High Performance Concretes An Annotated Bibliography 1974-1989

SHRP-C/WP-90-001

High Performance Concretes An Annotated Bibliography

1974-1989

Michael L. Leming, Shuaib H. Ahmad, Paul Zia North Carolina State University

John J. Schemmel, Robert P. Elliott University of Arkansas

Antoine E. Naaman University of Michigan

- Strategic Highway Research Program

National Research Council Washington, D.C. 1990

SHRY High Performance Concrete c An Annot at ed Bi b h g r ap h y 002

SHRP-C/WP-90-00 1

High Performance Concretes An Annotated Bibliography

1974-1989

Michael L. Leming, Shuaib H. Ahrnad, Paul Zia North Carolina State University

John J. Schemmel, Robert P. Elliott University of Arkansas

Antoine E. Naaman University of Michigan

- Strategic Highway Research Program

National Research Council Washington, D.C. 1990

SHRP-C/WP-90-00 1 SHRP-88-C205

March 15, 1990

Bibliography, Creep, Durability, Early Strength, Fiber Reinforced Concrete, Fatigue, High Performance Concrete, High Strength, Mechanical Behavior, Mechanical Properties, Shrinkage

Strategic Highway Research Program 818 Connecticut Ave., NW Suite 400 Washington, DC 20006

(202) 334-3774

FOREWORD

Strategic Highway Research Program (SHRP) Contract C-205 is concerned with an investigation of the mechanical behavior of high-performance concretes. The project is conducted by a research team from a consortium of three universities: North Carolina State University, the University of Arkansas, and the University of Michigan.

For the purpose of this project, high-performance concrete is defined as follows:

1. It should meet one of the following criteria:

a. A 3-hour strength not less than 3,000 psi b. A 24-hour strength not less than 5,000 psi c. A 28-day strength not less than 10,000 psi d. A water-cement ratio (including pozzolans) less than 0.35

2. It should also have a durability factor not less than 80 after 300 cycles of freezing and thawing.

The fiist task of the project was to conduct an extensive literature search to identify gaps in the existing knowledge on the subject. Based upon the literature search, this annotated bibliography was compiled as a working document covering a period of 15 years beginning in 1974.

This bibliography is divided into two sections: (I) plain concrete and @) fiber reinforced concrete. An author index and a subject index can be found at the end of each section. Section I was compiled at North Carolina State University with supplemental entries on pavement compiled at the University of Arkansas. Section 11 was compiled at the University of Michigan. All entries in the bibliography have been stored on PC disks and can be searched by keywords with the software PROCITE.

The development of a bibliography of this size requires an enormous amount of computer data processing. For their meticulous and extraordinary efforts in managing the database, special thanks are due William Chi of NCSU, Brett Peters of Arkansas, and Fadi Alkhairi of Michigan. Data entry by Andrea Hardison and assistance in literature search by Wayne Ellenberger, both of NCSU, are also gratefully acknowledged. Finally, Frank Pozo of NCSU Libraries was especially helpful in performing the online searches of TRIS and the Engineering Index files. His assistance is sincerely appreciated.

Comments and inquiries regarding this publication should be directed to:

h a m Jawed Manager, Concrete Program Strategic Highway Research Program 818 Connecticut Ave., N W Suite 400 Washington, DC 20006 (202) 334-3774

Section I

High Performance Plain Concrete

1974

1001. Bazant, 2. P. and Wu, S. T., "RATE-TYPE CREEP LAW OF AGING CONCRETE BASED ON MAXWELL CHAIN," Materiaux et Constructions, Materials and Structures, Vol. 7, No. 37, 1974, pp. 45-60.

It is shown that the linear creep law of concrete can be characterized, with any desired accuracy, by a rate-type creep law that can be interpreted by a Maxwell chain model of time-variable viscosities and spring moduli. Identification of these parameters from the test data is accomplished by expanding into Dirichlet series the relaxation curves, which in turn are computed from the measured creep curves.

1002. Bazant, 2. P. and Wu, S. T., "CREEP AND SHRINKAGE LAW . FOR CONCRETE AT VARIABLE HUMIDITY," American Society

of Civil Engineers, Journal of the Engineering Mechanics Division, Vol. 100, No. 6, 1974, pp. 1183- 1209.

The drying creep effect is modeled by a nonlinear coupling between two types of hidden stresses, those in solids and those in (hindered adsorbed) water. Material parameters, as functions of pore humidity, of equivalent hydration period, and of relaxation time, are identified from the existing test data, using an optimization algorithm based on a least-square criterion and coupled with a finite element program for strain and stress history in a drying concrete cylinder. The ratios in which pore humidity modifies the creep parameters are found to be nearly the same for all concretes. Realistic estimates of stresses induced by shrinkage and by drying creep are also reached. The formulation is also extended to variable temperature. The success in fitting the data corroborates the underlying irreversible therodynamic theory of the creep mechanism, and especially confirms that creep at working stress levels is caused primarily by the diffusion of solids which, in turn, is facilitated by the presence of water and is nonlinearly accelerated by its migration.

1003. Dhir, R. and Sangha, C. et al., "AGE, ENVIRONMENT AND FRACTURED CONCRETE, 'I Civil Engineering, N817, Sep 1974, pp. 44-51.

This article is concerned with the behaviour of fractured concrete. After a brief outline of earlier investigations, the authors give details of a series

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I..

of experiments t h a t t hey have c a r r i e d ou t t o s tudy the effect of age and environment on t h e h e a l i n g of f r a c t u r e d c o n c r e t e . Thei r r e s u l t s show t h a t water- cu red c o n c r e t e h e a l s better t h a n a i r - c u r e d c o n c r e t e and t h a t t h e best a b i l i t y t o heal. occurs when s t r e s s i n g takes p l a c e a t 1 4 days (when it was found t o be s t r o n g e r a t 28 days than when u n s t r e s s e d ) . They a l s o found t h a t t h e s t r e n g t h of c o n c r e t e d iminished when exposed t o a d r y atmosphere and subsequent ly f r a c t u r e d a t ages of 60 days o r more. Other f i n d i n g s were:- t h a t w h i l s t environment arid age affected b o t h pre-and p o s t - f a i l u r e s t r e s s - s t r a i n c h a r a c t e r i s t i c s , p o s t - f a i l u r e w a s affected t o t h e greater e x t e n t ; t h a t p r e - f a i l u r e s u s t a i n e d loads had l i t t l e effect on p o s t - f a i l u r e behaviour whereas p o s t - f a i l u r e s u s t a i n e d l o a d s r e s u l t e d i n a r educ t ion i n s t r e n g t h ; t h a t p o s t - f a i l u r e c y c l i c l oad ing i n c r e a s e d r e s i d u a l s t r e n g t h and t h a t t h e effect of s u s t a i n e d load ing on c o n c r e t e p r e v i o u s l y loaded t o maximum stress w a s t o :increase s t r e n g t h t o v a l u e s greater t h a n t h e cor responding s t r e n g t h of t h e c o n c r e t e no t p r e v i o u s l y s u b j e c t e d t o load ing .

1 0 0 4 . D h i r , R. and Sangha, C . e t a l . , "RELATIONSHIPS BETWEEN STRENGTH, CONCRETES, '' Quarry Management and Products , V o l . 1, NO. 3, Aug 1 9 7 4 , pp. 93-99.

DEFORMATION AND AGE OF AUTOGENOUSLY HEALED

T h e a u t h o r s describe an i n v e s t i g a t i o n on t h e autogenous h e a l i n g of mor ta rs s u b j e c t e d t o s t r e n g t h f a i l u r e . T h e e f fec ts of water/cement and aggregate/cement r a t i o s on t h e h e a l i n g p r o c e s s were s t u d i e d . S ix conc re t e s , made w i t h 3 t y p e s of c rushed igneous c o a r s e aggrega te , and cu red i n humid c o n d i t i o n s , formed t h e c y l i n d r i c , s l t es t specimens. 367 tes ts were conducted us ing a c o n s t a n t s t r a i n ra te of 1 X 1 / 1 O O O O O / s t o g i v e c o n t r o l l e d load ing up t o t he maximum stress of 5 0 n / squa re mm. T h e i n f l u e n c e of mix d e s i g n and age w a s cons ide red . T e s t ages w e r e 7 , 28, 60 , 1 2 0 and 2 4 0 d a y s . T h e a u t h o r s concluded t h a t (1) f u l l recovery of conc re t e s t r e n g t h a f t e r f r a c t u r i n g t o maximum stress i s p o s s i b l e f o r a l l ages i n v e s t i g a t e d and i s u n r e l a t e d t o aggrega te t y p e and mix p r o p o r t i o n s ; ( 2 ) f u l l recovery of t he 5 0 % t a n g e n t modulus was p o s s i b l e only a f t e r i n i t i a l t e s t i n g a t 7 days; (3 ) healed conc re t e e x h i b i t s b r i t t l e behaviour w i t h a reduced u l t i m a t e s t r a i n a t f a i l u r e .

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1 0 0 5 . Domone, P. L . , "UNIAXIAL TENSILE CREEP AND FAILURE O F CONCRETE," Magazine o f Concre t e Research , V o 1 . 2 6 , No.88, Sept 1974, pp. 1 4 4 - 1 5 2 .

T h i s paper describes a series o f e x p e r i m e n t s carried o u t on c o n c r e t e under u n i a x i a l t e n s i l e stress, u s i n g a t e s t method deve loped p r e v i o u s l y . The p r o p e r t i e s assessed i n c l u d e t h e e f fec t o f mix p r o p o r t i o n s and c u r i n g c o n d i t i o n s upon t h e s h o r t - t e r m f a i l u r e stress and s t r a i n and upon t h e t e n s i l e c r e e p unde r a l o a d of 35% o f t h e u l t i m a t e s h o r t - t e r m s t r e n g t h . The e f fec t o f variable humid i ty s ta tes upon t h e t e n s i l e creep was a l s o i n v e s t i g a t e d , and t h e r e s u l t s i n t e r p r e t e d from t h e v i ewpo in t o f creep h y p o t h e s e s f o r compress ive l o a d i n g .

1 0 0 6 . Gaynor, R . D., "ONE LOOK AT CONCRETE COMPRESSIVE STRENGTH," N a t i o n a l Ready Mixed C o n c r e t e A s s o c i a t i o n , P u b l i c a t i o n , No. 147, 1 9 7 4 , pp. 11.

The r e p o r t reviews t h e l i t e r a t u r e on some of t h e f a c t o r s which a f fec t t h e r e l a t i o n s h i p between t h e s t r e n g t h of s t a n d a r d molded c y l i n d e r s and d r i l l e d c o r e s and emphas izes t h e f a c t t h a t t h e r e l a t i o n s h i p s are n o t s u f f i c i e n t l y w e l l known t o predict c o r e s t r e n g t h levels t h a t w i l l be achieved, o r on t h e o t h e r hand, t o a v o i d c o r e s t r e n g t h s less t h a n 85 p e r c e n t f ' ( * c ) .

1 0 0 7 . Goodman, M. and Jo rgensen , G . e t a l . , "COMPUTER-AIDED INTERPRETATION O F STRESS-STRAIN CURVES," J o u r n a l of T e s t i n g and E v a l u a t i o n , V o l . 2 , No. 5 , S e p t 1 9 7 4 , p p . 361-369 .

A computer scheme f o r i n t e r p r e t i n g s t r e s s - s t r a i n c u r v e s has been deve loped u s i n g two basic a l g o r i t h m s . The f i r s t l o c a t e s t h e i n i t i a l l i n e a r p o r t i o n of t h e c u r v e by comparing t h e f i t o f l i n e a r and q u a d r a t i c c u r v e s t o t he da ta . The second d e t e r m i n e s t h e i n t e r s e c t i o n of t h e o f f s e t l i n e w i t h t h e d a t a . The scheme w a s tested by comparing computer r e s u l t s w i t h manual r e s u l t s o b t a i n e d b y s k i l l e d o b s e r v e r s . R e s u l t s w e r e good: t e n s i l e s t r e n g t h and 0 . 2 p e r c e n t o f f s e t y i e l d s t r e n g t h showed small d i f f e r e n c e s , less t h a n 2 p e r c e n t . Fo r t h e modulus and y i e l d s t r e n g t h a t 0 . 0 1 p e r c e n t o f f s e t , t h e d i f f e r e n c e s between t h e v a r i o u s o b s e r v e r s were more s i g n i f i c a n t t h a n t h e d i f f e r e n c e s between t h e computer r e s u l t s and t h e o b s e r v e r s . Fo r 32 samples ( 9 5 spec imens) t h e computer r e s u l t s f o r t h e modulus were g e n e r a l l y w i t h i n p l u s o r minus 2 p e r c e n t o f t h e average of t h e r e s u l t s f rom f o u r o b s e r v e r s and

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w i t h i n p l u s o r minus 1 0 p e r c e n t fior the 0 . 0 1 p e r c e n t y i e l d s t r e n g t h . Based on these r e s u l t s , a s t a n d a r d computer program has been develo:?ed which g e n e r a t e s g raphica l summaries o f t h e mecha*i ical p r c p e r t i e s In a form s u i t a b l e f o r permanent r e c o r d s .

1 0 0 8 . Hobbs, D . W . , "INFLUENCE OF AGGR.?GATE, RESTRAINT OK TI%: SHRINKAGE O F CONCRETE, J o u r n a l :)f T h e Arr.erican C o n c r e t e I n s t i t u t e , Vol . 71 , N o . 9 , Sep 1 9 7 4 , p p . 445- 4 5 0 .

A comparison i s made of t h e vsri0L.s mcdels which have been p roposed t o p r e d i c t t h 2 dependence of c o n c r e t e s h r i n k a g e upon t h e p r o p e r t i e s of i t s c o n s t i t u e n t s and t h e a g g r e g a t e v3lume c o r . c e n t r a t i o n . T h e p r e d i c t i o n s of one of these n o d e l s , t h e Cement and C o n c r e t e A s s o c i a t i o n model, are compered i n a g e n e r a l way w i t h t he obse rved sh r inkage b e h a v i o r o f c o n c r e t e . I t i s shown t h a t t h e sh r inkage ctf normal a g g r e g a t e c o n c r e t e s i s dependent pr i rnar i . ly on crnly three parameters -- t h e paste s h r i n k a c e , the a g g r e g a t e s h r i n k a g e and t h e aggregate v o l c n e c o n c e r , t r a t i o n .

1 0 0 9 . J e n k i n s , J. and B e e c r o f t , G . e t a l . , "POLYMER CONCRETE: OVERLAY TEST PROGRAM, Oregon Department of T r a n s p o r t a t i o n , I n t e r i m Report., CJov 1 .974 , p p . 53 .

T h i s r e p o r t describes work done on v a r i o u s combinations of monomers ar.d polymer concrete nixes and i d e n t i f i e s t h e mixes showi.ncj t h e grea tes t p o t e n t i a l f o r u s e i n bridge deck o v e r l a y s . P r e s e n t e d a re t e s t r e s u l t s showing p h y s i c a l p r o p e r t i e s o f v a r i o u s polymer c o n c r e t e mixes, such as compress ive s t r e n g t h , s p l i t t e n s i l e s t r e n g t h , moclu1.us~ of e l a s t i c i t y , thermal c o e f f i c i e n t of expans ion , and s h r i n k a g e c o e f f i c i e n t . The e f fec ts of polymer c o n t e n t , work t i m e , and t e m p e r a t u r e on v a r i o u s p r c r p e r t i e s a r e a l s o d i s c u s s e d . The development of two pcrlymer c o n c r e t e sys t ems w i t h e x c e l l e n t membrane p o t e n t i a l . a :x described a l o n g w i t h t h e de ta i l s , of bonding charac te r i s t ics of several s y s t e m s . E'inal l y , a polymer c o n c r e t e mix w i t h s u i t a b l e p r o p e r t i e s f o r deck and pavement p a t c h i n g i s de ta i led .

1 0 1 0 . J o h n s t o n , C . , "WASTE GLASS AS COURSE AC;GF,EGATE FOR CONCRETE, I' J o u r n a l of T e s t i n g and Eva lua t . i on , Vol. 2: No. 5, Sep 1 9 7 4 , pp . 344-350.

T h e p a p e r r e p o r t s on t h e per formance of 3 4 d i f f e r e n t c o n c r e t e mixeg c o n t a i r i i n g g lass c r u s h e d t o 3 / 4 - i n . ( 1 9 - m m ) maximum s i z e as c o a r s e a g g r e g a t e and

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six reference mixes made with gravel of the same size. Two cements of alkali equivalent 0.58 and 1.13, classifiable as low and high alkali (ASTM C 150-72), in amounts ranging from 400-900 lb/cu yd (237-534 kg/cu m) were used in combination with glass both with the fines removed and in the as-crushed condition. Partial cement replacement with fly ash and mixing of glass with gravel aggregate were included in an attempt to find a suitable method of overcombing the expected adverse effects of the reaction between glass and cement alkalis. On the basis of compressive stren,gth, flexural strength, expansion, and visible surface deterioration recorded up to an age of one year, the results show that in many cases the direct combi.nation of glass with portland cement yields concrete which exhibits marked strength regression and excessive expansion due to alkali-aggregate reaction. The conditions under which performance is satisfactory appear to relate to limiting maximum values of cement content and alkali equivalent. Replacement of 25 to 30 percent by weight of the cement, whether low or high alkali, appears to be an effective and widely applicable method of ensuring good long-term concrete performance, although the minimum required in any given case may be related to cement composition.

1011. Morgan, D. R., "EFFECTS OF CHEMICAL ADMIXTURES ON CREEP IN CONCRETE," Institution of Engineers, Australia, Civil Engineering Transactions, Vol. 16, NO. 1, 1974, pp. 7-11.

This paper critically reviews the results of a number of investigations into the effects of chemical admixtures on creep in concrete. It is shown that under certain conditions of admixture use and environmental exposure, chemical admixtures can give rise , t o highly significant increases in creep. A number of practical recommendations are made for the use of admixtures in creep-sensitive situations.

1012. Orchard, D. and Jones, R. et al., "EFFECT OF CEMENT PROPERTIES AND THE THERMAL COMPATIBILITY OF AGGREGATES ON THE STRENGTH OF ACCELERATED CURED CONCRETE," Journal Testing & Evaluation, Vol. 2, No. 2, Feb 1974, pp. 95-101.

In the present research electric curing was adopted, completely eliminating any temperature gradients throughout the test specimens. It was found t h a t coarse aggregates having a low coefficient of thermal expansion caused a significant drop in the one-day accelerated cured compressive strength. The

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c o e f f i c i e n t o f thermal expans ion o f t h e c o a r s e aggregate d id n o t have muck e f f e c t on t h e 28-day accelerated c u r e d s t r e n g t h . I t was t h o u g h t t h a t t h i s w a s due t o au togenous hea l . i ng du::ing t h e 27 d a y s of normal c u r i n g , r e c t i f y i n g any cr izcking c a u s e d t h r o u g h stresses a r i s i n g from thermal i n c o m p a t i b i l i t i e s during. t h e one day o f accelerated curinc?. R e s i d u a l e x p a n s i o r a f t e r h e a t i n g and c o o l i n g of ce r l - a in a g g r e g a t e s was l i a b l e t o c a u s e decreases i n s t r e n g t h . F u r t h e r e v i d e n c e i s g i v e n o f t h e impor t ance o f t h e C ( s u b 3 ) a c o n t e n t o f cement i n d e t e r m i n i n g t h e u l t i m a t e s t r e n g t h o b t a i n e d when t h e c o n c r e t e i s s u b j e c t e d i n i t i a l l y t o accelerated c u r i n g .

1 0 1 3 . Ra i thby , K . D . , "SOME FLEXYRAL F A T I G U E PROPERTIES O F CONCRETE-EFFECTS OF AGE AND METHODS OF C U R I N G , " A U S t Conf on Eng Mater, l s t , P roc , Sydney, A u s t r a l i a , Aug 1 9 7 4 , p p . 211-229.

T h e i n v e s t i g t i o n w a s conduc ted on t y p i c a l pavement q u a l i t y c o n c r e t e from tes t s on ma11 beams which had f i r s t aged f o r 6 months unde r v a r i o u s c o n b i n a t i o n s of a i r c u r i n g and immersion i n w a t e r . T h e h ighes t f l e x u r a l s t r e n g t h s and l o n g e s t f a t i g u e l ives w e r e achieved on beams which w e r e oven-driec! a f t e r p r o l o n g e d immersion. The l o w e s t s t r e n g t h s , a b o u t one ha l f o f t h e h ighes t v a l u e s , o c c u r r e d or. s i m i l a r beams which were a l l o w e d t o d r y o u t i n t h e l a b c , r a t o r y a f t e r immersion. I n g e n e r a l , f l e x u r a l f a t i q u e s t r e n g t h f o r d i f f e r e n t t y p e s of concre te unde r var ious c o n d i t i o n s of c u r i n g and o v e r a w i d e r a n g e Df a c e s a?pea r s t o be re la ted d i r e c t l y t o t h e modulus D f r l ; .p ture measured i n q u a s i - s t a t i c tes ts under t h e sarr.2 c o r . d i t i o n s .

1 0 1 4 . R u s s e l l , R . O . , "NEW H I G H EARLY STRENGTH CONCRETE," Roadways and A i r p o r t s , A C I SP-51, 1 9 7 4 , pp . 269-278.

The p a p e r r e p o r t s on a development t h z t grew o u t of r e f r a c t o r y bonding programs o r i e n t e d towcrd c h e m i c a l l y bonded r e f r a c t o r i e s . The bonding concep t of t h i s n o v e l c o n c r e t e is based on an acid-base r e z c t i c i n . The r a t e o f r e a c t i o n i s c o n t r o l l e d b y t h e p r o p e r s e l e c t i o n o f magnesia and o f a complex phospha te l i q u i d . T h e b a l a n c e o r major p o r t i o n of t h e c o n c r e t e i s composed n a t u r a l aggregates. With p r o p e r mixing, s e t t i n g t i m e s are on t h e o r d e r o f s even minu tes a t room t e m p e r a t u r e . The c r u s h i n g s t r e n g t h s s h o u l d exceed 200C p s i f o r f i n e aggregates a f te r two h o u r s and can e x c e e d 3500 p s i by i n c r e a s i n g aggregate s i z e . T e s t i n g ha.s sk.own good freeze-thaw and s u c c e s s f u l au t .oc lave t e s t i n g . Not shown by t r a d i t i o n a l t e s t i n g i s t h e e . b i l i t y of t h i s c o n c r e t e t o bond t o many a r t i c l e s such as- i t s e l f , o l d

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concrete, steel, wood, and paper. Another benefit is the cold weather working capabilities. Preliminary experience in applying this concrete has been in a bridge deck on an interstate highway in cooperation with the District 12, State of Ohio, bridge engineers.

1015. Taylor, M. A. and Patel, B. K., "INFLUENCE OF PATH DEPENDENCY AND MOISTURE CONDITIONS ON THE BIAXIAL COMPRESSION ENVELOPE FOR NORMAL WEIGHT CONCRETE," Journal of The American Concrete Institute, Vol. 71, NO. 12, 1974, pp. 627-633.

Using 50 mm cubical specimens, biaxial compression- compression strength envelopes were obtained for three strengths of 9. 5 mm MSA normal weight aggregate concrete. The desired stress state and partial elimination of friction were achieved by loading the specimens through 1. 6 mm diam ball bearings and using a specially designed two-channel, closed-loop electro- hydraulic testing facility. Envelopes were obtained for specimens dried after a standard curing period and for specimens kept continually saturated. Further studies examined the envelopes obtained under different loading histories.

1016. Young, J. F., "ASSESSMENT OF THE INFLUENCE OF MICROSTRUCTURE ON TIME-DEPENDENT DEFORMATIONS OF HARDENED CEMENT PASTE," Proceedings/Aust Conf on Eng Mater, lst, 1974, pp. 3-28.

Experimental data on drying shrinkage and creep of portland cement concrete has shown that these time- dependent deformations are properties of the cement paste. It is to be anticipated that the physical structure of the hardened paste will influence such properties. The paper reviews the pertinent results in each area of research and some of the conclusions reached are that drying shrinkage and creep are manifestations of the same phenomena; and that the C- S-H gel (colloidal calcium silicate hydrate phase of variable composition) is primarily responsible for time-dependent deformations observed due to its randomly arranged layer structure.

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1975

1 0 1 7 . "FAST SETTING CONCRETE, I' ' Spec.ia1. R e p o r t s on: 'Jse o f Equipment and Methods of Maint.ensnce' . (Research. comple ted by Manning, Selvage & Lee, I n c . f o r Repub.1:~~: Steel C o r p o r a t i o n ) , J u l 19?5, pp,. S .

S t e e l c o t e Fast-Crete i s a slixtiure o f f i n e c a l c i n e d magnes ia and aggregate combined w i t h ammonia phosphorous l i q u i d t o produce h i g h ezr1.y s t r e n g t h c o n c r e t e . Accord ing t o t h e company, t.he c o n c r e t e s e t s i n f i ve t o t e n minu tes and hardens i n t.wa h o u r s ; t h e p r o d u c t ' s immediate a p p l i c a t i o n i s hi.ghw&y and b r i d g e deck repairs where vehic le t r a f f i c can be r e s t o r e d w i t h i n h o u r s . The new p r o d u c t bonds t.o s t . r u c t u r a 1 s teel , o l d c o n c r e t e , wood, g l a s s , , and paper. Field tes ts have d e m o n s t r a t e d t h a t t h e p r o d u c t ' s a b i l i t y t o bond o l d c o n c r e t e makes it p o s s i . b l e t.o f u r t h e r speed repairs by e l i m i n a t i n g a t ime-consumi .n~~ sawing step now r e q u i r e d t o create a n i n t e r l . o c k i n g edge a round thi? p o t h o l e s t o s e c u r e t h e p a t c h . T h e app1.ic:ation p r o c e d u r e and o t h e r t e c h n i c a l d a t a are p r o v i d e d .

1 0 1 8 . Aronsson, R . and Fage r lund , G . e t a l . , "THE IMPACT STRENGTH OF CONCRETE USED I N E'ILES," Cement and C o n c r e t e Research I n s t i t u t e , StockhoI.m, Sweden, 1975, p p . 7 1 .

T h e main p u r p o s e of t h i s r e s e a r c h s t u d y i s t o develop reliable m e t h o d s and e q u i p m e r i t f c i r the t e s t i : T < T

of s t r e n g t h p r o p e r t i e s o f c o n c r e t e sub:jec:ted t o impact l o a d i n g s i m i l a r t o t h a t which o c c u r s w i t h p i l e d r i v i n g . Four d i f f e r e n t corLcrete qua1. i t - ies a r e tested a c c o r d i n g t o t h i s method ar:d t h e resu1t . s are compared w i t h e x p e r i e n c e s g a i n e d w i t h ac t .ua1 p i l e d r i v i n g . A l i t e r a t u r e s u r v e y has a l s o b e e n made and a n a l y s e d . 1':. w i l l be p u b l i s h e d as a sepa ra t - e r e p o r t arid i s t h e r e f o r e n o t i n c l u d e d . A prograrnae !:or f u r t h e r development i s a l s o i n d i c a t e d r e s u l t i - n g i.n a method f u l l y a p p l i c a b l e f o r a c o n c r e t e element: works. T h e mechan ica l equipment d i s c u s s e d was a 1 6 metre t a l l . m o d i f i e d v e r s i o n of Hopkinson 's s p l i t bar , and strai:': gauges , Wheats tone br idges w i t h ampli.fi.ers, t r ans l e r ; : : r e c o r d e r s , o s c i 11 o s c ope s and re c o r de 1: s a I. s o as s o c i a I: e : 2 w i t h t h e t e s t i n g equipment . An i n c r e a s e d a g g r e g a t e c o n t e n t improves the impact s t r e n g t h of c o n c r e t e i f compress ive s t r e n g t h i s m a i n t a i n e d a t a c o n s t a n t l eve l .

8 A

1019. Bickle, L. and Smiel, A., "APPLICABILITY OF ACOUSTIC- EMISSION TECHNIQUES TO CIVIL ENGINEERING RESEARCH," Final Rpt., Eric H Wang Civil Engineering Research Facility, New Mexico University, Albuquerque, Jun 1975, pp. 102.

When a solid undergoes a plastic deformation or fracture, part of the stored strain energy is released as elastic stress waves which can be sensed by sophisticated instrumentation. These stress waves are termed acoustic emissions even though the amplitudes and frequencies involved are usually outside the audible range. This study demonstrated that acoustic emission technology is becoming increasingly more suitable for field applications in civil engineering. Further research relating to reinforced concrete, soils, paving materials, and passive transducers is clearly justified.

1020. Brown, J. and Pomeroy, C., "MECHANICAL PROPERTIES OF SOME YICRO-CONCRETES AND MORTARS MODIFIED BY POLYMETHYLMETHACRYLATE," Cement and Concrete Association, Tech Rpt., Mar 1975, pp. 1-24.

Measurements were made of the mechanical properties of mizroconcretes and mortars modified by the inclusion of polymethylmethacrylate. Several different experimental methods were employed: (1) the PCC method whereby concretes were prepared by using pre-mixed polymer-emulsion admixture, followed by a cycle of heat curing; (2) the PIC method in which hardened concrete was impregnated with the monomer which was subsequently polymerized in situ; (3) the PCC method with the addition of steel fibers; and (4) PIC treatment of PCC prepared concrete. Results showed improved compressive strengths and an increase in the elastic modulus with an increase in the amount of polymer in the concrete. These results were attributed to a reduction in capillary propsity. flexural strength of the polymer-modified concrete seemed to be higher than would result from a simple reduction in porosity. the concretes prepared by using the PCC method. BIC method provided higher compressive strengths than the PCC method, since the impregnation sequence reduced the effective porosity to a greater extent. The inclusion of steel fibers made the polymer- modified concrete less brittle, but the fiber concentrations used (up to 1.5 percent by volume) has a very small effect upon the stress at which the matrix cracked. Applying the PIC method to PCC- modified concretes was not a success, possibly due to limited penetration of the monomer into the PCC-

The

This was particularly so for The

9

t reated c o n c r e t e . The polymer treatmer-.ts s u b s t a n t i a l l y improved the r e s i s t a n c e of c o n c r e t e t o c h l o r i d e and s u l p h a t e a t t a c k and alscl p r o v i d e d grea te r r e s i s t a n c e t o damage from f r e e z i n g an.d thawing . The most p r o m i s i n g u s e o f polymer-mc,:iified c o n c r e t e s i s i n a p p l i c a t i o n s where these a d v a n t a g e s can h e e x p l o i t e d ,

1 0 2 1 . Campbel l -Allen, D . and Rogers , D. F . , “SBRINKAGE O F CONCRETE AS AFFECTED BY S I Z E , “ Ma te r i aux e t C o n s t r u c t i o n s , Materials and S t r u c t u r e s , V o l . 8 , No. 4 5 , 1 9 7 5 , p p . 193-202.

A c r i t i c a l s t u d y o f e x i s t i n g test. dat.a on d r y i n g s h r i n k a g e of c o n c r e t e s u g g e s t s t h a t t h e q e n e r a l l y accepted v i e w t h a t t h e u l t i m a t e s h r i n k a g e i s a f u n c t i o n o f s i z e canno t be s t r o n g l y s u p p o r t e d . I t i s shown t h a t t he v a l u e s of u l t i m a t e s h r i n k a g e f o r l a r g e spec imens o b t a i n e d by e x t r a p o l a t i o n o f e m p i r i c a l s h r i n k a g e - t i m e c u r v e s can be ser-ious1.y i n e r r o r i f the wrong form o f c u r v e i s f i t t e d . A n a n a l y t i - c a l s t u d y of a n idealised model i n d i c a t e s t h a t t h e o n l y f a c t o r which c o u l d p roduce a major size e f fec t is t h e o n s e t o f c r a c k i n g . I t i s s u g g e s t e d t h a t f o r d e s i g n purp0se . s t h e s i z e effect on the f i n a l s h r i n k a q e s h o u l d be e l i m i n a t e d from c o d e s .

1022. Clear, K. and Ornsby, W . , “CONCEPT O F INTERNALLY SEALED CONCRETE, I n t r m Rpt . , Federa:- Highway A d m i n i s t r a t i o n ; Off ice of Resea rch and Development, Mar 1 9 7 5 , 1 7 pp.

c o n c r e t e , which p r e v e n t s t h e i n t r u s i o n of c h l o r i d e s f rom d e c i c i n g o p e r a t i o n s c r mar ine env i ronmen t s and t h e subsequen t d e t e r i o r a t i o n of -,he c:oncrete, w a s deve loped by Monsanto Research C o r p o r a t i o n unde r an FHWA c o n t r a c t . The work i s d e s c r i b e d i n Repor t FHWA- RD-75-20, ’ I n t e r n a l l y Sealed C o r c r e t e , ‘ hy G . H . J e n k i n s and J . M . B u t l e r . T h i s report: :is i n t e n d e d as a supplement t o t h e above p u b l i c a t i o n . pe r fo rmed t o f u r t h e r document t h e concept: o f i n t e r n a l l y sealed c o n c r e t e and t o p r o v i d e independer* t e v i d e n c e t h a t t he wax p a r t i c l e s w h i c h are mixed i n t o t h e fresh c o n c r e t e do, upox h e a t i n g , migrate i n t o t h e cap i l l a r i e s and v o i d s of the c o r c r e t e m a t r i x . T h e s c a n n i n g e l e c t r o n microscope and an e n e r g y d i s p e r s i v e x- ray a t t a c h m e n t were used t o s t u d y heated and u n h e a t e d c o n c r e t e c o n t a i n i n g 2 Fercerit montan wax. T h e c o n c l u s i o n w a s t h a t montan wax, when melted, w i l l migrate w i t h i n , and t h o r o u g h l y c: 3at, t h e s u r r o u n d i n g c o n c r e t e m a t r i x .

A p r o m i s i n g new p r o c e s s f o r interna:Lly s e a l i n g

The work was

1 0

1023. Eash, R. and Shafer, H., "REACTIONS OF POLYMER LATEXES WITH PORTLAND CEMENT CONCRETE," Transportation Research Record, N542, 1975, pp. 1-8.

This paper explains the physical and chemical actions and reactions of polyvinylidene chloride and styrene-butadiene polymer latexes on the aggregate and portland cement in concrete. It also describes how the polymer particles irreversibly bond to the aggregate and cement, form a monolayer of plastic parti,zles over their surfaces, and subsequently coalesce to form a continuous polymer phase throughout the concrete. The need for curing procedures with latex concrete different from those required for the optimlim cure of conventional concrete is also discussed. These basic data are expanded to explain how polymer latexes reinforce concrete, improve its structural properties, control its elastic behavior, and greatly enhance its durability. Data are presented to describe polymer latex concrete with compressive strengths from 5,000 to 15,000 psi (34 500 to 103 000 kPa), flexural strengths from 800 to 2,000 psi (.5520 to 13 800 kPa), elastic moduli from 2 to 5 x 10 to the 6th power kPa), bond strength to steel greater than 2,500 psi (17 200 kPa), and bond strength to concrete greater than 600 psi (4140 kPa) at which the concrete substrate fails. Practical applications of latex concrete over the past 20 years are described, and why the materials are ideally suited for each application is explained.

1024. Gerwick, B., "MATERIALS FOR CONCRETE SHIPS: DURABILITY AND CORROSION PROTECTION, COATINGS, INSPECTION AND REPAIR," Proceedings of the Conference on Concrete Ships and Floating Structures, University of California, Berkeley, Sept 15-19 1975, pp. 8.

Properties of concretes, passive reinforcements, prestressings, and composite systems are listed, and inspection and repair procedures are proposed.

1025. Gjorv, O., "CONCRETE IN THE OCEANS," Marine Science Communications, Vol. 1, No. 1, 1975, pp. 51-74.

increasing number of very important ocean structures and vessels. The assurance of high performance and long term durability requires a good and basic understanding of the various deteriorating processes which may occur. Some experiences are briefly presented on the use of reinforced concrete as a construction material in marine environments. chemical deterioration of concrete in seawater should not represent any problem provided high quality concrete

Reinforced concrete is being applied to an

11

i s a p p l i e d . F r e e z i n g and thawing car. a l s o be c o n t r o l l e d by a p p r o p r i a t e u s e of a i r - e n t r a i n i n g a d m i x t u r e s . I t i s p r i m a r i l y c o r r o s i o n of embedded s tee l which may a f fec t t h e perfc1rmanc:e. Al though e x p e r i e n c e i n d i c a t e t h a t concr-et €2 sea s t r u c t u r e s can remain serviceable w i t h little 01: no ma in tenance f o r a t l e a s t 4 0 t o 50 y e a r s , a l l s t r u c t u r e s f o r which s a f e t y and per formance p l a y an i m p o r t a n t r o l e s h o u l d be p e r i o d i c a l l y mon i to red f o r s teel p o t e n t i a l s and e l ec t r i ca l r e s i s t i v i t y alor ,g t h e c o n c r e t e s u r f a c e . Such measurements s h o u l d be p a r t of t-he r e g u l a r s u r v e y i n g and main tenance program.

1 0 2 6 . Hawkins, N . , "FATIGUE C O N S I D E R A T I O N S FOR CONCRETE SHIPS AND OFFSHORE STRUCTURES, P r o c e e d i n g s o f t h e Confe rence on Concre t e Ships ancl F l o a t i n g S t r u c t u r e s , U n i v e r s i t y o f C a l i f o r n i a , Be rke ley , S e p t 15-19 , 1975, p p . 2 2 .

S t r e n g t h t o resist higk---inl;er:sity r e v e r s e d - c y c l i c bend ing and shear, r i g i d i t y t o res is t v i k r a t i o n s , w a t e r - t i g h t n e s s , impact r e s i s t a r z e , and l o n g l i f e i n a n adverse envi ronment of c o n c r e t e and s teel are compared. D u c t i l i t y of f a t i g u e f a i l u r e s and b r i t t l e f r a c t u r e and c r a c k i n g are a n a l y z e d . F a t i g u e l i f e i s c a l c u l a t e d u s i n g t h e known damaqe cha rac t e r i s t i c s f o r t h e material and s e l e c t i n g t h e a p p r o p r i a t e t h e o r y f o r c u m u l a t i v e damage e f fec ts and p r o p e r r e c o g n i t i o n of a l l t h e f a c t o r s , ma te r i a l , c o n s t r u c t i o n a l and e n v i r o n m e n t a l , l i k e l y t o a f f ec t t h e s t r e s s - l i f e relationship.

1 0 2 7 . Hudson, S . and Bowery, F . , "D3TE~RMINATION O F STATISTICAL PARAMETERS. PHASE 11. COIVCRE'I'E PAVEMENT AND STRUCTURES, I' Materials R e s e x c h and Development, R e s . Rp t . , J u l 1975, pp . 1.35.

The r e p o r t c o v e r s t h e j.nvest.i g a t i o n s , f i n d i n g s and c o n c l u s i o n s of a research p r o j e c t co3duc:ed t o o b t a i n r e l i a b l e i n f o r m a t i o n r e q u i r e d f o r t h e p r e p a r a t i o n of r e a l i s t i c s p e c i f i c a t i o n s f o r P o r t l a n d cement concrete f o r t h e P e n n s y l v a n i a Depar tmen t of T r a n s p o r t a t i o n . The research w a s conduc ted o v e r a p e r i o d from Oc tobe r 1 9 7 3 t o A p r i l 1975. The work i n v o l v e d (1) t h e d r a f t i n g of t r i a l s p e c i f i c a t i o n s ( 2 ) t h e random sampl ing and t e s t i n g of pavement and s t r u c t u r e c o n c r e r e on a statewide bas is , and ( 3 ) t h e r e v i s i o n of t h e t r i a l s p e c i f i c a t i o n s as r e q u i r e d by the f i n d i n g s of t h e random sampl ing . Concre t e sampl ings 'dere made on 35 p r o j e c t s d i s t r i b u t e d o v e r e i g h t c o u n t i e s . Random sampl ings i n c l u d e d 165 of s t ruc: .ure c o n c r e t e and 2 9 7 of pavement c o n c r e t e . T o f a c i l i t a t e a n a l y s i s , t h e s t a t i s t i c a l p a r a m e t e r s o f measurements m3de on a l l samples were o b t a i n e d frorn t h e d a t a by mzaris of

I

I

computer programs specifically developed for the purpose. Field measurements of slump and air content were made on all samples. Tests of compressive and flexural strength were made. Data from all tests were analyzed to determine averages, standard deviation among projects, standard deviation within projects, overall standard deviation, and coefficient of variation. See also report dated October, 1972.

1028. Johnston, C., "FIFTY-YEAR DEVELOPMENTS IN HIGH STRENGTH CONCRETE," ASCE Journal of the Construction Division, Vol. 101, No. C04, Dec 1975, pp. 801-818.

full, users of concrete must become conversant with the many recent developments that have made it possible to build smaller lighter structures or structural components using high strength concrete. The paper emphasizes the importance of cement and aggregate characteristics on the strength of conventional Portland cement concrete, and then shows how high compressive strengths can be achieved using conventional materials and compaction techniques. It then shows how a change to high alumina cement can be advantagous in achieving very high early strength with otherwise conventional materials and techniques. Newer, sometimes fairly complex, and generally more expensive methods of achieving high strength involve high pressure compaction, polymer impregnation, and fiber reinforcement. In each case, the basic technology is described, the range of strengths attainable is defined, and actual and potential field applications are identified.

In order to utilize present day technology to the

1029. Johnston, C. D., "FIFTY-YEAR DEVELOPMENTS IN HIGH STRENGTH CONCRETE," American Society of Civil Engineers, Journal of the Construction Division, Vol. 101, NO. 4, 1975, pp. 801-818.

In order to utilize present day technology to the full, users of concrete must become conversant with the many recent developments that have made it possible to build smaller lighter structures or structural components using high strength concrete. The paper emphasizes the importance of cement and aggregate characteristics on the strength of conventional Portland cement concrete, and then shows how high compressive strengths can be achieved using conventional materials and compaction techniques. It then shows how a change to high alumina cement can be advantageous in achieving very high early strength with otherwise conventional materials and techniques. Newer, sometimes fairly complex, and generally more expensive methods of achieving high strength involve

13

h i g h p r e s s u r e compact ion, polymer i m p r e g n a t i o n , and f iber r e i n f o r c e m e n t . I n each case, t h . e b a s i c t e c h n o l o g y i s described, t h e r a n g e of s t r e n g t h s a t t a i n a b l e i s d e f i n e d , and actual. and. p o t e n t i a l field a p p l i c a t i o n s are i d e n t i f i e d .

1 0 3 0 . Mahmood, N . and Hannant, D . , "STRENGTH O F CONCRETE SUBJECTED TO COMPRESSION-COMPRESSION-, T E N S I O N STRESS SYSTEMS, '' ASTM J o u r n a l of T e s t i n 3 and E v a l u a t i o n , Vol. 3 N o . 2 , Mar 1975, pp . 107-112.

An e x p e r i m e n t a l i n v e s t i g a t i o r . i n t o t he f a i l u r e of a p a r t i c u l a r c o n c r e t e s u b j e c t e d t o stress f i e l d s v a r y i n g between b i a x i a l compress ion , compression-compression- t e n s i o n , and u n i a x i a l t e n s i o n i s desc:ribed. The r e s u l t s are compared w i t h p u b l i s h e d data f o r re la ted stress sys t ems , and t h e shape of t h e f a i l u r e s u r f a c e i n t h e compress ion- t e n s i o n q u a d r a n t s o f s tress s p a c e i s shown t o be o f t h e s i m p l e hexagonal pyramid t y p e .

1 0 3 1 . Ma lho t r a , V. M . , "DEVELOPMENT OF SULFUR-INFILTRATED HIGH-STRENGTH CONCRETE," J o u r n a l of The American C o n c r e t e I n s t i t u t e , Vol . 72 , N o . 9 , 1975, p p . 466-473.

A new t y p e of h i g h - s t r e n g t h , s u l f u r - i n f i l t r a t e d c o n c r e t e has been deve loped from l e a n , c o n v e n t i o n a l c o n c r e t e . The c o n c r e t e so deve loped e x h i b i t s phenomenal improvements i n i t s s t r e n q t h and e l a s t i c p r o p e r t i e s and i s h i g h l y r e s i s t a n t t o repeated c y c l e s of f r e e z i n g and thawing . T h i s new t y p e o f c o n c r e t e described appears t o be e m i n e n t l y s u i t e d f o r precast c o n c r e t e u n i t s , such as p i p e s , p o l e s , farm s i l o s , and r a i l w a y t i e s , and i s a prac t ica l . s u b s t i t u t e f o r e x p e n s i v e polymer- impregnated c0ncret.e.

1 0 3 2 . Ma lho t r a , V. M . , "IN-PLACE EVALUATION O F CONCRETE, '' Can Cent f o r Miner, Energy and Technol , Ottawa, Vol. 1 0 1 , No. 2 , Jun 1975, pp . 345-35-7.

T h e two new methods f o r e s t i m a t i n g t h e s t r e n g t h of c o n c r e t e i n s t r u c t u r e s a re : (1) T h e Windsor p r o b e tes t ; and ( 2 ) t h e p u l l - o u t t e s t . The Windsor p r o b e measures the p e n e t r a t i o n r e s i s t a n c e of c o n c r e t e . The Windsor p r o b e c o n s i s t s of a power- a c t u a t e d gun o r d r iver , hardened a l l o y p r o b e s , l o a d e d car t r idges, a depth gage f o r measu r ing p e n e t r a t i o n , and r e l a t e d equipment . The p r o b e i s 3. 2 5 i n . ( 6 . 3 mm) i n diameter, 3 . 12.5 i n . ( 7 9 . 4 mm) long, . and has a f r u s t o - c o n i c a l p o i n t . A pul-1-out t es t measures , w i t h a dynamometer, t h e f o r c e r e q u i r e d t o p u l l o u t from c o n c r e t e a specia1l.y shaped s t e e l r o d w i t h a n e n l a r g e d end t h a t has been cast i n t o tha-: c o n c r e t e . The p u l l - o u t f o r c e i s re la ted t.o compress ive s t r e n g t h , the r a t i o of t h e p u l l o u t - c o m p r e s s i o n

14

strength being between 0. 1 and 0. 2 . The two new pieces of equipment which are either simplified versions of equipment already available or are based upon well-established theoretical concepts are: (1) The PUNDIT; and ( 2 ) the Concrete Maturity Meter. The PUNDIT is a light-weight portable ultrasonic concrete-tester, whereas the Concrete Maturity Meter measures maturity of concrete by use of a probe.

1033 . Malhotra, V., "DEVELOPMENT OF SULFUR-INFILTRATED HIGH- STRENGTH CONCRETE," American Concrete Institute, Journal of, Vol. 72, No. 9, Sep 1975, pp. 466-473.

Sulfur-infiltrated, high-strength concrete has been developed at early ages from 2 day old conventional concrete containing low cement content. Two infiltration procedures have been employed. Procedure A consists of moist curing fresh concrete specimens for 24 hr. drying them at 250 F ( 1 2 1 C) for 24 hr, immersing them in a bath of molten sulfur for 3 hr, removing them from sulfur to cool, and then testing 1 to 2 hr later. Procedure B consists of moist curing fresh concrete specimens for 24 hr, drying them at 250 F ( 1 2 1 C) for 24 hr, immersing them in molten sulfur under vacuum for 2 hr, releasing the vacuum and soaking them for an additional 1 / 2 hr, then removing them from sulfur to cool. Testing is done 1 to 2 hr later. Satisfactory high-strength concretes have been produced using the above procedures, with superior results being obtained using Procedure B. The sulfur- infiltrated concretes exhibit phenomenal increases in mechanical and elastic properties and durability characteristics. A typical value of the compressive strength of the infiltrated specimens using Procedure B was 8060 psi (55.3 MN sq m) compared with 810 psi (5.6 MN sq m) for reference moist cured specimens. The sulfur-infiltrated specimens were in excellent condition after more than 800 cycles of freezing and thawing, whereas the moist cured specimens had completely disintegrated after 40 cycles. This new type of concrete appears to be eminently suited for precast concrete units, such as pipes, poles, farm silos, and railway ties, and is a practical substitute for expensive polymer-impregnated concrete.

YEARS OF PROGRESS," Proc Paper, ASCE Journal of the Construction Division, Vol. 101, No. CO1, Mar 1975, pp. 5-14.

1034. Mather, B., "DURABILITY OF CONCRETE CONSTRUCTION--50

After 50 years progress in understanding factors causing deterioration of concrete has been such that deterioration can be prevented provided that the cause can be anticipated and appropriate measures takes.

15

D i f f e r e n t p r e c a u c i o n s are 1:eedecl f o r d i f f e r e n t c a u s a t i v e f a c t o r s t h a t may be d e s t r u c t i v e a g e n c i e s . D e t e r i o r a t i o n from f r o s t a c t i o n (:hemi-cal r e a c t i o n s of a l k a l i e s and s o l u b l e s i l i c a i n the aggregates s u l f a t e a t t ack , d e l a y e d h y d r a t i o n o f free lime 01: magnes ia , 01: b o t h , i n t h e cement, expans ion of c e r t a i n k i n d s of! aggregate par t ic les caused b y chemical react i o n s o t h e r t h a n t h o s e w i t h a lka l i e s s u r f a c e c o n t - r a c t i o n due :lo d r y i n g and s o l u t i o n ( l e a c h i n g ) can be p r e v e n t e d b y o t h e r p r e c a u t i o n s .

1035. Pankra tov , V. and Osipov, A . e t al., "SLAG PORTLAND CEMENT FOR HYDRAULIC STRUCTURES OPERATINC; UNDER SEVE3IE CLIMATIC CONDITIONS, Hydrotechr1:ical C o n s t r u c t i o n , N S ,, Aug 1 9 7 5 , p p . 731-735.

I n d u s t r i a l s l a g p o r t l a n d cements produced from g r a n u l a r magnesia s lags were s t u d i e d c o n c u r r e n t l y with l a b o r a t o r y s l ag p o r t l a n d cemen t s . A:-1 p a s s e d t h e a u t o c l a v e t es t s f o r u n i f o r m i t y c : f vo:-ume change unde r a p r e s s u r e o f 20 k b / s q c m . There w e r e v i r t u a l l y n3 d e f o r m a t i o n s i n 180-day spec imens . S tudy r e s u l t s sh0 .u t h a t t h e s t r e n g t h of s l a g p o r t l a n d cement: (SPC) i n c r e a s e s s t e a d i l y , and afzer 2 year:; exceeds t h e c l a s s i ca l 28-day s t r e n g t h by a f a c t o r of 1 . 5 - 2 . 0 . A s compared w i t h t h e c o n v e n t i o n a l S I C S , t h e magnesia S P Z s f o l l o w a high s t r e n g t h g a i n i n d i c a t o r from 28 t o 3 6 0 days ; t h i s has a p o s i t i v e effect on massfive c o n c r e t e placed i n h y d r a u l i c s t r u c t . u r e s . A s compared w i t h t h c o n v e n t i o n a l SPCs t h e magnesia S P C s e x h i b i t an even lower heat liberation, a m o u n t i n c - t o :34 and 4 5 cal . /g a f t e r 3 and 7 days o f h a r d e n i n g r e spec t ive ly . The q u a l i t y of magnesia SPC w a s assessed frorr. c o m p a r a t i v e c o r r o s i o n - r e s i s t a n c e t es t s , and , t he s t r u c t u r a l - e n g i n e e r i n g p r o p e r t i e s of t h e mc.gnesia SPC were teste.5 d i r e c t l y i n c o n c r e t e . The inveE. t iga t ion : ; c o n f i r m t h a t magnes ia -s lag-based s l a g po r t1a r .d cement:; s a t i s f y t h e t e c h n i c a l s p e c i f i c a t i o n s and t,hc:.t t h e y are s u i t a b l e f o r massive c o n c r e t e i n hydrau1i .c s t : r u c t u r e s . T r a n s l a t e d from Gid ro tekhn icheskoe Sqz ro i t e l s tvo , N o . 81 August 1975, pp 15-18 .

1036. P l a t o u , J . , llSULPHUR-IM?REGNA'TEI:) CONCRETIZ, I' Sulphur I n s t i t u t e J o u r n a l , Vo l . 13., No. 1, 1375, p p . 2 - 4 .

Sulphur i s a low-cost mol ten m a t e r i a l which s o l i d i f i e s on c o o l i n g and s a t i s f i e s -:he 3 c r i t e r i a r e q u i r e d o f a m a t e r i a l t h a t cou;l.d impregnate c o n c r e t e . High s t r e n g t h c o n c r e t e s have 5een produced by i m p r e g n a t i n g l o w - s t r e n g t h c o n . z r e t e s ( a g g r e g a t e : cement r a t i o o f 8-8.5) w i t h s u l p h u r . Lean c13ncretes r e q u i r e o n l y 3 /4 o r less of t h e amount of p o r t l a n d cement used i n h i g h - s t r e n g t h c o n c r e t e s . Sul.phur i m p r e g n a t i o n of l e a n c o n c r e t e i n c r e a s e s i t i s compress ive s t r e n g t h from

1 t;

less t h a n 1 /3 t o 1-1/2 t i m e s t h a t o f high s t r e n g t h c o n c r e t e . Maximum a b s o r p t i o n o f s u l p h u r i s a c h i e v e d by c a r r y i n g o u t t h e impregna t ion i n mol t en s u l p h u r u n d e r vacuum. i m p r e g n a t i o n levels may a l s o be achieved w i t h o u t t he u s e o f vacuum. T h e 8 - f o l d i n c r e a s e i n compress ive s t r e n g t h achieved i n t h e vacuum i s reduced t o 5 - f o l d w i t h o u t vacuum. S t u d i e s a l s o show t h a t whi le i m p r e g n a t i o n o f high s t r e n g t h c o n c r e t e i n c r e a s e s i t s f i n a l s t r e n g t h t o a v a l u e higher t h a n t h a t of low s t r e n g t h c o n c r e t e , t h e r e l a t ive i n c r e a s e i n s t r e n g t h and t h e amount o f s u l p h u r abso rbed are smaller. Su lphur impregna ted c o n c r e t e (SIC) may be u s e d where high s t r e n g t h , r e s i s t a n c e t o w a t e r p e n e t r a t i o n , chemicals e tc . are r e q u i r e d . Available i m p r e g n a t i n g t e c h n o l o g y i s a p p l i c a b l e t o p r e c a s t c o n c r e t e s t r u c t u r e s , whi le s u i t a b l e t e c h n o l o g y f o r i m p r e g n a t i n g cast-in-place c o n c r e t e needs t o be deve loped .

AND HARDENED CONCRETE, I' F i n a l R p t . , P e n n s y l v a n i a Department o f T r a n s p o r t a t i o n ; Bureau o f Mater ia ls , T e s t i n g and Research , Feb 1975, pp . 73.

Recent work i n d i c a t e s t h a t s a t i s f a c t o r y

1 0 3 7 . Reidenouer , D . and Howe, R . , "AIR CONTENT O F PLASTIC

A combined f i e l d and l a b o r a t o r y t e s t i n g program was conduc ted t o compare a i r c o n t e n t i n p l a s t i c and ha rdened c o n c r e t e and t o s t u d y t h e r e l a t i o n s h i p of a i r c o n t e n t t o v i b r a t i o n and compress ive s t r e n g t h . Twelve p l a i n c o n c r e t e s labs were placed unde r normal f i e l d c o n d i t i o n s . The s labs r e p r e s e n t e d three levels o f a i r c o n t e n t , two levels of v i b r a t i o n , and two t y p e s of c o a r s e aggregate. Both t h e p l a s t i c and ha rdened c o n c r e t e w a s s u b j e c t e d t o a number o f d i f f e r e n t t es t s . A i r meter (Acme t y p e ) t es t s per formed by d i f f e r e n t o p e r a t o r s on t h e same b a t c h o f p l a s t i c c o n c r e t e have a 95% p r o b a b i l i t y of b e i n g w i t h i n 0.80% o f t h e mean. A n a l y s i s of v a r i a n c e of l i n e a r traverse data revealed t h a t tes t also h a s good p r e c i s i o n , as l o n g as t h e a i r c o n t e n t d o e s n o t exceed 7 % . There i s e s s e n t i a l l y no change i n t h e e n t r a i n e d a i r c o n t e n t between p l a s t i c and ha rdened c o n c r e t e . However, v i b r a t i o n does v e r y s i g n i f i c a n t l y r e d u c e e n t r a p p e d a i r . R e s u l t s o f f r e e z e / t h a w tes ts reaff i rm t h e v a l u e o f e n t r a i n e d a i r v o i d s i n cement paste i n p r e v e n t i n g f r o s t damage t o c o n c r e t e .

1038 . Roy, D . and Gouda, G . , " O P T I M I Z A T I O N OF STRENGTH I N CEMENT PASTES," Cement and Concre t e Research, V o l . 5, No. 2, Mar 1975, pp. 153-162.

I t h a s been demons t r a t ed t h a t p o r o s i t y i s by f a r t he dominant c o n t r o l l i n g f a c t o r i n l i m i t i n g s t r e n g t h o f h y d r a t e d cement paste . Mechanical means have been employed i n t h e p r e s e n t s t u d y t o minimize t h i s

1 7

p o r o s i t y , ' h o t p r e s s i n g ' unde r r a t h e r modest t e m p e r a t u r e s and p r e s s u r e s , p r o d u c i n g mat.erials h a v i n g v e r y low p o r o s i t y and u n u s u a l l y h igh s t r e n g t h . A new r e l a t i o n s h i p t o describe the i n t e r r e l a t i o n o f s t r e n g t h and p o r o s i t y i s g i v e n , and t h e effect. o f m a t u r i t y of spec imens , compos i t ion and mic ros t ruc : tu re a re i l l u s t r a t e d . Though t h e o r e t i c a l dens i . ty h a s n o t y e t been achieved, t he cement pastes have compress ive s t r e n g t h s (as w e l l as t e n s i l e arid s h e a r s t r e n g t h s ) an o r d e r o f magni tude h i g h e r t h a n i n normal1.y h y d r a t e d cements , are s tab le and d u r a b l e , and have d e n s e i n t e r p e n e t r a t i n g m i c r o s t r u c t u r e s .

1 0 3 9 . Schmidt , W . and Hoffman, E . , " 9 0 0 0 P S I CONCRETE--WHY? WHY NOT?," ASCE C i v i l Eng inee r ing , V o 1 . 45 N o . 5, May 1 9 7 5 , pp. 52-55.

High s t r e n g t h c o n c r e t e i s b e i n g u s e d i n many h i g h - r ise apa r tmen t and o f f i c e b u i l d i n g s . I n t h i s case, high s t r e n g t h means 9000 p s i ( 6 2 . 0 MPa) . Q u a l i t y c o n t r o l , aggregate a v a i l a b i l i t y and s p e c i f i c a t i o n r e s t r i c t i o n s are the f a c t o r s t h a t seem t o have he ld back t h e g e n e r a l u s e o f s t r o n g e r c o n c r e t e s . I n some areas these f a c t o r s have been e l i m i n a t e d and t h e r e s u l t i n g s a v i n g s are w e l l worth c o n s i d e r i n g . R e i n f o r c e d c o n c r e t e c o n t i n u e s t c rep:Lace s t r u c t u r a l steel i n t a l l e r and t a l l e r s t r u c t u r e s . The l i m i t of r e i n f o r c e d c o n c r e t e c a p a c i t y has n o t been reached, b u t it i s up t o t he s t r u c t u r a l e n g i n e e r t o e x p l o r e t h e p o t e n t i a l s o f high s t r e n g t h c o n c r e t e i n his own r e g i o n .

1 0 4 0 . Spel lman, D. and Woodstrom, J. e t a l . , "CONCRETE AGGREGATE DURABILITY TESTS, F i n . a l R p t . 415, C a l i f o r n i a Department of T r a n s p o r t a t i o n , Dec 1 9 7 5 .

S e v e r a l p r o c e d u r e s are s t u d i e d i n an attempt t o d e v e l o p a less t i m e consuming sL.bstil;ute f o r t h e sodium s u l f a t e soundness t e s t . Cons ide red w e r e p r o c e d u r e s u s i n g e l a s t i c f r a c t i o n a t i o n , heavy media s e p a r a t i o n , a u t o c l a v e d e g r a d a t i o n , f:reez:ing and thawing o f aggregates, and o t h e r s . One p r o c e d u r e , d e t r i t i o n v a l u e t es t , c o r r e l a t e s , f a i r l y w e l l w i t h soundness tes t l o s s e s f o r aggregates from one area o f t he s t a t e where t he soundness t e s t i s a c o n t r o l l i n g f a c t o r i n aggregate p r o c e s s i n g . T h i s p r o c e d u r e c o n s i s t s o f t he dynamic abrasior- : of water and aggregate i n a 5 g a l l o n b u c k e t o n a p a i n t shaker . A tes t method w a s deve loped and ar. a l t e r n a t e s p e c i f i c a t i o n t o t h e soundness t .est r e q u i r e m e n t w r i t t e n f o r c o n t r o l o f a g g r e g a t e q u a : l i t y . The s p e c i f i c a t i o n i s c u r r e n t l y l imi t .ed t ( 2 a g q r e g a t e s frorr! the S a n t a Clara R i v e r a r e a n e a r V e n t u r a . Prepared in

18

c o o p e r a t i o n w i t h Federal Highway A d m i n i s t r a t i o n , Washington, D . C .

1 0 4 1 . Swamy, R. N . and Ibrahim, A. B . e t a l . , "STRENGTH AND DEFORMATION CHARACTERISTICS OF H I G H EARLY STRENGTH STRUCTURAL CONCRETE," Ma te r i aux e t C o n s t r u c t i o n s , Materials and S t r u c t u r e s , Vol 8 , No. 48, Nov-Dec 1 9 7 5 , pp . 413-423.

T e s t s u s i n g a n u l t r a f i n e cement w i t h expanded s l a t e l igh tweight aggregate and g r a n i t e produced c o n c r e t e s w i t h a s t r e n g t h of 30-40N/mm**2 and 60-70 N/mm**2 r e s p e c t i v e l y i n 24 h o u r s . Tests w i t h a luminous cement produced be t te r a g g r e g a t e - m a t r i x bond and deve loped s t r e n g t h s of abou t 9 5 N/mm**2 i n t h e same t i m e . E q u a t i o n s are p r e s e n t e d t o p r e d i c t t h e t e n s i l e s t r e n g t h and e l a s t i c i t y of t h e high e a r l y s t r e n g t h c o n c r e t e . I t i s shown t h a t t h e rap id h y d r a t i o n r e s u l t s i n a high r a t e of s h r i n k a g e and c r e e p i n i t i a l l y b u t t h e long- te rm d e f o r m a t i o n c h a r a c t e r i s t i c s are comparable t o normal c o n c r e t e .

RESISTANT CONCRETE, '' Waterways Experiment S t a t i o n , F i n a l R p t . , Jun 1975, pp . 38 .

1 0 4 2 . Tynes, W . , "INVESTIGATION OF HIGH-STRENGTH FROST-

T h i s s t u d y w a s conducted t o d e t e r m i n e if r e d u c t i o n i n a i r c o n t e n t by v i b r a t i o n of a w e l l p r o p o r t i o n e d c o n c r e t e m i x t u r e of r e l a t i v e l y high cement c o n t e n t r e d u c e s t he f r o s t r e s i s t a n c e o f t h e ha rdened c o n c r e t e and a l s o t o d e t e r m i n e t he effect of such r e d u c t i o n i n a i r c o n t e n t on compress ive s t r e n g t h . One 3 / 4 - i n . (19.0-mm) maximum-size c r u s h e d l i m e s t o n e aggregate c o n c r e t e m i x t u r e w a s p r o p o r t i o n e d t o have a compress ive s t r e n g t h o f approx ima te ly 5 5 0 0 p s t (37 .92 MPa) a t 28 d a y s age. The m i x t u r e had a n a i r c o n t e n t o f 8 p l u s o r minus % . V a r i o u s v i b r a t i o n times were u s e d t o r e d u c e t he a i r c o n t e n t u n t i l t h e samples had an a i r c o n t e n t as low as c o u l d be p r a c t i c a l l y o b t a i n e d . Specimens w e r e cast f o r d e t e r m i n i n g compress ive s t r e n g t h , r e s i s t a n c e t o f r e e z i n g and thawing , and a i r v o i d p a r a m e t e r s t o e v a l u a t e t h e e f fec t of r e d u c t i o n i n a i r c o n t e n t of t h e c o n c r e t e on s t r e n g t h and f r o s t r e s i s t a n c e .

1043. Washa, G . and Wendt, K . , " F I F T Y YEAR PROPERTIES O F CONCRETE," American Concre t e I n s t i t u t e , J o u r n a l o f , Vo l . 72, No. 1, J a n 1975, p p . 20-28.

Compressive s t r e n g t h , u n i t weight, and volume changes o f c o n c r e t e f o r ages up t o 50 y e a r s have been d e t e r m i n e d . Variables i n c l u d e d are t y p e s of cement and c o a r s e aggregate, mix p r o p o r t i o n s , c o n s i s t e n c y , methods of p lacement , and s t o r a g e c o n d i t i o n s . Over

19

2500 c o n c r e t e c y l i n d e r s , 132 c o n c r e t e e x p a n s i o n prisms, and several thousand m o r t a r c y l i n d e r s and b r i q u e t s were made i n 1 9 1 0 , 1 9 2 3 , and 1937 f o r t h i s program. E a r l i e r r e p o r t s cn these t e s t s were p u b l i s h e d i n 1931, 1943, and 1 9 6 1 . Under c u t d o o r s t o r a g e i n Madison t h e compress ive st r e n q t h of c o n c r e t e made w i t h c o a r s e l y ground cements h a v i n g h igh C2S c o n t e n t s g e n e r a l l y i n c r e a s e d as the l o g c:f t h e age o u t t o 5 0 y e a r s , b u t c o n c r e t e made wi th f i . ne r cements h a v i n g r e l a t i v e l y low C2S c o n t e n t s a p p e a r e d t o reach maximum s t r e n g t h a t ages be tween 1 3 t o 2 5 y e a r s and showed some r e t r o g r e s s i o n thereaf te r .

1 0 4 4 . Wilson, A . , "DURABILITY O F CONCRETE AND CONCRETE STRUCTURES BY SLOW CYCLE F A T I G U E , 'I Durabf i l i t y o f C o n c r e t e . K a t h e r i n e and Bryan t P:athe:r I n t e r n a t i o n a l Conference , A t l a n t a , Georg ia , USA, 2'7 April-May 1 9 7 5 , pp. 259-291.

Effects o f f r e e z i n g a t an e a r l y age as w e l l a s t h e effects of a i r e n t r a i n m e n t were e v a l u a t e d and compared t o s t a n d a r d c u r e d spec imens . Mic roscop ic s t u d y of spec imens w a s u s e d as a f u r t h e r mean:; o f compar ison and a s a method o f o b s e r v a t i o n a n d e v a l u a t i o n . A c a l c u l a t i o n of a d u r a b i 1 i t . y f a c t o r and the t o t a l number o f c y c l e s - t o - f a i l u r e were u s e d t o e v a l u a t e t h e r e s u l t s . I t was found t h a t ear l>, freezinc; of c o n c r e t e had a d e t e r i o r a t i n g effect. on c o n c r e t e which was l a t e r s u b j e c t t o slow c y c l e f a t i g u e l v a d i n g s . I t w a s d e m o n s t r a t e d t h a t v i s ib l e e v i d e n c e c o u l d a l s o be observed through a m i c r o s c o p i c s t u d y of c o n c r e t e spec imens .

1976

t

1045. Barrick, J. E. I1 and Krokosky, E. M., "EFFECTS OF TEMPERATURE AND RELATIVE HUMIDITY ON STATIC STRENGTH OF HYDRATED PORTLAND CEMENT," Journal of Testing & Evaluation, Vol. 4, No. 1, 1976, pp. 61-73.

This paper delineates the effects of temperature and relative humidity on static strength (fatigue) of hydrated portland cement mortar. An experimental program involving the static loading of small cement- sand beams at varying conditions of temperature and relative humidity was undertaken to obtain information on the time required for fracture. This data was analyzed with a statistical procedure developed for truncated, lognormal distributions. The results are presented as cumulative probability distributions. A stress-corrosion mechanism dependent on the presence of calcium hydroxide is postulated as a result of this study.

1046. Bazant, Z . P. and Osman, E., "DOUBLE POWER LAW FOR BASIC CREEP OF CONCRETE," Materiaux et Constructions, Materials and Structures, Vol. 9, No. 49, 1976, pp. 3- 11.

The paper demonstrates that, in conjunction with the power law for the shape of creep curves, a power function of the duration of creep describes very closely the age effect and, in the limit, the age- dependence of the conventional elastic modulus as well. Additional evidence in support of the power law for the shape of creep curves is also presented. The law is limited to basic creep, but with different values of material parameters it can also describe drying creep up to a certain time. The simplicity of t h e double power law is a major advantage for statistical evaluation of test data.

1047. Bazant, Z . P. and Osman, E. et al., "PRACTICAL FORMULATION OF SHRINKAGE AND CREEP OF CONCRETE," Materiaux et Constructions, Materials and Structures, Vol. 9, NO. 54, 1976, pp. 395-406.

A set of algebraic formulas is proposed to describe the shrinkage and creep of concrete over the entire range of time durations of interest. The formulas cover: the effects of drying at various environmental relative humidities, the size and shape of cross section, aging (due to hydration), the effect of time lag of loading after the start of drying, creep of specimens predried to various humidities, the nonlinear dependence of stress, the increase of

2 1

n o n l i n e a r i t y a t s i m u l t a n e o u s d r y i.ng, and t h e d e c r e a s e o f s t r e n g t h f o r long-t ime loses. S i m F l i f i c a t i o n i n ti-;? form o f a l i n e a r dependence on s.:.ress i s o b t a i n e d a s special case.

1048. C l i f t o n , J . and F r o h n s d o r f f , G . , "POL,YMEF:-IMPREGNF-TET) CONCRETES, I' Cements Research F'rcqress, F i n a l R p t . , 1 9 7 6 , p p . 173-196.

Developments i n the s c i e n c e arid t echnc , logy of po lymer- impregnated c o n c r e t e s ( P I C ' S ) , up t o December 1 9 7 5 , are c o v e r e d i n t h i s revi.ew., P I C ' S a . r e import .ant members o f t h e g roup o f conc re t e -po lymer s y s t e m s . P I C has been d e f i n e d as ' a p r e c a s t port lE.nd cement c o n c r e t e impregna ted w i t h a monomer sys t em t h a t i s s u b s e q u e n t l y po lymer i zed i n s i t c ' . T h e t e r m P I C i s applicable t o precast c o n c r e t e s and m o r t a r s which are f u l l y - i m p r e g n a t e d and t h o s e which a re p a r t i a l l y - impregna ted t o a f i n i t e d e p t h . S u l f u r - i m p r e g n a t e d c o n c r e t e s are a l s o i n c l u d e d i n t h i s review, b u t o t h e r concre te -polymer sys tems, such as po lymer -conc re t e and po lymer -conc re t e , are n o t .

1 0 4 9 . Dunstan, E . J . , "PERFORMANCE O F L I G N I T E AND SUBBITUMINOUS FLY ASH I N CONCKETE - A PROGRESS REPORT," Bureau o f Reclamat ion; Denver Federal C e n t e r , P r o g r e s s Repor t , J a n 1.976, pp. 30.

V a s t reserves of subbi tuminous and l i g n i t e coal.. w i l l be u s e d i n power p r o d u c t i o n i n t h e IJn i ted S t a t e s i n t h e years t o come. A byproduc t , f1.y ash, c o l l e c t e d from t h e f l u e gases o f c o a l b u r n i n g p o w e r p l a n t s w i l l be produced i n large q u a n t i t i e s . S i n c e bi. tuminous coa:L f l y ash has been u s e d i n c o n c r e t e t o c o n s i d e r a b l e a d v a n t a g e f o r several y e a r s now, it i s q u i t e l i k e l y t h a t s i m i l a r u s e c o u l d be made of l i q n i t e and subb i tuminous c o a l f l y ashes. If! s o , t h i s mater ia l c o u l d p r o v i d e a p l e n t i f u l supp ly of' a p o t e n t i a l l y low c o s t cement ing medium f o r u s e wi.th p o r t l a n d cement .i:? c o n c r e t e . F l y ashes were o b t a i n e d from fi-ve Western U n i t e d States p o w e r p l a n t s . A complete chemica l and physical a n a l y s i s o f each l i g n i t e and subb i tuminous ash w a s made and none were found t o rneet a l l r e q u i r e m e n t s f o r a C l a s s F pozzc:lan a c c o r d i n g t o Federal S p e c i f i c a t i o n SS-P-570B. C o n c r e t e mixes w e r e made w i t h 15 and 25 percent_ r ep lacemen t o f cement, by weight , w i t h these f l y a s h e s , a n d cornpared t o a m i x c o n t a i n i n g no f l y ash and t o m i x e s con ta i -n ing 15 and 2 5 p e r c e n t r ep lacemen t of f l y ash meet inq t h e r e q u i r e m e n t s f o r a Class F p o z z c l a n . The r e s u l t i n g ha rdened c o n c r e t e w a s found t o have a d e q u a t e compress ive s t r e n g t h , reduced d r y i n g shr:-nkage, aI;d s a t i s f a c t o r y f r eeze - thaw & J r a b i l i t y , b u t , i n scme

2 2

cases, drastically reduced resistance to sulfate attack.

1050. Fitzgibbon, M., "LARGE POURS FOR REINFORCED CONCRETE STRUCTURES," Concrete, Vol. 10, No. 3, Mar 1976, pp. 41.

Reinforced sections of high-strength concrete, rich in cement, can be cast in one continuous pour whether 30 M3 or 3000 M3 in volume. The technique was developed to solve an increasing problem facing the construction industry when casting large amounts of structural-quality concrete for reinforced sections. Although it is current practice, some explanation of the technique is included where necessary to emphasize its striking contrast with the traditional method developed for mass concrete dam construction. This current practice sheet describes the principles and planning leading up to the decision to cast in one or monolithically.

1051. Griffin, D. and Nielsen, J., "ACOUSTIC-EMISSION CHARACTERISTICS OF PLAIN CONCRETE," New Mexico Univ Albuquerque Eric H Wang Civil Engineering Research Facility, Oct 1976, pp. 42.

The results of acoustic-emission tests on young concrete specimens and concrete cores from airfield pavements indicate that the Kaiser Effect is not permanent in concrete. That is, there is a recovery such that load cycles applied subsequent to the initial load cycle will produce acoustic-emission signals similar to those obtained during the first load cycle. This report suggests, therefore, that the Kaiser Effect cannot be used to detect the maximum past stress in concrete which has not been subjected to a continuous stress.

1052. Haque, M., "EFFECT OF MOISTURE CONTENT ON THE DIRECT TENSILE STRENGTH OF CONCRETE CYLINDERS AND PRISMS," New South Wales University, Australia School of Civil Engineering, Dec 1976.

The effects of desorption and water sorption on the tensile strength of concrete and hydrated cement paste cylinders and prisms are investigated. Two different techniques for the determination of the direct tensile strength i.e. Cylinders with embedded bars and prisms with glued end blocks are used. The results indicate that the concept of 'drying-strengthening' is not valid for the tensile strength of concrete where the 'drying-weakening' effects of desorption outweigh the strengthening effects due to the removal of moisture. The tensile strength of the concrete system on

23

d e s o r p t i o n and subsequen t rescirF::ion i s r e p o r t e d t o be dependent on t h e shape of t h e s p c i m e n s .

1053. H e w l e t t , P. and Rixom, R . , "SUPEXPLA$TICISED CONCRETE," Concre t e , Vol. i0, Nc.. 9 , Sep 1 9 7 6 , pp. 39- 42.

Data related t o mix d e s i g n , h a n d l i n g p r o p e r t i e s and p o s s i b l e u s e s of s u p e r - p l a s t i c : i z s d c o n c r e t e a re here condensed i n t o a u s a b l e p r a c t i . c e sheet. Two t y p e s of s u p e r p l a s t i c i z e d c o n c r e t e a r e d i s t i n g u i s k e d : f l o w i n g c o n c r e t e produced a t normal wa te r / cemen t r a t i o s b u t p o s s e s s i n g such ex t r eme w o r k a b i l i t y w i t h o u t excess i . ve b l e e d i n g o r s e g r e g a t i o n t h a t t h e c o n c r e t e can be placed w i t h l i t t l e o r no v i b r a t i o n or compact ion; wa te r - r educed h igh s t r e n g t h c o n c r e t e produced a t much lower water-cement r a t i o n s t h a n no rma l ly e x p e r i e n c e d and h a v i n g w o r k a b i l i t y i n t h e r ange t . r a d i . t i o n a i l y use(i by t h e i n d u s t r y . w o r k a b i l i t y are s u l p h o r a t e d melamine formaldehyde c o n d e n s a t e s and s u l p h o r a t e d n a p h t h a l e n e fo rma lde lhyde c o n d e n s a t e s .

The chemicals t h a t g i v e t h e high

1054. I v a n y i , G . , "EFFECTS O F A STRAIN GRADIENT ON THE TENSILE STRENGTH OF CONCRETE, 'I I n t Conf on Mech Behav of Mater, 2nd, P roc , Boston, Mass, Vo1. 2 , 1 9 7 6 , p p . 1108-1112.

The t e n s i l e s t r e n g t h of a c o n c r e t e specimen can b.3 described as a f u n c t i o n of stress o r s t r a i n g r a d i e n t , heterogeneity and geometry. Of t h e s e , h e t e r o g e n e i t y i s the most d i f f i c u l t f a c t o r to d e t e r m i n e b o t h e x p e r i m e n t a l l y and t h e o r e t i c a l l y . N e l t h e r a d i r e c t a p p l i c a t i o n o f t he l a w s of f rac t : i i re mechanics of homogeneous materials leads t o u s e f u l r e s u l t s , n o r s t a t i s t i c a l approaches w i t k ? , s t a t : . i s t i c a l u n i t s n o t i n acco rdance w i t h t h e h e t e r c g e n e o u s s t r u c t u r e of c o n c r e t e . The p a p e r a t t e m p z s t o c l ea r up some a s p e c t s of t h e problem f o r l i n e a r vary i r ig stresses b y u s i n g 2 s t a t i s t i c a l model t o g e t h e r w i t h a layered-beam f i r : i t 2 element.

1 0 5 5 . Kao, C. and Slate , F . , "TENSILE-SHEAR BOND STRENGTH AND FAILURE BETWEEN AGGREGATE AKD MORTAR, ASTM J o u r n a l o f T e s t i n g and E v a l u a t i o n , V o 1 . 4, N o . 2 , Mar 1 9 7 6 , p p . 148-150.

The p u r p o s e of t h i s s t u d y w a s t o i n v e s t i g a t e the t e n s i l e - s h e a r bond s t r e n g t h and f a i l u r e of t h e m o r t a r - aggregate i n t e r f a c e . The t e c h n i q u e s used a r e r e p o r t e d . The r e s u l t s i r ,d icate that: t h e Mohr f a i l u r ? e n v e l o p e i n t h e t e n s i o n - s h e a r q u a d r a n t i s a lmos t a s t r a i g h t l i n e and t h a t t h e fa:ilL;.re i s e s s e n t i a l l y t e n s i l e i n n a t u r e .

24

1056. Larsen, T. and McDaniel, W. J. et al., "CORROSION- INHIBITING PROPERTIES OF PORTLAND AND PORTLAND- POZZOLAN CEMENT CONCRETES," Transportation Research Record, N613, 1976, pp. 21-29.

Within the framework of studying properties that inhibit corrosion of concrete that contains admixtures and additives, concretes with various amounts of fly ash were tested and evaluated. Cylindrical specimens with a centrally located reinforcing bar were partially immersed in a 5 percent sodium chloride solution after various curing periods and curing procedures. A n impressed-curred test was used to accelerate the corrosion process. Time to cracking and current flow were measured, and total energy requirements to induce failure calculated. Other variables studied included sorption, resistivity, strength, consistency, and time to cracking failure of the specimens. Test results indicated that the use of possolznic material (fly ash) as an additive or an admixture improves the property of the concrete to prevent corrosion of the embedded reinforcing steel.

1057. Malhotra, V., "ARE 4 X 8 INCH CONCRETE CYLINDERS AS GOOD AS 6 X 12 INCH CYLINDERS FOR QUALITY CONTROL OF CONCRETE?," American Concrete Institute, Journal of, Vol. 73, No. 1, Jan 1976, pp. 33-36.

This paper reports data which have become available at the CANMET over the past several years as to the relative merits of 4 x 8 in. (102 x 203 mm) and 6 x 12 in. (152 x 305 mm) cylinders for quality control of concrete. The types of concrete investigated incorporated limestone and gravel as the coarse aggregates and natural sand as the fine aggregate. The nominal water-cement ratio varied from 0.33 to 0.87. Each set of test specimens consisted of two 4 x 8 in. (102 x 203 mm) and two 6 x 12 in. (152 x 305 mm) cylinders, cured under standard moist room conditions and tested at ages ranging from 3 days to about 8 months. The analyses of the data indicate: (a) That the compressive strengths of 4 x 8 in. (102 x 203 mm) cylinders are higher than those of 6 x 12 in. (152 x 305 mm) cylinders. There are, however, indications that at low strength levels, the reverse may be true. (b) That the difference in the strength of two sizes of cylinders increases with an increase in the strength level of concrete. (c) That the standard deviation of the compressive strength of test cylinders increases with decrease in the cylinder diameter as indicated by Tucker's 'summartion- strength' theory. However, the magnitude of this increase is such that considerably more than twice t h e

25

number of 4 x 8 i n . ( 1 0 2 x 203 m m ) c y l i n d e r s w i l l haiJe t o be tested f o r each 6 x 1 2 i n . (152! x 3 0 5 mm) c y l i n d e r t o o b t a i n t he same degree off p r e c i s i o n .

1058. Maschmann, M . , "CONCRETE POKERS, " C i v i l E h g i n e e r i n g , May 1 9 7 6 Ser ia l , pp . 3-32.

The a r t i c l e d i s c u s s e s t h e develcjpment of e l e c t r o - mechan ica l p o k e r v i b r a t o r s and their impor t ance i n a c h i e v i n g h i g h - s t r e n g t h , q u a l i t y c o n c r e t e w i t h t h e e l i m i n a t i o n of a i r v o i d s . Optimum c o n c r e t e d e n s i t y c a n be achieved by e f f i c i e n t compact ion i-f the frequerlcy o f v i b r a t i o n c o i n c i d e s w i t h t h e r e s o n a n t f r e q u e n c y cf the c o n c r e t e g r a i n s . C u r r e n t c o n c r e t e mixes are s a i d t o r e q u i r e a working frequ.ency o:f i n t e r n a l v i b r a t i o n o f a b o u t 200 c p s . F l ex ib l e . s h a f t - d r i v e n : - n t e r n a l v i b r a t o r s o r i g i n a l l y c o n s i s t e d c f a dr ivr -ng motor of o p t i o n a l ene rgy form, a f l e x i b l e sha f t guided by A p r o t e c t i v e hose , and, i n t e r c h a n g e a b l e v i b r a t i n g heads a c c o r d i n g t o s i t e r e q u i r e m e n t s . La te r h igh - f r equency d e s i g n s f e a t u r e d a b u i l t - i n e l e c t r i c motor d r i v i n g an e c c e n t r i c a l l y mounted, o r rolILifig, weight: t o p roduce c e n t r i f u g a l f o r c e s . A simpler d e s i g n i s t h e compressed a i r i n t e r n a l v i b r a t o r which i n c c r p o r a t e s an ou t -o f - b a l a n c e mass r o t a t i n g on a carr iage and :is s i m i l a r t o t he f l e x i b l e s h a f t equipment . T k . i s design has t h e d i s a d v a n t a g e t h a t t h e hose must be less t h a n 4 M l o n g t o m a i n t a i n pe r fo rmance . La ter Yypes have h igher o p e r a t i n g speeds w i t h a u t o m a t i c v i b r a t i o n c o n t r o l and p roduce 13000-18000 rpm a c c 0 r d i r . g t o c o n c r e t e consistency.

1 0 5 9 . Sakata, K . and N i s h i b a y a s h i , S . , "STUDY (1" THE MECHANISM OF CREEP OF CONCRETE, I' T r a n s a c t i o n s of t h e Japan S o c i e t y o f C i v i l Engineer:!, Vo:L. 7,. 1 9 7 6 , p p . 171-172.

T o e x p l a i n t he c r e e p mechanisn of c o n c r e t e , t h e creep tes t and m o i s t u r e l c l s s ( w a t e r :LOSS:I t e s t w e r e pe r fo rmed i n t h i s s t u d y on t h r e e d i f f e r e n t k i n d s of c o n c r e t e s ( w i t h a c r u s h e d s t o n e and two k i n d s of l i gh twe igh t aggregates) . From t k . e t e s t r e s u l t s , t h e r e l a t i o n s h i p between c r e e p s t r a i n and amcunt of m o i s t u r e l o s s from t h e specimen a s w e l l as t h e e f f e c t o f ambient r e l a t i v e humid i ty on c r e e p a n d m o i s t u r e l o s s i s d i s c u s s e d .

1 0 6 0 . Sandonato , A . , "EVALUATION OF IL'TERNALLY SEALED CONCRETE, '' I n t r m R p t . 1 8 , Massac 'huse t t s Eepartment . of P u b l i c Works, D e c 1 9 7 6 ,

T h i s r e p o r t re la tes t o t h e f i e l d : i n s t a l l a t i o n p r o c e d u r e f o l l o w e d i n t h e p l a c i r - g of t h e i n t e r n a l l y sealed c o n c r e t e a t two o f t h e f i v e s e c t i c l n s of o v e r l a y

on the Austin Street Bridge in Boston (Charlestown) Mass.

1061. Sauer, J. and Nawy, E. et al., "STRENGTH IMPROVEMENTS IN MORTAR AND CONCRETE BY ADDITION OF EPOXIES," Transportation Research Record, N613, 1976, pp. 30-36.

To raise the tensile strength of cement mortar and concrete, we conducted a series of experiments in which suitably formulated spoxy resins were added to standard cement mortar and to selected concrete mixes. Tensile and compressive strength measurements were made on various formulations, and strengths were determined as a function of epoxy-added content. Both tensile and compressive strengths are apprecibly increased by additions of epoxy to cement mortar and concrete. These additions are 5 and 10 percent by weight of mortar for the cement mortar and concrete respectively. The effects of polymer additions on aggregate-paste bond have been studied by use of a scanning electron microscope. The influence of the epoxy on workability, stiffness, and water absorption is also discussed.

1062. Skalny, J. and Odler, I., "USE OF ADMIXTURES IN PRODUCTION OF LOW-POROSITY PASTES AND CONCRETES," Transportation Research Record, N564, 1976, pp. 27-38.

This paper reviews the results of studies on the development of a low-porosity, high-strength cement paste and concrete. The paste is made by mixing finely ground cement clinker, containing alkali or alkaline earth lignosulfonates, with 0.20 to 0.30 parts water containing alkali carbonate. Concretes and mortars made with low-porosity cement paste have improved strength, dimensional stability, and other engineering properties.

1063. Sullivan, T. and McBee, W., "DEVELOPMENT AND TESTING OF SUPERIOR SULFUR CONCRETES," Bureau of Mines; Boulder City Metallurgy Research Laboratory, Boulder City, Nevada, Sep 1976, pp. 37.

The preparation and testing of sulfur concretes were investigated by the Bureau of Mines as one part of a sulfur utilization program. Modified sulfur concretes were developed by reacting the sulfur with unsaturated hydrocarbons before mixing the molten sulfur and hot aggregate. Physical properties of optinum mixes for both sulfur concrete and modified sulfur concretes, prepared with various aggregates, were determined and compared with Portland cement concretes. The resultant modified sulfur concretes had properties equal to or better than those of unmodified

27

s u l f u r concre tes and Por t land cement concre te depending on t h e types of aggregate used.

1 0 6 4 . Yimprasert, P . e t a l . , "DURABILITY, STRENGTH, AND METHOD OF APPLICATION OF POLYMEF:--IMPF'EGNATED CONCRETE FOR SLABS, '' C e n t e r f o r Highway Ftesearch, Texas Univers i ty , Austin, TX, Jan 15376, pp. 2 3 0 .

The app 1 i c a t ion of po 1 yme r - imp regri a t ed con c r e t e ( P I C ) f o r improving t h e durablli.l:y of! concre te s l a b s , e s p e c i a l l y highway br idge decks, has been w i d e l y i n v e s t i g a t e d . For t h i s aFp l i ca t ion , t h e s l a b i s p a r t i a l l y impregnated frorr. t h e upper s u r f a c e . Parameters such a s drying t i m e and temperature , soaking t i m e , and cur ing t i m e and ter iperature , whlch, of course, can inf luence the d u r a b i l i t y of concre te br idge decks a f t e r impregnation, w e r e t h o r o u g h l y i n v e s t i g a t e d . The monomer system of m e t h y l methacrylate (MMA) w i t h 18 (by weight:) benzoyl peroxide (BP) and 1 0 % (by weight) t r i m e t h a c r y l a t e (TMPTMA) was gene ra l ly used thrcughout the t e s t s . A dry ing temperature of more than 212 degrees F t o 3 0 0 degrees F was acceptab le f o r t h e s l a b s t e s t e d . T o ob ta in a t l e a s t a 1 - i n . polymer depth, a soaking t i m e of 4 hours o r more w & s necessary. Steam was found t o be an economical, s a f e and workable cur ing source f o r f i e l d treatment.. WiYh adequate steam, t h e monomer i n concre te can be curec. w i t h i n :30 m i n u t e s . .A cu r ing temperature of a t l e a s t 140 degrees F i s necessary t o achieve adequate polymer depth . I t i s recommended t h a t t h e m i n i m u m c u r i n g t i m e and temperature of 60 minutes and 15'0 degrees F, r e s p e c t i v e l y , should be used f o r a c t u a l f i e l d impregnations. T h e durabi . l i ty of pa:rtia.lly- impregnated s l a b s was eva lua ted 'by freeze-thaw tes ts conducted on 1 0 - i n . X 6 - i n . concre te s l a b s . I t was found t h a t t h e d u r a b i l i t y performance of concre te was s i g n i f i c a n t l y increased by P I C i.rnpregnat.ion.

2 8

1977

1065. Bromham, S. B., "SUPERPLASTICIZING ADMIXTURES IN HIGH STRENGTH CONCRETE," Symp on Concrete for Eng Eng for Concrete, Brisbane, Aust, Aug 30 1977, pp. 17-22.

This paper presents the results of a comprehensive investigation into the effects of the superplasticizing admixture Melment L10 on a range of structural concretes. The principal aim in designing the mixes was to achieve a slump of 70 mm for both plain and superplasticized concretes, and thus all comparisons are made between concretes of similar practical workability levels. The effects of superplasticizer dosage rate, cement content and type of cement on the properties of both the plastic concrete and hardened concrete are presented in some detail. The laboratory steam curing experiments and field trials using a variety of concrete mixing and curing techniques have allowed an assessment of the potential and problems of using superplasticizing admixture in the precast industry.

1066. Brooks, J. J. and Neville, A. M., "COMPARISON OF CREEP, ELASTICITY AND STRENGTH OF CONCRETE IN TENSION AND IN COMPRESSION, Magazine of Concrete Research, Vol. 29, No. 100, 1977, pp. 131-141.

A method of manufacturing a bobbin-shaped specimen for testing concrete in direct tension is described. Direct tensile strength is related to tensile and compressive strengths as determined by standard tests and their changes with age are described. Data on the modulus of elasticity in compression and in tension at two exposure conditions are given, and the influence of age upon creep and creep recovery is established. The difference in behavior of strength, modulus of elasticity, creep and creep recovery are discussed.

1067. Cedolin, L. and Crutzen, Y. J. et al., "TRIAXIAL STRESS-STRAIN RELATIONSHIP FOR CONCRETE," ASCE Journal of the Engineering Mechanics Division, Vol. 103, No. 3, Jun 1977, pp. 423-439.

A triaxial constitutive law and a failure criterion for concrete under short-term monotonic loading are derived from the analysis of available experimental data. Their representation through the octahedral normal and shear components of stresses and strains show that the deformational behavior of concrete can be described through simple analytical expressions relating the bulk and shear moduli to the first two invariants of the strain state. The values of the

29

t a n g e n t moduli are t h e n immedia te ly o b t a i n e d by d i f f e r e n t i a t i o n . The u l t i i n a t e s t r e n g t h c r i t e r i o n has: been e x p r e s s e d as a r e l a t i o n between o c t a h e d r a l s h e a r and normal stresses a t f a i l u r e i I i vo lv ing also t h e t h i r d stress i n v a r i a n t . T h e p roposed e q u a t i o n s both f o r t h e c o n s t i t u t i v e l a w and t h e f a i l u r e c r i t e r i o n a r e i n a s a t i s f a c t o r y agreemen-: w i t h expe r imen ta l . data anC. are s u i t a b l e f o r u s e i n numer i ca l schemes f o r p r e d i c t i n g t he r e s p o n s e of r e i n f o r c e d c o n c r e t e three- d i m e n s i o n a l s t r u c t u r e s .

1 0 6 8 . Chou, Y., " E N G I N E E R I N G BEHAVIOR OF PAVEMENT MATERIALS : STATE O F THE ART, 'I Waterways Experiment S t a t i o n ; S o i l s and Pavements Laborasory , F i n a l R p t . , H e b 1 9 7 7 , pp. 4 0 9 .

T h i s r e p o r t reviews the e n g i n e e r i n g b e h a v i o r of pavement materials w i t h r e s p e c t t o highway a n d a i r c r a f t l o a d i n g s and e n v i r o n m e n t a l c o n d i t i o n s . The mater ia ls c o v e r e d are b i tuminous m i x t u r e s , p o r t l a n d cement c o n c r e t e , g r a n u l a r mater ia ls , c h e m i c a l l y s t a b i l i z e d s o i l s , and f i n e - g r a i n e d s o i l s . Basic p r o p e r t i e s o f each are d i s c u s s e d . F o r b i t u m i n o u s m i x t u r e s , emphasis i s placed on t h e cha rac t e r i s t i c s of permanent d e f o r m a t i o n , f a t i g u e , and r h e o l o g i c a l p r o p e r t i e s and t h e a p p l i c a t i o n t o pavement d e s i g n of a c c u m u l a t i v e damage t h e o r y based on Mine r ' s h y p o t h e s i s . D i s c u s s i o n s are p r e s e n t e d on t h e development o f f a t i g u e c r i t e r i a from l a b o r a t o r y f a t i g u e t e s t s and d e s i g n c u r v e s . Fo r p o r t l a n d cement. concrete, concrete s t r e n g t h s d e t e r m i n e d b y v a r i o u s tes ts are d i s c u s s e d . T e s t p r o c e d u r e s f o r d e t e r m i n i n g t he modulus o f e l a s t i c i t y and P o i s s o n ' s r a t i o are p r e s e n t e d , t o g e t h e r w i t h discuss ion o f f a c t o r s a f f e c t i n g t h e s e v a l u e s . The f a t i g u e p r o p e r t y of c o n c r e t e and i t s r e l a t i o n s h i p t o pavement d e s i g n a r e d i s c u s s e d . Fo r g r a n u l a r materials, t h e r e s i l i e n t and p l a s t i c p r o p e r t i e s are d i s c u s s e d . C o n s t i t u t i v e stress- s t r a i n r e l a t i o n s p roposed by many a g e n c i e s a re p r e s e n t e d and compared. The r e l a t i o n s c o n s i s t of r e s i l i e n t , p l a s t i c , shear, and dynamic stresses and s t r a i n s . Because o f t h e h i g h l y n o n l i n e a r n a t u r e of g r a n u l a r mater ia ls , the v a l i d i t y of t h e s u p e r p o s i t i o n p r i n c i p l e i s appl ied t o pavement d e s i g n i s d i s c u s s e d . Fo r s o i l s t a b i l i z a t i o n , t he mechanisms of s t a b i l i z a t i o n are e x p l a i n e d , which i n c l u d e d s o i l - cement, s o i l - l i m e , l i m e - f l y ash, and l ime-cement - f ly ash and b i tuminous materials. F a c t o r s i n f l u e n c i n g e n g i n e e r i n g p r o p e r t i e s and p r o p e r t i e s o f s t a b i l i z e d s o i l s w i t h respect t o s t r e n g t h , modulus, and f a t i g u e are d i s c u s s e d . Fo r f i n e - g r a i n e d s u b g r a d e s o i l s , d i s c u s s i o n s a l s o c o n c e n t r a t e on the r e s i l i e n t a n d p l a s t i c p r o p e r t i e s . C o n s t i t u t i v e stress-strain r e l a t i o n s are p r e s e n t e d w i t h r e s p e c t t o r e s i l i e n t ,

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static, viscoelastic, plastic, dynamic, and shear properties. The modulus of subgrade reaction used in rigid pavements and the nature of expansive soils in relation to rigid pavement design are discussed.

CONCRETE: MATERIAL CHARACTERIZATION AND HEAT TREATING STUDIES," Intrm Rpt., Federal Highway Administration; Office of Research and Development, Mar 1977, pp. 73.

The work described herein was aimed at developing the information and processes necessary for efficient experimental construction of bridge decks using internally sealed concrete. This concrete is sealed by means of wax included in the mix, and was developed for use in bridge decks to prevent the penetration of water and chlorides to the reinforcing steel. Specific goals of the study were: (1) The development of safet, efficient field heating systems needed to melt the wax and seal the concrete. (2) The definition of the engineering properties of the particular internally sealed concrete specified for the experimental projects. phases, concrete cracking problems were encountered and circumvented by modifying the heating and bead- manufacturing processes. Heating equipment experiments performed to develop both small, single pass, fast- heating equipment and equipment which slowly heats a large area at once are described. Also discussed are the tests performed to document the engineering properties of internally sealed concrete (i.e., strength, bond to underlying concrete and reinforcing steel, abrasion resistance, skid resistance, shrinkage, etc.). Finally, the findings of an analysis of two prototype internally sealed decks built in 1975 and heat treated in 1976 are presented. Sponsored by DOT, Federal Highway Administration.

1069. Clear, K. and Forster, S., "INTERNALLY SEALED

During the early testing

1070. Fagerlund, G., "THE INTERNATIONAL COMPARATIVE TEST OF THE CRITICAL DEGREE OF SATURATION METHOD OF ASSESSING THE FREEZE/THAW RESISTANCE OF CONCRETE," Materiaux et Constructions, Rilem, N 5 8 , Jul 1977, pp. 231-253.

The paper describes the conduct and results of a study of the critical degree of saturation method. This study is part of the work carried out by the Rilem Committee 4CDC on freezing/thawing cycles. laboratories were involved. Tests were carried out on two types of concrete; one with and one without an air-entraining agent. degree of saturation was determined by means of freezing/thawing cycles and the critical degree of capillary saturation by means of water absorption. The differences found between the two are small.

Five

In each laboratory the critical

Up

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1071.

1 0 7 2 ,

t o now, t h e q u a n t i t a t i v e eva lua t . i on o f r e s i s t a n c e t o f r e e z i n g / t h a w i n g c y c l e s was near:Ly the s a m e i n a l l the l a b o r a t o r i e s .

F u j i t a , Y . and S a e k i , N . e t a l . , "F0EWAT::ON OF BOYD CRACK I N PLAIN CONCRETE," P roc ;lpn Congr Mater Rer; 2 1 s t , Tokyo, J apan , 1 9 7 7 , p p . 201-203 .

T h e crack i n i t i a t i o n of c o n c r e t e as a compos i t e material o c c u r s p r i m a r i l y a l o n g the : in t e r f ace between i n c l u s i o n and m a t r i x when a com1:ressive :Load i s applied, namely, bond cracks a re p roduced . The d e f o r m a t i o n and f a i l u r e of' c o n c r e t e are decidedly affected by the i n i t i a t i o n and ~ r o p a q a t i o n o f bond c r a c k i n g . T h i s p a p e r i s conce rned w i t h a n a l y t i c a l and e x p e r i m e n t a l s t u d i e s on the b e h a v i o r of hond crack i n i t i a t i o n . The bond s t r e n g t h s c f t h e i n t e r f a c e s between aggregate and mortar-mat r i x have been e x p r e s s e d by t h e enve lope cu rves d e f i n e d by t h e Coulomb-Mohr f a i l u r e t h e o r y , t h e n t h e s t : r e s s and i n c l i n a t i o n a n g l e a t t he bond c r a c k i n i t i a t i o n have been a n a l y z e d by a p p l y i n g t h e er ,ve lope ciirve t o t h e stress f i e l d of t h e i n t e r f a c e i x - c o n c r e t e . T o v e r i f y t h e above a n a l y s i s t he o b s e r v a t i o n o € t h e bond c r a c k i n i t i a t i o n was e x p e r i m e n t a l l y per formed on spec imens of c o n c r e t e .

Gomez-Toledo, C . , "STUDIES ON CE:MENT PASTE AND CONCRETE BOTH MADE WITH LOW POROSITY CEMENT," F i n a l R p t . 1 4 3 , Purdue and I n d i a n a S t a t e H.ighway Commission JHRP, J u l 1 9 7 7 , pp . 53.

Cement paste and c o n c r e t e w e r e examined i n d e t a i l . S t u d i e s w e r e carried o u t on t h e r h e o l o g i c a l b e h a v i o r p r i o r t o ha rden ing , on t h e h y d r a t i o n p r o c e s s , on t h e m i c r o s t r u c t u r e o f t h e ha rdened p r o d u c t s .in compress ive s t r e n g t h , on p e r m e a b i l i t y and 01-1 p o r e s i z e d i s t r i b u t i o n . For c o n c r e t e , t h e p r o p e r t i e s i n v e s t i g a t e d i n c l u d e d r h e o l o g i c a l b e h a v i o r and w o r k a b i l i t y i n t h e f r e s h s t a t e and compress ive s t r e n g t h , f l e x u r a l s t r e n g t h , and d y n a m i c modulus o f e l a s t i c i t y i n t h e ha rdened c o n d i . t i o n . I t was found t h a t e x c e l l e n t c o n s i s t e n c y and f low b e h a ~ i o r c o u l d be produced i n b o t h cement p a s t e s 2 n d c13ncretes f o r m u l a t e d a t low water c o n t e n t . Lower cement c o n t e n t s produced a l o s s of c.zInsiste:ncy and a d e g r a d a t i o n o f t h e f l o w p r o p e r t i e s of t h e f r e s h c o n c r e t e s . Higher cement c o n - t e a t s , ,311 t h e o t h e r hand, improved t h e w o r k a b i l i t y of c3ni::rete and i n c r e a s e d i t s compress ive s t r e n g t h . I t w a s found t h a t h y d r a t i o n o f t h e p a s t e w a s small o v e r t h e f i r s t 1 8 ho.-irs, b u t theri accelerated n o t i c e a b l y . The time of s e t t i n g of l3w p o r o s i t y cement paste was found t o c3inci .de a c c u r a t e l y w i t h t he end of i t s dormant peri .od a s i n d i c a t e d by

3 2

t e m p e r a t u r e e v o l u t i o n measurements . Fo r c o n c r e t e , compress ive s t r e n g t h development w a s rapid f o l l o w i n g t h e f i rs t day . I t was obse rved t h a t f l e x u r a l s t r e n g t h s and dynamic e l a s t i c m o d u l i i were s i g n i f i c a n t l y h i g h e r t h a n would be e x p e c t e d f o r h igh - s t r e n g t h c o n c r e t e s o f s imi la r compress ive s t r e n g t h made w i t h o r d i n a r y P o r t l a n d cement. Tests i n d i c a t e t h a t low p o r o s i t y cement paste i s much less permeable, less porous , and ' t i g h t e r ' t h a n o r d i n a r y P o r t l a n d cement paste a t any g i v e n age.

1 0 7 3 . G y l l t o f t , K. and E l f g r e n , L., "FATIGUE STRENGTH O F C I V I L ENGINEERING STRUCTURES," N a t i o n a l Swedish I n s t i t u t e f o r B u i l d i n g Research, Gavle, Sweden, 1 9 7 7 , pp. 1 6 0 .

T h i s r e p o r t examines t h e f a t i g u e s t r e n g t h of c i v i l e n g i n e e r i n g s t r u c t u r e s , b o t h o f s teel and of r e i n f o r c e d c o n c r e t e . Examples o f such s t r u c t u r e s are bridges, roads and a i r f i e lds , r a i l w a y sleepers, c r a n e r a i l s and overhead c r a n e t r acks , t r a n s p o r t i n s t a l l a t i o n s , machine f o u n d a t i o n s , mar ine c o n s t r u c t i o n s , wind power p l a n t s . The i n t e n t i o n i s t o give a review i n t h i s f i e l d o f b o t h e x i s t i n g knowledge and t h e areas where f u r t h e r knowledge i s needed . t o now e x i s t i n g t h e o r i e s c o n c e r n i n g f a t i g u e have been p r i m a r i l y applied t o simple b o d i e s . There i s no comple t e t h e o r y avai lable a t p r e s e n t c o n c e r n i n g t h e f a t i g u e process i n composi te s t r u c t u r e s . T h i s applies t o b o t h steel and r e i n f o r c e d c o n c r e t e s t r u c t u r e s . Des ign is t h e r e f o r e carried o u t a t p r e s e n t by a p p l i c a t i o n o f empirical r e l a t i o n s h i p s based on t e s t s . The r e p o r t examines i n d e p t h , f o r d i f f e r e n t materials and i n c o n j u n c t i o n w i t h material p r o c e s s i n g , the d i f f e r e n t stress and l o a d i n g c o n d i t i o n s as w e l l a s t h e s t r e n g t h and t h e effect of f a t i g u e . c o n t a i n s diagrams and i l l u s t r a t i o n s . t h a t f u t u r e research s h o u l d c o n c e n t r a t e on f u l l - s c a l e tes ts on s t r u c t u r e s and s t r u c t u r a l e l e m e n t s unde r t h e a c t i o n of l o a d s and e x t e r n a l c o n d i t i o n s .

Up

The r e p o r t I t i s p roposed

1 0 7 4 . Hadley, W . , "GAP-GRADED CONCRETE RESEARCH, 'I L o u i s i a n a Tech U n i v e r s i t y , F i n a l R p t . , Feb 1 9 7 7 , p p . 1 2 0 .

I n many p a r t s of L o u i s i a n a t h e s o u r c e s of n a t u r a l l y

Many o c c u r r i n g con t inuous ly -g raded aggregates a re b e i n g d e p l e t e d w i t h o u t any e x p e c t a t i o n o f r e p l a c e m e n t . of t h e ava i lab le m a r g i n a l aggregate s o u r c e s are rejected b e c a u s e o f gap-grading , i . e . , c e r t a i n p a r t i c l e s i z e s are l a c k i n g , o r t h e s izes and q u a n t i t i e s of t h e c o a r s e aggregate do n o t meet t h e e x i s t i n g s p e c i f i c a t i o n r e q u i r e m e n t s . T h i s r e p o r t describes a s t u d y which was unde r t aken t o compare t h e b e h a v i o r o f gap-graded c o n c r e t e s w i t h t h e b e h a v i o r of

33

c o n t i n u o u s l y - g r a d e d c o n c r e t e s t o determire whether o r n o t t h e gap-graded c o n c r e t e m i x t u r e s were comparable t o t h e c o n t i n u o u s l y - g r a d e d c o n c r e t e niixtc.res. The f i v e f a c t o r s i n v e s t i g a t e d i n t h i s s t u d y were c o a r s e aggregate g r a d a t i o n , water-cement r a t . i o , cement c o n t e n t , f i n e aggregate c o n t e n t , and l e n q t h o f c u r i n g . T h e fundamenta l material p r o p e r t i e s evalc.ated w e r e compress ive s t r e n g t h , modulus of e l a s t i c i t y , t e n s i l e s t r e n g t h , P o i s s o n ' s r a t i o , and t e n s i 1 . e s t r a i n , w h i l e t h e p r o p e r t i e s of t h e p l a s t i c c o n c r e t . e mix which were i n v e s t i g a t e d i n c l u d e d slump, d e n s i t y , a i r c o n t e n t , and w o r k a b i l i t y . The r e s u l t s o f an e v a l c . a t i o n o f t h e homogenei ty of t h e v a r i a n c e s ammg and w i t h i n t h e c o n c r e t e s i n d i c a t e t h a t , f o r most fundamen ta l e n g i n e e r i n g p r o p e r t i e s , t h e v a r i a n c e s : were e s s e n t i a l l y t he s a m e f o r a l l gap-graded c o n c r e t e s ; and t h e c o n t i n u o u s l y - g r a d e d c o n c r e t e . .And i n a d d i t i o n , d i rect compar isons of mean p r o p e r t y v a l u e s i n d i c a t e d t h a t t h e gap-graded c o n c r e t e s , i n g e n e r a l , e q u a l l e d o r exceeded t h o s e of t h e c o n t i n u o u s l y - g r a d e d c o n c r e t e s . T h i s c o n c l u s i o n i s g e n e r a l i n s cope s i n c e it i s based upon a wide v a r i e t y o f workable and nonworkable c o n c r e t e mixes .

1075. Hester, W., "HIGH-STRENGTH AIR-ENTRAINED CONCRETE, I'

C o n c r e t e C o n s t r u c t i o n , V o l . 22 , No. 2, Feb 1 9 7 7 , pp . 15.

I n t he d i s c u s s i o n p r e s e n t e d s p e c i f i c and p r a c t i c a l t r e a t m e n t i s g i v e n t o f a c t o r s i m p o r t a n t t.o p r o d u c t i o n a n d u s e of high-strength a i r - e n t r a i n e d concrete, i n c l u d i n g s e l e c t i o n o f mater ia ls , mix p r o p o r t i o n i n g , c o n c r e t e p r o d u c t i o n and c o n t r o l t e s t i . n g .

1076. Howdyshell , P. A., WEVISED OPERATIONS G U I D E FOR A CHEMICAL TECHNIQUE TO DETERMINE WATEF: AND CEMENT CONTENT OF FRESH CONCRETE," C o n s t r Erig R e s Lab Tech R e p M-212, A p r 1977, pp. 35.

T h i s o p e r a t i o n s g u i d e p r o v i d e s infrormation needed t o set up and operate t h e U . S . Army C o n s t r u c t i o n E n g i n e e r i n g Resea rch L a b o r a t o r y / K e l l y V a i . 1 sys t em f ~ i r d e t e r m i n i n g water and cement c o n t e n t of f resh c o n c r e t e . The g u i d e describes t h e s y s t e m ' s capabi l i t i es ( i n c l u d i n g i t s capab i1 i t . y t o estimate p o t e n t i a l c o n c r e t e s t r e n g t h ) , l i m i t a t i o n s , and a c c u r a c y , and d e t a i l s t h e r e q u i r e d equi.pment, r e a g e n t s , and p r o c e d u r e s . A g u i d e for- a n a l y z i n g t e s t r e s u l t s and a d e s c r i p t i o n of a mob i l e m i n i a t u r i z e d f i e l d u n i t are p r e s e n t e d .

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1077. L e i n s , W . and S t i p p , W . , "THE FATIGUE STRENGTH OF CONCRETE, WITH PARTICULAR CONSIDERATION TO THE LOADING RATIOS PREDETERMINED BY TEMPERATURE AND TRAFFIC LOAD I N RESPECT OF CONCRETE ROAD SLABS," Wes tdeu t sche r Verlag P o s t f a c h Opladen West Germany, N2702, 1977, p p . 1 6 4 .

T e s t s w e r e carried o u t on 15/15/70 c m beams t o d e t e r m i n e t he f a t i g u e s t r e n g t h and, i n a d d i t i o n t o t h e s i n u s o i d a l l o a d i n g , work w a s carr ied o u t a l s o f o r repet i t ive l o a d i n g . I n t h i s way a p o s s i b l e sequence o f l o a d i n g by t r a f f i c w a s s i m u l a t e d . I t was found t h a t 18 c m t h i c k s labs are a d e q u a t e on r o a d s c a r r y i n g heavy loads, and t h a t damage i n t h e form o f c r a c k i n g i n t h e s l ab canno t o c c u r . There i s a l s o a s u f f i c i e n t reserve t o a l l o w f o r i n a c c u r a c i e s o f manufac tu re as regards the t h i c k n e s s o f t h e s lab. I n o r d e r t o save b u i l d i n g c o s t s , t he r e s u l t o f these l a b o r a t o r y tes ts s h o u l d be tested on a s t r e t c h of r o a d .

1078. Ma lho t r a , V. M . , "CONTRACT STRENGTH REQUIREMENTS -- CORES VERSUS I N SITU EVALUATION," J o u r n a l o f The American C o n c r e t e I n s t i t u t e , V o l . 7 4 , No. 4, A p r 1 9 7 7 , pp. 163-172.

T h i s paper d i s c u s s e s t he problems a s s o c i a t e d w i t h e v a l u a t i o n of c o r e t e s t data and emphas izes t h e c o n t r a d i c t o r y n a t u r e o f t h e ava i lab le i n f o r m a t i o n . T h e effects of the variables such as l e n g t h - d e p t h r a t i o , embedded r e i n f o r c e m e n t , t y p e of aggregate, s t r e n g t h level o f c o n c r e t e , d i r e c t i o n of d r i l l i n g , and c u r i n g o f c o n c r e t e are d i s c u s s e d . The u n s a t i s f a c t o r y n a t u r e of t he e x i s t i n g a c c e p t a n c e p r o c e d u r e i s b r o u g h t o u t and a case i s made f o r t h e abandonment o f t h e e x i s t i n g a c c e p t a n c e p r o c e d u r e i n f a v o r of a new approach . The suggested p r o c e d u r e c o n s i s t s of t h r e e s t e p s .

1 0 7 9 . M a t s u s h i t a , H . , "FUNDAMENTAL STUDY O F FATIGUE PROPERTIES OF CONCRETE I N THE WATER," P r o c Jpn Congr Mater R e s 2 1 s t , 1977, pp. 166-170.

The p r o p e r t i e s of c o n c r e t e s t r e n g t h i n w a t e r have been made clear o n l y unde r s t a t i c l o a d i n g b u t n o t u n d e r f a t i g u e l o a d i n g . T h i s r e p o r t aims t o examine t h e f a t i g u e s t r e n g t h of c o n c r e t e unde r r e p e a t e d compress ive stress i n t h e water and compare it w i t h t h a t i n a i r . T e s t r e s u l t s g i v e n i n t h i s t e s t show t h a t t h e f a t i g u e s t r e n g t h and l o n g i t u d i n a l compress ive s t r a i n a t f a i l u r e are less t h a n t h o s e i n t h e a i r .

35

1080. Mein inger , R. and Wagner, F . e t a l . , "CONCRETE CORE STRENGTH--THE EFFECT OF LENGTH TO DIAMETER R A T I O , " ASTM J o u r n a l of T e s t i n g and E v a l u a t i o n , V o l . 5, No. 3 , May 1977, pp. 147-153.

The ASTM Method f o r Obtainincr and T e s t i n g D r i l l e d Cores and Sawed Beams of C0ncret.e ( C 42-68) c u r r e n t l y c o n t a i n s l e n g t h t o diameter rati.0 c o r r e c t i o n f a c t o r s f o r soaked c o r e s b u t n o t dr ied c o r e s . However, it i s w i d e l y r e c o g n i z e d t h a t f o r s t r u c t u r e s which w i l l be s u b s t a n t i a l l y d r y i n service dri.ed c o r e s are more a p p r o p r i a t e . I t i s sometimes d i . f f i c - J l t - - b e c a u s e o f c o n s t r a i n t s o f aggretate s i z e , r e i n f o r c i n g bar p l acemen t , and member d imens ions- - to o b t i a n d r i l l e d c o r e s o f the preferred dimens ions , w i t h a l e n g t h t w i c e the diameter. Research per formed i n two l a b o r a t o r i e s i n v o l v i n g t h e d r i l l i n g and t e s t j - n g of a large number o f 4 - in . (102-mm) diameter soaked and dr ied c o r e s w i t h l e n g t h t o diameter r a t i o s , o f 1..0, 1 .25 , 1 .5 , 1 .75 , and 2 .0 , t a k e n from s i x s t r u c t u r a l - s i z e members, i n d i c a t e s t ha t t h e same c o r r e c t l o n f a c t o r s c a n be u s e d f o r b o t h m o i s t u r e c o n d i t i o n s and t h a t t h e f a c t o r s now i n ASTM Method C 42-68 s h o u l d be lowered s l i g h t l y . I n a d d i t i o n , data w e r e gathered on t h e effect o f end p r e p a r a t i o n p r o c e d u r e on c o r e s t r e n g t h . For t h e methods u s e d ( t h r e e capp ing p r o c e d u r e s and g r i n d i n g o f t h e e n d s ) no i m p o r t a n t d i f f e r e n c e s i n measured s t r e n g t h were n o t e d .

1 0 8 1 . Mukherjee, P . , " H I G H EARLY STRENGTH REPAIR CONCRETE FOR CREDIT RIVER STRUCTURE N O . 24203," O n t a r i o M i n i s t r y o f T r a n s p o r t a t i o n C Cornmunic, Can E n g i n e e r i r g Materials Off ice , Mar 1977, pp. 1 2 .

W i t h r e f e r e n c e t o M r . G . P . Wi l son ' s memo dated November 8 t h , 1 9 7 6 and subsequen t d i s c u s s i o n , a serj-es o f l a b o r a t o r y t r i a l tes ts were carried o u t u s i n g d i f f e r e n t cement f a c t o r s and dosages o f set- a c c e l e r a t o r i n o r d e r t o o b t a i n s t r e n g t h o f 1 0 0 0 p s i a t 7 t o 9 h o u r s . I t was a l s o decided t o t r y u s i n g a s u p e r p l a s t i c i z e r t o c u t t h e w a t e r r e q u i r e m e n t of t h e mix and t h u s p r o d u c i n g a high e s r l y s t r e n g t h c o n c r e t e . T h e f o l l o w i n g materials were us,ed ir. a l l t h e e v a l u a t i o n tests: (a) Type-30, High E a r l y S t r e n g t h Cement f rom Canada Lafarge C e m e n t Co. (b) A 3/4 ' i n c h nominal s i z e c r u s h e d d o l o m i t i c l i m e s t o n e from Nelson Q u a r r y (Lab. S t a n d a r d ) w i t h b u l k specif ic g r a v i t y 2 . 6 6 and a b s o r p t i o n 1 . 4 7 p e r c e n t . ( c ) Sand (Lab. S t a n d a r d ) f rom C o n s o l i d a t e d Sand and Gravel Co. L t d . , Guelph, O n t a r i o ( P i c k e r i n g P l a n t ) w i t h bu lk s p e c i f i c gravitly 2 .65 and a b s o r p t i o n 0 . 6 3 p e r c e n t and FM-2.66. (d ) S u f f i c i e n t a i r e n t r a i n i n g admix tu re Darex (Lab. N o . 501-76) t o p r o d u c t 6 p l u s o r minus 1% a i r i n t h e

36

concrete. (e) Darex Set Accelerator of various dosages as described in this report. (f) Superplasticizer 'Melment L-10' was used in some of the test mixes as described in this report. It would appear that: (a) A set accelerating effect and increase in strength are obtained by increasing the dosage of the admixture 'Darex set accelerator'. (b) The desired early strength of 1000 psi can be achieved with a cement factor of 700 lbs. and 1.5 lb. of Darex Set Accelerator per 100 lb. of cement at 7-1/2 hour under laboratory conditions. (c) The 6 hour strength of Melment modified 800 lb. cement factor concrete was significantly lower than that with Darex Accelerator. However considerably higher strength was achieved at 12 hours. (d) The temperature rise characteristics of all test mixes were normal and comparable to the control concrete. On the basis of these observations and test results it is recommended that the concrete with 700 lb. cement factor and 2 lb. of Darex Set Accelerator per 100 lb. of cement be used in order to produce the desired strength under field conditions.

1082. Nawy, E. and Ukadike, M. et al., "HIGH-STRENGTH FIELD POLYMER MODIFIED CONCRETES," ASCE Journal of the Structural Division, Vol. 103, No. ST12, Dec 1977, pp. 2307-2322.

The investigation showed that the rate of increase of slump due to the increase in the polymer/cement ratio (P/C) is less than that due to increasing the water/cement ratio (W/C). It also showed that the P/C optimum ratio within the workable range varies between 0.3 and 0.45 for any practicable W/C ratio below 0.6. It is also demonstrated that liquid polymers of the type used give better mix results when their viscosities are kept low. The polymer modified concrete in this investigation showed a tensile splitting strength increase of 255% and a compressive strength increase of 277% in the respective strengths of the control cylinders. The energy absorption characteristics of the polymer modified concrete (PMC) were almost 3 1/2 times the control specimens making such concretes better suited to such structures as bridge decks and other dynamically loaded structures in addition to their superior serviceability performance in crack and deflection control due to their high tensile and compressive strengths as well as their higher resistance to aggressive environment.

37

1083. Neal, B. and Mason, P., "CONCRETE CREEP STUDY," California Department of Transportation, Final Rpt., Mar 1977, pp. 20.

Creep and shrinkage characteristics were determined for concrete made with aggregates from three different sources. A 1200 psi (8 Mpa) load was applied to creep specimens at three different concrete ages, and maintained for a minimum of 7 7 days. Using best fit curve equations determined from the concrete tests, a prediction of creep and shrinkage for any period up to one year can be made with reasonable accuracy. Although certain properties of aggregate and concrete are indicators of potential creep, more satisfactory results can be obtained by measuring creep and shrinkage as outlined in the report, using concrete made with the ingredients and in the proportions to be used in a specific structure. /Author/ Performed in cooperation with the Department of Transportation, Federal Highway Administration.

1084. Nelson, J. A. and Young, J. F., "ADDITIONS OF COLLOIDAL SILICAS AND SILICATES TO PORTLAND CEMENT PASTES," Cement and Concrete Research, Vol. 7, No. 3,, 1977, pp. 277-282.

Additions of colloidal silicas and silicates were added to portland cement and tricalcium silicate pastes to assess their pozzolanic reactivity. These materials show early reductions of calcium hydroxide consistent with a rapid pozzolanic reaction. High early strengths were generally observed with siliceous additions but later strengths were less affected.

1 0 8 5 . O'Neil, D. J., "POLYMER-CONCRETE COMPOSITES, I' International Journal of Polymeric Materials, Vol. 6,. NO. 1-2, 1977, pp. 73-84.

The need for cost-effective, high-strength, corrosion-resistant materials of construction has l e d to the development of a new class of materials, polymer-concrete composites. Production of such composites may be effected in four ways. This report focuses on polymer-impregnated concrete and polymer-concrete composites and looks at the technical, processing, and economic merits of these materials. A case for increased research is made. It is shown that this new class of structural materials which have strong technical, design, and economic potential for applications in numerous fields, particularly in highway applications.

38

1086. Okada, K. and Kobayashi, K., "EFFECTS OF ADDITION OF GYPSUM AND SUPER WATER-REDUCING AGENT ON MECHANICAL PROPERTIES OF BLAST-FURNACE SLAG CEMENT MORTAR," Proc Jpn Congr Mater Res 21st, Tokyo, Japan, 1977, pp. 209- 213.

The ultra high strength concrete has been produced quite easily through the routine procedures only by using the super water-reducing agents. The cement content, however, is to be considerably increased to obtain such a high strength concrete. Then, the attempt that a part of unit cement content is replaced by blast-furnace slag is not only useful from the economical viewpoint, but also effective for improving durability of concrete against sulfate attacks. In this study, effectiveness of gypsum addition on the improvement in early strength and the actions of gypsum on strength development with age, drying shrinkage and time of setting, are examined in detail using the mortar specimens. 4 refs.

1087. Ozyildirim, H., "ALTERNATIVES TO TYPE I1 CEMENT, PART I--PRELIMINARY LABORATORY STUDIES," Virginia Highway & Transportation Research Council, Intrm Rpt., Feb 1977, pp. 31.

In this study concrete mixtures incorporating fly ash are being investigated as possible alternatives to mixtures utilizing Type I1 cements. The mixture characteristics being considered are strength, resistance to freezing and thawing and sulfates, heat of hydration, and volume stability. Control mixtures are made of Type I, 11, and I11 cements. In the experimental mixtures, Type IP cement--a blend of ordinary cement and fly ash--and Type I cement with fly ash as an admixture are being used. This report gives the results of initial tests for compressive and flexural strengths, resistance to rapid freezing and thawing, early volume change, time of set, and heat of hydration. Long-term strength data and information on sulfate and scaling resistance and drying shrinkage will be presented in the final report, with recommendations from the study.

1088. Pandit, G. and Tanwani, N., "A NEW DIRECT TENSION TEST FOR CONCRETE," Indian Concrete Journal, Vol. 51, No. 8, Aug 1977, pp. 244-246.

A new test for the tensile strength of concrete is proposed in this paper. In addition to satisfying the usual requirements of simplicity, accuracy and reproducibility, the uniformity of stress on the test section is also ensured. equipment which can easily be fabricated and a

The test requires simple

39

compress ion t e s t i n g machine of r e l a t i v e l y small c a p a c i t y . I t i s believed t h a t the new tes t d e t e r m i n e s t h e t r u e u n i a x i a l t e n s i l e s t r e n g t h of c o n c r e t e bec,ause it m e e t s t h e r e q u i r e m e n t s o f a n .ideal t e n s i o n t e s t t o t h e maximum p o s s i b l e e x t e n t .

REINFORCEMENT, 'I C o n s t r u c t i o n ( F r a n c e ) , V o l . 32, No. I., J a n 1977, pp. 28-32.

1089. Puech, M . , "REINFORCED CONCRETE .- PROTECTION OF TH:E

T h i s a r t i c l e s t u d i e s t he i n f l . J e n c e of z i n c and t h e s a l t s it c o n t a i n s on c o n c r e t e as regards a d h e s i o n . It. describes l a b o r a t o r y tests on new steel , o x i d i z e d steel and z i n c t reated steel , t o g e t h e r w i t h commercial. a p p l i c a t i o n s i n F rance , t h e Nethlsr lands, t h e U n i t e d S t a t e s , Japan , e tc . I t deals w i t n t h e r e a c t i o n of z i n c w i t h cement and w i t h the consequlence on t h e b e h a v i o u r o f s teel w i r e s s u b j e c t e d t o high t e n s i l e p r e s t r e s s i n g f o r c e s . Mention i s made of f u l l - s c a l e tes ts on prestressed beams. The r i s k o f b r i t t l e n e s s i n high- s t r e n g t h steel due t o t h e p r e s e n c e of hydrogen released t h r o u g h t h e r e a c t i o n between z i n c and cement , c a n be a v o i d e d i f t h e a p p r o p r i a t e t y p e of cement i s used o r by a d d i n g p o t a s s i u m b i c h r o m a t e t o a r t i f i c i a l p o r t l a n d cement .

1 0 9 0 . Ramakrishnan, V., "SIGNIFICANT PHYSICAL AND MECHANICAL PROPERTIES OF GAP-GRADED CONCRETE, I n d i a n C o n c r e t e J o u r n a l , V o l . 51, No. 5, May 1977, pp. 142-158.

The results of an extensive investigation involving t h r e e hundred and s e v e n t y - f i v e mixes of gap-graded and c o n t i n u o u s l y graded c o n c r e t e mixes i n t he s t r e n g t h r a n g e o f 210 kg/cm2 t o 5 3 0 kg/cm2 ( 3 0 0 0 l b / i n 2 t o 7500 l b / i n 2 ) w i t h f o u r d i f f e r e n t maximum s i z e s o f c o a r s e aggregate are p r e s e n t e d i n t h i s p a p e r . The water- cement r a t i o s by weight of t h e mixes varied from 0.3!5 t o 0 .65 , and the aggregate-cement r a t i o s by weight from 2 . 0 t o 1 0 . 0 . Wi th in t h e premises o f t h i s s tudy . , it i s conc luded t h a t gap-graded c o n c r e t e , t hough o f a r e l a t i v e l y s t i f f e r and drier mix, can be placed a n d f i n i s h e d w i t h o u t undue e f f o r t f o r a l l c o n s t r u c t i o n work where in c o n t i n u o u s l y g r a d e d c o n c r e t e has been c u s t o m a r i l y u s e d h e r e t o f o r e . A c o n s i d e r a b l e s a v i n g .in cement c o n t e n t and n o t a b l e improvements i n p h y s i c a l and mechan ica l p r o p e r t i e s are t h e r e a l i s t . i c a l l y a c h i e v a b l e a d v a n t a g e s t h r o u g h t h e u s e o f gap-graded c o n c r e t e f o r a l l p u r p o s e s where c o n v e n t i o n a l c o n c r e t e i s b e i n g u s e d .

4 0

1091. Rosenberg, A. and Gaidis, J. et al., "CORROSION INHIBITOR FORMULATED WITH CALCIUM NITRITE FOR USE IN REINFORCED CONCRETE," ASTM Special Technical Publications, N629, 1977, pp. 89-99.

The scarcity of good aggregate in Japan led to an investigation of the use of a corrosion inhibitor for reinforced concrete. The results showed that the introduction of calcium nitrite diminishes the corrosion of reinforcing steel in the presence of admixed sodium chloride. specimens partially immersed in saturated sodium chloride solution indicate that admixed calcium nitrite can prevent the open circuit potential of reinforcing steel from entering the active region. Calcium nitrite was found to enhance the strength of concrete. The use of a calcium-based admixture is expected to sidestep the issue of alkali-aggregate reactions and subsequent deterioration of concrete. Presented at the 79th ASTM Annual Meeting, Chicago, Illinois, June 27-July 2, 1976.

1092. Rosner, J., "LOCAL FLY ASH USAGE IN PORTLAND CEMENT CONCRETE," Proceedings of 14th Paving Conference, 1977, pp. 144-166.

Long-term tests on large

An analysis of data, accumulated during a laboratory test program, indicates that waste boiler ash (fly ash) produced at the Four Corners Generating Station, Fruitland, New Mexico can be used advantageously as an admixture in portland cement concrete. Compressive and flexural strength data have been obtained over a ninety day curing period. These data are utilized in the development of a mix design procedure aimed at optimizing the proportions of fly ash and portland cement relative to economic factors.

1093. Schminke, P., "FLOWED CONCRETE PRACTICE IN WEST ~-~

GERMANY," Zement und Beton, Vol. 22, No. 2, 1977, pp. 44-47.

To an increasing degree concrete pavements in the federal German republic are being constructed with early high-strength flowed concrete. By this means of construction, concrete slabs without heavy surface stresses can be installed with minimum dead time. Flowed concrete is also being employed in the widening of concrete slabs to receive the 4/0-traffic without renewal. Four construction methods for the renewal of concrete motorway foundations are described. /TRRL/

41

1094. Tepfers, R. and Friden, C. et al., "STUDY OF THE APPLICABILITY TO THE FATIGUE OF )CONCRETE OF THE PALMGREN-MINER PARTIAL DAMAGE HYPOTHESIS," Magazine of Concrete Research, Vol. 29, No. 100, 1977, pp. 123- 130.

This investigation provides some information concerning the applicability to the fatigue of concrete of the Palmgren-Miner partial damage hypothesis. The results do not contradict this hypothesis. The tests were performed on small concrete cylinders at high load-alternation frequencies. The results may be used to determine the effects of waves on offshore structures.

1095. Torrent, R., "A GENERAL RELATION BETWEEN TENSILE STRENGTH AND SPECIMEN GEOMETRY FOR CONCRETE-LIKE MATERIALS," Materiaux et Constructiones, Essais et Recherches, N58, Jul 1977, pp. 187-196.

In the course of this study, a general relation between the different tensile strengths of concrete- like materials was established, which is based on the 'weakest link' concept. Seven mortar mixtures were: tested under nine different conditions of tensile tests: bending test with axial load and with load applied on the middle third of the specimen, splitting tensile tests on samples of different sizes and direct tensile tests. In each case, the volume of material with a tensile stress more than 0.95 of the maximum stress within the sample (maximum stress volume) was evaluated. A decreasing linear relation between the ultimate tensile strength logarithm and the maximum stress volume logarithm was found with a gradient that can be regarded as constant for the seven mixtures: tested.

1096. Waagaard, K., "FATIGUE OF OFFSHCRE CONCRETE STRUCTURES-DESIGN AND EXPERIMENTAL INVESTIGATIONS,'' Proceedings - Offshore Technology Conference, May 2-5, 1977, pp. 10.

Results from pilot testing of reinforced concrete specimens exposed to repeated reversible loading are presented. The main parameters investigated are the effects of cracking, water pressure, frequency of testing and the stress level in the specimen. The results indicate that the fatigue strength of concrete is considerably reduced when exposed to a marine environment and repeated reversible stresses.

42

I

1097. Wang, P. and Shah, S. et al., "COMPLETE STRESS-STRAIN CURVE OF CONCRETE AND ITS EFFECT ON DUCTILITY OF REINFORCED CONCRETE MEMBERS," Illinois University, Chicago; Department of Materials Engineering, Final Report, Oct 1977, pp. 276.

A relatively simple experimental technique was developed to obtain the entire stress-strain curve of concrete. The experimental curves were obtained for normal weight concrete of compressive strengths up to 11,000 psi and lightweight concrete of strengths up to 8,000 psi. An analytic expression for the stress- strain curve is proposed. The expression has four constants which depend on the properties of both the ascending and the descending portions of the curve. A computerized nonlinear analysis program was developed to predict the structural response of reinforced concrete on the ultimate strength parameters of the concrete compressive zone.

43

1978

1098. Bazant, 2. P. and Panula, L., "PRACTICAL PREDICTION OF

CREEP," Materiaux et Constructions, Materials and Structures, V o l . 11, No. 66, 1978, pp. 415-434.

TIME-DEPENDENT DEFORMATIONS OF CONCRETE -- 3 . DRYING

The practical model for predicting creep and shrinkage developed is extended to creep at dryin<[ environment and constant temperature. The increase of creep due to drying is related to shrinkage. Formulas for determining material parameters from concrete strength and mix composition are presented and verified by extensive comparisors with test data from the literature.

1099. Bazant, 2. P. and Panula, L., "PRACTICAL PREDICTION OF TIME-DEPENDENT DEFORMATIONS OF CONCRETE -- 1. SHRINKAGE, 'I Materiaux et Constructions, Materials and Structures, V o l . 11, No. 65, 197'8, pp. 307-328.

Proposed is a practical model for predicting creep and shrinkage of concrete from the composition of concrete mix, strength, age at loading, conditions of environment, size and shape, etc:. The main features are:double power law for basic creep, square-root hyperbolic law for shrinkage, diffusion-type size dependence of humidity effects, additive drying creep term related to shrinkage, and &ctivation energy treatment of thermal effects. Optimization techniques are used to fit numerous test data available in the literature.

1100. Berry, E. E. and Malhotra, V. M., "FLY ASH FOR USE IN CONCRETE -- 2. A CRITICAL REVIEW OF THE EFFECTS OF FLY ASH ON THE PROPERTIES OF CONCRETE," CANMET Report (Canada Centre for Mineral and Elnergy Technology), No. 78-16, 1978, pp. 59.

Within limits, the applicaticln of appropriate proportioning methods and the use of a high quality fly ash permit the economic manufacture of concrete of adequate early strength. When properly proportioned and placed, fly ash concrete generally shows improved workability, pumpability, cohesiveness, finish, ultimate strength, and durabi1it.y. If has been found that fly ash is of particular value in high-strength concrete. Its use has often been shown to improve the performance of concretes exposed to sulphate attack or to deterioration caused by alkali-aggregate interactions. However, research on fly ash concrete has still been inadequate.

44

1101. Bishara, A. and Rose, J. et al., "SHRINKAGE AND CREEP CHARACTERISTICS OF LATEX-MODIFIED CONCRETE," Journal of American Concrete Institute, Vol. 75, No. 5, May 1978, pp. 204-208.

An experimental investigation was conducted to study creep and shrinkage characteristics of latex- modified mortar (LMM) and concrete (LMC) used for bridge deck overlays. prisms of latex-modified mortar and eleven prisms of latex-modified concrete prepared to be tested for almost 8 months. Empirical equations for predicting shrinkage strains of LMM and LMC show that shrinkage of LMM is almost double that of LMC and air-entrained normal weight concrete ( A E C ) . Empirical equations developed for predicting creep of LMM give values of the same order of magnitude as those of AEC.

The test program included eight

1102. Bowery, F. and Higgins, F., "THE EVALUATION OF ALTERNATE CAPPING PROCEDURES FOR CONCRETE 28 DAY QUALITY ASSURANCE SPECIMENS," Final Report, Woodward- Clyde Consultants; Materials Res & Development Div, Rockville, Maryland, Charleston, West Virginia, Jan 1978, pp. 60.

This study is based on a designed experiment to determine the feasibility of using pressure pads in the testing of 28 day concrete test cylinders. The scope of the investigation includes four types of pressure pads (Celotex, Upson Board, Rubber Belt and Steel End Caps with Rubber inserts) as well as the Sulphur Mortar Caps which are intended as the reference standard. The design required 1 5 batches of concrete to fabricate ten 6 inch x 12 inch concrete cylinder specimens. All batches were made with one aggregate of one gradation, one brand of cement, and cement constants of 5.0, 6.0 and 7.25 bags/cubic yard. Test results indicate that the average concrete compressive strengths are less when tested using either Celotex, Upson Board or Rubber Belt pressure pads than when the specimens are tested with Sulphur Mortar caps. However, the Sulphur Mortar and the Steel End Caps with inserts have about the same strengths. The within-test variations are good to excellent for the Steel End Caps but the other non-standard caps generally show a poor within-test variation. The unit material cost per test for the Steel End Caps with rubber inserts is about the same as the standard and considerably less when equipment purchase price, installation costs, personnel safety and time, and energy costs are considered. The Steel End Caps with rubber inserts are an acceptable alternate for the standard method of capping 28 day concrete test specimens.

45

1103. Brooks, J. J. and Neville, A . M., "PREDICTING LONG --- TERM CREEP AND SHRINKAGE FROM SHORT-TERM TESTS," Magazine of Concrete Research, V o l . 30, No. 103, 1970, pp. 51-61.

On the basis of experimental results from creep arid shrinkage tests lasting five years and data from other investigators, it is proposed that long-term deformations can be predicted within reasonable limits of accuracy from values measured at 28 days. The expressions given are sensibly independent of a wisde range of the independent variables which affect creep and shrinkage of concrete.

1104. Derucher, K. N., "FAILURE MECHANISM OF CONCRETE," ASTM Special Technical Publication, 1978, pp. 664-679.

The major objective of this investigation was t3 observe directly the formation o:r propagation of microcracks in concrete by use of the scanning electron microscope both before and after application of compressive stress fields. Concrete, under compression, fails when macrocracks have propagated to the extent that the concrete will not support the applied loads. Many investigators have implied that the failure mechanism of concrete is related to internal microcracking. However, due to the limitations in the techniques employed, the detection of microcracks was somewhat uncertain. Microcracks were found to exist in concrete prior to application of compressive stress fields in the form of shrink'age microcracks (initial bond microcracks). As the compressive stress field is increased, these microcracks widen and propagate until failure occurs.

1105. Dmitriev, A. and Vlasova, M. et al,, "MANUFACTURING PROCESS FOR OBTAINING HIGH-STRENGTH RAPID-HARDENING CEMENT, I' Zement-Kalk-Gips, N7, Jill 1978, pp. 3 3 8 - 3 3 9 .

In order to improve the hydraulic characteristics of cement and to produce rapid-hardening cement, organizations in the USSR carried out investigations which showed that the clinker's baking conditions had the greatest influence on the hydraulic properties of cement. The composition and fineness of raw meal, the cooling of the clinker and the fineness of the cement are other parameters affecting the hydraulic properties. If the raw material available has A silicate ingredient containing ferrous oxide, rapid baking of the clinker in a short oven with a short flame is recommended. In a long oven with an extension clinkerization zone, good hydraulic quality

46

I

clinker is obtained only if the alkali content exceeds 0,7%. Tests 700 and 850 kp/sq.cm.

1106. "DYNAMIC TEST ON MODEL BRIDGE DECK," Rail International, N5, May 1978, pp. 361-362.

This article describes some of the findings of report D123/RP6 published by ORE, Utrecht. A model bridge deck with a span of 3.6 M was subjected to tests designed to check whether ultimate strength would be affected by the cracks expected to develop during service. After approximately 200000 load cycles, measurements were made of maximum deflection, strain in upper and lower edges of the girders and the upper surface of the concrete. Based on the measured material characteristics, calculation using plastic theory or elastoplastic theory gave lower predictions of failure moment. service loading tended to stabilize.

Effects of cracking under repeated

1107. Gauert, C. E., "EXPERIMENTS AND EXPERIENCES RELATING TO HIGH EARLY STRENGTH CONCRETE WITH SUPERPLASTICISER," Replacement of Pavements, Beton, Herstellung, Verwendung, Vol. 28, No. 9, 1978, pp. 326-328.

The author reports that a flowing concrete with high early strength was developed as construction material which could be used without the help of machinery even under difficult placing conditions, for instance at intersections, parking spaces and junctions. In German with English abstract.

1108. Hajek, J., "INFLUENCE OF STRAIN GRADIENT ON CONCRETE TENSILE STRENGTH, Stavebnicky Casopis, Vol. 26, No. 1, 1978, pp. 20-27.

The paper deals with the determination of the cracking limit of concrete elements with regard to the influence of strain gradient on concrete tensile strength. The tests on two series of plain and prestressed concrete elements have shown that with the increase of strain gradient the cracking limit is relatively increasing, too. The value of the strain gradient can be influenced by prestressing.

CONSTRUCTION," Strassen und Tiefbau, Vol. 32, No. 2, Feb 1978, pp. 16-17.

1109. Jacobs, J., "RECENT DEVELOPMENTS IN CONCRETE

The supplementary technical specifications and regulations for the construction of concrete pavements, which are shortly to be published, contain fresh information, some of which is briefly covered

47

here. Some 5 0 0 0 0 0 cu M of e a r l y h i g h s t r e n g t h c o n c r e t e made w i t h p l a s t i c i z e r s and used f o r t r a f f i cked s u r f a c e s , no t covered by D I N 1045 ( c o n c r e t e ) , has a l r e a d y been produced accord ing t o the r e l e v a n t s p e c i f i c a t i o n s . A s slump has g e n e r a l l y been less t h a n 50 crns, t h i s i s no t t r e a t e d as flow c o n c r e t e . F u r t h e r measures are concerned w i t h c o n c r e t e s a f e t y f ences , which are used abroad i n s t e a d of steel s a f e t y f e n c e s . These are 8 0 o r 1 3 0 crns h igh , made o f i n - s i t u c o n c r e t e o r made up i n 1 M long p r e c a s t u n i t s and erected u s i n g a mobile c rane . They form bar r ie rs t o p reven t vehicles c r o s s i n g t h e c e n t r a l r e s e r v e o r t h e edge boundar ies and guide v e h i c l e s back onto t h e car r iageway. They a l s o can be e a s i l y r e p a i r e d and p reven t g la re .

1 1 1 0 . Kaar, P . and Hanson, N . e t a l . , "STRESS-STRAIN CHARACTERISTICS OF HIGH-STRENGTH CONCRETE," P o r t l a n d Cement Assoc ia t ion , 1978 , pp. 1 0 .

T h e s t r e s s - s t r a i n r e l a t i o n s h i p and f l e x u r a l stress d i s t r i b u t i o n f o r u l t i m a t e s t r e n g t h d e s i g n has been w e l l established from previous work. Genera l ly , normal-weight c o n c r e t e s w i t h s t r e n g t h s ranging from 1 , 0 0 0 p s i t o 7 , 5 0 0 ps i ( 6 . 9 MPa t o 51.7 MPa) have been i n v e s t i g a t e d . I n t h e p r e s e n t s tudy , f l e x u r a l c h a r a c t e r i s t i c s of h igh - s t r eng th c o n c r e t e s were o b t a i n e d from a series o f specimens tested a t t he P o r t l a n d Cement Assoc ia t ion l a b o r a t o r i e s . The tes t series inc luded c o n c r e t e s t r e n g t h s ranging from 6 , 5 0 0 p s i t o 14,850 psi (44.8 MPa to 102.4 M P a ) for normal- weight c o n c r e t e s and from 3 , 5 6 0 p s i t o 1 2 , 4 9 0 p s i (24.5 MPa t o 86.1 MPa) f o r l i g h t w e i g h t c o n c r e t e s . Concre tes c o n t a i n i n g three d i f f e r e n t normal-weight aggrega te s and two d i f f e r e n t l i g h t - weight aggrega te s were inc luded i n t he s tudy . S t r e s s - s t r a i n cu rves , f l e x u r a l c o n s t a n t s , and moduli of e l a s t i c i t y are r e p o r t e d f o r the complete range of c o n c r e t e s t r e n g t h s . R e s u l t s of t h i s i n v e s t i g a t i o n have been combined w i t h t h o s e of o t h e r i n v e s t i g a t o r s . The d a t a a r e compared w i t h t h e l a t e s t A C I Bui ld ing Code r e v i s i o n s p e r t a i n i n g t o f l e x u r a l c o n s t a n t s f o r s t r e n g t h d e s i g n .

1111. Kaneuji , M . , "CORRELATION BETWEEN PORE S I Z E DISTRIBUTION AND FREEZE THAW DURABILITY O F COARSE AGGREGATE I N CONCRETE," I n t e r i m Report , Ind iana S t a t e Highway Comm, West L a f a y e t t e , Ind iana , Aug 1 9 7 8 , pp. 1 4 2 .

S t u d i e s have shown t h a t t h e pore c h a r a c t e r i s t i c s of c o a r s e aggregates have an impor tan t r o l e i n t he freeze- thaw d u r a b i l i t y of c o n c r e t e . T h i s s t udy was des igned t o seek a c o r r e l a t i o n between p o r e - s i z e d i s t r i b u t i o n of an aggregate measured by mercury

4 8

i n t r u s i o n and the f r eeze - thaw d u r a b i l i t y o f c o n c r e t e made w i t h the aggregate. F o u r t e e n aggregates w i t h a v a r i e t y of p o r e - s i z e d i s t r i b u t i o n s were s t u d i e d . The rapid f r e e z e - t h a w (ASTM C 666A) and a m o d i f i e d c r i t i c a l d i l a t i o n t e s t were conduc ted . and t h e PCA a b s o r p t i o n - a d s o r p t i o n tes ts were a l s o conduc ted . A good c o r r e l a t i o n between the p o r e - s i z e d i s t r i b u t i o n o f a n aggregate and i t s n o r m a l i z e d d u r a b i l i t y f a c t o r o b t a i n e d from the rapid f r eeze - thaw test w a s found. The e q u a t i o n relates t h e e x p e c t e d d u r a b i l i t y f a c t o r t o t h e p o r e volume and t h e median p o r e s i z e . make f o r p o o r d u r a b i l i t y . Aggregates from pavement c o n c r e t e w i t h v a r y i n g degrees o f D-Cracking were r u n and, on t h e basis of t h e r e s u l t s , t e n t a t i v e e x p e c t e d d u r a b i l i t y f a c t o r s were set up t o d i s t i n g u i s h between p o t e n t i a l l y good and p o t e n t i a l l y poor aggregates. A b s o r p t i o n v a l u e s and the a b s o r p t i o n - a d s o r p t i o n tes t were n o t as good i n d i c a t o r s of pe r fo rmance .

The a b s o r p t i o n

Larger p o r e volumes and smaller p o r e s i z e s

1112. L e e , D . and Klaiber, F . e t a l . , "FATIGUE BEHAVIOR OF AIR-ENTRAINED CONCRETE,'* T r a n s p o r t a t i o n Resea rch Record, N671, 1978, pp. 20-23.

Almost a l l r ig id-pavement d e s i g n p r o c e d u r e s u s e d t o d a y i n c l u d e c o n s i d e r a t i o n o f t h e f a t i g u e s t r e n g t h of c o n c r e t e , b u t t he f a t i g u e c u r v e s u s e d do n o t t ake i n t o a c c o u n t t h e effects o f e n t r a i n e d a i r . T h i s paper p r e s e n t s t h e r e s u l t s o f a s t u d y of t h e f l e x u r a l f a t i g u e s t r e n g t h o f c o n c r e t e i n which the o n l y var iable w a s t he p e r c e n t a g e of e n t r a i n e d a i r . A l l o t h e r variables (e.g. , t y p e of cement, water-cement r a t i o , and t y p e o f aggregate) w e r e held c o n s t a n t . F i v e sets o f c o n c r e t e beams t h a t had a i r c o n t e n t s t h a t varied from 2 .8 p e r c e n t ( n a t u r a l a i r , i . e . , no a i r - e n t r a i n i n g a g e n t added) t o 11.3 p e r c e n t b u t a c o n s t a n t water -centment r a t i o of 0 . 4 1 were tested under one- third-point l o a d i n g . The stresses were varied from z e r o t o a p r e d e t e r m i n e d maximum t h a t c o r r e s p o n d e d t o a p e r c e n t a g e o f t h e modulus-of - rupture s t r e n g t h of t h e g i v e n beam. Wi th in each a i r - c o n t e n t group, a minimum of f ive beams were tested a t e a c h o f f o u r stress levels: 60, 70, 80, and 90 p e r c e n t o f modulus of r u p t u r e . A t o t a l o f 112 specimens of 1 5 . 2 - 15.2-cm ( 6 x 6 - i n . ) c r o s s s e c t i o n were tes ted. The r e s u l t s are p r e s e n t e d as f a t i g u e c u r v e s t h a t re la te t h e r a t i o f l e x u r a l stress; modulus of r u p t u r e t o t h e number of a l l o w a b l e l o a d r e p e t i t i o n s and show a decrease i n f a t i g u e s t r e n g t h as a i r c o n t e n t i n c r e a s e s .

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1113. Losberg, A,, "PAVEMENTS AND SLABS ON GRADE WITH STRUCTURALLY ACTIVE REINFORCEMENT," American Concrete Institute, Journal of, Vol. 75 No. 12, Dec 1978, pp. 647-657.

This paper gives the theoretical analyses for the various load cases, and summarizes the results in simple design diagrams. shows the reliability of these results. Also the influence of temperature and shrinkage effects are treated and simple formulas are given for the joint design. A design example shows the method of calculation and the use of the diagrams.

A review of tests carried out

1114. Ma, J. and McCullough, B., "ANALYSIS OF LOAD, TEMPERATURE, AND SHRINKAGE EFFECT ON CONTINUOUSLY REINFORCED CONCRETE PAVEMENT," Transportation Research Record, N671, 1978, pp. 29-39.

load, temperature, and shrinkage effects on a continuously reinforced concrete pavement is presented. pavements is the result of the restraint of the pavement slab to dimensional changes induced by internal and external forces. The formation of transverse cracks can be attributed to two distinct and basic mechanisms: (a) the internal forces associated with decrease in temperature and drying shrinkage, and (b) the externally induced stress caused by wheel loads, The CRCP-2 computer program combines the stress caused by in.terna1 forces and the flexural stress under wheel load. The internal stress is determined by using the one-dimensional axial structural model that simulates the mechanistic behavior of the composite slab. The wheel-load stress can be determined either externally by slab-analysis methods or internally within the program by using the Westergaard equation for interior loading and inputting the magnitude of the wheel load, the wheel- base radius, and the modulus of subgrade. A series of problems is solved by using the CRCP-2 computer program. The results show that external load, when combined with internal forces, induces more cracks to develop and that both steel stress and crack width decrease as crack spacing decreases. The function of steel reinforcement in continuously reinforced concrete pavement is to control crack spacing; higher steel percentage means higher restraint to the concrete, which causes more crac:ks to develop. The function of the slab thickness i.s to resist the tensile stress under wheel load; thicker slab usually means wider crack spacing. It is concluded that the

A computer program--CRCP-2--for the analysis of

The transverse cracking of continuous

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i n c l u s i o n of both wheel load and i n t e r n a l f o r c e s makes it p o s s i b l e t o p r e d i c t more r e a l i s t i c a l l y and more accu ra t e ly t h e a c t u a l crack spacing, t h e crack width, and t h e steel stress i n t h e pavement s y s t e m and t h e s l a b th i ckness and t h e steel percentage must be proper ly designed t o ( a ) withstand t h e i n t e r n a l f o r c e s developed from restrained-pavement volume changes, (b) keep cracks t i g h t l y c losed, and (c) avoid excess ive c racking . This paper appeared i n TRB Record 671, Analysis of Pavement Sys tems.

1115. Malhorta, V . , "RECYCLED CONCRETE--A NEW AGGREGATE, Canadian Journal of C i v i l Engineering, Vol. 5, No. 1, Mar 1978, pp. 42-52.

Large urban c e n t r e s i n Canada and t h e United S t a t e s are f i n d i n g it inc reas ing ly d i f f i c u l t t o l o c a t e and develop n a t u r a l aggregate sources f o r use i n conc re t e . T h e s tudy repor ted he re in was t h e r e f o r e undertaken t o i n v e s t i g a t e t h e p o s s i b i l i t y of producing aggregates from discarded concre te con t ro l tes t cy l inde r s , normally s e n t t o waste dumps a f t e r t e s t i n g . A series of 2.2-cu f t (0 .062-cu m ) concre te mixes were made covering t h e low, medium and high s t r e n g t h l e v e l s . Two sets of mixes were made a t each s t r e n g t h l e v e l , one set cons i s t ed of a con t ro l mix and a mix made using coarse aggregate prepared from recycled concre te and r e fe rence f i n e aggregate; the second set cons i s t ed o f a c o n t r o l mix and a mix using f i n e aggregate prepared from recycled concre te and a r e fe rence coarse aggregate . Cylinder and prism specimens were c a s t from each mix t o determine mechanical p r o p e r t i e s of conc re t e s a t var ious ages and t o study t h e d u r a b i l i t y of concre te a f t e r exposure t o freeze-thaw cyc l ing . The ana lyses of t h e tes t r e s u l t s have shown t h a t s a t i s f a c t o r y concre te can be made w i t h aggregates prepared from recycled concre te . A t lower water- cement r a t i o s , s t r e n g t h s of t h e two types of concre te a r e comparable. The d u r a b i l i t y of concre te made w i t h aggregates prepared from recycled concre te i s comparable t o t he d u r a b i l i t y of concre te made w i t h r e f e rence aggrega tes .

1 1 1 6 . Malhotra, V. M . , "SUPERPLASTICIZERS I N CONCRETE, 'I Modern Concrete, V o l . 4 1 , No. 12 , 1 9 7 8 , pp. 38-43.

T h i s paper r e p o r t s the r e s u l t s of a l abora to ry i n v e s t i g a t i o n t o determine t h e performance of s u p e r p l a s t i c i z e r s i n high-strength concre te . A series of concre te mixes were made a t a water cement r a t i o of 0 . 4 2 w i t h a slump of 5 0 mm. Various dosages of t h e s u p e r p l a s t i c i z e r s , Melment L10 , Mighty 1 5 0 and Mulcoplast CF, w e r e added t o t h e mixe r a f t e r t h e completion of i n i t i a l mixing. Increases i n slumps and

51

their subsequent loss with time were measured. Test cylinders and prisms were cast for strength and durability studies.

1117. Mangat, P. S. and Evans, D. A., "INFLUENCE OF POLMER ADMISTURES ON THE STRENGTH, DEFORMATION AND FRACTURE OF HIGH STRENGTH CONCRETES," Int Congr on Polym in Concr, 2nd, Univ of Tex, Austin, Oct 25-27 1978, pp. 67-87.

The use of polymer emulsions to produce very low water-cement ratio concretes has been investigated and the strength, deformation and fracture behavior of the material studied. Four types of polymers were used --- acrylic, modified acrylic, styrene acrylic and styrene butadiene. The investigation was carried out on ordinary portland cement mixes, with proportions of 1:l. 5:2. 5, 1:2:2 and 1:2. 5:l. 5 (by weight) and a water-cement ratio of 0. 3 was maintained. Three types of curing regimes were adopted -- dry, wet/dry and wet.

1118. Mehta, P. K. and Pirtz, D., "USE OF RICE HULL ASH TO REDUCE TEMPERATURE IN HIGH-STRENGTH MASS CONCRETE.," Journal of The American Concrete Institute, Vol. 75, NO. 2, 1978, pp. 60-63.

It is shown that a highly reactive silica ash produced by incineration of rice hulls can be successfully used in mass concrete applications requiring high strengths without excessive rise in adiabatic temperature. In a concrete mixture when 30 percent rise hull ash by weight of the total cementing material was present, the 7-day and the 28-day compressive strengths were higher and the adiabatic temperature rise was 10 C lower than the control concrete.

1119. Porter, L., "A 25-YEAR EVALUATION OF CONCRETE CONTAINING REACTIVE KANSAS-NEBRASKA AGGREGATES," Bureau of Reclamation Engineering and Research Center Denver Colorado, Oct 1978, pp. 89.

Durable concretes made with reactive aggregates require compatible ingredients, properly blended and cured. Initially, accelerated tests were used to evaluate materials; however, seldom is the opportunizy available, as it is here, to reassess the original concretes after many years of weathering. The concreie slabs, exposed out-of-doors for 25 years, which were inspected for soundness and measured initially, have now been inspected to determine dimensional stability. Concretes contained aggregates which had varying potential for reacting with alkalis in the cements.

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Methods tried for alleviating effects of reactive expansion included use of various additive aggregates, pozzolans, and portland cements, both with and without entrained air. Fundamental conclusions from initial accelerated tests were confirmed. These require the use of cements having very low alkali content or 45 percent crushed limestone additive with the reactive aggregate. However, use of palliatives such as pozzolan and granite or crushed quartzite aggregate additives delay, but do not prevent, reactive expansion and cracking.

1120. Schubenz, D. and Pedersen, S., "USE OF HIGH EARLY STRENGTH CONCRETE MADE WITH SUPERPLASTICIZERS FOR ROAD PAVEMENTS,'' Nordisk Betong, Vol. 22 No. 1, 1978, pp. 11-16.

By adding super-plasticizer to concrete it is now possible to produce concrete characterized by a low water-cement ratio (0,38 to 0,40), good workability (slump 15 to 20 cm) and early strength gain (20 n/sq mm after 24 hours). Accordingly, concrete is to be regarded as a practicable alternative to flexible pavements.

1121. Sommer, H., "ADVICE ON THE PRODUCTION OF EARLY HIGH STRENGTH ROAD CONCRETE WITH PLASTICIZERS," Forschungsinstitut Des Vereins Der Oesterreichisch Reisnerstrasse 53 Vienna Austria, Feb 1978, pp. 12.

Within the framework of the relevant Austrian specifications, the following points are dealt with: requirements, (skidding resistance, bond of fresh concrete, flow, early strength, frost-deicing salt resistance), concrete mix design, construction materials (sand, chippings, cement, additives) , suitability tests (mixer, mixing, fresh concrete tests, t o t a l sand con ten t , f i n e sand con ten t , q u a n t i t y of plasticizer, hardened concrete tests, concrete mix design), strength tests, hardening tests, production.

1122. Tasuji, M. E. and Slate, F. 0. et al., "STRESS-STRAIN RESPONSE AND FRACTURE OF CONCRETE IN BIAXIAL LOADING," Journal of The American Concrete Institute, Vo1.75, No.7, Jul 1978, pp. 306-312.

Thin plain concrete plates subject to biaxial loading were studied experimentally. All combinations of compressive and tensile loadings were included. Deformational characteristics, fracture mechanism, and strength were observed. A general stress-strain relationship for concrete in biaxial loading is proposed. A simple biaxial strength criterion is recommended for practical application.

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1123 . Wang, P . and Shah, S . e t a l . , "STRESS-STRAIN CURVES C,F NORMAL AND LIGHTWEIGHT CONCRETE I:N COMPRESSION," J o u r n a l of American Concrete I n s t i t u t e , V o l . 75, N o . 11, NOV 1978, pp. 603-611.

A r e l a t i v e l y simple exper imenta l t echn ique i s used t o o b t a i n t h e s t r e s s - s t r a i n cu rves of c o n c r e t e s up tcl a s t r a i n of 0 . 0 0 6 . The s t r e s s - s t r a i n cu rves of norma.1 weight c o n c r e t e s of s t r e n g h t s up t o 1 1 , 0 0 0 p s i and l i g h t w e i g h t c o n c r e t e of strength:; up t o 8000 ps i are r e p o r t e d . An a n a l y t i c expres s ion f o r t h e stress- s t r a i n curve of c o n c r e t e i s deve1Loped t o ref lect exper imenta l r e s u l t s . T h e a n a l y t i c expres s ion has f o u r c o n s t a n t s which depend on t h e p r o p e r t i e s of b o t h t h e ascending and t h e descending p o r t i o n s of t h e s t r e s s - s t r a i n curve and can be e v a l u a t e d from t h e knowledge of f o u r key p o i n t s of t h e cu rve . The c o o r d i n a t e s of t h e f o u r key p o i n t s were expres sed i n f u n c t i o n of t h e compressive s t r e n g t h of c o n c r e t e s o as t o a l low p r e d i c t i o n of t h e e n t i r e curve s o l e l y from t h e knowledge of t h e compressive s t r e n g t h .

1 1 2 4 . Young, J. F. and Berger, R. L . e t a l . , "SHRINKAGE OF TRICALCIUM SILICATE PASTES: SUPEIWOSITION OF SEVERAL MECHANISMS," Cemento, V o l . 75, No. 3, 1978, pp. 391- 398.

Drying shr inkage of t r i c a l c i u r n s i l i c a t e p a s t e s cu red a t 4 DEGREE C, 25 DEGREE C, and 65 DEGREE C i s related to the physico-chemical microstructural f e a t u r e s of cumulat ive p o r e volume, p o r e s i z e d i s t r i b u t i o n and degree of s i l i ca t e po lymer i za t ion . T h e d r y i n g shr inkage can be related t o t h e cumulat ive effect of two c o n c u r r e n t l y p r o g r e s s i n g mechanisms namely, c a p i l l a r y d ry ing and gel d r y i n g . T h e r e l a t i v e c o n t r i b u t i o n of each mechanism i s dependent upon degree of hydra t ion and wa te r - so l id s r a t i o . The mechanisms can e x p l a i n some o f the c o n f l i c t i n g d r y i n g sh r inkage measurements which have been r e p o r t e d i n t h e l i t e r a t u r e . T h e i n f l u e n c e of admixtures C a ( C 1 * * 2 ) and Ca(NO**3) on d ry ing shr inkage are a l s o d i s c u s s e d .

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1 9 7 9

1125. Alexander , K . M . and Wardlaw, J. e t a l . , "INFLUENCE OF S 0 / / 3 CONTENT OF PORTLAND CEMENT ON THE CREEP AND OTHER PHYSICAL PROPERTIES OF CONCRETE," Cement and C o n c r e t e Research , V o l . 9, No. 4 , 1979, pp. 451-459.

T h e impor t ance o f t he c o r r e c t amount of gypsum, S0 / /3 , added t o c l i n k e r , t o c o n t r o l s e t t i n g t i m e i s emphas ized . I t i s shown t h a t t h e creep of c o n c r e t e i s v e r y s e n s i t i v e t o t he S0 / /3 c o n t e n t o f cement . Examples are g i v e n i n which creep d o u b l e s when S 0 / / 3 i s reduced from 3. 7 t o 1. 6%. I t i s a l s o d e m o n s t r a t e d t h a t t h e dependence o f creep on t h e S0//3 c o n t e n t o f cement d o e s n o t v a r y w i t h t h e d u r a t i o n of the c r e e p t e s t . Compressive s t r e n g t h t o 1 y e a r , modulus o f e l a s t i c i t y , d r y i n g s h r i n k a g e and 3-year e x p a n s i o n i n water were measured and t h e r e l a t i o n s h i p s between these p r o p e r t i e s of c o n c r e t e and the S0//3 c o n t e n t o f cement w e r e de t e rmined .

1 1 2 6 . Andrews , K . R. F . and Moharram, A. e t a l . , "SHAKEDOWN STRESSES DUE TO CREEP AND CYCLIC TEMPERATURES I N CONCRETE STRUCTURES," Envi ron F o r c e s on Eng S t r u c t ; P r o c o f t h e I n t Conf, l s t , Imp Coll, 1979, pp. 475- 486.

T h i s paper p r e s e n t s an e l a s t i c s t i f f n e s s ana logy f o r t he c y c l i c t h e r m a l creep problem. I t i s deve loped from a minimum average power p r i n c i p l e and i s r e a d i l y u t i l i z e d i n s t a n d a r d f i n i t e e l emen t programs.

1127. Anon, "CONCRETE COMPRESSIVE STRENGTHS I N 5 HOURS," C o n c r e t e C o n s t r u c t i o n , V o l . 24, No. 9 , Sep 1979, pp. 607-610.

A new tes t h a s been deve loped t h a t g ives s t r e n g t h r e s u l t s 5 h o u r s a f t e r t h e tes t c y l i n d e r s are made. T h e method w a s applied t o c o n c r e t e f l o o r s t h a t were cast b e f o r e t h e f irst 28-day c y l i n d e r tes t r e s u l t w a s available. Method and equipment u s e d and r e s u l t s o b t a i n e d are o u t l i n e d .

1 1 2 8 . A r t h u r , P . D . and E a r l , J. C . e t a l . , "FATIGUE O F REINFORCED CONCRETE I N SEAWATER," C o n c r e t e (London) , Vol. 13, No. 5, 1979, pp. 26-30.

The a u t h o r s describe t h e s t u d i e s of t h e f a t i g u e b e h a v i o r o f r e i n f o r c e d and prestressed c o n c r e t e i n seawater, c o n c e n t r a t i n g main ly on l o w stress c y c l e f r e q u e n c i e s , and t h e a r t i c l e p r e s e n t s some i n i t i a l r e s u l t s on r e i n f o r c e d c o n c r e t e .

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1129. Brooks, J. and Wainwright, P. et al., "SUPERPLASTICISER EFFECT ON TIME-DEPENDENT PROPERTIES OF AIR ENTRAINED CONCRETE," Concrete, Vol.. 13, No. 6 , Jun 1979, pp. 35-38.

Developed more than 15 years ago in Japan, and in commercial use in Germany since 1972, superplasticisers are stated as having considerable advantages over conventional plasticisers. In order to assess these benefits, a series of tests is reported, undertaken to investigate the long-term behaviour of concretes containing the superplasticiser irgament mighty 150, type: napthalene sulphonate/formaldehyde condensate. The time- dependent behaviour of strength, elasticity, durability, creep and shrinkage of high workability (flowing) admixture air entrained concretes are reported. Details of the mixes used in the tests are provided, and the experimental d.ata are presented an,d the results discussed.

1130. Bryant, A. H., IICREEP AND SHRINKAGE OF A BRIDGE- BUILDING CONCRETE," Journal of the American Concrete Institute, Vol. 76, No. 3, Mar 1979, pp. 387-403.

Experimental results for creep and shrinkage of a bridge-building concrete are presented for specimens kept inside a laboratory and on top of, inside, and underneath a concrete box girder bridge. The environment is shown to have considerable effect on creep and shrinkage but it is cc-ncluded that location at the bridge was relatively unimportant. Code predictions of creep and shrinkage were close to experimental values provided that a suitable value of relative humidity was chosen.

1131. Colony, D., "INDUSTRIAL WASTE PRODUCTS IN PAVEMENTS: POTENTIAL FOR ENERGY CONSERVATION," Transportation Research Record, N734, 1979, pp. 16-21.

Criteria for evaluating the potential performance of industrial waste products as pavements materials are outlined. It is shown that a net energy saving is realized over a selected analysis period whenever the energy saved in the production cf raw materials for a pavement that contains waste products (in comparision with a conventional pavement design) is equal to or greater than a function of the energy cost of resurfacing and the times required for both the conventional and waste-product pavements to reach a present serviceability index of 2.5. The 'marginal waste product' is (a) in energy terms, that material for which the energy cost of resurfacing over the analysis period, and (b) i.n ecor.omic terms, that

product for which the cost per unit of energy saved is equal to the current unit price of energy. Potentially useful industrial waste products can be ranked according to these criteria. A performance criterion for waste materials requires that data be available on which to base reasonable estimates of serviceability history. Several examples of waste products that are currently used as paving materials are discussed, and a statistical study of the compressive strength of pozzolanic concrete correlated with available data on pavement performance is examined.

1132. Edwards, J. and Holman, F., "CONCRETE PROPERTIES FOR RIGID PAVEMENT DESIGN," Alabama State Highway Dept., Mar 1979, pp. 25.

Representative Alabama coarse aggregates were included in appropriate concrete pavement mix designs and the resulting concrete tested for compressive and splitting tensile strengths and modulus of elasticity. From these test results, representative values of each were recommended for use in the 'Alternate Procedure for the Design of Rigid Pavement' as described in the AASHTO Interim Guide For Design of Pavement Structures, 1972.

1133. Fataliev, S. and Samedov, M. et al., "OBTAINING HIGH STRENGTH POROUS AGGREGATES FOR CONCRETE," Stroitel Nye Materialy, N5, 1979, pp. 26-28.

Following a brief explanation of the low strengths obtained for expanded clays, the authors describe a heating technique at 1450 or even 1500 deg C, with fusion of the raw clay, followed by rapid freezing causing re-crystallization. After pulverising, the addition of additives and humidification the material is granulated, then expanded between 1000 and 1100 deg C in a rotary furnace or a fluidified bed. The process is still experimental.

1134. Fowler, D., "CONCRETE-POLYMER MATERIALS FOR HIGHWAY APPLICATIONS," Res Report 114-9F, Final Report, Mar 1979, pp. 32.

The use of concrete-polymer materials for highway applications has been studied with the objective of providing durable materials that would reduce maintenance in highway structures. Several significant developments resulted from this research. Partial-depth polymer impregnation was developed for improving durability of bridge decks. The process includes drying the concrete, cooling the surface, applying a low viscosity monomer solution to a sand cover, and permitting it to soak into the concrete,

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and a p p l y i n g heat t o po lymer i ze t h e monomer i n t h e c o n c r e t e t o a depth o f 0 . 5 i n . ('1.3 c m ) o r more. P o s t - t e n s i o n e d polymer- impregnated beams were made and tested t o d e t e r m i n e t h e s t r u c t u r a l b e h a v i o r . Beams w i t h a n I-shaped c r o s s - s e c t i o n and a span o f 8 f t ( 2 . 7 m) w e r e f u l l y impregnated w i t h a monomer s o l u t i o n . High s t r e n g t h w i r e t e n d o n s were p o s t - t e n s i o n e d and t h e beams were tested t o d e t e r m i n e the f l e x u r a l and shear b e h a v i o r . S i g n i f i c a n t i n c r e a s e s i n s t r e n g t h a n d s t i f f n e s s were obse rved . Time-de;?endent d e f l e c t i o n s w e r e r educed by a n o r d e r o f magni tude . Polymer c o n c r e t e w a s deve loped f o r r e p a i r i n g bridge decks. Clean , d r y , graded aggregate i s :?laced i n t h e repair area and a monomer sys tem t h a t h a s s u f f i c i e n t p romote r and i n i t i a t o r t o po lymer i ze a t ambient c o n d i t i o n s i s applied t o f u l l y s a t u r a t e t h e aggregate. P o l y m e r i z a t i o n o c c u r s i n 30 t o 4 5 minu tes , p r o d u c i n g a sound and d u r a b l e repair . A polymer c o n c r e t e o v e r l a y w a s deve loped t o wa te rp roof b r i d g e decks. A t h i n l a y e r o f d r y s a n d i s c o v e r e d w i t h c o a r s e aggregate. Two monomer s o l u t i o n s are a p p l i e d and p o l y m e r i z a t i o n o c c u r s a t ambient t e m p e r a t u r e . (FHWA) S tudy conduc ted i n c o o p e r a t i o n w i t h t he Department o f T r a n s p o r t a t i o n , Federal Highway A d m i n i s t r a t i o n . Research Study T i t l e : 'Polymer-Impregnated Concre t e f o r Highway A p p l i c a t i o n ' .

1135. Galloway, J. W . and Harding, H . M . e t a l . , "EFFECTS O F AGE ON FLEXURAL, FATIGUE AND COMPRESSIVE STRENGTH OF CONCRETE, I' TRRL L a b o r a t o r y Repor t ( T r a n s p o r t and Road Research Labora to ry , Great B r i t a i n ) , 1 9 7 9 , pp. 23 .

F l e x u r a l s t r e n g t h tes ts on small c o n c r e t e beams a t ages u p t o t e n y e a r s and f a t i g u e tests up t o f i v e y e a r s are r e p o r t e d . T e s t s w e r e made on three t y p e s of c o n c r e t e , two c o n t a i n i n g f l i n t gravel aggregate, t h e o t h e r c o n t a i n i n g c r u s h e d l i m e s t o n e . Two o f t h e c o n c r e t e s were o f pavement q u a l i t y and the o t h e r was a d r y l e a n mix. I n e a c h case s u b s t a n t i a l i n c r e a s e s i n b o t h s t a t i c s t r e n g t h and f a t i g u e pe r fo rmance were obse rved , w i t h a modest i n c r e a s e i n modulus o f e l a s t i c i t y . The f l e x u r a l s t r e n g t h i n c r e a s e d more r a p i d l y t h a n t he compress ive s t r e n g t h .

1 1 3 6 . Galloway, J. W. and Harding, H . M . e t a l . , "EFFECTS O F MOISTURE CHANGES ON FLEXURAL AND FATIGUE STRENGTH O F CONCRETE," TRRL L a b o r a t o r y Repor t ( T r a n s p o r t and Road Research L a b o r a t o r y , Great B r i t a i n ) , 1 9 7 9 , pp. 3 4 .

R e s u l t s are g i v e n o f f l e x u r a l s t r e n g t h and f a t i g u e tests on s m a l l u n r e i n f o r c e d beams o f pavement q u a l i t y c o n c r e t e t o s t u d y the e f fec ts o f v a r i o u s m o i s t u r e c o n d i t i o n s . S u b s i d i a r y tests i n c l u d e d dynamic modulus o f e l a s t i c i t y and e q u i v a l e n t cube c r u s h i n g t e s t s on

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the fractured specimens. The report discusses effects of moisture condition at the time of test, and the method of curing.

1137. Garrett, G. G. and Jennings, H. M. et al., "FATIGUE HARDENING BEHAVIOUR OF CEMENT-BASED MATERIALS," Journal of Materials Science, Vol. 14, No. 2, 1979, pp. 296-306.

This paper describes part of a study into the fatigue behaviour of cement-based materials. The mode and mechanism of stable microcracking which occurs during both monotonic and cyclic loading has been examined using a novel re-hydration technique. It is shown that unhydrated particles exposed during fatigue, which are not revealed after monotonic (static) failure, result from an attrition process which takes place subsequent to the passage of the major microcrack fronts. Increases in ultimate static strength after fatigue, which can be produced in specimens tested over a wide range of applied stress, only occur with the presence of free , or chemically uncombined, water within the cement matrix Such fatigue hardening is dependent on damage introduced as microcracks in the early part of the fatigue life, and arises essentially from an in situ, microstructural self-repair process.

1138. Gerstle, K. H., "MATERIAL BEHAVIOR UNDER VARIOUS TYPES OF LOADING," Proc of the Workshop on High Strength Concr, Univ of I11 at Chicago Circle, 1979, pp. 43-78.

The present state of knowledge of the mechanical behavior of high-strength concrete is summarized, and it is concluded that, with the exception of its response to monotonically-applied uniaxial loadings, little is known. Response and strength of high- strength concrete under uniaxial compressive and tensile loadings are concisely described by reference to previous studies. Comparison of multiaxial tests of different strength concretes indicates no qualitative differences between the behavior of normal and high- strength concretes. Areas of deficient knowledge are delineated, and some suggestions are made for future research.

1139. Hudson, L. J. and Symons, M. G., "EFFECT OF DELAY TIME AND STEAM CURING ON CONCRETE PROPERTIES," National Conference Publication - Institution of Engineers, Australia n 79/9, Symp on Concr 1979, Cases and Concepts, Canberra, Australia, 1979, pp. 69-73.

times between mixing and start of accelerated curing This paper examines the effects of varying delay

59

on t h e pos t - cu r ing and l a t e r age s t r e n g t h s f o r a h igh e a r l y s t r e n g t h (Type B) cement and a b l end of h igh e a r l y s t r e n g t h cement w i t h P o r t Augusta f ' lyash. Optimum d e l a y p e r i o d s are demonstrated. T h e compressive s t r e n g t h s a t 28 days a f t e r a c c e l e r a t e d steam c u r i n g are found t o exceed t h e 28 day s t r e n g t h s of s t a n d a r d fog cured c o n c r e t e f o r d e l a y p e r i o d s equa l t o o r greater t h a n f o u r hour s . During t h e delay p e r i o d t h e c o n c r e t e specimens were s t o r e d a t a t empera tu re of 2 3 DEGREE C . To observe any changes i n t he hardened cement p a s t e due t o v a r i a t i o n s i n t h e c u r i n g c y c l e , e l e c t r o n micrographs of t he s u r f a c e of discs c u t froin c o n c r e t e t es t c y l i n d e r s w e r e t a k e n . These reveal t h a t t h e r e d u c t i o n i n s t r e n g t h caused b y inadequate delay is a s s o c i a t e d w i t h a less c r y s t a l l i n e h y d r a t i o n product i n t he hardened cement p a s t e . 6 refs.

1 1 4 0 . I y e r , L. S. and Phelps , R . , "CREEP AND SHRINKAGE O F

I n t e r n a t i o n a l Jou rna l of Cement Composites, Vol. 1, LATEX M O D I F I E D VERSUS GAP-GRADED CONCRETE,"

N O . 4 , 1979, pp. 171-175.

Creep and shr inkage a r e determined f o r b o t h t h e l a t e x modif ied and gap-graded c o n c r e t e accord ing t o t h e s t a n d a r d s of t he American Soc ie ty f o r T e s t i n g and Materials. Equat ions based on t h e p r e s e n t d a t a are proposed f o r t h e p r e d i c t i o n of c r e e p and sh r inkage f o r b o t h l a t e x modif ied and gap-grad.ed c o n c r e t e . From the r e s u l t s of t h i s i n v e s t i g a t i o n , sh r inkage deformat ions and creep s t r a i n s of t he l a t e x n o d i f i e d c o n c r e t e specimens, i n g e n e r a l , w e r e found t o be respectively approximately 2 4 0 and 1 2 0 p e r c e n t larger t h a n t h o s e f o r t h e gap-graded c o n c r e t e specimens.

1 1 4 1 . Kadlecek, V. D . , J . , "DETECTION O F THE DETERIORATION OF CONCRETE BY THE MICKOHARDNESS MEASUREMENTS, l1 Contro le de Qua1 d e s S t r u c t en Beton, Stockholm, Sweden, Vo1.2, Jun 1 3 7 9 , pp . '77-84.

T h e microhardness t e s t method, which pe rmi t s i d e n t i f i c a t i o n of mechanical p r o p e r t y changes of d e f i n e d microvolumes of concrete:, i s used f o r d e t e c t i n g the formation and development of microcracks . An example of s u c c e s s i v e l y loaded c o n c r e t e shows the a p p l i c a t i o n of t he microhardness test method. T h e p o s s i b i l i t y of apply ing t h e method t o i n v e s t i g a t e t h e development of d e t e r i o r a t i o n of c o n c r e t e i n s t r u c t u r e s has proved feasible , p a r t i c u l a r l y a t t he beginning of c o n c r e t e l o a d i n g (i . e . when t h e l o a d va lues are i n t h e range of 20 t o 60% of t he u l t i m a t e l o a d ) . The s u c c e s s i v e load ing of t es t specimens causes a decrease of microhardness v a l u e s by 35 t o 6 5 % . These v a l u e s change i n accordance w i t h the p o s i t i o n of t he measured

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area referred to the external loading direction. Consequently, the microhardness test method can be properly used for investigation of the deterioration of hydrated cement paste and concrete structures.

1142. Klausen, D. and Weigler, H., "STRENGTH OF CONCRETE UNDER CONSTANT AND VARIABLE PULSATING FATIGUE LOAD," Study & Res Cent for Cement Manufacturing Industry, Epernon, France, Mar 1979, pp. 23-35.

A study is presented of the fatigue strength of concrete, stress distribution and deformations under repeated loads varying in magnitude and frequency. The lifetime of concrete is evaluated using Miner's hypothesis of linear accumulation of damages due to stresses exceeding fatigue strength. Results of tests in ordinary and lightweight concrete are given together with general conclusions on the effects of service loads. This article is a translation into French of an original German article entitled: 'Betonfestigkeit bei Konstanter und Veraederlicher Dauerschwellbeanspruchung' which was publised in Betonwerk, Fertigteil-Technik, 1979 (3), 158-63.

1143. Kotsovos, M., "A MATHEMATICAL DESCRIPTION OF THE STRENGTH PROPERTIES OF CONCRETE UNDER GENERALIZED STRESS," Magazine of Concrete Research, Vol. 31, No. 108, Sep 1979, pp. 151-158.

A mathematical description of the ultimate strength envelope of concrete under axisymmetric stress states has been derived by analysing experimental data obtained in previous investigations of the Concrete Materials Research Group at Imperial college. The derived equations, when combined with an expression proposed elsewhere for the description of the effect of the intermediate stress upon the ultimate strength level, define a surface in stress space which provides a simple mathematical representation of the ultimate strength of concrete under generalized short-term loading conditions. The resulting ultimate strength surface conforms with generally accepted shape requirements and has been found to provide a close fit for most biaxial and triaxial strength data published to date.

1144. Mailhot, G. and Bisaillon, A . et al., "IN-PLACE CONCRETE STRENGTH: NEW PULLOUT METHODS," Journal of The American Concrete Institute, Vol. 76, No. 12, Dec 1979, pp. 1267-1282.

Investigations were undertaken to develop pullout tests that could be carried out on finished structures. Three possible approaches considered

61

were: p u l l i n g o u t of t a p e r e d anchors p l a c e d i n d r i l l ed ho le s ; p u l l i n g ou t of b o l t s set i n hardened c o n c r e t e u s i n g epoxy; and measuring t h e f o r c e r e q u i r e d t o cause shear f a i l u r e of c o n c r e t e u s i n g a s p l i t - sleeve assembly. The techniques were t r i ed on 25 c o n c r e t e slabs. The c o n c r e t e covered a s t r e n g t h range from 1 7 t o 42 MPa. More t h a n 1 0 0 0 p u l l o u t tes ts u s i n g t h e three t echn iques were performed.

1145. McBee, W . and S u l l i v a n , T . , "DEVELOPMENT OF SPECIALIZED SULPHUR CONCRETES," I n v e s t Rpt, Bureau of Mines, 1979, pp. 27.

S p e c i a l i z e d s u l f u r c o n c r e t e s were developed by the Federal Bureau of Mines as a r e s u l t of research f o r t h e b e n e f i c i a l u t i l i z a t i o n of s u l f u r i n c o n s t r u c t i o n materials. Materials were develolped f o r u se i n acid and s a l t c o r r o s i v e environments .where p o r t l a n d cement c o n c r e t e has been found t o d e t e r i o r a t e . Because t he minera l aggregates a l s o come i n t o c o n t a c t w i t h the c o r r o s i v e media, c o n c r e t e s w e r e developed u t i l i z i n g b o t h l imes tone and q u a r t z aggrega te s . T h e s u l f u r b i n d e r used w i t h b o t h aggrega te s was modi f ied by r e a c t i o n w i t h 5 p c t d i cyc lopen tad iene t o improve product d u r a b i l i t y . S u l f u r q u a r t z aggregate c o n c r e t e was found t o have moderately hig:h s t r e n g t h characterist ics ( 6 , 0 0 0 p s i compressive) and w a s ex t remely r e s i s t a n t t o chemical .st tack by b o t h acid and s a l t s o l u t i o n s . S u l f u r l imes tone aggrega te c o n c r e t e e x h i b i t e d very high s t r e n g t h character is t ics ( 9 , 0 0 0 p s i compressive) and was e x t r e m e l y r e s i s t an t t o chemical attack of s a l t s o l u t i o n s . Both types of c o n c r e t e s main ta ined the i r s t r e n g t h and i n t e g r i t y af ter long-term t e s t i n g i n acid ,and s a l t s o l u t i o n s and e x h i b i t e d c o n s i d e r a b l e r e s i s t a n c e t o damage by the a c t i o n of f r e e z i n g and thawing. : ? o t e n t i a l u s e s i n c l u d e leach t a n k s , e l e c t r o l y t i c cel ls , t h i c k e n e r s , bridge decking, i n d u s t r i a l f l o o r i n g , p ipe , and t i l e .

1 1 4 6 . Na ik , T . R. , "UTILIZATION OF ACCZLERATED STRENGTH T E S T I N G METHODS," Cement and Concrete Research, Vo1.9, No.1, J an 1 9 7 9 , pp. 7-17.

T h i s paper p r e s e n t s methods t o predict the l a t e r age s t r e n g t h of conc re t e and d i s c u s s e s how these methods can be adapted f o r q u a l i t y c o n t r o l and q u a l i t y a s su rance of c o n c r e t e f o r small as well a s l a r g e p r o j e c t s . These methods were fou:nd t c be more s u i t a b l e t h a n o t h e r A . S . T . M . methods. An a c c e l e r a t e d s t r e n g t h t e s t i n g program, a long wi th t h e r e l i a b i l i t y of r e s u l t s ob ta ined , i s a l s o discussed.

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1147. Osidze, V. I. and Khoperiya, D. L., "EFFECT OF AGGREGATE SIZE ON THE TENSILE STRENGTH OF HYDRAULIC- CONCRETE SPECIMENS," Hydrotechnical Construction, No. 3, Mar 1979, pp. 239-244.

The effect of specimen size on the tensile strength of hydraulic concrete was studied by testing two groups of test cylinders for splitting-tensile strength (along the generatrix). This first group included five series, which differed in size. The effect of specimen length on the tensile strength of concrete was investigated by testing a second group consisting of four series. These series were distinguished only by the length of the test cylinders: 10, 15, 20, and 30 cm. The diameter of the specimens of all series in the second group was held constant at 15 cm. 8 refs.

1148. Pesch, L., "ADEQUATE CAPACITY FOR RESISTANCE TO FROST AND DE-ICING SALT," Betonwerk und Fertigteil-Technik, Vol. 45 No. 5, May 1979, pp. 304-307.

The information sheet 'Examination of Concrete Products for Road Construction having Joints Capable of Withstanding Frost and Salt' published in January 1979 by the Federal German Association of the Concrete- and Pre-cast Unit-Industry its reproduced in full. Although the mechanism in concrete for reacting to frost and salt had been widely researched, until now no uniform view of the matter was possible, such as a forecast about the reaction in practice. The suggested test procedure, the sprinkled-salt method followed by rolling, should enable results to be collected which can then, insofar as it is applicable, be compared with results from practical experience. It is still open as to which grade of weathering, determined as loss in mm can be allowed. Because the time and resource expenditure for the test is considerable, reference should be made to other types of test for specific inspection, with which the frost- salt resistance capacity may be judged. Reference is made to the difficulties of carrying out the tests on mildewed and multi-layered concrete.

1149. Raithby, K. D., "FLEXURAL FATIGUE BEHAVIOUR OF PLAIN CONCRETE," Fatigue of Engineering Materials and Structures, Vol. 2, No. 3, 1979, pp. 269-278.

Of course, the term concrete does not represent a single material having unique properties but in fact covers a whole range of inhomogeneous composites in which discrete particles of relatively inert material (coarse and fine aggregate) are bound together by a

63

cemen t i t i ous ma t r ix . The p r o p e r t i e s of the r e s u l t i n g agglomerate depend no t only on t h e p r o p e r t i e s of t he , c o n s t i t u e n t par t s b u t on the i n t e r a c t i v e behaviour of t h e whole. This i s a f f e c t e d by time-dependent variables such as mois ture movements, r a t e of l oad ing and creep and the i r i n t e r a c t i o n w i t h t h e ra te a t which h y d r a t i o n of the cement ma t r ix c c c u r s over extended t i m e p e r i o d s . I n t h i s paper some of t h e c o n d i t i o n s which affect t he f l e x u r a l fatigL.e behavior of t y p i c a l c o n c r e t e mixes a r e d i scussed .

1150. Reinhard t , H . , "DETERMINATION OF THE TENSILE STRENGTH O F CONCRETE UNDER IMPACT I ,OADING," Cemeniz, Vol. 31, No. 9, Sep 1979, pp. 4 1 1 - 4 1 4 .

An appa ra tus f o r t h e de t e rmina t ion of t h e t e n s i l e s t r e n g t h of c o n c r e t e under impact l o a d w i t h c e n t r i c t e n s i o n i s developed. a p p a r a t u s are d i scussed . Conclusions are drawn w i t h r e s p e c t t o the i n t e r r e l a t i o n of t h e ra te of loading , t h e ( s t a t i c o r . impact ) t e n s i l e s t r e n g t h , t h e water cement r a t i o and t h e mois ture c o n t e n t of c o n c r e t e . The k ind and t h e q u a l i t y of t he cement were found t o have no i n f l u e n c e upon t h e r e l a t i o n between t h e r a t e of l o a d i n g and t h e t e n s i l e s t r e n g t h of c o n c r e t e . Repeated impact l oad ing led t o s imi l a r r e s u l t s f o r a l l k inds of conc re t e : i n c r e a s e of t.he number of blows causes decrease i n s t r e n g t h .

The r e s u l t s of tes ts w i t h t h i s

1151. Sauc ie r , K., "HIGH-STRENGTH CONCRETE, PAST, PRESENT, FUTURE," Army Engineer Waterways: Experiment S t a t i o n Vicksburg MS, May 1 9 7 9 , pp. 1 7 .

s t r e n g t h conc re t e , t he r e s e a r c h needed, and the in fo rma t ion and exper ience requi-red f o r h igh - s t r eng th c o n c r e t e t o become u n i v e r s a l l y accep ted . Discuss ion i n v o l v e s examinat ion of three l e v e l s of h igh - s t r eng th conc re t e : (1) t h e p r e s e n t range of 5,000 t o 1 0 , 0 0 0 p s i (34.4 t o 68.9 MPa), ( 2 ) t he ava:Llable range of 1 0 , O C . O t o 15,000 p s i (68.9 t o 103.4 MPa), and (3) t he ex0t i . c area of 1 5 , 0 0 0 p s i (103.4 M P a ) . P r e s e n t p r a c t i c e s i n c l u d e u s e of l o w W/C, high cement f a c t o r , mixtures; w i th f l y ash, h igh -qua l i ty c rushed aggrega te s , high-. range water-reducing admixtures, , and more c o o r d i n a t i o n and q u a l i t y c o n t r o l e f f o r t s . t h e second range i s a t t a i n a b l e wi th available mater:ials and equipment such as s l u r r y mixing, no-slump conc re t e , c l o s e r c o n t r o l , compaction b y p r e s s u r e , new admixtures , l onge r cu r ing , and polymer material . research i n t h e a r e a s of v i b r a t i o n and compaction, u se of a r t i f i c i a l aggregates, polymers, d i scon t inuous re inforcement , i n t e r a c t i o n w i t h t he energy s i t u a t i o n , and des ign c o n s i d e r a t i o n s w i l l be needed b e f o r e t h e 15,000-psi

T h i s paper summarizes the c u r r e n t s t a t u s of high-

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(103.4-MPa) range can be successfully entered. the exotic area may include heretofore impractical techniques such as combining pressure and vibration and development of the silica-lime bond. A prediction is offered of the technique to be used for the manufacture, placement, and consolidation of high- strength concrete in the year 2000.

1152. Shah, S., "HIGH STRENGTH CONCRETE," Proceedings of a Workshop Held at the University of Illinois at Chicago Circle, December 2-4, 1979, pp. 235.

These workshop proceedings contain fourteen papers on various aspects of concrete and high strength concrete. The workshop was divided into five sessions: (1) Micromechanics of Achieving High Strength Concrete, (2) Material Behavior Under Various Types of Loading, (3) Inelastic Behavior of Structural Elements and Structures, ( 4 ) Special Design Features Appropriate for High Strength Concrete, and (5) Concluding Session. Sponsored in part by National Science Foundation, Washington, DC.

1153. Sprinkel, M., "SUPER-WATER-REDUCED CONCRETE PAVEMENTS AND BRIDGE DECK OVERLAYS," Transportation Research Record, N720, 1979, pp. 19-28.

In order to obtain mixtures that have (a) a consistency that would permit use of conventional placement equipment and (b) a water-to-cement ratio of 0-.33-0.37, melamine- and naphthalene-sulfonated polymer admixtures were used in the concrete placed in two experimental pavements and four bridge deck overlays. With one exception, ready-mix trucks were used to mix the concrete, and placement methods included direct discharge, buggy, crane and bucket, and pump. Internal vibration was used for consolidation, and the screeding equipment included a wooden straightedge, an oscillating screed, a rotating-drum screed, and a metal vibrating straightedge. Compression-tested specimens from the projects showed significantly higher early and 28-day strengths than specimens without the admixture, and petrographic examinations of cores taken from the overlays indicated that, on the average, the concrete was properly consolidated and controlled. However, because of the extreme variability of the concrete, many portions of the completed structures exhibited inadequate consolidation, segregated mixture components, improperly entrained air, shrinkage cracks, and poor finishes. Also specimens from freeze-thaw tests showed low durability factors that were attributed to an unsatisfactory air-voids system.

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T h i s paper appeared i n Transpor t a t ion Research Record No. 720, S u p e r p l a s t i c i z e r s i n Concrete .

1154. Stock, A. and Hannant, D . e t al., "THE EFFECT O F AGGREGATE CONCENTRATION UPON THE STRENGTH AND MODULUS OF ELASTICITY OF CONCRETE," Magazine of Concrete Research, V o l . 31, No. 1 0 9 , Dec 1979, pp. 225-234.

T h e paper p r e s e n t s de t a i l s of an i n v e s t i g a t i o n i n t o t h e effect of aggrega te c o n c e n t r a t i o n upon t h e s t r e n g t h and modulus of e l a s t i c i t y of c o n c r e t e i n b o t h u n i a x i a l t e n s i o n and u n i a x i a l compression. T h e t es t r e s u l t s re la te t o cement p a s t e and t o mixes c o n t a i n i n g 20 t o 80% by volume of a graded aggregate. Emphasis w a s p l a c e d on a c c u r a t e de t e rmina t ion of t h e s p e c i f i c g r a v i t y and a b s o r p t i o n of t h e c o n s t i t u e n t aggrega te s i z e f r a c t i o n s i n an a t tempt t o main ta in a c o n s t a n t free water/cement r a t i o i n t h e v a r i o u s mixes. The specimens were cont inuous ly r o t a t e d d u r i n g t h e s e t t i n g p e r i o d i n o r d e r t o minimize s e t t l e m e n t of t h e aggregate p a r t i c l e s . The r e s u l t s sugges t t h a t t he s t r e n g t h of cement p a s t e i n t e n s i o n and i n cornpression i s reduced by t h e a d d i t i o n of 20% by volume of graded aggregate, f a l l i n g t o a minimum va lue a t a volume f r a c t i o n of 30 t o 35% and t h e n i n c r e a s i n g w i t h f u r t h e r a d d i t i o n of aggregate. I n c o n t r a s t , t h e modulus i n t e n s i o n and i n compression i n c r e a s e s wi th t h e a d d i t i o n of aggregate and t h e measured v a l u e s are compared w i t h t h e o r e t i c a l p r e d i c t i o n s based upon t h e l a w s of mix tu res .

1155. T a s u j i , M . and Nilson, A. e t a l . , "BIAXIAL STRESS- STRAIN RELATIONSHIPS FOR CONCRETE," Magazine of Concrete Research, V o l . 31, No. 1 0 9 , D e c 1 9 7 9 , pp. 217-224.

On t h e basis of exper imenta l r e s u l t s , a stress- s t r a i n r e l a t i o n s h i p i s proposed f o r p l a i n c o n c r e t e t h a t i s a p p l i c a b l e t o a l l combinations of b i a x i a l t e n s i o n and compression. The proposed equa t ion accounts f o r b o t h non-l inear and o r t h o t r o p i c behaviour of c o n c r e t e . Also based on exper imenta l r e s u l t s , a b i a x i a l u l t i m a t e s t r e n g t h c r i t e r i o n i s proposed f o r c o n c r e t e i n t he form of a f a i l u r e stress envelope. The proposed equa t ions a r e given i n a form such t h a t t h e y may be inco rpora t ed r ead i ly i n p l a n e - s t r e s s a n a l y s i s of r e i n f o r c e d c o n c r e t e us ing t h e f i n i t e - element approach.

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1156. Tepfers, R., "TENSILE FATIGUE STRENGTH OF PLAIN CONCRETE," Journal of The American Concrete Institute, Vo1.76, No.8, Aug 1979, pp. 919-933.

The fatigue tests were performed on cube splitting test specimens which do not have a definite tensile stress distribution. However, distribution of stress has no effect on the results as these are set out in nondimensional form by relating the fatigue stress to the static stress. Two concrete strengths have been tested, and the susceptibility to fatigue due to tensile stresses found to be independent of the level of the strength. Tests have been made with constant values of 0. 20, 0. 30, and 0. 40.

1157. Tepfers, R. and Kutti, T., "FATIGUE STRENGTH OF PLAIN, ORDINARY, AND LIGHTWEIGHT CONCRETE," Journal of The American Concrete Institute, Vol. 76, No. 5, May 1979, pp. 635-652.

An equation is proposed for the determination of the fatigue strength of plain, ordinary, and lightweight concrete when subjected to compressive stresses. The equation expresses both the Woehler and the Smith diagram, and it is shown that the Woehler diagram should be constructed for constant values of the ratio between the lowest and the highest compressive stress under pulsating load, and not for constant stress amplitudes or for constant lower stresses. The equation is verified by laboratory experiments which are presented and by test data taken from the literature.

1158. Wittmann, F. H., "MICROMECHANICS OF ACHIEVING HIGH STRENGTH AND OTHER SUPERIOR PROPERTIES," Source: Proc of the Workshop on High Strength Concr, Univ of I11 at Chicago Circle, Dec 2-4 1979, 1979, pp. 8-30.

With respect to micromechanics, the structure of concrete may be subdivided into three different levels. On the micro-level the porous matrix of hardened cement paste must be dealt with. The structure of mortar is built up by sand inclusions, microcracks, and capillary pores. The mortar structure is defined to be the mezzolevel. Finally the structure of concrete with coarse aggregates, compaction pores, and interfacial cracks is dealt with on the macrolevel. Crack propagation in a homogeneous infinite plate with one cylindrical hole is described. This approach is extended to cover crack formation in porous materials. Then crack formation and crack propagation in a composite material is investigated. The application of micromechanics is further discussed

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by means of two examples, failure under high sustained load, and influence of rate of loading on strength.

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1980

1159. Alexander, K. M. and Bruere, G. M. et al., "CREEP AND

SUPERPLASTICIZED CONCRETE, Cement and Concrete Research, Vol.10, No.2, Mar 1980, pp. 131-137.

RELATED PROPERTIES OF VERY HIGH-STRENGTH

The effect of the superplasticizer 'Melment' on the creep and related properties of concrete has been studied under extreme conditions, in which the strength of the control concrete was the maximum attainable with the cement and aggregates used in the experiment, and in which the admixture dosage level was high enough to change slump from the original value of zero to collapsed, at constant mix proportions.

1160. Brown, T. G. and Baluch, M. H., "MIX DESIGN, DURABILITY AND CREEP CHARACTERISTICS OF SULPHUR INFILTRATED CONCRETE, Cement and Concrete Research, Vol. 10, NO. 5, 1980, pp. 623-630.

The work presented deals with the measurements of certain basic behavioral characteristics required to classify sulfur infiltrated concrete (SIC) as a reliable construction material. The characteristics monitored and presented in this study include mix design parameters and their influence, chemical and environmental stability and the deformation under sustained load of SIC.

1161. Carpenter, J., "APPLICATIONS OF HIGH STRENGTH CONCRETE FOR HIGHWAY BRIDGES,'' Public Roads, Vol. 44, Sep 1980, pp. 76-83.

This article describes the results of the first task of a three-task Federal Highway Administration research project to identify optimum structural applications of high strength concrete in highway bridges. Mixing specifications, physical properties, and advantages and disadvantages of high strength concrete were studied.

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1162. Carse, A. and Behan, J. E., "STATIC CHORD MODULUS OF ELASTICITY OF HIGH STRENGTH CONCRETE IN UNIFORM COMPRESSION AND FLEXURE," Proceedings - Conference of the Australian Road Research Board, Vol.10 Pt 3, 1980, pp. 46-56.

Variables of curing regime, concrete strength, aggregate type and percentage of reinforcement have been considered. The uniform compression test specimen consisted of 150 mm diam by 300 mm long cylinders. A complete range of curing regimes was investigated. The regimes consisted of ambient curing, standard- moist curing and steam curing. Two design strengths of 35 MPa and 50 MPa were considered. Reinforcement was used in the uniform compression tests and was chosen to reflect the range of prestressed and non-prestressed reinforcement in existing structures. The modulus in flexure was determined by loading a column specimen in uniform compression and then applying a moment such that the minimum extreme fiber strain was zero.

1163. Cook, D. J. and Chindaprasirt, P., "INFLUENCE OF LOADING HISTORY UPON THE COMPRESSIVE PROPERTIES OF CONCRETE," Magazine of Concrete Research, Vo1.32, No.111, Jun 1980, pp. 89-100.

The influence of sustained and cyclic load histories upon the compressive properties of concrete, mortar and paste are reported. It is shown that the effects of a sustained load produce a small increase in strength and a relatively large increase in stiffness, whereas cyclic loading results in a small decrease in strength and a relatively large decrease in stiffness.

1164. Gerwick, B. C. Jr, "RESEARCH REQUIREMENTS FGR CONCRETE IN MARINE ENVIRONMENTS," Performance of Concrete in Marine Environment, American Concrete Institute SP-6.5, 1980, pp. 577-587.

Concrete structures are being increasingly utilized for a wide variety of applications in the marine environment. As the structures become more sophisticated (e.g., prestressed) ; and as they are located in areas of more severe exposure (e.g., ice, open sea, etc.), subjected to dynamic cyclic and impact loads, their performance requirements have become increasingly severe and critical. A great deal of relevant research has been carried on in recent years as an outgrowth of the extensive use of concreze

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p l a t f o r m s i n t h e Nor th Sea and t h e N e t h e r l a n d s D e l t a P l a n . A summary of these research programs f u r n i s h e s a u s e f u l s t a r t i n g p o i n t . I n a d d i t i o n , there are a number o f p r o p r i e t a r y programs from which t h e r e s u l t s are n o t y e t p u b l i c l y avai lable . Impor t an t problems s t i l l remain . These can be divided i n t o f ive c a t e g o r i e s : (a ) r e l a t i n g t o i n t e r n a l r e s p o n s e of t h e s t r u c t u r a l e l e m e n t s , (b) r e l a t i n g t o t h e env i ronmen ta l c o n d i t i o n s and f o r c e s under which t h e s t r u c t u r e must serve, (c) r e l a t i n g t o new materials and c o n f i g u r a t i o n s , (d) r e l a t i n g t o c o n s t r u c t i o n practices, i n c l u d i n g r e p a i r s , and (e) r e l a t i n g t o new u s e s i n t h e ocean. Concre t e i s d e s t i n e d t o p l a y an i n c r e a s i n g l y i m p o r t a n t r o l e i n man's expans ion i n t o t h e oceans . n e c e s s a r y i n g r e d i e n t o f t h i s e v o l v i n g t echno logy , i n o r d e r t o e n s u r e o p t i m a l performance.

A s t r o n g and viable research program i s a

1165. Halstead, W . , "USE OF FLY ASH I N CONCRETE BY STATE TRANSPORTATION AND HIGHWAY DEPARTMENTS," V i r g i n i a Highway & T r a n s p o r t a t i o n Research Counc i l , May 1 9 8 0 , pp. 21 .

F i f t y - n i n e a g e n c i e s responded t o a q u e s t i o n n a i r e on u s e o f f l y ash a n d / o r Type I P b l ended cement i n c o n c r e t e . These i n c l u d e d a l l o f t h e s t a t e highway and t r a n s p o r t a t i o n depa r tmen t s , t h e D i s t r i c t of Columbia, three Canadian p r o v i n c e s and f ive federal a g e n c i e s . Twenty-four a g e n c i e s made no u s e of e i t he r s u b s t a n c e i n c o n c r e t e . T h e o t h e r s d id permit t h e u s e of e i ther one o r b o t h , u s u a l l y a t t he o p t i o n o f t h e c o n t r a c t o r . However, o n l y f o u r s ta tes had placed more t h a n 1 0 0 l a n e - m i l e s o f f l y a s h c o n c r e t e , and o n l y two had placed more t h a n 1 0 0 lane-miles of b l ended cement c o n c r e t e . a lack o f economic i n c e n t i v e s . i n v e s t m e n t f o r t h e r e q u i r e d separate s i l o s o r s t o r a g e b i n s , as w e l l as t h e i n c r e a s e d q u a l i t y c o n t r o l t e s t i n g , deters small c o n t r a c t o r s from u s i n g f l y ash . Blended c o n c r e t e i s n o t a t t r ac t ive , s i n c e it u s u a l l y c o s t s t h e same as t h e more f ami l i a r r e g u l a r p o r t l a n d cement. Those s ta tes u s i n g e i ther o r b o t h r e p o r t s a t i s f a c t o r y per formance , w i t h t h e p r imary c o n t r o l problem b e i n g a s s u r i n g t he p r o p e r amount of e n t r a i n e d a i r .

This l a c k o f widespread usage may be due t o The i n i t i a l c ap i t a l

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1166. Hester, W. T., "FIELD TESTING HIGH-STRENGTH CONCRETES: A CRITICAL REVIEW OF THE STATE-OF-THE-ART," Concrete International: Design and Construction, V01.2, No.12, Dec 1980, pp. 27-38.

Contemporary testing procedures for high-strength concretes, and their contribution to the consistency and absolute values of test results, are identified and discussed. The significance of specimen mold materials, consolidation techniques, curing environment, and procedures for application of compression stresses are discussed in detail. Previously published data and conclusions, unpublished research data, and field experiences from the testing of high-strength concretes are critically analyzed. Recommended refinements in exist.ing testing practices are presented.

1167. Hughes, 8. P., "FREEZING AND THAWING AND SCALING RESISTANCE TESTS OF CONCRETE WITH OR WITHOUT SALT DE- ICERS, International Journal of Cement Composites, Vol. 2, No. 2, May 1980, pp. 77--84.

Details of the design and performance of an automatic apparatus for rapid freezing and thawing and scaling resistance tests of concrete are described. Special attention has been pa1-d to minimizing the thermal shock associated with freezing and thawing tests, since this is considered to be a major factor leading to difficulties in relating earlier results to performances under more practical situations. Test procedures are recommended in which concrete specimens are subjected to closely-specified temperature cycles by freezing :in air and thawing by spraying with either water or salt solution.

1168. Kageyama, H. and Nakagawa, K. el: al., "HIGH STRENGTH CONCRETE MADE WITH SPECIAL CEMENT ADMIXTURE," Journal of the Society of Materials Science, Vo1.29, No.318, Mar 1980, pp. 220-225.

A special cement admixture for making high strength concrete has been developed, and the paper reports OD. the basic properties of concrete made with this admixture of 5-10 wt% and some water reducing agent. Compressive strengths of about ;300 kgf/cm**2 and 1000 kgf/cm**2 were achieved at the ages of one day and 26 days, respectively, by steam curing at normal pressure. The flexural strength, tensile strength, elastic modulus, creep, drying shrinkage and frost resistance of the concrete were also determined.

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1169. Kunghan-Roy and Sunghan-Roy e t a l . , "RESEARCH ON SEVERAL PHYSICO-MECHANICAL PROPERTIES O F LIGHTWEIGHT AGGREGATE CONCRETE," I n t l J of Cement Composi tes & L i g h t w e i g h t Concre t e , V o l . 2, N o . 4, D e c 1980, pp. 185-191.

T h e c o n v e r s i o n c o e f f i c i e n t f o r t h e effect o f specimen s i z e on cake compress ive s t r e n g t h i s s i m i l a r t o t h a t o f o r d i n a r y c o n c r e t e . Direct t e n s i l e s t r e n g t h c a n be e x p r e s s e d as a n e x p o n e n t i a l f u n c t i o n . Dimensions have a great i n f l u e n c e on s p l i t t i n g s t r e n g t h . P r i s m compress ive s t r e n g t h i s s l i g h t l y higher t h a n o r d i n a r y c o n c r e t e o f t h e same grade. The same e x p r e s s i o n and cube s i z e o f 10 x 1 0 x 30 c m can be used t o d e t e r m i n e t h e modulus of e l a s t i c i t y o f d i f f e r e n t k i n d s o f l i g h t w e i g h t aggregate c o n c r e t e . However, t h e modulus of e l a s t i c i t y of expanded s l ag c o n c r e t e i s a b o u t 20 p e r c e n t higher t h a n c a l c u l a t e d , and o t h e r v a l u e s are found t o be 25 t o 65 per c e n t l ower t h a n t h a t o f o r d i n a r y c o n c r e t e o f t h e same grade. Exper iments show t h a t t h e t h e r m a l c o n d u c t i v i t y c o e f f i c i e n t i s p r o p o r t i o n a l t o i t s d e n s i t y . The m o i s t u r e c o n t e n t has a c o n s i d e r a b l e effect on specific heat. T h e t e m p e r a t u r e c o n d u c t i v i t y c o e f f i c i e n t depends ma in ly upon t h e d e n s i t y and t h e h e a t s t o r a g e c o e f f i c i e n t i s smaller t h a n t h a t o f o r d i n a r y c o n c r e t e .

1 1 7 0 . Lydon, F. D . and Balendran , R. V . , "SOME PROPERTIES O F HIGHER STRENGTH LIGHTWEIGHT CONCRETE UNDER SHORT-TERM TENSILE STRESS," I n t e r n a t i o n a l J o u r n a l o f L igh twe igh t Concre t e , V o l . 2, No. 3, 1980, pp. 125-139.

T h i s paper describes two methods o f c h e c k i n g t h e t e n s i l e s t r e n g t h of c o n c r e t e , v i z . by u n i a x i a l t e n s i o n and by ax i symmet r i c compress ion t h r o u g h n i t r o g e n - g a s p r e s s u r e applied t o t h e bare c o n c r e t e s u r f a c e . Two l i g h t w e i g h t aggregate c o n c r e t e s and a l i m e s t o n e aggregate c o n c r e t e w e r e tested o v e r a r a n g e o f cement c o n t e n t s and s t r e n g t h s . I t i s s u g g e s t e d t h a t t h e n i t r o g e n gas tes t c o u l d be u s e d as a s i t e tes t ; good c o r r e l a t i o n w a s found between t h e two methods. T h e H . H . Bache/P. Nepper-Chr is tensen model w a s s u c c e s s f u l l y u s e d t o c a l c u l a t e t h e l i g h t w e i g h t aggregate t e n s i l e s t r e n g t h i n c o n c r e t e .

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1171. Malhotra, V. M. and Carette, G., "COMPARISON OF PULLOUT STRENGTH OF CONCRETE WITH COMPRESSIVE STRENGTH OF CYLINDERS AND CORES, PULSE VELOCITY, AND REBOUND NUMBER," Journal of The American Concrete Institute, Vol. 77, No. 3, May-Jun 1980, pp. 161-170.

This paper presents comparisons of pullout strength of concrete with compressive strength of cylinders and cores, pulse velocity, and rebound number. The analysis of the test data shows that a significant correlation exists between the compressive strength of cylinders cured under standard conditions and the pullout strength of concrete. This is equally true for the compressive strength of cores drilled from concrete blocks.

1172. Myers, J. and Dubberke, W., "IOWA PORE INDEX TEST, '' Intrm Rpt., Iowa Department of Transportation Division of Highways, Jan 1980, pp. 4.

The objective of the investigation was the development of a test that would readily identify the potential of an aggregate to cause D-cracking because of its susceptivity to critical saturation. A Press- Ur-Meter was modified by replacing the air chamber with a one-inch diameter plastic tube calibrated in milli-. It was concluded that the pore index was sufficiently reliable to determine the D-cracking potential of limestone aggregates in all but a f e w cases where marginal results were obtained. Consistently poor or good results were always in agreement with established service records or concrete durability testing. In those instances where marginal results are obtained, the results of concrete durability testing should be considered when making the final determination of the D-cracking susceptibility of the aggregate in question. The following applications for the pore index test have been recommended for consideration: concrete durability testing be discontinued in the evaluation process of new aggregate sources with pore index results between 0-20 (Class 2 durability) and over 35 (Class 1) durability; composite aggregates with intermediate pore index results of 20-35 be tested on each stone type to facilitate the possible removal of low durability stone from the production process; and additional investigation should be made to evaluate the possibility of using the test to monitor and upgrade the acceptance of aggregate from sources associated with D-cracking.

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1173. Ngab, A., "BEHAVIOR OF HIGH-STRENGTH CONCRETE UNDER SUSTAINED COMPRESSIVE STRESS," Cornell Univ., Ithaca, NY. Dept. of Structural Engineering, Feb 1980, pp. 217.

The behavior of plain high-strength concrete subjected to sustained compressive stress is reported. Time-dependent deformational and strength characteristics were investigated. A direct comparison was made to the behavior of normal-strength concrete subjected to similar relative stresses under the same environmental conditions. Deformational behavior related to moisture movements and internal progressive microcracking also was investigated. Sealed and unsealed concrete specimens were analyzed for internal microcracking after being subjected to short-term drying shrinkage and creep strains. Results indicate the following: (1) Time-dependent deformation is less for high-strength concrete than for normal-strength concrete; (2) The amount of internal progressive microcracking associated with short-term shrinkage and creep is considerably less in high-strength concrete than in normal-strength concrete; and ( 3 ) The creep- stress relation of high-strength concrete is linear over a larger range than that in normal-strength concrete. Results of an experimental program on the effect of sustained loading on compressive strength are described.

1174. Seyitaprasirt, P., "FACTORS AFFECTING THE RELATIONSHIP BETWEEN RATE OF LOADING AND MEASURED COMPRESSIVE STRENGTH OF CONCRETE," Magazine of Concrete Research, Vol. 32 No. 111, Jun 1980, pp. 79-88.

The effect of the free water, age and curing conditions upon the strength/loading-rate relationship of concrete, mortar and neat cement paste was studied. It was found that the moisture content at the time of testing was one of the most important factors influencing this relationship, but any variables such as age or curing regime which affect the internal structure of the solid phase also have an influence. The data obtained under the different loading methods indicated that, when a specimen made from cement paste is loaded at slower rates up to approximately one- third of its ultimate strength value, the resulting ultimate strength is increased. However, if a slower rate of loading is continued throughout the test, the ultimate strength is decreased significantly. This result is used to find the analytical form of the relationship between the stress-strain curve and strain rate of concrete and equations are proposed which closely agree with the existing data.

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1175. T e r r i e n , M., "ACOUSTIC EMISSION AND 'POST-CRITICAL MECHANICAL BEHAVIOUR' OF CONCRETE SUBJECTED TO TENSILE STRESS," B u l l e t i n de Lia ison des Lab des Ponts e t Chaussees, N105, J an 1 9 8 0 , pp. 65-72.

I n s t r u c t u r a l des ign the t e n s i l e s t r e n g t h of c o n c r e t e i s cons ide red t o be n i l and i t s f a i l u r e in s t an taneous . The s tudy described i n t h i s a r t i c l e was conducted t o confirm t h a t a ' p o s t - c r i t i c a l ' behaviour i s reached by conc re t e i n t e n s i l e stress w i t h a v i e w t o r each ing a better unders tanding of t h e behaviour o f c o n c r e t e i n f l e x u r a l stress. T h i s s tudy i s divided i n t o two parts: (1) t e n s i l e tes ts a t a c o n s t a n t ra te of deformation. These tes ts showed t h a t a p o s t - c r i t i c a l behaviour could be o b t a i n e d w i t h w e t c o n c r e t e and t h a t t h e l i n e a r mechanics of f a i l u r e cou ld no t e x p l a i n t h i s behaviour . I t was a l s o no ted t h a t , f o r a s imi la r mix des ign , dried c o n c r e t e had a h i g h e r f a i l u r e stress and a lower Young's modulus t h a n t h e cor responding w e t concrete; ( 2 ) s tudy of a c o u s t i c emiss ion under stress. The spectrum a n a l y s i s of a c o u s t i c phenomena under l o a d showed t h a t it i s p o s s i b l e t o d i s t i n g u i s h several t y p e s o f spectrum, which leads t o proposing a f i s sL . r a t ion mechanism. Two stress l i m i t s corresponding t o t he onse t of t h e two phenomena w e r e determined: t h e f irst w a s t h e breakdown of cohesion between aggrega te s e n d mor ta r , t h e second w a s i n t e r - a g g r e g a t e c racking . I t w a s a l s o observed that cracking occurred in several zones of the sample.

1176 . Tognon, G . and U r s e l l a , P . e t al.. , " D E S I G N AND PROPERTIES OF CONCRETES WITH STFLENGTH OVER 1500 kgf/cm**2," Jou rna l of The American Concrete I n s t i t u t e , Vol. 7 7 , No. 3 , May-Cun 1 9 8 0 , pp. 171-178.

Very high s t r e n g t h conc re t e s (VHSC) having a compressive s t r e n g t h over 1 5 0 0 k:fg/cm**2 were made. T h i s r e s u l t was reached b y u s i n g high s t r e n g t h p o r t l a n d cement, ground q u a r t z , and s i l i c e o u s aggregates, and by s u b j e c t i n g the c o n c r e t e s t o a two- stage low and h igh p r e s s u r e steam c u r i n g . The VHSC have a high modulus of e l a s t i c i t y , a low Po i s son ' s r a t i o , and an almost l i n e a r s t r e s s - s t r a i n curve up t o t h e maximum load . Reinforced cor ,c re te beams ( 0 . 1 0 X 0. 20 X 2. 00 m) having d i f f e r e n t re inforcement r a t i o s (from 0 . 87 t o 8. 8 8 p e r c e n t ) w e r e manufactured us ing

VHSC and an o rd ina ry c o n c r e t e as, a r e f e r e n c e . These beams w e r e t e s t e d i n f l e x u r e by observ ing t h e t r e n d s o f t he c u r v a t u r e as a func t ion of t h e a p p l i e d moment.

7 6

1981

1177. Alford, N. M., "THEORETICAL ARGUMENT FOR THE EXISTENCE OF HIGH STRENGTH CEMENT PASTES," Cement and Concrete Research, Vol. 11, No. 4, 1981, pp. 605-610.

The purpose of this paper is to determine whether the volume of porosity or whether the size of individual pores is responsible for controlling strength in cement paste. The suggestion given here, and recently by Birchall, Howard and Kendall, is that the conventional strength - total porosity relation is largely fortuitous. Emphasis is placed upon the maximum pore size as being responsible for the strength characteristics of cement paste.

1178. Carrasquillo, R. L. and Slate, F. 0. et al., "MICROCRACKING AND BEHAVIOR OF HIGH STRENGTH CONCRETE SUBJECT TO SHORT-TERM LOADING," Journal of The American Concrete Institute, Vol. 78, No. 3, May-Jun 1981, pp. 179-186.

The progressive microcracking of concretes with uniaxial compressive strengths from 31 to 76 MPa was studied quantitatively and compared. Cracks were identified by types as related to unstable behavior and progressive failure. Differences in behavior between high strength concrete and normal concretes, including differences in stress-strain response and mode of failure, were related to and explained by differences in microcracking.

1179. Carrasquillo, R. L. and Nilson, A. H. et al., "PROPERTIES OF HIGH STRENGTH CONCRETE SUBJECT TO SHORT-TERM LOADS," Journal of The American Concrete Institute, Vol. 78, No. 3, May-Jun 1981,

Results are summarized from an experimental investigation of the properties of high strength concrete. The materials tested were produced using Type I portland cement, gravel or crushed limestone coarse aggregate, sand from a local deposit, and for some mixes a water-reducing retarding admixture.

77

1180. Cook, D . J. and C h i n d a p r a s i r t , E . , "INFLUENCE OF LOADING HISTORY UPON THE TENSILE: PROPERTIES OF CONCRETE, '' Magazine o f Concre t e Research, V o l . 33, No.116, S e p t 1981, pp. 154-160.

I n t h i s paper, t he i n f l u e n c e o f s u s t a i n e d and c y c l i c l o a d regimes upon t h e ter.sile p r o p e r t i e s o f c o n c r e t e a n d paste is r e p o r t e d . The r e s u l t s i n d i c a t e t h a t p r i o r l o a d i n g o f any form r e d u c e s t h e s t r e n g t h of c o n c r e t e on r e l o a d i n g . For paste, however, t h e effect i s n o t so marked and a s l i g h t increase i n s t r e n g t h i s o b s e r v e d a f t e r c y c l i c p r e l o a d i n g .

1181. Ghosh, R. S. and Timusk, J. , "CREEP O F FLY ASH CONCRETE," J o u r n a l o f t h e American C o n c r e t e I n s t i t u t e , V o l . 78, No. 5, Sep-Oct 1981, PF. 351-357.

T h e effect o f d i f f e r e n t q u a l i t i e s o f f l y ash and d i f f e r e n t ash t o cement r a t i o s c n creep, s h r i n k a g e , and modulus o f e l a s t i c i t y f o r c c n c r e t e s w i t h 20 MPa and 55 MPa compress ive s t r e n g t h s w a s d e t e r m i n e d . R e s u l t s w e r e compared w t i h t h o s e f o r r e f e r e n c e c o n c r e t e s o f e q u a l w o r k a b i l i t y and 3- o r 28-day s t r e n g t h s . Compared t o r e f e r e n c e c o n c r e t e s , it w a s found t h a t c o n c r e t e s u s i n g f l y a s h o f good q u a l i t y had e q u i v a l e n t modulus o f e l a s t i c i t y v a l u e s and s i g n i f i c a n t l y lower creep and s h r i n k a g e .

1182. HSU, T . T . C, "FATIGUE O F PLAIN CONCRETE," J o u r n a l o f The American C o n c r e t e I n s t i t u t e , Vol . 78, No. 4 , J u l - Aug 1981, pp. 292-305.

T h i s paper p r e s e n t s a g e n e r a l f o u r - v a r i a b l e r e l a t i o n s h i p f o r p r e d i c t i n g the f a t i g u e s t r e n g t h of c o n c r e t e . Based on the r e l a t i o n s h i p , two e q u a t i o n s are p roposed f o r t h e p r e d i c t i o n of f a t i g u e s t r e n g t h of c o n c r e t e , one f o r t h e h i g h - c y c l e f a t i g u e and one f o r low-cycle f a t i g u e . These e q u a t i o n s have been s u b s t a n t i a t e d by compress ive and f l e x u r a l tests r e p o r t e d i n l i t e r a t u r e .

1183. Lawrence, C. D . , "DURABILITY O F CONCRETE: MOLECULAR TRANSPORT PROCESSES AND TEST METHODS," Tech R e p Cem Concr Assoc 5 5 4 , J u l 1981, pp. 2 4 .

R e v i e w s o f mechanisms o f c o n c r e t e d e t e r i o r a t i o n i n aggressive env i ronmen t s are p r e s e n t e d , i n d i c a t i n g the l i k e l y r a t e - c o n t r o l l i n g t r a n s p o r t p r o c e s s e s and e s t i m a t i n g t h e speeds of d e t e r i o r a t i o n . A d i s c u s s i o n o f t es t methods

78

involving transport phenomena is given in the light of requirements for predicting durability from basic material properties. Diffusion measurements employing gases are measurements which are both relevant to durability problems and relatively easily carried out. The diffusion of water vapor from saturated specimens appears to be a rate-determining step in many durability problems.

1184. Malhotra, V., "EFFECT OF REPEATED DOSAGES OF SUPERPLASTICIZERS ON SLUMP, STRENGTH AND FREEZE-THAW RESISTANCE OF CONCRETE," Materiaux et Constructions, Vol. 14, No. 80, Mar 1981, pp. 79-89.

When added to concrete, plasticizers markedly increase its slump characteristics, but this increase is only temporary. In practice it is sometimes necessary to renew the addition of plasticizer in order to maintain the increase in slump. This article presents the results of an experimental study carried out with a view to determining the effects of repeated additions of plasticizer on the workability, strength and durability of concrete. These results show that large increases in slump can be maintained for several hours by adding a second dose. Except in one case, the addition of a third dose did not appear desirable. Repeated additions of plasticizer containing sulphonated melamine and naphthalene led to substantial losses of entrained air content in concrete; but the reverse was observed in the case of concrete to which a plasticizer containing lignosulphonate was added. Loss of entrained air has the effect of lowering the performance of concrete subjected to frost sensitivity tests.

1185. Ngab, A. S. and Nilson, A. H. et a l . , "SHRINKAGE AND CREEP OF HIGH STRENGTH CONCRETE," Journal of the - ~-

American Concrete Institute, V o l . 78, No. 4, Jul-Aug 1981,

Results of an experimental program on the time- dependent deformation and sustained load strength of high strength concrete are presented. Comparison with normal strength concrete under similar conditions indicates significant differences which should be accounted for in design. Sealed and unsealed specimens were subjected to uniaxial compressive stress for load period up to 90 days. The main variables investigated included concrete strength, conditions of drying, age at first loading, intensity of load, and duration of load.

79

1186. O z y i l d i r i m , H . and S p r i n k e l , M . , " I N V E S T I G A T I O N O F CONCRETE MIXTURES INCORPORATING HOLLOW PLASTIC MICROSPHERES," F i n a l R p t . , V i r g i n i a Highway C T r a n s p o r t a t i o n Resea rch Counc i l , J u l 1981, pp. 35.

T h i s s t u d y i n v e s t i g a t e d t h e p o t e n t i a l o f ho l low p l a s t i c m i c r o s p h e r e s , HPM, f o r p r o v i d i n g non-a i r - e n t r a i n e d p o r t l a n d cement c o n c r e t e r e s i s t a n c e t o damage from c y c l e s o f f r e e z i n g and thawing . I n the s t u d y , a m i x t u r e w i t h a n a i r - e n t . r a i n i n g a g e n t ( v i n s o l r e s i n ) w a s u s e d as the c o n t r o l f o r comparison w i t h t h r e e e x p e r i m e n t a l mixtures--one w i t h HPM, one w i t h s u p e r water r e d u c e r s (SWR) and HPM, and one w i t h f l y ash a n d HPM. HPM m i x t u r e s a t d o s a g e s o f 1.5% o r more by weight o f cement e x h i b i t e d s a t i s f a c t o r y r e s i s t a n c e t o damage from c y c l e s of f r e e z i n g and thawing . M i x t u r e s w i t h SWR and HPM e x h i b i - t e d low d u r a b i l i t y f a c t o r s and f a i l ed the a c c e p t a n c e c r i t e r i o n r e q u i r i n g a d u r a b i l i t y f a c t o r o f 60 o r more. C o n c r e t e w i t h f l y ash and HPM d i s p l a y e d d u r a b i l i t y f a c t o r s comparable t o t h o s e o f m i x t u r e s w i t h t h e same d o s a g e s o f HPM. However, t h e weight l o s s e s o f f l y ash m i x t u r e s w e r e higher t h a n t h o s e o f comparable m i x t u r e s . T o d e t e r m i n e t he c a u s e o f low d u r a h i l i t y f a c t o r s i n m i x t u r e s w i t h SWR and HPM, spec imens were examined u s i n g a n o p t i c a l microscope and s c a n n i n g e l e c t r o n mic roscope . I t w a s found t h a t the paste o f t h e m i x t u r e w i t h o u t t h e SWR c o n t a i n e d numerous w e l l - d i s t r i b u t e d HPM v o i d s . The paste o f m i x t u r e s w i t h t h e SWR and t h e s a m e dosage o f HPM c o n t a i n e d f e w HPM v o i d s d i s t r i b u t e d t h r o u g h o u t , b u t d id have c o n c e n t r a t i o n s o f HPM a t t h e u n d e r s u r f a c e o f t he aggregates. (FHWA)

1187 . Poppe, J. , "FACTORS AFFECTING THE D U R A B I L I T Y OF CONCRETE BRIDGE DECKS: SUMMARY, C a l i f o r n i a Department o f T r a n s p o r t a t i o n D i v i s i o n o f T r a n s p o r t a t i o n Fac i l i t i e s Design, F i n a l Rpt . , J a n 1981,

W i t h t h e o b j e c t i v e o f d e t e r m i n i n g f a c t o r s w h i c h c o n t r i b u t e t o c r a c k i n g o f c o n c r e t e bridge decks, p r o j e c t s w e r e u n d e r t a k e n t o exp:Lore t he effects o f d i f f e r e n t c o n c r e t e s t r ike o f f machines , effects of d i f f e r e n t t i m i n g of a p p l i c a t i o n o f f i n i s h f l o a t i n g a rd t e x t u r i n g , effects o f d i f f e r e n t methods and t i m i n g of c o n c r e t e c u r i n g , and effects o f d i f f e r e n t water c o n t e n t s i n t he c o n c r e t e . V a r i a t i o n s i n t he amount and l o c a t i o n o f t he t o p l a y e r o f deck l o n g i t u d i n a l r e i n f o r c i n g steel w e r e i n v e s t i g a t e d . Reinforcement p l a c i n g and s u p p o r t t e c h n i q u e s r e s u l t i n g i n a f l e x i b l e m a t w e r e compared t o t h o s e r e s u i l t i n g i n a r i g i d m a t . F l e x i b l e forms, a b s o r b e n t forms,. and forms w i t h l a rge gaps were compared w i t h t i g h t , : r i g i d forms. Ef fec ts

80

of air entrainment and a water reducing agent were investigated. The effects of thickening decks were studied, as were the advantages of using shrinkage compensated cement in the deck concrete. The effects of traffic were evaluated. Effects on the quality of the decks were related to abrasion loss of the deck surfaces, the friction factor of the deck surfaces, and the amount of cracking which developed in the decks. numerical comparisons of cracking between the various decks studied. The planned variables had little or no effect on abrasion loss or friction factor. Deck cracking was affected more by timing and quality of cure than by any other variable.

A crack index was developed to permit

1188. Ramakrishnan, V. and Coyle, W. V., "SUPERPLASTICIZED CONCRETE FOR REHABILITATION OF BRIDGE DECKS AND HIGHWAY PAVEMENTS,'' Department of Civil Engineering, South Dakota School of Mines and Technology, Rapid City, SD, Jan 1981, pp. 262.

The object of this research was to develop guidelines for assuring the trouble-free placement of tough, high-strength, high-density, durable concrete for bridge deck construction through the use of superplasticizers and steel fibers. The study was made in t w o phases. The first investigated the basic properties of concrete made with superplasticizers through the use of experimental mixtures conforming to the requirements dictated by statistically valid factorial designs, so that analysis of variance could be used in the evaluation. The second phase extended the findings into an evaluation of superplasticized concretes containing steel fibers. This report describes the first phase study of the statistical evaluation of superplasticized concrete properties. Two mixes, one with medium workability and high cement content suitable for bridge deck replacement and another with high workability suitable for structural and pavement concrete were selected for intensive study. For these mixes, properties of the fresh concrete (slump, vebe time, flow table spread, air content, initial and final setting times) are reported. The effects of retempering are described. The influence of three types of cements on the properties of plastic and hardened concrete is explained. are presented: compressive strength, tensile strength, flexural strength, static modulus of elasticity, dynamic modulus of elasticity, pulse velocity, and dry unit weight at 1, 3, 28, and 90 days curing. The selected concretes had high durability and satisfactory resistance against de-icer scaling.

Complete results of the following tests

81

1189. Salah el Din, A. S. and Lovegrove, J. M., "GAUGE FOR MEASURING LONG-TERM CYCLIC STRAINS ON CONCRETE SURFACES, I' Magazine of Concrete Research, Vol. 33, No.115, Jun 1981, pp. 123-127.

The theory and construction of a gage for measuring long-term cyclic strains on concrete surfaces is presented. The gage transforms axial concrete strains to smaller bending strains by means of a formed metal strip. Calibration of the gage shows that it is capable of reducing the concrete strains by a factor of about 25. The gage performs in a stable manner and an application to long-term strain measurement on a number of concrete beams repeatedly loaded at 1 Hz during a period of about two years is described.

1190. White, R. and Taylor, M. et al., "MORE ECONOMICAL BUT EQUALLY EFFECTIVE INTERNALLY SEALED CONCRETE," Federal Highway Administration Office of Research and Development, Final Rpt., Dec 1981, pp. 147.

Wax beads of several lower melting, lower cost wax blends can seal concrete as effectively as the paraffin-montan wax beads currently used in internally sealed concrete bridge decks, without affecting other important properties of the concrete. Savings of 5 to 25% in raw material costs can be expected to lower the cost of wax beads by approximately 5 to 20%. Since the minimum temperature required for melting the wax beads is about 25 deg F (14 deg C) lower than for the current beads, the cost of heating a bridge deck to achieve effective sealing should be reduced by approximately 15%. Beads of two formulations: 10% montan wax, 15% firbark wax, 75% paraffin 140/142 (FMP), and 5% stearic acid, 20% hydrogenated tallow, 75% paraffin 150/152 ( S T P ) , were produced in pilot plant quantities and were evaluated on two field tests. Damage to the beads during extended mixing of the concrete was suspected to be one of the causes of low strength and poor resistance to scaling of the test slabs in the first test. Some blocking of the lower melting beads at temperatures between 100 and 110 deg F (38 and 43 deg C) occurred during production in hot weather or storage for long times in warm locations. Coating the beads with 10% cement restored them to a free-flowing condition. Chlorides permeability of the slab containing STP beads was very low, equivalent to that of the best laboratory batches, even though wax content was reduced from 3% to 2% by weight. Chlorides permeability of the slab containing 2% of FMP wax beads was approximately

82

e q u i v a l e n t t o t h a t of l a b o r a t o r y batches c o n t a i n i n g 1.5 t o 3% of t h e c u r r e n t paraff in-montan wax beads, b u t n o t as low as f o r t he s l ab c o n t a i n i n g STP beads.

1191. Woelf l , G. and McNerney, M. e t a l . , "FLEXURAL FATIGUE OF POLYMER CONCRETE, 'I Cement, Concrete , and Aggregates, Vol. 3 No. 2, 1981, pp. 84-88.

T h i s paper descirbes modulus o f r u p t u r e and f l e x u r a l f a t i g u e t e s t i n g performed on beam specimens made of S i l i k a l polymer c o n c r e t e and c o u r s e aggregate. T e s t r e s u l t s i n d i c a t e t h a t modulus o f r u p t u r e o f polymer c o n c r e t e i n c r e a s e s w i t h i n c r e a s i n g r a t e of l o a d i n g s imi la r t o p o r t l a n d cement c o n c r e t e . F a t i g u e t es t r e s u l t s show good c o r r e l a t i o n w i t h a mathematical e x p r e s s i o n r e l a t i n g p r o b a b i l t y o f s u r v i v a l w i t h stress level and number o f c y c l e s t o f a i l u r e . T h i s e q u a t i o n w a s developed and used by o t h e r i n v e s t i g a t o r s f o r p o r t l a n d cement c o n c r e t e . T e s t r e s u l t s i n d i c a t e t h a t f requency o f l o a d i n g i n f l u e n c e s t he f a t i g u e l i f e o f polymer c o n c r e t e , b u t a s h o r t rest p e r i o d w i t h i n each l o a d i n g c y c l e probably does n o t . F u r t h e r f a t i g u e s t u d y i s recommended i n t h e pape r .

1192 . Z i e l i n s k i , A. J. and Reinhard, H . W . e t a l . , "EXPERIMENTS ON CONCRETE UNDER REPEATED UNIAXIAL IMPACT TENSILE LOADING, Mater iaux e t C o n s t r u c t i o n s , Materials and S t r u c t u r e s , Vo1.14, No.81, May-Jun 1981, pp. 163-169.

The f a t i g u e behav io r of c o n c r e t e w a s a new aspect i n t h e expe r imen ta l program focused on t h e behav io r of c o n c r e t e s u b j e c t e d t o u n i a x i a l impact t e n s i l e l oad ing . T h e i n f l u e n c e o f water-cement r a t i o , cement c o n t e n t , specimen humidi ty , l o a d i n g / c a s t i n g d i r e c t i o n and compressive s t r e n g t h upon t h e impact f a t i g u e t e n s i l e s t r e n g t h o f c o n c r e t e w a s s t u d i e d . The phenomenon observed are d i s c u s s e d w i t h t h e a id o f f r a c t u r e mechanics concep t s .

8 3

1982

1193. Bazant, Z. and Raftshol, W. J., "EFFECT OF CRACKING IN DRYING AND SHRINKAGE SPECIMENS," Cement and Concrete Research, Vol. 12, No. 2, Mar 1982, pp. 209-226.

The significance of cracking and microcracking caused by nonuniform drying shrinkage of test specimens is analyzed. Graphs for the maximum admissible rate of change of environmental humidity, calculated from both linear and nonlinear diffusion theories, are provided. The spacing and width of parallel cracks due to drying are estimated from fracture mechanics considerations.

1194. Beams, G. W. Jr. and Gerstle, K. H. et al., "RESPONSE OF CONCRETE TO CYCLIC BIAXIAL COMPRESSIVE LOADS," Preprints - 1982 ASCE National Convention, Las Vegas, NV, 1982, pp. 14.

Complex structural analysis through the use of computer based methods has developed rapidly in recent years to include structures that are subjected to multiaxial loading, such as concrete ocean vessels, prestressed plates and shells, offshore oil plateforms, and nuclear containment vessels. Analysis of such structures requires a thorough understanding of the response of concrete when subjected to multiaxial stress states so that constitutive models for concrete may be developed. The research project reported in this paper was conceived to understand and gain insight into the response of plain concrete subjected to cyclic biaxial compressive loading, and to obtain data which would contribute to the base on which constitutive modeling of concrete behavior will be founded. Results are presented in terms of deformational response and strength response.

1195. Blackie, A., "THE INFLUENCE OF PFA ON THE PROPERTIES OF STRUCTURAL CONCRETE., Proceedings of the International Symposium on the Use of PFA in Concrete, Vol. 1, April 14-16, 1982, pp. 289-299.

This article examines the properties of structural concrete containing pfa in the light of British standard CP110. The following aspects are discussed: durability; structural behaviour; concrete compressive strength; quality control; sulphate resistance; pozzolanicity; colour; and alkali silica reaction.

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1196. Carpinteri, A., "SENSITIVITY AND STABILITY OF PROGRESSIVE CRACKING IN PLAIN AND REINFORCED CEMENT COMPOSITES," Intl J of Cement Composites & Lightweight Concrete, Vol. 4 No. 1, Feb 1982, pp. 47-56.

A general formulation of the problem of sensitivity and stability of fracture in plain and reinforced cement composites is presented. It is shown how such phenomena are subjected to very similar laws of scale. The stability of the fracturing process is due to a sufficiently high degree of redundancy in the system. The adjunctive elements, producing such redundancy, are usually fibre or bar reinforcements. Two particular cases are eventually considered: 1. Reinforced concrete beam element, subjected to bending moment; 2. Masonry wall, subjected to eccentric axial force. Their stability conditions are discussed with reference to progressive cracking.

1197. Chatterji, S., "PROBABLE MECHANISMS OF CRACK FORMATION AT EARLY AGES OF CONCRETES: A LITERATURE SURVEY," Cement and Concrete Research, Vol. 12, No. 3, 1982, pp. 371-376.

Recent fluorescent microscopic investigations of concrete structures have revealed that cracking can occur inside the bulk of concrete structures with or without any visible sign on the outer surfaces. It is also indicated that under certain conditions cracks can form shortly after or even before the outer form- works are removed. The relevant literature has been critically surveyed to identify the probable mechanisms of crack formation at early ages of concrete structures.

1198. Coleman, S. and Maage, M. et al., "LOW POROSITY HIGH STRENGTH COONRETE FOR HIGHWAY BRIDGE DECKS," Final Rpt., Purdue University/Indiana State Highway Corn JHRP, 1982, pp. 306.

Premature failure of concrete bridge decks stemming from chloride-induced corrosion of reinforcing steel constitutes a major problem. This study relates to the possibility of substituting 'low porosity' concrete (made with gypsum-free portland cement) for conventional concrete on bridge decks. Relevant properties of certain experimental low-porosity concretes, formulated with and without flyash, were determined experimentally and compared with the corresponding properties of conventional bridge deck concrete formulations and also with those of Iowa-type dense concrete mixtures. Conventional concrete was

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shown t o be d e f i c i e n t i n t.erms of long-term r e s i s t a n c e t o t h e p e n e t r a t i o n o f c h l o r i d e ions , and i n terms of ma in ta in ing steel pass iva t . ion once t h e c h l o r i d e had p e n e t r a t e d . Measured c h a r a c t e r i s t i c s of t h e dense c o n c r e t e s were g e n e r a l l y s u p e r i c r t o the convent iona l bridge deck mixes, b u t g r o s s l y i n f e r i o r t o t h e low p o r o s i t y c o n c r e t e s . formula ted t o produce f lowing c c n c r e t e of good w o r k a b i l i t y a t w : c 0.28. S t r e n g t h s developed were i n t h e range 10,000-13,000 psi , and. these c o n c r e t e s showed e x c e l l e n t f r e e z i n g r e s i s t a n c e , reduced d r y i n g shr inkage , reduced carbonat ion , and a t i g h t po re s t r u c t u r e . T h e resistance t o p e n e t r a t i o n of c h l o r i d e w a s good. Equal ly important , because of the high i n h e r e n t a l k a l i n i t y of the c o n c r e t e p o r e s o l u t i o n s of low p o r o s i t y conc re t e , p a s s i v a t i o n appeared t o be main ta ined throughout t h e moni tor ing p e r i o d , even i n t h e p re sence of large c h l o r i d e c o n c e n t r a t i o n s . p o r o s i t y c o n c r e t e showed t h e b r i t t l e behavior expec ted of any h igh s t r e n g t h conc re t e , b u t t h i s should be no p r a c t i c a l problem i n v i e w of t h e d u c t i l i t y provided by t h e c o n s i d e r a b l e percentage o f s . t e e l i n most b r i d g e deck des igns .

Low p o r o s i t y c o n c r e t e cou ld be

Low

1199 . E l - J a z a i r i , B. , "RAPID REPAIR OF CONCRETE PAVINGS," Concrete , V o l . 16 , N o . 9, Sep 1982, pp. 12-15.

T h e a u t h o r d i s c u s s e s t h e p r o p e r t i e s of t h e s i n g l e component magnesium phosphate cement (mpc) p a t c h i n g product , febset-45, e x p l a i n i n g t h e f e a t u r e s l e a d i n g t o t y p i c a l a p p l i c a t i o n s . The material i s a chemical s e t t i n g cement mainly of magnesia, a mixture of phosphates blended w i t h f i n e aggrega te s . When it i s added t o t h e gauging water, an exothermic r e a c t i o n produces mainly s t r u v i t e , s e t t i n g i n about 15 minutes and hardening t o a s u f f i c i e n t s t r e n g t h 20n/mm squared t o be able t o t a k e heavy t raff ic : w i t h i n one hour . Normal s t r e n g t h g a i n can be o b t a i n e d i n adve r se weather by e i t h e r h e a t i n g o r c o o l i n g t h e gauging w a t e r . T h e pe rcen tage of w a t e r added i s c r i t i c a l a s t o o much produces s e g r e g a t i o n arid b l eed ing . Examples are g iven of t h e use o f t h e m a t e r i a l i n t h e r e p a i r o f roads , a i r p o r t s and i n d u s t r i a l f i loors ( i n c l u d i n g c o l d s t o r e s ) . Good flow c h a r a c t e r i s t i c s permi t t h e material t o be used f o r r e p a i r s of up t o 200mm wi thout the need of v i b r a t i o n . Because of i t s good bonding characterist ics, no pr imer i s needed on any r e p a i r work. (Author/TRRL)

8 6

1200. Fagerlund, G., "ON THE CAPILLARITY OF CONCRETE," Nordic Concrete Research, Article 1, Publication No. 6, Dec 1982, pp. 1-20.

The kinetics of water absorption in concrete can be described approximately by three coefficients, m, k and (epsilon of e). In the article a simple method for determination of those coefficients is suggested. Experimental results indicate relatively well-defined relations between the capillary porosity and the coefficients m and k. Thus, all capillary constants can be evaluated theoretically once the cement content, the w/c-ratio and the degree of hydration are known. The effect of the initial moisture condition of the concrete can also be evaluated theoretically. Experiments confirm that the air-voids in concrete have very little effect on the absorption process.

1201. Fagerlund, G., "PREDICTING THE SERVICE LIFE OF CONCRETE STRUCTURES," Second Engineering Foundation Conference Related to Cement and Concrete, Jul 25-30 1982, pp. 187-198.

It is suggested that the qualitative but widely used concept 'durability' should be abandoned and be replaced by the quantitative concept 'service life'. If this is tc be meaningful, however, we need reliable methods for service life prediction. Such methods would enable us to achieve much more rational designs than we do today; consideration could also be given to such fundamental factors as the required service life, the consequences of failure due to lack of durability and the cost of maintenance and repair.

1202. Franklin, R. E., "EFFECT OF PULVERIZED FUEL ASH ON THE STRENGTH OF PAVEMENT-QUALITY CONCRETE," Transportation and Road Research Lab, 1982,

To assess possible applications in concrete road construction a study has been made of the effects on the strength of pavement-quality concrete of using a selected pulverized fuel ash as a cement-replacement material. The development of indirect-tensile, flexural, and compressive strengths has been followed from an age of 18 hours to 1 year on various concrete mixtures containing up to 180 kg/m**3 of ash. Values of strain capacity have been determined by two methods.

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1203. Ghosh, R. K . and S e t h i , K. L . et: a l . , "LABORATORY STUDIES ON LEAN CEMENT-FLY ASH CONCRETE AS CONSTRUCTION MATERIAL," Hfighway Research B u l l e t i n ( N e w D e l h i ) , No. 19, 1982, pp. 13-26..

The paper deals w i t h 1abora t : ) ry i n v e s t i g a t i o n s carried o u t t o f i n d t he p o s s i b i L i t y o f p a r t r ep lacemen t o f f i n e aggregate by f l y a s h i n l e a n cement c o n c r e t e mixes and s a v i n g i n t h e c o s t effected t h e r e b y w i t h o u t any impairment i n t he s t r e n g t h of c o n c r e t e . I t a l s o deals w i t h d i f f e r e n t e n g i n e e r i n g p r o p e r t i e s o f l e a n cement c o n c r e t e such as f l e x u r a l s t r e n g t h , modulus o f e l a s t i c i t y , Po i s son ' :; r a t i o , t e n s i l e s t r e n g t h , s t r e s s - s t r a i n r e l a t i o n s h i p , f a t i g u e e tc .

1204. Gress, D . , ''AN INVESTIGATION OF THE EFFECT OF AGGREGATE ON CONCRETE COMPRESSIVE STRENGTH," N e w Hampshire U n i v e r s i t y Department of C i v i l E n g i n e e r i n g , F i n a l R p t . , Mar 1982, pp. 39.

The o b j e c t o f t h i s s t u d y w a s t o d e t e r m i n e t h e s i g n i f i c a n c e of v a r i a t i o n i n t h e p l a s t i c p r o p e r t i e s of c o n c r e t e as d e n o t e d by c o n s t r u c t i o n r e c o r d s of t h e N e w Hampshire Department o f P u b l i c Works and H i g h w a y s ; t o i s o l a t e t h o s e variables t h a t a l s o have a n affect on the ha rdened p r o p e r t i e s of c o n c r e t e ; t o d e t e r m i n e i f r i g i d c o n t r o l o f a g g r e g a t e g r a d a t i o n c o u l d be j u s t i f i e d by r e q u i r i n g t h e aggregate t o be separate i n t o several s i z e f r a c t i o n s p r i o r t o field b a t c h i n g i n o r d e r t o p roduce a d u r a b l e supe : r ior c o n c r e t e ; and t o e v a l u a t e t he microwave oven t e c h n i q u e of d e t e r m i n i n g t h e water-cement r a t i o o f p l a s t . i c c o n c r e t e . T h e s t a t i s t i c a l a n a l y s i s o f t e n y e a r s o f c o n c r e t e c o n s t r u c t i o n data showed t h a t some s o u r c e s of c o a r s e aggregate had n o t m e t the i r e x p e c t e d s t r e n g t h s and t h a t c o n c r e t e s made o f t y p e I1 cements were found t o p roduce compress ive s t r e n g t h s abou t e i g h t p e r c e n t h i g h e r t h a n c o n c r e t e made o f t y p e I cements. F i n d i n g s from l a b o r a t o r y t e s t i n g i m p l i e d t h a t improved d u r a b i l i t y may be o b t a i n e d by r e q u i r i n g t i g h t c o n t r o l on t h e c o a r s e aggregate g r a d a t i o n b y s e p a r a t i n g it i n t o three s i z e f r a c t i o n s . The microwave t e c h n i q u e appears t o be a viable method of d e t e r m i n i n g t h e water cement r a t i o o f p l a s t i c c o n c r e t e .

1205. H j o r t , L . , "MICROSILICA I N CONC:XETE, Nc,rdic C o n c r e t e Research, No. 1, D e c 1982, pp.18.

M i c r o s i l i c a i s a by-product from t h e f e r r o a l l o y s i n d u s t r y . I t c o n s i s t s of e x t r e m e l y f i n e , amorphous s i l i c a pa r t i c l e s . M i c r o s i l i c a a f f e c t s t h e p r o p e r t i e s w

88

of fresh concrete, the pore size distribution and the hydration products formed during hydration, and hereby the mechanical properties and durability of the hardened cement based products. The literature on the properties of microsilica in concrete is reviewed. (Author) The members of the Nordic Concrete Federation are the Concrete Associations of: Denmark, Finland, Iceland, Norway and Sweden.

1206. Hughes, B. and Ghunaim, F., "AN EXPERIMENTAL STUDY OF EARLY THERMAL CRACKING IN REINFORCED CONCRETE,"

1982, pp. 18-24. Magazine of Concrete Research, Vol. 34 No. 118, Mar

Restrained volume changes in concrete can cause cracking before normal service loads are applied, since all concrete members undergo an early thermal cycle due to the heat of hydration. This mechanism of early thermal cracking is reviewed and an experimental laboratory investigation is described which tested the validity of the current proposals in BS 5337 for some different types, arrangements and amounts of reinforcement. Of the types of reinforcement investigated, the fabric was found, as expected, to give the best crack width control. It was confirmed that, provided a minimum ratio of reinforcement is present in reinforced concrete, thermal crack widths are a function of reinforcement ratio, reinforcement diameter, strength of concrete and bond strength between reinforcement and concrete.

1207. Huovinen, P., "AIR-PERMEABILITY OF CONCRETE," Nordic Concrete Research, Article 10, Publication No. 1, Dec 1982, pp. 1-17.

An apparatus for defining the air permeability of concrete is described and the air permeability of concrete is defined by measuring the volume flow rate of air through the samples with the apparatus. The specific permeation coefficient (D of s ) of concrete is calculated on the basis of the measured air volume. Eleven different types of concrete and the pressures of 1, 3 and 5 bar were examined at the tests. Other variables were temperature, the length of the sample and the age of the concrete. Concrete has no unambiguous value of air permeability. The values of the specific permeation coefficient which appeared at measurement are set in a wide range: (lo**-16) to (lo**-19) (m**2).

8 9

1 2 0 8 . Mindness, S . , "ACOUSTIC EMISSION AND ULTRASONIC PULSE VELOCITY O F CONCRETE," In t . l J of Cement Composi tes & Lightweight Concre t e , V o l . 4 N o . 3, Aug :1982, pp. 173- 179.

Both a c o u s t i c e m i s s i o n and u l . t r a s o n i c p u l s e v e l o c i t y measurements w e r e u s e d t o t r y t o m o n i t o r the s t r u c t u r a l i n t e g r i t y o f c o n c r e t e . Specimens i n t h e form o f 1 5 0 mm cubes w e r e l o a d e d m o n o t o n i c a l l y t o f a i l u r e , and a c o u s t i c e m i s s i o n and u l t r a s o n i c p u l s e v e l o c i t y w e r e measured s i m u l t a n e o u s l y . Four d i f f e r e n t c o n c r e t e mixes w e r e each tested a t ages up t o two y e a r s t o p r o v i d e a w i d e r a n g e of! c o n c r e t e s t r e n g t h s . The r e s u l t s i n d i c a t e d t h a t u l t r a s o n i c p u l s e v e l o c i t y measurements began t o show i n t e r n a l c r a c k i n g a t stresses o f a b o u t 33 t o 66 p e r c e n t o f t h e u l t i m a t e stress; t h i s method t h e r e f o r e appeared t o be more s e n s i t i v e t o damage t h a n ac0us t i . c e m i s s i o n s , which i n d i c a t e d severe c r a c k i n g o n l y a t a b o u t 8 0 t o 90 per c e n t o f t h e u l t i m a t e stress. However, b o t h u l t r a s o n i c p u l s e v e l o c i t y and a c o u s t i c e m i s s i o n seemed t o be affected by t h e age o f t h e c o n c r e t e . I t w a s conc luded t h a t , f o r a c o u s t i c e m i s s i o n t o h e u s e d as a r e l i ab le i n d i c a t o r o f c o n c r e t e damage, e x t e n s i v e work would have t o be done t o e s t a b l i s h a s t a n d a r d t e s t p r o c e d u r e .

1209. Montague, P . and Kormi, K . , "CONSTITUTIVE RELATIONSHIPS AND A FAILURE CRITERION FOR CONCRETE BASED ON FUNDAMENTAL MATERIAL PROPERTIES," Magazine of C o n c r e t e Research, V o l . 3 4 No. 1.18, Y a r 1982, pp . 35- 4 3 .

T h e f u n c t i o n a l s t r e s s - s t r a i n r e l a t i o n s h i p s o b t a i n e d by Kotsovos from h i s a p p l i c a t i o n o f r e g r e s s i o n a n a l y s i s t o empirical data are u s e d as t h e bas i s f o r a d e r i v a t i o n o f m u l t i a x i a l c o n s t i t - u t i v e r e l a t i o n s h i p s , f o r c o n c r e t e s u b j e c t e d t o compress ive stresses, which d i s t i n g u i s h between l o a d i n g and u n l o a d i n g . A model i s p r o p o s e d i n w h i c h i n t e r n a l c r a c k i n g i s accompanied ky a n i n t e r n a l t r a n s f e r o f e n e r g y firom t h e d e v i a t o r i c stress sys t em t o t h e spherical stress sys tem, r e s u l t i n g i n m o d i f i e d v a l u e s o f t h e effect ive i n t e r n a l spherical and shear stresses and o f t he shear s t r a i n . T h i s t r a n s f e r of ene rgy i s regarded as a n i r revers ible p r o c e s s which can o n l y take p l a c e d u r i n g l o a d i n g and i n t e r n a l crack p r o p a g a t i o n . T h e p roposed f a i l u r e c r i t e r i o n i s t h a t f a i l u r e of t h e ma te r i a l t a k e s p l a c e when, unde r any sys tem o f a p p l i e d c o n p r e s s i v e stresses, t h e i n t e r n a l shear stress reaches a un ique v a l u e e q u a l t o t h a t which e x i s t s a t f a i l u r e i n a u n i a x i a l l y compressed s o l i d c y l i n d r i c a l specimen of 1 0 0 mm diameter and 250 mm lengt -h . Fo r any o t h e r

9 0

general compressive stress state which generates a modified octahedral shear stress less than this unique value, the concrete will retain its load-bearing capacity.

1210. Noor, F. and Wijayasri, S., "MODELLING THE STRESS- STRAIN RELATIONSHIP OF STRUCTURAL CONCRETE," Magazine of Concrete Research, Vol. 34, No. 118, Mar 1982, pp. 25-34.

Recent research has led to an improvement in the properties of model reinforcement, but similitude of deformations, over the complete range of loading, and sheer strength has not been achieved. It is well known that a number of size effects are due mainly to the properties of microconcrete because, in comparison with structural concrete, this material is stronger in tension and more ductile in compression. As a result of a detailed investigation into the compressive to tensile strength ratio and the stress-strain relationship of various model concrete mixes, a new type of microconcrete has been produced. The new mix is gap-graded, some of the coarse sand particles being replaced by glass beads. It has been tried in a number of model beams with an over-all depth of 30 mm and has given useful results.

1211. Reinhardt, H. W., "CONCRETE UNDER IMPACT LOADING - TENSILE STRENGTH AND BOND," Heron, Vol. 27, No. 3, 1982, pp.48.

Uniaxial impact tensile tests on plain concrete were carried out with the aid of Split Hopkinson Bar equipment with stress rates of up to 60,000 N/mm**2 X (TIMES) s . Various concrete mixes were investigated under dry and wet conditions. The bond between reinforcing steel and concrete was studied in pull-out tests with short embedment length. Relations between compressive strength and tensile strength are given for various stress rates.

1212. Walker, H., "THE USE OF SULPHUR AS A RIGID BINDER AND FOR THE IMPREGNATION OF CONCRETE-STATE OF THE ART," Virginia Highway & Transportation Research Council, Nov. 1982, pp. 17.

Recent research has led to the development of durable modified-sulphur mortars, concretes, and coatings. All of the methods of using sulphur as a binder for rigid concrete rely 011 the reaction of one or more modifiers to stabilize, in the hardened state,

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a t least a p o r t i o n of t h e s u l p h u r i n i t s less b r i t t l e , less d e n s e form. The d u r a b i l i t y o f t he c o n c r e t e p roduced appears t o depend on t h e mod i fy ing sys t em u s e d . I n a l l cases the s u l p h u r must be heated t o a l i q u i d s t a t e t o react w i t h t h e m o d i f i e r and t o mix w i t h and c o a t t he aggregate and f i l l e r . Su lphur c o n c r e t e c a n d e v e l o p h i g h s t r e n g t h , a t t a i n s s t r e n g t h i n a f e w h o u r s , r e q u i r e s no special c u r i n g , resists acids and o r g a n i c l i q u i d s , has no known u n d e s i r a b l e r e a c t i o n s w i t h aggregates, and r e q u i r e s no l i m i t a t i o n on t h e ambient t e m p e r a t u r e a t t h e time of p l acemen t . When i t s u s e becomes economica l ly feasible, s u l p h u r c o n c r e t e w i l l be a n e x c e l l e n t m a t e r i a l f o r u s e i n pavement repairs and b r i d g e deck o v e r l a y s . F u r t h e r research is r e q u i r e d on c e r t a i n facets o f t he u s e of s u l p h u r c o n c r e t e . No d a t a are avai lable c o n c e r n i n g t h e r e a c t i o n , i f any, o f s u l p h u r c o n c r e t e w i t h a m o i s t a l k a l i n e sys t em s u c h as p o r t l a n d cement u n d e r weather c o n d i t i o n s . The r e a c t i o n s o f s u l p h u r c o n c r e t e w i t h aggregates fabricated from r e c y c l e d materials ae unknown. No data are available c o n c e r n i n g t h e par t ic le shape r e q u i r e d o f aggregates u s e d i n s u l p h u r c o n c r e t e , n o r i s there i n f o r m a t i o n on means o f s e c u r i n g s k i d r e s i s t a n c e o r on t h e a d h e r e n c e o f marking p a i n t .

1213. Weigler, H. and Dil lmann, R . , "CONCRETE MEMBERS UNDER FLEXURAL PULSATING LOAD - STRESS DISTRIBUTION I N THE FLEXURAL COMPRESSIVE Z O N E S , " Betonwerk und F e r t i g t e i l - Technik , V o l . 48, N o . 6, 1982, pp. 342-346.

T h e compress ive s t r e n g t h of c o n c r e t e u n d e r a x i a l compress ive p u l s a t i n g l o a d i s a d e q u a t e l y known. These character is t ic v a l u e s are n o t , however, v a l i d f o r t h e f l e x u r a l compress ive zone. I n o r d e r t o d e t e r m i n e t h e stress d i s t r i b u t i o n t h a t c o u l d b e e x p e c t e d t o d e v e l o p i n t h a t zone, t he s t r a i n e v o l u t i o n i n i n d i v i d u a l f ibres i n t h e c r o s s - s e c t i o n of t es t spec imens s u b j e c t e d t o e c c e n t r i c compress ive p u l s a t i n g l o a d w a s established. T h e same s t r a i n b e h v i o u r w a s t h e n r ep roduced i n spec imens s u b j e c t e d t o a x i a l compress ive p u l s a t i n g l o a d . From the l o a d s r e c o r d e d i n these t e s t s it w a s p o s s i b l e t o a s c e r t a i n t h e stress d i s t r i b u t i o n o v e r t he depth o f t he compress ive zone .

92

1983

1214. "PRODUCTION OF HIGH QUALITY CONCRETE IN SARAWAK WITH SPECIAL REFERENCE TO BATANG KEMENA BRIDGE SITE EXPERIENCES, 'I Concrete Institute of Australis's Eleventh Biennial Conference, Session 3: Recent Action, Sydney, Australia., 1983, pp. 11.

The Kemena bridge is the most recent of the Colombo Plan Aid bridges constructed in Sarawak with technical assistance provided by Australia, and is also the most sophisticated concrete structure, requiring a higher general standard of concrete work, and high strength concrete for the prestressed bridge superstructure. Investigations into local materials, laboratory testing and the subsequent site construction experienced, have proven that it is possible to use some of the local materials to produce a sound, high quality concrete, with an assessed upper limit of f'c = 50 mpa, although the shrinkage and creep for such concrete is relatively high. Consideration however has to be given to the type of (and variability in) gradings of the materials available, the low ph of the natural waters, the high ambient humidity, the relatively short life of the cement, and shortage of experienced local labour.

1215. Birchall, J. D., "CEMENT IN THE CONTEXT OF NEW MATERIALS FOR AN ENERGY-EXPENSIVE FUTURE," Technology in the 1990s: Developments in Hydraulic Cements, Proceedings of a Royal Society Discussion Meeting, London, England, Feb 16-17 1983, pp. 31-42.

Hydraulic cements are energy-cheap relative to other common materials, are manufactured on a large scale and, when mixed with water, form readily mouldable pastes that harden at low temperature. In a technological sense, such pastes can be regarded as inorganic 'plastics', but the types of article that can usually be fabricated from the cements has been restricted by the low tensile strength and fracture toughness of hardened cement pastes. Poor mechanical properties are not inherent in inorganic solids formed under mild conditions; mineral structures of biological origin can display relatively high strength and useful toughness as a result of microstructural features determined by biopolymers. Recent studies have shown that the low tensile properties of cement paste result from the presence of macroscopic pores. The elimination of such defects by the use of polymeric rheology modifiers gives unreinforced cement pastes a flexural strength of 150 MPa or more.

93

1216. Bromham, S. and Meadley, M., "STEAM CURING OF HIGH STRENGTH CONCRETE, 'I Symposium on Concrete 1983, the Material for Tomorrow's Demands, Institution of Engineers, Perth, Australia, 20-21 October 1983, Aug 1983, pp. 24-28.

The performance of high strength concrete which is steam cured to accelerate strength growth depends on many characteristics of the concrete, the environment and the steam curing cycle. When optimum strength gain is required, and this is the case for most of the steam cured concrete used by the CRB, the concrete mix design and the steam curing process need to be carefully evaluated to ensure that these strength levels will be consistently achieved and this will then result in the economical production of high standard precast concrete units.

1217. Brooks, J. and Wainwright, P., "PROPERTIES OF ULTRA-

Magazine of Concrete Research, 'Jol. 35, No. 125, Dec

Tests have been undertaken over a period of one year to compare the time-dependant properties of high- cement-content (500-730kg/m cubed) concretes with and without a superplasticizing admixture. containing the superplasticizer, there was an improvement in strength and modJlus of elasticity and a decrease in shrinkage, but there were increases in creep and swelling. The process of microcracking is postulated to be a contributing factor in shrinkage and in creep under drying conditions. (Author/TRRL)

HIGH-STRENGTH CONCRETE CONTAINING A SUPERPLASTICIZER, "

1983, pp. 205-213.

For mixes

1218. Buerge, T. A., "14,000 PSI IN 24 HOURS," Concrete International: Design and Construction, Vo1.5, No.9, 1983, pp. 36-41.

High strength concrete is considered to be concrete with a compressive strength higher than 6000 psi. An extremely strong and dense concrete can be produced with a 24-hour compressive strength higher than 14,000 psi with conventional methods of production, curing at room temperature, and cement-based binders and admixtures The binder is made of portland cement, silica fume, superplasticizer, and an alkali-free accelerator. Variations of the mix proportioning and corresponding test results are presented.

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1219 . Clark, C. R. and Johnston, D. W., "EARLY LOADING EFFECTS ON BOND STRENGTH," Journal of The American Concrete Institute, Vol. 80, No. 6, 1983, pp. 532-539.

An investigation was conducted to determine the effects of early loading on concrete bond with deformed steel reinforcement. Bond tests were conducted on identical beam end speciinens with a 4000 psi concrete mix using 60 ksi reinforcement. The 28 day ultimate bond strength and the concrete bond load- slip characteristics were compared for specimens loaded at one day and maintained for 27 days to specimens only loaded at 28 days and to specimens loaded to ultimate at one day. Three different embedment lengths were tested.

1220 . Collins, R., "CONCRETE FROM CRUSHED JURASSIC LIMESTONE," Quarry Management and Products, Vol. 10 No. 3, Mar 1983, pp. 127.

In this paper, 1 5 samples from 11 quarries are compared with a thames Valley flint gravel and a hard carboniferous limestone from the Mendip Hills. Samples were drawn to illustrate the effects of different rock formations, lateral variations in rock formations and different layers within one quarry. Details are given of freeze-thaw tests of concrete durability on a series of different cement contents. Water absorption tests were also carried out and checks were made of mixing abrasion and dust content. Results showed that jurasic limestone is capable of producing acceptable concrete where air entrainment is unnecessary. Conditions of freezing after prolonged saturation are likely to produce surface spalling. The weakest aggregates are incapable of producing high strength concrete, but in most cases strengths are comparable with values obtained for strong aggregates. Excessive amounts of dust can be formed due to the break-up of the coarse aggregate during mixing but this can be remedied before batching. The absorption value of limestone aggregates was not found to be a good measure of concrete durability and low absorption aggregates in plain concrete gave some poor results in its laboratory freeze-thaw tests.

1221. Diederichs, U. and Schneider, U. et al., "FORMATION AND PROPAGATION OF CRACKS AND ACOUSTIC EMISSION," Dev Civ Eng 7, Frac Mech of Concr, 1983, pp. 157-205.

The report summarizes our knowledge on acoustic emission techniques with concrete and concrete members. It gives a survey on origin, propagation,

95

shape and s i z e o f acoustic: e m i s s i o n s i g n a l s . The e x p e r i m e n t a l t e c h n i q u e s i n c l u d i n g d e t e c t i o n and p r o c e s s i n g o f t h e received s i g n a l s are i l l u s t r a t e d as w e l l as t h e e v a l u a t i o n methods. Fu r the rmore t h e com.on u s e o f t h e a c o u s t i c emis s ion t e c h n i q u e i n t e s t i n g materials l i k e metals, glasses, ceramics, p l a s t i c s w i t h r e f e r e n c e t o crack f o r m a t i o n and p r o p a g a t i o n i s ment ioned .

1 2 2 2 . Gannon, C . R. and Wombles, R. H.. e t a l . , "NEW CONCEPTS AND DISCOVERIES RELATED TO THE STRENGTH CHARACTERISTICS OF PLASTICIZED SULFUR, I' ASTM S p e c i a l T e c h n i c a l P u b l i c a t i o n 807, 1983, pp. 84-101.

The o b j e c t i v e o f t h i s s t u d y was t o d e t e r m i n e t h e p h y s i c a l r e a s o n s f o r the h i g h - s t r e n g t h character is t ics o f p las t ic ized s u l f u r c o n c r e t e and t o d e f i n e p r a c t i c a l m a n u f a c t u r i n g t e c h n i q u e s . The r e s u l t s o f t h i s s t u d y reveal some v e r y i n t e r e s t i n g phenomena. The Vroom p r o c e s s o f s u l f u r p l a s t i c i z a t i o n e x h i b i t s a v e r y u n u s u a l d i s p l a y o f o r d e r e d angu:Lar c r y s t a l l i z a t i o n . T h e Bureau o f Mines' p l a s t i c i z e d s u l f u r shows a d i f c e r e n t c r y s t a l l i z a t i o n p a t t e r n c o n s i s t i n g o f bonded spherical b o d i e s . These c r y s t a l l i z a t i o n phenomena i n d i c a t e a l o g i c a l p h y s i c a l e x p l a n a t i o n f o r t h e s u p e r i o r s t r e n g t h characterist ics i n h e r e n t i n p l a s t i c i z e d s u l f u r c o n c r e t e s manufac tured by e n t i r e l y d i f f e r e n t p r o c e s s e s . These new d i s c o v e r i e s are revealed by m i c r o s c o p i c e x a m i n a t i o n s u t i l i z i n g b o t h the stereomicroscope and the scanning electron microscope . These unique m i c r o s c o p i c phenomena o f f e r t o t h e s c i e n t i f i c community a d i f f e r e n t e x p l a n a t i o n as t o why u n u s u a l l y higher s t r e n g t h s are o b t a i n e d i n p l a s t i c i z e d s u l f u r c o n c r e t e s .

1223 . Hague, M. N . and Haber, E. W . , ' "HIGH FLY ASH CONCRETE I N PAVEMENTS," Department o f Ma.in Roads, Royal Military College; New South Wales, 1983, pp. 5.

T h e i n c r e a s e d f o r e c a s t p r o d u c t i o n o f f l y ash, f u t u r e p r e s s u r e s o f r e s o u r c e u t i l i z a t i o n and p r o t e c t i o n o f environment w i l l compel t h e greater u t i l i z a t i o n o f f l y ash. R e c e n t l y , h i g h - f l y ash c o n c r e t e (hfc) has emerged as a mater ia l of c o n s t r u c t i o n i n i t s own r i g h t . I t i s p roposed t h a t s u b s t a n t i a l q u a n t i t i e s o f f l y ash can be u t i l i z e d i n s u b b a s e a n d / o r base o f a pavement s t r u c t u r e as r o l l e d c o n c r e t e o r e c o n o c r e t e . Some p o t e n t i a l a p p l i c a t i o n s o f h fc are reviewed and same r e c e n t a p p l i c a t i o n s o f h fc on t h e l o c a l s c e n e are l i s t e d . A l a b o r a t o r y s t u d y i s described o f h f c mixes u s i n g Alberta f l y a s h ( a i r - e n t r a i n e d and n o n - a i r - e n t r a i n e d ) o f medium t o low

9 6

workability for placement by slip forming and roller compaction, respectively. The concretes were characterized as to their compressive, indirect tension, and flexural strengths, drying shrinkage and freeze-thaw durability. It is confirmed that cohesive non-segregating concrete can be manufactured containing up to 75 percent fly ash in the cementitious fraction. These mixes can be effectively air-entrained which in turn provides adequate freeze- thaw durability. The tensile and compressive strength achieved are adequate for the proposed applications. In particular, the high tensile/compressive strength ratioo is most attractive in pavement applications.

1224. Hofmann, P. and Stoeckl, S., "TESTS ON THE CREEP RECOVERY OF HIGH STRENGTH LIGHTWEIGHT CONCRETE," Deutscher Ausschuss fuer Stahlbeton, 1983, pp. 47.

A report is presented on the creep recovery and the shrinkage of lightweight concrete specimens (aggregates: Liapor, Berwilit, Leca, Reba) . The concrete of the test series S an L was produced in the laboratory, for the other series the concrete was taken from building sites. The creep recovery and shrinkage measurements were performed on both cylinders THETA

1225. Jensen, A. P., "BEAMS AND SHELL IN HIGH-STRENGTH CONCRETE," Nordic Concrete Research, No. 2, Dec 1983, pp. 114-124.

A new type of cement-based materials (DENSIT) with compressive strength 160-200 MPa has been investigated with regard to civil engineering applications. Tests on beams and shells have been carried out in order to evaluate the applicability of known calculation methods on such strong materials, and in order to evaluate the application of steel fibres to increase the ductility of the materials.

1226. Kotsovos, M. D., "EFFECT OF TESTING TECHNIQUES ON THE

Materiaux et Constructions, Materials and Structures, Vo1.16, No.91, Jan-Feb 1983, pp. 3-12.

POST-ULTIMATE BEHAVIOUR OF CONCRETE IN COMPRESSION,"

The paper is concerned with an investigation into the effect of testing techniques on the behavior of plain concrete specimens under increasing uniaxial compressive load. It is found that for load increasing to the maximum level that can be sustained by the

97

specimen, specimen b e h a v i o r i s e s s e n t i a l l y independenz of t e s t i n g t e c h n i q u e effects.

1227. M a l h o t r a , V., "THE USE OF FLY ASH, SILICA FUME, SLAG AND OTHER MINERAL BY-PRODUCTS IN CONCIIETE," 7 t h ERMCO Congress and E x h i b i t i o n , London, May 22-26, 1983, 1983, pp. 12.

I n a n energy-hungry wor ld c o n s i d e r a b l e e f f o r t s are b e i n g made t o f i n d s u b s t i t u t e m a t e r i a l s f o r p a r t i a l r e p l a c e m e n t o f cement i n c o n c r e t e . Some of t h e most p r o m i s i n g s u b s t i t u t e s o r supp lemen ta ry cemen t ing mater ia ls are high- and low-calcium f l y ashes, f e r r o u s - and non- fe r rous s lags and condensed s i l i c a fume. T h i s paper p r e s e n t s a s t a t e - o f - t h e - a r t review on the u s e o f t h e s e m i n e r a l by -p roduc t s i n c o n c r e t e . T h e p h y s i c a l and p o z z o l a n i c p r o p e r t i e s of the supp lemen ta ry cement ing materials are o u t l i n e d and their effect on t h e p r o p e r t i e s o f fresh and ha rdened c o n c r e t e are d i s c u s s e d . P a r t i c u l a r emphas is i s placed on t h e u s e o f condensed s i l i c a :fume, a r e l a t i v e l y new a d d i t i o n t o t he f a m i l y o f supp lemen ta ry cemen t ing materials. The c o n t r i b u t i o n o f s u p e r - p l a s t i c i z e r s i n a c h i e v i n g h i g h - s t r e n g t h c o n c r e t e i n c o r p o r a t i n g f l y ash a n d s i l i c a fume i s ment ioned . R e f e r e n c e i s made t o t h e c u r r e n t l y available s p e c i f i c a t i o n s f o r these materials b o t h i n Nor th America and Europe, and t he i r l i m i t a t i o n s are d i s c u s s e d . T h e a d v a n t a g e s a n d l i m i t a t i o n s i n t he u s e o f supp lemen ta ry cemen t ing materials as separately batched ingredients at a ready-mixed c o n c r e t e p l a n t vers.Is the u s e o f b l e n d e d cements are d i s c u s s e d , and Nor th American t r e n d s i n t h i s f i e l d are ment ioned b r i e f l y . I t i s emphasized t h a t a d d i t i o n a l q u a l i t y c o n t r o l measures a re needed when f l y ash, s l ag and s i l i c a f u m e are i n c o r p o r a t e d i n ready-mixed c o n c r e t e . T h i s i s e s p e c i a l l y s o when c h e m i c a l a d m i x t u r e s are a l s o i n c o r p o r a t e d i n c o n c r e t e made w i t h supplementary cement ing mater ia l s .

1228. Meland, I., "HYDRATION O F BLENDED CEMENTS, Nord ic C o n c r e t e Research, No. 2 , D e c 1983, pp. 183-196.

A s a r e s u l t o f a change from O r d i n a r y P o r t l a n d cement t o b l e n d e d cements , f l y ash - and s l a g cements , i n Norway, i n v e s t i g a t i o n s have been made t o compare these cements w i t h Ord ina ry P o r t l a n d cement . T h i s paper p r e s e n t s r e s u l t s from i n v e s t i g a t i o n s a iming a t d i f f e r e n c e s i n degree o f h y d r a t i o n , r e s i d u a l calciurn- hydrox ide , and water c o n t e n t s o f pastes made from f l y ash cement w i t h - and w i t h o u t a d d i t i o n o f condensed s i l i c a fume compared w i t h O r d i n a r y P o r t l a n d cement .

Possible effects of a plasticising agent in a cement- silica paste is discussed.

1229. Ozyildirim, C., "INTERNALLY SEALED CONCRETE FOR BRIDGE DECK PROTECTION," Final Rpt., Virginia Highway C Transportation Research Council, Jul 1983, 17 pp.

This study investigated the characteristics of internally sealed concrete through tests on specimens fabricated in the laboratory to determine its properties and an installation in a bridge deck to assess the controls needed during construction and its performance over five years, the last four under traffic. Air-entrained samples preapred in the laboratory and obtained from the field during construction provided satisfactory strength and adequate freeze-thaw durability, and prevented or minimized the penetration of chlorides. However, the heat treatment of the deck led to numerous cracks which have facilitated penetration of chlorides to the level of the reinforcing steel and reduced the effectiveness of this protective system.

1230. Peterman, M. and Carrasquillo, R., "PRODUCTION OF HIGH STRENGTH CONCRETE.," Final Research Report, Texas University, Austin Center for Transportation Research Austin Texas, Oct 1983, PP. 306.

The main objective of this research program was to establish criteria for selection of materials and their proportions to achieve uniform, economical, high-quality concrete with a compressive strength between 9000 and 12000 psi at 56 days using 6-in.-dia. x 12-in. cylinders cast in steel molds. In this study, the research approach was to investigate the basic interactions among concrete components in mix proportions which are suitable for producing high strength concrete. Approximately 2500 concrete specimens were made and tested as part of this study. Valuable guidelines were established to be followed by practicing engineers in the development of trial mixes for producing high strength concrete.

1231. Sabnis, G. and Ghorbanpoor, A., "STRUCTURAL PROPERTIES OF SUPERPLASTICIZED CONCRETE," Indian Concrete Journal, Vol. 57 No. 7, Jul 1983, pp. 179-185.

This paper reports the results of a study undertaken on the properties, both short and long- term, of superplasticized concrete. A total of 18 concrete mixes, both with and without superplasticizer

99

w e r e s u b j e c t e d t o slump and f low t a b l e tests, and s h r i n k a g e and creep tes t s . sawn t o s t u d y t h e p o s s i b l e e f f e c t on s e g r e g a t i o n . I t w a s conc luded t h a t t h e u s e of t h e a d m i x t u r e i n c r e a s e s w o r k a b i l i t y and compress ive s t r e n g t h o f c o n c r e t e , w h i l e d r y i n g s h r i n k a g e and creeF s t r a i n v a l u e s w e r e n o t changed. No s i g n i f i c a n t s e g r e g a t i o n o r b l e e d i n g w a s n o t i c e d .

A number o f c y l i n d e r s w e r e

1232. S a i t o , M. and Imai, S., " D I R E C T TENSILE FATIGUE O F CONCRETE BY THE USE OF F R I C T I O N G R I P S , " J o u r n a l o f The American C o n c r e t e I n s t i t u t e , V01.80, NO.!^, Sept -Oct 1983, pp. 431-438.

T e n s i l e f a t i g u e tes ts w e r e ccmducted by p r o v i d i n g t h e necked prismatic specimens with t e n s i l e l o a d s u s i n g t h e f r i c t i o n gr ip . The t e s t r e s u l t s show t h a t p l a i n c o n c r e t e e x h i b i t s no f a t i g u e l i m i t i n t e n s i l e f a t i g u e a t less t h a n 2 m i l l i o n c y c l e s and t h a t t h e f a t i g u e s t r e n g t h f o r 2 m i l l i o n c y c l e s i s 72. 8 p e r c e n t of t h e s t a t i c t e n s i l e s t r e n g t h . T e n s i l e f a t i g u e s t r e n g t h i s c o n s i d e r a b l y h i g h e r t h a n compress ive and f l e x u r a l f a t i g u e s t r e n g t h s obta imed by several worke r s .

1233. S c h n e i d e r , U. and Diederichs, U . , "DETECTION O F CRACKS BY MERCURY PENETRATION MEASUREME:NTS," Dev C i v Eng 7, Fract Mech o f Concr, 1983,

T h e r e p o r t gives a brief i n t r o d u c t i o n t o t h e mercury p e n e t r a t i o n method and i - l l u s t r a t e s t h e e v a l u a t i o n and i n t e r p r e t a t i o n of' t h e o b t a i n e d measurement r e s u l t s w i t h r e spec t . t o crack measurements . T h e mercury p e n e t r a t i o n method c o n c e i v e s t h e t o t a l specimen volume. Fur the rmore one ge ts q u a n t i t a t i v e r e s u l t s on c r a c k wj-dths and c r a c k volumes. Expe r imen ta l r e s u l t s i n d i c a t e t h a t t h e method i s s u i t a b l e f o r g e t t i n g informat - ion a b o u t c r a c k s r e s u l t i n g from i n t e r n a l l y o r e x t e r n a l l y induced stresses namely, s h r i n k a g e , m e c h a n i c a l l y and t h e r m a l l y applied stresses.

1234. Shah, S. and Naaman, A . e t a l . , "EFFECT O F CONFINEMENT ON THE DUCTILITY OF LIGHTWEIGHT CONCRETE," I n t l J of Cement Composi tes & Lightweight C o n c r e t e , V o l . 5, N o . 1, Feb 1983, pp. 15-27.

Tests are r e p o r t e d t o determine the u n i a x i a l compress ive s t r e s s - s t r a i n c u r v e s o f l i gh twe igh t aggregate c o n c r e t e i n c l u d i n g t h e d e s c e n d i n g p o r t i o n o f t h e c u r v e . The effect o f l a t e r a l conf inement and

100

compressive strength on ductility are evaluated. It is shown that an essentially elasto-plastic response for lightweight concrete could be obtained by providing a large amount of confinement. The results are compared with those of normal weight concrete.

1235. Sorensen, E. V., "FREEZING AND THAWING RESISTANCE OF CONDENSED SILICA FUME (MICROSILICA) CONCRETE EXPOSED TO DEICING CHEMICALS," Fly Ash, Silica Fume, Slag & Other Mineral By-products in Concrete, American Concrete Institute SP-79, Vol. 2, 1983, pp.709-718.

action in conjunction with the use of deicing chemicals has become a severe concrete durability problem. The present paper reports results of freezing and thawing experiments performed to evaluate the effect of microsilica (beneficiated condensed silica fume) addition to concrete in that respect. Tests performed using a standard and a modified method show that the drying - rewetting history of the concrete prior to freezing and thawing has a significant influence on conventional concrete, whereas microsilica concrete is relatively unaffected. Air entrainment has a marked beneficial effect on both conventional and microsilica concrete, although microsilica concrete with relatively low cement contents can be manufactured to be frost resistant without air entrainment.

Scaling of concrete due to freezing and thawing

1236. Sullivan, C., "CORROSION INHIBITING ADMIXTURE FOR CONCRETE," Proceedings of 37th Annual Ohio Transportation Engineering Conference, Nov 1983, pp. 18-20.

This paper is a brief discussion of a system designed to inhibit chloride-induced corrosion of reinforcing steel in portland cement concrete. Subjects of interest include: calcium nitrite as a corrosion inhibitor (with FHWA test results), chloride ion intrusion data, the use of high range water reducers to limit chloride intrusion and field application of the inhibitor system. This paper was presented during The Proceedings of the Thirty-Seventh Annual Ohio Transportation Engineering Conference.

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1 2 3 7 . Vos, E . , "INFLUENCE OF LOADING ELATE AND RADIAL PRESSURE ON BOND I N REINFORCED CONCRETE. A NUMERICAL AND EXPERIMENTAL APPROACH, I' U n i v e r s i t y Press, D e l f t , N e t h e r l a n d s , O c t 1983, p p . 235.

One o f t h e fundamenta l p r i n c l p l e s o f t h e compos i t e material r e i n f o r c e d c o n c r e t e i s t h e bond o f t he r e i n f o r c i n g steel t o the c o n c r e t e . I t d e t e r m i n e s t h e c r a c k i n g b e h a v i o u r o f r e i n f o r c e d c o n c r e t e , t he d e f l e c t i o n b e h a v i o u r i n t h e cracked stage, and the anchorage of t h e r e i n f o r c i n g s teel . Much research has been carried o u t on t he bond p r o p e r t i e s , e s p e c i a l l y u n d e r s t a t i c l o a d i n g c o n d i t i o n s . I n regard t o t h e bond b e h a v i o u r unde r impact l o a d i n g c o n d i t i o n s , however, l i t t l e i s known. A t t e r n p t s have been made t o es tab l i sh t h e o r e t i c a l models. S t i l l no model i s available t h a t c a n e x p l a i n quai:-tatively a n d q u a n t i t a t i v e l y by means o f t h e r e l e v a n t bond mechanisms and phenomena the i n f l u e n c e o f t he numerous parameters i n f l u e n c i n g bond. T h i s research c o m p r i s e s a n e x p e r i m e n t a l and a n u m e r i c a l pa r t . The main t o p i c o f the e x p e r i m e n t a l par t w a s t o s t u d y the i n f l u e n c e o f t he l o a d i n g ra te on the bond r e s i s t a n c e of deformed bars, p l a i n bars and p r e s t r e s s i n g s t r a n d s f o r d i f f e r e n t c o n c r e t e compress ive s t r e n g t h s . I n t h e n u m e r i c a l pa r t , a mathematical t o o l w a s deve loped , which made it p o s s i b l e t o s t u d y t h e bond b e h a v i o u r of deformed bars i n a fundamenta l way, i n terms o f o n l y t h e b e h a v i o u r o f t he s u r r o u n d i n g c o n c r e t e and t h e bar geometry . I n c o n c l u s i o n it can be s ta ted t h a t t he deve loped s l i p l a y e r approach , w h i c h has p r o v e d t o be s u c c e s s f u l i n e x p l a i n i n g t h e i n f l u e n c e on bond of c o n c r e t e q u a l i t y , l o a d i n g ra te and e x t e r n a l r a d i a l p r e s s u r e , w i l l be a v a l u a b l e t o o l i n f u t u r e . I t o f f e r s t h e p o s s i b i l i t y o f studyying t h e i n f l u e n c e on bond of deformed bars o f , f o r example, creep, t e m p e r a t u r e o r bar geometry by o n l y chang ing t h e i n p u t parameters o f the material p r o p e r t i e s o r t h e geometry .

1238. Young, J., llSLUMP LOSS AND RETEMPERING O F SUPERPLASTICIZED CONCRETE., F i n a l Repor t , N200, Mar 1983, pp. 23 .

The i n f l u e n c e o f mix d e s i g n and material s e l e c t i o n on t h e slump g a i n and subsequen t l o s s of s u p e r p l a s t i c i z e d c o n c r e t e w a s s t u d i e d . I t w a s d e t e r m i n e d t h a t t h e dose of t he s u p e r p l a s t i c i z e r w a s t he most c r i t i ca l f a c t o r , and the optimum amount depends on t he t y p e o f admix tu re and cement . An o v e r d o s e of admix tu re can lead t o severe s e g r e g a t i o n and b l e e d i n g . S u g g e s t i o n s are q i v e n f o r d e v e l o p i n g s u p e r p l a s t i c i z e d c o n c r e t e s t h a t w i l l m a i n t a i n high

1 0 2

workabilities until the time of placement without undesirable bleeding. Superplasticized concretes can be satisfactorily air entrained. Some adjustments may be needed for loss of air after superplasticizing, but if the final air content is within the usual recommended range then the concrete should be frost resistant.

1239. Zielinski, Z. A. and Spiropoulos, I., "EXPERIMENTAL STUDY ON THE UNIAXIAL AND BIAXIAL FLEXURAL TENSILE STRENGTH OF CONCRETE," Canadian Journal of Civil Engineering, Vol.10, No.1, Mar 1983, pp. 104-115.

The flexural uniaxial and biaxial tensile strength of concrete was studied experimentally on one-way and two-way ribbed slab specimens. The specimens, consisting of a thin slab and deep ribs, constituted part of a waffle-like structure. Uniaxial tension was achieved by supporting the specimens at two points at the ends of one rib, and biaxial tension by supporting the specimens at four points at the ends of two cross ribs. In both support conditions, load was applied in the middle of the slab, thus introducing flexural tension in the ribs and compression in the slab.

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1984

1240. "EFFECT O F AGGREGATES' PHYSICO-MECHANICAL PROPERTIES ON RESISTANCE TO COMPRESSION OF VERY H I G H STRENGTH CONCRETE," B u l l e t i n of t h e I n t e r n a t i o n a l Assoc ia t ion of Engineer ing Geology, No. 30, 1984, pp. 187-191.

The c o n s t r u c t i o n of v e r y h igh c o n c r e t e b u i l d i n g s i n s t e a d o f steel i s now q u i t e common and it r e q u i r e s ve ry h igh s t r e n g t h c o n c r e t e s ( 1 0 0 MPa and o v e r ) . T h i s new f i e l d o f u t i l i z a t i o n of c o n c r e t e r e q u i r e s a deeper e v a l u a t i o n of t he physico-mechanical p r o p e r t i e s of c o n c r e t e . T h e r e p o r t p r e s e n t s an exper imenta l s tudy about t he product ion of 1 0 0 MPa c o n c r e t e s w i t h d i f f e r e n t k inds of aggrega te s q u a r r i e d i n S a i n t Laurent Lowlands i n Quebec (Canada) and i d e n t i f i e d as devonian sedimentary rocks and c r e t a c e o u s basic i n t r u s i v e rocks . I t appears t h a t t h e h i g h e r s t r e n g t h s are o b t a i n e d when aggregates and cement p a s t e have s imi la r mechanical p r o p e r t i e s and i f c o a r s e and f i n e

. aggregates are produced w i t h t h e same t y p e o f rock, p r e f e r a b l y a micro-granular l imestone; there i s no n o t i c e a b l e advantage t o u t i l i z e aggrega te s w i t h a s t r e n g t h much more h ighe r t h a n t h a t one o f t h e cement p a s t e .

1241. "TOWER ROAD BRIDGE," Prestressed Concrete I n s t i t u t e , J o u r n a l o f , V o l . 2 9 No. 2, Feb 1984, pp. 144-147.

H i g h s t r e n g t h c o n c r e t e (9000 p s i ( 6 2 . 1 ma)) provided s t r u c t u r a l advantages, long-term d u r a b i l i t y , and economy f o r t h i s 283-f t (86.3 m) long, p r e c a s t p r e s t r e s s e d c o n c r e t e highway bridge which c r o s s e s t h e Tou t l e R i v e r i n t h e S t a t e of Washington. The s t r u c t u r e i s a pos t - t ens ioned three-span cont inuous girder bridge (see p l a n view and c r o s s - s e c t i o n a l d e t a i l s ) . The i n d i v i d u a l girder s e c t i o n s w e r e c a s t i n l e n g t h s o f 89 f t 6 i n . and 95 f t (27.3 and 29.0 m ) . T h e g i r d e r s e c t i o n s w e r e spliced i n t h e f i e l d , r e s u l t i n g i n f i n i s h e d girder l e n g t h s of 277 f t (84.45 m)

1242. Anon, "STATE-OF-THE-ART REPORT ON HIGH-STRENGTH CONCRETE," J o u r n a l of The American Concrete I n s t i t u t e , V O ~ . 81, No.4, Jul-Aug 1984, pp. 364-411.

C u r r e n t l y a v a i l a b l e informat ion about h igh - s t r eng th c o n c r e t e i s summarized. Topics d i s c u s s e d i n c l u d e s e l e c t i o n o f materials, c o n c r e t e mix p ropor t ion ing , ba t ch ing , mixing, t r a n s p o r t i n g , p l a c i n g , c o n t r o l procedures , c o n c r e t e p r o p e r t i e s , s t r u c t u r a l des ign ,

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economics, and applications. A bibliography is included. Refs.

1243. Arnaouti, C. and Sangakkara, S. R., "CREEP AND SHRINKAGE IN A LIGHTWEIGHT-AGGREGATE CONCRETE," Magazine of Concrete Research, Vol. 36, No. 128, 1984, pp. 165-173.

A model is presented for the determination of the creep and shrinkage of a large reinforced concrete structure from the shrinkage data of a small plain concrete prism. The method is based on the linear relationship between drying creep and concurrent shrinkage and the relationship between drying shrinkage and the exposed area to volume ratio of a concrete specimen. This model was developed to obtain time-dependent properties of concrete slabs for the non-linear finite element analysis of restrained concrete slabs.

1244. Bazant, Z. P. and Chern, J.-C., "RATE-TYPE CONCRETE CREEP LAW WITH REDUCED TIME," Journal of Engineering Mechanics, Vol. 110, No. 3, Mar 1984, pp. 329-340.

For creep analysis of large structural systems, the linear aging integral-type creep law needs to be converted to a rate-type form, which consists of a system of first-order linear differential equations with age-dependent coefficients. The system may be visualized by the Kelvin chain model with age- dependent elastic moduli and viscosities. In the existing formulation, the independent variable is actual time. It is shown that, by using as the independent variable a certain reduced time, which increases 'with time at a gradually declining rate, one reduces the number of differential equations needed to describe creep within the given time range, thereby making numerical structural analysis more efficient. An algorithm for identifying the material parameters from given creep data is also presented.

1245. Bazant, Z. P. and Chern, J.-C., "DOUBLE-POWER LOGARITHMIC LAW FOR CONCRETE CREEP," Cement and Concrete Research, Vol. 14, No. 6, 1984, pp. 793-806.

An improvement of the double-power law for creep at constant temperature and moisture content is proposed. Comparisons with available test data indicate that the final slopes of long-term creep curves, as indicated by the double-power law, are predominantly on the high side. This remedied by introducing a transition to a

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straight line in the logarithmic scale of load duration. The strain at t:he transition as well as the slope of the straight line are *:he same for all ages at loading.

1246. Bazant, Z. P. and Chern, J.-C., "BAYESIAN STATISTICAL PREDICTION OF CONCRETE CREEP AND SHRINKAGE," Journal of The American Concrete Institute, Vol. 81, No. 4, 1984, pp. 319-330.

Inpresent design practice, the statistical approach is used for strength but not fo.r deformations, including creep and shrinkage. :3owever, predicting concrete creep properties from design strength and concrete composition involves a large uncertainty, much larger than that of strength. It is shown that by carrying out some short-time creep measurements, even rather limited ones, the uncertainty can be drastically reduced, and extrapolation of short-time measurements can be made much more reliable. This is accomplished by developing a Bayesian approach to creep prediction. This information is combined, according to Bayes' theorem, with the probability of a given concrete's creep values to yield the posterior probability distribution of the creep values for any load duration and age at loading. Only a linear creep case is considered, and a normal distribution of errors is assumed for the given concrete as well as for the prior information.

1247. Bazant, Z. P. and Panula, L., "PRACTICAL PREDICTION OF CREEP AND SHRINKAGE OF HIGH STRENGTH CONCRETE," Materiaux et Constructions, Materials and Structures, Vo1.17, No.101, Sep-Oct 1984, pp. 375-378.

A model for practical prediction of creep and shrinkage of normal strength concrete, developed previously, is extended to high strength concrete. It is found that only a minor adjustment for the concrete strength effect is needed in the formulas for drying creep. The formulas for basic creep and shrinkage need no adjustment. The prediction model is compared with test data for creep and shrinkage and a satisfactory agreement is demonstrated. The coefficient of variation of the deviations from test data is not larger than that for the normal strength range.

106

1248.

1249.

1250.

Bocca, P., "APPLICATION OF PULL-OUT TEST TO HIGH STRENGTH CONCRETE ESTIMATION," Materiaux et Constructions, Materials and Structures, Vo1.17, N0.99, 1984, pp. 211-216.

The paper compares the results of non-destructive (pull-out, pulse velocity, hardness) tests conducted to determine the compressive strength of concrete specimen with strength from 40 to 80 MPa. The pull-out method is seen to exhibit greater sensitivity and precision in the results. It is particularly efficient for high concrete (60 DIVIDED BY 80 MPa). In this case, it may be convenient to combine the ultrasonic/pull-out methods, or else, the ultrasonic/hardness/pullout methods.

Buenfeld, N. and Newman, J., "THE PERMEABILITY OF CONCRETE IN A MARINE ENVIRONMENT," Magazine of Concrete Research, Vol. 36, No. 127, Jun 1984, pp. 67- 80.

Permeability is a fundamental property governing the durability of concrete in the marine environment and it has only recently been appreciated that some concretes exhibit a very significant reduction in permeability on immersion in sea-water. To investigate this phenomenon further, a resistivity technique has been developed and used to monitor the changes in permeability of five mortars and one concrete on exposure to sea-water. All mixes studied showed a fall in permeability (increase in resistance) on immersion in sea-water. Indeed 25 mm thick specimens of the two most permeable mortars showed a fall equivalent to over 20 mm of additional thickness after only 10 weeks. This increase is due to the formation of an aragonite-brucite layer on the surface of the mortar plus a more widespread progressive constriction of the cement paste pore system. This effect also has a considerable influence upon the absorption capacity of concrete after a period of drying, which is important in the tidal and splash zones.

Buil, M. and Paillere, A. M. et al., "HIGH STRENGTH MORTARS CONTAINING CONDENSED SILICA FUME," Cement and Concrete Research, Vol. 14, No. 5, 1984, pp. 693-704.

A silica fume and a superplasticizer have been added to an ordinary easily flowing mortar composition. The optimal amounts of those constituents have been determined in order to obtain the maximum

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compressive s t r e n g t h f o r a cons tan t w o r k a b i l i t y . The compressive s t r e n g t h s are approximately t w i c e h i g h e r a t 2, 7 and 28 days as compared t o t h e reference mor tar . The d r y i n g shr inkage i s s l i g h t l y i n c r e a s e d and t h e h y d r a t i o n k i n e t i c s are h i g h l y modified.

1251. Cabrera, J. and Wooley, G . e t a l . , "CONFERENCE PROCEEDINGS OF ASHTECH' 84 SECOND INTERNATIONAL CONFERENCE ON ASH TECHNOLOGY A N D MARKETING, BARBICAN CENTRE, LONDON, Conference ProceedingslAshtech ' 84, September 16-21, 1984, pp. 7 4 0 .

t h e S t r e n g t h of Concrete (Cabrera, J G , Wooley, GR, Hopkins,CJ, Lee ,= , Plowman,C and Fox,H) : T i m e - Dependent P r o p e r t i e s of Concrete Containing P u l v e r i s e d Fuel Ash and a S u p e r p l a s t i c i z e r ( C r i p w e l l , J B , Brooks, JJ and Wainwright,PJ) ; Some Aspects o f S t r e n g t h and Related ' i n S i t u ' P r o p e r t i e s o f ' A i r ' Cured and 'Moist ' Cured OPC/PFA Concretes ( E l l i s , C ) ; PFA f o r Concrete: An Engineering Judgment (Dhir , RK Munday, JGL and Hubbard,TH); In f luence of D i f f e r e n t F ly Ashes on t h e P r o p e r t i e s of Aerated Lightweight Concrete ( H u m s , D , H u b e r , H aand Morte1,H); The E f f e c t of Age of Loading on Es t ima t ing Creep of Mass Concrete Conta in ing F l y Ash and Exposed t o High Temperature (Marzouk,H and N a s s e r , K W ) ; F l y Ash U t i l i s a t i o n i n Concrete Cons t ruc t ion (Swamy,FW); The App l i ca t ion of F l y Ash t o High S t r e n g t h Concrete Products (Nagataki ,S and Ohga,H) ; Examination of t h e Use of High P r o p o r t i o n s of High-Lime Content F l y Ash i n Cons t ruc t ion (Day, RL, J o s h i , RC, Langan,BW and Ward,MA). (cont inued on TRRL 396273).

The Relevance of Pu lve r i zed Fuel Ash P r o p e r t i e s on

1252. C a r r a s q u i l l o , R. L. , "CRACKING AND FAILURE MECHANISM OF H I G H STRENGTH CONCRETE SUBJECT BIAXIAL STATE OF STRESS," Proceedings of t h e I n t e r n a t i o n a l Conference on Cement 6 th , Albuquerque, NM, 1 9 8 4 , pp. 344-359 .

This paper discusses t h e observed c r a c k i n g behavior and f a i l u r e mechanism o f h igh s t r e n g t h concrete subjected t o b i a x i a l compression. For t h i s s tudy , bo th model concrete specimens and r ea l concre te specimens c u t from larger beam specimens were tested. Three d i f fe ren t coarse aggrega te s t o g e t h e r w i t h t h r e e d i f f e ren t mortar mixes having c i i f f e r e n t s t r e n g t h and e l a s t i c p r o p e r t i e s were used i n order t o determine t h e effects of materials p r o p e r t i e s on t h e c racking behav io r and f a i l u r e mechanism of h igh - s t r eng th concre te .

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1253. Cedolin, L. and Mulas, M., "BIAXIAL STRESS-STRAIN RELATION FOR CONCRETE," Journal of Engineering Mechanics, Vol. 110, No. 2, Feb 1984, pp. 187-206.

A constitutive law for concrete under monotonic biaxial loading up to peak stress is presented in the form of a total, explicit relation between stresses and strains. Explicitness is achieved by expressing the bulk and shear moduli of elasticity as nonlinear functions of the first two invariants of the strain tensor. The resulting stress-strain relation depends only on three parameters, which characterize the concrete, initial elastic moduli, and compressive strength. Its use is very simple and leads to accurate predictions of the experimental results even close to the peak stress, where inelastic dilatancy occurs.

1254. Christensen, D. W. and Sorenson, E. V. et al., "ROCKBOND: A NEW MICROSILICA CONCRETE BRIDGE DECK OVERLAY MATERIAL," International Bridge Conference, Pittsburgh, PA, 1984, pp. 151-160.

The deterioration of concrete bridge decks due to chloride induced corrosion of reinforcement and scaling due to freeze-thaw cycling is a major problem. This report summarizes test programs on three bridge deck overlay materials: latex-modified concrete, low- slump dense concrete and a new material, ROCKBOND, which is a high-strength microsilica concrete made using EMSAC-B, a microsilica based concrete additive. The results of the tests show that high-strength microsilica concrete develops greater compressive, flexural and bond strengths than the other materials, is much less permeable to chloride ions, and has excellent freeze-thaw resistance.

1255. Coleman, S. and Diamond, S., "STUDIES OF LOW-POROSITY CONCRETES DESIGNED FOR BRIDGE DECK APPLICATIONS: 1 MIX DESIGNS, STRENGTH DEVELOPMENT AND RHEOLOGICAL CHARACTERISTICS," Cement and Concrete Research, Vol. 14, No. 5, Sep 1984, pp. 670-678.

A major problem in recent years has been premature deterioration of concrete bridge decks due to corrosion of reinforcing steel. The research reported here was designed to explore the possibility of eliminating the problem by the use of low porosity concrete. A brief review of low porosity cement systems is provided. Mix design considerations are explored. The results of laboratory trials on rheological and other features of fresh low porosity

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c o n c r e t e s are r epor t ed , and compressive s t r e n g t h d a t a are provided f o r several d i f f e r e n t systems. (TRRL)

1256. Corne l i s sen , H. A. W, "FATIGUE L I F E P R E D I C T I O N O F PLAIN CONCRETE SUBJECTED TO UNIAXIAL T E N S I O N AND TENSION-COMPRESSION," L i f e Assessment of Dynamically Loaded Materials and S t r u c t u r e s , Proceedings o f t h e 5 t h European Conference on F r a c t u r e ; Lisbon, P o r t u g a l , V01.2, Sept 17-21 1984, pp. 729-738.

From constant-ampli tude tests on p l a i n c o n c r e t e s u b j e c t e d t o u n i a x i a l r epea ted t e n s i o n and a l t e r n a t i n g tension-compression, a marked r e l a t i o n was deduced between c y c l i c secondary c r e e p ra te and t i m e t o f a i l u r e . T h i s r e l a t i o n i s a p p l i e d t o improve t h e e s t i m a t i o n o f f a t i g u e l i f e of c c n c r e t e s u b j e c t e d t o program load ing and variable ampli tude load ing . The tests are described and t h e results are p r e s e n t e d and d i scussed .

1257. Corne l i s sen , H. A. W. and Reinha.rdt, H. W . , "UNIAXIAL TENSILE FATIGUE FAILURE O F CONCFETE UNDER CONSTANT- AMPLITUDE AND PROGRAMME LOADING," Magazine o f Concrete Research, Vo1.36, No.129, Dec 1984, pp. 216-226.

Uniax ia l repea ted- tens ion and tension-compression tests on p l a i n c o n c r e t e are described. The r e s u l t s a r e p r e s e n t e d as S-N diagrams and i n the form of a modif ied Goodman diagram. S t r e s s : reversals appeared to reduce l i f e s i g n i f i c a n t l y . By a s t a t i s t i c a l t r e a t m e n t , t h e i n f l u e n c e of scatter i n t h e s t a t i c s t r e n g t h upon the f a t i g u e r e s u l t s w a s ascer ta i .ned . To avo id t h e effect of t h i s scatter, c y c l i c creep r a t e w a s e v a l u a t e d t o predict l i f e more a c c u r a t e l y i n cons t an t - ampli tude tes ts as w e l l as i n program load ing tests.

1258. Corne l i s sen , H . A. W, "FATIGUE FAILURE OF CONCRETE I N T E N S I O N , " Heron, Vo1.29, No.4, 1.984, pp. 68.

Concent r ic t e n s i l e and f l e x u r a l t e n s i l e f a t i g u e tes ts w e r e carried o u t on p l a i n c o n c r e t e specimens. T h e effects o f p u l s a t i n g t e n s i l e l o a d i n g s as w e l l a s o f a l t e r n a t i n g tens i le -compress ive load ings w e r e s t u d i e d . T h e r e s u l t s of the cons tan t -ampl i tude tes ts have been p r e s e n t e d i n S-N diagrams and a Goodman diagram. From t h e s e r e s u l t s it emerged t h a t f a t i g u e l i f e w a s s t r o n g l y reduced by a l t e r n a t i o n o f t h e stress from t e n s i o n t o compression. Furthermore t h e number of c y c l e s t o f a i l u r e f o r w e t specimens w a s lower t h a n f o r d ry ones. I t w a s a l s o found t h a t f o r equa l l o a d s i g n a l s app l i ed , f l e x u r a l tests r e s u l t e d i n longe r

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fatigue lifes than concentric tests, probably because of the possibility of redistribution of stresses. The longitudinal strains of the concentric tests were analyzed. This resulted in a strong relation between strain rate and fatigue life.

1259. Day, R. L. and Cuffaro, P. et al., "EFFECT OF RATE OF DRYING ON THE DRYING CREEP OF HARDENED CEMENT PASTE," Cement and Concrete Research, Vol. 14, No. 3, 1984, pp. 329-338.

Tests were performed on miniature, thin-wall, hardened cement paste specimens; specimens under load were dried at various rates, re-wet and then unloaded. Deformation was monitored throughout. Appropriate control specimens for shrinkage/swelling, basic creep and weight change were also tested. Relationships between moisture loss, shrinkage and wetting creep were obtained. It was found that, like shrinkage, the magnitude of drying creep is independent of rate of drying.

1260. Dhir, R. K. and Yap, A . W. F, "SUPERPLASTICIZED FLOWING CONCRETE: STRENGTH AND DEFORMATION PROPERTIES, " Magazine of Concrete Research, Vol.36, No.129, Dec 1984, pp. 203-215.

This is the final paper from a wide-ranging investigation undertaken into superplasticized high- workability concrete. The properties described are those of strictly flowing concrete in the hardened state and inc1ude:compressive strength, drying shrinkage, thermal expansion, elastic deformation, creep, creep recovery and post-creep-recovery elastic deformation and strength. With regard to the various mix, curing and testing parameters considered, both normal and flowing concretes appear to respond in a similar manner for the properties studied.

1261. Dhir, R. and Yap, A., "SUPERPLASTICIZED FLOWING CONCRETE STRENGTH AND DEFORMATION PROPERTIES," Magazine of Concrete Research, Vol. 36, No. 129, Dec 1984, pp. 203-215.

This paper investigates superplasticized high- workability concrete. The properties described are those of strictly flowing concrete in the hardened state and include: compressive strength, drying shrinkage, thermal expansion, elastic deformation, creep, creep recovery and post-creep- recovery elastic deformation and strength. It is shown that flowing

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c o n c r e t e s made w i t h s u p e r p l a s t i c i z e r s o f c a t e g o r i e s a and b e x h i b i t similar p r o p e r t i e s . I n compar ison w i t h t h e c o r r e s p o n d i n g normal c o n c r e t e , f l o w i n g c o n c r e t e , f o r a g i v e n s t r e n g t h , i s .Likely t o r e q u i r e a s l i g h t l y h i g h e r cement c o n t e n t , it exhibyi ts h i g h e r s h r i n k a g e , s l i g h t l y h i g h e r e l a s t i c modulus and lower creep, w h i l s t i t s creep r e c o v e r y and p o s t - c r e e p - r e c o v e r y e l a s t i c d e f o r m a t i o n and s t r e n g t h p r o p e r t i e s are g e n e r a l l y comparable . With regard t o t h e v a r i o u s mix, c u r i n g and t e s t i n g p a r a m e t e r s c o n s i d e r e d , b o t h normal a n d f l o w i n g c o n c r e t e s a p p e a r t o r e spond i n a s imi l a r manner f o r t h e p r o p e r t i e s s t u d i e d . (Author/TRRL)

1262. D r a n s f i e l d , J. M. , "DEVELOPMENTS I N SUPERPLASTICISERS, 'I Concre t e (London) , V o l . 18 , N o . 1 2 , Dec 1 9 8 4 , pp. 7-11.

I n t e r n a t i o n a l l y , the u s e o f s u p e r p l a s t i c i s e r s has i n c r e a s e d d r a m a t i c a l l y o v e r t h e l a s t t e n y e a r s . T h i s has been b r o u g h t a b o u t by t h e fm:,llowing three f a c t o r s : (1) development of t he performa.nce characterist ics by t h e a d m i x t u r e companies t o over,zome t h e i n h e r e n t d i f f i c u l t i e s which were e x p e r i e n c e d on s i t e w i t h some of t h e f irst g e n e r a t i o n s u p e r p l s s t i c i s e r s , p a r t i c u l a r l y problems w i t h mix 'des ign , bleed, s e g r e g a t i o n and s h o r t working l i f e ; a greater c o n f i d e n c e i n t he i r u s e r e s u l t i n g from i n c r e a s e d t e c h n i c a l data on t he e f fec ts , b o t h s h o r t a n d l o n g t e r m , which these a d m i x t u r e s have on t h e p r o p e r t i e s of t h e c o n c r e t e ; and ( 3 ) a greater awareness o f t h e b e n e f i t s which t h i s c l a s s o f a d m i x t u r e can b r i n g . T h i s a r t i c l e attempts t o summarise t h e l a t e s t t h i n k i n g i n respect o f t h e s e three f a c t o r s .

1263. Eden, N . B. and B a i l e y , J. E . , "MECHANICAL PROPERTIES AND TENSILE FAILURE MECHANISM OF A H I G H STRENGTH POLYMER M O D I F I E D PORTLAND CEMENT," J o u r n a l o f Materials Science, V o l . 19, Aug 1984, pp. 2677-2690.

An i m p o r t a n t parameter f o r t h e material i s the amount o f polymer p r e s e n t , and the p r o p e r t i e s are found t o be dependent upon the degree o f d r y i n g . Al though i n c r e a s i n g polymer c o n t e n t c a u s e s a r e d u c t i o n i n t he i n i t i a l t a n g e n t modulus, it i s shown t h a t r e t a r d a t i o n o f h y d r a t i o n may a c c o u n t f o r t h i s . I n the d r y s ta te , i n c r e a s i n g polymer c o n t e n t leads t o i n c r e a s i n g f l e x u r a l s t r e n g t h , f r a c t u r e t o u g h n e s s and f a i l u r e s t r a i n , b u t l e a v e s i n i t i a l e l a s t i c modulus r e l a t i v e l y unchanged. I t i s conc luded t h a t removal o f p o r e s i s n o t t h e p r i n c i p a l s t r e n g t h e n i n g mechanism s i n c e s t r e n g t h i n c r e a s e s are consequen t upon water removal from the m i c r o s t r u c t u r e i n t he p r e s e n c e o f t h e

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polymer . A f i b r i l l a r p u l l - o u t model i s p roposed t o e x p l a i n t h e obse rved b e h a v i o r o f b o t h ' w e t ' and ' d r y ' material and o r d i n a r y P o r t l a n d cement paste.

1264. Eden, N. B. and B a i l e y , J. E . , "ON THE FACTORS AFFECTING STRENGTH O F PORTLAND CEMENT," J o u r n a l o f Materials S c i e n c e , Vo1.19, No.1, 1984, pp . 150-158.

This paper r e p o r t s mechanica l p r o p e r t y measurements f o r P o r t l a n d Cement paste free from f a b r i c a t i o n a r t i f a c t s (e. g. bubb le - type v o i d s ) , and compares them t o p u b l i s h e d r e s u l t s b o t h f o r normal and new h i g h s t r e n g t h cement . Removal o f large v o i d s by vacuum de- a i r i n g leads t o a n i n c r e a s e o f 15% i n mean f l e x u r a l s t r e n g t h and a small decrease i n f r a c t u r e t o u g h n e s s . T h i s i n c r e a s e i n f l e x u r a l s t r e n g t h i s p r e d i c t a b l e from t h e t i e d - c r a c k model p r e v i o u s l y p roposed t o e x p l a i n t h e n o t c h - s e n s i t i v i t y b e h a v i o r o f ha rdened cement paste. F a c t o r s s u c h as m o i s t u r e c o n t e n t are a t l eas t as i m p o r t a n t as la rge v o i d s i n c o n t r o l l i n g mechan ica l p r o p e r t i e s . T h e much i n c r e a s e d s t r e n g t h o f t h e new po lymer -con ta in ing cements must r e s u l t from improvements t o t h e m i c r o s t r u c t u r e o t h e r t h a n t h e simple e l i m i n a t i o n o f v o i d s .

1265. F u r t a k , K . , "A METHOD FOR DETERMINING CONCRETE STRENGTH UNDER INCREASING L O A D I N G , " Cement and C o n c r e t e Resea rch , Vol . 1 4 , No. 6, Nov 1984, pp. 855- 865.

The p a p e r gives a method t o d e t e r m i n e t he f a t i g u e compress ive s t r e n g t h o f c o n c r e t e a t a g i v e n number o f c y c l i c l o a d s . A parameter d i s i n t r o d u c e d , which t a k e s i n t o accoun t mic roc rack development i n c o n c r e t e , depend ing on t h e c r i t i c a l stresses. The i n f l u e n c e o f t h e l o a d i n g f r equency on t h e f a t i g u e s t r e n g t h i s t a k e n i n t o a c c o u n t .

1266 . Gehr ing , D . , "FLEXIBLE P H O E N I X TURNS CLOCK BACK TO PCCP," Surveyor , V o l . 163, No. 4810, Sep 1984, pp . 1 6 .

The a u t h o r b r i e f l y describes t h e f irst p o r t l a n d cement c o n c r e t e pavement (PCCP) c o n s t r u c t e d i n Phoenix s i n c e 1 9 2 1 o v e r a 1.1 m i l e l e n g t h o f r o a d r e q u i r e d t o s u s t a i n up t o 530 18000-pound vehicle l o a d i n g s p e r day . Ten i n c h e s o f p o r t l a n d cement c o n c r e t e o v e r f o u r i n c h e s of abc, a r i v e r - r u n base mater ia l , would c a r r y t h e l o a d i n g s and would o b v i a t e t h e need f o r l o w e r i n g s h a l l o w u t i l i t i e s . aggregates and f i n e s ca l led f o r i n ASTM 467 d e s i g n e d t o give a f l e x u r a l s t r e n g t h o f 4 5 0 p s i w i t h i n 48 h o u r s

A c o n c r e t e mix d e s i g n u s i n g

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w a s chosen . T e s t c y l i n d e r s and beams were t a k e n . F ie ld q u a l i t y c o n t r o l o f compress ive s t r e n g t h and f l e x u r a l s t r e n g t h w e r e described.. The pavement w a s t r a f f i c k e d o n l y a f e w d a y s a f t e r segments were comple ted . The design e x p e c t e d t o be e q u a l i n c o s t t o a f l e x i b l e pavement o v e r a 20-4C y e a r p e r i o d , t a k i n g i n t o a c c o u n t lower main tenance c o s t s e x p e c t e d .

1267. Haque, M. and Langan, B. e t a l . , " H I G H FLY ASH CONCRETES," J o u r n a l o f American C o n c r e t e I n s t i t u t e , V c l . 81, No. 1, J a n 1984, pp. 54-60.

C o n c r e t e s c o n t a i n i n g f l y ash up t o 7 5 p e r c e n t by weight o f t h e c e m e n t i t i o u s mater ia l 'nave p r o p e r t i e s t h a t make them a t t r ac t ive as a subbase o r base c o u r s e component i n pavement c o n s t r u c t i . o n . T h i s paper describes an e x t e n s i v e l a b o r a t o r y s t u d y o f a i r - e n t r a i n e d high f l y ash c o n c r e t e mixes ( a i r e n t r a i n e d and n o n - a i r e n t r a i n e d ) o f medium t o low w o r k a b i l i t y s u i t a b l e f o r p lacement by s l i p f o r m i n g and r o l l e r compact ion , r e s p e c t i v e l y . The c o n c r e t e s were c h a r a c t e r i z e d as t o t h e i r compress ive , i n d i r e c t t e n s i o n , and f l e x u r a l s t r e n g t h s ; d r y i n g s h r i n k a g e ; and f r e e z e - t h a w d u r a b i l i t y . I t i s conf i rmed t h a t c o h e s i v e n o n s e g r e g a t i n g c o n c r e t e s can be manufac tu red c o n t a i n i n g 4 0 t o 75 p e r c e n t f l y ash i n t h e c e m e n t i t i o u s f r a c t i o n .

1268. Hoff, A. and STATOIL, T. N . e t i l l . , " T E S T I N G O F HIGH STRENGTH LIGHTWEIGHT AGGREGATE CONCRETE ELEMENTS," Nord ic C o n c r e t e Research, No. 3,, 1984, pp . 63-91.

The p r e s e n t p a p e r deals w i t h a n e x p e r i m e n t a l i n v e s t i g a t i o n o f s t r u c t u r a l e l e m e n t s o f high s t r e n g t h l i gh twe igh t aggregate (LWA) - c o n c r e t e exposed t o b e n d i n g and shear and a x i a l compress ion . I n a d d i t i o n , f a t i g u e tes ts o f p l a i n h igh s t r e n g t h LWA-concrete are reported. The tes ts are a p a r t of a t e s t programme w h i c h a i m t o p r o v e t he a p p l i c a b i l i t y o f high s t r e n g t h LWA-concrete ( C > 6 0 ) f o r deep water s t r u c t u r e s . The r e s u l t s are compared w i t h f i n d i n g s i n c o r r e s p o n d i n g i n v e s t i g a t i o n s o f normal d e n s i t y ( N D ) c o n c r e t e o f h igh and modera te s t r e n g t h .

1 2 6 9 . HSU, T . T . C, "FATIGUE AND MICROCRACKING O F CONCRETE," Ma te r i aux e t C o n s t r u c t i o n s , Mater ia l s a n d S t r u c t u r e s , V O l . 17 , N O . 97, 1984, pp. 51-5.4.

The direct and i n d i r e c t methods c f examining m i c r o c r a c k s are reviewed. I t is conc luded t h a t t h e d i s c o n t i n u i t y stress i s a fundainental p r o p e r t y o f

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concrete. It signifies (1) the end of the quasi- elastic behavior of concrete, (2) the long time sustained strength of concrete, ( 3 ) the point at which the Poisson's ratio starts to increase, and (4) the point at which mortar cracks begin to develop extensively. However, a logical and measurable definition of discontinuity stress has not yet been found. This paper suggests a new approach to define discontinuity stress based on fatigue tests. The fatigue interaction surface is derived, which reveals a measurable 'kink'. This 'kink' represents the discontinuity stress. Below this 'kink' in the high cycle region, microcracks are developing as bond cracks in a slow gradual process. Above the 'kink' in the low cycle region, mortar cracks are forming continuous networks.

1270. Kholmyanskii, M. M., "PERFORMANCE OF EARTH MATERIALS AND CONCRETES IN ELEMENTS WITH SOLITARY CRACKS," Soviet Mining Science, Vol. 20, No. 2, 1984, pp. 79- 85.

The author considers the performance of such materials in the case where subcritical crack development generates preconditions for tearing or plastic failure. It is shown that, whereas the strain distribution in the weakened section can be approximated by a rather simple analytical expression, the problem can be solved using a simple statistical model. This is shown for three frequently used test schemes.

1271. Lesage, R. and Acker, P. et al., "HIGH-STRENGTH CONCRETE: AN EXPERIMENTAL PROJECT," Bulletin de Liaison des Lab des Ponts et Chaussees, N131, May 1984, pp. 123-127.

This article deals with the construction of the central part of a reinforced concrete deck comprising 180 cubic meters of concrete. The concrete, batched at 400 kg of APC cement of high-speed and high- performance category (HIPR), was supplied by a ready- mixed concrete production plant. On arrival at the site, after 30 minutes of transport, a dose of plasticizer was systematically added to the concrete. The characteristic compressive strength aimed at (within the meaning of the Instruction of 9th March 1979) was 60 MPa, and a strength of this order was in fact obtained on site. The observations made concerned notably: the organization of the control, which requires more personnel than usual when one specifies a high resistance for the concrete, and the difficulty

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of obtaining a satisfactory distribution of the plasticizer in truck-mounted concrete-mixed load.

1272. Macadam, D. and Smith, K. et al., "EVALUATION OF RAPID-SETTING CONCRETES," Transportation Research Record, N1003, 1984, pp. 19-28.

Rapid-setting materials are becoming widely available. Transportation agencies have a strong need for materials that will set rapidly yet provide a durable repair especially in urban areas. There are eight categories of rapid-setting concretes, and these possess a wide range of characteristics and properties. A survey of state transportation departments indicated that there are several preferred properties and characteristics of rapid-setting materials. A test program was conducted to evaluate test procedures for these materials and to determine the properties of a range of rapid-setting concretes. The results of this test program are summarized in this paper. This paper appeared in Transportation Research Record N1003, International Symposium on Mechanical Properties of Special Concrete.

1273. Mor, A. and Mehta, P., "EFFECT OF SUPERPLASTICIZING ADMIXTURES ON CEMENT HYDRATION, 'I Cement and Concrete Research, Vol. 14, No. 5, Sep 1984, pp. 754-756.

The note gives the results of an investigation i n t o the reasons for higher early concrete strengths being obtained by the use of superplasticizer admixtures as compared with strengths of reference cement pastes without plasticizers. It was shown that the rate of cement hydration increases in the presence of superplasticizers. Higher compressive strengths of superplasticized concrete were directly associated with a lower amount of large capillary pores in the superplasticized cement pastes than in the reference cement pastes.

1274. Nakashima Kiyomi and Yoshida, H., "STUDIES ON COLD WEATHER CONCRETING BY THE USE OF SPECIAL SUPER HIGH EARLY STRENGTH CEMENT," Doboku Gakkai Rombun- Hokokushu/Proceedings of the Japan Society of Civil Engineers, 1984, pp. 95-102.

The aim of this study is first to clarify the strength characteristics of the special super high early strength cement at different temperature, secondly, to clarify what effect freezing exerts on the increase of strength when the concrete is

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s u b j e c t e d t o f r e e z i n g a t t he i n i t i a l p e r i o d o f hardening, and t h i r d l y , t o c l a r i f y the r e s i s t i v i t y when t h e c o n c r e t e a t t he i n i t i a l p e r i o d o f hardening o r a f t e r s u f f i c i e n t l y hardened i s s u b j e c t e d t o t h e repeated rapid f r e e z i n g and thawing. I t w a s found t h a t t h e c o n c r e t e u s i n g s p e c i a l supe r high e a r l y s t r e n g t h cement showed the ve ry high m a n i f e s t a t i o n o f s t r e n g t h even a t low tempera ture and s h o r t age. When the c o n c r e t e w a s s u b j e c t e d t o f r e e z i n g a t t h e i n i t i a l p e r i o d of hardening, t he lowest compressive s t r e n g t h j u s t b e f o r e f r e e z i n g , w i t h which the i n c r e a s e o f s t r e n g t h w a s able t o be expec ted by con t inu ing f r e e z i n g , w a s about 5 0 kg/cm**2 s i m i l a r l y t o o r d i n a r y c o n c r e t e .

1275. Nallathambi, P. and Karihaloo, B. L. e t a l . , "EFFECT OF SPECIMEN AND CRACK SIZES, WATER/CEMENT RATIO AND COARSE AGGREGATE TEXTURE UPON FRACTURE TOUGHNESS OF CONCRETE, Magazine o f Concrete Research, V o l . 36, No.129, Dec 1984, pp. 227-236.

Tests w e r e performed on cement mor ta r and c o n c r e t e beams, i n two stages, w i t h a view t o s tudy ing t h e i n f l u e n c e of several specimen and mix variables on t h e f r a c t u r e behavior of conc re t e . On t h e basis of t h e r e s u l t s from t h e f irst stage o f tests, i n which a s i n g l e water/cement r a t i o and t y p e of c o a r s e aggregate w e r e used, a s imple formula w a s established t o estimate t h e f r a c t u r e toughness o f c o n c r e t e i n terms o f specimen dimensions, maximum aggregate s i z e and no tch depth, t o g e t h e r w i t h t h e mix compressive s t r e n g t h and modulus o f e l a s t i c i t y .

1276 . Ohama, Y . and Muranishi, R. , "RELATION BETWEEN CURING CONDITIONS AND STRENGTH OF SILICA FUME TO CONCRETE," Proceedings of t h e Twenty-seventh Japan Congress on Materials Research; Tokyo, Japan, 1984, pp. 199-202.

I n t h i s paper , h igh s t r e n g t h c o n c r e t e w i t h t h e selected mix p r o p o r t i o n i s prepared u s i n g s i l i c a fume and water-reducing agent , and cured i n water o f v a r i o u s tempera tures and i n au toc lave . The cured c o n c r e t e i s tested f o r compressive and t e n s i l e s t r e n g t h s , and pore s i z e d i s t r i b u t i o n . The i n f l u e n c e s o f c u r i n g c o n d i t i o n s on t h e s t r e n g t h of t h e c o n c r e t e are examined.

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1277. Philleo, R. E., "VERSATILITY AND HIGH STRENGTH IN CONCRETE MATERIALS,11 Concrete International: Design and Construction, Vol. 6, No. 2, Feb 1984, pp. 41-47.

Future developments in concrete and concrete materials will be determined by energy considerations and new requirements such as those surfacing in Arctic offshore construction. In the concrete industry, the waste materials - fly ash, blast furnace slag, silica fume, and organic binders - will play a significant role in future development as will such factors as recycled concrete, synthetic aggregates, lightweight concrete, high-range water reducers, fiber reinforcement, tunnel shotcreting robots, and roller compaction.

1278. Ramakrishnan, V., "SUPERPLASTICIZED FIBER-REINFORCED CONCRETES FOR THE REHABILITATION OF BRIDGES AND PAVEMENTS," South Dakota School of Mines and Technology, 1984, pp. 4-11.

The most critical problem facing the highway industry is the rehabilitation of its distressed structures, particuarly concrete bridge decks and pavements. Various forms of distress have occured in some of the surfaces and different rehabilitation procedures can be very costly. There is a need to determine the most effective and. the most economically advantageous means to rehabilitate the damaged concrete bridge decks and pavements. An investigation sponsored by the U.S. Department of Transportation has been completed at the South Dakcta School of Mines and Tecnology to develop a tough, high-strength, high- density, durable concrete for bridge deck consruction; and a medium-strength, flowing, structural concrete through the use of superplasticizers and steel fibers. The study was conducted in two phases. The first investigated the basic properties of concrete made with superplasticizers through the use of experimental mixtures conforming to the requirements dictated by statistically valid factorial designs, so that analysis of variance can be used. in the evaluation. The second phase extended the findings into an evaluation of superplasticized concrete containing steel fibers. The study has been completed and the significant results are presented in this paper. The addition of the special type of steel fibers (with deformed ends and glued together into bundles with a quick water soluble adhesive) tc superplasticized concrete greatly increased its ductility, toughness, impact resistance, ultimate flexural strength, post- crack load-carrying capacity, and shock resistance.

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The fiber-reinforced superplasicized concrete also had higher freeze-thaw durability and lower permeability. These improvements were achieved without a reduction of workability or the usual balling of steel fibers in the plastic concrete. Therefore, the fiber-reinforced superplasicized concrete is an almost ideal material for the rehabilitation of bridge decks and highway pavments, and for construction of other concrete structures.

1279. Ramey, G. E. and Strickland, A. M., "AN EXPERIMENTAL EVALUATION OF RAPID-SETTING PATCHING MATERIALS USED IN THE REPAIR OF CONCRETE BRIDGES AND PAVEMENTS," Department of Civil Engineering, Auburn University, Auburn, Alabama, Aug 1984, pp. 147.

The major objective of this investigation was to experimentally evaluate the performance of some commonly used rapid-setting concrete pavement and bridge patching materials. The materials were incorporated into a laboratory testing program designed to evaluate the physical properties relevant to patch placement and performance. Specimens were subjected to a series of tests to measure thier strength at early age, after final curing, and after simulated weathering. A mechanical anchorage system was also incorporated into the tesing program to evaluate patch performance that this type system could provide.

1280. Ramey, G. and Parker, F. J. et al., "EVALUATION OF RAPID SETTING MATERIALS AND CONSTRUCTION TECHNIQUES FOR CONCRETE PAVEMENT PATCHES.," Final Report, Alabama State Highway Department Bureau of Materials and Tests, Oct 1984, pp. 80.

Laboratory and field studies were conducted to evaluate several rapid setting PCC pavement patching materials, several bonding agents, several mechanical anchors systems, patch geometry and patch construction techniques. Rapid-setting PCC, Roadpatch and polymer concrete were evaluated. Manufacturer recommended bonding agents were used with the Roadpatch and polymer concrete. Portland cement grouts and epoxy were used with the rapid-setting PCC. Mechanical anchors consisted of nails or reinforcing bars bent into a U shape installed along the bond surface. Rapid setting PCC and Roadpatch provide adequate patch properties with Roadpatch having superior ductility. Type I11 PC grouts and epoxy provide adequate bond, but the rate of strength gain and sensitivity to low temperatures of the epoxy make the PC grouts more

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desirable for general use. Mechanical anchors improve patch strength and ductility. Anchors that provide a cross sectional area of 0.5 sq in. per 100 sq in. of bond area are recommended.

1281. Saito, M., "TENSILE FATIGUE STRENGTH OF LIGHTWEIGHT CONCRETE," International Journal of Cement Composites and Lightweight Concrete, Vo1.6, No.3, Aug 1984, pp. 143-149.

Tensile fatigue tests of lightweight concrete were conducted on necked prismatic specimens using friction grips. The test results showed that lightweight concrete exhibited no fatigue limit in direct tension. The fatigue strength for 2 million cycles was found to be 75. 4% of static tensile strength. The tensile fatigue strength of lightweight concrete was considerably higher than that of concrete made with natural aggregates. The compressive fatigue strengths of lightweight concrete obtained by other researchers were found to be lower than the tensile fatigue strength of lightweight concrete obtained in this study. The test results also indicated that the stress-strain relations under repeated tensile loading were approximately linear and that their slopes did not change with the number of cycles.

1282. Shah, S. P., 'wPREDICTIONS OF CUMULATIVE DAMAGE FOR CONCRETE AND REINFORCED CONCRETE," Materiaux et Constructions, Materials and Structures, Vo1.17, No.97, Jan-Feb 1984, pp. 65-68.

Nonlinear damage evolution equation is suggested to predict fatigue life of plain concrete subjected to sequential, constant amplitude loading. This approach seems to eliminate the nonconservative aspect of the linear damage law (the Miner hypothesis) and is based on the observed shape of the damage growth relationship. For serviceability based design of reinforced concrete structures, a simple nonlinear relationship is developed to relate the increases in deflection and crack width with. the cycle-ratio.

1283. Shiina, K. and Oyabu, T., "INFLUENCE OF MOISTURE CONTENT ON THE COMPRESSIVE STRENGTH AND YOUNG'S MODULUS OF DRYING CONCRETE," Trans of the Jpn Concr Inst, Vo1.6, 1984, pp. 255-262.

This paper covers the compressive strength and Young's modulus of concrete or mortar which was dried in the atmosphere for 52 weeks after 28 days of water

1 2 0

curing. The concrete or mortar specimens were kept outdoors, indoors and in a constant climate room.

1284. Smith, K. G. et al., "LABORATORY AND FIELD EVALUATION

PAVEMENTS, '' Austin Center for Transportation Research, Austin, TX, J u l 1984, pp. 105.

OF RAPID-SETTING MATERIALS USED FOR REPAIR OF CONCRETE

Minimizing lane down-time is of key importance when repairing concrete pavements in high traffic volume areas. As a result, rapid setting repair materials are in great demand. Many such products are available, however, they differ widely in chemical composition, workability, durability, and cost. The following four proprietary rapid setting materials were chosen for laboratory and field evaluation: (1) Duracel (a water-activated blend of portland cement and gypsum); (2) Set-45 (a water-activated magnesia phosphate) ; ( 3 ) Gilco Highway Patch (a water-activated modified portland cement) ; and (4) Neco-Crete (a magnesia powder which is activated by an ammonium phosphate solution). The repair mixes contained both fine and coarse aggregate. Techniques used to place and finish the repairs were similar to those used with conventional portland cement concrete. Laboratory results include the following: (1) compressive strengths, flexural strengths and Gilmore Needle set times of materials mixed and air-cured at 40, 72, and 110 degrees F (4, 22, and 43 degrees C); (2) change in length of air-cured specimens; and (3) resistance of specimens to freeze-thaw cycles. Field repairs were made in the Waco, Amarillo, Dallas, and Houston districts. Several small full-depth punchouts were repaired in each of these districts using the rapid setting materials.

1285. Smith, K. and Fowler, D. et al., "LABORATORY AND FIELD EVALUATION OF RAPID SETTING MATERIALS USED FOR REPAIR OF CONCRETE PAVEMENTS," Texas University, Austin Center for Transportation Research, Intrm Rpt., Jul 1984, pp. 105.

Minimizing lane down-time is of key importance when repairing concrete pavements in high traffic volume areas. As a result, rapid setting repair materials arre in great demand. Many such products are available, however, they differ widely in chemical composition, workability, durability, and cost. The following four proprietary rapid setting materials were chosen for laboratory and field evaluation: (1) Duracal (a water-activated blend of portland cement and gypsum); (2) Set-45 (a water-activated magnesia

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phosphate) ; ( 3 ) Gilco High.way Patch (a water-activated modified portland cement) ; and (4) Neco-Crete (a magnesia powder which is activated by an ammonium phosphate solution). The repair mixes contained both fine and coarse aggregate. Techniques used to place and finish the repairs were similar to those used with conventional portland cement concrete. Laboratory results include thee follcwing: (1) compressive strengths, flexural strengths and Gilmore Needle set times of materials mixed and air-cured at 4G, 72, and 110 degree F (4, 22, and 43 degree C); (2) change in length of air-cured specirt?ens; and ( 3 ) resistance of specimens to freeze-thaw cycles. Field repairs were made in the Waco, Amarillc, Dallas, and Houston districts. Several small full-depth punchouts were repaired in each of these districts using the rapid setting materials.

1286. Tazawa, Y. and Nobuta, Y. et al., "PHYSICAL PROPERTIES AND DURABILITY OF HIGH-STRENGTH LIGHTWEIGHT CONCRETE INCORPORATING SILICA FUME," Trans of the Jpn Concr Inst, Vo1.6, 1984, pp. 55-62.

The purpose of this study is to evaluate the physical properties and durability of high-strength lightweight concrete incorporating silica fume which is considered to have a good performance as a new concrete material. Based on the experimental design using the orthogonal array table, a series of twenty- seven concrete mixes with s i x f a c t o r s such as t y p e and silica fume content, water to cement plus silica fume ratio, etc. , was used in the test.

1287. Tepfers, R. and Hedberg, E. et al., "ABSORPTION OF ENERGY IN FATIGUE LOADING OF PLAIN CONCRETE," Materiaux et Constructions, Materials and Structures, Vo1.17, No.97, Jan-Feb 1984, pp. 59-64.

Existing partial damage hypothesis gives unsatisfactory results in estimating the fatigue of plain concrete. Volumetric, ultrasonic, and acoustic emission measurements have not been able to fully interpret the deterioration of concrete. Another parameter in this respect might be the absorbed energy by the loaded concrete. In this investigation a measuring system for registration of the absorbed energy is presented. The results achieved are affected by difficulties at the development of the measuring system. However, it seems as if the absorbed energy at failure of concrete was the same for static load and for fatigue load with different intensities.

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1288. Vir t anen , J., "MINERAL BY-PRODUCTS AND FREEZE-THAW RESISTANCE OF CONCRETE, Nordic Concrete Research, No. 3, D e c 1984, pp. 191-208.

T h e u s e of minera l by-products i n c o n c r e t e has i n c r e a s e d cons ide rab ly du r ing the l a s t f e w years. I n the Nordic c o u n t r i e s t h e y a r e used b o t h by t he cement manufac turers and b y conc re t e p l a n t s . The u s e r s are fami l ia r w i t h t h e effects of these p roduc t s on the 28- day s t r e n g t h of conc re t e , b u t l a c k of knowledge does s t i l l e x i s t of the effects on t h e d u r a b i l i t y of c o n c r e t e s . T h i s a r t i c l e is aimed a t g i v i n g in fo rma t ion on t h e effects of ground g r a n u l a t e d b l a s t - fu rnace slag, p u l v e r i z e d c o a l f l y ash, and condensed s i l i c a fume on the freeze- thaw r e s i s t a n c e of c o n c r e t e . T h i s a r t i c l e i s most ly based on two s t u d i e s made a t Oy P a r t e k Ab's Development Centre i n Pargas, F in l and .

1289. Wols iefer , J., "ULTRA HIGH-STRENGTH FIELD PLACEABLE CONCRETE WITH S I L I C A FUME ADMIXTURE," Concrete I n t e r n a t i o n a l : Design and Cons t ruc t ion , Vo1.6, No.4, A p r 1984, pp. 25-31.

U l t r a h igh - s t r eng th conc re t e is now a v a i l a b l e t o the commercial c o n s t r u c t i o n market a t f i e l d p l a c e a b l e slumps, i n t h e compression range of 1 0 , 0 0 0 t o 1 8 , 0 0 0 p s i (69 t o 124 MPa). Laboratory s t u d i e s and f i e l d t e s t programs have been conducted t o e v a l u a t e a new s i l i c a fume t y p e admixture ' s c a p a b i l i t y t o produce s t a t e - o f - the-ar t h igh -qya l i ty conc re t e , over a range of a p p l i c a t i o n s .

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1290. "PLAIN AND REINFORCED CONCRETE UNDER CYCLIC LOADING, Betonwerk und Fertigteil-,Technik, Vol. 51, No. 11, 1985, pp. 705-713.

The results of the single-stage tests with axial (central) pulsating compressive loading and alternating compressive-tensile loading which were performed on normalweight concrete specimens with a 28-day cube strength of about 35 N/mm**2 can be summarized as follows: Under alternating load cycles there is found to be a significant effect of the tensile loading on the fatigue strength and the type of failure. The S/N diagrams display a distinct change in direction at N//b APPROX EQUALS 10**5.

1291. Aarsleff, L. and Bredal-Jorgensen, J. et al., "VERY HIGH STRENGTH CEMENT-BASED MATER1ALS;ON THE PROPERTIES OF ULTRA HIGH STRENGTH CONCRETE WITH PARTICULAR REFERENCE TO HEAT OF HYDRATIONXA," Materials Research Society Symposia Proceedings, Vol.42, 1985, pp. 19-29.

It has been observed that the heat of hydration for concrete under practical conditions not only depends on the type of cement and the content of cement and silica fume in the concrete but also depends on the w/c-ratio of the concrete. On m.icroscopic examination of concrete having low w/c-ratio it has been observed that the cement compounds are left partly unhydrated. However, the unhydrated cement compounds exist for a l l values of the w/c-ratio. This fact will influence the present way of estimating the heat of hydration when a thermal stress analysis is to be carried out for an ultra high strength concrete in order to prevent the concrete from crackling due to temperature differences across a massive cross-section. The tests are carried out with concrete having a compression strength greater than 100 MPa (approx. 14,000 psi). In order to obtain samples drilled from the same casting for compression tests, microscopic investigation, penetration tests and freezing/thawing-investigation rather large specimens are used.

1292. Aavik, J. and Kutti, T. et al., "FLOWING CONCRETE WITH SILICA. CAPILLARY SUCTION AND FROST RESISTANCE," Statens Raad Foer Byggnadsforskning, 1985, pp. 24.

Several investigations have reported that the frost resistance of flowing concrete is low. The improvements that can be achieved by air entraining

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admixtures and an elevated cement content (reduced water/cement ratio) are stated to be considerably lower than in the case of concrete of stiffer consistency. This investigation has studied the capillary suction and frost resistance of flowing concrete in which 10% by weight of the cement has been replaced by silica. Frost resistance was studied for two different degrees of water absorption and by two methods. The concrete was compared with silica concrete of stiff consistency and with concrete without silica. The investigation was carried out in the laboratory under controlled curing conditions. The results showed that admixture of silica refines the capillary structure and improves the frost resistance of both flowing concrete and concrete of stiffer consistency. The frost resistance is satisfactory even at low air contents and high degrees of pore saturation. Admixture of silica into flowing concrete may be an alternative to entrainment of air to provide protection against frost and de-icing salts. This method is less sensitive to segregation and degradation of the protective system in connection with mixing and handling.

1293. Ahmad, S. H. and Shah, S. P., "PROPERTIES OF HIGH STRENGTH CONCRETE FOR STRUCTURAL DESIGN," Materials Research Society Symposia Proceedings, Vol. 42, 1985, pp. 169-181.

The current ultimate strength design practice is based on experimental information obtained from concretes of compressive strengths in the range of 21 to 42 Mpa. For developing a satisfactory procedure for design of structures using higher strength concretes, additional considerations, and validation or modification of existing strength design methods may be necessary. In this paper, experimental data on high strength concrete obtained by the authors are reported. In this paper, the emphasis is on the results, comparison with normal strength concrete, development of the empirical formulae and some discussion on the implication for structural design.

1294. Ahmad, S. H. and Shah, S. P., "STRUCTURAL PROPERTIES OF HIGH STRENGTH CONCRETE AND ITS IMPLICATIONS FOR PRECAST PRESTRESSED CONCRETE, I' Journal of the Prestressed Concrete Institute, Vo1.30, No. 6, 1985, pp. 92-119.

Experimental data on the structural properties of high strength concrete [ f'c greater than 6000 psi (42 MPa) 3 are reported. Based on these findings, as well

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as data on normal s t r e n g t h c o n c r e t e , empirical e x p r e s s i o n s are p roposed . The i m p l i c a t i o n s o f s u c h parameters as compress ive s t r e n g t h , compress ive s t r e s s - s t r a i n c u r v e , modulus o f e l a s t i c i t y , t e n s i l e s t r e n g t h , shear s t r e n g t h , P o i s s o n ' s r a t i o , d u c t i l i t y , l a t e r a l r e i n f o r c e m e n t , as w e l l a s economic c o n s i d e r a t i o n s f o r t h e s t r u c t u r a l d e s i g n o f prestressed c o n c r e t e are s t u d i e d and d e s i g n recommendations are made.

1295. Bache, H. H . , "DURABILITY OF CONCRETE FRACTURE MECHANICAL ASPECTS," Nord ic C o n c r e t e Research, 1985, pp. 7-25.

C o n c r e t e d u r a b i l i t y i s viewed i n t h e l i g h t of f r a c t u r e mechanics . P r i n c i p l e s are p r e s e n t e d a n d applied t o problems r e l a t i n g t o c o n c r e t e d u r a b i l i t y f o r the p u r p o s e o f i n t r o d u c i n g f r a c t u r e mechanics i n d u r a b i l i t y research. T h e b e h a v i o r o f c o n c r e t e materials unde r effects t h a t seek t o d e s t r o y t h e materials - a l k a l i - s i l i c a r e a c t i o n s , f r o s t at tack, e tc . - are mechan ica l phenomena t h a t s h o u l d be c o n s i d e r e d i n t he l i g h t o f f r a c t u r e mechanics .

1296 . Ba rna rd , D . and I r w i n , R. e t a l . , "NZCS (NEW ZEALAND CONCRETE SOCIETY) CONFERENCE," New Zea land C o n c r e t e C o n s t r u c t i o n , V o l . 29, Dec 1985, pp. 3-8.

Among the papers p r e s e n t e d a t t h e c o n f e r e n c e w e r e t h e f o l l o w i n g : P e r m e a b i l i t y - A D u r a b i l i t y F a c t o r (Barna rd , DP); Ca rbona t ion o f C c n c r e t e - A N e w Technique t o I n t e r p r e t C o n d i t i o n s and S e l e c t R e m e d i a l Work ( I r w i n , RW) ; Cement Grout Techniques f o r t h e Repair o f Cracks i n Concre t e S t r u c t u r e s (Smith, L ) ; S e i s m i c R e t r o f i t t i n g o f S t a t e Highway Bridges i n N e w Zea land ( S t u a r t , C R ) ; C u r r e n t Bridge Design and C o n s t r u c t i o n Practice i n Westerr. USA ( B i l l i n g s , I ) ; T h e Response o f R e i n f o r c e d C o n c r e t e S l a b s t o C o n c e n t r a t e d Loads (Dickson, A a d Fenwick, R) ; Anchorage of T r a n s v e r s e Re1nforc:ement i n R e c t a n g u l a r R e i n f o r c e d C o n c r e t e Columns (Tancka, H, P a r k , R and McNamoe, B ) ; S i l i c a Fume C0ncret.e (Gae r ty , L) .

1297. Bazant , Z . P . and Chern, J . - C . , "LOG DOUBLE POWER LAW FOR CONCRETE CREEP," J o u r n a l o f The American C o n c r e t e I n s t i t u t e , V o l . 82, No. 5 , 1985, pp. 665-675.

An improved l a w o f c r e e p o f c o n c r e t e a t c o n s t a n t humid i ty and temperAp 0 5SJs p fo rmula which e x h i b i t s a c o n t i n u o u s t r a n s i t i o n from a poorer c u r v e t o a s t r a i g h t l i n e i n t h e l o g a r i t h m o f creep d u r a t i o n . The s t r a i g h t

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line has the same slope for all ages at loading, and the higher the age at loading, the longer is the duration at which the transition occurs. The exponent of the initial power curve is higher than that used in the double power law and is much too high in comparison with the existing test results for very short load durations in the dynamic range.

1298. Beaudoin, J. J. and Feldman, R. F., "HIGH-STRENGTH CEMENT PASTES - A CRITICAL APPRAISAL," Cement and Concrete Research, Vo1.15, No.1, 1985, pp. 105-116.

The mechanisms responsible for high strength in cement paste systems are assessed in an attempt to define features common to selected new technologies, e. g. , hot-pressed, impregnated, and macrodefect-free pastes. Important factors influencing strength of porous systems include porosity, pore geometry, C-S-H composition, composite behavior, and fracture criteria. The effects of low water-cement ratio, dense inclusions, stress modification in critical areas, and their role in optimizing and controlling production of high-strength cement paste are discussed.

1299. Berner, D. and Gerwick, B. C. Jr. et al., "STATIC AND CYCLIC BEHAVIOR OF STRUCTURAL LIGHTWEIGHT CONCRETE AT CRYOGENIC TEMPERATURES, 'I Conference on Temperature Effects on Concrete, Kansas City, MO;, 1985, pp. 21- 3 7 .

The mechanical behavior of a high-strength, lightweight concrete made with expanded-shale aggregate was determined in the temperature range from 23 DEGREE C (73 DEGREE F) to MINUS 196 DEGREE C (MINUS 320 DEGREE F). High-strength, lightweight concrete i s of particular interest for use in offshore cryogenic containment structures in which the concrete may be subjected to low temperatures and high-intensity cyclic loading simulating 20-year stormwave action. Values of compressive strength, tensile strength, and elastic modulus were determined, with moisture content and cyclic loading serving as key parameters. An evaluation was also made of the behavior of embedded strain gages at cryogenic temperatures. The results indicate that the lightweight concrete performed favorably under the test conditions, with the mechanical properties generally increasing at low temperatures with greater gains for higher moisture contents.

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1300. Biswas, M. and Ghattas, 0. N. et al., "FATIGUE AND FREEZE-THAW RESISTANCE OF EPOXY MORTAR," Transp Res Rec 1041, 1985, pp. 33-37.

Results of tests to investigate resistance of epoxy mortar to fatigue and freeze-thaw exposure are reported. Fatigue resistance is evaluated by number of load reversals sustained against a repeated impactive loading at different temperature levels within the range of 0 to 150 DEGREE F. The results indicate that fatigue resistance decays exponentially with increasing temperature. Freeze-thaw resistance is evaluated as it is affected by the presence of moisture in fine aggregates. The results indicate that basic material strength and stiffness as well as freeze-thaw resistance of epoxy mortar diminish markedly because of the presence of even a small amount of moisture.

1301. Buil, M. and Acker, P., "CREEP OF A SILICA FUME CONCRETE, l1 Cement and Concrete Research, Vol. 15, No. 3, May 1985, pp. 463-466.

Creep tests have been performed on a concrete composition where part of the c:ement was replaced by a silica fume. The results show t.hat the total deformation is decreased in drying condition, without any significant reduction of the basic creep.

1302. Carreira, D. J. and Chu, K.-H., "STRESS-STRAIN RELATIONSHIP FOR PLAIN CONCRETE: IN COMPRESSION, Journal of The American Concrete Institute, Vo1.82, No.6, Nov-Dec 1985, pp. 797-804.

A general form of the serpentine curve is proposed to represent the complete stress-strain relationship of plain concrete in compression. The parameters that define the relationship are physically significant and can be estimated from empirical. relationships or determined experimentally. Proposed equations fit a wide range of testing conditions and concretes for both the ascending and descendhg branches of the stress-strain diagram in compression. The conditions that should meet with an equation representing the stress-strain relationship and the effects of the testing conditions on the relationship are also discussed.

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1303. Cervenka, V., "CONSTITUTIVE MODEL FOR CRACKED REINFORCED CONCRETE," Journal of The American Concrete Institute, Vol. 82, No. 6, 1985, pp. 877-882.

The constitutive model used to calculate the winning solution that was submitted to the international competition to predict the behavior of four reinforced concrete panels tested at the University of Toronto is based on a smeared representation of cracking and reinforcement in plane stress state. The refined action of cracked concrete includes compressive resistance of concrete parallel to cracks, tension stiffening, and shear resistance of concrete on the crack face. A new basic assumption is that compressive strength and other material properties are reduced due to damage done to the concrete by cracking. The model is formulated so that the material stiffness matrix is directly applicable to nonlinear finite element analysis. The material functions are optimized with respect to the experimental data. The parameter study shows the sensitivity of the resulting stress-strain relationship to the separate material parameters.

1304. Cornelissen, H. A. W. and Siemes, A. J. M, "PLAIN CONCRETE UNDER SUSTAINED TENSILE OR TENSILE AND COMPRESSIVE FATIGUE LOADINGS," Behaviour of Offshore Structures, Proceedings of the 4th International Conference; Delft, Netherlands, July 1-5 1985, pp. 487-498.

An overview is presented of three investigations regarding the endurance of plain concrete. The first two concern a test program from Delft University on the behaviour of concrete under sustained and cyclic tensile loadings. The third is an investigation from TNO-IBBC on the behaviour of concrete under random compressive loadings. In all the investigations the loadings were uniaxial. Based on tensile creep tests, relations between the relative stress and time to failure are presented. No significant influence of concrete composition and temperature was found. Results of cyclic tensile tests with stress reversals into the compression zone are given and a complete modified Goodman diagram for dry concrete is proposed. For fatigue life prediction under complex loadings, Miner's rule as well as a method based on strain rate is discussed. The test results are evaluated with Miner' s rule.

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1305. Dewar, V., "TESTING CONCRElTE FOR. DURABILITY. PART 2, 'I Concrete (London), Vol. 19, No. 7, Jul 1985, pp. 19- 21.

The first priority is to establish the purpose of the test, the parameter to be measured and the place of testing. Acceptable tests and. serviceability criteria can be selected which can then be used in establishing compliance criteria. Acceptable overall precision of test results is essential. Confirmation of precision may entail performance tests using special specimens or samples carefully prepared for use by all laboratories. Inspection and accreditation of testing by organisations such. as the UK national testing laboratory accreditation. scheme (natlas) may in the future be applied to samples and to site testing as well as to laboratory testing. The author also refers to the difficulties of simulating conditions using small scale specimens in the laboratory, service life prediction and accelerated testing.

1306. Dewar, V., "TESTING CONCRETE F O R DURABILITY. PART 1," Concrete (London), Vol. 19, No. 6, Jun 1985, pp. 40- 41.

Lack of care in any of the st.ages in the construction of concrete, including specification, production of raw materials, mix formulation, mixing, transporting, placing, compaction around reinforcement, maturing and functioning under action of the working load can lead to faults. The author describes the movement of air arid water within freshly laid concrete as it hardens. In the hardened state, movement continues. Air, moisture vapour, and fluids may enter and move around concrete, evaporating water and depositing or dissolving chemicals o r diluting solutions and moving chemicals around. In reinforced concrete, concrete variations, moisture variations, chemical migration and carbonation will change the electropotential distribution which in turn may encourage electrochemical reactivity ideal for corrosion. Loading, wind levels, daily and annual temperature changes, humidity changes, ground movements and water levels will change the stress and strain concentrations. The outer 25 mm may be considerably more permeable than the inner portion associated with poor protection and lack of curing. The upper 20 per cent of the height may have a substantially greater permeability due to water gain. Concrete can have a different permeability horizontally compared with vertically because of the effects of sedimentation and mic:roscopic cracking.

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Compaction may be variable due to difficulty of compacting concrete well at edges and corners and near boxed out areas, and between reinforcement and the surface. Concrete can have cracks in the heart which are invisible at the surface. Cracks at the surface may not progress far into the concrete or they may go right through. Testing based on conventional standard tests may give misleading results. Testing should be carried out on specimens taken directly from the structure.

1307. Diamond, S., "VERY HIGH STRENGTH CEMENT-BASED MATERIALS - A PROSPECTIVE, Materials Research Society Symposia, Vol. 42, 1985, pp. 233-243.

The present paper represents the author's attempt to provide a framework for organizing the concepts and relationships behind the recent commercial development and production of very high strength cementitious materials. Their production and properties are discussed after consideration of the fundamental behavior and limitations of conventional concrete and cement pastes. A brief comparison of the mechanical characteristics of these ultra high strength materials with other materials will be attempted, and certain relationships between them and the developing 'high tech ceramic' materials briefly explored.

1308. Dingsoyr, E. and Mosberg, T. et al., "INFLUENCE OF AGGREGATES ON THE STRENGTH AND ELASTIC MODULUS OF HIGH STRENGTH MORTARS CONTAINING MICROSILICA," Very High Strength Cement-Based Materials: Materials Research Society Symposia Proceedings, Vo1.42, 1985, pp. 211- 218.

The strength development of mortars made w i t h a high strength paste containing microsilica was investigated as a function of aggregate type and content. Strength could be modelled using composite theory; the predicted strengths of the paste and aggregate component reflected the influence of the cement-aggregate bond. Scanning electron microscopic examinations gave a qualitative idea of the extent of bond failure, which correlated satisfactorily with the predicted behavior. The modulus of elasticity for Sic mortars could be predicted well by Hirsch's model or the aggregate model.

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1309. Eden, N. B. and Bailey, J. E., "FLEXURAL STRENGTH AND FRACTURE TOUGHNESS OF A NORMAL AND A HIGH STRENGTH POLYMER MODIFIED PORTLAND CEMENT, 'I Materials Research Society Symposia Proceedings, V o 1 . 42, 1985, pp. 79- 87.

A model has been developed for the flexural strength of Portland cement pastes, based upon observed fracture behaviour of both normal and high strength pastes. Fibrillar or foil-like elements pull apart at a yield stress which is characteristic of the number of elements and interfacial shear strength. The former can be maximised by usin13 a low water/cement ratio and the latter by inclusim of water-soluble polymer, followed by suitable drying. It is proposed that this is the mechanism by w:hich high strength may be attained in Portland cement.

1310. Ehm, C. and Schneider, U., "HIGH TEMPERATURE BEHAVIOUR OF CONCRETE UNDER BIAXIAL CONDITIONS,1f Cement and Concrete Research, Vol. 15, No. 1, Jan 1985, pp. 27- 34.

Experimental investigations at temperatures up to 600 DEGREE C were made with a n,ew concrete test equipment which allows the determination of strengths and deformations of concrete su:bjected to biaxial compressive stresses at high temperatures. The equipment is described and test results are reported. The test results show that the :biaxial high temperature strength is greater than the uniaxial strength. An increase of the biaxial strength was observed at comparatively high temperatures.

1311. Feldman, R. and Huang, C.-Y., "RESISTANCE OF MORTARS CONTAINING SILICA FUME TO ATTACK BY A SOLUTION CONTAINING CHLORIDES," Cement and Concrete Research, Vol. 15, No. 3, May 1985, pp. 411-420.

Mortars prepared at water/cement + silica fume ratios, w/(c+sf), of 0.45 and 0.60 were exposed to a solution containing a mixture of magnesium, calcium and sodium chlorides to investigate their resistance to attack. Mixes contained 0, 10 and 30 per cent silica fume, and sand-binder ratio was 2.25. Stiffness, pore-size distribution, calcium hydroxide content and non-evaporable water were measured before and after exposure to salt solution. Inclusion of silica fume resulted in increased durability of mortar, especially in specimens prepared at w/(ctsf) of 0.45 and cured for 28 days. Specimens prepared at

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the same w/(c+sf) with 30 per cent silica fume were also durable even after seven days of curing. Calcium hydroxide in mortars was reduced to zero by exposure to the salt solution.

1312. Foure, B., "EXPERIMENTAL STUDY OF CONCRETE STRENGTH UNDER SUSTAINED STRESS, Annales de 1' Institut Technique du Batiment et des Travaux Publics, Vo1.38, No.435, 1985, pp. 1-23.

The results of several test series on concrete specimens subjected to constant loading-till failure are presented. The study deals with normal-weight concrete (with normal strength lower than 50 MPa, and some results for high strength over 70 MPa) and lightweight concrete, under compressive as well as tensile stresses. After a synthesis with other published results, empirical relations are proposed for failure under sustained loading. They express the ratio of sustained failure stress to instantaneous strength at the age of failure, as a function of the duration of loading till failure. These relations are independent of age at loading, concrete strength, type of stress (compression or tension). They depend on the type of concrete, normal- or lightweight.

1313. Frolova, L. S. and Primachenko, V. V. et al., "EFFECT OF COMPLEX MINERAL ADDITIONS ON THE HYDRATION OF ALUMINA CEMENT AND ON THE STRENGTH OF THE CONCRETE BASED ON IT," Refractories (English translation of Ogneupory), Vol. 26, No. 9-10, 1985, pp. 517-528.

cement with plasticizer and mineral additions was conducted. Sodium polyphosphate and calcium chromelingnosulfonate act as plasticizers facilitating reduction of mixed water up to 15-20%. The additions increase the strength. Based on thermographic, x-ray, petrographic, and electron microscopic studies, the products of hydration and their relationship with strengthening were established. The cement containing calcium chromelignosulfonate preserves the high strength of the aluminosilicate refractory concrete during heating up to 1000 DEGREE C.

A study of strength characteristics of an alumina

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1314. Gaynor, R. D. and Meininger, R. C. et al., "EFFECT OF TEMPERATURE AND DELIVERY TIME ON CONCRETE PROPORTIONS," National Ready Mixed Concrete Assocation Publication, No. 171, 1985,

The literature demonstrates that concrete produced at high temperatures [ 35 versus 18 DEGREE C (95 versus 65 DEGREE F) ] or mixed and agitated for 90 versus 20 min, tends to have increased mixing water requirements and reduced strength. The research reported here demonstrates that the additional cement required to compensate for this strength loss can be very modest. Concrete was mixed at temperatures of 18 and 35 DEGREE C (65 and 95 DEGREE F). An increase in the concrete mixing temperature from 18 to 35 DEGREE C (65 to 95 DEGREE F) required an average increase of 4. 7 kg/m**3 ( 8 lb/yd**3) of cement to maintain the strength level.

1315. Gran, J. K. and Seaman, L. et al., "APPLICATION OF A NEW TECHNIQUE TO STUDY THE DYNAMIC TENSILE FAILURE OF CONCRETE," International Conference on Mechanical and Physical Behaviour of Materials under Dynamic Loading, Paris, France, Vol. 46, No. 8, 1985, pp. 617-622.

A new technique to test concrete in dynamic tension is described. The results of an experiment are interpreted using numerical simulations.

1316. Gruebl, P., "FRACTURE BEHAVIOR OF LIGHTWEIGHT AGGREGATE CONCRETE UNDER MULTIAXIAL COMPRESSIVE ' STRESS," Materials Research Society Symposia Proceedings, Vol. 42, 1985, pp. 183-191.

The dimensioning of concrete structures is based usually on the uniaxial strength. This characteristic value is embodied in the regulations of individual countries. However, since a long time, engineers as well as material scientists are dealing with multiaxial strength in order to use them especially for certain constructions i. e. columns, platforms etc. Lightweight aggregate concrete under triaxial compressive load shows a different failure behavior compared with normalweight concrete. The increase of strength due to confining pressure is not as large as it is with normal weight concrete. It depends on the type of aggregate.

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1317. Gustafsson, P., *'FRACTURE MECHANICS STUDIES OF NON- YIELDING MATERIALS LIKE CONCRETE; MODELLING OF TENSILE FRACTURE AND APPLIED STRENGTH ANALYSIS," Lund University of Technology, Lund, Sweden, 1985, pp. 411.

Fracture mechanics studies of non-yielding material are presented. The studies are based on a theoretical model for the macroscopic mechanical behaviour of materials during tensile stress induced fracture. A number of applied numerical analyses are indicated. Fracture models and strength relations are discussed also from a few more general and fundamental points of view. A number of comparisons are made to test results from literature. The applications concern materials such as concrete, reinforced concrete, mortar and wood. Most numerical calculations are carried out by means of finite element methods. The fracture mechanics model called the fictitious crack model is emphasized. This model gives a description of gradual and localized fracture-softening in a single discrete tensile fracture process region. Other models dealt with are: linear elastic fracture mechanics, Weibull-model, unlimited plasticity, conventional maximum stress theory and a few more special models. Specimens dealt with during numerical calculations are: beams in bending fracture mechanics test specimens, tensile test specimens, pipes in bending and crushing, specimens with a re-entrant corner and longitudinally reinforced concrete beams in shear. According to the results obtained, it seems to be theoretically consistent and often of great practical importance to take into account the gradual and localized fracture-softening during strength analysis of specimens and structural elements.

1318. Hansen, W., "STRUCTURAL DESIGN, CEMENTITIOUS PRODUCTS, AND CASE HISTORIES," Advances in High Strength Concrete, Proceedings/ASCE Convention, Detroit, Michigan, 1985, pp. 105-109.

The technology for producing field placeable concrete with a 28 day compressive strength of 10,000 psi has been available for many years. With the recent use of microsilica as an additive a new generation of high (up to 11,000 psi) and ultra high (above 11,000 psi) strength concretes have been produced using conventional materials and techniques. Due to the increased cost and limited supply of microsilica, concretes containing microsilica will mainly be used in high performance concrete structures such as columns in high rise buildings, prestressed concrete and long span bridges. The present paper discusses a

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new approach to understanding failure mode and load deformation behavior of high strength concrete. It also touches on methods of making high strength concrete with and without microsilica. 4 refs.

1319. Heikkinen, A., "PLASTICIZED CONCRETE - CONCRETE WITH MINERAL ADMIXTURES, Nordisk Betong, Vol. 29, 1985, pp. 19-20.

Comparative tests of concrete with different superplasticizing admixtures ha've shown that improved admixtures based on lignosulphonate are preferable, specially when using blended cements.

1320. HSU, T. C. and Mo, Y. L., "DISCUSSION: SOFTENING OF CONCRETE IN TORSIONAL MEMBERS - DESIGN RECOMMENDATIONS," ACI Journal, July-Aug 1985, pp. 443.

This paper is part of a three-paper series that appeared in the May-June, July-.August, and September- October 1985 issues. Because of the close relationship of the papers, discussion will be published for all three in the July-August 1986 Journal.

1321. Hughes, D., "SULPHATE RESISTANCE OF OPC, OPC/FLY ASH AND SRPC PASTES: PORE STRUCTURE AND PERMEABILITY," Cement and Concrete Research, Vol. 15, No. 6, Nov 1985, pp. 1003-12.

F l y ash is a slow acting pozzolana and requires substantial curing to achieve its potential strength and durability properties. Results are presented of the sulphate resistance, permeability and pore size distribution of ordinary portland cement (opc), opc/fly ash and sulphate resistant portland cement (srpc) pastes variously cured before immersion in 0.7 m sodium sulphate. A range of pores is identified which are particularly suscepti'ble to sulphate attack and a qualitative relationship established between the variation, with curing, of the ,entry size of these pores, the permeability of the pastes and sulphate resistance. (Author/TRRL)

1322. Hyrve, O., "LECA AND HIGH STRENGTH CONCRETE, 'I Nordisk Betong, Vol. 29, 1985, pp. 27.

The Norwegian Company A/S Norsk Leca has developed an improved type of lightweight aggregate that makes it possible to produce concrete with a compressive

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strength of 55-60 n/mm2 at a density of 1.8-2.0 t/m3. On site tests have shown that the concrete is pumpable and mainly has the same properties as ordinary concrete. (Author/TRRL)

1323. Joshi, R. C. and Oswell, J. M. et al., llLABORATORY INVESTIGATIONS ON CONCRETE AND GEOCRETE WITH HIGH FLY ASH CONTENTS," Proceedings of the Seventh International Ash Utilization Symposium and Exposition, Orlando, FL, 1985, pp. 683-691.

The engineering properties of high fly ash (75% replacement of cement), non-air entrained concrete prepared from sub-bituminous Alberta fly ashes are studied. The objective is to evaluate the suitability of the mixtures of cement, fly ash and aggregate as construction material. Compressive and flexural strength of equivalent control mixes without fly ash are also investigated for comparison. The concrete mixes investigated are of medium to low workability, suitable for placement by slip forming and roller compaction, respectively. Compressive and flexural strength of some of the selected concrete mixes prepared through geotechnical method (compacted at optimum moisture content and maximum dry density), called geocrete in this study, are also obtained for comparison. On the basis of various properties such as compressive, flexural, indirect tensile strengths and additional non-destructive tests (pulse velocity) it is concluded that the mixes investigated would allow the use of high fly ash concrete as a construction material for the core of a gravity dam and pavement sub-base or base courses.

1324. Klink, S. A., "ACTUAL POISSON RATIO OF CONCRETE," Journal of The American Concrete Institute, Vo1.82, No.6, Nov-Dec 1985, pp. 813-817.

Tests were carried out on specimens of several types of normal weight and lightweight concretes to determine for each type the Poisson ratio at the centers of the corresponding specimens. Internal strains were measured by means of embeddable strain gage units especially constructed for this investigation. The test results showed that this Poisson ratio, referred to as 'actual' in this paper, is about 55 percent higher than that obtained by the recognized standard test method. The results also showed the existence of a definite relation between the actual Poisson ratio, density, and compressive strength of concrete. An empirical formula was derived for the actual Poisson ratio of concrete, which should

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prove u s e f u l f o r s t r u c t u r a l d e s i g n e r s i n e s t i m a t i n g t h e deformations, displacements , and stresses i n p re - stressed and o r d i n a r y r e i n f o r c e d c o n c r e t e p l a t e s , s h e l l s , and o t h e r t y p e s of c o n c r e t e s t r u c t u r e s .

1325. Klink, S. A . , "ACTUAL ELASTIC MODULUS O F CONCRETE," J o u r n a l of t h e American Concrete I n s t i t u t e , V o l . 82, No.5, Sep-Oct 1985, pp. 630-633.

Tests w e r e c a r r i e d out m specimens of s e v e r a l t y p e s o f normal weight and l i g thwe igh t c o n c r e t e t o de te rmine f o r each t y p e t h e e laszic r.odulus i n compression a t t h e c e n t e r s of t h e cor responding specimens. I n t e r n a l s t r a i n s w e r e measured by means of embeddable s t r a i n gage u n i t s e s p e c i a l l y c o n s t r u c t e d f o r t h i s i n v e s t i g a t i o n . The tes t r e s u l t s showed t h a t t h i s e l a s t i c modulus, referred t o a s ' a c t u a l ' i n t h i s paper , i s about 50 pe rcen t higher t h a n t h a t ob ta ined e i t h e r by t h e s t a n d a r d method o f tes t o r t h e recognized e m p i r i c a l formula. T h e r e s u l t s a l s o showed t h e e x i s t e n c e of a d e f i n i t e r e l a z i o n between the a c t u a l e l a s t i c modulus, d e n s i t y , and compressive s t r e n g t h o f conc re t e . An e m p i r i c a l formula w a s derived f o r t he a c t u a l e l a s t i c modulus o f c o n c r e t e .

1326. Lenschow, R. J., "CONCRETE PLATFORMS I N THE NORTH SEA AND SOME RELATED RESEARCH ON CONCRETE," Ocean Space U t i l i z a t i o n '85, Proceedings of -:he I n t e r n a t i o n a l Symposium, Tokyo, Japan, Vo1.2, ,June 1985, pp. 687- 695.

T h e number of conc re t e p l a t fo rms cn the c o n t i n e n t a l shelf i n t h e North Sea i s i n c r e a s i n g s t e a d i l y and has reached 15 today . Most of them a r e produced i n Norway where the c o n d i t i o n s are p a r t i c u l a r l y advantageous f o r such product ion s t a r t i n g i n d ry dock and c o n t i n u i n g in deep f j o r d . T h e c o n c r e t e mix has gone through more f a c e s , and s t r e n g t h has been i n c r e a s e d each t i m e . The longt ime s t o c h a s t i c l oad ing makes it necessa ry t o c o n s i d e r t h e f a t i g u e behavior of t h e c o n c r e t e p l a t f o r m s . T h e dynamic s t r a i n of c o n c r e t e may be greater t h a n t h e t i m e dependent c reep . Recent r e s e a r c h r e s u l t s are a p p l i e d i n s i m p l i f i e d r u l e s f o r f a t i g u e l i f e of r e i n f o r c e d conc re t e s t r u c t u r e s . These r u l e s are d i scussed .

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1327. Mijnsbergen, J. P. G. and Reinhardt, H. W., "CREEP OF CONCRETE IN SEAWATER, '' Behaviour of Offshore Structures, Proceedings of the 4th International Conference, Delft, Netherlands (Developments in Marine Technology, v 2), 1985, pp. 475-485.

Offshore structures have to be thoroughly designed and analysed. This includes also the effects of creep on deformation and stability. However, there is only scarce information available with regard to the influence of seawater on creep. This paper describes test results of various concrete mixes under constant stress in seawater and saturated lime water. The results are compared with the predictions of a scientific model, the CEB-FIP Model Code and the Netherlands Standard for Reinforced Concrete. Large differences are revealed.

1328. Mindess, S., "RELATIONSHIPS BETWEEN STRENGTH AND MICROSTRUCTURE FOR CEMENT-BASED MATERIALS: AN OVERVIEW," Very High Strength Cement-Based Materials, Materials Research Society Symposia Proceedings, Vol. 42, 1985, pp. 53-68.

The mechanical properties of cement-based materials must be controlled by the microstructure, pore geometry and chemical composition of the cement, by the properties of the aggregate, and by the nature of the cement-aggregate bond. While the precise form of the strength vs. microstructure relationship is as yet only imperfectly understood, enough is known to permit us to predict what alterations in the microstructure are required for the production of materials with very high strengths. There are also techniques available for reducing the brittleness that is often a characteristic of high-strength materials. The present paper presents an overview of the strength vs. microstructure relationships that can be used to predict the properties of high strength cement-based materials, and a brief review of some of the methods for achieving high strengths.

1329. Nallathambi, P. and Karihaloo, B. L. et al., "VARIOUS SIZE EFFECTS IN FRACTURE OF CONCRETE," Cement and Concrete Research, Vol. 15, No. 1, Jan 1985, pp. 117- 126.

The paper reports the results of a series of three- point bend tests on pre-cracked cement mortar and concrete beams. The tests are performed with a view to studying the influence of pre-crack, aggregate and

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specimen s i z e s on the f r a c t u r e of c o n c r e t e . A s imple formula based on the exper imenta l data i s proposed t.ct account f o r a l l t he three s i z e dependent effects. Other parameters having a s i g n i f i c a n t i n f l u e n c e on tke f r a c t u r e of c o n c r e t e are a l s o p o i n t e d o u t .

1 3 3 0 . O'Brien, J. and Burns, N . e t a l . , "VERY EARLY POST- T E N S I O N I N G OF PRESTRESSED CONCFUZTE PAVEMENTS, '' I n t e r i m Report , Texas Un ive r s i ty , Aust in C e n t e r f o r T r a n s p o r t a t i o n Research, Jun 19'35, pp. 184.

Temperature and shr inkage c r a c k s occur i n long prestressed c o n c r e t e pavements du r ing t he f irst n i g h t a f te r c a s t i n g , b e f o r e t he p o s t - t e n s i o n i n g o p e r a t i o n i s performed. Previous pos t - t ens ion ing schedu les and c u r r e n t des ign c r i t e r i a b y ACI , P T I , and AASHTO do not gua ran tee t h a t compression can be in t roduced b e f o r e t h e cracks form. T h i s r e p o r t (1) p r e s e n t s a more detai led d i s c u s s i o n o f t h e problem of t empera tu re arid sh r inkage c racking , ( 2 ) reviews some o f the l i t e r a t u r e on e a r l y c o n c r e t e s t r e n g t h and anchorage zone stresses, (3) describes t e s t s on the c a p a c i t y of anchorage zone f o r very e a r l y pos t - t ens ion ing , and (4) recommends a pos t - t ens ion ing schedule accompanied by des ign a ids . Experimental t es t v a r i a b l e s inc luded s l a b t h i c k n e s s , s t r a n d spacing, anchor s i . z e , and t i m e from c a s t i n g . (Author) Study conducted i n coope ra t ion w i t h t h e F e d e r a l Highway Adminis t ra t ion . T i t l e : P r e s t r e s s e d Concrete Pavement Design--Design and Cons t ruc t ion of Overlay App l i ca t ions .

Research Study

1331. O h a m a , Y . and Demura, K. e t a l . , "DEVELOPMENT O F

A D D I T I O N AND POLYMER IMPREGNATION," Polym Concr U s e s , Mater, and Prop, ACI SP-1985, 1985, pp. 231-247.

SUPER-HIGH-STRENGTH CONCRETE MADE WITH S I L I C A FUME

I n t h e p a s t f e w years , g r e a t e r i n t e r e s t has been focussed on t h e use of s i l i c a fume as a concrete admixture, which i s a by-product i n the manufactur ing p r o c e s s of f e r r o s i l i c o n and metal l ic : s i l i c o n . T h e purpose o f t h i s s tudy i s t o f i n d a p p r o p r i a t e p r o c e s s c o n d i t i o n s f o r developing superh igh s t r e n g t h c o n c r e t e by t h e a p p l i c a t i o n of bo th s i l i c a fume a d d i t i o n and polymer impregnat ion. Base c o n c r e t e was mixed by use o f t h e s i l i c a fume and p o l y a l k y l a r y l s u l f o n a t e - t y p e water-reducing agent , and cured i n a u t o c l a v e o r h o t water. t h e cured base conc re t e was dried, and impregnated wi th polymethyl methacrylate b y thermal polymer iza t ion i n h o t water. The s t r e n g t h p r o p e r t i e s o f such superh igh s t r e n g t h c o n c r e t e w e r e tested.

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1332. Ohgishi, S. and Ono, H . , "EFFECT O F MOISTURE CONTENT ON CREEP OF CONCRETE UNDER UNIAXIAL AND TRIAXIAL COMPRESSIVE STRESS AT NORMAL TEMPERATURE," Za i ryo / Journa l of t h e Soc ie ty of M a t e r i a l s Sc ience , Japan, Vol. 34, No. 376, 1985, pp. 8-13.

T h i s paper r e p o r t s on an exper imenta l program carried o u t t o i n v e s t i g a t e t h e effects of mois ture c o n t e n t on t h e s t r e n g t h and c r e e p of c o n c r e t e under u n i a x i a l and t r i a x i a l (i. e. h y d r o s t a t i c p r e s s u r e ) compressive stress a t 30 DEGREE C. T h e dependence of moi s tu re con ten t on the v i s c o - e l a s t i c i t y of c o n c r e t e w a s d i s c u s s e d r h e o l o g i c a l l y . The t e s t r e s u l t s showed t h a t t he compressive s t r e n g t h , and t h e e l a s t i c s t r a i n , o f c o n c r e t e decreased w i t h i n c r e a s i n g moi s tu re c o n t e n t . I t w a s cons idered t h a t t he s t r e n g t h r educ t ion may be due t o t h e change of s u r f a c e energy, i n t h e hydra t ed cement gel , and t h e larger e l a s t i c s t r a i n a t lower mois ture con ten t level w a s brought i n as t h e r e s u l t of growing of vo id and crack i n c o n c r e t e du r ing d r y i n g procedure. On t h e o t h e r hand, t he mois ture dependency of c reep s t r a i n , was g r e a t l y d i f f e r e n t from t h e case of e las t ic s t r a i n : t he magnitude of c r e e p s t r a i n i n c r e a s e d r a p i d l y wi th i n c r e a s i n g moi s tu re from 0% t o 40%, and t h e n became n e a r l y c o n s t a n t i n t h e range of 40% over . I n Japanese w i t h Eng l i sh abstract .

1333. ONO, S. and KIMURA, K . e t a l . , "EVALUATIONS O F EXTERNAL RESTRAINING EFFECT AND PREDICTION METHOD FOR THERMAL CRACKS I N H I G H STRENGTH LIGHTWEIGHT CONCRETE," Doboku Gakkai Rombun Hokokushu, Feb 1985, pp. 147-155.

There are a number of unsolved problems r ega rd ing t h e c o n t r o l of thermal c rack ing i n massive c o n c r e t e s t r u c t u r e s us ing high s t r e n g t h l i gh twe igh t c o n c r e t e . The purposes of t h e p r e s e n t i n v e s t i g a t i o n are t o evaluate t h e degree of external r e s t r a in t on t h e basis of exper imenta l d a t a and t o examine t h e p r e d i c t i o n method f o r t he thermal crack p r o p e r t i e s o r i g i n a l l y developed f o r normal weight conc re t e f o r i t s a p p l i c a t i o n t o h igh s t r e n g t h l i gh twe igh t c o n c r e t e .

1334. Ozyi ld i r im, C. and Walker, H . , "EVALUATION O F HYDRAULIC CEMENT CONCRETES CONTAINING SLAG ADDED AT THE MIXER," V i r g i n i a Highway & Transpor t a t ion Research Counci l , F i n a l Rpt . , J u l 1985, pp. 38.

T h e s tudy eva lua ted t h e effect of ground, g r a n u l a t e d , i r o n b l a s t - f u r n a c e s l a g s on t h e p r o p e r t i e s of h y d r a u l i c cement conc re t e s such as normally used i n highway c o n s t r u c t i o n . Two cements w i t h d i f f e r e n t a l k a l i c o n t e n t s and two slags w i t h d i f f e r e n t a c t i v i t y

1 4 1

i n d i c e s , 1 0 0 and 1 2 0 , were used. S l ags w e r e used as replacements f o r p o r t i o n s of p o r t l a n d cement a t 40%, 50%, and 65% by weight. T h i s f i n a l r e p o r t p r e s e n t s d a t a on the p r o p e r t i e s of t h e f r e s h l y mixed c o n c r e t e and t h e t es t r e s u l t s on time of se t , heat of hydra t ion , compressive s t r e n g t h , f l e x u r a l s t r e n g t h , p e r m e a b i l i t y , r e s i s t a n c e t o f r e e z i n g and thawing, l e n g t h change va lues , and t h e r e s u l t s of p e t r o g r a p h i c examinat ions i n c l u d i n g d a t a on a i r vo ids , carabonat ion , and hydra t ion . The t es t r e s u l t s f o r t h e l a b o r a t o r y specimens i n d i c a t e t h a t mix tu res w i t h t h e slags e x h i b i t delay i n set and s:Lower development of compressive s t r e n g t h a t ea r ly ages t h a n do convent iona l mix tures , bu t have equa l o r better s t r e n g t h s a t l a t e r ages. T h e i n c o r p o r a t i o n of s lag reduces t h e p e r m e a b i l i t y of c o n c r e t e cons ide rab ly . I t i s conducted from t h i s s tudy t h a t c o n c r e t e s i n which up t o 50% by weight of t he cement has been r e p l a c e d w i t h a s l a g meeting the requi rements of ASTM C989 and having a minimum a c t i v i t y index of 1 0 0 are s a t i s f a c t o r y f o r u se i n highway c o n s t r u c t i o n .

1335. Rasmussen, T . , "LONG TERM D U R A B I L I T Y OF CONCRETE, 'I

Nordic Concrete Research, No. 4 , Dec 1985, pp.159-178.

The long-term d u r a b i l i t y c h a r a c t e r i s t i c s of var ious, t y p e s o f c o n c r e t e exposed t o v a r i o u s environments w a s i n v e s t i g a t e d . The p r o j e c t was carried o u t as s e m i - f u l l scale p r o j e c t w i t h a t o t a l c o n c r e t e volume o f 2 rr~ f o r each of t h e 16 d i f f e r e n t t y p e s of c o n c r e t e . T e s t s w i t h t h e f u l l - s c a l e specimens inc luded b o t h d e s t r u c t i v e and nondes t ruc t ive tests. I n a d d i t i o n t o t h e larger specimens a number of l a b o r a t o r y specimens were cast i n o r d e r t o provide i n . i t i a l data on t h e q u a l i t y of t he conc re t e .

1336. Reinhard t , H. , "CRACK SOFTENING ZONE I N PLAIN CONCRETE UNDER STATIC LOADING, I' Cement and Concrete Research, V o l . 15 No. 1, Jan 1985, pp. 42-!52.

S t a r t i n g from the f i c t i t i o u s crack model t h e s o f t e n i n g zone a t t he t i p of a discrete crack i n c o n c r e t e i s s t u d i e d . Using a power r e l a t i o n f o r t h e stress d i s t r i b u t i o n i n t h e s o f t e n i n g zone, t h e e x t e n s i o n of t h i s zone i s a func'zion of t h e exponent . If t he f u l l y s o f t e n e d c r o s s - s e c t i o n i s t aken as a f a i l u r e c r i t e r i o n , t he exponent can be cons ide red a s a measure f o r t h e t r u e s t r e n g t h of t he m a t e r i a l . Suppor t ing t h e theo ry conc re t e p l a t e s w e r e tested under u n i a x i a l t e n s i l e loading . S ince stress d i s t r i b u t i o n cannot be measured -:he s t r a i n d i s t r i b u t i o n around t h e c rack w a s determined. Using

1 4 2

the complete stress-strain relation the strains were translated into stresses. The test results are discussed and compared to the theoretical model. Further studies are encouraged to improve the accuracy of the experiments and to extend the model to cyclic loading.

1337. Roy, D. M. and Nakagawa, Z.-e. et al., "OPTIMIZED HIGH STRENGTH MORTARS: EFFECTS OF CHEMISTRY, PARTICLE PACKING, AND INTERFACE BONDING," Materials Research Society Symposia Proceedings, Vol. 42, 1985, pp. 245- 252.

High strength mortars have been prepared utilizing optimized particle packing, reactive substituents to modify the chemistry, and addition of superplasticizers. Otherwise the processing techniques were conventional. The compressive strengths of one prototype material after curing at temperatures from 38 C to 250 C were above 70 MPa. The strengths were particularly high at 175 C (195 MPa) where excellent bonding had deve1oped;one chemically modified material reached 245 MPa. At lower curing temperatures the strength increased with time, apparently still increasing at 5 6 days (106 MPa) for the materials cured at 38 C. Modified mixtures were prepared using different proportions of silica fume, MgO, different ratios of sand to fine components, and different sand mineralogy and other admixture proportions for rheological optimization. Microhardness, dynamic Young's modulus, density, and permeability were measured.

1338. Sakata, K. and Ikeda, K., "STUDY ON PREDICTION OF CREEP OF CONCRETE," Transactions of the Japan Society of Civil Engineers, Vol. 15, 1985, pp. 520-522.

The paper reports on creep tests carried out on various kinds of concretes and concrete mixes. It was found that the time dependent behavior of elastic strain under sustained load can be predicted. The effect of composition of concrete mix is estimated by the function of cement and water content. A new equation is proposed that can estimate rather accurately the effects of age at loading, size of specimen and ambient relative humidity on creep of concrete. The equation is applied to predict creep strain.

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1339. S a k a t a , K. and Yamura, K . e t a l . , "STUDY ON FATIGUE PROPERTIES OF CONCRETE UNDER VARIABLE REPETITIVE COMPRESSIVE LOADING, I' Trans Jpn Conc:r I n s t , Vol .7 , 1985, pp. 257-262.

Exper imen ta l r e s e a r c h on t h e b e h a v i o r of p l a i n c o n c r e t e s u b j e c t e d t o variable repet i t ive l o a d s i s described. Cons tan t - ampl i tude f a t i g u e t e s t s and variable l o a d f a t i g u e tests are per formed. F a t i g u e characterist ics o f c o n c r e t e unc.er variable r e p e t i t i v e l o a d i n g are d i s c u s s e d and f a t i g u e 1:ives o f c o n c r e t e are e v a l u a t e d by Miner sum. Also , the a p p l i c a b i l i t y ,of Mine r ' s h y p o t h e s i s t o f a t i g u e cmf c o n c r e t e i s examined. From t h e e x p e r i m e n t a l r e s u l t s , it c a n be conc luded t h a t Mine r ' s h y p o t h e s i s i s applicable t o t h e e s t i m a t i o n o f f a t i g u e l i f e o f c o n c r e t e s u b j e c t e d t o random l o a d i n g .

1 3 4 0 . Schmidt , H. and O p i t z , H . e t a l . , "IJLTIMATE STRENGTH AND STRESS-DEFORMATION BEHAVIOF. OF CONCRETE UNDER

Vol. 39, NO. 9, 1985, pp . 400-403 . MULTIAXIAL STRESS STATES," Bauplanung - Bautechn ik ,

Problems a r i s i n g d u r i n g test.s i n v o l v i n g a r b i t r a r y homogeneous compress ion stress states i n c o n c r e t e t es t specimens are b r i e f l y p r e s e n t e d . Expe r imen ta l resu l t s c o n c e r n i n g s t r e n g t h b e h a v i o r unde r t r i a x i a l compress ion stresses are descri.bed by means of fracture l i m i t l i n e s and s t r e s s - d e f o r m a t i o n r e l a t i o n s f o r c o n c r e t e unde r m u l t i a x i a l c:ompression l o a d i n g a re derived. I n i t i a l test r e s u l t s are g i v e n f o r t h e s t r e n g t h and d e f o r m a t i o n behavi.or of c o n c r e t e u n d e r t r i a x i a l tension-compression-cc)mpression stresses. ( T r a n s l a t e d a u t h o r abstract)

1 3 4 1 . S c h r a d e r , E . K., "DESIGN METHODS FO:R PAVEMENTS W I T H SPECIAL CONCRETES, I' American C o n c r e t e I n s t i t u t e , Nov 1985, pp. 331.

A method f o r a d a p t i n g e x i s t i - n g pavement t h i c k n e s s d e s i g n c u r v e s and fo rmulas f o r ' special ' c o n c r e t e s i s p r e s e n t e d . The need f o r d o i n g t h i s i s d i s c u s s e d ; i .e . , special c o n c r e t e s made w i t h f i b e r - r e i n f o r c e d o r h igh - range w a t e r - r e d u c e r s have mater ia l p r o p e r t i e s ( s p e c i f i c a l l y changed f a t i g u e endurance and the effects o f m a t u r i t y ) which are d i f f e r e n t from the long-assumed p r o p e r t i e s t h a t 'normal c o n c r e t e s ' p o s s e s s and upon which c u r r e n t d e s i g n c u r v e s a re based.

:I 4 4

1342. Shrive, N. G. and El-Rahman, M., "UNDERSTANDING THE CAUSE OF CRACKING IN CONCRETE: A DIAGNOSTIC AID," Concrete International: Design and Construction, Vo1.7, No.5, May 1985, pp. 39-44.

An understanding of the cause of cracking in concrete is necessary if correct diagnosis is to be made of the macroscopic conditions which induced the distress. Plain concrete is shown to behave like other so-called brittle materials under different states of stress. It is shown that the development of tensile stresses around voids initiates cracking. This simple theorem is confirmed by comparing experimental results with predicted behavior in terms of cracking for a variety of stress states, including compression.

1343. Smadi, M. M. and Slate, F. 0. et al., "HIGH-, MEDIUM-, AND LOW-STRENGTH CONCRETES SUBJECT TO SUSTAINED OVERLOADS-STRAINS, STRENGTHS, AND FAILURE MECHANISMS,

No.5, 1985, pp. 657-664. Journal of The American Concrete Institute, Vo1.82,

The behavior of high-strength concrete subject to high sustained compressive stresses was studied experimentally and compared with that of low- and normal-strength concretes. Various forms of stress- strain-time relationships were obtained. The long-term sustained strengths were established for these materials and were found to be greater (as percent of f'c) for high-strength than for low-strength concretes by about 5 to 10 percent. The time-dependent deformations were maximum at the vicinity of the sustained strength and were greater the lower the strength of concrete.

1344. Smutzer, R. and Zander, A., "A LABORATORY EVALUATION OF THE EFFECTS OF RETEMPERING PORTLAND CEMENT CONCRETE WITH WATER AND A HIGH-RANGE, WATER-REDUCING ADMIXTURE," Transportation Research Record, N1040, 1985, pp. 34-39.

This laboratory evaluation study was initiated to appraise the general amount and rate of slump loss of portland cement concrete (PCC) and to determine the effects of retempering concrete with water and a high- range water-reducing (HRWR) admixture. Three different concrete mix designs were considered in this laboratory evaluation: (a) air-entrained, Type I11 PCC; (b) air-entrained, Type I11 PCC with a type A chemical admixture (for conventional water reduction); and (c) air-entrained, Type I11 PCC with an HRWR admixture system. The evaluation consisted of eight

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c o n c r e t e ba t ches wi th c o n c r e t e t e s t i n g and sampling be ing done f o r t h e i n i t i a l c o n c r e t e c o n d i t i o n s and t h e f i n a l ( re tempered) c o n c r e t e c o n d i t i o n s . One HRWR admixture system w a s eva lua ted d u r i n g t h i s s tudy because, a t t h e p r e s e n t t i m e , t h e Indiana Department o f Highways ( I D O H ) has approved only two HRWR admixture systems, and t h e two HIWR admixtures t h a t a r e used i n these systems are g e n e r i c a l l y s imilar i n form. I t w a s concluded t h a t PCC wi th an HRWR admixture system should no t be retempered with an a d d i t i o n a l HRWR admixture t o r e g a i n c o n c r e t e slump a f t e r i t s i n i t i a l l o s s f o r c o n c r e t e a p p l i c a t i o n s t h a t r e q u i r e a good freeze- thaw d u r a b i l i t y , ( i . e . , t h e m a j o r i t y of t h e highway c o n c r e t e a p p l i c a t i o n s t h a t are exposed t o t h e e l e m e n t s ) . T h i s recommended l i m i t a t i o n has already been adopted by t h e I D O H . T h i s paper appeared i n T r a n s p o r t a t i o n Research Record N I 0 4 0 , Concrete Pavement Cons t ruc t ion .

1345. S p r i n k e l , M., "RADIANT HEAT CURING OF CONCRETE," Fina.1 R p t . , V i r g i n i a Highway C T r a n s p o r t a t i o n Research Council , May 1985, pp. 4 6 .

Comparisons w e r e made of t he p r o p e r t i e s o f c o n c r e t e mix tu res cu red wi th r a d i a n t heat and mixtures cu red w i t h low p r e s s u r e steam and of the c u r i n g c o n d i t i o n s . The c o n c r e t e w e r e p repa red and cu red a t two p l a n t s which produce p r e c a s t , prestressed c o n c r e t e p r o d u c t s and i n t h e Research Council l a b o r a t o r y . The r e s u l t s i n d i c a t e t h a t r a d i a n t heat c u r i n g used i n combinat in w i t h a membrane cu r ing compound can produce an a c c e p t a b l e conc re t e . Compresive s t r eng th , f reeze- thaw performance, and p e r m e a b i l i t y t o c h l o r i d e i o n s w e r e n o t s i g n i f i c a n t l y d i f f e r e n t f o r c o n c r e t e s cu red w i t h t h e two c u r i n g methods. The c u r i n g achieved a t t h e p l a n t w i t h r a d i a n t h e a t w a s found t o be much less uniform t h a n t h a t w i t h low p r e s s u r e steam b u t was adequate when p rope r p r e c a u t i o n s w e r e e x e r c i s e d . Therefore , it i s recommended that: beds should be s u i t a b l y enc losed and t h a t h e a t pipes be p r o p e r l y p o s i t i o n e d t o minimize tempera ture d i f f e r e n t i a l s th roughout t h e member. A l s o , c y l i n d e r s shou ld be cu red a t t he same tempera ture used i n cuur ing t h e leas t mature p a r t of t h e m e m b e r .

1346. S t o l l , U . W . , "COMPRESSIVE STRENGTH MEASUREMENT WITH THE STOLL T O W TEST," Concrete I n t e r n a t i o n a l : Design and Cons t ruc t ion , V o l . 7, N o . 1 2 , 1985, pp. 42-47 .

T h e S t o l l Tork T e s t ( S T T ) i s t i new, n o n d e s t r u c t i v e means f o r a s s e s s i n g the compresslve s t r e n g t h w i t h i n a c o n c r e t e s t r u c t u r e . The p ro to type device i s comprised.

1 4 6

of a special bolt extension and small, removable cleated spindle which is positioned in the plastic concrete. Results of reconnaissance tests, measuring peak torque resistance and associated compressive strength with the device embedded into the end of test cylinders and through sides of wall forms and test blocks are summarized. Tests involved locally available commercial concrete comprised of natural gravel, crushed limestone, or blast furnace slag aggregate.

1347. Suzuki, K. and Nakagawa, T. et al., "APPLICATION OF SUPERPLASTICIZER FOR SHORTENING CONSTRUCTION PERIOD," Trans of the Jpn Concr Inst, Vol. 6, 1985, pp. 15-22.

To get very high rate of hardening of concrete such as ultra-high-early-strength portland cement, the new application method of superplasticizer in which the combination of high-early-strength portland cement and super-plasticizer is used instead of ordinary portland cement of conventional concrete. The method was investigated by laboratory test and applied to a building construction project with successful result.

1348. Tazawa, Y. and Nobuta, Y. et al., "FREEZING-AND- THAWING RESISTANCE OF HIGH-STRENGTH LIGHTWEIGHT CONCRETE USING SILICA FUME," Trans Jpn Concr Inst, V01.7, 1985, pp. 127-134.

This paper describes the results of experimental research on strength development and freezing-and- thawing resistance of high-strength lightweight concrete incorporating silica fume. The variables for the experiment were type and moisture content of lightweight aggregate and dosage of silica fume. Test results showed the compressive strength of the lightweight concrete substantially increased with using silica fume regardless of type and moisture content of the lightweight aggregate. And the freezing-and-thawing resistance of the lightweight concrete was mainly influenced by the moisture content of lightweight aggregate. From these results, it was concluded that high-strength durable lightweight concrete satisfying the requirement for concrete structures to be used in severe condition such as the arctic region could be obtained by using low moisture lightweight aggregate together with silica fume.

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1349. Tinic, C. and Bruehwiler, E., "EFFECT OF COMPRESSIVE

STRAIN RATES," International JournaIL of Cement Composites and Lightweight Concrete,. Vo1.7, No.2, May

LOADS ON THE TENSILE STRENGTH OF CONCRETE AT HIGH

1985, pp. 103-108.

This paper describes the behavior of concrete subjected to tensile loads at high strain rates with and without compressive load histories. The tests, carried out at the laboratory of building materials of the Swiss Federal Institute of Technology, Zurich, show a considerable deterioration of the tensile strength due to initially applied compressive loads.

1350. Tjugum, O., "LATEX-MODIFIED CONCRETE, 'I Nordisk Betong, Vol. 29 NO. 2, 1985, pp. 15-17.

Latex-modified concrete overlays have been in service for over 20 years in the USA. Latex as an admixture is now being introduced in Norway. The physical and chemical properties of latex modified concretes and their use in practice are discussed.

1351. Ueber Das Kriechverhalten Von Fruehzeitig Belasteten, W. B., "CREEP BEHAVIOR OF HEAT-TREATED CONCRETES

VOl. 51, NO. 6, 1985, pp. 369-373. LOADED AT AN EARLY AGE," Betonwerk Fertigteil Tech,

The shrinkage and creep of heat-treated concretes made with two grades of Portland cement (PZ 35 F and PZ 55) were investigated. The tests show that both the shrinkage and the creep of heat--treated concretes are less than those of normally cured comparison concretes loaded at the same ace. For very early load application and long periods of load duration the creep strains of heat-treated c:oncretes can be calculated with sufficient accuracy by the method given in DIN 4227, Part 1. For calculating the cree:p strains in the first few days 2nd weeks after load application, however, the DIN 4227 method is not always sufficiently accurate.

1352. Warner, R., "DESIGN OF CONCRETE: STRTJCTURES FOR FATIGUE RELIABILITY," Adelaide University, Australia Department of Civil Engineerinq, Apr 1985, pp. 24.

Four different limit states formats for the fatigue design of reinforced concrete and prestressed concrete s t r u c t u r e s a r e descr ibed and ccmpared wi th in t h e context of simple second level reliability theory.

1.48

All four formats lend themselves to reliability treatment but the cycle format appears to be the most useful at the present time, given the limited quantity of design data available on the fatigue properties of the component materials. The problem of choosing appropriate reliability levels for fatigue design is also studied. A comparative calibration method is used to identify a range of acceptable values for the nominal probability of fatigue failure and the associated reliability index B. A design procedure for fatigue is finally proposed which incorporates the results of the present study.

1353. Williamson, R., "METHODS FOR DETERMINING THE WATER AND CEMENT CONTENT OF FRESH CONCRETE," Mater Struct, No. 106, Jul-Aug 1985, pp. 269-278.

Quality control of concrete has taken many forms in past years. Several accelerated testing techniques have been developed recently, and although these tests are accomplished in one or two days, as compared to the usual 28 days, they still are conducted on hardened concrete. The ideal test, of course, is a test that can be conducted on the plastic or fresh concrete. It is these methods of analysis that area being discussed in this paper. Of the many factors that affect the strength and durability of the concrete, the water and the cement contents are the most critical. These parameters expressed in terms of water to cement ratio provide the best indicator of the quality of the concrete. They are the prime factors in controlling the porosity, strength and durability of the hardened concrete.

1354. Williamson, R. B. and Rashed, A . I., "HIGH STRENGTH CONCMTE AND MORTARS IN HIGH TEMPERATUM ENVIRONMENTS," Materials Research Society Symposia Proceedings, Vol. 42, 1985, pp. 295-303.

A number of new materials are presently being introduced for application in high temperature environments. Though some of these are old materials fabricated with new methods or processes, many are actually new. A typical example is the use of ceramic fiber blankets for the interior of furnaces. This paper focuses on the use of high strength concretes or mortars for application to high temperature environments, such as furnaces or boilers for coal gasification and similar processes requiring high pressure and temperature.

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1355. Young, J. F. (Ed. ) , "VERY H I G H STRENGTH CEMENT-BASED MATERIALS, 'I M a t e r i a l s Research S o c i e t y Symposia Proceedings, V o l . 42 , 1985, pp. :317.

T h i s symposium proceedings c o n t a i n s 2 9 pape r s d e a l i n g w i t h new developments i n t h e a r e a of cemen t i t i ous materials. The t o p i c s covered inc lude : m i c r o s t r u c t u r e of high s t r e n g t h p a s t e systems; u l t r a h i g h s t r e n g t h c o n c r e t e p r o p e r t i e s ; high s t r e n g t h au toc laved mortars ; cement based mater ia l f r a c t u r e toughness; cement paste p o r e - s t r u c t u r e ; h y d r a u l i c cement paste p o r o s i t y ; h igh - s t r eng th c o n c r e t e mix p ropor t ion ing ; h igh s t r e n g t h morzar aggrega tes ; high- s t r e n g t h mor ta r op t imiza t ion ; macro-defect- f ree cement p r o p e r t i e s ; polymer impregnation of cemen t i t i ous composite materials; m i c r o s i l i c a c o n c r e t e technology.

1356. Zaitsev, Y . V. and Kovler, K. L . , "NClTCH SENSITIVITY OF CONCRETE AND SIZE EFFECT. P m r I : EFFECT OF

Cement and Concrete Research, V o l . 15, No. 6, 1985, SPECIMEN SIZE AND CRACK LENGTH BY 3-POINT B E N D I N G , "

pp. 979-987.

T h e problem of notch s e n s i t i v i t y of c o n c r e t e i s d i s c u s s e d w i t h t h e i n f l u e n c e of s i z e effect t aken i n t o account . T h e need t o cons ide r t h e s i z e effect on t h e t e n s i l e s t r e n g t h o f conc re t e w a s no ted . I t i s shown t h a t t h e c r i t i c a l stress i n t e n s i t y f a c t o r , K(**IC), ~ L S

connected w i t h t h e t e n s i l e s t r e n g t h clf t h e material , w h i c h gives an oppor tun i ty t o estimate t h e K ( * * I C ) - value on t h e resul ts of s t a n d a r d s t r e n g t h tes ts of t h e unnotched specimens. I n c o n c l u s i ' m , a. p r a c t i c a l c o n d i t i o n f o r quas i -b r i t t l e manner of f a i l u r e has been found .

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1986

1357. Ahmad, S. H. and Shah, S. P. et al., "ORTHOTROPIC MODEL OF CONCRETE FOR TRIAXIAL STRESSES," Journal of Structural Engineering, Vol. 112, No. 1, 1986, pp. 165-181.

An orthotropic model to predict the ascending and descending parts of the stress-strain curves of concrete subjected to biaxial or triaxial compressive stresses is presented. The stress-induced orthotropic material properties are expressed in terms of six constants in the compliance matrix. The six material constants are expressed as functions of stress invariants at ultimate strength. The proposed orthotropic constitutive model depends on the knowledge of the three principal stresses at the maximum strength, which are obtained through the use of a strength criterion (which is sensitive to all the three stress invariants). For predicting the ascending and descending parts of the multiaxial stress-strain curves, the six orthotropic material constants in the compliance matrix are continuously changed with the help of a 'fracturing index' parameter.

1358. Alliche, A. and Francois, D., "FATIGUE BEHAVIOR OF HARDENED CEMENT PASTE, I' Cement and Concrete Research, Vol. 16, No. 2, 1986, pp. 199-206.

The fatigue behavior of cement hardened paste was studied in compression loading with an R ratio equal to 10. The samples were immersed in water at room temperature. The fatigue life as a function of the stress amplitude, displayed a large scatter. The longitudinal and the radial deformations were recorded. A very good correlation was found between the fatigue life and the deformation rate per cycle during steady state. The acoustic emission and the ultrasonic waves attenuation displayed the same behavior as the deformation rate.

1359. Bailey, J. E. and Chanda, S. et al., "FRACTURE MECHANICS AND FAILURE PROCESSES IN POLYMER MODIFIED AND BLENDED HYDRAULIC CEMENTS," Fracture Mechanics of Ceramics (Proceedings of the Fourth International Symposium), Blacksburg, VA, Volume 7, 1986,

This paper reviews evidence for a model for the fracture of Portland cement pastes. These materials exhibit a yielding phenomenon, and fracture mechanics results suggest that a tied-crack model is the

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s i m p l e s t d e s c r i p t i o n of t h e f rac ture : p r o c e s s . R e s u l t s have been ob ta ined on normal cement p a s t e s , a blended cement p a s t e and high s t r e n g t h polymer modif ied cements. Sugges t ions are made as t o t h e p o s s i b l e effects o f changes i n t he m i c r o s t r u c t u r e on t h e f r a c t u r e p rocess , w i t h consequent effects on t h e f l e x u r a l s t r e n g t h .

1 3 6 0 . Banthia , N . P . and Mindess, S. e t a].., ' "HIGH STRESS RATE TESTING OF CONCRETE: AN OVERVIEW,'' I nd ian Concrete Jou rna l , V o l . 60 , No. 10, 1.986, pp. 265-2711..

T h e paper describes t h e r e s u l t s o f impact tes ts carried o u t u s i n g an ins t rumented drop weight impact a p p a r a t u s . Concrete beams made wi th normal s t r e n g t h conc re t e , h igh s t r e n g t h conc re t e , normal s t r e n g t h c o n c r e t e and steel f ibers, normal s t r e n g t h c o n c r e t e and polypropylene fibers, and normal s t r e n g t h c o n c r e t e w i t h convent iona l re inforcement w e r e tested. I n g e n e r a l , f o r a given drop hammer h e i g h t , h igh s t r e n g t h c o n c r e t e was more b r i t t l e t h a n normal s t r e n g t h c o n c r e t e . F i b e r s , p a r t i c u l a r l y t he s teel f ibers, w e r e v e r y effective i n i n c r e a s i n g t h e energy-absorp t ion capacity o f t h e conc re t e . All of t h e c o n c r e t e s testmed w e r e found t o r e q u i r e higher f r a c t u r e e n e r g i e s under impact l o a d i n g t h a n under s t a t i c l oad ing .

1361 . Bentur, A. and Mindess, S . , "EFFECT OF CONCRETE STRENGTH ON CRACK PATTERNS," Cement and Concrete Research, V o l . 16, No. 1, 1986, pp. 59-66.

I t i s w e l l known t h a t t h e cracks t h a t develop i n c o n c r e t e as it i s loaded t o f a i l u r e are affected b y t h e aggrega te p a r t i c l e s , partic:ular:Ly by t h e c o a r s e aggrega te . Because of the v e r y d i f f e r e n t f r a c t u r e e n e r g i e s of t he hydra ted cement m a t r i x and t h e aggregate p a r t i c l e s , t h e d e t a i l s o f t h e c rack p a t h a r e impor tan t i n de te rmining t h e f r a c t u r e energy of t h e composite. I t i s commonly assumed t h a t , f o r normal mortars o r concretes, c racks t end t o go around aggrega te p a r t i c l e s . For h igh s t r e n g t h conc re t e , some cracks w i l l go through t h e aggrega te p a r t i c l e s , though t h e more common crack p a t h w i l l . s t i l l be around t h e aggrega te . T h e purpose of t he p r e s e n t s tudy w a s t o compare t h e crack p a t t e r n s that. developed i n d i f f e ren t t y p e s o f p l a i n c o n c r e t e us ing specimens i n which t h e stresses o f t h e crack t i p were p r i m a r i l y t e n s i l e . I n a d d i t i o n , the effect of l oad ing r a t e on t h e c rack p a t t e r n w a s a l s o s t u d i e d .

1.52

I

1362. Bremner, T . W . and Holm, T . A., "ELASTIC COMPATIBILITY AND THE BEHAVIOR OF CONCRETE," ACI Jou rna l , March- A p r i l 1986, pp. 244-250.

Concrete i s cons ide red a p a r t i c u l a t e composite i n which t h e c o a r s e aggregate acts as a s p h e r i c a l i n c l u s i o n i n an i n f i n i t e ma t r ix o f mor ta r . Equat ions developed by Goodier a r e used t o c a l c u l a t e t h e stresses t h a t develop i n and around t h e aggregate i n c l u s i o n s . With o rd ina ry conc re t e , l a r g e stresses develop a t t h e i n t e r f a c e a s a r e s u l t of t h e large d i f f e r e n c e i n e las t ic modulus between t h e aggregate and the ma t r ix . With s t r u c t u r a l l i gh twe igh t conc re t e , t h e e las t ic modulus of t h e i n c l u s i o n (expanded aggregate) i s s imilar t o t h a t o f t h e mat r ix , r e s u l t i n g i n s i g n i f i c a n t l y lower stress c o n c e n t r a t i o n s deve loping a t t h e aggregate-matr ix interface. E l a s t i c a l l y matched c o n s t i t u e n t s w i l l r e s u l t i n lower levels o f t h e stress a t t h e i n t e r f a c e and less microcracking. Evidence i s p r e s e n t e d t o suppor t t h e v i e w t h a t more uniform d i s t r i b u t i o n of stress w i t h i n l ightweight c o n c r e t e w i l l compensate f o r t h e lower par t ic le s t r e n g t h of t h e expanded aggregate. I n c o r p o r a t i o n of e n t r a i n e d a i r i s shown t o promote e las t ic mismatching i n o rd ina ry c o n c r e t e because it i n c r e a s e s t h e d i f f e r e n c e i n s t i f f n e s s between the i n c l u s i o n and the ma t r ix . With s t r u c t u r a l l igh tweight c o n c r e t e s , e n t r a i n e d a i r lowers the s t i f f n e s s of the mor tar m a t r i x s o t h a t it approaches t he s t i f f n e s s of t h e expanded aggregates, r e s u l t i n g i n a more uniform stress d i s t r i b u t i o n . A t t h e p o i n t of e l a s t i c c o m p a t i b i l i t y of t h e two phases , e x t e r n a l l oad ing w i l l develop a stress concen t r a t ion f a c t o r approaching u n i t y and t h e stress a t t h e i n t e r f a c e pe rpend icu la r t o t h e d i r e c t i o n of t h e a p p l i e d l o a d w i l l approach ze ro . I n a d d i t i o n t o c o n t r i b u t i n g t o e f f i c i e n t s t r e n g t h development, r educ t ion i n microcracking should s u b s t a n t i a l l y reduce t h e i n g r e s s of water and c h l o r i d e s i n t o t h e concrete as t h e p a t h s of easy flow a r e minimized.

1363. Brooks, J. J. and Forsy th , P . , "INFLUENCE OF FREQUENCY O F CYCLIC LOAD ON CREEP OF CONCRETE," Magazine o f Concre te Research, V o l . 38, N o . 136, Sept 1986, pp. 139-150.

Short-term c r e e p of s e a l e d and d ry ing c o n c r e t e under a s i n u s o i d a l compressive l o a d has been determined a t v a r i o u s f r equenc ie s ranging from 1 cycle p e r day t o 1 H z . Under c y c l i c loading , c r e e p has t o be def ined c a r e f u l l y because of t h e changing shape of t he s t r e s s - s t r a i n curve. Between f r equenc ie s o f 1 c y c l e p e r day and 3 0 c y c l e s p e r hour, t h e i n c r e a s e i n c r e e p

153

under a cyclic load is approximately equal but, at higher frequencies, there is a fiurther increase in creep. Expressions are given which give estimates of the full strain cycle when the static creep is known.

1364. Buenfeld, N. R. and Newman, J. I3., vvPERMEABILITY OF MARINE CONCRETE, 'I Marine Concrete, Papers for the International Conference on Concrete in the Marine Environment, London, England, Sep 22-24, 1986, pp. 165-176.

The durability of concrete in the marine environment depends primarily upon its low permeability. Initial surface absorption, chloride ion diffusion and electrical resistivity test results show that the permeability of sea-water exposed concrete reduces significantly with time. This reduction is due to the formation of a discrete layer on the surface of the cement paste, together with a more widespread bulk effect associated with a modification of the pore structure. The surfac:e layer generally consists of i i brucite (magnesium hydroxide) layer, which is in evidence after only one day, overlain by a more slowly developing skin of aragonite (calcium carbonate) .

1365. Cornelissen, H. A. W. and Reinhardt, H. W., "EFFECT OF STATIC AND FATIGUE PRELOADING ON RESIDUAL STRENGTH AND STIFFNESS OF PLAIN CONCRETE," Fracture Control of Engineering Structures, Proceedings of the 6th Biennial European Conference on Fracture, Vol. 3 , Jun 15-20, 1986, pp. 2087-2103.

The effect of compressive and tensile static as well as repeated tensile and alternating tensile- compressive fatigue preloadings on the reloading stress-strain relations in both compression and tension was experimentally investigated. For accurate control of the fatigue tests a newly developed system based on cyclic strain ra te was applied. It was found that of all loading combinations, compressive preloading had a most detrimental influence on tensile reloading strength, but especially on reloading stiffness. These findings were explained on the basis of internal microcracking.

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1366. Cornelissen, H. A. W. and Hordijk, D. A . et al., "EXPERIMENTAL DETERMINATION OF CRACK SOFTENING CHARACTERISTICS OF NORMALWEIGHT AND LIGHTWEIGHT CONCRETE," Heron, Vol. 31, No. 2, 1986, pp. 45-56.

For modeling fracture behavior of concrete, various types of deformation-controlled uniaxial tests were performed on normalweight and lightweight concretes. These two types of concrete were compared with respect to their envelope curves, material stiffness, and degradation during post-peak cycles and residual compressive deformation on crack closure. Differences in behavior were explained on the basis of the properties of the aggregates that result in specific fracture surfaces. Based on narrow specimens with uniform stress distribution, unique stress deformation curves were determined, and the descending branches were modeled. These models were applied to calculate the stress distribution in wide specimens with a sawcut. The total force was in good agreement with the experiment. Probable reasons for the different behavior of lightweight and normal-weight concretes are discussed.

1367. Diamond, S., "CHLORIDE CONCENTRATIONS IN CONCRETE PORE SOLUTIONS RESULTING FROM CALCIUM AND SODIUM CHLORIDE ADMIXTURES, I' ASTM Cement, Concrete, and Aggregates, Vol. 8 No. 2, 1986, pp. 97-102.

Cement pastes prepared from a 'typical' ASTM Type I portland cement at a water/cement ratio of 0.50 were mixed with various calcium chloride (CaC12) admixture treatment levels, hydrated for various periods, and then subjected to pore solution expression. The expressed pore solutions were then analyzed for chloride and hydroxide ion concentrations. It was found that the concentration of chloride ions drops rapidly but reaches an equilibrium level by about ten days. The equilibrium concentrations attained varied between 20 and 50% of the original concentration in the mix water, the latter value being for the highest CaC12 treatment level, 2% by weight of the cement. Substituting sodium chloride (NaC1) for CaC12 as the admixture produced only minor differences in equilibrium concentration. The equilibrium Cl-ion/OH- ion ratios for treatments of 0.5% CaC12 and above were found to be beyond that considered to be the boundary for depassivation, slightly above 0.3. X-ray diffraction results were ambiguous but differential thermal a n a l y s i s (DTA) t r i a l s provided some evidence for the formation of Friedel's salt in these pastes. However, it was considered likely that at least some

155

of t h e c h l o r i d e no t re ta ined i n s o l u t i o n i s a s s o c i a t e d w i t h ca l c ium-s i l i ca t e -hydra t e (C-S-H) gel .

1368. Frohnsdorf f , G. , "BLENDED CEMENTS, '' ASTM, STP-897, a., 1986, pp. 172 .

P o r t l a n d b las t furnace s l a g cements, p o r t l a n d f l y a s h cements, and blended cementa wi th s l a g s and pozzolans are t h e t h r e e basic t o p i c s addressed i n t6.e n i n e t e c h n i c a l pape r s comprising t h i s p u b l i c a t i o n .

1369. Harr ison, W. H., "DURABILITY TESTS ON B U I L D I N G MORTZ3.S - EFFECT OF SAND GRADING," Magazine of Concrete Research, V o l . 38, N o . 135, 1986, pp. 95-107.

R e s u l t s are r e p o r t e d on a laboratory i n v e s t i g a t i o n i n t o t h e p r o p e r t i e s and performance of mor ta r under s imula t ed severe exposure. S i x d i f f e r e n t sands va ry ing from ve ry coarse t o ve ry f i n e w e r e used i n OPC morta.rs p l a s t i c i z e d e i t h e r w i t h l i m e o r an a i r - e n t r a i n i n g agent . T e s t specimens w e r e produced by l a y i n g mortar between e i t h e r w e t o r dry b r i c k s and t h e n removing t h e mortar bed a f t e r 24 hours . The p r o p e r t i e s of t h e f r e s h and t h e hardened mortar were measured.

1370. Joyce, R., "PFA RECOMMENDED AS ''FOURTH I N G R E D I E N T ' FCR H I G H PERFORMANCE CONCRETE, Highways (Croydon E n g l ) , Vol. 5 4 , NO. 1909, 1986, pp. 8-9.

The l a s t a r t i c l e i n ou r series on cement replacements looks a t p u l v e r i s e d f u e l a sh (PFA), a by- product of coa l b u r n t , a t e lectr ical power s t a t i o n s . The benefi ts of PFA inc lude : improved resistance t o a l k a l i aggregate r e a c t i o n ; improved s u l p h a t e resistance; lower h e a t of hydra t ion ; h i g h e r long-term s t r e n g t h ; improved workab i l i t y ; reduced w a t e r c o n t e r t ; reduced pe rmeab i l i t y ; reduced b:-eeding.

1371. Kordina, K. 0. and Ehm, C. e t al-., "EFFECTS O F BIAXIAL LOADING ON THE H I G H TEMPERATURE BEHAVIOUR OF CONCRETE, 'I F i r e S a f e t y Science, Proceedings o f t h e F i r s t I n t e r n a t i o n a l Symposium, 3.986, pp. 281-290.

B i a x i a l compression tests w i t h o r d i n a r y concrete have been carried o u t under s t e a d y s t a t e and t r a n s i e n t t empera tu re c o n d i t i o n s . The test: r e s u l t s show t h a t even s m a l l l o a d levels i n a second a x i s a l t e r t h e mechanical p r o p e r t i e s of concre te s i g n i f i c a n t l y . The s t r e s s - s t r a in r e l a t i o n s h i p s show a s i g n i f i c a n t dependence on t h e tempera ture level and t h e stress

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ratio. The strength under biaxial compressive stress is higher than the strength under uniaxial compression. The volumetric strains increase with increasing stress ratios and increasing temperatures. The failure temperature of specimens being biaxially loaded is higher than that of specimens which are uniaxially loaded. The modes of failure indicate that the tensile deformation is vital for the failure mechanism of concrete.

1372. LaFraugh, R. and Zinserling, M., "CONCRETE OVERLAYS FOR BRIDGES.," Interim Report, Washington State Department of Transportation, May 1986, pp. 43.

An extensive state-of-the-art review of construction methods and results for latex modified concrete (LMC) and low slump, dense concrete (LSDC) overlays is presented in this report. Recommendations are made for improvements in construction procedures, inspection, and specifications. An analysis and preventative measures for plastic shrinkage cracks in LMC are presented. Other alternate bridge deck protective systems were examined.

1373. Lydon, F. and Balendran, R., "SOME OBSERVATIONS ON ELASTIC PROPERTIES OF PLAIN CONCRETE," Cement and Concrete Research, Vol. 16, No. 3, May 1986, pp. 314- 324.

The elastic properties of plain concrete are important for understanding its behavior. They are mainly affected by type of aggregate, concrete strength, age and curing history. Sustained loading also seems to be important. Experimental data are presented to illustrate these effects. Evidence is consolidated to confirm that the modulus of elasticity and Poisson's ratio in tension are equal to those in compression.

1374. Malhotra, V. M. (Ed. ) , Fly Ash, Silica Fume, Slag, and Natiural Pozzolans In Concrete, Proceedings - Second International Conference, ACI SP-91, 1986, pp. 1609.

This conference proceedings contains 78 papers in 2 volumes. The topics covered include: fly ash and natural pozzolan applications; condensed silica fume and slag mixing; effect of fly ash in concrete; fly ash cementitions properties; mixed concrete creep behavior; fly ash concrete hydrothermal exposure; superplasticized concrete thermal properties;

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pozzo lan ic cement c o n c r e t e accelerated s t r e n g t h tests; calcium-enriched f l y ash c o n c r e t e mix p ropor t ions ; blended cement c o n c r e t e s t r u c t u r a l d u r a b i l i t y ; f l y ash c o n c r e t e carbonat ion; c o n c r e t e s u r f a c e l a y e r s t r e n g t h ; f l y ash effect on conc re tge reinforcement corrosicm; f l y ash w a t e r r educ ing p r o p e r t y i n mortar; o i l . shale ash p r o p e r t i e s ; condensed s i l i c a fume c o n c r e t e performance; c o n c r e t e ca rbona t ion depth w i t . h condensed s i l i c a fume; s i l i ca fume c o n c r e t e polymer impregnation; steel fiber c o n c r e t e w i t h s i l i c a fume f l e x u r a l behavior ; s i l i c a fume i n p o r t l a n d cement g r o u t s ; t empera tu re cyc led s l ag conc re t e s ; b las t fu rnace slag c o n c r e t e compressive s t r e n g t h ; c h l o r i d e i o n d i f f u s i o n i n f l y a s h c o n t a i n i n g mortars ; ash c o n t a i n i n g c o n c r e t e d u r a b i l i t y ; p o r t l a n d cement- b las t fu rnace s lag s u l p h a t e r e s i s t a n c e ; i r o n blast fu rnace s l ag spec i f i ca t . i ons ; s i l i ca fume s p e c i f i c a t i o n s .

1375. Malvern, L. E . and Tang, T . e t al., '"DYNAMIC COMPRESSIVE STRENGTH OF CEMENTITIOUS MATERIALS," Materials Research Soc ie ty Symposia Proceedings , Vol. 64, 1986, PP. 119-138.

T h e o b j e c t i v e of t h i s researc:h is t o de te rmine t h e ra te dependence o f f / / c and e v e n t u a l l y t o model t h e ra te-dependent c o n s t i t u t i v e behavior . R e s u l t s of tes ts w i t h a small Kolsky bar sys t em and o f a newly b u i l t larger s y s t e m on c o n c r e t e w i t h a maximum aggregate s i z e 1 /2 i n c h are r e p o r t e d w i t h s t r a i n rates a t t h e maximum stress from 50 t o 800/sec f o r mor ta r and from 5 t o 120 / sec f o r conc re t e . An apparent ra te dependence up t o a lmost t w i c e t h e s t a t i c s t r e n g t h i s observed f o r bo th . The mor ta r shows an apparent l i n e a r dependence, wh i l e the h igh - s t r eng th c o n c r e t e shows an approximately l o g a r i t h m i c dependence on t h e s t r a i n ra te a t the maximum stress, over: the dynamic range observed. Some q u e s t i o n s about specimen s i z e effects and about how much o f t h e apparent s t r a i n - r a t e e f f ec t i s r e a l l y a l a t e ra l i n e r t i a confinement effect are a s y e t unreso lved .

1376. McCurrich, L . , "PERMEABILITY TESTING O F S I T E CONCRETE - THE POSSIBILITIES AND RELEVANCE, Concrete(London) , Vol. 2 0 , No. 3.1 , Nov 1986, pp. 23- 2 4 .

The i n c r e a s i n g a t t e n t i o n be ing g iven t o a l l aspects of r e i n f o r c e d c o n c r e t e d u r a b i l i t y has high- l i g h t e d t h e importance of t h e a b i l i t y of c o n c r e t e , and i n p a r t i c u l a r t h e reinforcement cover zone, t o resist

158

the ingress of deleterious agents from the surrounding environment. To determine the permeability achieved on site, the concrete can either be tested in situ, or can be tested with samples removed from site. The most well-known in situ test is the initial surface absorption test, commonly known as ISAT, and some years ago this became incorporated as a standard method in BS 1881. The test measures the rate at which water applied to the surface of concrete in a special cap is absorbed into the surface under a low head.

1377. Muguruma, H. and Watanabe, F., "LOW-CYCLE FATIGUE BEHAVIOR OF CONCRETE AND AE MONITORING UNDER SUBMERGED CONDICTION," Proceedings of the Twenty-Ninth Japan Congress on Materials Research; Tokyo, Japan, Conf, N0.09271, 1986, pp. 151-158.

In this study, to verify the reason why the fatigue life of concrete becomes short under submerged condition, low-cycle compressive fatigue tests were carried out on the plain concrete under different environments. Test results obtained were discussed on the effects of mix proportions and the environments upon the fatigue life from the statistical view point. For specimens in additional test series, acoustic emission signals (AE) caused by the local fracture in concrete were monitored in conjunction with the strain measurement during cyclic loads. Based on the AE monitoring, fatigue failure processes of concrete under submerged condition were discussed by using the source location technique.

1378. Muravljov, M. and Zivkovic, S. et al., "POSSIBLE PRODUCTION OF CONCRETE WITH EARLY-AGE HIGH-STRENGTH BY SIMULTANEOUS USE OF ACCELERATORS AND SUPERPLASTICIZERS AS ADMIXTURES.," Proceedings - Symposium on Research on the Use of Modern Achievements in Yugoslav Civil Engineering in the Field of Materials and Structures., Vols. 1, 2, 3 and 4, Oct 1986, pp. 161-168.

The paper discusses the possibility of producing concrete with early-age high-compressive strength by influencing the process of hydration on a chemical and physical basis. In the first case, the necessary effects are achieved by using accelerators as admixtures in the hardening process. In the second case, the necessary rate of hardening is obtained by using low water cement ratios and superplasticizers. After 16 hours, a compressive strength of 10 m p a is obtained while after 24 hours it reaches the level of 16 mpa. Concrete mixes are highly workable which is

159

impor tan t f o r i t s use i n monol i th ic and p r e c a s t reinforced s t r u c t u r e s .

1379. Murayama, Y. and Iwabuchi, A . , "FLEXUARL AND SHEAR STRENGTH OF REINFORCED HIGH-STRENGTE LIGHTWEIGHTCONCRETE BEAMS, 'I Transac t ions of t h e Japan Concrete I n s t i t u t e . ( Proceedinlgs of t h e Annual J C I Meet ing) , Tokyo, Japan, Vo1.8, 1986, pp 267-274.

F l e x u r a l and shear s t r e n g t h s of r e i n f o r c e d high- s t r e n g t h l i g h t w e i g h t conc re t e (.LWC) beams are d i s c u s s e d i n comparison w i t h th,:,se o f r e i n f o r c e d normal weight c o n c r e t e (NWC) be,ams. I t has been concluded from tes t r e s u l t s t h a t t h e f l e x u r a l s t r e n g t h s of t h e r e i n f o r c e d LWC beams are compatible w i t h t h o s e o f t h e r e i n f o r c e d NWC beams d e s p i t e t h e d i f f e r e n c e i n t h e s t ress-s t ra in cu rves o f t h e two conc re t e s ; t h a t t he i n t e r f a c e shear t r a n s f e r s t r e n g t h s of the LWC's are 70% of t h o s e o f the NWC's , and t h a t t h e i n c l i n e d c rack ing s t r e n g t h s o f t h e r e i n f o r c e d LWC: beams are 70% of t h o s e of t he r e in fc , r ced NWC beams. However, t h e s h e a r s t r e n g t h s i n s h e a r compression f a i l u r e o f t h e r e i n f o r c e d LWC beams seem h i g h e r t h a n t h o s e of t h e r e i n f o r c e d NWC beains.

1380. Nakamura, N. and Saka i , M. e t a.L., "PROPERTIES O F HIGH-STRENGTH CONCRETE INCORPORATING VERY FINELY GROUND GRANULATED BLAST FURNACE SLAG, 'I F l y A s h , S i l i c a Fume, Slag, and Na tu ra l Pozzolans i n Concrete, A C I SP- 91, Vol. 2, 1986, pp. 1361-1380.

T h i s paper describes how some p r o p e r t i e s of high compress ive-s t rength conc re t e (approximately 80 MPa) can be improved by t h e use of ve ry f i n e ground g r a n u l a t e d b l a s t - f u r n a c e s l ag a:; a p a r t i a l rep1acemen:t f o r p o r t l a n d cement. The f i n e n e s s of ve ry f i n e ground s lag i s 715 m**2/kg (Bla ine) made from c l a s s i f y i n g o r d i n a r y ground s lag (364 m**2/kg B la ine ) by t h e air: s e p a r a t o r . Concrete mixtures c o n t a i n i n g ve ry f i n e ground s lag w e r e tested va ry ing t h e s u b s t i t u t i o n r a t i o of s lag t o t o t a l con ten t of cemen t i t i ous m a t e r i a l s (s lag PLUS p o r t l a n d cement) 1 0 , 4 0 , and 70 p e r c e n t . I t

w a s found t h a t high compressive s t r e n g t h could be ob ta ined w i t h t he improvement of p e r m e a b i l i t y , r e s i s t a n c e t o c h l o r i d e p e n e t r a t i o n , and o t h e r p r o p e r t i e s , even i f very f i n e g:round s lag w a s s u b s t i t u t e d f o r cement a t a replacement level of 7 0 % .

1381. Nasser, K. W. and Al-Manaseer, A. A., "CREEP OF CONCRETE CONTAINING FLY ASH AND SUPERPLASTICIZER AT DIFFERENT STRESS/STRENGTH RATIOS," Journal of the American Concrete Institute, Vol. 83, No. 4, Jul-Aug 1986, pp. 668-673.

Investigates the influence of different stress/strength ratios on the creep of unsealed and sealed concrete containing Saskatchewan lignite fly ash and admixtures of water reducer, air entrainment, and superplasticizer. The results were compared with a similar mix that did not contain any admixtures except air entrainment. The creep strain was measured at different stress/strength ratios of 10, 20, 30, 40, 50, and 60 percent, for a maximum period of 112 days. All the tests were carried out at room temperature of 70 F (21. 1 C). Creep was found to vary linearly with logarithm of time for both sealed and unsealed concrete. Also, creep was found to be a linear function of stress/strength ratio.

1382. Numata, S. and Koide, Y. et al., "PROPERTIES OF ULTRA- HIGHLY PULVERIZED GRANULATED BLAST FURNACE SLAG- PORTLAND CEMENT BLENDS," Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, ACI SP-91, Vol. 2, 1986, pp. 1341-1360.

This paper describes a study of the full exploitation of the inherent hydraulic behavior of granulated blast-furnace slag. An attempt was made by laboratory tests and by actual concrete practices to improve the properties of conventional slag cements and develop a high quality binder. Granulated blast- furnace slag pulverized and classified by an industrial mill (Blaine fineness 850 m**2/kg) was mixed with ordinary portland cement and semi-crushed granulated blast-furnace slag sand aggregate with the addition of a high-range water-reducing admixture. Workability, strength, and resistance to freezing and thawing cycles, mechanical abrasion and chemical attacks were determined. Microstructures were measured by SEM, and mercury intrusion and nitrogen adsorption porosimetries.

1383. Oh, B., "FATIGUE ANALYSIS OF PLAIN CONCRETE IN FLEXURE," Journal of Structural Engineering, Vol. 112, No. 2, Feb 1986, pp. 273-288.

This paper investigates fatigue strength of plain concrete subjected to flexural loading. This type of fatigue loading is of concern in the design of

161

c o n c r e t e bridges and conc re t e pa.vement slabs, s i n c e t h e f l e x u r a l stresses i n t.hese s t r u c t u r e s can be c r i t i ca l . Both exper imenta l and t h e o r e t i c a l s t u d i e s are conducted. T h e S-N curves a.re gene ra t ed from t h e t es t r e s u l t s and an equa t ion i s ob ta ined by r e g r e s s i o n a n a l y s i s t o p r e d i c t t h e f l e x u r a l f a t i g u e s t r e n g t h of conc re t e . A p r o b a b i l i s t i c approach .is i n t roduced t o p r e d i c t t h e f a t i g u e r e l i a b i l i t y of c o n c r e t e . The d i s t r i b u t i o n of f a t i g u e l i f e of c o n c r e t e under a given stress level w a s found, from t h e t es t data, t o approximately fo l low t h e Weibull. p r o b a b i l i t y l a w . The method o f o b t a i n i n g t h e d i s t r i b u t i o n parameters from S-N r e l a t i o n f o r t h e f l e x u r a l f a t i g u e o f c o n c r e t e i s a l s o p re sen ted .

1384. Ozyi ld i r im, C. , " INVESTIGATION OF CONCRETE CONTAINING SLAG -- HAMPTON RIVER BRIDGE., V i r g i n i a Highway & T r a n s p o r t a t i o n Research Counci l , F i n a l Report , May 1986, pp. 13.

The s tudy e v a l u a t e d t h e p r o p e r t i e s of c o n c r e t e s c o n t a i n i n g s lag i n a 50% replacement of the p o r t l a n d cement t o assess t h e i r s u i t a b i l i t y as an a l t e r n a t i v e t o t h e p o r t l a n d cement c o n c r e t e s normally used i n the c o n s t r u c t i o n o f bridge substruct:ures. For the major p o r t i o n of t h e s tudy , samples w e r e o b t a i n e d from f r e s h l y mixed c o n c r e t e used i n the c o n s t r u c t i o n o f t he s u b s t r u c t u r e f o r t h e Route 143 hridge over the Hampton R i v e r and a l s o from a fa i led p i e r f o o t i n g f o r the bridge. I n t h e l a b o r a t o r y , a l i m i t e d i n v e s t i g a t i o n w a s made o f t h e effects of tempera ture on c o n c r e t e s w i t h and wi thout s lag. The r e s u l t s i n d i c a t e t h a t concretes conta in ing q u a l i t y s l ag w i l l perform s a t i s f a c t o r i l y i n bridge s u b s t r u c t u r e s . However, it h a s been shown t h a t s t r e n g t h development i n c o n c r e t e s c o n t a i n i n g s lag i s more adve r se ly i n f l u e n c e d by c o l d weather t h a n i s t h a t o f c o n c r e t e s wi thout s lag. Alsc, it is no ted t h a t i n c o l d weather there may be a s i g n i f i c a n t d e l a y i n t h e t i m e of se t .

1385. Park, S. and T i a , M. , "THE EFFECTS OF SUPERPLASTICIZERS ON THE ENGINEERING PROPERTIES OF P L A I N CONCRETE," T ranspor t a t ion Research Record, N1062, 1986, pp. 38-46.

T h e effects of s u p e r p l a s t i c i z e r s on fresh and hardened c o n c r e t e were i n v e s t i g a t e d . The exper imenta l program inc luded tests on the s:Lump and slump l o s s , b l eed ing , s e t t i n g t i m e , a i r c o n t e n t , compacting f a c t o r , V e e Bee , compressive s t r e n g t h , t e n s i l e and f l e x u r a l s t r e n g t h , permeabi l i ty , , sh r inkage , and freeze- thaw d u r a b i l i t y . P r o p e r t i e s of s u p e r p l a s t i c i z e d

162

concrete were compared with those of conventional (high-slump) and base (low-slump) concretes. Superplasticizers were observed to have an appreciable fluidifying action in fresh concrete. They permitted a significant water reduction while maintaining the same workability. Bleeding of superplasticized concrete was much lower than that of conventional concrete of the same consistency. The compacting factor and Vee Bee value of superplasticized concrete were not significantly different from those of conventional concrete of the same consistency. This indicates that the use of superplasticizers did not affect the tendency of segregation of fresh concrete. The compressive, tensile, and flexural strengths of superplasticized concrete were significantly higher than those of conventional concrete. The permeability and drying shrinkage of superplasticized concrete were significantly less than those of conventional concrete, but there were no significant differences between base and superplasticized concrete. Compared with base concrete, non-air-entrained superplasticized concrete had slightly higher freeze-thaw durability, and superplasticized concrete with an appropriate amount of entrained air gave even better resistance to freezing and thawing. This paper appeared in Transportation Research Record N1062, Roller-Compacted Concrete Pavements and Concrete Construction.

1386. Penttala, V., "COMPATIBILITY OF BINDER AND SUPERPLASTICIZER IN HIGH-STRENGTH CONCRETE," Nordic Concrete Research, Dec 1986, pp. 117-128.

With the results from the electrophoresis tests and the penetration tests done by the Vicat-apparatus best compatible binder and superplasticizer combinations were selected. The results were applied to high- strength concrete produced by silica fume, class F flay ash, blast-furnace slag and ordinary cements together with compatible superplasticizers. By nearly triplicating the compression strength of the concrete the material costs rise merely 20-25 percent.

1387. Perdikaris, P. C. and Calomino, A. M., "CRACK GROWTH IN CONCRETE UNDER FATIGUE," Proceedings of the 1986 SEM Spring Conference on Experimental Mechanics; New Orleans, LA, 1986, pp. 1-6.

Fracture toughness characteristics of plain concrete under fatigue were studied based on 4-point bending tests of single-edge-notched beam (SENB) specimens. Crack growth was monitored by the crack- mouth-opening displacement CMOD compliance. Surface

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crack obse rva t ions and f l u o r e s c e n t dye-penet ra t ion i n t o t h e notch r o o t were performed t o de te rmine the shape o f t h e c rack f r o n t . The c rack l e n g t h s based or! t h e CMOD compliance measurements and LEFM agree w e l l w i t h t h e dye-penet ra t ion r e s u l t s . F r a c t u r e toughness , G / / I / / c , i n t h e f a t i g u e tests (cracked beams) i s higher t h a n i n t h e s t a t i c t e s t s (notched beams) i n d i c a t i n g a presence of a microcracking ( p r o c e s s ) zone. F i n a l l y , some p re l imina ry r e s u l t s on t h e k i n e t i c s of crack growth a r e p r t =sen ted .

1388. Perdikar is , P . and Calomino, A. e t a l . , "EFFECT OF FATIGUE ON FRACTURE TOUGHNESS O F CONCRETE, J o u r n a l o f Engineer ing Mechanics, V o l . 1 1 2 , No. 8, Aug 1986, pp. 776-791.

An exper imenta l s tudy u t i l i z i n g 4-point bending SENB specimens w a s carried ou t t o de te rmine t h e effect of f a t i g u e on t h e f rac ture toug:hness of p l a i n c o n c r e t e . I n a d d i t i o n t o f o u r t e e n s t a t i c tests of beams w i t h a midspan p r e c a s t notch, n i n e specimens w i t h an i n i t i a l p r e c a s t no tch o f a dep th t o h e i g h t r a t i o o f l / d = 0 . 2 0 were f a t i g u e d u n t i l a c e r t a i n crack l e n g t h w a s reached. Crack growth w a s s u c c e s s f u l l y monitored by the CMOD compliance measurements. Independent s u r f a c e c rack l e n g t h measurements by a hand-held scope and obse rva t ions o f t h e crack f r o n t w i t h t h e use of a f l u o r e s c e n t dye-penetrant i n j e c t e d i n t o t he notch r o o t were a l s o performed. toughness , G i c , under f a t i g u e appears t o be higher t h a n under s t a t i c load ing and shows an i n c r e a s i n g t r e n d w i t h i n c r e a s i n g c rack l e n g t h and number of l o a d i n g c y c l e s . re la ted t o t h e presence of a microcracking zone t h a t evo lves wi th f a t i g u e .

The f r a c t u r e

T h e observed behavior i s most like.l!y

1389. P h i l l e o , R., "FREEZING AND THAWING RESISTANCE O F HIGH- STRENGTH CONCRETE," NCHRP Syn thes i s of Highway Practice, N129, D e c 1986, PP. 38.

Recent developments have made a new g e n e r a t i o n o f h i g h - s t r e n g t h c o n c r e t e a v i a b l e material f o r r o u t i n e c o n s t r u c t i o n . high-range water-reducing admixtures , which permit the placement of c o n c r e t e of ve ry low water-cement r a t i o , and s i l i c a fume, a pozzolan of ex t remely h i g h f i n e n e s s . T h e advent o f t h i s h igh - s t r eng th c o n c r e t e h a s p u t requi rements f o r s t r e n g t h arid d u r a b i l i t y i n c o n f l i c t . Because e n t r a i n e d a i r reduces t h e s t r e n g t h of conc re t e , b u i l d e r s seek t o e l i m i n a t e o r l i m i t t h e use o f e n t r a i n e d a i r . There are t h o s e who a rgue that, h igh - s t r eng th c o n c r e t e i s of s u c h a q u a l i t y t h a t

The two p r i n c i p a l developments a r e

1 6 4

entrained air is unnecessary. Much of the high- strength concrete currently being used is in buildings, where the question of durability is minor. The question, however, cannot be avoided in exposed highway structures. Service records of non-air- entrained high-strength concrete exposed to freezing are not conclusive. Hence, this report synthesizes the available knowledge on the subject. Its aim is to provide guidance to those who wish to use high- strength concrete in typical highway applications and to indicate where further information is needed.

1390. Pigeon, M. and Pleau, R. et al., "FREEZE-THAW DURABILITY OF CONCRETE WITH AND WITHOUT SILICA FUME IN ASTM C 666 (PROCEDURE A) TEST METHOD: INTERNAL CRACKING VERSUS SCALING," ASTM Cement, Concrete, and Aggregates, Vol. 8, No. 2, 1986, pp. 76-85.

The freeze-thaw durability of concrete with and without silica fume was investigated in accordance with the requirements of ASTM Test Method for Resistance of Concrete to Rapid Freezing and Thawing (C 666 Procedure A). The water-cement ratio of all mixes was 0.5, and the silica-cement ratio of the silica fume mixes 0.1. The test results show that the critical value of the air-void spacing factor in these ASTM C 666 tests is significantly lower for the silica fume concretes. These concretes are therefore more susceptible to internal cracking caused by rapid freeze-thaw cycles in water, even though the use of silica fume decreased the surface scaling of the test specimens. This confirms that scaling and internal cracking are two different forms of frost damage caused by rapid freeze-thaw cycles in water. The use of silica fume also decreased the internal cracking of the nonair-entrained mixes damaged during the tests.

1391. Reinhardt, H. W. and Kormeling, H. A. et al., "SPLIT HOPKINSON BAR, A VERSATILE TOOL FOR THE IMPACT TESTING OF CONCRETE," Mater Struct, Vol. 19, No. 109, 1986, pp. 55-63.

Material properties under impact loading were studied by means of the split Hopkinson bar method. The paper describes the basic features of the equipment and gives the technical specifications of the materials and components used. The equipment, which had been designed for uniaxial tensile loading, was adapted for pull-out bond testing, for cryogenic testing, and for biaxial compression/tension testing. The various requirements and adjustments are dealt with and the principal results illustrating the

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v a r i o u s a p p l i c a t i o n s are r e p o r t e d . I t i s exp la ined t h a t t e s t i n g equipment su i t ed f o r s t r a i n rates between 0 . 0 5 and 25/sec. has been developed a t f a i r l y l o w c o s t .

1392. Reinhard t , H. W . , "INTERPRETATION OF THE POST-PEAK CYCLIC BEHAVIOR OF CONCRETE I N TENSION," Darmstadt Concrete: Annual Jou rna l on Concrete and Concrete S t r u c t u r e s , Vol. 1, 1986, pp. 157-165.

T e n s i l e s t r e n g t h and deformation of p l a i n c o n c r e t e have been s t u d i e d under u n i a x i a l cyclic load ing . The stress displacement diagrams are ana lyzed w i t h r e s p e c t t o reversible and irreversible d isp lacement , energy d i s s i p a t i o n , and s t i f f n e s s deg rzda t ion d u r i n g c y c l i n g . Descriptive models are p r e s e n t e d c o n s i s t i n g of f r i c t i o n a l e lements and normal and f l e x u r a l s p r i n g s . T h e e lements of the models are c:ompared w i t h r ea l c o n s t i t u e n t s of conc re t e . I t i s demonstrated t h a t t h e large d isp lacements observed are only e x p l i c a b l e i n t r o d u c i n g p a r a l l e l c r acks and bending s t i f f n e s s o r remnant uncracked areas i n t he c r a c k i n g zone. Some remarks are made w i t h r e s p e c t t o t e s t i n g of f r a c t u r e mechanics parameters .

1393. Reinhold, R. E . and Buck, A. D . e t a l . , "VARIATIONS I N CEMENTITIOUS MEDIA," Tech Rep U S Army Eng W a t e r w Exp S t n SL-86-10, May 1986, pp. 270..

A t o t a l of 5 9 cements, 1 2 fly ashes , 1 9 s i l i c a fumes from 1 6 sources , 3 natural- pozzolans, and 1 ground g r a n u l a t e d i r o n b l a s t - f u r n a c e s l a g , and l a b o r a t o r y combinations of t h e s e materials w e r e s t u d i e d by a combination of p h y s i c a l , chemical, and p e t r o g r a p h i c methods. Creep d a t a were o b t a i n e d f o r 1 7 pastes made u s i n g some of these materials.

1394. R o l l i n g s , R. S., "FIELD PERFORMANCE O F FIBER- REINFORCED CONCRETE AIRFIELD PAVEMENTS," Geotechnica l Laboratory, Waterways Experiment: S t a t i o n , Vicksburg, MS; Federal Avia t ion Adminis t ra t ion , Washington D . C . , J u l 1986, pp. 5 0 .

A f i e l d survey of steel f i b e r - r e i n f o r c e d c o n c r e t e a i r f i e l d pavements found t h e most s e r i o u s performance problem t o be permanent, e a r l y age c u r l of slabs and a s s o c i a t e d c rack ing . An examination of p o s s i b l e causes of t h i s c u r l i n d i c a t e s it : i s probably due t o the u s e o f large s labs and t h i n s e c t i o n s . T h i s s tudy recommends s lab s i z e s which should minimize t h i s problem i n t h e f u t u r e . Other i d e n t i f i e d performance

1 6 6

problems unique to this type pavement include loose surface fibers and nonfunctioning contraction joints. The design criteria for fiber-reinforced concrete was reviewed, and new criteria was proposed that is compatible with the Corps of Engineers change in portland cement concrete design criteria. A new method of overlay design was also proposed.

1395. Roper, H. and Kirkby, G. et al., "LONG-TERM DURABILITY OF BLENDED CEMENT CONCRETES IN STRUCTURES," Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, ACI SP-91, VOl. 1, 1986, pp. 463-482.

Relatively little information has been published on the long-term durability of blended cement concretes in service. The paper is a summary of an investigation of over two hundred structures in Australia. Some of these have service lives in excess of twenty years. Cored materials from some of the structures are described, and petrological and mineralogical examination allow conclusions on the efficacy hydration processes under field curing to be made. Porosity and permeability is discussed. Carbonation and corrosion effects on long-term durability are considered by the examination of data obtained from in situ concretes.

1396. Saito, M. and Kawamura, M., "RESISTANCE OF THE CEMENT- AGGREGATE INTERFACIAL ZONE TO THE PROPAGATION OF CRACKS," Cement and Concrete Research, Vol. 16, No. 5, Sept 1986, pp. 653-661.

A simple concrete model was used for evaluating the resistance of the cement-aggregate interfacial zone to the propagation of cracks. The characteristics of the interfacial zone for various types of rocks were estimated from the microhardness measurements conducted for each cement-rock combination. The load at which a crack formed first at a point on the interface reaches the prescribed point was regarded as a measure showing the extent of resistance of the interfacial zone to the propagation of cracks. Any interactions between cement paste and rock seem not to favorably contribute to the resistance of the interfacial zone to the propagation of cracks.

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1397. S e i t z e r , R. and S e t z e r , S. W . , '"'SPEED L I M I T FOR CONCRETE TESTED, Engineer ing News-Record, VOl. 217 , No. 6, Aug 7 1986, pp. 43.

A new t y p e of f a s t - s e t t i n g c o n c r e t e i s g e t t i n g i t s first road test on a 7 - m i l e s tretch of highway i n Iowa. The so -ca l l ed ' f a s t - t r a c k ' pavement, while s l i g h t l y more expensive t h a n a convent iona l mix, ho lds t h e promise of competing w i t h a s p h a l t o v e r l a y s f o r the growing highway r e c o n s t r u c t i o n .market, where t h e emphasis i s on quick r e s t o r a t i o n w i t h mimimum d i s l o c a t i o n of t r a f f i c . The f a s t - s e t . t i n g mix i s t h e b r a i n c h i l d of a committee c o n s i s t i n g of Iowa c o n t r a c t o r s , t rade a s s o c i a t i o n s , c0ncret .e producers and equipment manufacturers , i n cooperat.ion w i t h t h e Iowa Dept. of T ranspor t a t ion . While several v a r i a t i o n s o f t h e new mix are under development, t h e material g e n e r a l l y c o n s i s t s of f i n e l y g ranu la t ed , high-ear ly- s t r e n g t h p o r t l a n d cement ( t y p e 111), f l y ash, a water- reducing agent con ta in ing calcium c h l o r i d e , and c u r i n g a c c e l e r a t o r s . The mix c u r e s i n 1 2 hours t o a compressive s t r e n g t h of 1,300 p s i arid i s ready f o r t r a f f i c i n 18 hours .

1398. Si lva, M. A. G . and Kra jc inovic , D . r "IMPACT STRENGTH O F CONCRETE," Shock and V i b r a t i o n Digest, Vol. 18, N o . 11, 1986, pp. 3-6.

This review focuses on some of t h e un reso lved and controversial aspects of the impact strength and dynamic f a t i g u e of conc re t e . Th.e a u t h o r s sugges t t h a t continuum damage mechanics is t h e most a p p r o p r i a t e framework f o r t h e development c f a r a t i o n a l t h e o r y for p r e d i c t i n g the impact s t r e n g t h of c o n c r e t e . Unfor tuna te ly , p e r u s a l of t he pub l i shed l i t e r a t u r e i n d i c a t e s t h a t such a model has n o t y e t been developed.

1399. Skoberne, T . , "INFLUENCE O F CONDENSED S I L I C A FUME ON SOME MECHANICAL CHARACTERISTICS AND D U R A B I L I T Y O F FRESH CONCRETE," Symposium on Research on the U s e of Modern Achievements i n Yugoslav C i v : i l Engineer ing i n t h e F i e l d o f Materials and S t r u c t u r e s , O c t 1986, pp. 225-232.

The paper p r e s e n t s t h e e f fec ts o f a condensed s i l i c a fume on some mechanical p r o p e r t i e s and d u r a b i l i t y of c o n c r e t e w i t h the add. i t ion of p l a s t i c i z e r s and s u p e r p l a s t i c i z e r s . A new way o f adding t o t h e c o n c r e t e t h e condensed s i l i c a fume i n t h e form o f s p e c i a l s l u r r y w a s s u c c e s s f u l l y t e s t e d .

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1 4 0 0 . Soroushian, P . and Choi, K.-B. e t a l . , "CEMENT-BASED COMPOSITES: STRAIN RATE EFFECTS ON FRACTURE," Materials Research Soc ie ty Symposia Proceedings, V01.64, 1986, pp. 87-92.

R e s u l t s o f dynamic t e n s i l e s t r e n g t h tests of c o n c r e t e , produced by t h e a u t h o r s and o t h e r i n v e s t i g a t o r s , w e r e used t o s tudy t h e effects of s t r a i n ra te on t h e t e n s i l e s t r e n g t h of conc re t e . The i n f l u e n c e of mois ture con ten t and compressive s t r e n g t h o f conc re t e , and t y p e of tes t ( s p l i t t i n g t e n s i o n , f l e x u r e , o r direct t e n s i o n ) on the s t r a i n rate- s e n s i t i v i t y of t h e t e n s i l e s t r e n g t h were e v a l u a t e d . An e m p i r i c a l l y developed expres s ion i s p r e s e n t e d f o r t h e dynamic- to-s ta t ic r a t i o of c o n c r e t e t e n s i l e s t r e n g t h i n terms of the ra te of s t r a i n i n g .

1 4 0 1 . Soroushian, P . and Choi, K.-B. e t a l . , "DYNAMIC CONSTITUTIVE BEHAVIOR OF CONCRETE," J o u r n a l of The American Concrete I n s t i t u t e , Vol. 83, No. 2 , 1986, pp. 251-259.

A c o n s t i t u t i v e model f o r conf ined and unconfined c o n c r e t e s u b j e c t e d t o dynamic compression i s proposed. T h i s model i s based on numerous measurements of t h e maximum stress and the s t r a i n a t maximum stress i n tests performed a t d i f f e r e n t s t r a i n rates. The proposed model d i s t i n g u i s h e s between the s t r a i n r a t e effects on d ry and w e t conc re t e , and compares w e l l w i t h t h e available t es t r e s u l t s . (Author a b s t r a c t )

1402. Swamy, R. N . , "PROPERTIES OF HIGH-STRENGTH CONCRETE," Cement, Concrete, and Aggregates, v01.8, No.1, Summer 1986, pp. 33-41.

T h i s paper p r e s e n t s data related t o t he development o f h igh - s t r eng th conc re t e w i t h s p e c i a l emphasis on t h e development of h igh-ear ly s t r e n g t h . Both these o b j e c t i v e s were achieved by us ing an u l t r a f i n e p o r t l a n d cement w i t h a s p e c i f i c s u r f a c e about 750 m**2/kg o r a h i g h ea r ly s t r e n g t h p o r t l a n d cement w i t h about 75% t r i c a l c i u m s i l i ca t e c o n t e n t . Experimental data are t h e n r e p o r t e d on s t r e n g t h and e l a s t i c i t y p r o p e r t i e s , s t r e s s - s t r a i n behavior , h e a t of hydra t ion , shr inkage , and c r e e p of these c o n c r e t e s . T h e r e s u l t s show t h a t u s i n g an u l t r a f i n e cement, c o n c r e t e w i t h adequate w o r k a b i l i t y and one-day s t r e n g t h s of 60 t o 8 0 N/mm**2 and 35 t o 4 0 N/mm**2 can be obtained with g r a n i t e aggregates and l i gh twe igh t aggrega tes , r e s p e c t i v e l y .

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1403. Tse, E. W. and Lee, D. Y. et al., "FATIGUE BEHAVIOR OF CONCRETE CONTAINING FLY ASH," Fly Ash, S.ilica Fume, Slag, and Natural Pozzolans in Concrete, ACI SP - 91,

As a pozzolan, fly ash has been used to replace some of the portland cement in concrete. Because of its many advantages, the use of fly ash in concrete will undoubtedly increase. Although many studies have been conducted on the physical properties of concrete containing fly ash, very little research has been reported on the fatigue properties of fly ash concrete. Since most concrete pavement design procedures currently in use are based on the consideration of concrete fatigue, the importance of fatigue properties of concrete pavement containing f l y ash is evident. The purpose of this study was to evaluate the fatigue properties of concretes containing fly ash and compare these properties to those of concrete without fly ash.

Vol. 1, 1986, pp. 273-289.

1404. Van Mier, J. G. M., "FRACTURE OF CONCRETE UNDER COMPLEX STRESS," Heron, Vol. 31, No. 3, 1986, pp. 90.

Results of displacement-controlled multiaxial experiments on concrete are discussed in the first part of this paper. rather wide, ranging from simple proportional load paths to complicated paths that involve changes of principal stresses. Main emphasis is placed on fracture modes, and the experiments suggest that failure of concrete, both in tensile and compressive loading combinations, is a 1oca:Lized phenomenon. During the softening branch the specimens become highly nonuniformly loaded, and interactions with the experimental environment are very pronounced. In the second part, the outline for a physical model for concrete fracture is proposed. In principle, the model also should apply to rock. The model is valid for loading combinations involvhg both tensile and compressive components such that brittle fracture prevails. The model is divided into three stages: microcracking, crack joining, and localization. A simple fracture mechanics so1ut:ion is proposed for explaining the shape of the softening branch in direct tension. These theoretical considerations lead, in combination with the experimental observations, to the conclusion that geometrical changes in the post-peak range from the major ingredients of the softening phenomenon. When assuming nonuniform displacement distributions, typical response of direct tension

The scope of the experiments w a s

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experiments loaded between nonrotatable loading platens can be explained, and this is shown in the last part of the paper by a nonlinear numerical simulation with the DIANA finite element package.

1405. Willam, K. and Hurlbut, B. et al., "EXPERIMENTAL AND CONSTITUTIVE ASPECTS OF CONCRETE FAILURE," Finite Element Analysis of Reinforced Concrete Structures, Seminar Proceedings, Tokyo, Japan, 1986, pp. 226-254.

This paper presents novel experimental observations of post-critical response phenomena when cylindrical concrete specimens are loaded under displacement control in the form of direct tension and triaxial compression experiments. The investigation focuses on the problem whether or not 'proper' material properties can be extracted from such experiments which characterize not only stiffness and strength behavior but also the ductility in the post-peak response regime. In this context a fracture energy based strain-softening plasticity formulation is developed in terms of the fundamental Mode I type cracking which accounts for the transition from brittle to ductile fracture under increasing triaxial confinement .

1406. Zaitsev, Y. V. and Kovler, K. L., "NOTCH SENSITIVITY OF CONCRETE AND SIZE EFFECT. PART 11: STRESS STATE EFFECT," Cement and Concrete Research, Vol. 16, No. 1, 1986, pp. 7-16.

The problem of notch sensitivity of concrete is discussed with the influence of size effect being taken into account. The need to consider the size effect on the tensile strength of concrete was noted. The simple dependence of the critical stress intensity factor K(**IC) on stress state, specimen and crack geometry, tensile strength and structure of material is found. When analyzing the fictitious crack model the fracture zone length is calculated as a function of specimen and crack geometry and structure of the material.

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1987

1407. "RESEARCH NEEDS FOR HIGH-STRENGTH CONCRETE., I' J o u r n a l o f t he American Concrete I n s t i t l J t e , V o l . 84, N o . 6, NOV 1987, pp. 559-561.

A brief summary i s p resen ted of research needs i n many areas t o i n s u r e t h e economical and p rope r a p p l i c a t i o n of high s t r e n g t h c o n c r e t e s . T h e areas covered i n c l u d e t h e fol lowing: a i r en t ra inment requirements; h igh - s t r eng th c o n c r e t e f o r c o r r o s i o n p r o t e c t i o n ; p r o p e r t i e s o f h igh - s t r eng th c o n c r e t e i n a c t u a l a p p l i c a t i o n s ; e f f e c t s of aggre9at.e characteristics; compaction of h igh - s t r eng th conc re t e ; development o f compressive s t r e n g t h s i n excess of 2 0 , 0 0 0 p s i (138 MPa); s t r u c t u r a l p o r p e r t i e s of high- s t r e n g t h conc re t e ; h igh - s t r eng th c o n c r e t e i n h i g h seismic zones; p r o p e r t i e s of l igh tweight h igh - s t r eng th conc re t e ; long-term d e f l e c t i o n s of beams and slabs; t e s t i n g requirements; use of h igh - s t r eng th conc re t e ; e f f i c i e n t mixing of h igh - s t r eng th conc re t e ; a b r a s i o n r e s i s t a n c e ; f i r e and h igh tempera ture effects; p r o p o r t i o n i n g and e v a l u a t i n g h i g h - s t r e n g t h c o n c r e t e .

1408. "FREEZE-AND-THAW DURABILITY O F FLY ASH CONCRETE.," Missour i Highway and Transpor ta , t ion Department, F i n a l Report , O c t 1987, pp. 2 3 .

T h e p r imary o b j e c t i v e of t h i . s s tudy w a s t o investigate s t r e n g t h , freeze-and-thaw d u r a b i l i t y , and a i r - v o i d system c h a r a c t e r i s t i c s o f c o n c r e t e u t i l i z i n g f l y ash t o r e p l a c e v a r i o u s amounts of cement i n t h e mix des ign . All mixes were desi.gned w i t h 6 . 1 sacks of cement per c u b i c yard, 45% of aggregate as sand, and 5.5% a i r . Limestone aggrega te from two sources w a s used w i t h Class C f l y a sh from f o u r s o u r c e s . Cement w a s r e p l a c e d w i t h f l y a sh on a pound f o r pound b a s i s a t pe rcen tages of 0 , 1 0 , 20 , arid 30. D u r a b i l i t y of c o n c r e t e g e n e r a l l y decreased s l i g h t l y a s pe rcen tage of f l y a sh inc reased . S t r e n g t h g a i n was g e n e r a l l y slc,wer f o r c o n c r e t e w i t h f l y a sh t h a n f o r c o n t r o l c o n c r e t e . Air-void system c h a r a c t e r i s t i c s were comparable f o r a l l c o n c r e t e s . F l y ash i s p r e s e n t l y a l lowed a s a replacement, on a pound f o r pound basis, f o r up t o 15% of cement except i n conc re t e r e q u i r i n g h igh e a r l y s t r e n g t h s . R e s u l t s of t h i s s tudy i n d i c a t e t h a t replacement o f more than 15% cement w i t h f l y ash wcluld r e q u i r e more e x t e n s i v e t e s t i n g of each source o f f l y ash , cement, and aggrega te and cannot be j u s t i f i e d . No major r e v i s i o n of p r e s e n t requi rements i s a n t i c i p a t e d a t t h i s t i m e .

1409. "PAVING IN THE FAST LANE," Concrete Construction, Vol. 32, No. 7, July 1987, pp. 618.

Describes the fast-track paving of one mile of a country road. The road was open to traffic after only 35 hr, complete with sawed and sealed joints, shoulders, and center stripe.

1410. "HOW LONG SHOULD PAVEMENT LAST?," Better Roads, Vol. 57, NO. 10, Oct 1987, pp. 32-34.

The life of pavement is affected by a variety of factors. The number and type of vehicles have the most significant impact. Climate, roadbed soil, and properties of that soil are all very important. Article researches reasons behind the failure of concrete and presents methods for evaluation of good performance. Results of some performance evaluations on different types of pavements are given along with a pavement performance comparison.

1411. ACI Committee 363, "RESEARCH NEEDS FOR HIGH-STRENGTH CONCRETE," ACI Materials Journal, Vol. 84, No. 6, Nov- Dec 1987, pp. 559-577.

See No. 1407.

1412. Acker, P. and Boulay, C. et al., "ON THE IMPORTANCE OF INITIAL STRESSES IN CONCRETE AND OF THE RESULTING MECHANICAL EFFECTS," Cement and Concrete Research, Vol. 17, No. 5, Sept 1987, pp. 755-764.

From various results of tests of crack propagation in mortars and concretes in different uniform hygral conditions and at different imposed displacement rates, the roles and importance of the various physical causes that might explain the nonlinearities observed during unloading are analyzed - overall viscoelasticity, confined viscoelasticity, and initial stresses. Various approaches reveal the importance of the initial stresses. If their role is confirmed, fruitful lines of investigation will be opened up in the field of the laws governing the mechanical behavior and fatigue of concrete.

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1413. Ahmad, S. H. and Shah, S. P., "HIGH STRENGTH CONCRETE - A NEW MATERIAL," Materials and. Member Behavior, Proceedings of the Sessions at Structures Congress '87, Orlando, FL, Aug 17-20 1987, pp. 421-434.

structural member behavior of normal and high-strength concretes are summarized. The current ACI code recommendations are based on results of concretes with compressive strengths less than 6000 psi. The code recommendations are examined in light of the results observed for material properties as well as structural member behavior.

In this paper, the material properties and

1414. Alegre, S. and Lechuga, J. et al., "NEW PREDICTION METHODS OF DURABILITY APPLICATION TO CONCRETE WITH AND WITHOUT FLY ASH," Concrete Durability. Katherine and Bryant Mather International Conference, Held at Atlanta, Georgia, USA, 27 April-May, 1987, pp. 681- 704.

As a consequence of increasing use of fly ash in Spain, which is added to concrete at the plant, several studies have been developed with the object of checking the performance of the concrete, specially with respect to its durability. These studies have been more intensely developed in catalonia, where fly ash from the cercs power station is extensively used in concrete production. Numerical examples given in this paper of concrete with fly ash refer specifically to fly ash from cercs, which is obtained from lignite type coal. To check some varialsles that influence durability (mechanical resistance, modulus of elasticity, creep of the concrete, etc) there exist some standard methods that use concrete samples. Nevertheless, to verify other variables, trials are usually done with paste or mortar samples, which have the risk of giving results different from those obtained with a concrete sample. This is why, in these studies, new test methods have been developed using concrete samples and very simple apparatus to measure some characteristics usually tested on pastes and mortars. These methods are briefly summarized in this paper; they measure: the permeability to liquids, the permeability to gas, liquid absorption, carbonation tests, diffusion of chloride ion and the resistance to sulphate attack. Finally, we verify that the durability of the reinforcements within the tested concrete would be foreseeable with the indicated tests, as measurements made with the resistance to polarization tech.nique give concordant results with those deduced from the above.

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1415. Alliche, A. and Francois, D., "FATIGUE DAMAGE OF CONCRETE," Fracture of Concrete and Rock: SEM-RILEM International Conference, Conf, No.11591, 1987, pp. 120-127.

Cyclic flexural load tests of simply supported beams under central concentrated charge were performed, for two different concrete Young modulus. The strain at the most tensioned fiber was measured during experiments. A model for cumulative damage which is proportional to the strain was used to present the results.

1416. Ansari, F., "STRESS-STRAIN RESPONSE OF MICROCRACKED CONCRETE IN DIRECT TENSION," ACI Materials Journal, Vol. 84, No. 6, Nov-Dec 1987, pp. 481-490.

Behavior of concrete subjected to uniaxial tension is studied by laser speckle interferometry. The main emphasis is given to development of a technique for detection of microcracks, measurements of the width of microcracking zone, and calculating microcrack growth. Microcrack-macrocrack evolution is described from experimental results. Unique post-peak stress-strain and stress-deformation behavior were not observed. The stress-strain response of concrete was found to be gage-length dependent. Strains measured within a gage length inside the microcracking zone were two orders of magnitude higher than the values measured previously.

1417. Attiogbe, E. K. and Darwin, D., "SUBMICROCRACKING IN CEMENT PASTE AND MORTAR," ACI Materials Journal, Nov- Dec 1987, pp. 491-500.

Submicroscopic cracking of cement paste and mortar under uniaxial compression is measured and compared to applied strain. Cement paste specimens with water- cement ratios of 0.7, 0.5, and 0.3 and mortar specimens with a water-cement ratio of 0.5 were tested at ages ranging from 27 to 29 days. After loading, slices of material were removed for study at a magnification of 1250x in a scanning electron microscope. Cracking on transverse and longitudinal surfaces was measured, and three-dimensional crack distributions were obtained from the surface crack data. The research demonstrates that surface crack density in cement paste and mortar is an order of magnitude greater than the density of bond and mortar microcracks in concrete at the same value of

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compress ive s t r a i n . i n c r e a s e s w i t h i n c r e a s i n g compress ive s t r a i n , whi le the number o f cracks per u n i t volume decreases. D i f f e r e n c e s i n water-cement r a t i o have a s m a l l b u t measu rab le effect on the crack d i s t r i b u t i o n s . C r a c k d e n s i t y i s lower i n i t i a l l y i n m o r t a r t h a n i n cement paste b u t i n c r e a s e s more :rapidl!y as compress ive s t r a i n i n c r e a s e s .

T h e mean s i -ze o f submic roc racks

1 4 1 8 . Ba laguru , P. and Ukadike, M. e t a l . , "FREEZE-THAW RESISTANCE OF POLYMER MODIFIED CONCRETE," C o n c r e t e D u r a b i l i t y . K a t h e r i n e and Bryan t Mather I n t e r n a t i o n a l Conference , A t l a n t a , Georg ia , USA, 27 April-May 1987, pp. 863-876.

T h i s paper p r e s e n t s t h e r e s u l t s cmf a n exper imenta l . i n v e s t i g a t i o n on t h e f r eeze - thaw d u r a b i l i t y of polymer m o d i f i e d c o n c r e t e (pmc) . B a s i c s l l y , p r i s m spec imens w e r e s u b j e c t e d t o a maximum o f 900 c y c l e s o f f r e e z i n g and thawing , u s i n g ASTM c666 p r c x e d u r e a . F i v e sets of spec imens w i t h v a r i o u s amounts of polymer c o n t e n t w e r e tested. The polymer c o n s i s t e d of a l i q u i d epoxy r e s i n and a c u r i n g a g e n t ( o r h a r d e n e r ) . Weight and fundamenta l t r a n s v e r s e f r equency were measured a t v a r i o u s i n t e r v a l s o f f r eeze - thaw c y c l i c l o a d i n g . The r e s u l t s i n d i c a t e t h a t t h e f r eeze - thaw d u r a b i l i t y o f p m c i s better t h a n t h a t o f non a i r - e n t r a i n e d p l a n c o n c r e t e . The pmc w i t h polymer-cement r a t i o o f 0 . 4 o r h i g h e r can w i t h s t a n d 900 c y c l e s o f f r e e z i n g and t h a w i n g .

1 4 1 9 . Bamforth, P . B. , "PROPERTIES OF H I G H STRENGTH LIGHTWEIGHT CONCRETE, C o n c r e t e (London) , V o l . 21, No.4, A p r 1987, pp. 8-9.

T h e p r o p e r t i e s o f l i gh twe igh t c o n c r e t e , manufac tu red u s i n g Lytag , d i f f e r s i g n i f i c a n t l y from t h o s e of c o n c r e t e s u s i n g gravel o r c r u s h e d r o c k aggregate. T h i s a r t ic le c o n t a i n s a summary of t h e r e s u l t s of tests carried o u t by Taywood E n g i n e e r i n g t o compare t h e b e h a v i o r of two Grade 40N c o n c r e t e s , one c o n t a i n i n g Ly tag 12mm aggregate and t h e o t h e r c o n t a i n i n g 20mm gravel. P r o p e r t i e s which have been measured i n c l u d e : water p e r m e a b i l i t y , a i r p e r m e a b i l i t y , direct t e n s i l e s t r e n g t h and s t r a i n c a p a c i t y , f l e x u r a l s t r e n g t h (modulus of r u p t u r e ) and s t r a i n c a p a c i t y , bond s t r e n g t h , e l a s t i c modulus and creep, and thermal e x p a n s i o n c o e f f i c i e n t .

1.7 6

1420. Banthia, N. P. and Mindess,'S. et al., "IMPACT BEHAVIOUR OF CONCRETE BEAMS," Mater Struct, Vol. 20, NO. 118, 1987, pp. 293-302.

An instrumental impact machine was used to carry out impact tests on concrete beams, 100 X 125 mm in cross-section and 1400 mm long. The simply supported beams were struck at their midpoints by a 345 kg mass impact hammer, dropped from various heights. The instrumentation included strain gages mounted on the striking end of the hammer, strain gages mounted on one support anvil, and three accelerometers placed at various locations along the beam. The data were collected using a 5-channel data acquisition system. Normal strength, high strength, and fiber reinforced concrete beams were tested.

1421. Bazant, Z. P. and Wittmann, F. H. et al., "STATISTICAL EXTRAPOLATION OF SHRINKAGE DATA - PART I: REGRESSION," ACI Materials Journal, Vol. 84, No. 1, Jan-Feb 1987, pp. 20-34.

A large series of data on carefully controlled shrinkage tests of concrete involving groups of large numbers of identical specimens is reported. The data are used to compare existing shrinkage formulas in ACI, CEB-FIP, and BP modes. By far the best agreement is obtained for the BP model. Assuming that only the measured data for a certain initial period are known, predictions are made for long time and are compared. Best predictions are obtained when the shrinkage formula is fitted to test data using nonlinear optimization, then linear regression in transformed variables is used to obtain the confidence limits for long-time predictions. It is concluded that good long- time predictions of shrinkage can be obtained on the basis of shrinkage t e s t results on 80 mm diameter cylinders for a 3-week duration.

1422. Bazant, Z. P. and Chern, J.-C., "STRESS-INDUCED THERMAL AND SHRINKAGE STRAINS IN CONCRETE," Journal of Engineering Mechanics, Vol. 113, No. 10, Oct 1987, pp. 1493-1511.

A previous material model for the increase of creep of concrete caused by simultaneous drying is extended to describe the effect of both drying and wetting, as well as the increase of creep caused by temperature changes, both heating and cooling. The creep increase due to temperature changes, sometimes called the transitional thermal creep, is physically the same phenomenon as the increase of creep due to humidity

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changes, known as the P i c k e t t effect ( o r t h e d r y i n g c r e e p e f fec t ) . I n accord w i t h the p rev ious model f o r d r y i n g creep a lone , t h e p r e s e n t extended model e x p l a i n s t h e i n c r e a s e of c r e e p clue t o humidi ty o r t empera tu re changes as a consequence o f p r i n c i p a l l y t w o effects: (1) St ress - induced sh r inkage ( o r s w e l l i n g ) o r s t r e s s - induced thermal expansion ( o r c o n t r a c t i o n ) ; and ( 2 ) t h e d i s t r i . b u t e d t e n s i l e c r a c k i n g ( o r s t r a i n - s o f t e n i n g ) of c0ncret.e.

1 4 2 3 . Bazant, Z. P. and Sener, S. e t al., “EFFECT OF CRACKING ON DRYING PERMEABILITY AND DIFFUSIVITY O F CONCRETE, ACI Materials Journal., Sept -Oct 1987, pp. 351-357.

The i n c r e a s e o f o v e r a l l d ry ing p e r m e a b i l i t y and d i f f u s i v i t y of c o n c r e t e due t o c r a c k i n g i s determined expe r imen ta l ly and formulated mathematical ly . T h e tes t specimens are C-shaped beams deformed b y a t i e r o d and r e i n f o r c e d on the t e n s i l e face s o t h a t uni formly spaced cracks are produced. i n the l o s s o f weight f o r v a r i o u s d r y i n g p e r i o d s between cracked and uncracked specimens i s measured and used t o q u a n t i f y the effect on p e r m e a b i l i t y and d i f f u s i v i t y . The o v e r a l l d ry ing d i f f u s i v i t y and p e r m e a b i l i t y i n t h e c rack ing d i r e c t i o n , which i s t h e o r e t i c a l l y p r o p o r t i o n a l t o the c rack w i d t h cubed and i n v e r s e l y p r o p o r t i o n a l t o the c rack spac ing , i s found t o i n c r e a s e about 2 .25 t i m e s f o r crack w i d t h 0 . 1 mm and crack spac ing 70 mm. Although appreciable, t h i s v a l u e i s two orders of magnitude less than the t h e o r e t i c a l upper bound p r e d i c t e d on t h e basis of v i s c o u s f l o w c a l c u l a t i o n ( i f it i s assumed t h a t t h e cracks are o f c o n s t a n t t h i c k n e s s , have p l a n a r w a l l s , and are cont inuous . I t i s concluded t h a t even though t h e major cracks are seen t o be cont inuous on t h e specimen s u r f a c e , t h e y must be d i scon t inuous i n t h e specimen i n t e r i o r , perhaps be ing i n t e r c o n n e c t e d by much narrower necks w i t h a w i d t h about 1 0 t i m e s smaller. T h i s fact i s of i n t e r e s t f o r deducing f r a c t u r e p r o c e s s zone models from v i s u a l o b s e r v a t i o n s o f cracks on the specimen s u r f a c e . Although approximate, t h e p r e s e n t l y derived formula f o r t h e i n c r e a s e o f d i f f u s i v i t y and p e r m e a b i l i t y i s d i r e c t l y u s a b l e i n f i n i t e element programs f o r d r y i n g o r w e t t i n g of conc re t e .

The d i f f e r e n c e

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1424. Ben tu r , A. and Mindess, S. e t a l . , "BEHAVIOUR OF REINFORCED CONCRETE UNDER IMPACT: THE EFFECT OF CONSTRENGTH," F r a c t u r e o f C o n c r e t e and Rock: SEM-RILEM I n t e r n a t i o n a l Conference , Houston, TX, 1987, pp. 449- 458.

The response o f r e i n f o r c e d c o n c r e t e beams t o impact l o a d i n g w a s s t u d i e d , u s i n g a n i n s t r u m e n t e d drop-weight impact machine employing a 3 4 5 kg mass, and d r o p h e i g h t s o f 0 . 5 m and 1. 5 m. I t w a s found t h a t , unde r impact l o a d i n g , t he l o a d b e a r i n g c a p a c i t y o f t he beams w a s i n c r e a s e d , compared t o s t a t i c l o a d i n g . However, w h i l e f o r normal s t r e n g t h c o n c r e t e , t h e a b i l i t y t o s u s t a i n larger d e f l e c t i o n s i n c r e a s e d u n d e r impact, f o r h i g h s t r e n g t h c o n c r e t e the reverse w a s t r u e . Thus, t h e e n e r g y a b s o r p t i o n c a p a c i t y o f normal s t r e n g t h c o n c r e t e i n c r e a s e d unde r impact l o a d i n g ; t h e e n e r g y a b s o r p t i o n c a p a c i t y o f t h e h i g h s t r e n g t h c o n c r e t e decreased.

1425. Brameshuber, W. and H i l s d o r f , H. K . , "DEVELOPMENT O F STRENGTH AND DEFORMABILITY OF VERY YOUNG CONCRETE," F r a c t u r e o f C o n c r e t e and Rock: SEM-RILEM I n t e r n a t i o n a l Conference , Jun 17-19 1987, pp. 655-667.

A d e s c r i p t i o n of e x p e r i m e n t s c o n c e r n i n g t he development o f s t r e n g t h and d e f o r m a b i l i t y i n c l u d i n g f r a c t u r e mechanics parameters o f v e r y young c o n c r e t e i s g i v e n . I t i s shown t h a t the s t r e n g t h o f c o n c r e t e i n c r e a s e s d u r i n g t h e obse rved p e r i o d from 4 h o u r s t o 28 d a y s a f t e r c a s t i n g whereas t h e d e f o r m a b i l i t y - e. g. r e p r e s e n t e d by t he d e f l e c t i o n o f n o t c h e d beams a t maximum l o a d - decreases u n t i l a minimum i s reached and t h e n i n c r e a s e s a g a i n . The character is t ic l e n g t h l / / c / / h may be i n f l u e n c e d by h y d r a t i o n t e m p e r a t u r e b u t n o t the n o t c h s e n s i t i v i t y ; l / / c / / h r e a c h e s a maximum around 8 h o u r s and t h e n decreases c o n t i n u o u s l y up t o a n age o f 28 days .

1 4 2 6 . Buck, A., "USE O F CEMENTITIOUS MATERIALS OTHER THAN PORTLAND CEMENT," Concre t e D u r a b i l i t y . K a t h e r i n e and Bryan t Mather I n t e r n a t i o n a l Conference , A t l a n t a , Georg ia , USA, 27 April-May 1987, pp. 1863-81.

D i f f e r e n t amounts of f l y a s h , s i l i c a fume, o r ground g r a n u l a t e d i r o n b l a s t - f u r n a c e s lag have been u s e d w i t h p o r t l a n d cement i n a n e f f o r t t o p r e v e n t e x c e s s i v e expans ion due t o a l k a l i - s i l i c a r e a c t i o n o r s u l f a t e a t t a c k o r b o t h . The t e s t methods u s e d t o e s t ab l i sh optimum p r o p o r t i o n s w e r e ASTM c 4 4 1 and ASTM c 1012. Once t h e optimum p r o p o r t i o n s w e r e known, c o n c r e t e m i x t u r e s w e r e made and tested. (Author/TRRL)

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1 4 2 7 . Bu i l , M . , "VERY H I G H PERFORMANCE; MATERIALS FOR C I V I L ENGINEERING BASED UPON S I L I C A FUMES, It Travaux, 1 9 8 7 , pp. 8-12.

The u s e of s i l i c a fumes, a by-product of t h e s i l i c o n i n d u s t r y , i s s t i l l no t widespread. However, combined w i t h cement and aggrega te s , these fumes make it p o s s i b l e t o o b t a i n ou t s t and ing s t r e n g t h i n mor ta r and conc re t e , as w e l l as above average f l u i d i t y . Based upon an e x t e n s i v e b ib l iog raphy , t h e a u t h o r reviews t h e c h a r a c t e r i s t i c s of s i l i c a fumes and t h e n d e s c r i b e s their a c t i o n i n combination w i t h cement. T h e d ive r s i ty o f these fumes are demonstrated,, a long w i t h some examples of r e s u l t s achieved.

1 4 2 8 . B u t l e r , W. and B a w e j a , D . , "LONG-TERM D U R A B I L I T Y O F FLY ASH CONCRETES I N C I V I L ENGINEERING STRUCTURES," Concrete D u r a b i l i t y . Kather ine i3nd Bryant Mather I n t e r n a t i o n a l Conference, H e l d a t A t l a n t a , George, USA, 27 April-May, 1987, pp. 513-40.

R e s u l t s are p r e s e n t e d on r e c e n t s t u d i e s undertaken i n England, Georgia, USA and A u s t r a l i a on t h e d u r a b i l i t y o f a var ie ty of c o n c r e t e s t r u c t u r e s c o n t a i n i n g f l y a sh . F ive of these s t r u c t u r e s have been i n service f o r over fiftee.2 y e a r s and some provided comparisons between f l y ash c o n c r e t e and p l a i n c o n c r e t e . Detai ls of the f l y ashes used i n t he s t r u c t u r e s are suppor ted by background data on fly ash a v a i l a b i l i t y and u s e i n t h e a r e a s concerned. Design, c o n s t r u c t i o n and service d e t a i l s f o r t h e s t r u c t u r e s are p r e s e n t e d a long w i t h f i n d i n g s of o n - s i t e i n s p e c t i o n s . Assessments were made o f : f l y a s h h y d r a t i o n characteristics; dep th o f carbonat ion; f u n c t i o n a l e f f i c i e n c y and v i s ib le d e t e r i o r a t i o n . Links are ascribed between the determined v a l u e s .

1 4 2 9 . Chapman, R. A. and Shah, S . P . , "EmLY-AGE BOND STRENGTH I N REINFORCED CONCRETE," A C I M a t e r i a l s J o u r n a l , Nov-Dec 1987, pp. 501-510.

An i n v e s t i g a t i o n w a s conducted t o de te rmine t h e bond s t r e n g t h between r e i n f o r c i n g st.eel and c o n c r e t e loaded a t e a r l y ages. Bond tests w e r e conducted us ing a s p e c i a l l y developed p u l l o u t tes t . Load-s l ip characterist ics of smooth and deformed b a r s w e r e compared f o r specimens w i t h d i f f e r e n t bar-embedment l e n g t h s and tested a t v a r i o u s ages from 1 t o 28 days of c u r i n g . Smooth b a r s d i d no t e x h i b i t any age effect . However, t h e bond c h a r a c t e r i s t i c s o f deforined

1 8 0

bars showed a significant age effect. It was observed that the ACI Building Code-suggested equation for development length overestimated test results for very early ages. An alternate relationship is examined for structures loaded at early ages.

1430. Chin, D., "STEEL CORROSION IN CONCRETE: CAUSES AND

NON-CHLORIDE ACCELERATOR," Corrosion, Concrete and Chlorides, ACI SP-102, 1987, pp. 49-77.

Two important properties of calcium nitrite are that it is an accelerator and a corrosion inhibitor when used as an admixture in concrete. With its performance as an accelerator enhanced, calcium nitrite can be used as an effective non-corrosive, non-chloride accelerator in normal and fly ash concrete. The calcium nitrite-based accelerator provides good acceleration in initial setting times at 50 deg f (10 Dec c) and 72 deg f (22 deg c) and produces a significant improvement in compressive strengths at early ages. Electrochemical solution tests can be used to conduct a quick screening test to determine the potential corrosivity of a non-chloride accelerator. Potential and linear polarization resistance measurement tests provide a quick indication regarding the potential corrosivity of a non-chloride accelerator. (Author/TRRL)

RESTRAINTS. A CALCIUM NITRITE-BASED, NON-CORROSIVE,

1431. Clarke, J. L., "SHEAR STRENGTH OF LIGHTWEIGHT AGGREGATE CONCRETE, Concrete (London), V01.21, No.4, April 1987, pp. 12-13.

Lightweight aggregate concrete has been available for a number of years but apart from block masonry, has been widely used in structural applications. Some notable structures have been built however, such as grandstands, using prestressed lightweight concrete having a characteristic cube strength up to 60N/mm**2. Lightweight aggregate concrete has been used on a very small scale for bridges in the UK but in America and on the continent, it has been used for a number of structures, showing overall savings in total cost of between 10 and 20 per cent of the equivalent normal weight structure. Most of the lightweight aggregates suitable for concrete are factory made and include sintered pulverized fuel ash, pelletized slag and expanded clay, shale and slate. Those suitable for structural use, i. e. , above 25N/mm**2 at 28 days, will have densities between 1400kg/m**3 and 2000kg/m**3. It is possible to achieve strengths in excess of 50N/mm**2 but this is usually done by using

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lightweight coarse aggregate combined with a natural sand.

1432. Clifford, D. J. and Koretsky, A. V., "CREEP AND SHRINKAGE OF THE GATEWAY BRIDGE CONCRETE," Australian Road Research, Vol. 17, No. 2, Jun 1987, pp. 111-128.

The recently completed gatewa.y bridge is the largest concrete portal bridge in the world. Spanning Quarries Reach of the Brisbane FAver, Brisbane, Queensland, the 260 m main span consists of a single cell box girder varying in depth from 15. 2 m at the piers to 5. 2 m at center span. The mainspan superstructure was built by the cantilever method of construction from each of the main river piers, finally becoming continuous upon stressing of the center span segment. No curing was implemented anywhere on the bridge. Stressing occurred at age two days after casting on the mainspan superstructure. A testing program was initiated to determine the creep and shrinkage characteristics of the mainspan superstructure concrete. Compari.sons of the experimental results and the theoretical CEB- FIP/NAASRA predictions are presented.

1433. Delibes Liniers, A., "MICROCRACKING OF CONCRETE UNDER COMPRESSION AND ITS INFLUENCE ON TENSILE STRENGTH," Mater Struct, V01.20, No.116, Mar 1987, pp. 111-116.

A new parameter representing damage of concrete due to compressive stresses is investigated. Very important tensile strength losses are obtained after compressive loading over 40% of the compressive strength. Microcracking of concrete takes place under such load leading to tensile strength losses depending also on time under load, water content and type of aggregate. Under maximum compressive load a tensile strength reduction of about 50% is obtained.

1434. Dennison, A., "HERE COME THE "SCIPERCEMENTS", 'I Roads and Bridges, Vol. 25, No. 7, July 1987, pp. 34-36.

"Supercements" and "superpavers" are expected to change the concrete paving industry by offering faster paving alternatives.

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1435. Dhir, R. and Tham, K. et al., 11DUR2U31LITY OF CONCRETE WITH A SUPERPLASTICIZING ADMIXTURE," Concrete Durability. Katherine and Bryant International Conference,Atlanta, Georgia, USA, 27 April-May 1987, pp. 741-64.

The results of a wide-ranging study undertaken to examine the effect of a superplasticising admixture on the durability of normal-workability concretes are reported. The investigation was based on cement- reduced concrete mixes covering a range of 28 day strength from 20 to 65 mpa, with water-reduced concretes included to increase the data base. Corresponding normal concretes were used for comparison. The experimental programme covered included measurements of air and water permeability to assess the overall durability potential; the rates of carbonation and chloride ion diffusion to assess the possible risk of steel reinforcement corrosion in concrete; and the deterioration under alternate freezing and thawing and wetting and drying to assess the resistance of concrete to frost attack and weathering. The results showed that, f o r a given workability and design strength, the use of a superplasticising admixture can be expected to effect improvement in the durability of concrete.

1436. Dolch, W. and Lovell, J., "WETTING AND DRYING AS INDICATORS OF WATER/CEMENT RATIO," Concrete Durability, Proceedings, American Concrete Institute, SP 100-29, Volume 1, 1987, pp. 509-518.

Rate of wetting by capillary absorption and rate of drying from the saturated state were determined on mature cement pastes with w/c ratios of 0.40 and 0.60. The cumulative water gained or lost was parabolically related to time. The coefficients of this relationship, for both the wetting and the drying data, were two to three orders of magnitude larger for the pastes with w/c = 0.6 than for those with w/c = 0.4.

1437. Dunstan, E., "SULFATE RESISTANCE OF FLY ASH CONCRETES - THE R-VALUE," Concrete Durability. Katherine and Bryant Mather International Conference, Atlanta, Georgia, USA, 27 April-May 1987, 1987, pp. 2027-40.

the use of subbituminous and lignite fly ashes in concrete. By 1978 that research had lead to the development of the fly ash r-value as an advance

In 1973 the bureau of reclamation began research on

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i n d i c a t o r of p o t e n t i a l s u l f a t e r e s i s t a n c e of c o n c r e t e s c o n t a i n i n g f l y ash . The r-value i s c a l c u l a t e d from results of a chemical a n a l y s i s of t h e f l y a s h as (%cao-S)/%fe203. This paper i s a review (ano the r look a t t h e r-value) a f t e r more t h a n 1 2 years of s u l f a t e r e s i s t a n c e t e s t i n g . Many o f t he f l y ash c o n c r e t e s i n t h i s research have f a i l ed i n s u l f a t e t e s t i n g over t h e l a s t 1 2 years; however, many of these c o n c r e t e s have n o t f a i l e d and are s t i l l under t e s t . These s u l f a t e r e s i s t a n c e t es t r e s u l t s i nd ica t e t h a t t h e r -va lue remains a good i n d i c a t o r of p o t e n t i a l s u l f a t e r e s i s t a n c e o f f l y a s h conc re t e s . When c o n c r e t e c o n t a i n s 15-25% f l y ash wi th an r -va lue less t h a n 3 . 0 the s u l f a t e r e s i s t a n c e w i l l be equal. o r bet ter t h a n a c o n c r e t e w i t h t he same cement and no f l y ash.

1438. EKrenchel, H. and B i c k l e y , J. A. , V U L L O U T TESTING OF CONCRETE: HISTORICAL BACKGROUND AND S C I E N T I F I C LEVEL TODAY," Nordic Concrete Research, No.6, D e c 1987, pp. 155-168.

D i f f e r e n t p u l l o u t , p u l l o f f o r break-off systems have been developed over t he y e a r s f'or de te rmining c o n c r e t e s t r e n g t h . T h i s s tudy c o n t a i n s a survey of %he d i f f e r e n t p u l l o u t systems developed f o r c o n t r o l l i n g c o n c r e t e s t r e n g t h w i t h an examinat ion of stress- and s t r a i n - d i s t r i b u t i o n i n s i d e t he c o n c r e t e a t peak l o a d by t h e Scandinavian p u l l o u t t e s t i n g system.

1439. E l - J a z a i r i , B., "THE PROPERTIES OF HARDENED MPC MORTAR AND CONCRETE RELEVANT TO THE REQUIREMENTS OF RAPID REPAIR OF CONCRETE PAVEMENTS," Concrete , Vol. 2 1 , N o . 9, Sep 1987, pp. 25-31.

There is an i n c r e a s i n g need f o r new materials and methods f o r r a p i d b u t du rab le r e p a i r of c o n c r e t e pavements where t h e c l o s u r e t i m e i s i n hours ra ther t h a n days. The a u t h o r o u t l i n e s t h e main p r o p e r t i e s and r e p o r t s on some a s p e c t s of d u r a b i l i t y derived from l a b o r a t o r y i n v e s t i g a t i o n and f i e l d exper ience . Magnesia phosphate cement (mpc) based materials p rov ide a workable mix s e t t i n g w i t h i n 15 minutes a t normal t empera tu res and harden t o s u f f i c i e n t s t r e n g t h w i t h i n one hour . Unlike most f a s t s e t t i n g , e a r l y s t r e n g t h materials, mpc mor ta r can be cons ide red d imens iona l ly s table . I ts c o e f f i c i e n t o f thermal expansion f a l l s w i t h i n t h e ranqe o f conven t iona l mor ta r and conc re t e , and i t s modulus of e l a s t i c i t y i s s imi l a r t o h igh - s t r eng th c o n c r e t e when tes ted under i d e n t i c a l c o n d i t i o n s . Pul l -out tests show a s a t i s f a c t o r y s t r e n g t h of bond wi th s tee l . Although mpc material has a low p e r m e a b i l i t y it a l lows w a t e r

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vapor to diffuse through the matrix. Experience has shown that fuels, engine oils, urea, and other deicing materials have no effect on mpc repair patches. Details are given of successful applications on roads, motorways, bridge decks, airfields, and industrial floors.

1440. Farbiarz, J. and Carrasquillo, R., "ALKALI-AGGREGATE REACTION IN CONCRETE CONTAINING FLY ASH.," Concrete Durability. Katherine and Bryant Mather International Conference, Atlanta, Georgia, USA, 27 April-May 1987, 27 April-May 1987, pp. 1787-808.

The effectiveness of the use of fly ash in concrete in order to reduce the damage to concrete due to alkali-aggregate reaction tb acceptable levels was investigated. More than 1300 mortar-bars were cast and tested according to the mortar-bar test method, ASTM c 227, with 0, 17, 26, 34, 45, and 62 percent replacement of the volume of cement in the mixture with fly ash. The effect of silica fume in the mixture was compared to that of fly ash at 17, 34, and 45 percent cement replacement by volume. The variables studied included: type of aggregate, alkali content of the cement, type of pozzolan, percent of cement replacement, ph of mixing water, and blending of the cement with the fly ash. Both ASTM class c and class f fly ashes were investigated. The results indicate that the replacement of a portion of the volume of cement with an equivalent volume of fly ash tends to reduce the expansion caused by the reactivity between alkalies and reactive silica in the aggregate provided the proper amount of cement is replaced. This amount appears to depend on the alkali content of the fly ash and on the chemical composition of the fly ash used, mainly calcium oxide content. For some high calcium fly ashes having more than 1.5 percent available alkalies content, a 'pessimum limit' was observed. Such a limit represents a percent replacement under which the addition of fly ash causes equal or greater expansions in the mortar-bars than that of the mixture without fly ash, and above which the expansions are reduced. In some instances more than one 'pessimum limit' was detected for a given combination of materials.

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1 4 4 1 . Faulkner , T. and Walker, R. , “ R I l S I D ONE-CYCLE TEST FOR EVALUATING AGGREGATE PERFORMANCE WHEN EXPOSED TO FREEZING AND THAWING I N CONCRETE,. , I’ Concrete D u r a b i l i t y . Kather ine and Bryant Mather I n t e r n a t i o n a l Conference, A t l a n t a , Georgia, USA, 27 April-May 1987, pp. 705-22.

Previous work demonstrated t h a t c a r e f u l l y monitored l e n g t h change measurements d u r i r g the f irst f r e e z e p e r i o d o f a c o n c r e t e specimen cclntaining t h e aggrega te b e i n g e v a l u a t e d show a ’ f i n g e r p r i n t ‘ t h a t can be s u c c e s s f u l l y c o r r e l a t e d w i t h the! ‘ d u r a b i l i t y f a c t o r ‘ t h a t i s ob ta ined af ter many l a t e r c y c l e s of f r e e z i n g and thawing. S i x d i f f e r e n t c o a r s e aggregates w e r e used i n t h i s s tudy t o (1) f u r t h e r s u b s t a n t i a t e t h e conc lus ions of t h e prev ious work: and t o ( 2 ) attempt t o s h o r t e n t h e test e v a l u a t i o n proc:edure from eight t o three days. T h e s l o p e of the cumulat ive l e n g t h change vs temperature and t h e l e n g t h change vs t i m e curve of the first f r e e z e c y c l e nea r t h e f r e e z i n g p o i n t of water w a s used as the ‘ f inge rp r i . n t ‘ . Although attempts t o s h o r t e n t h e procedure by u s i n g a b o i l i n g w a t e r accelerated c u r i n g procedure w e r e cons ide red s u c c e s s f u l , it w a s recommended t .hat o t h e r methods of a c c e l e r a t i n g e a r l y s t r e n g t h s be a t tempted . T h e tests i n d i c a t e d t h a t t h e procedure w a s s a t i s f a c t o r y f o r s c r e e n i n g aggregates having a d u r a b i l i t y f a c t o r of less t h a n 30 and greater t h a n 50 p e r c e n t .

1442. Fowler, D. W. , “POLYMER CONCRETE FOR STRUCTURAL APPLICATIONS, ’’ Materials and Member Behavior, Proceedings o f t h e Sess ions a t S t r u c t u r e s Congress ‘87, Orlando, FL, 1987, pp. 389-400.

Polymer c o n c r e t e (PC) has been used e x t e n s i v e l y i n t h e Uni ted S t a t e s p r i m a r i l y a s a r e p a i r material f o r p o r t l a n d cement conc re t e . The e x c e l l e n t f l e x u r a l and compressive s t r e n g t h d u r a b i l i t y and bond t o p o r t l a n d cement c o n c r e t e have made it a ve ry a t t rac t ive r e p a i r material. There has a l s o been c o n s i d e r a b l e i n t e r e s t in PC f o r s t r u c t u r a l a p p l i c a t i o n s . T h i s paper d i s c u s s e s f l e x u r a l , shear, and c y c l i c behavior of r e i n f o r c e d P C beams and f l e x u r a l behavior of u n r e i n f o r c e d sandwich beams w i t h PC f a c i n g s .

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1443. Fraay, A. and Reigersman, A. et al., "SULFATE RESISTANCE OF MORTARS WITH PULVERIZED FUEL ASH.," Concrete Durability. Katherine and Bryant Mather International Conference, held at Atlanta, Georgia, USA, 27 April-May 1987, pp. 2041-58.

This paper deals with sulfate attack on mortars containing fly ashes. Mortars of ordinary portland cement (Dutch portland cement, class a) and of blast furnace slag cement were investigated. Two different sand gradings were used (sand up to 2 mm and sand up to 4 mm) as well as two different water contents (water/(cement + fly ash)-ratio = 0.45 and 0.50). At various time intervals during the tests, the length changes were measured. The tests were performed with various concentrations of na2so4 solution. At several intervals the ph of the solution was restored to 7-8 by titration with a h2so4 solution. Seven different fly ashes were tested. In one series, instead of the fly ash a fine graded sand was used as replacement of cement. The specimens were stored for one month at constant relative humidity of 95%. After immersion of 5 months in the na2so4-solution, the bending strength, the compressive strength and the pulse velocity of the specimens were measured. The sulfate attack turns out to be controlled by the fly ash and the amount of entrapped air in the mortars. With a w/(c+fa) ratio of 0.5 (good workability mortars), the finer fly ashes will give a good sulfate resistance. with the higher air contents will show a higher sulfate demand (to restore the ph) at increasing (water+air) / (cement+fly ash) ratio (in volume/volume) . The porosity factor and strength has a greater effect than the c3a content of the portland cement, for the mortar with sand instead of fly ash as cement replacement showed more degradation than reference mortar.

The specimen

1444. Gibson, F., "CORROSION, CONCRETE, AND CHLORIDES. STEEL CORROSION IN CONCRETE: CAUSES AND RESTRAINTS," American Concrete Institute SP-102, 1987, pp. 176.

Industry and engineering concern about corrosion of reinforcement in portland cement concrete, and the need to disseminate state-of-the-art information about corrosion motivated the planning of three independent sessions related to corrosion of steel in concrete at the March 1985 ACI Convention. This volume is a compilation of some of the papers presented at these sessions, plus an edited transcript of the Forum, and one additional paper solicited to round out the coverage of the subject. The papers deal with a

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var ie ty o f aspects o f co r ros ion . They i n c l u d e t h e marked i n f l u e n c e of c h l o r i d e i n caus ing c o r r o s i o n , t he chemis t ry of c o r r o s i o n a s tr iggered by c h l o r i d e t h a t r e s u l t s i n t he i n t e r n a l e lec t r ica l mechanism of c o r r o s i o n , ways f o r c o n t r o l l i n g c o r r o s i o n b y u s i n g c h l o r i d e - f r e e a c c e l e r a t o r s (and t he i r effects on the s e t t i n g and s t r e n g t h of c o n c r e t e ) , t h e r e d u c t i o n of c h l o r i d e p e n e t r a t i o n through use of pozzo lan ic b las t - fu rnace s lag as an admixture i n conc re t e , and t h e conduct ive c o a t i n g a s p e c t s of ca.thodic p r o t e c t i o n . The r e p o r t on t h e Forum ranges over a l l o f these t o p i c s , and more.

1445. Gopalan, M. and Haque, M. , "EFFE:CT OF CURING REGIME ON THE PROPERTIES O F FLY-ASH CONCRE:TE," American Concrete I n s t i t u t e , J o u r n a l of, V o l . 84, N o . 1, Jan 1987, pp. 6 .

Repor ts on t h e compressive arid f l e x u r a l s t r e n g t h of normal and f ly-ash c o n c r e t e s cured i n a fog room and i n an u n c o n t r o l l e d environment. Three classes of p l a i n c o n c r e t e w i t h water-cement: r a t i o v a r y i n g from 0.33 t o 0.47 were used. The f l y ash c o n t e n t of t h e modif ied mixes ranged from 20 t o 50 p e r c e n t by volume o f t h e t o t a l cemen t i t i ous material . The d r y i n g sh r inkage characteristics of these c o n c r e t e s are a l s o p r e s e n t e d . T h e c u r i n g c o n d i t i o n s i n f l u e n c e d t h e compressive s t r e n g t h of t he c o n c r e t e s s i g n i f i c a n t l y ; t h e 91-day a i r - c u r e d s t r e n g t h w a s less t h a n t h e 7-day fog-cured s t r e n g t h . T h e r a t i o of t h e c o n t r o l t o fly- a s h s t r e n g t h increased wi th age and t h e f ly-ash- cernent i t ious r a t i o . Poor c u r i n g i s concluded t o be more d e t r i m e n t a l t o t h e compressive s t r e n g t h development of f ly -a sh c o n c r e t e as compared t o normal c o n c r e t e .

1 4 4 6 . Greenhut, S., "CONCRETE," Cons t ruc to r , V o l . 69, No. 11, NOV 1987, pp. 17-20.

Today ' s concrete is s t ronge r , m o r e du rab le , and more complex t h a n ever. While s t r e n g t h s have been inc reased ; however, there is growing concern t h a t mar-y c o n c r e t e s cast today are no t as r e s i s t a n t as possible t o ab ras ion , chemical a t t a c k , 0:: o t h e r t ypes of d e t e r i o r a t i o n . I n a d d i t i o n , many c o n c r e t e s t r u c t u r e s b u i l t 30 t o 4 0 years ago a r e now i n need of r enova t ion . T h i s a r t i c l e looks i n t o each of these problems and gives more s p e c i f i c s . Research and q u a l i t y c o n t r o l are i n t e g r a l p a r t s i n s o l v i n g t h i s dilemma. Admixtures are described i n d e t a i l as a p o s s i b l e s o l u t i o n t o conc re t e problems.

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1 4 4 7 . Ha lvor sen , G., L e w i s H. T u t h i l l I n t e r n a t i o n a l Symposium on Concre t e and C o n c r e t e C o n s t r u c t i o n , 1987, pp. 360.

T h i s volume c o n t a i n s t h e papers p r e s e n t e d a t t he L e w i s H . T u t h i l l I n t e r n a t i o n a l Symposium on C o n c r e t e and C o n c r e t e C o n s t r u c t i o n , held a t t he ACI F a l l Convent ion i n S e a t t l e , November 9-13, 1987. T h e papers c o v e r t he f o l l o w i n g areas: d e s i g n , c o n s t r u c t i o n practice, c o n c r e t e q u a l i t y , admix tu res , bonding i n polymer c o n c r e t e , unde rwa te r c o n c r e t i n g (tremie c o n c r e t e ) , c o n c r e t e c u r i n g , high s t r e n g t h c o n c r e t e , c o n s o l i d a t i o n , d u r a b i l i t y , c o l d and h o t weather c o n s t r u c t i o n , and c a t h o d i c p r o t e c t i o n .

1448. Heinz, D. and Ludwig, C . , "MECHANISM OF SECONDARY ETTRINGITE FORMATION I N MORTARS AND CONCRETES SUBJECTED TO HEAT TREATMENT.," C o n c r e t e D u r a b i l i t y . K a t h e r i n e and Bryan t Mather I n t e r n a t i o n a l Conference , A t l a n t a , Georg ia , USA, 27 April-May 1987, 1987, pp. 2059-71.

I n t h e l a s t y e a r s , precast u n i t s made o f h i g h s t r e n g t h c o n c r e t e , and h a v i n g been h e a t t rea ted d u r i n g p r o d u c t i o n , have shown p a r t l y damaged s t r u c t u r e related t o loss of s t r e n g t h . T h i s damage a lways o c c u r r e d i n t h o s e b u i l d i n g components which, f o r several y e a r s , had been s u b j e c t e d t o o p e n - a i r w e a t h e r i n g (e.g. F r o n t p a n e l s and sleepers). The damage has o f t e n been c h a r a c t e r i z e d by crack f o r m a t i o n emerging from the edges o f t h e b u i l d i n g components, as w e l l as by a l o s s o f bond between the cement paste and t h e c o a r s e aggregate. I n o r d e r t o c l a r i f y t h i s damage, a series o f parameters have been examined as t o t h e i r i n f l u e n c e on t h e d u r a b i l i t y o f h e a t t rea ted concretes. Beside o t h e r s , t h e i n v e s t i g a t i o n c o n c e n t r a t e d on t h e f o l l o w i n g subjects: t h e t h r e s h o l d t e m p e r a t u r e of damage, t h e s o 3 c o n t e n t o f t he cement, t he h u m i d i t y o f s t o r a g e , and t he w / c .

1449. Holand, I., "UTILIZATION OF H I G H STRENGTH CONCRETE," Tapir P u b l i s h e r s , T h e Norwegian I n s t i t u t e o f Technology, Trondheim, The N e t h e r l a n d s , 1987, pp. 688.

P r o c e e d i n g s o f symposium he ld i n Norway i n June 1987 i n c l u d e 5 4 papers. H i g h - s t r e n g t h c o n c r e t e has been t h e f o c u s of b o t h research and prac t ica l u s e i n Norway f o r several y e a r s , p a r t i c u l a r l y due t o t h e p o t e n t i a l c o s t s a v i n g s of u s i n g t h e ma te r i a l i n o f f s h o r e c o n c r e t e s t r u c t u r e s . T h e symposium w a s he ld i n S tavange r , t he c e n t e r f o r t h e c o n s t r u c t i o n of

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o f f s h o r e c o n c r e t e p l a t fo rms . Purpose w a s t o b r i n g t o g e t h e r e x p e r t s i n t h i s f i e l d t o d i s c u s s developments. Proceedings give overview of p r e s e n t knowledge of v a r i o u s a s p e c t s wit .hin t he area, i n c l u d i n g materials; mechanical p r o p e r t i e s i n c l u d i n g f a t i g u e , des ign , and c o n s t r u c t i o n ( p r i n c i p l e s and expe r i ence ) ; and case d e s c r i p t i o n s .

1450. Holland, T . C. , "TESTING HIGH-STRENGTH CONCRETE," Concrete Cons t ruc t ion , V o l . 32, N o . 6, Jun 1987, pp. 534, 536.

Now h igh - s t r eng th c o n c r e t e i s ; widely used and d e s i g n e r s are i n c r e a s i n g l y speci-fying s t r e n g t h s exceeding 10,000 p s i . Because these c o n c r e t e s are used f o r c r i t i ca l s t r u c t u r a l appl ica t - ions , f a i l u r e t o reach the specified s t r e n g t h can cause c o s t l y d e l a y s w h i l e f u r t h e r t e s t i n g i s done. It 's e s p e c i a l l y impor tan t t o avo id low test r e s u l t s caused by i n c o r r e c t t e s t i n g procedures . P re l imina ry t e s t i n g o f h i g h - s t r e n g t h c o n c r e t e i s o f t e n done i n two phases: laboratory-made c o n c r e t e i s tested t o develop mixture p r o p o r t i o n s t h a t w i l l produce the desired s t r e n g t h ; and plant-mixed c o n c r e t e i s made t o ensu re t h a t large batches y i e l d t h e same test r e s u l t s as small hatches. The c o n c r e t e can be used i n n o n c r i t i c a l members such as f o o t i n g s . T h i s helps i d e n t i f y p o t e n t i a l problem areas i n c o n c r e t e product ion , sampling, and t e s t i n g .

1 4 5 1 . Holland, T . C. , l'WORKING WITH SILICA-FUME CONCRETE," Concrete Cons t ruc t ion , V o l . 32, No. 3, 1987, pp. 261, 263, 265-266.

Si l i ca fume produces c o n c r e t e t h a t is s t r o n g e r and more d u r a b l e t h a n convent iona l conc re t e . F i e ld s t r e n g t h s o f 1 4 , 0 0 0 p s i have been achieved w i t h t h i s h i g h l y reactive pozzolan. A l s o , rebar c o r r o s i o n i s reduced because t h e r e a c t i o n p roduc t s of t h e extremely f i n e s i l i c a fume par t ic les p l u g i n t e r n a l p o r e s . T h i s slows ca rbona t ion and h e l p s keep c h l o r i d e s o u t of t h e c o n c r e t e . Because o f these b e n e f i t s , many e n g i n e e r s are now s p e c i f y i n g s i l i ca - fume c o n c r e t e f o r high- s t r e n g t h s t r u c t u r a l a p p l i c a t i o n s , a b r a s i o n - r e s i s t a n t s u r f a c e s , and s t r u c t u r e s exposed t o d e i c i n g a g e n t s o r s a l t water.

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1452. Hol land , T . C. , "USING THE MATURITY METHOD TO PREDICT CONCRETE STRENGTH," C o n c r e t e C o n s t r u c t i o n , V o l . 32, No. 10, O c t 1987, pp. 867-869.

Describes t h e s t r e n g t h - m a t u r i t y r e l a t i o n s h i p i n c o n c r e t e and t h e r e c e n t l y a d o p t e d ASTM s t a n d a r d practice f o r e s t i m a t i n g c o n c r e t e s t r e n g t h by t h e m a t u r i t y method, which i s based on t h e t e m p e r a t u r e h i s t o r y o f t h e c o n c r e t e .

1 4 5 3 . Hover, K. C. , "CLOSING THE GAPS: HOW TO MAKE CONCRETE LESS PERMEABLE AND MORE DURABLE," C o n c r e t e C o n s t r u c t i o n , V o l . 32, No. 1 0 , O c t 1987, pp. 857-860.

Discusses p e r m e a b i l i t y v e r s u s d u r a b i l i t y o f c o n c r e t e . Water-cement r a t i o , c u r i n g , and a d m i x t u r e s are c i ted as major f a c t o r s i n f l u e n c i n g p e r m e a b i l i t y a n d d u r a b i l i t y , and p e r m e a b i l i t y is p roposed as a p o s s i b l e q u a l i t y - c o n t r o l parameter.

1 4 5 4 . J a n s s e n , D. J., "MOISTURE I N PORTLAND CEMENT CONCRETE, T r a n s p o r t a t i o n Research Record, N 1121, 1987, pp. 40-44.

P o r t l a n d cement c o n c r e t e s h r i n k s as it dries, and, i f t h i s s h r i n k a g e i s r e s t r a i n e d i n any way, t e n s i l e stresses w i l l d e v e l o p i n t h e c o n c r e t e . If t h e r e i s a m o i s t u r e g r a d i e n t i n t he c o n c r e t e , t he c o n c r e t e w i l l have a t e n d e n c y t o c u r l . The weight of t he c o n c r e t e t e n d s t o resist the c u r l i n g i n i n s t a l l a t i o n s s u c h as pavements , and t h i s leads t o c u r l i n g stresses. This h a s been r e c o g n i z e d i n pavements f o r many y e a r s . Normally m o i s t u r e g r a d i e n t c u r l i n g stresses i n pavements are i g n o r e d b e c a u s e o f t h e d i f f i c u l t y i n es t imat ing t h e i r magnitude and because it i s believed t h a t t h e y are c a n c e l l e d o u t by t h e effect o f t e m p e r a t u r e g r a d i e n t - i n d u c e d warping . I t i s t h e p u r p o s e o f t h i s paper t o estimate t h e magni tude and l o c a t i o n s of m o i s t u r e g r a d i e n t - i n d u c e d c u r l i n g stresses.

1455. Jerath, S. and Yamane, L . , "MECHANICAL PROPERTIES AND WORKABILITY OF SUPERPLASTICIZED CONCRETE," Cement, Concre t e , and Aggregates, V o l . 9, No. 1, Jun 1987, PP. 12-19.

I n t he d e s i g n o f c o n c r e t e s t r u c t u r e s , t he modulus of e l a s t i c i t y , t h e modulus of r u p t u r e , and the s p l i t c y l i n d e r t e n s i l e s t r e n g t h o f c o n c r e t e are predicted from i t s compress ive s t r e n t h . I n t h i s paper, t h e

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r e l a t i o n s h i p between compressive s t r e n g t h and o t h e r mechanical p r o p e r t i e s i s s t u d i e d f o r s u p e r p l a s t i c i z e d c o n c r e t e w i t h W-C r a t i o s of 0 .28 , 0.35, 0 . 4 5 , and 0.55. Also i n t h i s s tudy, t h e effect o f d i f f e r e n t dosages of a high-molecular-weight s u l f o n a t e d naphtha lene condensate s u p e r p l a s t i c i z e r known as Lomar-D on t h e compressive s t r e n g t h , s t r e s s - s t r a i n r e l a t i o n s h i p , modulus of e l a s t i c i t y , Po i s son ' s r a t i o , modulus of r u p t u r e , and s p l i t c y l i n d e r t e n s i l e s t r e n g t h of normal, medium, and h igh - s t r eng th c o n c r e t e mixes i s i n v e s t i g a e d . Overall, '72 c y l i n d e r s and 36 beams w e r e tested i n accordance w i t h ASTM s p e c i f i c a t i o n s . I n a d d i t i o n , the e f f e c t of d i f f e r e n t dosages of the s u p e r p l a s t i c i z e r on t h e w o r k a b i l i t y of d i f f e r e n t mixes and t h e slump loss w i t h t i m e w a s a l s o measured.

1456. John, R. and Shah, S. P . , "EFFECT O F H I G H STRENGTH AND

F r a c t u r e of Concrete and Rock: SEM-RILEM I n t e r n a t i o n a l Conference, Houston, TX, 1987, pp. 35-52.

RATE OF LOADING ON FRACTURE PARMTERS OF CONCRETE,"

Concrete w i t h compressive s t r e n g t h up t o 1 4 0 MPa ( 2 0 0 0 0 p s i ) can be now economical ly produced. For these high s t r e n g t h c o n c r e t e s i t has been shown t h a t one cannot u s e t h e same e m p i r i c a l r e l a t i o n s h i p s between compressive s t r e n g t h and o t h e r p r o p e r t i e s such as s p l i t c y l i n d e r s t r e n g t h , f l e x u r a l s t r e n g t h , shear s t r e n g t h and bond s t r e n g t h as t h a t c u r r e n t l y used, and d i f f e r e n t r e l a t i o n s h i p s f o r high s t r e n g t h c o n c r e t e have been proposed. I n t h i s paper a f racture mechanics based t h e o r e t i c a l model i s used t o p r e d i c t v a r i o u s expe r imen ta l ly observed t r e n d s f o r high s t r e n g t h c o n c r e t e . The s i z e independent f r a c t u r e parameters needed f o r t h i s model can be derived from a s i n g l e t es t . I t i s known t h a t an i n c r e a s e d load ing ra te increases t h e s t r e n g t h b u t reduces t he n o n l i n e a r i t y ( i n c r e a s e d ' b r i t t l e n e s s ' ) . T h i s s t r a i n r a t e s e n s i t i v i t y of f r a c t u r e s t r e n g t h of c o n c r e t e i s g e n e r a l l y lower f o r h igh s t r e n g t h c o n c r e t e . T h i s i n t e r a c t i o n between h igh s t r e n g t h c o n c r e t e and s t r a i n ra te and between t es t method and s i z e of t he specimen can be p r e d i c t e d u s i n g t h e f r a c t u r e mechanics approach proposed i n t h e paper .

1457. Johnston, C. and Mulhotra, V . , "HIGH-STRENGTH SEMI- LIGHTWEIGHT CONCRETE WITH U P TO 50% FLY ASH BY WEIGHT OF CEMENT," ASTM Cement Concrete and Aggregates, V o l . 9 NO. 2 , 1987, pp. 101-112.

The e f f e c t s are d i scussed of i n c l u d i n g a Western Canadian subbituminous f l y ash i n s u p e r p l a s t i c i z e d ,

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air-entrained, semi-lightweight concrete. Mixtures were proportioned with 100 +/- 20-mm slump and 5 +/- 1% air content. Cement contents ranged from 250 to 500 kg/m with additions of fly ash up to 50% by weight of cement. In the freshly mixed state, the effects of the fly ash are to reduce the initial water demand, increase the dosage of air-entraining admixture required for the specified air content, and reduce the rate of slump loss after addition of superplasticizer. The dosage of superplasticizer required remains essentially constant when expressed as a percentage of the total weight of binder (cement + fly ash). In the hardened state, the emphasis is on establishing how the proportion of fly ash to cement affects strength, unit weight, and cost. Each mixture is evaluated in terms of strength-weight ratio and cost in terms of cement equivalent in kg/m cubed, using the relationship between the costs of cement and fly ash locally to convert the cost of the fly ash into an equivalent cement cost.

1458. Katsaragakis, E. S., "NEW TENSILE TEST FOR CONCRETE," Materials and Structures, Research and Testing, Vol. 20, NO. 120, Nov 1987, pp. 463-466.

A new tensile test arrangement for concrete is presented, featuring a simple loading frame and an equally simple specimen shape.

1459. Kawamura, M. and Takemoto, K. et al., "EFFECTIVENESS OF VARIOUS SILICA FUMES IN PREVENTING ALKALI-SILICA EXPANSION," Concrete Durability. Katherine and Bryant Mather International Conference, Held at Atlanta, Georgia, USA, 27 April-May 1987, pp. 1809-19.

In order to utilize silica fume as a pozzolanic material for inhibiting alkali-silica expansion, the effect of various silica fumes on expansion of mortars containing beltane opal were investigated. Different silica fumes were found to vary widely in their effect on the expansion of mortars. The properties of silica fume affecting alkali-silica expansion were explored. Pozzolanic activity of silica fumes was evaluated by measuring the amounts of calcium hydroxide consumed by pozzolanic reaction in silica fume-bearing cement pastes. The amounts of calcium hydroxide in portland cement-silica fume mixtures were determined by dsc-tg analysis. Pore solutions obtained from mortars containing three different silica fumes were also analyzed. The silica fume with the highest pozzolanic activity was the most effective in reducing alkali- silica expansion of mortars. However, it was found

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t h a t r e d u c t i o n i n expansion by t.he a d d i t i o n o f s i l i c a fume w a s n o t n e c e s s a r i l y i n l i n e w i t h t h e amount of calcium hydroxide consumed as a whole. Although t h e c o n c e n t r a t i o n s af a l k a l i s and oh-ions i n t h e p o r e s o l u t i o n s i n mor ta rs were reduced t o t h e same level b y the a d d i t i o n o f three d i f f e r e n t s i l i c a fumes, t he r e d u c t i o n s i n expansions of t he three s i l i ca fumes- b e a r i n g mor t a r s were g r e a t l y d i f ' f e r en t from one ano the r .

1 4 6 0 . K i m , K . and M i l s t e i n , F., "RELATION BETWEEN HARDNESS AND COMPRESSIVE STRENGTH O F POLYMER CONCRETE, I'

Cons t ruc t ion and Bui ld ing Materi-als, V o l . 1, No. 4 , Dec 1987, pp. 209-214.

Experimental s t u d i e s w e r e made on the i n f l u e n c e of mixing and c a s t i n g t echn iques arid of c u r i n g t i m e upon t h e compressive s t r e n g t h and hardness o f m e t h y l methacrylate based polymer c o n c r e t e . T h e Rockwell K and F scales were found t o be s u i t a b l e f o r the ha rdness de t e rmina t ions . Over B w i d e range of hardness and s t r e n g t h va lues , the average compressive s t r e n g t h ( f**c) varied l i n e a r l y w i t h t h e average ha rdness (R**K) accord ing t o t h e r e l a t i o n ( f**c ) (ps i ) =560 (R**K) - 1 2 , 0 0 0 , i r r e s p e c t i v e o f c a s t i n g and c u r i n g variables. The weaker materials e x h i b i t e d greater v a r i a t i o n s i n hardness . Hardness t e s t i n g is found t o p rov ide a meaningful arid convenient method f o r e v a l u a t i n g t h e q u a l i t y o f polymer c o n c r e t e .

1 4 6 1 . Knutson, M. J. and Ri ley , R. C . , "CONCRETE PAVING H I T S THE FAST TRACK," Highway and Heavy Cons t ruc t ion , Vol. 130, No. 9, 1987, pp. 80-83.

High-production, heavy-duty pavement w i l l be most ly l i m i t e d t o a i r p o r t s , an occas iona l new freeway o r t u r n p i k e , and t o t h e r e c o n s t r u c t i o n of r u r a l I n t e r s t a t e s , o f t e n f e a t u r i n g mono l i th i c c o n c r e t e shou lde r s . The r e c o n s t r u c t i o n of urban f r eeways w i t h emphasis on coord ina t ion and schedu l ing i s fo reseen . T h e new marke t s i n t he c o n c r e t e paving f i e l d a r e : f a s t t r ack r e s u r f a c i n g w i t h ' t y p e 11:" high-early s t r e n g t h PC; c o n c r e t e pavement r e s t o r a t i o n ( C P R ) , now proven t o r e p a i r worn c o n c r e t e pavements w i t h a smooth-riding, s k i d - r e s i s t a n t s u r f a c e ; r e c y c l i n g c o n c r e t e as base s t o n e o r s p e c i f i c a t i o n aggregates when r e p l a c i n g pavements; and porous c o n c r e t e hase - a new idea f o r base c o n s t r u c t i o n .

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1462. Krenchel, H. and Bickley, J. A., "PULLOUT TESTING OF CONCRETE," Nordic Concrete Research, No. 6, Dec 1987, pp. 155-168.

A survey of the different pullout systems developed for controlling concrete strength with an examination of stress- and strain-distribution inside the concrete at peak load by the Scandinavian pullout testing system.

1463. Lane, D. and Meininger, R., "LABORATORY EVALUATION OF THE FREEZING AND THAWING DURABILITY OF MARINE LIMESTONE COARSE AGGREGATE IN CONCRETE.," Concrete Durability. Katherine and Bryant Mather International Conference, Atlanta, Georgia, USA, 27 April-May 1987, pp. 1311-23.

Air-entrained concretes were subjected to extended freezing-thawing tests to determine the durability of three porous marine limestone coarse aggregates. Control concretes were made with a non-porous limestone. Prior to mixing the concrete, the coarse aggregates were soaked for 24 hours. After initial curing, the specimens were placed in a standard moist room for 13 days until freezing tests began at 14 days age. Weight change, length change, and dynamic modulus of elasticity were monitored throughout the test. Specimens exposed to the freezing-in-air procedure were subjected to 1000 freezing-thawing cycles without showing significant deterioration. Except for the control group, a l l specimens subjected to the freezing-in-water procedure began to deteriorate between 250 and 350 cycles as indicated by increasing length and decreasing modulus of elasticity. Increasing weight of the water frozen specimens during the first 300 cycles was attributed to water absorption. Calculations suggest that the coarse aggregate in specimens frozen in water had reached 80 to 95 percent saturation when deterioration began. These results emphasize the critical role played by moisture content in determining the freezing-thawing durability of coarse aggregates and the need to develop better methods to evaluate saturation levels during testing with respect to in- place conditions.

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1 4 6 4 . Luong, M. P., "INFRARED THERMOGFMHY OF FRACTURE OF CONCRETE AND ROCK," F r a c t u r e o f Concrete and Rock: SEM-RILEM I n t e r n a t i o n a l Conference, Houston, TX, 1987, pp. 561-571.

I n f r a r e d thermography has been used as a n o n d e s t r u c t i v e and noncontact t echn ique t o examine the mechanical response o f c o n c r e t e and rock specimens s u b j e c t e d t o g iven s t a t i c unconffined compressions and t o a superimposed v i b r a t o r y exc i - t a t ion . The parameter i n v e s t i g a t e d i n t h i s paper i s the heat g e n e r a t i o n due t o energy d i s s i p a t i o n by t h e mat-erial which has been e x c i t e d beyond i t s s table reversible l i m i t . Th i s u s e f u l t echn ique a l lows a c c u r a t e i l l u s t r a t i o n of t he o n s e t o f u n s t a b l e crack propagat ion and/or f l a w coa lescence when i n c r e a s i n g irreversible microcracking i s g e n e r a t e d by v i b r a t o r y load ing .

1465. Maage, M. and Se l l evo ld , E. J., "EFFECT O F MICROSILICA ON THE DURABILITY OF CONCRETE STRUCTURES, I' Concrete I n t e r n a t i o n a l : Design C Construc:tion, V o l . 9, No. 12, D e c 1987, pp. 39-43.

Cores t a k e n from c o n c r e t e s t r u c t u r e s b o t h w i t h and wi thout m i c r o s i l i c a w e r e tested by mechanical and microscopic methods. R e s u l t s i n d i c a t e no s i g n i f i c a n t d e t r i m e n t a l changes i n long-term p r o p e r t i e s f o r c o n c r e t e c o n t a i n i n g m i c r o s i l i c a .

1466. Maage, M. and Johansen, R. , "PROPERTIES O F NORWEGIAN BLENDED CEMENTS WITH AND WITHOUT S I L I C A FUME," Nordic Concrete Research, N o . 6, 1987, pp. 179-197.

I n o r d e r t o save energy and r a w materials, NORCEM CEMENT i s producing cement (MP:30) where f l y a s h i s added i n the g r i n d i n g p rocess . The o b j e c t i v e o f t h i s research program has been t o document impor tan t p r o p e r t i e s f o r c o n c r e t e and cement paste of MP30 cements i n r e l a t i o n t o comparable mixes o f Ordinary P o r t l a n d Cement (P30). Also, t h e effect of s i l i c a fume should be documented. Concrete p r o p e r t i e s b o t h i n fresh s t a t e and i n green s t a t e w e r e tested a long w i t h long term d u r a b i l i t y p r o p e r t i e s . I n cement paste, chemical and d u r a b i l i t y aspects w e r e s t u d i e d .

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1467. Malhotra, V. M. and Painter, K. A. et al., "MECHANICAL PROPERTIES AND FREEZING AND THAWING RESISTANCE OF HIGH-STRENGTH CONCRETE INCORPORATING SILICA FUME," Cement, Concrete, and Aggregates, Vol. 9, No. 2, Winter 1987, pp. 65-79.

This report presents results of an investigation dealing with the mechanical properties and freezing and thawing resistance of high-strength, silica fume concrete using ASTM Test Method for Resistance of Concrete to Rapid Freezing and Thawing (C 666-84, Procedure A). Eighteen nonair-entrained and six air- entrained concrete mixtures, 0.06 (m**3) in size, were made. The water-to-(cement + silica fume) ratio (W/C + S) of the mixtures ranged from 0.25 to 0.36, and the percentages of cement replacement by silica fume were 0, 10, and 20 percent on a weight basis. Any loss in slump due to the use of silica fume was compensated for by the use of a superplasticizer. A number of test cylinders were made for testing in compression at various ages, and test prisms were cast for determining their resistance to repeated cycles of freezing and thawing in accordance with ASTM C 666, Procedure A. Sawn sections of some of the prisms were used for determining the air void parameters of the hardened concrete. Nonair-entrained, high-strength concrete with a compressive strength of up to 87 MPa at 28 days, regardless of the W/C + S and irrespective of the silica fume content used, had durability factors less than 12 when tested in accordance with ASTM C 666, Procedure A. Also, air-entrained concrete prisms incorporating 10 and 20 percent silica fume as replacement for cement failed to complete 300 cycles of freezing and thawing.

1468. Malhotra, V. and Painter, K. et al., "MECHANICAL PROPERTIES AND FREEZING AND THAWING RESISTANCE OF HIGH-STRENGTH CONCRETE INCORPORATING SILICA FUME," ASTM Cement Concrete and Aggregates, Vol. 9, No. 2, 1987, pp. 65-79.

This report presents results of an investigation dealing with the mechanical properties and freezing and thawing resistance of high-strength, silica fume concrete using ASTM Test Method for Resistance of Concrete to Rapid Freezing and Thawing (C 666-84, Procedure A). Eighteen nonair-entrained and 6 air- entrained concrete mixtures, 0.06 m cubed in size, were made. The water-to-cement (cement + silica fume) ratio (W/C + S) of the mixtures ranged from 0.25 to 0.36, and the percentages of cement replacement by silica fume were 0, 10, and 20% on a weight basis.

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Any loss in slump due to the use of silica fume was compensated for by the use of a superplasticizer. A number of test cylinders were made for testing in compression at various ages, anti test prisms were cast for determining their resistance to repeated cycles of freezing and thawing in accordance with ASTM C 666, Procedure A. Sawn sections of some of the prisms were used for determining the air vofid parameters of the hardened concrete. Nonair-entrained, high-strength concrete with a compressive strength of up to 87 MPa at 28 days, regardless of the W,/C +. S and irrespective of the silica fume content used,, had durability factors less than 12 when tested in accordance with ASTM 666, Procedure A. Also, air-entrained concrete prisms incorporating 10 and 20 %- silica fume as replacement for cement failed to complete 300 cycles of freezing and thawing.

1469. Malhotra, V. and Ramachandra, V. et al., "CONDENSED SILICA FUME IN CONCRETE, 'I CRC Press Incorporated, 1987, pp. 240.

A balanced view is presented of the effect of condensed silica fume on the physical, chemical, mechanical, and durability aspects with respect to cement pase, mortar and concrete. It discusses the nature and types of condensed s.ilica fume, physical characteristics, product variation and problems involved in its handling and transportation. The book covers the hydration and microstructural changes occuring in cement paste, the effect of silica fume on the physical properties of mortar, and its influence on the aggregate-cement paste interface. The properties of fresh and hardened concrete containing superplasticizers are covered, ,as well as fly ash and blast furnace slag, and the durability of silica fume concrete. The applications and curent standards, and the health and environmental hazards are also considered.

1470. Marusin, S., "IMPROVEMENT OF CONCRETE DURABILITY AGAINST INTRUSION OF CHLORIDE-LADEN WATER BY USING SEALERS, COATINGS AND VARIOUS ADMIXTURES.," Concrete Durability. Katherine and Bryant Mather International Conference, Atlanta, Georgia, USA, 27 April-May 1987, pp. 599-619.

This paper summarizes the research which has been undertaken at wiss, janney, elstner associates, inc (wje) since 1979 on sealers, coatings and concrete containing admixtures. The research used a test procedure developed during the national cooperative

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highway research program (NCHRP) project 12-19a 'concrete sealers for protection of bridge structures' which was reported in 1981 in the NCHRP report no 244. This test method uses 10-cm-cube specimens and water absorption and chloride ion penetration is determined after 21 days exposure to 15% nacl solution. The study focuses on the minimization of the ingress of chloride-laden water into concrete, the influence of w/c ratio, the relationship between water absorption and chloride ion content in concrete, and the comparison of the chloride distribution profiles through the conventional portland cement concrete and concrete containing various admixtures (superplasticizers, polymer emulsions, condensed silica fume).

1471. Matsufuji, Y. and Ohkubo, T., "ESTIMATING METHOD OF FATIGUE STRENGTH OF THE BRITTLE MATERIALS UNDER REPEATED IMPULSIVE BENDING LOAD," Fracture of Concrete and Rock: SEM-RILEM International Conference, Houston, TX, 1987, pp. 102-111.

In the case that reinforced concrete structures are subjected to repeated impulsive bending load, it is important to clarify the fatigue strength and the fatigue life of R/C members under repeated impulsive bending load. In this paper, a method estimating the fatigue life of the brittle materials, such as concrete and rock, is shown on the basis of the test results of cement-mortar beams under repeated impulsive bending load.

1472. Morris, M., "SOME OF THE APPLICATIONS FOR POLYMER GRIDS IN CONCRETE," Concrete (London), Vol. 21, No. 2, 1987, pp. 25-26.

In addition to the rapid growth Tensar high strength polymer grids have enjoyed in soil stabilisation, earth reinforcement and asphalt paving, they are now being widely used in an extensive range of concrete applications. Innovative design methods have led to the use of polymer grids to distribute stresses and control cracking in the continuous casting of jointless floors and other types of concrete paving. The crack control properties have also allowed the grids to be used extensively in a wide range of linings and coatings on coastal sites and in tunnels and sewers. A three-and-a-half year programme of research was undertaken at Sheffield to investigate the behaviour of concrete incorporating polymer grids using various methods of stress application to composite panels under both static and

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dynamic l o a d i n g . P o s i t i v e r e s u l t s o b t a i n e d from t h i s work w e r e u s e d t o create a programme o f a p p l i c a t i o n development .

1 4 7 3 . Murray, A. M. and Long, A. E . , "'STUDY OF THE I N SITU VARIABILITY OF CONCRETE USING TE[E PULL-OFF METHOD, P r o c e e d i n g s , I n s t i t u t i o n o f C i v i . l E n g i n e e r s (London) , Vol . 83, P a r t 2 , Dec 1987, pp. 731-745.

The a l l o w a n c e f o r c o n c r e t e v a r i a b i l i t y i n r e i n f o r c e d c o n c r e t e d e s i g n from s p e c i f i c a t i o n s CP 1 1 0 and BS 8110 i s d i s c u s s e d , and p r e v i o u s r e s e a r c h i s b r i e f l y reviewed. T h i s paper describes a program of p a r t i a l l y d e s t r u c t i v e i n s i t u tests on a m u l t i s t o r y car p a r k t o d e t e r m i n e t h e c o n c r e t e s t r e n g t h s and v a r i a b i l i t y i n t h a t s t r u c t u r e arid i n c l u d e s a de ta i led a n a l y s i s o f the r e s u l t s . T h i s i n f o r m a t i o n i s t h e n u s e d t o assess t h e adequacy o f t h e p a r t i a l s a f e t y f a c t o r f o r c o n c r e t e s t r e n g t h a t t he u l t i m a t e l i m i t s tate.

1 4 7 4 . Nagataki, S. and S a k a i , E . , "PROPERTIES O F ULTRA-HIGH STRENGTH CONCRETE," Concre t e J o u r n a l , V o l . 25, No. 8, Aug 1987, pp. 15-23.

T h e d e n s i f i e d sys t em c o n t a i n i n g homogeneously a r r a n g e d u l t r a - f i n e pa r t i c l e (DSP) has been deve loped as a u l t r a - h i g h - s t r e n g t h c o n c r e t e . T h i s mater ia l c o n s i s t s of cement, u l t r a - f i n e par t ic les s u c h as s i l i c a fume, and a large q u a n t i t y o f s u p e r p l a s t i c i z e r s . I t a l l o w s a large water r e d u c t i o n t o o b t a i n u l t r a - h i g h s t r e n g t h arid y e t a c h i e v e s a good f l u i d i t y o f c o n c r e t e f o r c a s t i n g . I n t h i s r e p o r t , t h e mechan ica l p r o p e r t i e s o f DSP c o n c r e t e and t h e ha rdened mechanism o r morphology o f DSP rnaterials are e x p l a i n e d . I n a d d i t i o n , some a p p l i c a t i o n s o f DSP f o r b u i l d i n g materials and i n d u s t r i a l materials are i n t r o d u c e d .

1475. Nawy, E. G . e t a l . , "EARLY STRENGTH O F CONCRETE PATCHING MATERIALS AT LOW TEMPERATURES, I'

T r a n s p o r t a t i o n Research Board, Sep 1987, pp. 11.

Win te r repair and main tenance o p e r a t i o n s o f c o n c r e t e bridge decks and pavement r e q u i r e high e a r l y s t r e n g t h p a t c h i n g materials s u i t a b l e f o r a p p l i c a t i o n a t s u b f r e e z i n g t e m p e r a t u r e s . An e x t e n s i v e e x p e r i m e n t a l program a t R u t g e r s U n i v e r s i t y has i d e n t i f i e d f o u r g e n e r i c materia:Ls as p o t e n t i a l l y s u i t a b l e t o f u l f i l l t h i s r o l e . E a r l y s t r e n g t h tests i n c l u d e d compress ive c y l i n d e r s t r e n g t h of p a t c h i n g

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material and s l a n t shear bond s t r e n g t h t o e x i s t i n g c o n c r e t e a t 1 day and 7 days, and s t a t i c and f a t i g u e f l e x u r e s t r e n g t h of pa tched specimens a t 7 days . All p a t c h materials were cast and cured a t t empera tu res of 15 deg F t o 20 deg F. The fou r g e n e r i c a l l y d i s t i n c t materials w e r e : (a) a methyl methacrylate-based material , (b) two t y p e s of magnesium phosphate-based materials, and (c) a polyure thane b inde r . E a r l y s t r e n g t h s ranged from 1700 p s i t o more t h a n 8000 ps i . S l a n t s h e a r bond s t r e n g t h s ranged from 2000 p s i t o more t h a n 5 0 0 0 ps i . F l e x u r a l s t r e n g t h s , bo th i n s t a t i c and f a t i g u e loading , a r e a l s o s u i t a b l e , w i th most materials d i s p l a y i n g performance comparable t o t h a t o f t h e c o n t r o l (unpatched) specimens. F l exure t e s t r e s u l t s , however, are h igh ly variable. The causes o f t h i s v a r i a b i l i t y and ways of reducing it need f u r t h e r i n v e s t i g a t i o n . This paper appeared i n T r a n s p o r t a t i o n Research Record No. 1 1 1 0 , Concrete and Concre te Cons t ruc t ion .

1476. Nawy, E. and Hanaor, A. e t a l . , "EARLY STRENGTH O F CONCRETE PATCHING MATERIALS AT LOW TEMPERATURES," T r a n s p o r t a t i o n Research Record, N1110, 1987, pp. 24- 34.

Winter r e p a i r and maintenance o p e r a t i o n s o f c o n c r e t e bridge decks and pavement r e q u i r e high e a r l y s t r e n g t h p a t c h i n g m a t e r i a l s s u i t a b l e f o r a p p l i c a t i o n a t s u b f r e e z i n g tempera tures . An e x t e n s i v e exper imenta l program a t Rutgers Un ive r s i ty has i d e n t i f i e d f o u r g e n e r i c materials as p o t e n t i a l l y s u i t a b l e t o f u l f i l t h i s r o l e . E a r l y s t r e n g t h tes ts inc luded compressive c y l i n d e r s t r e n g t h of p a t c h i n g material and s l a n t s h e a r bond s t r e n g t h t o e x i s t i n g c o n c r e t e a t 1 day and 7 days, and s t a t i c and f a t i g u e f l e x u r e s t r e n g t h of patched specimens a t 7 days. A l l p a t c h materials were cast and cured a t t empera tu res of 15 deg F t o 20 deg F. The f o u r g e n e r i c a l l y d i s t i n c t materials i d e n t i f i e d were: (a) a methyl methacry la te - based material, (b) two t y p e s o f magnesium phosphate- based materials, and (c) a polyure thane b i n d e r . E a r l y s t r e n g t h s ranged from 1 , 7 0 0 p s i t o more t h a n 8,000 p s i . S l a n t s h e a r bond s t r e n g t h s ranged from 2,000 psi t o more t h a n 5 , 0 0 0 p s i . F l e x u r a l s t r e n g t h s , b o t h i n s t a t i c and f a t i g u e loading, a r e a l s o s u i t a b l e , w i t h most materials d i s p l a y i n g performance comparable t o t h a t of t he c o n t r o l (unpatched) specimens. F l exure tes t r e s u l t s , however, a r e h ighly variable. T h e causes of t h i s v a r i a b i l i t y and ways of reducing it need f u r t h e r i n v e s t i g a t i o n .

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1477. Neville, A. , "WHY W E HAVE CONCRETE DURABILITY PROBLEMS.," Concrete Durability. Katherine and Bryant Mather International Conference, Atlanta, Georgia, USA, 27 April-May 1987, pp. 21-30.

The paper draws attention to some early papers by both the mathers of particular and lasting significance. Three factors relevant to so many current problems with durability of concrete are reviewed. First, inadequate criteria for acceptance of concrete, strength alone being relied upon in the past. Second, changes in cement properties over the years, which allowed the use of leaner mixes for a given specified strength. The third factor is the corrosion of steel in the concretes used nowadays, particularly severe in hot climates. Finally, recommendations are made for more attention to the composition of the mix and for inspection and maintenance of concrete structures.

1478. Oh, B., "BEHAVIOR OF CONCRETE UNDER DYNAMIC TENSILE LOADS," Journal of American Concrete Institute, Vol. 84, No. 1, Jan 1987, pp. 8-13.

A realistic nonlinear stress-strain model that can describe the dynamic tensile beh.avior of concrete is presented. The model is obtained by generalizing rate-independent nonlinear tensile stress-strain relations for concete. The stat.ic tensile behavior of concrete is modeled on the basis; of the concept of microcrack planes. The ine1asti.c phenomena such as microcracking occur predominant1.y on certain weak planes within the material. The orientations of these weak planes are considered to be uniformly distributed in the concrete. The model based on this concept describes well the static tensile test results of concrete. The affinity transfornlations are employed to model the effect of strain rate. The material parameters are characterized in terms of the strain rate magnitude. The present theory, which can model the dynamic tensile behavior of concrete, is compared with the dynamic tensile test data available in the literature. An equation is proposed to predict the increase of tensile strength due to an increase of strain rate. It is found that t.he effect of strain rate is more sensitive in tension than in compression. The model describes adequately the dynamic tensile behavior of concrete and allows more realistic dynamic analysis of concrete structures.

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1479. Ohama, Y., "PRINCIPLE OF LATEX MODIFICATION AND SOME TYPICAL PROPERTIES OF LATEX-MODIFIED MORTARS AND

Vol. 84, NO. 6, NOV 1987, pp. 511-518. CONCRETES," Journal of American Concrete Institute,

Latex-modified mortars and concretes employing various polymer latexes have been developed actively for more than 60 years and widely used as construction materials because of their good performance-cost ratio. This paper reviews the principle of latex modification in the process technology of latex- modified mortars and concretes and discusses their typical properties. Such properties are mainly characterized by a polymer-cement comatrix they form. The formation process of the comatrix is explained by a 3-step, simplified model. The possibility of some reactions between polymers, cement and aggregates is also discussed. The author proposes a binder-void ratio law for the strength predicton of the latex- modified mortars and concretes, which expands Talbot's void theory. The reviewed typical properties of hardened latex-modified mortars and concretes include strength, adhesion, pore structure, impermeability, and durability (freeze-thaw resistance, chloride penetration resistance, carbonation resistance and weatherability). In general, these properties are strongly affected by the polymer-cement ratio.

1480. Okamoto, H., "STUDY ON CREEP PROPERTIES OF CONCRETE AT VERY EARLY AGE," Proceedings of the Thirtieth Japan Congress on Materials Research, 1987, pp. 171-174.

The present study has been carried out to make it clear that creep behavior on concrete at 2 to 7 hours after placing is examined by varying ratio of loading stress, and the constitutive equation is investigated by applying rheological models to experimental results. Taking up rheological models, we examined the fittness of three-element model and four-element model.

1481. Ozyildirim, C., "LABORATORY INVESTIGATION OF CONCRETE CONTAINING SILICA FUME FOR USE IN OVERLAYS," Journal of American Concrete Institute, Vol. 84 , No. 1, Jan 1987, pp. 3 - 7 .

Hydraulic cement concretes containing silica fume were batched and tested in the laboratory to assess their suitability for use in overlays having a minimum thickness of 1/4 in. (32 m m ) . Tests were made for

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s t r e n g t h , pe rmeab i l i t y , and freeze-thaw r e s i s t a n c e , and t h e characterist ics o f a i r v o i d s i n t h e hardened c o n c r e t e w e r e determined by p e t r o g r a p h i c examinat ion. Concre tes made w i t h s i l i c a fume from two sources a t a cement replacement ra te o f 5 p e r c e n t by weight and w i t h a water-cement r a t i o o f 0 . 4 0 o r lower y i e l d e d t h e p r o p e r t i e s desired f o r t h i n ove r l ays . I t i s t h u s expec ted t h a t c o n c r e t e s made w i t h s i l i c a fume can p rov ide a c o s t - e f f e c t i v e p r o t e c t i o n .

1482. P e r d i k a r i s , P . C. and Calomino, A. M . , "KINETICS OF CRACK GROWTH I N PLAIN CONCRETE," F r a c t u r e of Concrete and Rock: SEM-RILEM I n t e r n a t i o n a l Conference, 1987, pp. 96-101.

The number o f l o a d c y c l e s , N,, load-poin t d i sp lacement (LPD) and crack-mouth-opening d isp lacement (CMOD) compliance were measured i n a series of f a t i g u e tests on s ingle-edge-notched c o n c r e t e beams (SENB) under 4-point bending t o i n v e s t i g a t e t h e k i n e t i c s o f crack p ropaga t ion i n p l a i n c o n c r e t e . T h e prenotched beams were s u b j e c t e d t o e i ther a c o n s t a n t o r v a r i a b l e p u l s a t i n g l o a d up t o a maximum l o a d level of about 75% of t h e s t a t i c u l t i m a t e s t r e n g t h . Typ ica l ly , t h e crack growth ra te , d L-SCRIPT / d N decreased f o r t h e f i r s t 8 mn of crack e x t e n s i o n . T h e crack growth rate and the s t r a i n energy release rate , G//I, are p l o t t e d v e r s u s t h e crack l e n g t h t o beam depth r a t i o , which i s dete.rmined from t h e CMOD compliance measurements. The crack speed varied cons ide rab ly along t h e c rack p a t h b u t i n c r e a s i n g s t r a i n energy release rates produced on t h e average an i n c r e a s e i n t h e c rack speed. F i n a l l y , k i n e t i c data from t h r e e beams s u b j e c t e d t o a c o n s t a n t ampl i tude r e p e a t e d load ing i s compared t o t h e P a r i s model.

1483. P e s s i k i , S. P . and Carino, N. J . , "MEASUREMENT OF THE SETTING TIME AND STRENGTH OF CO'NCRETE BY THE IMPACT- ECHO METHOD," Report No. NBSIR 87-3575, U . S . Department of Commerce, Na t iona l Bureau of S tandards , a, 1987, pp. 121 .

T e s t s w e r e performed t o evaluate t h e f e a s i b i l i t y of u s i n g t h e impact-echo method t o de te rmine s e t t i n g t i m e and monitor s t r e n g t h development of c o n c r e t e . I n t he impact-echo method, the tes t o b j e c t i s s u b j e c t e d t o p o i n t impact and t h e s u r f a c e displacement a d j a c e n t t o t h e impact p o i n t i s monitored. From t h e measured d isp lacement waveform and the t .h ickness of t h e o b j e c t , t h e P-wave v e l o c i t y i s determined. Changes i n t h e P- wave v e l o c i t y w i t h t i m e reveal informat ion about t h e development of mechanical p r o p e r t i e s . S e t t i n g t i m e

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tests were made on concrete mixtures of two water- cement ratios and with and without set-controlling admixtures. A strong correlation was found between the time of initial setting of mortars sieved from the concrete, as determined by penetration resistance (ASTM C 403), and the time when the P-wave velocity began to increase. Two approaches for using the impact-echo method to define the setting time of concrete are presented. Tests were performed to examine the relationship between P-wave velocity, as determined by the impact-echo method, and the compressive strength of concrete. At early ages (up to about three days at standard temperature), the relationship was independent of curing temperature and water-cement ratio. It is concluded that the impact- echo method is a promising technique for nondestructively monitoring the development of mechanical properties in concrete from initial setting to ages of several days.

1484. Petroski, H. J. and Ojdrovic, R. P., "CONCRETE CYLINDER: STRESS ANALYSIS AND FAILURE MODES," International Journal of Fracture, Vol. 34 , No. 4 , 1987, pp. 263-279.

The rationale for using the circular cylindrical specimen for determining the tensile strength of concrete is reviewed, and the stress fields and fracture modes associated with the familiar splitting test and a pressurized cylinder test are discussed. The effect of a macrocrack on the stress field within a cylinder is introduced as a means of understanding the progressive fracture of a cylindrical specimen. In particular, it is argued that, while the idealized stress field in an unflawed cylinder may explain how and where the first macrocrack develops in a cylindrical specimen, it is the stress field modified by the presence of the macrocrack that must be considered to understand subsequent behavior. The axial tensile failure of a concrete cylinder loaded by radial pressure is also considered in the context of classical elastic stress analysis. We demonstrate that the induced tensile stress field is indeed of sufficient magnitude to explain the axial failure under radial pressure by an elementary strength of materials argument.

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1485. Pfeifer, D. and Landgren, J. et al., "PROTECTIVE SYSTEMS FOR NEW PRESTRESSED AND SUBSTRUCTURE CONCRETE.," Final Report, Apr 1987, pp. 1.33.

A three-year corrosion research project on 11 corrosion protection systems was undertaken in two laboratory studies. A total of 124 small reinforced concrete slabs were subjected to a 48-week, cyclic wet and dry saltwater exposure in the first study. The second year-long study dealt with cyclic saltwater exposure on 19 full-size sections of reinforced concrete columns and beams and precast, prestressed piles and stay-in-place bridge deck panels. The slab tests evaluated concrete having w/c ratios of 0.51, 0.40, and 0.28 with clear cover of 1, 2, and 3 in. The reinforcing steels evaluated were normal gray bars, normal prestressing strands, galvanized bars, and fusion-bonded epoxy-coated bars and prestressing strands. A calcium nitrite corrosion-inhibiting admixture for fresh concrete was evaluated. A penetrating silane sealer and methacrylate coating system were evaluated as surface treatments for hardened concrete. The full-size member tests included most of the above materials in concrete at a constant w/c ratio of 0.44, generally with 1-in. cover. A concrete containing a silica fume admixture was also evaluated in the full-size member tests. The full-size columns and beams were moist cured while the precast, prestressed piles and bridge deck panels were heat cured overnight at 130 to 140 deg F. Corrosion- related measurements included monitoring macrocell corrosion current and instant-off voltage between corroding and noncorroding reinforcement, half-cell potentials, chloride contents at the initiation of corrosion and at the conclusion of the test cycle, and measurement of the corroded areas on the reinforcement. The measured corrosion activity of these numerous specimens is presented and comparisons are made in their corrosion protection performance. Of particular significance were the beneficial influence of low w/c ratios and adequate concrete cover in reducing corrosion and chloride penetration. The silane sealer and the silica fume pozzolanic admixture concrete both dramatically reduced chloride penetration and the reinforcement did not develop corrosion. Epoxy-coated reinforcing bars and prestressing strands were not ccrroded in these tests, even though surrounding concrete had high chloride contents. Galvanized reinforcerent embedded in conventional concrete and bare reinforcement embedded in concrete made with the calcuim nitrite corrosion inhibitor both developed a low level of corrosion when surrounding concrete had ?igh chloride contents.

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Design considerations are suggested for these different corrosion protection materials to provide for greater corrosion protection for new cast-in-place reinforced concrete and precast, prestressed concrete bridge members.

1486. Philleo, R., "FROST SUSCEPTIBILITY OF HIGH-STRENGTH CONCRETE.," Concrete durability. Katherine and Bryant Mather International Conference, Atlanta, Georgia, USA, 27 April-May 1987, pp. 819-842.

Recent developments have made a new generation of high-strength concrete a viable material for routine construction. The two principal developments are high-range water-reducing admixtures, which permit the placement of concrete of very low water-cement ratio, and silica fume, a pozzolan of extremely high fineness. There are those who argue that high- strength concrete is of such a quality that entrained air is unnecessary. The resistance to freezing is directly dependent on the concrete's capacity for and its probability of containing freezable water. Concretes of very low water-cement ratio may have no capacity for freezable water if ambient conditions permit continuous hydration for a long period of time so that all the available space is filled with hydration products; or, short of complete space- filling, they may become so impermeable that saturation by water is unlikely in most natural exposures. High-range water-reducing admixtures do not alter the pore structure of cement paste; they merely extend traditional cement technology into a range of low water-cement ratios that were previously impractical. The addition of silica fume does alter the pore structure and places more of the pore volume in pores that are so small that water cannot freeze in them at ordinary atmospheric temperatures. It offers some hope of achieving frost resistance without entrained air. The normal test for evaluating frost resistance, ASTM c 666, exposes specimens to freezing at an intermediate level of maturity with no opportunity for drying by loss of water to the surroundings prior to test and exposes them to a very rapid freezing cycle. High-strength specimens without entrained air that may ultimately become durable cannot be expected to do well in the test. While the test is excellent for assessing the frost resistance of young saturated specimens to severe exposure, the resistance of mature specimens to more typical exposures might better be assessed by altering the age-at-test and specimen-conditioning requirements in C 666 or by replacing it with a critical dilation test such as ASTM c 671.

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1487. P i a s t a , J. and P i a s t a , W . e t a l . , "SULFATE RESISTANCE OF MORTARS AND CONCRETES WITH CALCIFEROUS AGGREGATES.," C o n c r e t e D u r a b i l i t y . K a t h e r i n e and Bryan t Mather I n t e r n a t i o n a l Conference , A t l a n t a , Georg ia , USA, 27 April-May, 1987, pp. 2153-70.

T h e i n v e s t i g a t i o n w a s carried o u t i n o r d e r t o e x p l a i n the effect o f t he t y p e o f aggregate on t h e s u l f a t e r e s i s t a n c e o f c o n c r e t e s and m o r t a r s . T h e c o n c r e t e s t u d i e d c o n t a i n e d t h e f o l l o w i n g c r u s h e d c o a r s e (2-20 mm) aggregates: po rous l i m e s t o n e ( p o r o s i t y 36%) d e n s e l i m e s t o n e ( p o r o s i t y 5.5%) a n d g r a n i t e and m o r t a r s w i t h t he same c a l c i f e r o u s aggregates (0-2 mm) and q u a r t z s a n d (0-2 m m ) . T h e r e s u l t s o f t he i n v e s t i g a t i o n showed t h a t t he s u l f a t e r e s i s t a n c e o f c o n c r e t e s w a s d i f f e r e n t a c c o r d i n g t o t h e aggregate used; however, t he d u r a b i l i t y o f c o n c r e t e w i t h t h e p o r o u s c a l c i f e r o u s aggregate w a s much better t h a n e x p e c t e d i n spite o f i t s v e r y high p o r o s i t y ( 3 6 % ) . I t w a s a l s o found t h a t m o r t a r s w i t h t h e porous aggregate had a higher r e s i s t a n c e t h a n c o n c r e t e s c o n t a i n i n g t ha t aggregate. G e n e r a l l y , cement w i t h f l y a s h r ep lacemen t had a h i g h e r r e s i s t a n c e t h a n o r d i n a r y p o r t l a n d cement . (TRRL)

1488. P igeon, M. and Gagne, R. e t a l . , "CRITICAL AIR-VOID SPACING FACTORS FOR LOW WATER-CEMENT RATIO CONCRETES WITH AND WITHOUT CONDENSED S I L I C A FUME, 'I Cement and C o n c r e t e Resea rch , Vo1.17, No.6, Nov 1987, pp. 896- 906.

I n t h i s paper, t h e r e s u l t s o f a f irst series of tests carried o u t a t Lava1 U n i v e r s i t y t o assess the i n f l u e n c e o f t h e decrease o f t h e water-cement r a t i o 011 f r e e z e - t h a w d u r a b i l i t y are r e p o r t e d . C o n c r e t e s made w i t h normal P o r t l a n d cement as w e l l as c o n c r e t e s c o n t a i n i n g condensed s i l i c a fume (CSF) w e r e tested, b e c a u s e the u s e of CSF is f a i r l y common i n h i g h s t r e n g t h c o n c r e t e .

1489. P igeon, M. and A i t c i n , P.-C. e t a l . , "COMPARATIVE STUDY OF THE AIR-VOID STABILITY I N A NORMAL AND A CONDENSED SILICA FUME FIELD CONCRETE," A C I Materials J o u r n a l , Vol . 84, No. 3 , May 1987, pp. 194-199.

Very l i t t l e re l iable d a t a e x i s t c o n c e r n i n g t h e d u r a b i l i t y o f f i e l d - c o n d e n s e d s i l i c a fume (CSF) c o n c r e t e exposed i n service t o f r e e z i n g and thawing i n the p r e s e n c e o f d e i c i n g s a l t s . T h e data available i n d i c a t e t h a t CSF c o n c r e t e w i t h o u t t he r i g h t bubb le -

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spacing factor performs very poorly, but with the correct spacing factor, it performs satisfactorily in similar climatic conditions. This paper reports the findings of a research program studying freeze-thaw durability and the stability of the air void system in a specific CSF mix from batching through placement. Additional test data show shrinkage and compressive strengths. With proper mixing and placing techniques, the air-void system of VSF concrete was found to be as stable as that of normal concrete. The proper spacing factor was obtained without any problem, and freeze- thaw tests confirmed the durability of the CSF concrete.

1490. Pitt, J. and Schluter, M. et al., "SULFATE IMPURITIES FROM DEICING SALT AND DURABILITY OF PORTLAND CEMENT MORTAR, Transportation Research Record, N1110, 1987, pp. 16-23.

Research on the topic of calcium sulfate impurities in deicing salts adversely affecting the durability of portland cement mortar is covered in this paper. Natural rock salt may contain as much as 4.0 percent calcium sulfate. When combined with chloride solutions the solubility of calcium sulfate increases by as much as 3 . 5 times; hence, the calcium sulfate impurities contained in rock salt brine become highly detrimental, causing attack on cement mortar samples. These impurities can collect in pavement joints and cracks, reaching high concentrations through evaporation and the repeated use of deicing salts. Such a destructive mechanism may account for premature field failure of pavements that passed durability tests in the laboratory. Durability studies using brines containing differing amounts of gypsum in proportion to the sulfates occurring in natural rock salts have been conducted. To model field conditions, samples were concurrently subjected to brines and rapid freeze-thaw testing. Deterioration proved so rapid that testing was stopped at 88 cycles. Tensile tests showed strength losses up to 40 percent for samples subjected to brine solutions containing gypsum impurities. Mercury intrusion porosimetry showed significant losses in pore volume for the treated samples as compared to samples frozen and thawed in water only. X-ray diffraction tests discovered increased amounts of ettringite and Friedel's salt, a tricalcium aluminate chloride hydrate.

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1 4 9 1 . Poon, C. S. and Wassell, L,. E. e t a l , , , "HIGH STRENGTH REFRACTORY ALUMINOUS CEMENT, 'I B r C e r a m Trans J, Vol. 86, No. 2, Mar-Apr 1987,

The performance of t h e macro-defect-free cement fDr r e f r a c t o r y purposes when compared t o t he normal f i r ed cast cement has been s t u d i e d . R e s u l t s show t h a t much improvement i n s t r e n g t h a f t e r f i r i n g i s achieved through the c l o s e packed green body of t h e macro- defect-free system, showir-g improved m i c r o s t r u c t u r e a f t e r f i r i n g . F u r t h e r i n c r e a s e i n s t r e n g t h can be achieved by u s i n g t h e very f i n e and active p a r t i c l e s r e s u l t i n g from the dehydra t ion o f t h e h y d r a t i o n p roduc t s of t h e normal aluminous cement t o form t h e i n i t i a l g reen body.

1 4 9 2 . Popovics, S. and Rajendran, N . e t a l . , " R A P I D HARDENING CEMENTS FOR REPAIR OF CONCRETE," A C I Material Jou rna l , Vo1.84, No.1, 1987, pp. 64-73.

This paper p r e s e n t s t h e r e s u l t s of an i n v e s t i g a t i o n on ve ry r a p i d l y hardening cements. Rapid hardening cements are t h o s e t h a t can develop several thousand p s i compressive s t r e n g t h w i t h i n a f e w hours . S ince t h e s e cements were developed j u s t r e c e n t l y , v e r y l i t t l e l a b o r a t o r y and even less p r a c t i c a l expe r i ence have been ob ta ined w i t h them. Th.erefore, t h i s paper p r e s e n t s t h e r e s u l t s o f a l a b o r a t o r y i n v e s t i g a t i o n on f o u r such cements. These cements are: 1. magnesium phosphate cement f o r c o l d and r e g u l a r weather u s e ( M P C ) ; 2 . magnesium phosphate cement f o r h o t weather u s e (MPH) ; 3 . aluminum phosphate cement (MAP) ; and 4 . r e g u l a t e d set cement ( R S ) . T h e p r e s e n t e d i n v e s t i g a t i o n c o n c e n t r a t e s on the s t r e n g t h development a t e a r l y ages.

1493. R i l ey , R. C . , ""FAST TRACK" OVERLAYS OPEN DOORS FOR CONCRETE," Roads and Bridges, V c l . 25, N o . 7, Jul 1987, pp. 39-40.

The c o n c r e t e i n d u s t r y has t u r n e d i t s s i g h t s t o h igh e a r l y s t r e n g t h mixes and new equipment f o r c o n c r e t e s u r f a c i n g .

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1494. Rjegovic, D. and Mikulis, D. et al., "THEORETICAL ASPECTS AND METHODS OF TESTING CONCRETE RESISTANCE TO FREEZING AND DEICING CHEMICALS.," Concrete Durability. Katherine and Bryant Mather International Conference, Atlanta, Georgia, USA, 27 April-May 1987, pp. 947-971.

Theoretical aspects of concrete resistance to freezing and deicing chemicals are shown in causal terms. Different constituents and concreting procedures result in different concretes. Furthermore, environmental influences cause a series of physical processes which are also presented in the paper. These physical mechanisms cause stresses which may result in concrete damages. The second part of the paper contains a survey of methods for testing the resistance of concrete to freezing and deicing chemicals. The most common methods are presented in a flowchart showing the advantages and disadvantages of a method and its applicability for a particular structure.

1495. Roberts-Seymour, M., "THE EFFECT OF HIGH RANGE WATER REDUCING ADMIXTURES ON SOME DURABILITY PARAMETERS OF SILICA FUME PORTLAND CEMENT CONCRETES," Concrete Durability. Katherine and Bryant Mather International Conference, Atlanta, Georgia, USA, 27 April-May 1987, pp. 577-85.

The author presents three experimental programmes employing high range water reducing admixtures to modify durability performance in portland cement-fume concrete. Resistivity and chloride permeability are shown to be significantly improved where fume replaced concrete utilizes superplasticizer. Superplasticizing has some demonstrated draw backs where fume is introduced to reduce alkali aggregate reactions.

1496. Robson, G., "DURABILITY OF HIGH-STRENGTH CONCRETE CONTAINING A HIGH RANGE WATER REDUCER," Concrete Durability. Katherine and Bryant Mather International Conference, Held at Atlanta, Georgia, USA, 27 April- May, 1987, pp. 765-80.

Recent construction of a segmental, precast concrete, cable stayed bridge across the Ohio river at huntington, w v involved two special designed concretes; one with 6000 psi minimum strength and one with 8000 psi minimum strength. Attaining these strength levels was markedly enhanced by the availability and use of high range water reducers (hrwr), even though the fear of non-durable concretes

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w a s a l s o he ightened . T h e c o n t r a c t f o r t h i s bridge r e q u i r e d t h a t t h e c o n t r a c t o r develop mix des igns and conduct a f i e l d t r i a l o p e r a t i o n t o shake-down' h i s p roduc t ion and p l a c i n g p rocess us ing t h e s e mix p r o p o r t i o n s . Tests o f t he c o n c r e t e s produced du r ing t h i s f i e l d t r i a l i n d i c a t e d t h a t a i r e n t r a i n e d high s t r e n g t h c o n c r e t e s c o n t a i n i n g h r w r e a s i l y m e t t h e minimum s t r e n g t h requirements b u t would not w i ths t and the f r e e z e thaw c y c l i n g of ASTM c 666. T h i s paper d i s c u s s e s t h e e f f o r t s involved :in deve loping s u i t a b l e c o n c r e t e p r o p o r t i o n s f o r t h i s work and compares f r e e z e t h a w d u r a b i l i t y of high s t r e n g t h c o n c r e t e s w i t h and wi thout e n t r a i n e d a i r and w i t h and wi thout high range w a t e r reducing admixtures .

1497 . Roy, D . and Malek, R. et a l . , "CHLORIDE PERMEABILITY OF FLY ASH-CEMENT PASTES AND MORTARS.," Concrete D u r a b i l i t y . Kather ine and Bryant Mather I n t e r n a t i o n a l Conference, A t l a n t a , Georgia, USA, 27 A p r i l - M a y 1 9 8 7 , pp. 1459-75.

The r e s u l t s o f an accelerated e l ec t ro -osmos i s experiment t o de te rmine t h e e f f e c t i v e n e s s o f d i f f e r e n t cement / f ly ash b lends (cured f o r 28 days) i n r e s i s t i n g c h l o r i d e i o n d i f f u s i o n are p resen ted . The effects o f c u r i n g tempera ture , water t o cernent i t ious materials r a t i o , p re sence of sand, etc, on t h e c h l o r i d e i o n mig ra t ion were determined. C l a s s F f l y ashes i n c r e a s e t h e e f f e c t i v e n e s s o f t h e b l end t o resist c h l o r i d e i o n mig ra t ion a t any f l y ash replacement level. T h e effect increases wi th i n c r e a s i n g pe rcen tages of replacement . T h i s i s p o s s i b l y due t o t h e s t r o n g i n t e r a c t i o n s between class f f l y ash o r i t s r e a c t i o n p roduc t s w i t h cement and i o n i c s p e c i e s i n po re f l u i d s . A h igher replacement level, on the o t h e r hand, i s r e q u i r e d t o s i g n i f i c a n t l y decrease c h l o r i d e i o n d i f f u s i o n i n cemen t / c l a s s c f l y ash b lends .

1 4 9 8 . Sakuta , M. and Urano, T . e t a l . , , "MEASURES TO RESTRAIN RATE O F CARBONATION I N CONCRETE," Concrete D u r a b i l i t y . Kather ine and Bryant Mather I n t e r n a t i o n a l Conference, A t l a n t a , Georgia, USA, 27 April-May 1987, 27 April-May 1987, pp. 1963-77.

I n an o rd ina ry atmospheric environment c o r r o s i o n of r e i n f o r c i n g steel i n a c o n c r e t e s t r u c t u r e can occur when carbon d i o x i d e permeates the c o n c r e t e and t h e p r o t e c t i v e f i l m of t h e s tee l i s des t royed . Thus t h e r a t e of ca rbona t ion i n c o n c r e t e can be a s i g n i f i c a n t . f a c t o r i n i n f l u e n c i n g t h e d u r a b i l i t y of t h e concrete. s t r u c t u r e . Various means of r e s t r a i n i n g t h e ra te of ca rbona t ion w e r e i n v e s t i g a t e d arid it w a s found t h a t

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t h e a d d i t i o n of amino a l c o h o l and g l y c o l e t h e r derivatives t o c o n c r e t e was effective f o r t h i s purpose. T h e former appears t o absorb carbon d iox ide provided from t h e s u r f a c e of t he conc re t e , and t h e l a t t e r appears t o reduce the t o t a l volume of a i r v o i d s i n t h e c o n c r e t e and t h e s i z e o f each void , i n effect , making the c o n c r e t e less permeable. I t may be concluded from t h e tests described i n t h i s paper t h a t even when t h e above-mentioned two derivatives are used t o g e t h e r i n c o n c r e t e t h e y demonstrate an e f f e c t i v e n e s s wi thout any harmful side effects. (Author/TRRL)

1 4 9 9 . Sakuta, M. e. a l . , "DEVELOPMENT OF HIGHLY DURABLE CONCRETE," Takenaka Technical Research Report , Tokyo, No. 38, NOV 1987, pp. 149-154.

I n an o rd ina ry atmospheric environment, c o r r o s i o n of r e i n f o r c i n g steel i n a c o n c r e t e s t r u c t u r e can occur when carbon d iox ide permeates t h e c o n c r e t e and t h e p r o t e c t i v e f i l m of t h e steel i s des t royed . Thus t he ra te of ca rbona t ion i n conc re t e can be a s i g n i f i c a n t f a c t o r i n i n f l u e n c i n g the d u r a b i l i t y of t h e c o n c r e t e s t r u c t u r e . I n urban a r e a s , s u l f u r o u s acid gas from t h e exhaus t of automobiles d i f f u s e d i n t he atmosphere g r e a t l y lowers t he p H of r a inwa te r . The p e n e t r a t i o n of t h i s r a inwa te r i n t o conc re t e s u r f a c e s h a s t e n s t he ca rbona t ion of t h e conc re t e . According t o t he r e s u l t s o f r e c e n t measurements, t h e p H of r a inwa te r i n t h e Tokyo d i s t r ic t i s about 3 . 0 . There have been many examples of exposed .conc re t e s u r f a c e s be ing a t t a c k e d by t h e s t r o n g ac id i ty . S ince ca rbona t ion of c o n c r e t e r e s u l t s from t h e r e a c t i o n between carbon d i o x i d e and s u l f u r o u s acid i n the atmosphere and calcium hydroxide i n cement hydra t ion products , t h e predominant concept i n t h e past has been t h a t t h i s r e a c t i o n w a s unavoidable. I n view of t h i s s i t u a t i o n , t h e a u t h o r s conducted studies on t h e use of chemical a c t i o n s wi th t h e o b j e c t i v e of p rov id ing a means of pro longing t h e l ives of c o n c r e t e s t r u c t u r e s by reducing the ra te o f ca rbona t ion .

1 5 0 0 . Samarin, A., "METHODOLOGY O F MODELING FOR CONCRETE D U R A B I L I T Y , " Concrete D u r a b i l i t y . Kather ine and Bryant Mather I n t e r n a t i o a n l Conference, A t l a n t a , Georgia, USA, 27 April-May 1987, pp. 1205-25.

Most of t h e r e p o r t e d research on d u r a b i l i t y of c o n c r e t e r e l a t e s t o some p a r t i c u l a r a s p e c t of environmental a t t a c k , v i z : - f r o s t , s u l p h a t e , s e a water a c t i o n , etc. The main o b j e c t i v e of t h i s s tudy i s t o p rov ide an architect o r a s t r u c t u r a l eng inee r w i t h t he methodology of modeling f o r c o n c r e t e d u r a b i l i t y under

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various conditions of reinforced concrete -environment interaction, which is divided into three main types, i.e., -concrete continuously submerged in water, concrete continuously exposed to air, concrete subjected to cycles of wetting and drying. The process of hydration and desiccation of cement paste as a function of pore structure and the environment becomes an important aspect of modeling for durability. Various modes of interaction between reinforced concrete and either existing or artificially created environment are expressed as a loss i.n concrete serviceability, utilising the concept of limit state design. This methodology should provide the basis for an evaluation of the most important factors of architectural, structural and technological design of reinforced concrete and clearly define the appropriate quality assurance practices, which are both necessary and sufficient to meet the specific durability requirements for each particular case of the material -environment interaction.

1501. Sarkar, S. L. and Aitcin, P. C., "DISSOLUTION RATE OF SILICA FUME IN VERY HIGH STRENGTH CONCRETE," Cement and Concrete Research, Vol. 17, No. 4 , 1987, pp. 591- 601.

A very high strength concrete, having a 91 day compressive strength of 113 MPa, was developed using Type I11 cement, limestone aggregates, sodium naphthalene superplasticizer and silica fume, with W/C ratio of 0. 24. SEM-EDXA and AEM were used to study the rate of dissolution of silica fume in this concrete, with progressive hydration. It was possible to observe the dissolution process of silica fume particles, which begin at an early stage. Within 28 days, most of the silica fume is consumed in the pozzolanic reaction. The initial reaction product is a silica rich gel which later transforms into different morphological types of C-S-H which are compacted together.

1502. Sarkar, S. L. and Aitcin, P.-C., "COMPARATIVE STUDY OF THE MICROSTRUCTURES OF NORMAL AN3 VERY HIGH-STRENGTH CONCRETES, Cement, Concrete, and Aggregates, Vol. 9, No. 2, Winter 1987, pp. 57-64.

The microstructure of a normal con.crete with water- cement ratio (w/c) = 0.56 (f'̂ c+ at 28 days = 31.8 MPa or 4610 psi) was compared with two series of very high strength concretes (up to 118 MPa or 17 120 psi), one made with Type I11 cement and the other with the same Type I11 cement plus 6 to 10 percent silica fume.

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These concretes were water cured for 91 days. Their microstructural examination was undertaken using mercury porosimetry and scanning electron microscopy- energy dispersive X-ray analysis (SEM-EDXA). Similarities and differences are described in detail. Basically, both are composed of calcium silicate hydrates (C-S-H) and calcium hydroxide (C-H) , but their proportions and morphology are quite different. The composition and types of C-S-H also vary. Significant differences in porosity and aggregate- cement bonding are present. Chloride ion permeability tests indicate the very high strength concretes to be as impervious as polymer-impregnated types.

1503. Schiessl, P., "INFLUENCE OF THE COMPOSITION OF CONCRETE ON THE CORROSION PROTECTION OF THE REINFORCEMENT," Concrete Durability. Katherine and Bryant Mather International Conference, Held at Atlanta, Georgia, USA, 27 April-May, 1987,

The report presents a discussion on the influence of the concrete composition on the pore structure and the binding capacity of the matrix and the corresponding effects on carbonation, diffusion of chlorides, depassivation of the reinforcement, and corrosion rate. The most important parameters are - the water-cement ratio, -the cement type, -the blending agents, -the cement content, and -additives and admixtures. The concrete composition must be adapted to the environmental conditions (micro climate at the concrete surface). Sufficient quality of concrete cover can only be achieved by a sufficiently long moist curing. The interrelations with respect to the influence of the concrete composition on the various durability aspects are very complex and need further detailed investigation.

1504. Schonlin, K. and Hilsdorf, H., "EVALUATION OF THE EFFECTIVENESS OF CURING OF CONCRETE STRUCTURES.," Concrete Durability. Katherine and Bryant Mather International Conference, Atlanta, Georgia, USA, 27 April-May 1987, pp. 207-226.

For the evaluation of the effectiveness of curing of concrete in the field a non-destructive, rapid test method has been developed. With this method air permeability of concrete surface layers is measured within a period of about 10 minutes, expressed in terms of a permeability index. Laboratory experiments show a close correlation between the measured permeability index and the duration of curing, curing temperature, type of cement, w/c-ratio and content of

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f l y a sh of t h e conc re t e . The method i s v e r y s e n s i t i v e t o changes i n most parameters w h i c h affect t h e p o r e s t r u c t u r e of t he hydra ted cement p a s t e and t h u s t h e d u r a b i l i t y of c o n c r e t e s t r u c t u r e s under normal exposure c o n d i t i o n s . (Author/TRFtL)

1505. Senbe t t a , E . and Malchow, G . , "STUDIES ON CONTROL O F D U R A B I L I T Y OF CONCRETE THROUGH E'ROPER C U R I N G , " Concrete D u r a b i l i t y . Kather ine and Bryant Mather I n t e r n a t i o n a l Conference, A t l a n t a , Georgia, USA, 27 April-May 1987, pp. 73-87.

T h i s work w a s undertaken t o develop t es t data which show t h e effect o f c u r i n g on t h e d u r a b i l i t y o f c o n c r e t e . I t w a s i n t ended t o o b t a i n more data about what i s a l r e a d y known o r suspec ted and was n o t i n t ended t o be an o r i g i n a l research t o d i s c o v e r new fac ts . I t i s hoped t h a t t h e in fo rma t ion derived from t h i s s tudy w i l l be o f b e n e f i t i n t he c o n t i n u i n g e f f o r t t o t e a c h p r a c t i t i o n e r s t he v i r t u e s of adhe r ing t o good c o n c r e t i n g practices and t h e consequences of d e v i a t i n g from them. I t w a s necessary t o under take t h i s work because most o f t h e c o n c r e t e t h a t i s p l a c e d i n bo th r e s i d e n t i a l and i n d u s t r i a l c o n s t r u c t i o n i s no t be ing cu red p rope r ly . The r e s u l t i s premature f a i l u r e and d e t e r i o r a t i o n which, f o r t h e most p a r t , can be p reven ted o r a t t h e leas t postponed. Q u a n t i t a t i v e l y showing t h e cause and e f f e c t r e l a t i o n s h i p between c u r i n g o f c o n c r e t e and the c o n c r e t e ' s performance under service c o n d i t i o n s i s b e l i e v e d t o h e l p i n increasing t h e awareness of p r a c t i t i o n e r s and encouraging good conc re t ing p r a c t i c e s .

1 5 0 6 . Shah, S. P . and Sankar, R. , "INTERNAL CRACKING AND STRAIN-SOFTENING RESPONSE O F CONCRETE UNDER UNIAXIAL COMPRESSION," ACI Materials Jou rna l , V o l . 84, No. 3, May-Jun 1987, pp. 200-212.

Understanding t h e s t r a i n - s o f t e n i n g response of c o n c r e t e i s impor tan t f o r numerical modeling of t h e c o n s t i t u t i v e behavior of c o n c r e t e . I n t h i s s tudy t h e n a t u r e and e x t e n t of i n t e r n a l c r a c k i n g were s t u d i e d f o r c o n c r e t e c y l i n d e r s s u b j e c t e d t o a x i a l s t r a i n s i n t h e post-peak par t of t he s t r e s s - s t r a i n curve . Seve ra l t e s t i n g methods t o reduce the e n d - r e s t r a i n t w e r e e v a l u a t e d and one t h a t gave e s s e n t i a l l y homogeneous stress d i s t r i b u t i o n w a s used f o r t h e s tudy . Long i tud ina l and t r a n s v e r s e slices o f t h e specimens loaded t o d i f f e r e n t v a l u e s of a x i a l s t r a i n s w e r e examined u s i n g p e t r o g r a p h i c tec!nniques f o r microcracks.

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1 5 0 7 . Shah, S. P. (Ed. ) and Swartz, S. E. (Ed . ) , "FRACTURE O F CONCRETE AND ROCK," SEM-RILEM I n t e r n a t i o n a l Conference, Houston, TX, Jun 1987, pp. 709.

T h i s conference proceedings c o n t a i n s 85 papers , 1 8 of which appear i n a b s t r a c t form only . The t o p i c s covered inc lude : f r a c t u r e of c o n c r e t e and rock; c o n c r e t e f r a c t u r e toughness; l o a d - r a t e effect on dynamic f r a c t u r e ; c o n c r e t e beam ins t rumented impact tests; time-dependent f r a c t u r e s t a t i s t i c a l theory ; f iber r e i n f o r c e d conc re t e f r a c t u r e p r o p e r t i e s ; recycled aggrega te-concre te mechanical p r o p e r t i e s ; rock f r a c t u r e a n a l y t i c a l models; j o i n t e d rock fracture-damage mechanic model; f r a c t u r e p r o c e s s zone o f conc re t e ; mixed-mode c o n c r e t e f r a c t u r e tests; g e o l o g i c a l material mixed-mode tests; gravi ty d a m upstream s u r f a c e h o r i z o n t a l cracks; c o n c r e t e compression-shear f r a c t u r e ; c o n c r e t e r h e o l o g i c a l f r a c t u r e theory ; f r a c t u r e parameter s i z e effects; c o n c r e t e f r a c t u r e p rocess zone a n a l y s i s ; r e i n f o r c e d c o n c r e t e modeling us ing d i s t i n c t element method; c o n c r e t e gravi ty dam s t r u c t u r a l a n a l y s i s ; c o n c r e t e and rock f r a c t u r e i n f r a r e d thermography; rock crack p ropaga t ion r e s i s t a n c e ; delayed crack i n s t a b i l i t y i n c o n c r e t e ; f r a c t u r e t e s t i n g methods and r e s u l t s .

1 5 0 8 . Skalny, J. and Roberts , L . R. , "HIGH-STRENGTH CONCRETE," Annual R e v i e w of M a t e r i a l s Science, Vol. 17, 1987,

The chapter cove r s the p r e s e n t s t a t e of knowledge w i t h r e s p e c t t o t h e fundamental aspects of c o n c r e t e s t r e n g t h development and d i s c u s s e s novel approaches be ing in t roduced i n t he conc re t e c o n s t r u c t i o n f i e l d . This review i s r e s t r i c t e d t o c o n c r e t e s p r i m a r i l y based on h y d r a u l i c cements and i n c l u d e s only brief mention o f t e c h n o l o g i e s t h a t are l imited t o p a s t e s and low- volume shaped ar t ic les . I t does no t d e a l w i t h aspects o f c o n c r e t e performance not d i r e c t l y re la ted t o s t r e n g t h .

1 5 0 9 . Smadi, M. and Slate , F. e t a l . , "SHRINKAGE AND CREEP O F HIGH-, MEDIUM-, AND LOW-STRENGTH CONCRETES, I N C L U D I N G OVERLOADS, 'I ACI Materials Jou rna l , V o l . 8 4 , No. 3, May 1987, pp. 224-234.

T h e i n f l u e n c e of d ry ing and of s u s t a i n e d compressive stresses, a t and i n excess o f t h e normal working stress levels, on the shr inkage and creep p r o p e r t i e s of high-, medium-, and low-s t rength c o n c r e t e s w e r e exper imenta l ly s t u d i e d and compared.

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The 28-day compressive strength of the materials studied ranged from 3000 to 10,000 psi (21 to 69 ma). The long-term shrinkage was found to be greater for low-strength concrete and smaller for medium- and high-strength concretes. Creep strain and normalized creep were smaller for high-stre:2gth than for concretes of medium and low strengths. The creep- stress proportionality limit (as a percent of fc) was higher for the high-strength con,zrete than for the others by about 20 percent. Data on creep recovery for the three materials are also presented.

1510. Staynes, B. W., "PRODUCTION PERFDRMANCE AND POTENTIAL OF POLYMERS IN CONCRETE, Proceedings, 5th International Congress on Polymers in Concrete, Brighton Polytechnic, Sep 1987, pp. 424.

Thirteen sections include papers presented during 14 sessions at this conference. Subjects addressed are: international perspectives; design, production, and performance in relation to construction; design and behavior in relation to construction; machine tool manufacturing and performance; fundamental properties of concrete polymers; precast and decorative applications; repair and renovation relating to structural performance; underwater construction with nondispersible concrete; waste management and corrosion resistance; and strategic perspectives. A n author index is included. A method for predicting the spacing and width of cracks in concrete tension members reinforced with welded wire fabric (WWF) is presented. According to the method, WWF provides better crack control than conventional reinforcement only if the spacing of the transverse wires is restricted to certain critical values. Deformed fabric is superior to an equivalent smooth fabric, as far as cracking behavior is concerned. Test results of 70 tension members reinforced. with both smooth and deformed WWF as presented in this paper are in good agreement with the theoretical predictions.

1511. Tanahashi, I. and Ohgishi, S. et al., "EVALUATION OF DURABILITY FOR CONCRETE IN TERMS OF WATERTIGHTNESS BY 'PERMEABILITY COEFFICIENT TEST FESULTS'," Concrete Durability. Katherine and Bryant Mather InternationalConference, Atlanta., Georgia, USA, 27 April-May 1987, pp. 187-206.

The authors developed a new type of permeability testing apparatus which is capahle of direct measurement of the permeability coefficient of structural concrete, for the purpose of establishing a

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new method to evaluate the quality and durability of structural concrete in terms of water-tightness. Effects of fluidity and mix proportion on the permeability was investigated on a concrete of typical specimen (disk and hollow disk types). Next, permeability coefficient of structural concrete (wall and floor) were investigated and evaluation of concrete durability was carried out. From these experiments, the following conclusion was obtained. The permeability coefficient of typical specimen which filled into the form sufficiently can be represented by an experimental equation. The durability of structural concrete can be evaluated from the water- tightness which is derived from comparison of measured permeability coefficient and the theoretical permeability coefficient obtained by substituting the water cement ratio and unit water quantity of designed mix proportion into the above experimental equation. The authors understand that the permeability testing apparatus is sufficiently applicable to the structural concrete permeability test, and method to evaluate the durability of structural concrete using this apparatus is a ready available means which is capable of evaluating the durability of structural concrete in terms of water-tightness.

1512. Tayabji, S. D. and Okamoto, P. A., "ENGINEERING PROPERTIES OF ROLLER-COMPACTED CONCRETE," Transportation Research Record, No. 1136, 1987, pp. 33-45.

An investigation was conducted to develop a procedure for the design of roller-compacted concrete (RCC) pavements. This paper is a report on the laboratory protion of the investigation that was conducted to determine the engineering properties of RCC. Specimens for the laboratory tests were obtained from a full-scale test section constructed using a 10- ton vibratory roller. Specimens were tested for flexural, split-tensile, and compressive strength; modulus of elasticity; and fatigue properties. The engineering behavior of RCC was determined to be similar to that of conventional concrete. Test results for RCC made using 243 to 285 lb/yd**3 of cement show that RCC is capable of providing relatively high in- place strength. As with conventional concrete, RCC strengths produced are even higher when higher cement contents are used. Specimens prepared by using the vibrating table produced significantly lower densities and strengths because the moisture content was lowered.

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1513.

1514

Whiting, D . , "DURABILITY OF HIGH-STRENGTH CONCRETE., Concrete D u r a b i l i t y . Kather ine and Bryant Mather I n t e r n a t i o n a l Conference, A t l a n t a , Georgia, USA, 27 A p r i l - M a y 1987, pp. 169-186.

Concrete mixtures w e r e des igned t o nominal 28-day compressive s t r e n g t h s of 6000, €1000 and 1 0 0 0 0 p s i ( 4 1 , 55, and 69 mpa) us ing mix des igns t y p i c a l o f commercial p roduct ion of high s t r e n g t h c o n c r e t e s . produce t h e h i g h e r s t r e n g t h Concretes , a d d i t i o n s of f l y a s h (class C ) , water r educe r s , and high-range water r educe r s were u t i l i z e d . Concretes were s u b j e c t e d t o b o t h mois t and a i r cu res . D u r a b i l i t y t es t procedures inc luded r a p i d freezimg and thawing i n water, and a p p l i c a t i o n of d e i c i n g a g e n t s . A l l moist cured, non-a i r -en t ra ined c o n c r e t e s performed poor ly , e x h i b i t i n g r a p i d d e t e r i o r a t i o n i-rrespective of s t r e n g t h level. En t ra ined a i r c o n t e n t s , measured i n t h e fresh conc re t e , of 3 t o 4 p e r c e n t w e r e found t o be necessa ry i n o r d e r t o a s s u r e adequate d u r a b i l i t y when c o n c r e t e s w e r e s u b j e c t e d t o f r e e z i n g and thawing i n water. However, moist-cured, a i r - e n t r a i n e d , high s t r e n g t h conc re t e s , p repared a t 8000 and 1 0 0 0 0 p s i , (55 and 69 mpa), wh i l e performing s a t i s f a c t o r i l y w i t h respect t o f r e e z i n g and thawing i n w a t e r , w e r e less r e s i s t a n t t o a p p l i c a t i o n s of deiicing a g e n t s t h a n w e r e a i r - e n t r a i n e d c o n c r e t e s p repa red a t t h e lower s t r e n g t h level. This w a s t r u e even w i t h a i r c o n t e n t s between 7 and 8 p e r c e n t i n t h e fresh c o n c r e t e . g e n e r a l l y b e n e f i c i a l effects on r e s i s t a n c e t o f r e e z i n g and thawing and a p p l i c a t i o n of d e i c i n g a g e n t s t o normal s t r e n g t h , a i r - e n t r a i n e d c o n c r e t e s , b u t had l i t t l e p o s i t i v e i n f l u e n c e on d u r a b i l i t y o f h igh s t r e n g t h mixtures . Performance of non-a i r - en t r a ined c o n c r e t e s d u r i n g f r e e z i n g and thawing i n water was somewhat improved when given a p e r i o d of a i r dry ing; however, a l l non-a i r -en t ra ined c o n c r e t e s performed poor ly when exposed t o d e i c i n g agen t s .

T o

A i r c u r i n g had

Whiting, D . and Schmit t , J., "DURABILITY O F IN-PLACE

ADMIXTURES, T ranspor t a t ion Research Board, Sep 1987, pp. 7 2 .

f i e l d s tudy of the d u r a b i l i t y o f p o r t l a n d cement c o n c r e t e highway wearing s u r f a c e s c o n t a i n i n g high- range water-reducing admixtures . D u r a b i l i t y surveys w e r e carried o u t on 1 2 s t ructurczs ranging from 4 t o 1 2 y e a r s o f age. bridge decks, bridge deck ove r l ays , and pavements. T h e t o t a l area a f f e c t e d by v e r y l i g h t t o moderate s c a l i n g w a s minor, amounting t o less t h a n 4 p e r c e n t of

CONCRETE CONTAINING HIGH-RANGE WATER-REDUCING

This r e p o r t documents and p r e s e n t s t h e r e s u l t s of a

These s t r u c t u r e s inc luded highway

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the area surveyed. L e s s t h a n 1 / 2 p e r c e n t w a s c h a r a c t e r i z e d by medium t o heavy s c a l i n g , where c o a r s e aggregate particles were s i g n i f i c a n t l y exposed. A three-parameter performance model i n c l u d i n g water- cement r a t i o , amount of e n t r a i n e d a i r removed from the s u r f a c e , and a i r - v o i d spac ing f a c t o r w a s developed and o f f e r e d r easonab le c o r r e l a t i o n w i t h t h e f i e l d obse rva t ions . The f i n d i n g s o f t he s tudy i n d i c a t e t h a t high q u a l i t y , du rab le conc re t e can be produced u s i n g high-range water-reducing admixtures .

1515. Whiting, D. and S c h m i t t , J., "DURABILITY OF IN-PLACE CONCRETE CONTAINING HIGH-RANGE WATER-REDUCING ADMIXTURES," NCHRP Report , N296, Sep 1987, pp. 72 .

T h i s r e p o r t documents and p r e s e n t s t he r e s u l t s of a f i e l d s tudy o f t h e d u r a b i l i t y of p o r t l a n d cement c o n c r e t e highway wearing s u r f a c e s c o n t a i n i n g high- range water-reducing admixtures . D u r a b i l i t y surveys w e r e carried ou t on 1 2 s t r u c t u r e s ranging from 4 t o 1 2 years of age. These s t r u c t u r e s inc luded highway bridge decks, bridge deck ove r l ays , and pavements. The t o t a l area affected by very l i g h t t o moderate s c a l i n g w a s minor, amounting t o less t h a n 4 p e r c e n t of t he a r e a surveyed. L e s s t h a n 1 / 2 p e r c e n t w a s c h a r a c t e r i z e d by medium t o heavy s c a l i n g , where c o a r s e aggregate p a r t i c l e s were s i g n i f i c a n t l y exposed. A three- parameter performance model i n c l u d i n g water-cement r a t i o , amount of e n t r a i n e d a i r removed from t h e s u r f a c e , and a i r - v o i d spac ing f a c t o r was developed and o f f e r e d r easonab le c o r r e l a t i o n w i t h t he f i e ld o b s e r v a t i o n s . The f i n d i n g s of t h e s tudy i n d i c a t e t h a t high q u a l i t y , du rab le c o n c r e t e can be produced u s i n g high-range water-reducing admixtures .

1516. Xu, J., "STRENGTH AND STRAIN CALCULATION OF CONCRETE UNDER BIAXIAL TENSILE AND COMPRESSIVE STRESS STATE," F r a c t u r e o f Concrete and Rock: SEM-RILEM I n t e r n a t i o n a l Conference, Houston, TX, Jun 17-19 1987, pp. 383.

On t h e b a s i s of o v e r a l l a n a l y s i s and comparison between the r e s u l t s ga ined bo th a t home and abroad, t h i s paper sugges t s an average stress, s ta tes a formula t o c a l c u l a t e t he b i a x i a l compression and t e n s i o n s t r e n g t h by us ing the maximum s t r a i n t h e o r y c o n d i t i o n and the features o f c o n c r e t e m a t e r i a l p r o p e r t i e s , w i t h c o n s i d e r a t i o n s t o t h e grade of c o n c r e t e . A better co inc idence has been ob ta ined among t h e formulas and the tes t r e s u l t s , which may be used as r e f e r e n c e f o r des ign and b u i l d i n g code. (Author abstract)

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1517. Yankelevsky, D. 2. and Reinhardt , H. W . , "RESPONSE O F PLAIN CONCRETE TO CYCLIC T E N S I O N , " ACI Materials Jou rna l , Sept -Oct 1987, p-p. 365-373.

Cracking i s an important f e a t u r e o f a c o n c r e t e s t r u c t u r e t ha t affects cons ide rab ly i t s o v e r a l l behavior . The c rack ing p rocess s tar ts a t a r e l a t ive ly low t e n s i l e stress, and t h e degree o f t e n s i l e damage increases wi th an i n c r e a s e i n t h e t e n s i l e s t r a i n ( o r d i sp l acemen t ) , e x h i b i t i n g a s o f t e n i n g behavior . For a complete unders tanding of c rack development, tests shou ld be performed on conc re t e specimens a t v a r i o u s l o a d h i s t o r i e s . I n r e c e n t years, t e s t i n g t echn iques have been improved t o y i e l d re l iab le r e s u l t s , and tests a t v a r i o u s displacement p a t h s are be ing performed a t t h e S t e v i n Laboratory, D e l f t U n i v e r s i t y of Technology. A n a l y t i c a l e x p r e s s i o n s have been proposed t o describe the e n t i r e monotonic behavior , as w e l l as t h e response t o cycl ic load ings , and comparisons w i t h available tes t data a r e shown.

1518. Zhang, B. and Zhu, 2 . e t a l . , "FATIGUE RUPTURE O F PLAIN CONCRETE ANALYSED BY FRACTURE MECHANICS," F r a c t u r e of Concrete and Rock: SEM-RILEM I n t e r n a t i o n a l Conference, 1987, pp. 90-95.

T h e f a t i g u e damage mechanisms o f c o n c r e t e under r e p e a t e d l o a d s are s t u d i e d . Based on the r e s u l t s o f f a t i g u e tests of c o n c r e t e beam specimens, new f a t i g u e phenomena and process are found and a computing formula i s p u t forward. The p h y s i c a l meanings of t h e formula are exp la ined from t h e s t a n d p o i n t of mesoscopic f r a c t u r e mechanics and damage mechanics. This formula could be used t o p r e d i c t t h e f a t i g u e l i f e o r remaining l i fe of c o n c r e t e c o n s t r u c t i o n s .

1519. Zia, P . and Perenchio, W . F . e t a l . , "RESEARCH NEEDS FOR HIGH-STRENGTH CONCRETE," ACI M a t e r i a l s J o u r n a l , V o l . 84, No. 6, Nov-Dec 1987, pp. 559-561.

Desp i t e t h e amount of research t h a t has been performed on h igh - s t r eng th c o n c r e t e . ACI Committee 3 6 3 feels t h a t t h e r e are s t i l l research needs i n many areas t o ensu re t h e economical and p rope r a p p l i c a t i o n of t h e material . The o b j e c t i v e of t h i s r e p o r t i s t o p r e s e n t a brief summary o f these research needs. T h i s summary can p rov ide guidance t o f i n a n c i a l sponsors such as government agencies , r e s e a r c h i n s t i t u t i o n s , i n d u s t r y , and t h e academic community. Cons ide ra t ion of r e s e a r c h needs should inc lude th ,e u se of s p e c i a l blended cements f o r high-strengt :h c o n c r e t e .

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1520. "BRIDGE DECK MATERIALS - MAKING A CHOICE," Better Roads, Vol. 58 No. 8, Aug 1988, pp. 4.

This article reviews some of the bridge deck materials currently in use. The original reinforced concrete deck on the Golden Gate Bridge was replaced with an orthotropic steel plate deck. It was chosen over concrete-filled steel grid and precast concrete designs because it was less expensive over its lifetime, considering maintenance costs. Portland cement overlays offer potential installation cost advantages over latex-modified concrete in some cases. However, latex-modified concrete overlays are needed where there is inadequate rebar cover, significant delamination repair areas, or where wear may be of concern (e.g., high-volume routes or routes with high chain or studded tire use). Grid reinforced concrete decks offer cost and advantages including reduced dead load, durability (up to 50 years), composite action with supporting steel, speedy deck replacement, and ease of precasting. High early strength, latex- modified concrete overlays can put traffic back onto a bridge earlier than many other materials, in 24 hours as opposed to 4 to 7 days. Other bridge deck materials are choosen for their ability to resist corrosion or deterioration of concrete. These include polyester styrene, methacrylate concrete, and admixtures (calcium nitrate, pozzolons, and plasticizers) .

1521. "CRACKING STUDIES ADVANCE, Engineering News Record, Vol. 221 No. 19, Nov 1988, pp. 17.

It is told how fracture mechanics analysis is a way to make more efficient use of high-strength concrete in structural designs. By applying fracture mechanics analysis to the study of high-strength concrete, researchers could prevent failures and advance technology. A notched beam test similar to fracture toughness tests used on steel sections, is being used to examine how difficult it is to extend a crack once it has started. A number of ways are being studied of reducing the brittleness of high-strength concrete. By packing the cement in the slurry more efficiently, researchers are measuring the increased density of the solid material and the concrete's reduced porosity. It was found that the addition of silica fume produces stronger concrete because the reaction of the fume with calcium hydroxide works to produce amorphous

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c a l c i u m s i l i ca t e h y d r a t e , the s t . rong s u b s t a n c e a t t he hear t o f c o n c r e t e .

1522. "CAN WE DOUBLE CONCRETE LIFE?," Better Roads, Vol . 58, No. 9, Sep 1988, pp. 27-34.

Computer a n a l y s i s o f t h e per formance o f v a r i o u s c o n c r e t e mixes o v e r t h e l a s t three g e n e r a t i o n s i n d i c a t e s t h a t i n a p p r o p r i a t e aggregate par t ic le d i s t r i b u t i o n i s a l e a d i n g c a u s e o f pavement f a i l u r e . O f the major i n d u s t r i a l n a t i o n s , o n l y t h e US u s e s 2 s i z e s ( c o a r s e and f i n e ) o f aggregates i n a mix. T h e o t h e r s u s e a t l eas t 3. T h i s practice gives better pa r t i c l e d i s t r i b u t i o n , s i n c e t h e t h i r d aggregate p r i m a r i l y c o n s i s t s o f i n t e r m e d i a t e s i z e s . These form a bridge between large and f i n e par t ic les , which f i l l s ma jo r v o i d s and i n c r e a s e s c o n c r e t e d e n s i t y . When t h e i n t e r m e d i a t e - s i z e d aggregates are m i s s i n g o r f e w i n number, t h e c o n c r e t e must have more, l e s s - d e n s e m o r t a r . T h e higher t h e m o r t a r c o n t e n t , t h e more e a s i l y t h e s u r f a c e can be abraded. T h i s leads t o a greater number o f c h a n n e l s t h r o u g h which a t t a c k i n g material c a n migrate.

1523. ACI Committee 214, "SIMPLIFIED VERSION OF THE RECOMMENDED PRACTICE FOR EVALUATION OF STRENGTH TEST RESULTS," ACI Materials J o u r n a l , Vol . 85, No. 4 , J u l y - Aug 1988, pp. 272-279.

The p u r p o s e o f t h i s r e p o r t i s t o i n t r o d u c e t h e u s e o f a s implif ied v e r s i o n o f t h e s t a t i s t i c a l c o n c e p t s as o u t l i n e d i n ACI 214 f o r t he s p e c i f i c a t i o n , c o n t r o l , a n d e v a l u a t i o n of t he p r o d u c t i o n o f c o n c r e t e . F o r a more e l a b o r a t e d i s c u s s i o n o f t h e c o n c e p t s , see t h e "Recommended P r a c t i c e f o r t he E v a l u a t i o n o f S t r e n g t h T e s t R e s u l t s of Concre te" (ACI 2 1 4 ) .

1524. ACI Committee 228, "IN-PLACE METHODS FOR DETERMINATION OF STRENGTH O F CONCRETE," ACI M a t e r i a l s J o u r n a l , Vol. 85, No. 5 , Sep-Oct 1988, pp. 446-471.

The s ta te o f t h e a r t i n t he u s e o f methods f o r d e t e r m i n i n g t he i n - p l a c e compress ive s t r e n g t h of c o n c r e t e i s r e p o r t e d . The methods c o v e r e d i n c l u d e t h e rebound hammer, p r o b e p e n e t r a t i o n , p u l l o u t , u l t r a s o n i c p u l s e v e l o c i t y , m a t u r i t y , and c a s t - i n - p l a c e c y l i n d e r . T h e u n d e r l y i n g p r i n c i p l e s and i n h e r e n t l i m i t a t i o n s c f each method are d i s c u s s e d . R e p e a t a b i l i t y of t e s t r e s u l t s i s reviewed, and recommendations are g i v e n f o r d e v e l o p i n g t h e c o r r e l a t i o n r e l a t i o n s h i p f o r each tes t method. Recommendations are g i v e n f o r t h e number of

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tests, and statistical techniques for interpretation of test results are described.

1525. Aitcin, P.-C., "CURING TEMPERATURE AND VERY HIGH STRENGTH CONCRETE," Concrete International: Design and Construction, Vol.10, No.10, Oct 1988, pp. 69-72.

The effects of early temperature rise in very high strength concrete used in structural elements are investigated. The compressive strengths of specimens are tested and compared to each other and to that of core samples taken from instrumented, experimental columns. Variables affecting the laboratory specimens include cement content, the addition of silica fume, and the curing process.

1526. Alexander, M. G., "USE OF ULTRASONIC PULSE VELOCITY FOR FRACTURE TESTING OF CEMENTED MATERIALS," Cement, Concrete and Aggregates, Vol. 10, No. 1, Summer 1988, pp. 9-14.

The paper describes the use of the ultrasonic pulse velocity technique to measure two important features of fracture in notched concrete beams: the extent of the zone of microcracking that develops ahead of the notch or crack, and the depth of the main (or stress- free) crack. Beams of 100 mm in width and ranging from 100 to 500 mm in depth were tested, and ultrasonic pulses were transmitted longitudinally through the beams at various elevations. Ultrasonic readings taken at elevations above or below the visible crack tip were found to be sensitive to the development of the microcracked zone or to main crack growth, respectively. Based on pulse transit time measurements, the average depth of the microcracked zone was about 44% of the residual beam depth, taking all the beam sizes together.

1527. Anderson, F. D., "STATISTICAL CONTROLS FOR HIGH- STRENGTH CONCRETE," Texas Civil Engineer, Vo1.58, No.1, 1988, pp. 16-20.

This study provides a simplified insight into the mechanics of optimizing the many variables associated with high-strength concrete. It is evident that some of the variables that affect high strength in concrete may not be obvious when reviewed against the experience of traditional concrete production. By the use of applied statistics to examine many variables in research and development as well as day-to-day production of high-strength concrete, many of these

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e l u s i v e variables can be i d e n t i f i e d and c o n t r o l l e d . By the u s e o f m u l t i p l e r e g r e s s i o n a n a l y s i s , p a r t i c u l a r l y step-wise r e g r e s s i o n t o s y s t e m a t i c a l l y discard variables having t h e l e a s t effect , a working mathematical model can be developed t h a t w i l l p rov ide a high degree of confidence and i n t e g r i t y i n t h e completed p r o j e c t .

1528. Anderson, S. and C a r r a s q u i l l o , R . , "THE EFFECTS O F WITHHOLDING M I X I N G WATER AND RETEMPERING ON PROPERTIES O F CONCRETE., I n t e r i m Report , Texas Un ive r s i ty , Aus t in Center f o r T ranspor t a t ion Research, Feb 1988, pp. 128 .

b a t c h i n g fol lowed by retempering of t h e mix a t t h e j o b - s i t e on the p r o p e r t i e s of t h e c o n c r e t e produced f o r highway a p p l i c a t i o n s w a s examined i n an exper imenta l program. Add i t iona l ly , t h e effects o f redosage w i t h water above and beljond t h a t called f o r i n t h e specified mix des ign w a s examined. T e s t s w e r e performed t o determine t h e effects on slump, a i r c o n t e n t , u n i t weight, compressive s t r e n g t h , f l e x u r a l s t r e n g t h , a b r a s i o n r e s i s t a n c e , and freeze- thaw r e s i s t a n c e . The effects of va ry ing the wi thhold ing amount, wi thhold ing t i m e , and cement c o n t e n t on t h e fresh and hardened conc re t e p r o p e r t i e s mentioned above were examined. The c o n c r e t e examined w a s produced a t a ready-mixed c o n c r e t e f a c i l i t y :in o r d e r t o d u p l i c a t e as c l o s e l y as p o s s i b l e j o b - s i t e c o n d i t i o n s a r i s i n g i n t yp ica l c o n c r e t e c o n s t r u c t i o n . The r e s u l t s of t h e s t u d y show t h a t s i g n i f i c a n t d e t r i m e n t a l effects occur when mixing w a t e r i s withheld and c o n c r e t e i s retempered a t a l a te r t i m e . Slump, a i r c o n t e n t , a b r a s i o n r e s i s t a n c e , and freeze- thaw r e s i s t a n c e are a l l adve r se ly affected. The effects were found t o v a r y w i t h v a r i a t i o n s i n bo th wi thhold ing t i m e and cement c o n t e n t . The s t r e n g t h w a s no t affected when water w a s w i thhe ld and c o n c r e t e was retempered, b u t a r e d u c t i o n i n s t r e n g t h accompanied an i n c r e a s e i n water-cement r a t i o above design values a t redosage . The p r o p e r t i e s changed l e a d t o c o n c r e t e o f reduced q u a l i t y and q u e s t i o n a b l e performance. Research s tudy t i t l e : Gu ide l ines f o r Proper Use of S u p e r p l a s t i c i z e r s and t h e Effec t o f Retempering P r a c t i c e s on Performance and D u r a b i l i t y o f Concrete.

T h e effects of wi thhold ing mixing water a t i n i t i a l

2 2 6

1529. Anon, "RESISTANCE OF HIGH-STRENGTH CONCRETE TO FREEZING AND THAWING," Concrete Construction, Vol. 33, No. 3, Mar 1988, pp. 344, 346-347.

Two developments have made possible the new generation of high-strength concrete now available for routine construction: Superplasticizers, the high- range, water-reducing admixtures that permit placement of concretes with very low water-cement ratios; and Use of silica fume (also called microsilica), a pozzolan of extremely high fineness. The advent of this high-strength concrete has put requirements for strength and durability in conflict. Because entrained air reduces the strength of concrete, builders seek to eliminate or limit its use. However, the problem cannot be avoided in highway structures. Highway concrete structures are typically constructed with thin sections permanently exposed to both wetting and freezing. The highway industry pioneered the development and practical use of air entrainment as the primary defense for concrete against the ravages of freezing and thawing. for the low- and medium- strength concretes traditionally used in highway applications, entrained air has served well where exposure has not been complicated by reinforcement corrosion problems or by the use of coarse aggregates.

1530. Balaguru, P. and Ramakrishnan, V., "CHLORIDE PERMEABILITY AND AIR-VOID CHARACTERISTICS OF CONCRETE CONTAINING HIGH RANGE WATER REDUCING ADMIXTURE," Cement and Concrete Research, Vol. 18, No. 3, May 1988, pp. 401-414.

Presents the results of an experimental investigation of chloride permeability and air-void characteristics of concrete containing a high-range water-reducing admixture. Two typical mixture proportions with cement contents of 611 and 799 lb/(yd**3) (363 and 474 kg/(m**3) were tested. The respective water-reducing admixture contents by weight of cement were 1.0 and 1.2 percent. Chloride permeability tests were conducted using 6 x 12 in. (150 x 300 mm) cylinders and an 8 percent sodium chloride solution. The chloride contents were determined at depths of 0.5, 1.0, 1.5, and 2.0 in. (12.7, 25.4, 38.1, and 50.8) for time periods of 1, 3, 6, 9, and 12 months. Air-void characteristics were studied using 0.75 in. (19 mm) thick prisms. Air-void characteristics results obtained from three other laboratories are compared with the results of this investigation. The results show that chloride permeability of concretes made with and without a

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high-range water-reducing admixture i s about t h e same. T h e a i r - v o i d Characteristics o f c o n c r e t e s tested i n t h i s i n v e s t i g a t i o n us ing high-range water-reducing admixtures are s a t i s f a c t o r y . Spacing f a c t o r s , chord- i n t e r c e p t s , and the frequency d i s t r i b u t i o n s of chord- intercepts i n terms of t h e i r l e n g t h s are w i t h i n t h e normally recommended range.

1531. Barker , M. G. and R a m i r e z , J. A , , , "DETERMINATION O F CONCRETE STRENGTHS WITH BREAK-OFF TESTER," ACI

221-228. Materials Jou rna l , V o l . 85, No. 4, July-Aug 1988, pp.

The c o r r e l a t i o n s o f t h e break-off t e s t r e s u l t s w i t h t h o s e o f t h e ASTM compression c y l i n d e r and t h e ASTM modulus of r u p t u r e beam t e s t s w e r e examined. The variables i n v e s t i g a t e d were t h e water-cement r a t i o , t h e aggregate type , and t h e maximum aggrega te s i z e . I n t h i s s tudy , t h e u n c e r t a i n t i e s a s s o c i a t e d w i t h t h e 75 compression c y l i n d e r s , 59 modulus of r u p t u r e beanis, and 99 break-off tests w e r e eva lua ted . R e s u l t s i n d i c a t e t h e break-off t e s t i s less i n f l u e n c e d b y aggregate effects t h a n t h e modulus of r u p t u r e beam. The i n h e r e n t v a r i a b i l i t y of t he beam tes t i s n o t e v i d e n t i n t h e break-off t es t . The break-off t es t bet ter c o r r e l a t e s w i t h t he compression c y l i n d e r . The r e s u l t s show t h a t e s t i m a t i n g i n s i t u compressive s t r e n g t h s u s i n g t h e break-off tester seems promising f o r aggregate s i z e s up t o a t least one-half i n . (13 mm) maximum. Furthermore, prev:ious s t u d i e s suggest t h a t t h e r e l a t i o n s h i p is adequate f o r larger s i z e aggregates.

1532. Bauer, C. J., "NEW STANDARDS FOR INNOVATIVE COMPOSITE CONSTRUCTION, I' Const ruc t ion S p e c i f i e r , V o l . 4 1 , No. 4, Apr 1988, pp. 84-89.

S e a t t l e ' s new Two Union Square o f f i c e complex i s unique i n t h a t it w i l l be suppor ted by large c o n c r e t e columns wrapped i n steel shells.. T h e s t r e n g t h of t he columns w i l l be a r eco rd b reak ing 1 9 , 0 0 0 p s i - 36 p e r c e n t s t r o n g e r than columns used i n any p r e v i o u s s t r u c t u r e . Because of t h e i r unique character is t ics , t he columns used i n Two Union Square are larger t h a n conven t iona l columns, bu t s t i l l save space . They accomplish t h i s because t he s t i f f n e s s of a column i s roughly p r o p o r t i o n a l t o i t s a r e a . The Two Union Square columns p r o c e s s high s t r e n g t h f o r heavy l o a d c a r r y i r g c a p a b i l i t i e s , s o t h e y m u s t a l s o posses a high modulcs o f e l a s t i c i t y , o r s t i f f n e s s .

2 2 8

1533. Bazant, Z . P . and Sener, S., "SIZE EFFECT I N PULLOUT TESTS," ACI Materials Journa l , V o l . 85, No. 5, Sep-Oct 1988, pp. 347-351.

T e s t r e s u l t s on t h e p u l l o u t s t r e n g t h o f r e i n f o r c i n g bars embedded i n conc re t e are r e p o r t e d . The t es t specimens are 1.5, 3, and 6-in. cubes w i t h g e o m e t r i c a l l y s imi l a r bars. The r e s u l t s are found t o be c o n s i s t e n t w i t h Bazant 's s i z e effect l a w f o r t h e nominal stress a t s o f t e n i n g f a i l u r e s due t o d i s t r i b u t e d c rack ing . Based on t h e s i z e effect l a w , an approximate formula p r e d i c t i n g p u l l o u t s t r e n g t h i s developed.

1534. B i s a i l l o n , A. and Malhotra, V. M., "PERMEABILITY OF CONCRETE USING A UNIAXIAL WATER-FLOW METHOD," Pe rmeab i l i t y o f Concrete, ACI SP-108, a, 1988, pp. 175-194.

Paper describes t h e mod i f i ca t ions made t o a p r e v i o u s l y developed CANMET tes t method t o measure t he p e r m e a b i l i t y of c o n c r e t e and d i s c u s s e s t es t r e s u l t s t o de te rmine t h e r e p r o d u c i b i l i t y of the t e s t method. B r i e f l y , t h e tes t method c o n s i s t s of measuring t h e u n i a x i a l water flow through c y l i n d e r s (125 mm high w i t h a diameter of 150 mm) under a p r e s s u r e of 3 .5 ma. A large number of c o n c r e t e specimens with water- cement r a t i o s of 0.65 and 0.80 w e r e tested. A l i m i t e d number o f t es t specimens having w / c o f 0 . 2 2 and 0 . 2 7 w e r e a l s o tested. T e s t r e s u l t s show t h a t t h e wi th in- batch v a r i a t i o n f o r t h e tes t method i s high , and t h i s i s probably due t o t h e heterogenous n a t u r e of t h e c o n c r e t e . For c o n c r e t e w i t h w / c of 0 .22 and 0 . 2 7 , t h e r e was no ou t f low of water, and t h i s t echn ique i n the p r e s e n t form may no t be s u i t a b l e f o r measuring the p e r m e a b i l i t y of ve ry high s t r e n g t h conc re t e .

1535. B o r t o l o t t i , L . , "DOUBLE-PUNCH TEST FOR TENSILE AND COMPRESSIVE STRENGTHS I N CONCRETE, '' ACI Materials J o u r n a l , V o l . 85, N o . 1, Jan-Feb 1988, pp. 26-32.

A method of e v a l u a t i n g t h e t e n s i l e s t r e n g t h i n c o n c r e t e is i l l u s t r a t e d by i n t e r p r e t i n g the f a i l u r e mechanism from t h e double-punch t es t . A p a r t i c u l a r Coulomb-like f a i l u r e c r i t e r i o n i s a t t h e b a s i s of t h i s method. Ana lys i s i s conducted by c o n s i d e r i n g two s u c c e s s i v e l i m i t s t a t e s through which the s t r u c t u r e , r e p r e s e n t e d by a conc re t e cube, p a s s e s . The f i r s t s t a t e corresponds t o t h e t e n s i l e s t r e n g t h reached i n t h e s p l i t t i n g s u r f a c e and a l lows f o r o b t a i n i n g an expres s ion bo th o f t h e t e n s i l e s t r e n g t h o f t h e material and of i t s compressive s t r e n g t h by means of

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t h e Coulomb-like f a i l u r e c r i t e r i o n . The second l i m i t s tate, cor responding t o t h e f a i l u r e o f t h e c o n i c a l s u r f a c e s under t h e l o a d p l a t e s , p o i n t s o u t t h a t such a s ta te i s reached a f t e r a c o n s t a n t l oad ing r e d i s t r i b u t i o n p rocess , w i th s o f t e n i n g i n t h e t e n s i l e f a i l u r e s u r f a c e .

1536. B r e t t , D . M., "RCC PAVEMENTS I N TASMANIA, AUSTRALIA, R o l l e r Compacted Concrete 11, Proceedings o f t h e Conference, San Diego, CA, 1988, pp. 369-379.

Over 60,000 m**2 o f h igh s t r e n g t h R o l l e r Compacted Concrete (RCC) pavement has been completed i n Tasmania, A u s t r a l i a , s i n c e Decemher 1986. P r o j e c t s have ranged from f o o t p a t h s and small i n d u s t r i a l ha rds t ands t o h a u l roads f o r mining o p e r a t i o n s and a s e c t i o n o f p u b l i c highway. Several aggregate t y p e s , g rad ings and j o i n t i n g systems have been used. T h e pavement RCC mix has inc luded a p r o p o r t i o n o f condensed s i l i c a fume (CSF) w h i c h has been found t o have a s i g n i f i c a n t effect on pavement s t r e n g t h . T h e RCC mix des ign techniques , c o n s t r u c t i o n d e t a i l s , q u a l i t y c o n t r o l t e s t i n g and pavement performance are d i scussed . Cos t ing on v a r i o u s p r o j e c t s i s p r e s e n t e d .

1537. C a r r a s q u i l l o , P . M. and C a r r a s q u i l l o , R. L . , "EFFECT OF USING UNBONDED CAPPING SYSTEMS ON THE COMPRESSIVE STRENGTH OF CONCRETE CYLINDERS," ACI Materials J o u r n a l , V o l . 85, N o . 3, May-Jun 1988, pp. 1 4 1 - 1 4 7 .

More t h a n 5 0 0 6- x 12-in. (152-x 305-mm) c y l i n d e r s from c o n c r e t e s having compressive s t r e n g t h s o f from 2500 t o 16,500 ps i (17 . 2 t o 113. 8 MPa) w e r e cast and tested u s i n g either unbonded caps o r s u l f u r mor ta r caps, and the resu l t s w e r e compared. The effect o f r e s t r a i n i n g r i n g dimensions on test r e s u l t s w a s a l s o i n v e s t i g a t e d . I t w a s found t h a t t h e u s e of unbonded caps cou ld p rov ide a c l e a n e r , safer, and c o s t effective a l t e r n a t i v e t o s u l f u r mor ta r f o r capping c o n c r e t e c y l i n d e r s . However, p r i o r t o t h e acceptance of each unbonded capping system, c y l i n d e r s must be tested u s i n g t h e unbonded caps, and t h e r e s u l t s must be compared and c o r r e l a t e d w i t h : r e su l t s o b t a i n e d from companion c y l i n d e r s tested fo l lowing c u r r e n t ASTM C 39 and C 617 procedures .

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1538. Carrasquillo, P. M. and Carrasquillo, R. L., "EVALUATION OF THE USE OF CURRENT CONCRETE PRACTICE IN THE PRODUCTION OF HIGH-STRENGTH CONCRETE," ACI Materials Journal, Vol. 85, No. 1, Jan-Feb 1988, pp. 49-54.

A research program was conducted for the study of various quality-control procedures as applied to high- strength concrete. Over 1000 specimens for strength evaluation were cast from 29 high-strength concrete mixtures having compressive strengths ranging from 6000 to 14,500 psi at 28 days. Variables investigated included test specimen size, cylinder mold material, curing conditions, additions of superplasticizer, and cylinder capping method.

1539. Carrasquillo, P. M., "PULLOUT TESTS ON STRAIGHT DEFORMED BARS EMBEDDED IN SUPERPLASTICIZED CONCRETE," ACI Materials Journal, Vol. 85, No. 2, Mar-Apr 1988, pp. 90-94.

The bond performance of reinforcing steel embedded in superplasticized normal weight concrete was studied. Pullout tests were conducted on straight deformed bars having an embedded length of either 6 or 8 in. (152 or 203 mm). Variables studied were the slump of the concrete before and after the addition of the superplasticizer, the type of superplasticizer used, and the depth of fresh concrete cast under the pullout bars. To determine which properties of the concrete were affected by the addition of the superplasticizer and how these, in turn, affected the bond behavior of the reinforcing bars embedded in that concrete, several properties of the fresh and hardened concrete were tested. These included concrete slump, air content, temperature, bleed, compressive strength, and splitting tensile strength. The test results indicated that the effects of a sulfonated naphthalene formaldehyde condensate on fresh and hardened concrete properties were quite different from those of a sulfonated melamine formaldehyde condensate. However, in no case was the pullout capacity of straight deformed bars embedded in superplasticized concrete significantly less than that of bars embedded in the concrete containing no superplasticizer.

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1540. Cumming, N. A. and Seabrook, P. T., "QUALITY ASSURANCE PROGRAM FOR VOLUME-BATCHED HIGH- STRENGTH CONCRETE, 'I

10, NO. 8, 1988, pp. 28-32. Concrete International: Design and Construction, Vol.

The Alex Fraser Bridge, located near Vancouver, B. C. is the world's longest cable-stayed bridge, spanning 465 m (1526 ft. ).Large quantities of cast- in-place high-strength concrete were placed, of which 1055 m**3 (1380 yd**3) was 55 MFa (8000 psi) low- slump, volume-batched concrete used in the deck overlay. This article describes the quality assurance procedures, presents a statistical analysis of the test data, and compares the statistical performance of the volume-batched concrete to weight-batched, ready- mixed concrete of the same stren.gth class. (Author abstract). 3 Refs.

1541. Day, R. L. and Marsh, B. K., "MEASUREMENT OF POROSITY IN BLENDED CEMENT PASTES," Cement and Concrete Research, Vol. 18, No. 1, Jan 19m88, pp. 63-73.

Assessment of porosity was made by several methods on plain portland cement pastes and on those containing silica fume or fly ash. Water-solid ratio and proportion of pozzolan were varied to provide a wide range of porosities and pore structures. Measurements were made on specirens that had been cured a t 20 C f o r 7 days, 28 days, and 3 months, and at 35 C for 3 months. Porosity was assessed by mercury intrusion porosimetry; oven-drying; water, methanol, and propanol resaturation; and methanol and propanol exchange. Selected pastes were also analyzed by nitrogen sorption. The different methods give varying views of the pore structures of the materials examined. Conclusions about the pore structure can be made by comparing and contrasting results from the different methods. There are fundamental differences in the nature of the porosity in plain and blended cement pastes. Simpler, less expensive, methods than mercury porosimetry are available that produce useful estimates of porosity.

1542. Dhir, R. and Hubbard, F. et al., "CONTRIBUTION OF PFA TO CONCRETE WORKABILITY AND STRE,NGTH DEVELOPMENT,"

1988, pp. 277-289. Cement and Concrete Research, Vol. 18, No. 2, Mar

An assessment of the nature cf the components of pulverized-fuel ash (pfa) has shown a dominance of hollow, glassy spheres with a ccmposite shell. Total

2.32

or partial coating by magnetite can be present. The form, size and physical nature of the particles are shown to be the main influences affecting the workability and water demand of fresh pfa concretes. The relationship between progressive pfa particle reaction and strength gain with time has been observed for standard cured concretes up to two years old. The early pfa contribution to strength development is largely a beneficial interaction with the normal hydration of portland cement while the pozzolanic reaction becomes significant after 28 days. The potential performance of pfa can be predicted from a consideration of its fineness, as measured by 45 micro m sieve residue.

1543. Diamond, S. and Olek, J., "FLY ASH CONCRETE FOR HIGHWAY USE.," Final Report, Purdue University/Indiana State Highway Comm, Mar 1988, 363 p.

A series of investigations were carried out to examine the potential for routine use of fly ash in highway concrete, with special reference to Indiana. Existing methods of mix proportioning of fly ash concretes were reviewed in detail, and a new method developed to better assure good durability characteristics despite expected fluctuations in fly ash properties. Extensive investigations were carried out on the properties of concretes designed by this method and using representative Indiana fly ashes of both Class F and Class C varieties. In general these concretes exhibited compressive strengths and other mechanical properties at least as satisfactory as those of presently specified plain portland cement concretes, and the potential durability appeared to be significantly improved. The development of early flexural strengths was found to lag those of plain concretes somewhat, but after several months this lag disappeared. Provision of an adequate air content is necessary to assure freeze-thaw durability, and it was found that the necessary dosage of air entraining agent varied with the fly ash, but could be determined very easily by use of the foam index test. A number of technical conclusions were drawn with respect to reactions within the fly ash concretes, and a chapter on recommendations and cautions has been supplied.

233

1 5 4 4 .

1545.

E c k e r t , W . and C a r r a s q u i i l o , R. , "RECOMMENDATIONS FOR USING SUPERPLASTICIZERS FOR PROD3CING FLOWING CONCRETE I N HOT WEATHER., I n t e r i m Repor t , Texas U n i v e r s i t y , A u s t i n C e n t e r f o r T r a n s p o r t a t i o n Resea rch A u s t i n Texas, Jun 1988, pp. 242.

T h i s r e p o r t c o n s i s t s of r e s u l t s , o b s e r v a t i o n s , and c o n c l u s i o n s from an e x p e r i m e n t a l program i n v e s t i g a t i n g t h e effect o f s u p e r p l a s t i c i z e r s an fresh and ha rdened c o n c r e t e p r o p e r t i e s . T e s t s f o r w o r k a b i l i t y , a i r c o n t e n t , u n i t weight, s e t t i n g times, s t r e n g t h , and d u r a b i l i t y w e r e conducted f o r t h e mixes t h a t made up t h i s s t u d y . Variables f o r these mixes i n c l u d e d i n i t i a l slump, c o a r s e a g g r e g a t e t y p e , cement c o n t e n t , retarder dosage , t i m e o f a d d i t i o n , and admix tu re combina t ions . The r e s u l t s from t h i s s t u d y show t h a t s u p e r p l a s t i c i z e r s can p r o v i d e desirable characteristics f o r a c o n c r e t e m:Lx such as i n c r e a s e d w o r k a b i l i t y , i n c r e a s e d compress ive and f l e x u r a l s t r e n g t h s , and i n c r e a s e d r e s i s t a n c e t o a b r a s i o n . However, s u p e r p l a s t i c i z e r s can a l s o produce u n d e s i r a b l e and d e l e t e r i o u s characterist ics f o r a c o n c r e t e mix such as rapid slump lo s s , l o s s o f a i r , and d e l a y e d f i n i s h i n g due t o d e l a y e d s e t t i n g t i m e s . T h i s r e p o r t p r o v i d e s t h e resident : e n g i n e e r w i t h recommendations f o r p r o d u c t i o n of s u p e r p l a s t i c i z e d f l o w i n g c o n c r e t e and s u g g e s t i o n s f o r f u r t h e r r e s e a r c h . Resea rch s t u d y t i t l e : G u i d e l i n e s f o r P r o p e r U s e o f S u p e r p l a s t i c i z e r s and the E f f e c t o f Retempering Practices on Performance and D u r a b i l i t y of C o n c r e t e .

Feng, N.-Q. and Yang, H.-M. e t a:L., "STRENGTH EFFECT OF MINERAL ADMIXTURE ON CEMENT CONCRETE, 'I Cement and C o n c r e t e Research, V o l . 1 8 , N o . 3 , May 1988, pp. 464- 472.

P r e s e n t s t he s t r e n g t h effect o f t h e F m i n e r a l admix tu re (FMA), which i s made of t h e f i n e l y divided powder of n a t u r a l z e o l i t e r o c k ground w i t h a b i t o f o t h e r i n o r g a n i c mater ia l . T e s t r e s u l t s i n d i c a t e t h a t a c o n c r e t e mix w i t h 4 5 0 kg/(m**3) o f o r d i n a r y p o r t l a r t a cement ( O P C ) , 5 0 kg/(m**3) o f FMIi and W/C + FMA = 35 p e r c e n t can have a compress ive s t r e n g t h above 8 0 MPa, w h i l e t h e compress ive s t r e n g t h of t h e c o r r e s p o n d i n g c o n c r e t e mixing w i t h 500 kg/(m**:3) o f OPC i s o n l y 7 0 MPa. T e s t r e s u l t s a l s o conc lude t h a t , when a 5 t o 10 p e r c e n t of cement i n t h e c o n c r e t e i s displaced by FMA under t h e c o n d i t i o n of u s i n g s u p e r p l a s t i c i z e r (HRWR) and w / c = 0 . 3 1 t o 0.35, t he s t r e n g t h o f t h i s c o n c r e t e i s 1 0 t o 15 p e r c e n t higher t h a n t h a t o f t h e c o r r e s p o n d i n g c o n c r e t e mix w i t h p u r e OPC.

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I

1546. Foy, C. and Pigeon, M. et al., "FREEZE-THAW DURABILITY AND DEICER SALT SCALING RESISTANCE OF A 0.25 WATER- CEMENT RATIO CONCRETE, '' Cement and Concrete Research, Vol. 18, No. 4, July 1988, pp. 604-614.

Specimens of 0.25 water-cement ratio concrete with various air void spacing factors were tested for freeze-thaw durability in accordance with ASTM C 666 and for deicer salt scaling resistance in accordance with ASTM C 672. All specimens were moist-cured for 14 days. Few specimens showed signs of deterioration after 300 and 800 cycles of freezing and thawing and a critical air void spacing factor of approximately 750 um was determined. All specimens that underwent scaling tests showed a very good resistance to deicer salts and, even after 150 cycles, a maximum of only 0.6 kg/(m**3) of scaled off particles was measured.

1547. Gardner, N. J. and Sau, P. L. et al., "STRENGTH DEVELOPMENT AND DURABILITY OF CONCRETES CAST AND CURED AT 0 C," ACI Materials Journal, Vol. 86, No. 6, Nov- Dec 1988, pp. 529-536.

Describes an experimental investigation into the strength development of CSA Types 10 and 30 (ASTM Types I and 111) cement concretes and the durability of CSA Type 30 cement concretes, cast and cured at 0 C in seawater relative to conventionally cast and cured concretes. All concretes incorporated air-entraining admixtures and had plastic air contents of between 4 and 6 percent. Strength development of all concretes with temperature is dependent upon the water- cementitious ratio. Low-temperature casting and curing is not necessarily detrimental to the strength development of low water-cement ratio concretes. The resistance to freezing and thawing of air-entrained Type 30 cement concretes of water-cement ratios below 0.50 is excellent regardless of casting and curing temperature.

1548. Giaccio, G. and Malhotra, V., "CONCRETE INCORPORATING HIGH VOLUMES OF ASTM CLASS F FLY ASH," Cement, Concrete, and Aggregates, Vol. 10, No. 2, 1988, pp. 88-95.

The results are given of a study to develop additional data on mechanical properties, and freezing and thawing resistance of high-volume Class F fly ash concrete made with ASTM Types I nd I11 cements. A series of 8 concrete mixtures involving 12 batches were studied. Details are given of the volume, water-

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t o -cemen t i t i ous matrials r a t i o , f l y ash r a t i o , and t h e cement con ten t . A l l mix tures were a i r - e n t r a i n e d and s u p e r p l a s t i c i z e d . T h e mix tures i n c o r p o r a t e d Type I and Type I11 cements, vari.ous combinations o f as- recieved f l y ash, benef ic i .a ted f l y ash, and condensed s i l i c a fume. From t h e tes t resclts, it is concluded t h a t high-volume f l y ash conc re t e has e x c e l l e n t mechanical properties and satisfactory r e s i s t a n c e t o repeated c y c l e s of f reezing and thawing. T h e u s e of ASTM Type I11 cement appears t o be e s s e n t i a l when hig:h s t r e n g t h a t e a r l y ages a r e r equ i r ed . For c o n c r e t e s made w i t h ASTM Type I cement, the u s e o f b e n e f i c i a t e d f l y ash, and b e n e f i c i a t e d f l y ash and condensed s i l i c a fume, does l i t t l e t o enhance t h e p r o p e r t i e s o f c o n c r e t e compared w i t h ' a s received' f l y ash. For c o n c r e t e made w i t h ASTM Type 111: cement, t h e b e n e f i t s o f u s i n g b e n e f i c i a t e d C las s F f l y a s h and condensed s i l i ca fume are not c l e a r .

1549. Gjorv, 0. E . , "HIGH-STRENGTH CONCRETE, " Nordisk Betong (Stockholm), V o l . 32, No. 1, 1988, pp. 5-9.

E x i s t i n g c o n c r e t e codes have been a l i m i t i n g f a c t o r f o r s t r u c t u r a l u t i l i z a t i o n of h igh - s t r eng th concrete.. I n Norway, however, a new c o n c r e t e code i s under p r e p a r a t i o n t o permit t h e u t i l i z a t i o n of h igh - s t r eng th c o n c r e t e up t o 1 0 5 ma f o r s t r u c t u r a l a p p l i c a t i o n s . For grades of c o n c r e t e above t h i s level, r e c e n t i n v e s t i g a t i o n s have demonstrated a great p o t e n t i a l f o r a p p l i c a t i o n s of c o n c r e t e w h e r e high a b r a s i o n r e s i s t a n c e i s impor tan t .

1550. Gutmann, P . F., ''BUBBLE CHARACTERISTICS AS THEY PERTAIN TO COMPRESSIVE STRENGTH AND FREEZE-THAW DURABILITY," ACI M a t e r i a l s Jou rna l , V o l . 85, No. 5, Sept-Oct 1988, pp. 361-366.

Known air-entraining additives are not entirely s a t i s f a c t o r y w i t h r e s p e c t t o t h e s t a b i l i t y o f t h e a i r bubbles i n c o n c r e t e and have a tendency t o e i t h e r l o s e a i r o r i n c r e a s e a i r as mixing t i m e i s extended. Another d i sadvantage is t h e r e d u c t i o n of compressive s t r e n g t h s of a 1 0 pe rcen t s t r e n g t h l o s s per 1 p e r c e n t i n c r e a s e i n e n t r a i n e d a i r . I t :is believed t h a t t h i s l o s s i s due i n p a r t t o i r r e g u l a r bubble s i z i n g and the coa lescence of bubbles i n t he mix caus ing large v o i d s t h a t reduce t h e compressive s t r e n g t h . T h e o b j e c t of t h i s research program w a s t o improve the a i r - e n t r a i n e d p o r t l a n d cement conc re t e , which inc luded an addi t ive t h a t would e n t r a i n an a i r - v o i d system having d e s i r a b l e characterist ics when used over i i wide dosage range and, a l s o , have a s u p e r i o r dosacge response r e l a t i v e t o

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similar known additives. Another objective of this research program was to provide improved strength results that include an additive that entrains an air- void system and increases compressive strengths over known air-entraining agents. Microscopic examination of a methyl ester-derived Cocamide diethanolamine produced bubbles that were spherical, having thick walls with no coalescence, while wood-resin bubbles were relatively thin-walled and tended to be less than spherical with some shapes oblong and coalescence observed. It was believed that this difference would produce a more stable air content and more uniform bubble structure in portland cement concrete. Test results on concrete with the use of a Cocamide diethanolamine produced by a methyl ester process produced a stable volume of air having the desirable size and distribution, and, compared to known air- entraining agents, increased the resistance to freeze- thaw durability by 400 percent and increased compressive strengths 25 percent in early ages and 10 percent in later ages.

1551. Hague, M. and Day, R. L. et al., "REALISTIC STRENGTH OF AIR-ENTRAINED CONCRETES WITH AND WITHOUT FLY ASH," ACI Materials Journal, Vol. 85, No. 4, July-Aug 1988, pp. 241-247.

Effects of various curing regimes on the strength development of both plain and fly ash concretes were studied. Three grades of air-entrained concretes with 28 day nominal strengths of 20, 30, and 40 MPa (2900, 4350, and 5800 psi) were cast. For each grade, 0, 20, 35, and 50 percent of the weight of cement was replaced by two subbituminous fly ashes. Cylinders were cured at 100 and 50 percent relative humidities and under outdoor ambient conditions - including a Canadian winter climate. Structural-size members were also exposed to the elements and strength was estimated by testing extracted cores. indicate exposure of test cylinders to site conditions does not adequately reflect strength development of the in situ concrete; this is particularly so if test cylinders are allowed to dry. Prediction of in situ strength from site-cured cylinders is particularly inaccurate for the fly ash concretes. For in situ concretes with a low total cementitious content, the inclusion of fly ash in appreciable quantities is likely to result in slower strength gain than plain concrete. However, for higher grade concretes (higher total cementitious content) even with high ash content, early exposure to the elements is no more detrimental than it is to plain concrete.

Results

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1552. Ho, D . W. S . and L e w i s , R . K . , "SPECIFICATION OF CONCRETE FOR REINFORCEMENT PROTECTION - PERFORMANCE CRITERIA AND COMPLIANCE BY STRENGTH," Cement and Concrete Research, Vol. 18 , No. 4 , J u l y 1988, pp. 584- 594.

The c u r r e n t practice of s p e c i f y i n g c o n c r e t e f o r re inforcement p r o t e c t i o n i s o f t e n c a l c u l a t e d by t h e s t a n d a r d 28-day compressive s t r e n g t h , water-cement r a t i o , and cement c o n t e n t . However, t h i s form o f s p e c i f i c a t i o n may lead t o m i s i n t e r p r e t a t i o n . Paper o f f e r s an a l t e r n a t i v e approach based on performance cr i ter ia w i t h t he q u a l i t y of c o n c r e t e expres sed i n terms o f w a t e r s o r p t i v i t y and ca rbona t ion . T h e u se of minimum 28-day s t r e n g t h s as deemed-to-comply v a l u e s f o r these c r i te r ia i s a l s o d i scussed .

1553. Horiguchi , T . and S a e k i , N . e t a l . , "EVALUATION OF PULLOUT TEST FOR ESTIMATING SHEAR, FLEXURAL, AND COMPRESSIVE STRENGTH OF FIBER REINFORCED S I L I C A FUME CONCRETE," ACI Materials Journa l , V o l . 85, No. 2 , Mar- A p r 1988, pp. 126-132.

T h e u s e o f p u l l o u t s t r e n g t h o f steel f iber r e i n f o r c e d c o n c r e t e (SFRC) t o e v a l u a t e t h e shear f l e x u r a l and compressive s t r e n g t h of SFRC c o n t a i n i n g a condensed s i l i c a fume i s d i scussed . F i r s t , t h e effect o f f iber re inforcement and s i l i c a fume a d d i t i o n on p u l l o u t s t r e n g t h w a s i n v e s t i g a t e d w i t h d i f f e r e n t apex a n g l e s of t h e c o n c r e t e f rus t rum. Then t h e c o r r e l a t i o n s between t h e p u l l o u t s t r e n g t h o f steel f iber r e i n f o r c e d c o n c r e t e and shear s t r e n g t h s w e r e o b t a i n e d f o r three types o f s h e a r t es t methods. I n a d d i t i o n , compressive s t r e n g t h and f l e x u r a l s t r e n g t h were a l s o c o r r e l a t e d w i t h t h e p u l l o u t s t r e n g t h . T h e t e s t r e s u l t s show t h e a d d i t i o n of f iber re inforcement and s i l i c a fume s i g n i f i c a n t l y improves t h e p u l l o u t s t r e n g t h . The r e g r e s s i o n a n a l y s i s of t h e t e s t data shows t h a t a c l o s e c o r r e l a t i o n e x i s t s between the shear s t r e n g t h s and t h e p u l l o u t s t r e n g t h o f t h e steel f iber r e i n f o r c e d c o n c r e t e . The magnitude of p u l l o u t s t r e n g t h i s found t o be approximately t he same o r d e r as t h a t of i n d i r e c t s h e a r s t r e n g t h .

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1554. Hover, K. C., "ANALYTICAL INVESTIGATION OF THE INFLUENCE OF AIR BUBBLE SIZE ON THE DETERMINATION OF THE AIR CONTENT OF FRESHLY MIXED CONCRETE," Cement, Concrete, and Aggregates, ASTM, Vol. 10, No. 1, Summer 1988, pp. 29-34.

It has been qualitatively suggested that the pressure method for the determination of air content in freshly mixed concrete can be in error when a portion of the entrained air bubbles becomes relatively incompressible due to the increase in internal bubble pressure that accompanies a reduction in bubble diameter. This has been used to explain the observed discrepancy between air meter readings and the air volume reported by microscopic analysis. This paper reports the results of an analytical investigation of the bubble-size effect, in which it is seen that it is unlikely that a sufficient volume of bubbles with the required diameter are present so as to cause the observed discrepancy. In order to demonstrate a significant influence of bubble size on the accuracy of the air meter, one must resort to values for the surface tension of the bubble film, which ae unjustified. The characteristics of various meters are discussed.

1555. Hughes, B. P. and Mahmood, A. T., "INVESTIGATION OF EARLY THERMAL CRACKING IN CONCRETE AND THE RECOMMENDATIONS IN BS 8007," Structural Engineer (London), Vol. 66, No. 4, Feb 1988, pp. 61-69.

All concrete structures expand and then contract because of the evolution of the heat of hydration and consequent rise and fall in temperature. If the contraction from the peak temperature is restrained, tensile stresses are induced, which can cause cracking. The present investigation aims to reproduce site conditions for early thermal cracking within the laboratory to provide accurate data that can assist in the control of such cracking in practice. The validity of the theoretical analyses and the theory as assumed in BS 8007 are also checked against the experimental results.

1556. Hughes, B. P. and Mahmood, A. T., "LABORATORY INVESTIGATION OF EARLY THERMAL CRACKING OF CONCRETE," ACI Materials Journal, May-June 1988, pp. 164-171.

High-temperature gradients can occur in all concrete structures as the heat of hydration of the freshly placed concrete is liberated, and cracking can

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result at the surface. Problems, due to the tensile stresses and cracks that are induced by the temperature gradients can be especially severe for thick concrete sections. The present investigation aims to reproduce conditions for early thermal movements in the laboratory site! and to study their effects and possible control.

1 5 5 7 . Janssen, D . J., "LABORATORY PEEWEABILITY MEASUREMENT, '' Permeability of Concrete, ACI SE'-108, a, 1 9 8 8 , pp. 145-158 .

Equipment and procedures for measuring actual permeability of portland cement concrete are presented. The equipment is bui.1t from readily available parts and materials and requires only standard laboratory air pressure and vacuum sources. The sample size used is 3 in. ( 7 . 5 cm) diameter x 3- 1 / 8 in. ( 8 cm) long, but other sample sizes could be used. Typical measurements are presented to show repeatability and time required for permeability testing. The equipment has been used for permeabilities as low as 1 x (lo**-11) cm/sec. Concrete with lower permeability would require equipment modifications and/or I-onger measurement times.

1 5 5 8 . Jennings, H. M. , "DESIGN OF HIGH STRENGTH CEMENT BASED MATERIALS: PART 3 STATE OF THE ART, Materials Science and Technology, V o l . 4, No. 4, Apr 1 9 8 8 , pp. 291-300.

Some of the new materials that are used for both construction and highly specialized small scale application are described. As far as possible, explanations for improved properties are based on the microstructure and fracture mechanics of the material. Discussion is focused mainly on experimental results and relationships that are used in practice.

1 5 5 9 . Jennings, H. M . , "DESIGN OF HIGH STRENGTH CEMENT BASED MATERIALS: PART 2 MICROSTRUCTUR13,11 Materials Science and Technology, Vo1.4, No.4, Apr 1 9 8 8 , pp. 285-290.

The microstructure of cement based materials is examined with a view to establishing relationships between microstructure and strength. Porosity of cement is perhaps the most important feature, but the other phases and aggregate are i I l S O examined. Present. classification systems for both porosity and microstructure of the solid phases cannot be related directly to strength, but several microstructural

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f e a t u r e s t h a t probably c o n t r o l s t r e n g t h have been i d e n t i f i e d .

1560. Jennings , H. M., "DESIGN OF H I G H STRENGTH CEMENT BASED MATERIALS: PART 1 FRACTURE MECHANICS., I' M a t e r i a l s Sc ience and Technology, Vo1.4, No.4, Apr 1988, pp. 277-284.

Aspects of high s t r e n g t h cement based materials a r e described w i t h a view towards e s t a b l i s h i n g r e l a t i o n s h i p s between m i c r o s t r u c t u r e and p r o p e r t i e s . The t h e o r y of f r a c t u r e t h a t may be a p p l i e d t o d e s i g n i n g h igh s t r e n g t h m a t e r i a l s i s d i scussed . Cement paste, conc re t e , and f ib re r e i n f o r c e d cement based materials are cons ide red i n terms of some of t h e f r a c t u r e mechanics parameters .

1561. Jones, K . , "EVALUATION O F TYPE I CEMENT FAST TRACK CONCRETE., " F i n a l Report , Iowa Department o f T ranspor t a t ion , O c t 1988, pp. 20.

There are p r o j e c t s where opening t h e pavement t o t r a f f i c i n less t h a n the 5 t o 7 days i s needed, b u t an 8 t o 12 hour opening t i m e i s n o t necessary . T h e s tudy examined f a s t track conc re t e w i t h Type I cement and admixtures . The variables s t u d i e d were: c u r e tempera ture ; cement brand; a c c e l e r a t o r s ; and w a t e r r e d u c e r s . A s t a n d a r d water reducer and c u r i n g b l a n k e t s appear t o be effective a t producing a 24 hour t o 36 hour opening s t r e n g t h . An a c c e l e r a t o r and/or high range water reducer may produce opening s t r e n g t h i n 12 t o 24 hours . Calcium c h l o r i d e w a s most effective a t ach iev ing high-early s t r e n g t h .

1562. Jones, K., "EVALUATION OF TYPE I CEMENT FAST TRACK CONCRETE. FINAL REPORT," Iowa Department of T r a n s p o r t a t i o n , O c t 1988, pp. 20.

There are p r o j e c t s where opening the pavement t o t r a f f i c i n less t h a n the 5 t o 7 days is needed, b u t an 8 t o 12 hour opening t i m e i s no t necessary . The s tudy examined f a s t t rack conc re t e w i t h Type I cement and admixtures . The variables s t u d i e d w e r e : c u r e tempera ture ; cement brand; acce1era tors ;and water r e d u c e r s . A s t a n d a r d water reducer and c u r i n g b l a n k e t s appear t o be effective a t producing a 24 hour t o 36 hour opening s t r e n g t h . An a c c e l e r a t o r and/or high range water r educe r may produce opening s t r e n g t h i n 12 t o 24 hours . Calcium c h l o r i d e was most effective a t a c h i e v i n g high-early s t r e n g t h .

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1563. Kaetzel, L. J. and Clifton, J. R., "MAINTENANCE AND IMPLEMENTATION OF AN EXPERT SYSTEM FOR DURABLE CONCRETE," Computer Applications in Concrete Technology - San Antonio, ACI SP-106, a, 1988, pp. 75- 86.

Describes an expert system with a knowledge base consisting of freeze-thaw, sulfate, alkali-aggregate, and corrosion aspects of concrete durability. The system was developed on a microcomputer using an expert-system shell facility. This paper discusses knowledge acquisition, knowledge representation, issues relating to the maintenance of expert systems, and recommendations for field irplementations.

1564. Khaloo, A. R. and Ahmad, S. H., "BEHAVIOR OF NORMAL AND HIGH-STRENGTH CONCRETE UNDER. COMBINED COMPRESSION- SHEAR LOADING," ACI Materials Jcurnal, Vol. 85, No. 6, Nov-Dec 1988, pp. 551-559.

Eighty solid cylindrical 3 multiplied by 9-in. (76.2 multiplied by 152.4-mm) specimens using normal and high-strength concrete were tested under uniaxial compression, shear shear-compression, and compression- shear loadings to determine strength and behavior of concrete under these loading paths. The effects of stress path on the behavior of concrete under fombined compression shear were studied. For shear-compression loading, the effect of shear on the compressive stress-strain curves was to redLce the peak stress and to increase the strain correspocding to peak stress, as the magnitude of applied shea.r increased. The experimental results for compres,sion-shear loading are compared with a strength criteri.on based on all three stress invariants and the comparison is judged good.

1565. Klieger, P., "CONCRETE: THE CHANGING SCENE," Construction Specifier, Vol. 41, No. 12, Dec 1988, pp. 36-42.

The author reviews a number of significant changes in the utilization of materials and techniques to provide concretes with enhanced performance. Topics discussed include advances in chemical admixtures, hydraulic cements and materials supplementary to cement, including fly ash, blast.-furnace slag, silica fume and polymers. The author also discusses advances in reinforcement, including epoxy-coated steel bar reinforcement and fiber reinforcement, advances in handling and placing and advances in quality control and quality assurance.

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1566. Koch, R. and Wohlfahrt, R., "EFFECT OF ADMIXTURES IN CONCRETE ON THE BOND BEHAVIOR OF GALVANIZED REINFORCING BARS (IN GERMAN AND ENGLISH)," Betonwerk und Fertigteil-Technik (Wiesbaden), Vol. 54, No. 3, Mar 1988, pp. 64-68.

In general, the reinforcement in reinforced concrete is protected against corrosion by the concrete surrounding it. Under the action of chlorides and sulfides, however, highly alkaline concrete may lose its protective effect, and penetration of carbon dioxide from the air can lower the alkalinity of the concrete (carbonation) and make corrosion possible. Structures in or close to seawater, industrial and traffic engineering structures, and generally any structural component in which the depth of concrete cover to the steel is inadequate will therefore more particularly be at risk. To provide better corrosion protection in these critical cases, the use of galvanized reinforcement may be considered among other corrosion protection measures. Several pullout tests were performed to determine what effect admixtures in concrete have upon bond behavior. Because of the large number of approved admixtures commercially available, the tests were confined to admixtures containing six frequently used active ingredients.

1567. Lee, G. C. and Shih, T. S. et al., "MECHANICAL PROPERTIES OF HIGH-STRENGTH CONCRETE AT LOW TEMPERATURE," Journal of Cold Regions Engineering, Vol. 2, No. 4, 1988, pp. 169-178.

This paper presents the results of an experimental study on the mechanical properties of high-strength concrete in the temperature range between plus or minus 20 degree C and minus 70 degree C without considering the effect of freezing cycles. Test results show that the values of compressive and splitting tensile strength, modulus of elasticity and Poisson's ratio increase as the temperature decreases. The ratio of bond strength at low temperature and the bond strength at normal temperature are generally larger under reversed cyclic loading than under monotonic or repeated cyclic loading. The rate of increase in compressive and splitting tensile strength, Young's modulus, local bond strenth and Poisson's ratio for high-strength concrete at corresponding different low temperatures is generally lower than that for normal strength concrete.

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1568. Luke, K. and Glasser, F. I ? . , "INTERNAL CHEMICAL EVOLUTION OF THE CONSTITUTION OE' BLENDED CEMENTS," Cement and Concrete Research, V o 1 . 18, No. 4, July 1988, pp. 495-502.

Blends comprising 30 percent of either fly ash or blast furnace slag and 70 percent ordinary portland cement have been aged up to two years at 25, 40, and 55 C in C(O**2)-free conditions. Changes in their mineralogy were determined by selective dissolution, TG, x-ray diffraction, analytical electron microscopy, and Ca(OH)2 determinations on both whole samples and dissolution residues. Portland cements converge on a steady state, but blended cements, especially those with slags, show much evidence of persistent internal. inhomogeneity. Higher cure temperatures accelerate reaction but not necessarily in the same direction as at 25 C.

1569. Mangialardi, T. and Paolini, A. E., "WORKABILITY OF SUPERPLASTICIZED MICROSILICA-PORTLAND CEMENT CONCRETES, It Cement and Concrete Research, Vol. 18, No. 3 , May 1988, pp. 351-362.

The effect of the addition time of superplasticizers on the workability of concretes containing 0 or 10 percent microsilica was studied at different polymer dosages, water-cement ratios, and mixing times. Cement pastes were also prepared and examined for workability, zeta potential., and polymer adsorption. The water demand and the slump loss of the two types of concretes, as well as the dosage of superplasticizer, are significantly reduced when the addition of the polymer is delayed. Regardless of the addition time of the admixture, the difference in water demand between the two types of concretes is greatly reduced when the polymer dosage is above 2 percent by weight of cement. The data on cement pastes suggest that the delayed addition of superplasticizer might be assimilated to an immediate addition to a cement with a lower fineness.

1570. Marusin, S. L., "INFLUENCE OF SUPERPLASTICIZERS, POLYMER ADMIXTURES, AND SILICA FUME IN CONCRETE ON CHLORIDE ION PERMEABILITY," Permeability of Concrete,, ACI SP-108, a, 1988, pp. 19-34.

This paper summarizes the results of permeability studies that have been undertaken since 1979. The research used a test procedure developed during the NCHRP Project 12-19A, "Concrete Sealers for Protection

2 4 4

of Bridge Structures", which was reprinted in 1981 as NCHRP Report No. 244. This test method utilizes 10 cm concrete cubes, and chloride ion penetration is determined at 4 depths after 21 days exposure to 15 percent NaCl solution. The test results show that lowering of water-cement ratio in portland cement concrete or presence of superplasticizers, polymer admixtures, and silica fumes are able to significantly reduce concrete permeability.

1571. McLean, F. G. and Pierce, J. S., "COMPARISON OF JOINT SHEAR STRENGTHS FOR CONVENTIONAL AND ROLLER COMPACTED CONCRETE," Roller Compacted Concrete 11, Proceedings of the Conference, San Diego, CA, 1988, pp. 151-169.

Direct shear test data for parent material and bonded and unbonded jointed specimens of conventional and RCC (roller compacted concrete) are presented and compared. Results are discussed and recommendations made regarding shear strength values for lift joints in gravity dams constructed of RCC. Some discussion is presented on safety factors used in analyses.

1572. Mijnsbergen, J., "STRENGTH DEVELOPMENT OF CONCRETE WITH SILICA FUME (IN DUTCH)," Cement, Vol. 40, No. 5, May 1988, pp. 18-21.

A silica-fume, blast furnace slag cement concrete was used to construct a pressure pipe in South Holland, to obtain a high material strength combined with good sulfate and chloride resistance. After completion of the project, further research was done on the effect of temperature on the silica-fume addition. At 30 C, compressive strength was higher after 1 day's curing because of the addition; at 20 C, contributation to strength development was observed after 2 day's curing. At a curing temperature of 10 C, the silica-fume addition initially had a negative effect on the strength development, but positive effect was observed after 3 days.

1573. Mobasher, B. and Mitchell, T. M., "LABORATORY EXPERIENCE WITH THE RAPID CHLORIDE PERMEABILITY TEST." Permeability of Concrete, ACI SP-108, a, 1988, pp. 117-144.

The new rapid chloride permeability test, in which chloride ions are driven into concrete samples electrically over a 6-hr period, is becoming widely used and has been accepted as an American Association of State and Highway Transportation Officials (AASHTO)

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standard, T277. This paper summarizes the results of an extensive series of laboratory tests with the new method. Results of an interlaboratory test program provide single- operator and multilaboratory coefficients of variation suitable for use in a precision statement in the stand.ard versions of the

1574. Nagaraj, T. S. et al., llSUPER-PLIASTICIZED NATURAL RUBBER LATEX MODIFIED CONCRETES," Cement and Concrete Research, Vol. 18, No. 1, Jan 1488, pp. 138-144.

Polymeric admixtures modify the properties of the processed concrete. Ductility is one such property modification. This investigation deals with the development of a method to incorporate

1575. Nelson, E. and Carrasquillo, R. et al., "BEHAVIOR AND FAILURE OF HIGH-STRENGTH CONCRETE SUBJECTED TO BIAXIAL-CYCLIC COMPRESSION LOADING," Journal of American Concrete Institute, Vol. 85, No. 4, Jul 1988, pp. 248-253.

Static and cyclic tests were performed to determine the properties and behavior of plain high-strength concrete subjected to biaxial cyclic compression. The primary variables studied were the maximum stress level and the biaxial stress ratio. Other variables included the effect of stress range and moisture content in the concrete. For specimens tested in fatigue at maximum stress levels: below approximately 76 percent, results show failure: occurred at a higher number of load cycles as the bia.xia1 stress ratio decreased. Endurance limits for a fatigue life of two million cycles were found in the range of 47 to 52 percent of the uniaxial static compressive strength. The effect of cyling below the fatigue limit resulted in postfatigue specimens having an increase in uniaxial static strength of about 39 percent over the control specimens tested prior t.o fatigue loading. The data were evaluated by regression analysis to develop a biaxial compression envelope. The failure envelope represents the predicted fatigue life of high-strength concrete as a function of the applied stress ratio. The observed failure mode for hi.gh-strength concrete under biaxial cyclic loading is also described.

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1576. Ozyildirim, C. and Halstead, W., "RESISTANCE TO CHLORIDE ION PENETRATION OF CONCRETES CONTAINING FLY ASH, SILICA FUME, OR SLAG," Permeability of Concrete, ACI SP-108, a, 1988, pp. 35-62.

The effects of two pozzolanic admixtures, fly ash and silica fume, and a ground-granulated blast furnace slag on the chloride ion intrusion of concretes prepared with low water-to-cementitious material ratios (0.35 to 0.45) were investigated. Results of the rapid permeability test (AASHTO T 277) showed that the resistance of concrete to the penetration of chloride ions increases significantly as the water-to- cementitious material ratio is decreased for the same proportions of solid ingredients. Most concretes with pozzolans or slag exhibited higher resistance to chloride ion penetration than the control concretes containing portland cement as the cementitious material. Results of the 90-day ponding test (similar to AASHTO T 2591, which was conducted with 0.40 w/c concretes only, indicated minimal chloride content at depths below 3 / 4 in. (19 mm) for all the test concretes. Strength values for all concretes made with the pozzolans and slag at 90 days were in excess of 5000 psi (34.5 ma), which is satisfactory.

1577 . Ozyildirim, C. and Halstead, W., "RESISTANCE TO CHLORIDE ION PENETRATION OF CONCRETES CONTAINING FLY ASH, SILICA FUME, OR SLAG.," Final Report, Virginia Transportation Research Council, Feb 1988, pp. 40.

The effects of two pozzolanic admixtures, fly ash and silica fume, and a ground-granulated blast furnace slag on the chloride ion intrusion of concretes prepared with low water-to-cementitious material ratios (w/c) (0.35 to 0.45) were investigated. Results of the rapid permeability test (AASHTO T 277) showed that the resistance of concrete to the penetration of chloride ions increases significantly as the w/c is decreased for the same proportion of solid ingredients. Usually, concretes with pozzolans or slag exhibited higher resistance to chloride ion penetration than the control concretes containing portland cement as the cementitious material. Results of the 90-day ponding test (similar to AASHTO T 2591, which was conducted with 0.40 w/c concretes only, indicated minimal chloride content at depths below 3 / 4 in (19 mm) for all the test concretes. Strength values for all concretes made with the pozzolans and slag at 90 days were in excess of 5,000 psi (34 .5 MPa), which is satisfactory.

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1578. Pedersen, N. and Baerland, T., "'EVALUATION OF THE DURATION OF CONCRETE PAVEMENTS EIY ABRASION," NORCEM Cement, 1988,

The aim is to evaluate various concrete mix designs concerning strength class, type of cement, additives, aggregates (fine and coarse) and other possible matters influencing the duration of rigid pavements, especially in relation to the use of studded tires. A ring road testing machine has been built with four studded truck wheels running with a speed of 14-70 km/h upon 12 concrete elements, arranged in a circle of 6 m diameter. It is possihle to apply a load cf up to 5 tons on each wheel in order to increase abrasion. Abrasion, dry and wet:, is measured electronically by use of a bridge placed on fixed points on each element. The testing equipment so far has been used for evaluation of concrete mix designs for the new part of highway El8 in Vestfold, to be built this year, as well as for testing concrete mixes versus asphalt pavements regarding production of dust by abrasion.

1579. Perraton, D. and Aitcin, P. C. c?t al., "PERMEABILITIES OF SILICA FUME CONCRETE," Permeability of Concrete, ACI SP-108, a, 1988, pp. 63-84.

Water, chloride-ion, and air permeability of two series of silica fume and non-silica fume concretes having water-cementitious ratios of 0.4 and 0.5 were studied as well as that of a 0.24 water-cementitiousi ratio silica fume concrete. Silica fume dosage varied from 5 to 20 percent by weight of cement. The water permeability of concrete samples having water- cementitious ratios lower than 0.5 is so low that they can be considered impervious whether they contain silica fume or not. The chloride-ion impermeability provided by silica fume rivals that of latex for water-cementitious ratios of 0.4 to 0.5 and polymer-. impregnated concrete with a 0 . 2 4 w/c ratio. The two drying methods used in this research yielded a positive correlation between silica fume dosage and air permeability. Equal variations were observed for values of up to 10 percent, whereas at twenty percent, the increase was markedly sharper. The characterization of concrete permeability is not as simple as it appears. Sample preparation and fluid type can significantly affect the interpretation of the effect of an admixture such as silica fume.

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1580. Pessiki, S. P. and Carino, N. J., "SETTING TIME AND STRENGTH TO CONCRETE USING THE IMPACT-ECHO METHOD," ACI Materials Journal, Vol. 85, No. 5, Sep 10 1988, pp. 389-399.

Tests were performed to evaluate the feasibility of using the impact-echo method to determine setting time and to monitor strength development of concrete. In the impact-echo method, the test object is subjected to point impact and the surface displacement is monitored at a point adjacent to the impact. From the measured displacement waveform and the thickness of the object, the P-wave velocity is determined. Changes in the P-wave velocity with time reveal information about the development of mechanical properties as the concrete matures. Setting-times tests were made on concrete mixtures of two water-cement ratios both with and without set-controlling admixtures. It is concluded that the impact-echo method is a promising nondestructive technique for monitoring the development of mechanical properties in concrete from '

initial setting to ages of several days.

1581. Pons, G. and Ramoda, S. A. et al., "INFLUENCE OF THE LOADING HISTORY OF FRACTURE MECHANICS PARAMETERS OF MICROCONCRETE: EFFECTS OF LOW-FREQUENCY CYCLIC LOADING," ACI Materials Journal, Vol. 85, No. 5, Sep 10 1988, pp. 341-346.

The concepts of fracture mechanics permits us to formulate mathematical laws of crack propagation. Since the Griffith studies in 1920, this theory has been successfully applied to metallic materials. Its extension to concrete and mortar has held the attention of research workers for the last 10 years. This investigation will show the influence of loading history on the resistance to crack growth in concrete by means of fracture mechanics parameters: the strain energy release rate and the stress intensity factor. This experimental investigation relates to the behavior of plain microconcrete notched beams subjected to repeated or stationary flexural stresses. The damage and consolidation phenomena have been ascertained, and the evolution of the ductility has been analyzed.

1582. Ravina, D. and Mehta, P. K., llCOMPRESSIVE STRENGTH OF LOW CEMENT/HIGH FLY ASH CONCRETE," Cement and Concrete Research, Vol. 18, No. 4, July 1988, pp. 571-583.

with fly ash on the compressive strength of lean The effect of replacing 35 to 50 percent of cement

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c o n c r e t e mixtures (350 lb./yd**3; 210 kg/m**3) w a s i n v e s t i g a t e d , u s i n g two ASTM C l a s s F and two ASTM C l a s s C f l y ashes. T h e t es t r e s u l t s showed t h a t , p a r t i c u l a r l y i n l e a n conc re t e , f l y ash has s i g n i f i c a n t effects on t h e p r o p e r t i e s of f r e s h and hardened concrete. Paper evaluates t h e effect of f l y a s h on t h e compressive s t r e n g t h development of t h e hardened c o n c r e t e . T e s t r e s u l t s show t h a t , compared w i t h t h e r e f e r e n c e mix t h a t reached t h e r e q u i r e d s t r e n g t h ( 2 0 0 3 p s i ; 1 4 MPa) a t 28 days, t.he c o n c r e t e s w i t h t h e f l y a s h replacement levels j u s t mentioned reached s t rengt :h a t 35 t o 1 7 0 days, depending on the replacement pe rcen tage and the p r o p e r t i e s of' f l y ash. From t h e s t a n d p o i n t of c o n c r e t e behavior , t h e u s e of a large amount of f l y ash, as rep lacemer t f o r b o t h cement and sand, i s h i g h l y b e n e f i c i a l .

1583. Robison, R. , "HIGH STRENGTH H I G H R I S E , " C i v i l Engineering(New York), V o l . 58, N o . 3, Mar 1988, pp. 62-65.

P u b l i c a t i o n Year: 1988 CODEN: CIEGAG ISSN: 0009- 7853 Chicago w i l l be t h e p l a c e f o r a 1 1 0 m i l l i o n s t r u c t u r e t h a t seems t o i n c o r p o r a t e most o f t h e 1980s e n g i n e e r i n g innova t ion and post-modern a r c h i t e c t u r e . I t w i l l be completed i n t i m e f o r t h e new decade, January 1990. S t a r t i n g a t t h e t o p , t h e 959 f t h e i g h t makes it t h e world 's t a l l e s t c o n c r e t e b u i l d i n g - t h e s i x t h Chicago s t r u c t u r e t o c a r r y t h a t t i t l e . The up- down c o n s t r u c t i o n method al lowed the c o n t r a c t o r t o excava te two of t h e t h r e e below--grade p a r k i n g levels w h i l e the tower frame was under way. T h i s 1980s innova t ion has become s t a n d a r d procedure on many si tes where convent iona l excavat ion could d i s t u r b ne ighbor ing s t r u c t u r e s . Other t e c h n i c a l advances i n c l u d e a pos t - tens ioned f l o o r s y s t e m and u s e o f m i c r o s i l i c a i n t h e c o n c r e t e mix t o produce ve ry h i g h s t r e n g t h s . From t h e foundat ion t o t h e 1 5 t h f l o o r , columns are 1 2 , 0 0 0 p s i ; t h e n t h e s t r e n g t h decreases g r a d u a l l y , t opp ing o f f a t 6000 p s i .

1584. Rodway, L. E . , "EFFECT O F AIR-ENTRAINING AGENT ON AIR- VOID PARAMETERS OF LOW- AND HIGH-CALCIUM FLY ASH CONCRETES, Cement, Concrete, arid Aggregates, Vol. 1 0 , No. 1, Summer 1988, pp. 35-38.

Five f l y ashes w i t h widely va ry ing l i m e c o n t e n t s from three c o u n t r i e s w e r e used f o r 25 p e r c e n t o f t h e cement by mass i n i d e n t i c a l c o n c r e t e mixes, inc1udin.g t h e same q u a n t i t y o f a i r - e n t r a i n i n g agent i n each case. T h e hardened conc re t e r e s u l t e d i n a s a t i s f a c t o r y

air-void system in terms of freeze-thaw resistance, regardless of the lime content of fly ash.

1585. Saito, M., "TENSILE FATIGUE STRENGTH OF THE MORTAR- AGGREGATE BOND, '' Cement and Concrete Research, Vol. 18, No. 5, Sept 1988, pp. 710-714.

The cement- or mortar-aggregate bond is an important factor that influences strength or durability of concrete. Various studies on bond strength have been conducted under static loading conditions, but there are no reports on the characteristics of the bond under repeated loading conditions. Tensile fatigue tests of the bond give information relating to cracking at the mortar- aggregate interface in concrete subjected to repeated tensile stresses. The results of microcrack observations have suggested that bond cracking at the interface plays a role in the beginning of failure of a concrete system under repeated tensile loading. The objectives of this study were to investigate the S-N relationship and the fatigue strength of the mortar- limestone bond under repeated tensile loading by using a friction grips method. Tensile fatigue tests of the mortar-limestone bond were carried out by applying direct tensile loads to the composite specimens using the friction grips. Test results were statistically analyzed to obtain the relationship between stress level and fatigue life for a 50 percent probability of failure. The relationship obtained gave the fatigue bond strength of 74.9 percent of the static bond strength for 2 million cycles.

1586. Schonlin, K. and Hilsdorf, H. K., "PERMEABILITY AS A MEASURE OF POTENTIAL DURABILITY OF CONCRETE - DEVELOPMENT OF A SUITABLE TEST APPARATUS," Permeability of Concrete, ACI SP-108, 1988, pp. 99- 116.

For the determination of the permeability on concrete discs, a rapid test method has been developed. No special devices are required to fix the test apparatus to the specimen. Air permeability of the concrete can be measured within a period of about 15 min. Laboratory experiments show a close correlation between the measured permeability coefficient and the duration of curing, type of cement, w/c ratio and the content of fly ash.

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1587. Seabrook, P. I. and Wilsori, H. S., "HIGH STRENGTH LIGHTWEIGHT CONCRETE FOR USE IN OFFSHORE STRUCTURES: UTILISATION OF FLY ASH AND SILICA FUME," International Journal of Cement Composit.es and. Lightweight Concrete, VOl. 10, NO. 3, Aug 1988, pp. 183-192.

Construction demands have raised design expectations of lightweight portland cement concrete. Paper presents results of the second phase of a three- phase program and consists of 162 trial mixtures using coarse aggregates from three sources, two chemical admixture systems, three levels of fly ash replacement, and three levels of silica fume replacement. It is concluded that 91 day compressive strengths of the order of 65 MPa are attainable in lightweight concrete, although this is the threshold level of the aggregates. Further, it is concluded that a nominal increase in strength occurs with Type F fly ash replacement, and that retarded early-strength gain caused by extended window superplasticizers poses a potential impediment to early strength. Silica fume additions resulted in significant strength increases. The minimum unit weight achieved. was 2000 kg/(m**3).

1588. Shaeles, C. and Hover, K., "INFLUENCE OF MIX PROPORTIONS AND CONSTRUCTION OPERATIONS ON PLASTIC SHRINKAGE CRACKING IN THIN SLABS," ACI Materials Journal, Vol. 85, No. 6, Nov 1988, pp. 20.

Plastic shrinkage cracking in. mortar panels, simulating cracking in concrete slabs, was investigated using the procedure developed by Kraai. For the specific conditions of the testing program, the incidence of plastic shrinkage cracking increased with the paste volume fraction. It was also observed that the orientation and severity of the cracks were influenced more strongly by the direction and speed of strikeoff operations than for all other variables studied. While it is believed that some threshold evaporation rate is necessary to initiate cracking, for the tests conducted there wa.s no direct correlation between the severity of the cracking and the rate of evaporation.

1589. Shih, T. and Lee, G. et al., "MECHANICAL PROPERTIES OF HIGH-STRENGTH CONCRETE AT LOW TEMPERATURE," Journal of Cold Regions Engineering, Vol. 2, No. 4, 4 Dec 1988, pp. 169-178.

The paper compares the test results for the high- strength concrete with those of normal strength

concrete under otherwise identical testing conditions. Details of the experimental program and results are given. It was found that for high-strength concrete with water cement ratio of 0.35 the compressive strength increases uniformly as the temperature decreases. The value of increase in concrete Young's modulus at low temperature is much less profound than that for the compressive strength. The rate of increase in splitting tensile strength at low temperature is uniform and relatively close to that of Young's modulus based on the ACI code. These and other findings are discussed.

1590. Shih, T. and Leem, G. et al., "HIGH-STRENGTH CONCRETE- STEEL BOND BEHAVIOR AT LOW TEMPERATURE," Journal of Cold Regions Engineering, Vol. 2, No. 4, Dec 1988, pp. 157-168.

The local behavior of reinforced high-strength concrete specimens under monotonic, repeated cyclic, and reversed cyclic loadings were studied. The temperature variable used was between 20 deg C and -70 deg C. The experimental results for the high-strength concrete are presented and are compared with those for the normal strength concrete reported in an earlier paper. The observations of the study are listed and discussed. It was found that under monotonic loading the stiffness of the initial loading curve of the bond stress-slip relationship under low temperature is almost the same as that under normal temperature. Other observations relate to the 'leaping' at the end of the linear stiffness range in the bond stress-slip curve, values of the maximum bond stress under monotonic loading, and the measure of ductility, etc.

1591. Shirley, S. and Burg, R. et al., "FIRE ENDURANCE OF HIGH-STRENGTH CONCRETE SLABS," ACI Materials Journal, Vol. 85 No. 2, Mar 1988, pp. 102-108.

In recent years, use of high-strength concrete ranging in compressive strength from 8000 to 15,000 psi has become more prevalent. such as high-rise buildings, are now using these materials. Most recently, the use of silica fume as a supplementary cementitious material has developed for design of higher strength concrete mixtures. The objective of this investigation was to develop fundamental information on the behavior of high- strength concrete at elevated temperatures using realistic test specimens. Scope of the work included a review of available literature on performance in fire tests of specimens fabricated fron high-strength

Concrete structures,

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concrete mixtures, with and without silica fume. The literature review was followed by laboratory tests of 3 x 3 x 0.33 ft slab specimens with embedded reinforcement. Specimens were exposed to elevated temperatures and monitored for temperature rise and physical integrity. Test:; were conducted at the Fire/Thermal Technology Section of Construction Technology Laboratories, Inc. (CTL) . Results of fire tests performed on the slab specimens show no measurable difference in performance of high-strength concretes and conventional strength concretes.

1592. Sprinkel, M. M., "PREDICTING PLASTIC SHRINKAGE CRACKING LMC OVERLAYS, 'I Concrete Construction, Vol. 33, NO. 7, Jul 1988, pp. 672-674.

Plastic shrinkage cracking is a potential problem when latex-modified concrete (LMC) is placed on a dry, windy day. LMC has a lower water content than conventional concrete so it bleeds less. Because plastic cracking is caused by evaporation rate exceeding bleeding rate, LMC's low bleeding rate makes plastic cracking more likely. To avoid the problem, contractors must be able to pred.ict when it's likely to occur so they can take steps to prevent it. Whenever temperature, relative humidity, and wind conditions are such that evaporation rate exceeds the critical 0. 1 value, contractors should be especially careful.

1593. Sprinkel, M. M., "HIGH EARLY STRENGTH LATEX MODIFIED CONCRETE," Concrete Construction, Vol. 33, No. 9, Se:p 1988, pp. 831-836.

Describes a trial installation of a high-early- strength latex-modified concrete (LMC) overlay on a highway bridge deck. The goal was to develop an LMC overlay that can be subjected to traffic in less than a day. Compressive strength reached 3000 psi in 24 hr or less. Shear bond strength and permeability also were tested and compared favorably with standard LMC overlays.

1594. Stock, A. F. et al., "CONCRETE PAVEMENTS," Elsevier Applied Science Publishers, 1988, pp. 1-433.

This book provides a source c,f information on the current technology available to designers and constructors of concrete pavements. It contains one introduction and the following ten chapters: a mechanistic approach to rigid pavement design;

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concrete for pavements; concrete pavement construction; evaluation of concrete pavements; skidding resistance of concrete surfaces; maintenance of portland cement concrete pavement; criteria for the design and construction of continuously reinforced concrete pavement; overlay design;prestressed concrete pavements; interlocking concrete block pavements.

1595. Su, E. and HSU, T., "BIAXIAL COMPRESSION FATIGUE AND DISCONTINUITY OF CONCRETE," ACI Materials Journal, Vol. 85, No. 3, May 1988, pp. 178-188.

A biaxial compression fatigue machine was built to test plain concrete plates of 6 x 6 x 1.5 in. (15.2 x 15.2 x 3.8 cm). Brush-type loading platens were used to eliminate the edge friction. The test program covered four principal biaxial-compression stress ratios and a range of load cycles from 1 to 2,000,000. Within this range of cycles the S-N (fatigue stress versus number of cycles) curve was found not to be a straight line as commonly assumed. This S-N curve can be closely represented by a modified Richard and Abbott's expression. The observed S-N curves of concrete can each be idealized by two straight lines that have significantly different slopes. The slope for low-cycle fatigue is several times greater than that for high-cycle fatigue. These two straight lines form a distinctive kink at the intersection. This point of intersection represents the discontinuity stress and can be used as its definition. Compared to the authors' tests, the S-N curves obtained in the literature are found to be not conservative because of the end friction exerted by the solid loading platens on the test specimens. The fatigue strength of concrete under biaxial compression is greater than t h a t under uniaxial compression for any given number of load cycles. Observation of failure modes and the measurements of deformations also indicate that concrete possesses similar failure patterns under static and fatigue loadings.

1596. Su, E. C. M. and HSU, T. T. C, "FATIGUE TEST MACHINE FOR BIAXIAL COMPRESSION OF CONCRETE," Journal of Testing & Evaluation, Vol. 16, No. 6, 1988, pp. 549- 554.

A 980 kN capacity test machine has been developed to study the fatigue behavior of concrete under biaxial compression. It features a load bifurcation mechanism and brush-type loading platens. Concrete plates 15.2 by 15.2 by 3.8 cm can be tested with the two principal stress ratios ranging from 0 (uniaxial)

255

t o 1.0 (equal b i a x i a l ) , arid wi thout edge f r i c t i o n a l c o n s t r a i n t . Deformations i n t he three p r i n c i p a l d i r e c t i o n s can be measured conti .nuously throughout a test u s i n g a capac i tance- type measuring device.

1597. S u l l i v a n , B. R., "PERMEABILITY 7IESTING SYSTEM FOR GROUT, CONCRETE, AND ROCK, I' Permeab i l i t y of Concrete , ACI SP-108, a, 1988, pp. 259-1741.

A t e s t i n g system which can accommodate up t o seven samples s imul taneous ly w i t h computer -cont ro l led d a t a a c q u i s i t i o n , a n a l y s i s , and r e p o r t i n g i s described. T h e system c o n s i s t s of seven c o r e h o l d e r s o f t h e Hassler t y p e which can handle c y l i n d r i c a l samples r ang ing from 1-1/2 t o 4 i n . i n diameter and from 4 t o 11 i n . i n l e n g t h . Confining and d r i v i n g p r e s s u r e s can be independent ly varied up t o 4 0 0 0 p s i . The t es t medium can be e i t h e r l i q u i d o r gas i n c l u d i n g b r i n e , s i n c e a l l t u b i n g and c o n t a i n e r s are s t a i n l e s s steel . Flow i s determined by p r e s s u r e i n c r e a s e i n a c o l l e c t . c r t a n k f o r gas and change i n l iqufid level i n a p i p e t t e column f o r l i q u i d . Four p r e s s u r e t r a n s d u c e r s p e r c a r e h o l d e r are used t o monitor a l l p r e s s u r e levels d u r i n g a t es t . A computer-based d a t a a c q u i s i t i o n system i s used t o scan up t o seven tes ts s imul taneous ly anda r e c o r d a l l data on a disc. Upon t e r m i n a t i o n of a test , flow and p e r m e a b i l i t y a r e computed and p l o t t e d a g a i n s t t i m e and a r e p o r t i s p r i n t e d f o r t h e tes t . The data are saved permanently on t h e d i s k and a backup copy i s t r a n s f e r r e d t o a f loppy d i s k f o r safe storage. Sample p r e p a r a t i o n , sea l ing , and t e s t i n g procedures are expla ined . Data a n a l y s i s and typ ica l - r e s u l t s are p r e s e n t e d on s a l t c o r e s and c o n c r e t e samples.

1598. Tikalsky , P. J. and C a r r a s q u i l l o , P . M. e t a l . , "STRENGTH AND D U R A B I L I T Y CONSIDERATIONS AFFECTING M I X PROPORTIONING OF CONCRETE CONTAINING FLY ASH, 'I A C I Materials Journa l , V o l . 86, N o . 6, Nov-Dec 1988, pp.. 505-511.

R e s u l t s of a th ree -yea r s tudy on t h e p r o p e r t i e s of c o n c r e t e c o n t a i n i n g f l y ash are p r e s e n t e d . Both t h e fresh and hardened p r o p e r t i e s are r e p o r t e d f o r c o n c r e t e made u s i n g Type I cemext, r iver gravel, n a t u r a l sand, and f l y ashes froin several sou rces . The mix tu res were propor t ioned t o have s imi la r slump and a c o n s t a n t cemen t i t i ous con ten t by weight . I t i s shown t h a t c o n c r e t e c o n t a i n i n g f l y as .h car, be p ropor t ioned having equa l s t r e n g t h p r o p e r t i e s and adequate d u r a b i l i t y when a s u i t a b l e ASTM C 6 1 8 C l a s s C o r C l a s s F f l y ash i s used. T e s t d a t a on over 1 6 0 0 l a b o r a t o r y

2 5 6

and field specimens tested for freeze-thaw resistance, flexural strength, compressive strength, creep, shrinkage, and abrasion resistance are presented. Fly ash contents ranging from 0 to 35 percent by weight of portland cement were used with both Class C and Class F fly ashes. Guidelines for the selection of materials and their proportions for producing concrete containing fly ash to meet existing highway specifications for concrete are presented.

1599. Tsai, W. T., "UNIAXIAL COMPRESSIONAL STRESS-STRAIN RELATION OF CONCRETE," Journal of Structural Engineering, Vo1.114, No.9, Sep 1988, pp. 2133-2136.

The stress-strain relation of concrete under compression is known to contain an ascending portion and a descending portion. The ascending portion is well characterized. However, the descending portion has not yet been completely developed. Since the relations for both portions are steeper as the ultimate concrete strength becomes higher, concrete with higher strength has higher potential of catastrophic failure after the peak strength is reached. Therefore, the descending portion is important if ductility of the concrete members is desired. Development of an accurate stress-strain relation for the descending portion becomes necessary. This note proposes a new equation to represent the uniaxial compressional stress-strain relation of concrete. It consists of two parameters, one to control the ascending behavior and the other to control the descending behavior.

1600. Wall, J. S. and Shrive, N. G., "FACTORS AFFECTING BOND BETWEEN NEW AND OLD CONCRETE," ACI Materials Journal, Vol. 85, No. 2, Mar-Apr 1988, pp. 117-125.

attempts are usually made to bond the two concretes together: often a cement paste or mortar "joint" is used, as in masonry. The service stress states in bonds can vary tremendously so no single test method can replicate all these states. A method of test for bond should reflect a typical inservice stress state yet also be sensitive to variation in the strength of the bond. Four tests were evaluated, and a slant shear test was found to be the most appropriate. The effects of various parameters were evaluated theoretically with the finite element method and/or experimentally. A bond material with a modulus of elasticity similar to the adjacent concrete was found to be desirable, as was consistency in the bond

When new concrete is placed next to old concrete,

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material properties. Thick bond layers were found to reduce bond strength considerably and copolymer polyvinylacetate was found to be a poor bonding agent over a wide range of curing conditions and mortar mix designs.

1601. Whiting, D., "PERMEABILITY OF SELECTED CONCRETES, I' Permeability of Concrete, ACI SP-108, a, 1988, pp. 195-222.

Study of permeability was made using six concrete mixtures ranging in water-to-cementitious material (w- c) ratio from 0.26 to 0.7.5. Concrete specimens were tested for permeability to water and air, permeability to chloride ions (rapid and long-term), volume of permeable voids, and porosity. Results confirm that permeability is a direct function of w-c ratio. The addition of silica fume results in even greater decreases in permeability than would be anticipated based solely on w-c ratio. A period of initial moist curing of at least seven days is essential for achieving low permeability. Results also indicate that rapid test procedures offer a reasonable alternative to more lengthy and complex conventional permeability tests.

1602. Wilson, H. S. and Malhotra, V. M.., "DEVELOPMENT OF HIGH STRENGTH LIGHTWEIGHT CONCRETE FOR STRUCTURAL APPLICATIONS," International Journal of Cement Composites and Lightweight Concrete, Vol. 10, No. 2, May 1988, pp. 79-90.

Investigation reports results of a study undertaken to develop high-strength lightweight concretes using a Canadian lightweight aggregate. A series of seven concrete mixtures involving 25 batches were made. The cement or cements, fly ash, and silica fume content o f t h e mixtures ranged from 300 t o 635 kg/(m**3). All mixtures were air entrained and superplasticized. A large number of test cylinders and prisms were cast for the determination of the mechanical properties of concrete and to evaluate its resistance to freezing and thawing. It is concluded that high-strength concretes with densities of less than 2000 kg/(m**3) can be made with or without the use of mineral admixtures, but the use of superplasticizers is mandatory. The highest compressive strength achieved was 66.5 MPa at 365 days for a cementitious content of 638 kg/(m**3). The 28 day splitting tensile strengths obtained were of the order of 3.5 MPa. The freezing and thawing tests performed indicated excellent frost

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resistance of concrete with durability factors generally greater than 90.

1603. Yong, Y.-K. and Sethi, M., "SHEAR STRENGTH OF PLAIN

AXIAL COMPRESSION, I' ACI Materials Journal, Vol. 85, No. 2, Mar 1988, pp. 75-81.

HIGH-STRENGTH CONCRETE BEAMS WITH SILICA FUME UNDER

This paper details an experimental investigation of the shear strength of high-srength plain concrete specimens f sub c'= 9000 to 12,500 psi ( 6 2 to 86 MPa) with a shear span ratio of 1 and under axial compressive stresses of up to 0.62 f sub c' . The ratio of condensed microsilica fume to cement was 0.37. The experimental data were checked aganist the shear strength calculated according to the ACI Building Code (ACI 318-83) and the proposals made by ACI-ASCE Committee 426 on Shear and Diagonal Tension. The theoretical shear strength of concrete V sub c increases with respect to both the compressive strength of concrete f sub c' and the axial compressive stress N sub u/A sub g. The increases in the calculated shear strength were found to be conservative with regard to the increase in f sub c, but unconservative with respect to the increase in N sub u/A sub g.

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1989

1 6 0 4 . "PROPERTIES OF CONCRETE A T EARLY AGES," Concrete I n t e r n a t i o n a l : Design and Cons t ruc t ion , V o l . 11, No. 4 , Apr 1989, pp. 51-54.

Recent ly , there has been an i n c r e a s i n g i n t e r e s t i n t h e p r o p e r t i e s of conc re t e a t ages less t h a n 28 days. Two f a c t o r s c o n t r i b u t i n g t o t h i s r e d i r e c t i o n o f i n t e r e s t are t h e fas t -paced c o n s t r u c t i o n schedu les t h a t expose c o n c r e t e t o s i g n i f i c a n t s t r u c t u r a l l o a d s a t e a r l y ages, and t h e r e c o g n i t i o n t h a t long-term performance of c o n c r e t e i s g r e a t l y a f f e c t e d by ear ly- age h i s t o r y . A summary of t h e Engineer ing Foundation Conference i s g iven t o improve unders tanding and a p p r e c i a t i o n of t h e p r o p e r t i e s c f c o n c r e t e a t e a r l y ages.

1605 . Anderson, F. D . , "72-STORY HIGH-RISE WITH 83 MPA FLY ASH CONCRETE - A CASE HISTORY," F l y Ash, S i l i c a Fume, Slag, and Na tu ra l Pozzolans i n Concrete - Proceedings Th i rd I n t e r n a t i o n a l Conference, Trondheim, Norway, ACI SP-114, a, 1989, pp. 607-624.

Describes r e c e n t l y completed c o n s t r u c t i o n o f a 175,000 (m**2) (1.85 m i l l i o n f ( t * * 2 ) 72-story o f f i c e b u i l d i n g . A unique f e a t u r e o f t h e s t r u c t u r a l system i s t h e h igh - s t r eng th r e i n f o r c e d c o n c r e t e - s t r u c t u r a l s teel composite columns. Conventional aggregates and p o r t l a n d cement, w i th about 2 9 p e r c e n t f l y a s h replacement , produced average 5Em day compressive s t r e n g t h s of over 8 3 MPa ( 1 2 , 0 0 0 p s i ) , e a s i l y s u r p a s s i n g t h e des ign s p e c i f i e d s t r e n g t h o f 69 MPa ( 1 0 , 0 0 0 p s i ) . Most of the c o n c r e t e w a s p l a c e d a t a slump o f 200 mm (8 i n . ) , u s ing a high-range w a t e r - r educ ing admixture. The s t r u c t u r a l d e s i g n w a s based on 16 e x t e r i o r columns, an arran.gement t h a t a l lowed e x c e l l e n t u t i l i z a t i o n of t e n a n t space. P r e c o n s t r u c t i o n research and development of t h e high- s t r e n g t h fly ash conc re t e mix des igns proceeded s imul taneous ly w i t h t he a r c h i t e c t u r a l and s t r u c t u r a l des ign . R e s u l t s of these tests produced impor tan t d a t a on modulus o f e l a s t i c i t y , s .hrinkage, and c r e e p t h a t i n f l u e n c e d the composite ccllumn des ign . Much of t h e c o n c r e t e w a s p l aced under h a t weather c o n d i t i o n s t y p i c a l o f Texas, where summer ambient t empera tu res sometimes exceed 4 0 C ( 1 0 4 F ) . While f l y ash w a s employed i n a l l o f t he conc re t e mixes, t h i s pape r focuses on t h e h igh - s t r eng th a s p e c t s i n which t h e use of f l y a sh w a s an e s s e n t i a l i n g r e d i e n t .

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1606. Atkins, M. and MacPhee, D. E. et al., "CHEMICAL MODELLING IN BLENDED CEMENT SYSTEMS," Fly Ash, Silica Fume, Slag and Natural Pozzolans in Concrete - Proceedings Third International Conference, Trondheim, Norway, ACI SP-114, a, 1989, pp. 73-96.

Blast furnace slags and pulverized fly ash have been used extensively as additives to ordinary portland cement (OPC) to make low-permeability pastes with adequate long-term strengths. These properties are a consequence of phase development in the matrix that proceeds nonuniformly because the OPC clinker and blending agent react at different rates. Also, sheaths of hydration products forming around anhydrous grains inhibit reaction. This complicates our interpretation of the properties of blended cement systems because phases observed as products on laboratory time scales are not necessarily representative of the steady state assemblages. The aqueous chemistry is also subject to time-dependent changes since solution composition is related to that of the coexisting solids. In some applications, it is necessary to predict long-term physicochemical properties. This can be achieved through modelling, based on sound scientific principles, and using as much information as realistic from immature systems. Paper describes progress in model development and verification.

1607. Bentur, A. and Goldman, A., "CURING EFFECTS, STRENGTH AND PHYSICAL PROPERTIES OF HIGH STRENGTH SILICA FUME CONCRETES," Journal of Materials in Civil Engineering, Vol. 1, No. 1, Feb 1989, pp. 46-58.

Work is described which characterizes high strength silica fume concretes from the points of view of heat generation, shrinkage and sensitivity to curing, and compares their performance with that of concretes made of portland cement only, having either the same cement content or the same water to cementitious materials ratio. It was found that the presence of silica fume resulted in a marked increase in strength, especially at 28 days, but also at 1 day. This, however, was not accompanied by excessive heat liberation. Calorimetric measurements suggest an accelerating effect of the SF on the reaction of the portland cement. These and other observations are noted and discussed.

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1608.

1609.

Cebeci, 0. Z . and Al-Noury, S. I . e t a l . , "STRENGTH AND DRYING SHRINKAGE OF MASONRY MORTARS I N VARIOUS TEMPERATURE-HUMIDITY ENVIRONMENTS," Cement and Concrete Research, V o l . 1!3, N o . 1, Jan 1989, pp. 53- 62.

The compressive and f l e x u r a l s t r e n g t h development and d r y i n g sh r inkage of p:Lain cement and cement-lime mor ta r s under v a r i o u s tempera ture and humidi ty c o n d i t i o n s have been i n v e s t i g a t e d . p repa red a t 20, 35, and 5OC and were cu red i n l i m e - s a t u r a t e d water, o r exposed t o 33, 75, o r 92 p e r c e n t re la t ive humidity f o r v a r i o u s p e r i o d s up t o one year. R e s u l t s show t h a t , w h i l e t he u l t i m a t e s t r e n g t h of p l a i n cement mor ta r i s adve r se ly affected by high tempera ture , b o t h ea r ly and the u l t i m a t e s t r e n g t h s of cement-lime mor ta r s i n c r e a s e w i t h t empera ture . T h i s effect i s more pronounced w i t h i n c r e a s i n g l i m e c o n t e n t a n d . i s observed f o r a l l levels of humidi ty and c u r i n g p e r i o d . The f l e x u r a l t o compressive s t r e n g t h r a t i o i s affected only by t h e s t r e n g t h . i n c r e a s e s t h e i n i t i a l r a t e o f d ry ing shr inkage , b u t reduces t h e u l t i m a t e shr inkage .

The specimens w e r e

High t empera tu re

Cook, J. E. , m ' l O , 000 P S I CONCRETE, Concrete I n t e r n a t i o n a l , O c t 1989, pp. 67-75.

Loca l ly available materials used i n t h e p roduc t ion of ready-mixed concrete can produce compressive s t r e n g t h s i n excess o f 1 0 , 0 0 0 p s i ( 6 9 MPa) . I t i s feasible t o produce s t r e n g t h s i n excess of 1 0 , 0 0 0 p s i (69 MPa) u s i n g a 1- in . (25.4-mm) maximum-size aggregate when t h e mixture i s p ropor t ioned w i t h a high-range water-reducing admixture . I n g e n e r a l , t h e larger t h e amount of c o a r s e aggregate w i t h a high e l a s t i c modulus i n a c o n c r e t e mixture , t h e higher the modulus of e l a s t i c i t y of t h e c o n c r e t e . Q u a l i t y c o n t r o l t echn iques commonly used f o r low t o moderate s t r e n g t h c o n c r e t e s may not n e c e s s a r i l y be a p p r o p r i a t e f o r very h igh s t r e n g t h c o n c r e t e s . A l a b o r a t o r y t r i a l batch program seems t o be the most effective method of de te rmining c o n c r e t e p r o p e r t i e s and e s t a b l i s h i n g mix tu re p r o p o r t i o n s f o r h igh - s t r eng th c o n c r e t e . Specimen s i z e used f o r s t r e n g t h measurements of l a b o r a t o r y t r i a l batches should be c o n s i s t e n t w i t h t h e s i z e used by t h e s p e c i f i e r f o r acceptance on t h e p r o j e c t . T h e c o e f f i c i e n t o f v a r i a t i o n e x p r e s s i o n i s a more u s e f u l t e r m i n comparing t h e degree of c o n t r o l between h igh - s t r eng th conc re t e a n d low t o moderate s t r e n g t h c o n c r e t e s . The a v a i l a b i l i t y of data on higher s t r e n g t h c o n c r e t e s r e q u i r e s a reassessment of

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current equations to determine their applicability with higher strength concretes.

1610. Fiorato, A. E., "RESEARCH ON HIGH-STRENGTH CONCRETE," Concrete International: Design and Construction, Vol. 11, No. 4, Apr 1989, pp. 44-50.

Reviews Portland Cement Association-sponsored research on high-strength normal-weight concrete. This research has reflected construction-industry needs for technological information about high- strength concrete applications for prestressed members, building, and bridges, and in situations where durability rather than strength is the primary concern.

1611. Giraldi, A., "HIGH-STRENGTH CONCRETE IN WASHINGTON, D.C.," Concrete International: Design and Construction, Vol. 11, No. 3, Mar 1989, pp. 52-55.

Traces the evolution of high-strength concrete in the Washington, D.C. area as experienced by a ready- mixed concrete producer. The proportioning process and the use of local materials are reviewed. As strength requirements increased, the experience gained from each preceding mix was used in formulating the higher strength mixes. Improved field and laboratory testing techniques are recommended.

1612. Janssen, D., "PCC MIX DESIGN. FINAL REPORT, I' University of Washington, Seattle, Wa, Mar 1989, pp. 55.

Properties of portland cement concrete (PCC) mixes, including workability, strength, durability, and abrasion resistance, are discussed along with the specific mix factors that affect each property. The mix design process is then discussed and the effect of each ingredient on PCC properties is explained. Chemical and mineral admixtures are included. The adequacy and limitations of the WSDOT mix design procedure are addressed. Recommendations for special considerations such as long transit times, high early strengths, and qualification of aggregates by non- standard methods are presented.

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1613. Kudlapur, S. et al., "EVALUATION OF COLD-WEATHER CONCRETE PATCHING MATERIALS, 'I ACI Materials Journal, Vol. 86, No. 1, Jan 1989, pp. 36-44.

The results are presented of an investigation of patching materials suitab1le for winter maintenance operations of bridges and pavements at subfreezing temperatures. Four materials, identified by a preliminary screening investigation as potentially suitable, were tested extensively for strength and durability. The four materials are methyl methacrylate-based polymer concrete, two types of magnesium phosphate-based concretes, and polyurethane- based concrete. Methyl methacrylate emerges as superior to the other materials in terms of performance, but environmental considerations mitigate in favor of the magnesium phosphates. The water-based magnesium phosphate has relatively poor freeze-thaw durability when cast at subfreezing temperatures, but the liquid-activated variety offers a reasonable compromise between performance and environmental factors.

1614. Kudlapur, S. and Hanaor, A. et al., "EVALUATION OF COLD-WEATHER CONCRETE PATCHING MATERIALS," ACI Materials Journal, Vol. 86, No. 1, Jan 1989, pp. 36- 44.

The results are presented of an investigation of patching materials suitable for winter maintenance operations of bridges and pavements at subfreezing temperatures. Four materials, identified by a preliminary screening investigation as potentially suitable, were tested extensively for strength and durability. The four materials are methyl methacrylate-based polymer concrete, two types of magnesium phosphate-based concretes, and polyurethane-- based concrete. Methyl methacrylate emerges as superior to the other materials in terms of performance, but environmental considerations mitigate in favor of the magnesium phosphates. The water-based magnesium phosphate has relatively poor freeze-thaw durability when cast at subfreezing temperatures, but the liquid-activated variety offers a reasonable compromise between performance and environmental factors.

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1615. Luther , M. D. and Hansen, W . , "COMPARISON O F CREEP AND

FLY ASH CONCRETES O F SIMILAR STRENGTHS," F l y A s h , S i l i c a Fume, Slag, and Natura l Pozzolans i n Concrete - Proceedings Thi rd I n t e r n a t i o n a l Conference, Trondheim, Norway, ACI SP-114, a, 1989, pp. 573-592.

SHRINKAGE O F HIGH-STRENGTH S I L I C A FUME CONCRETES WITH

T h e s p e c i f i c creep and shr inkage of f ive high- s t r e n g t h c o n c r e t e mixtures w e r e monitored f o r 400 days a t the U n i v e r s i t y o f Michigan, Ann Arbor. One 52.6 MPa (7630 ps i ) s i l i c a fume (SF) c o n c r e t e was compared w i t h a fly ash c o n c r e t e of s imilar compressive s t r e n g t h , and SR c o n c r e t e and f l y ash c o n c r e t e having compressive s t r e n g t h s of approximately 69 MPa ( 1 0 , 0 0 0 p s i ) w e r e compared. A 106.6 MPa (15,450 p s i ) SF c o n c r e t e w a s a l s o s t u d i e d . The creep of SF c o n c r e t e s w a s no t s i g n i f i c a n t l y d i f f e r e n t from t h a t of t h e f l y ash c o n c r e t e s . Furthermore, t h e r e l a t i o n s h i p between creep and compressive s t r e n g t h was c o n s i s t e n t w i t h t h a t r e p o r t e d i n t h e open l i t e r a t u r e f o r h igh - s t r eng th p o r t l a n d cement conc re t e s . Seve ra l o t h e r c o n c r e t e p r o p e r t i e s were s t u d i e d , i n c l u d i n g slump r e t e n t i o n , t i m e of s e t t i n g , compressive s t r e n g t h development f o r one year , s p l i t - t e n s i l e s t r e n g t h , modulus of r u p t u r e , and f o r t h e nominal 69 MPa c o n c r e t e s only, r a p i d f r e e z i n g and thawing d u r a b i l i t y and the hardened c o n c r e t e a i r - v o i d system.

1616. Malhotra, V. M. and P a i n t e r , K. E . , "EARLY-AGE STRENGTH PROPERTIES, AND FREEZING AND THAWING RESISTANCE OF CONCRETE INCORPORATING H I G H VOLUMES OF ASTM CLASS F FLY ASH," I n t e r n a t i o n a l Jou rna l of Cement Composites and Lightweight Concrete, V o l . 11, No. 1, Feb 1989, pp. 37-46.

Paper r e p o r t s r e s u l t s of an i n v e s t i g a t i o n t o de te rmine t h e ear ly-age s t r e n g t h and t h e f r e e z i n g and thawing r e s i s t a n c e o f conc re t e i n c o r p o r a t i n g high volumes o f ASTM C l a s s F f l y ash. Three series of c o n c r e t e mixtures w e r e made. I n Series I , t he cement c o n t e n t w a s kept c o n s t a n t a t 145 +/ - 5 kg/(m**3), and t h e f l y ash amount w a s v a r i e d from 1 1 0 t o 197 kg/(m**3). The water- to-cementi t ious materials r a t i o ranged from 0.32 t o 0.42, and t h e e n t r a i n e d a i r c o n t e n t o f t h e mixtures was 9.5 +/- 1 . 0 p e r c e n t . The mix tu res of Series I1 w e r e s i m i l a r t o t h o s e of Series I excep t t h a t t h e a i r con ten t was reduced t o a convent iona l amount, i .e . , 5.5 +/ - 1.0 p e r c e n t . I n Series I11 mixtures , t h e f l y ash con ten t varied from 1 8 3 t o 275 kg/(m**3), and the r e s u l t i n g water- to- cemen t i t i ous m a t e r i a l s r a t i o ranged from 0.28 t o 0 .35 , w i t h t h e e n t r a i n e d a i r con ten t a t 4.0 +/- 0.5 p e r c e n t .

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The strength properties of the concrete were determined at ages up to 91 days, and the freezing and thawing tests were perforned in accordance with ASTM C 666 Procedure A. The results of this investigation show that the compressive strength of concrete incorporating high volumes of ASTM Class F fly ash increases with decreasing water-to-cementitious materials ratio, i.e., with the increasing amounts of fly ash. The optimum amount of fly ash appears to be about 200 kg/(m**3) of concrete. The concretes investigated had adequate early-age strength, and the freezing and thawing resistance of the concretes was satisfactory except that the test prisms suffered moderate to considerable surface scaling.

1617. Maslehuddin, M. and Al-Mana, A. et al., "EFFECT OF SAND REPLACEMENT ON THE EARLY-AGE STRENGTH GAIN AND LONG-TERM CORROSION-RESISTING CHARACTERISTICS OF FLY ASH CONCRETE," ACI Materials Journal, Vol. 86, No. 1, Jan 1989, pp. 58-62.

This is a report of the results of experiments carried out to evaluate compressive-strength development and corrosion-resisting characteristics of concrete mixtures in which fly ash was used as'an admixture (an equal quantity of sand was replaced). Data were developed for fly ash additions of 0, 20, and 30 % and water-cement ratios of 0.35, 0.40, 0.45,, and 0.50. The compressive strength was determined at 3, 7, 14, 28, 56, and 90 days. Concrete samples were partially immersed in a 5 % sodium chloride solution for a period of about 4 years, and corrosion-resisting characteristics of concrete were evaluated by monitoring the half-cell potential and measuring the corrosion rate of embedded steel bars using electrochemical techniques. Results show that addition of fly ash as an admixture increases the early-age compressive strength and long-term corrosion-resisting characteristics of concrete. The superior performance of these mixtures compared to plain concrete mixtures is attributable to the densification of the paste structure due to pozzolanic action between the fly ash and the calcium hydroxide liberated as a result of hydration of cement.

1618. Naik, T. R. and Ramme, B. W., "HIGH-STRENGTH CONCRETE CONTAINING LARGE QUANTITIES OF FLY ASH," ACI Materials Journal, March-April 1989, pp. 111-116.

Presents research performed to identify and recommend mix designs for high fly ash content 3000 and 4000 psi (21 and 28 MPa) structural grade concrete

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utilizing Class C fly ash. The fly ash was produced at Wisconsin Electric Power Company's Pleasant Prairie Power Plant.

1619. Plante, P. and Bilodeau, A., "RAPID CHLORIDE ION PERMEABILITY TEST: DATA ON CONCRETES INCORPORATING SUPPLEMENTARY CEMENTING MATERIALS," Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete - Proceedings Third International Conference, Trondheim, Norway, ACI SP-114, a, 1989, pp. 625-644.

Gives results of an investigation on the chloride ion permeability of concretes incorporating supplementary cementing materials, using the Rapid Determination of Chloride Permeability Test (AASHTO T277-83). A total of 18 concrete mixtures were made. These included mixtures incorporating silica fume (8 percent replacement or addition to the cement by mass) or ground granulated blast furnace slags (50 percent replacement by mass), or fly ash (25 percent replacement by mass). The w/c of the mixtures investigated ranged from 0.21 to 0.71. From each mixture, a number of 152 x 305 mm cylinders for compressive strength testing and 102 x 203 mm cylinders for determining the chloride permeability were made. Porosity measurements were also performed on some of the concrete specimens. The test results showed that the use of supplementary cementing materials significantly reduced the chloride ion permeability of concrete. Silica fume and blast furnace slags investigated seem to be particularly efficient for producing concrete almost impermeable to chloride ions.

1620. Ronne, M., "EFFECT OF CONDENSED SILICA FUME AND FLY ASH ON COMPRESSIVE STRENGTH DEVELOPMENT OF CONCRETE," Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete - Proceedings Third International Conference, Trondheim, Norway, ACI SP-114, a, 1989, pp. 175-190.

The effect of different curing conditions on the long-term compressive strength of concrete containing silica fume and fly ash was investigated. The project was carried out as a parallel test program at three different laboratories for a period of two years. Two mixes were chosen: one blended cement (MP30) containing 25 percent fly ash, and the other containing 25 percent fly ash and 10 percent silica fume. The cubes were exposed to six different curing conditions at different temperatures (20 to 70 C) and humidities (about 30 to 100 percent relative humidity). In one of the series, the cubes were

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allowed to dry on one side only. The compressive strength for both the cements containing fly ash and silica fume were sensitive to the early drying procedure. Good initial curing conditions in the first three days of curing gave an improvement in compressive strength compared to the samples dried immediately after demolding.

1621. Rosenberg, A. M. and Gaidis, J. M., "NEW MINERAL ADMIXTURES FOR HIGH-STRENGTH CONCRETE," Concrete International: Design and Construction, Vol. 11, No. 4, Apr 1989, pp. 31-36.

During research leading to the development of a new concrete admixture, insight was obtained on how silica fume enhances the strength of concrete. Silica fume does not densify concrete in the usual sense; it enhances the paste-aggregate bond, which is generally the weakest part of concrete. This comes about by a reduction in the amount of bleed water produced. Chemical and physical evidence is shown to prove these conclusions.

1622. Roy, D. M., "FLY ASH AND SILICA FUME CHEMISTRY AND HYDRATION," Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete - Proceedings Third International Conference, Trondheim, Norway, 1989, ACI SP-114, a, 1989, pp. 117-138.

Hydration of cements containing the supplementary cementing materials fly ash (FA) and silica fume (SF:i is discussed and compared with the hydration of ordinary portland cement (OPC). Early stage heats of hydration, changes in the chemistry of the solution (both at early stages, and later pore solution compositions), microstructural development, and pore structure are compared. The hydration rates normally follow the order: SF > OPC > FA. The complex hydration processes may be controlled so that the use of these cements enables development of materials having superior strength and durability.

1623. Smadi, M. M. and Slate, F. O., "MICROCRACKING OF HIGH AND NORMAL STRENGTH CONCRETES UNDER SHORT- AND LONG- TERM LOADINGS," ACI Materials Journal, Vol. 86, No. 2, Mar - Apr 1989, pp. 117-127.

The effects of both monotonic and sustained uniaxial compressive stresses on the relationships among microcracking, strength, and deformation of high-strength concrete were studied using x-ray

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t echn iques and compared w i t h t h o s e o f low and medium s t r e n g t h c o n c r e t e s . The formation, propagat ion , and s t a b i l i t y o f microcracks and the i r c o n t r i b u t i o n t o t h e f a i l u r e o f c o n c r e t e under b o t h t y p e s of l oad ings are examined and d i scussed . The stress levels i n v e s t i g a t e d ranged from 4 0 t o 95 p e r c e n t o f u l t i m a t e f o r t h e three m a t e r i a l s . High-strength c o n c r e t e showed s i g n i f i c a n t l y smaller amounts of c r ack ing a t a l l stress levels t h a n normal s t r e n g t h c o n c r e t e s . A s a r e s u l t , lesser i n e l a s t i c deformat ions and h i g h e r creep-stress l i n e a r i t y l i m i t s w e r e a s s o c i a t e d w i t h t h e former t h a n wi th t he o t h e r s .

1624. Swamy, R. N . and Mahmud, H. B. , "SHRINKAGE AND CREEP BEHAVIOUR OF H I G H FLY ASH CONTENT CONCRETE," F l y A s h , S i l i c a Fume, Slag, and Na tu ra l Pozzolans i n Concrete - Proceedings Thi rd I n t e r n a t i o n a l Conference, Trondheim, Norway, ACI SP-114, a, 1989, pp. 453-476.

Paper p r e s e n t s e x t e n s i v e tes t data on t h e shr inkage and c r e e p behavior of h igh f l y ash-content c o n c r e t e made w i t h o r d i n a r y p o r t l a n d cement and 50 p e r c e n t by weight cement replacement w i t h low-calcium Type F f l y ash. T h e c o n c r e t e mixes w e r e des igned t o have 2 0 , 40 , and 60 MPa 28 day cube s t r e n g t h w i t h high w o r k a b i l i t y and low water-to-composite cement r a t i o . The o t h e r variables w e r e t he exposure c o n d i t i o n f o r the sh r inkage tes ts and s t r e s s - s t r e n g t h r a t i o f o r the c r e e p tests. The r e s u l t s showed t h a t f o r s t r u c t u r a l c o n c r e t e of 4 0 t o 60 MPa, t he u l t i m a t e sh r inkage s t r a i n ranged from 400 t o 500 x 1 ( 0 * * - 6 ) m/m. The s w e l l i n g s t r a i n amounted t o 40 t o 55 p e r c e n t of t he sh r inkage v a l u e and i n d i c a t e d the importance and cont inued water c u r i n g f o r effective r e a l i z a t i o n of f u l l pozzo lan ic a c t i o n o f t h e f l y ash . For t h e same concrete s t r e n g t h of 4 0 t o 60 MPa, t h e s p e c i f i c c r e e p and t h e c r e e p c o e f f i c i e n t w e r e remarkably low ranging from 4 0 t o 1 0 0 x 1(0**-6) MPa and 1 . 2 0 t o 2.50, r e s p e c t i v e l y . The d a t a c l e a r l y confirm t h a t the t i m e - dependent deformations of wel l -designed h igh f l y ash- c o n t e n t c o n c r e t e compare extremely w e l l w i t h t h o s e o f p o r t l a n d cement conc re t e .

1625. Thomas, M. D. A. and Matthews, J. D . e t a l . , "EFFECT O F CURING ON THE STRENGTH AND PERMEABILITY O F PFA CONCRETE," F ly Ash , S i l i c a Fume, Slag, and Na tu ra l Pozzolans i n Concrete - Proceedings Th i rd I n t e r n a t i o n a l Conference, Trondheim, Norway, ACI SP- 1 1 4 , a , 1989, pp. 191-218.

Tests w e r e c a r r i e d out on a series of c o n c r e t e mixes, des igned t o equal w o r k a b i l i t y and 28 day

269

compressive strength and with a range of pulverized fuel ash (pfa) levels, to study -the effect of curing on the strength and permeability of pfa concrete. Concrete specimens were subjected to a range of moist- curing periods prior to air storage. Compressive strength was determined at: various ages and permeability to oxygen and water was determined at 28 days. Results confirm the imporzance of curing, with reductions in the curing period resulting in lower strength, more permeable concrete. The strength of the pfa concretes appears to be more sensitive to poor curing than ordinary portland ceinent (opc) concrete, the sensitivity increasing with increasing pfa content. However, despite exhibiting lower strengths, pfa concretes moist cured for only one day were, generally, no more permeable to water and substantially less permeable to ODxygen than similarly cured opc concretes. increased, the pfa concretes became considerably more impermeable to water and oxygen than the opc concretes. These results are discussed in the context of the minimum periods of curing and protection recommended in BS 8110. It is argued that although the increased curing periods suggested for pfa concrete are justified on the basis of concrete strength, pfa concrete may require no more curing than opc concrete to achieve equal durability, as measured by oxygen and water permeability.

As the period of curing

1626. Yankelevsky, D. Z. and Reinhardt, H. W., "UNIAXIAL BEHAVIOR OF CONCRETE I N C Y C L I C T:ENSION," Journal of Structural Engineering, ASCE, Vol. 115, No. 1, Jan 1989, pp. 166-182.

A new one-dimensional model for random cyclic tension in concrete is developed. The model determines several geometrical loci, defined as focal points, in the uniaxial stress-displacement plane, which are used to compute the coinplete unloading- reloading curves. Given the complete load- displacement curve, the focal points are located, and the path of any unloading-reloading cycle can be computed. without further complications. 'The model is compared with test results recently obtained at the Stevin Laboratory, Delft University of Technology, as well as with other available data, and good agreement is shown.

A cycle may also be plotted graphically

270

AUTHOR INDEX

Aarsleff, L.

Aavik, J.

ACI Committee 214

ACI Committee 228

ACI Committee 363

Acker, P.

Ahmad, S. H.

Aitcin, P. C.

Alegre, S.

Alexander, K. M.

Alexander, M. G.

Alford, N. McN

Alliche, A.

Anderson, F. D.

Anderson, S. M.

Andrews, K. R. F.

Ansari, F.

Arnaouti, C.

Aronsson, R.

Arthur, P. D.

Atkins, M.

Attiogbe, E. K.

Bache, H. H.

Bailey, J. E.

Balaguru, P.

Bamforth, P. B.

1291

1292

1523

1524

1411

1412

1293, 1294, 1357, 1413

1525

1414

1125, 1159

1526

1177

1358, 1415

1527, 1605

1528

1126

1416

1243

1018

1128

1606

1417

1295

1359

1418, 1530

1419

271

B a n t . h i a , N . P .

B a r k e r , M . G .

B a r n a r d , D . P .

B a r r i c k , J. E .

B a u e r , C . J.

B a z a n t , Z . P .

B e a m s , Jr . , G . W .

B e a u d o i n , J . J .

B e n t - u r , A.

B e r n e r , D .

B e r r y , E . E .

B i c k l e , L . W .

B i r c h a l l , J. D .

B i s a i l l o n , A .

B i s h a r a , A . G .

B i s w a s , M.

B l a c k i e , A . D .

B o c c a , P .

B a r t o l o t t i , L .

Bowery, F. J .

B r a m e s h u b e r , W .

B r e r n n e r , T . W .

B r e t t , D . M .

Brornham, S . B .

B r o o k s , J. J.

B r o w n , J. H .

1360, 1420

1531

1296

1045

1532

1001, 1002, 1046, 1047, 1099, 1130, 1193, 1245, 1246, 1247, 1297, 14.21, 1422, 1.423, 1533

1194

1298

1361, 1424, 1607

1299

1101

1019

1215

1534

1102

1300

1195

1248

1535

1103

1425

1362

1536

1065, 1.216

1066, 1104, 1129,, 1217, 1363

1020

Brown, T. G.

Bryant, A. H.

Buck, A.

Buenfeld, N. R.

Buerge, T. A.

Buil, M.

Butler, W.

Cabrera, J. G.

Campbell-Allen, D.

Carpenter, J. E.

Carpinteri, A.

Carrasquillo, I?. M.

Carrasquillo, R. L.

Carreira, D. J.

Carse, A.

Cebeci, 0. Z.

Cedolin, L.

Cervenka, V.

Chapman, R. A.

Chatterji, S.

Chin, D.

Chou, Y. T.

Christensen, D. W.

Clark, C. R.

Clarke, J. L.

Clear, K. C.

Clifford, D. J.

1160

1130

1426

1249, 1364

1218

1250, 1301, 1427

1428

1251

1021

1161

1196

1537, 1538, 1539

1178, 1179, 1252

1302

1162

1608

1067, 1253

1303

1429

1197

1430

1068

1254

1219

1431

1022, 1069

1432

273

C l i f t o n , J . R.

Coleman, S . E .

C o l l i n s , R . J.

Colony, D . C .

Cook, D . J .

Cook, J. E .

C o r n e l i s s e n , H . A. W

Cumming, N . A .

Day, R . L .

Delibes, L . A .

Dennison, A.

Derucher , K . N .

D e w a . r , V. D .

Dh i r , R . K .

Diamond, S .

D i e d e r i c h s , U .

Dinysoyr , E .

D m i t . r i e v , A. M.

Dolch, W .

Domone, P . L .

Dransf ie ld , J. M .

Duns tan , Jr . , E . R .

Eash, R . D .

E c k e r t , W . C .

Eden, N . B .

Edwards, J. H .

Ehm,. C .

1048

1198, '1255

1220

1131

1163, 1180

1609

1256, 1257, 1258, 1304, 1365, 1366

1540

1259, 1541

1433

1434

1105

1305, 1306

1003, 1004, 1260, 1261, 1435, 1542

1307, 1367, 1543

1221

1308

1106

1436

1005

1262

1049, 1.437

1023

1544

1263, 1.264, 1309

1132

1310

2 7 4

E l - J a z a i r i , B.

F a g e r l u n d , G .

F a r b i a r z , J .

F a t a l i e v , S . A.

F a u l k n e r , T .

Feldman, R . F.

Feng, N . Q .

F i o r a t o , A . E .

F i t z g i b b o n , M. E .

F o u r e , B.

Fowle r , D . W .

Foy, C .

F r a a y , A.

F r a n k l i n , R . E .

F r o h n s d o r f f , G .

F r o l o v a , L . S .

F u j i t a , Y .

F u r t a k , K .

Gal loway, J. W .

Gannon, C . R .

Ga rdne r , N . J .

Garre t t , G . G .

Gauert , C . E .

Gaynor, R . D .

Gehring, D .

Gerstle, Kur t H .

Gerwick, J r . , B. C .

1199, 1439

1070, 1200, 1201

1440

1133

1441

1311

1545

1610

1050

1312

1134, 1442

1546

1443

1202

1368

1313

1071

1265

1135, 1136

1222

1547

1137

1107

1006, 1314

1266

1138

1024, 1164

275

Ghosh, R. K.

Ghosh, R. S.

Giaccio, G. M.

Gibson, F. W.

Giraldi, A.

Gjorv, 0. E.

Gomez-Toledo, C.

Goodman, M. L.

Gopalan, M. K.

Gran, J. K.

Greenhut, S.

Gress, D. L.

Griffin, D. F.

Gruebl, P.

Gustafsson, P. J.

Gutmann, P. F.

Gylltoft, K.

Hadley, W. 0.

Hajek, J.

Halstead, W. J.

Halvorsen, G. T.

Hansen, W.

Haque, M. N.

Harrison, W. H.

Hawkins, N. M.

Heikkinen, A.

Heinz, D.

1203

1181

1548

1444

1611

1025, 1549

1072

1007

1445

1315

1446

1204

1051

1316

1317

1550

1073

1074

1108

1165

1447

1318

1052, 1223, 1267, 1551

1369

1026

1319

1448

2 7 6

Hester, W.

Hewlett, P.

Hjort, L.

Ho, D. W. S.

Hobbs, D. W.

Hoff, A.

Hofmann, P.

Holand, I.

Holland, T. C.

Horiguchi, T.

Hover, K. C.

Howdyshell, P. A.

HSU, T. C .

Hudson, L. J.

Hudson, S. B.

Hughes, B. P.

Hughes, D. C.

Huovinen, P.

Hyrve, 0.

Ivanyi, G.

Iyer, L. S.

Jacobs, J.

Janssen, D. J.

Jenkins, J. C.

Jennings, H. M.

Jensen, A. P.

Jerath, S.

1075, 1166

1053

1205

1552

1008

1268

1224

1449

1450, 1451, 1452

1553

1453, 1554

1076

1182, 1269, 1320

1139

1027

1167, 1206, 1555, 1556

1321

1207

1322

1054

1140

1109

1454, 1557, 1612

1009

1558, 1559, 1560

1225

1455

277

John, R.

Johnston, C. D.

Jones, K.

Joshli, R. C.

Joyce, R.

Kaar, P. H.

Kadlecek, V.

Kaetzel, L. J.

Kageyama, H.

Kaneuji, M.

Kao, C. C.

Katsaragakis, E. S.

Kawamura, M.

Khaloo, A. R.

Kholmyanskii, M. M.

Kim, K.

Klausen, D.

Klieger, P.

Klink, S. A.

Knutson, M. J.

Koch, R.

Kordina, K. 0.

Kotsovos, M. D.

Krenchel, H.

Kudlapur, S.

Kunghan-Roy

LaFraugh, R. W.

1456

1010, 1028, 1029, 145'7

1561, 1562

1323

1370

1110

1141

1563

1168

1111

1055

1458

1459

1564

1270

1460

1142

1565

1324, 1325

1461

1566

1371

1143, 1226

1438, 1462

1613, 1614

1169

1372

2! '7 8

Lane, D.

Larsen, T. J.

Lawrence, C. D.

Lee, D.

Lee, G. C.

Leins, W.

Lenschow, R. J.

Lesage, R.

Losberg, A.

Luke, K.

Luong, M. P.

Luther, Mark D.

Lydon, F. D.

Ma, J.

Maage, Magne

Macadam, D.

Mahmood, N.

Mailhot, G.

Malhotra, V. M.

Malvern, L. E.

Mangat, P. S.

Mangialardi, T.

Marusin, S.

Maschmann, M.

Maslehuddin, M.

Mather, B.

1463

1056

1183

1112

1567

1077

1326

1271

1113

1568

1464

1615

1170, 1373

1114

1465, 1466

1272

1030

1144

1031, 1032, 1033, 1057, 1078, 1115, 1116, 1171, 1184, 1227, 1374, 1467, 1468, 1469, 1616

1375

1117

1569

1470, 1570

1058

1617

1034

279

M a t s u f u j i , Y .

M a t s u s h i t a , H .

McBee, W . C .

McCurr ich, L .

McLean, F . G .

Meht.a, P . K .

M e i n i n g e r , R. C .

Meland, I .

M i j n s b e r g e n , J.

Mindess , S.

Mobasher, B .

Montague, P . Mor, A.

Morgan, D . R .

M o r r i s , M.

Muguruma, H .

Mukher jee , P . K .

Murav l jov , M.

Murayama, Y .

Murray, A. McC

Myers, J . D .

Nagaraj, T . S .

Nagataki, S .

Na ik , T . R.

Nakamura, N .

Nakashima, K .

Nallathambi, P .

1471

1079

1145

1376

1571

1118

1080

1228

1327, 1572

1208, 1328

1573

1209

1273

1011

1472

1377

1081

1378

1379

1473

1172

1574

1474

1146, 1618

1380

1274

12 7 5 , 1.32 9

Nasser, K. W.

Nawy, E. G.

Neal, B. F.

Nelson, E. L.

Nelson, J. A.

Neville, A.

Ngab, A. S.

Noor, F. A.

Numata, S.

O'Brien, J. S.

O'Neil, D. J.

Oh, B. H.

Ohama, Y.

Ohgishi, S.

Okada, K.

Okamoto, H.

Ono, S.

Orchard, D. F.

Osidze, V. I.

Ozyildirim, H. C.

Pandit, G. S.

Pankratov, V. L.

Park, S. B.

Pedersen, N.

Penttala, V.

Perdikaris, P. C.

1381

1082, 1475, 1476

1083

1575

1084

1477

1173, 1185

1210

1382

1330

1085

1383, 1478

1276, 1331, 1479

1332

1086

1480

1333

1012

1147

1087, 1186, 1229, 1334, 1384, 1481, 1576, 1577

1088

1035

1385

1578

1386

1387, 1388, 1482

281

P e r r a t o n , D .

P e s c h , L .

P e s s i k i , S . P .

P e t e r m a n , M. B .

P e t r o s k i , H . J.

P f e i f e r , D . W .

P h i l l e o , R.

P i a s t a , J.

P i g e o n , M.

P i t t , J. M .

P l a n t e , P .

P 1 a t ou , J . P o n s , G .

P o o n , , C . S .

P o p o v i c s , S . P o p p e , J. B .

P o r t e r , L . C .

P u e c h , M.

R a i t h b y , K . D .

R a m a k r i s h n a n , V .

Rameyy, G . E .

R a s m i i s s e n , T . H .

R a v i n a , D .

R e i d e n o u e r , D . R.

R e i n h a r d t , H . W .

R e i n h o l d , R . E .

R i l e y , R. C .

1579

1148

1483, 1580

1230

1484

1485

1277, 1389, 1486

1487

1390, 1.488, 1489

1490

1619

1036

1581

1491

1492

1187

1119

1089

1013, 11149

1090, 1188, 1.278

1279, 1280

1335

1582

1037

1150, 1211, 1.336, 1391, 1392

1393

1493

Rjegovic, D.

Roberts-Seymour, M.

Robison, R.

Robson, G.

Rodway, L. E.

Rollings, R. S.

Ronne, M.

Roper, H.

Rosenberg, A. M.

Rosner, J. C.

Roy, D. M.

Russell, R. 0.

Sabnis, G. M.

Saito, M.

Sakata, K.

Sakuta, M.

Salah el Din, A. S.

Samarin, A.

Sandonato, A. G.

Sarkar, S. L.

Saucier, K. L.

Sauer, J. A.

Schiessl, P.

Schmidt, H.

Schmidt, W.

Schminke, P.

Schneider, U.

1494

1495

1583

1496

1584

1394

1620

1395

1091, 1621

1092

1038, 1337, 1497, 1622

1014

1231

1232, 1281, 1396, 1585

1059, 1338, 1339

1498, 1499

1189

1500

1060

1501, 1502

1151

1061

1503

1340

1039

1093

1233

283

S c h o n l i n , K .

S c h r a d e r , E . K .

Schubenz , D . Seabrook , P . I .

S e i t z e r , R .

S e n b e t t a , E .

S e y i t a p r a s i r t , P .

S h a e l e s , C . A.

Shah, S . P .

S h i h , T . S .

Sh i i -na , K .

S h i r l e y , S . T .

S h r i v e , N . G .

S i l v a , M. A . G .

Skal-ny, J.

Skoberne , T .

Smadi, M. M.

Smi th , K . G .

Smutze r , R. K .

Sommer, H .

S o r e n s e n , E . V.

S o r o u s h i a n , P .

Spel-lman, D . L .

S p r i - n k e l , M . M .

S t a y n e s , B . W .

S t o c k , A. F .

Stol.1, u . w .

1504, 1.586

1341

1120

1587

1397

1505

1174

1588

1152, 1234, 1282, 1506, 1507

1589, 1590

1283

1591

1342

1398

1062, 1.508

1399

1343, 1.509, 1623

1284, 1285

1344

1121

1235

1400, 1.401

1040

1153, 1.345, 1592, 1593

1510

1154, 1.594

1346

:2 a 4

Su, E. C. M.

Sullivan, B. R.

Sullivan, C. L.

Sullivan, T. A.

Suzuki, K.

Swamy, R. N.

Tanahashi, I.

Tasuji, M. E.

Tayabji, S. D.

Taylor, M. A.

Tazawa, Y .

Tepfers, R.

Terrien, M.

Thomas, M. D. A.

Tikalsky, P. J.

Tinic, C.

Tjugum, 0. M.

Tognon, G.

Torrent, R. J.

Tsai, W. T.

Tse, E. W.

Tynes, W. 0.

Van Mier, J. G. M.

Virtanen, J.

Vos, E.

Waagaard, K.

Walker, H. N.

1595, 1596

1597

1236

1063

1347

1041, 1402, 1624

1511

1122, 1155

1512

1015

1286, 1348

1094, 1156, 1157, 1287

1175

1625

1598

1349

1350

1176

1095

1599

1403

1042

1404

1288

1237

1096

1212

285

Wall, J. S.

Wang, P. T.

Warner, R. F.

Washa, G. W.

Weigler, H.

White, R. M.

Whiting, D.

Willam, K.

Williamson, R.

Wilson, A.

Wilson, H. S.

Wittmann, F. H.

WoeYfl, G. A.

Wolsiefer, J.

Xu, J.

Yankelevsky, D. Z.

Yimprasert, P . Yong, Y-K

Young, J. F.

Zaitsev, Y. V.

Zhang, B.

Zia, P .

Zielinski, A. J.

Zielinski, Z. A.

1600

1097, 1123

1352

1 0 4 3

1 2 1 3

1 1 9 0

1513, 1514, 1515, 1 6 0 1

1405

1353, 1354

1044

1 6 0 2

1 1 5 8

1191

1 2 8 9

1516

1 5 1 7 , 1626

1064

1603

1016, 1124, 1238, 1355

1356, I t406

1518

1519

1192

1239

SUBJECT INDEX

abrasion

admixture-chemical

admixture-mineral

aggregate

1451, 1578, 1594

1011, 1086, 1112, 1153, 1188, 1236, 1262, 1279, 1347, 1386, 1434, 1470, 1503, 1539, 1566,

1035,

1186, 1218, 1235, 1276, 1292, 1318, 1348, 1381, 1393, 1426, 1443, 1455, 1468, 1485, 1501, 1542, 1553, 1572 , 1583, 1605, 1617, 1624,

1092,

1053, 1062, 1091, 1093, 1116, 1121, 1159, 1168, 1217, 1218, 1238, 1250, 1271, 1273, 1284, 1319, 1367, 1378, 1389, 1397, 1435, 1446, 1474, 1475, 1513, 1514,

1569, 1570, 1544, 1561,

1049, 1101, 1195, 1223, 1250 , 1277 , 1301, 1321, 1368, 1382, 1399, 1427, 1444 , 1457, 1469, 1486, 1503, 1543, 1565, 1576, 1584, 1606, 1618, 1625

1056, 1118, 1202, 1225, 1251 , 1286, 1308, 1323, 1370, 1384, 1403, 1428, 1445, 1459, 1470, 1488, 1513, 1545, 1566, 1577, 1587, 1607, 1620,

1065, 1081, 1107, 1109, 1124, 1129, 1179, 1184, 1227, 1231, 1260, 1261, 1277 , 1278 , 1341, 1344, 1381, 1385, 1399, 1430, 1455, 1469, 1486, 1495, 1515, 1530, 1562, 1565, 1584, 1613

1086, 1165, 1203, 1227, 1254, 1288, 1311, 1331, 1374, 1389, 1408, 1437, 1446, 1465, 1474, 1495, 1536, 1548, 1568, 1579, 1598, 1615, 1621,

1087, 1181, 1205, 1228, 12 67 , 1289, 1313, 1334, 1380, 1390, 1414, 1440, 1451, 1467, 1481, 1497, 1541, 1551, 1570 , 1582, 1603, 1616, 1622,

1004, 1008, 1010, 1012, 1027,

1057, 1059, 1074, 1083, 1090, 1111, 1115, 1119, 1123, 1132, 1133, 1145, 1154, 1157, 1158, 1169, 1170, 1172, 1176, 1204,

1029, 1039, 1040, 1043, 1055,

1220, 1224, 1234, 1240, 1243,

287

a i r entrainment

bond-concrete t o c o n c r e t e

bond-concrete t o s teel

b r idge

br idge deck

capping

cement

ch 1 cl r i de s

compressive s t r e n g t h

1266, 1268, 1275, 1277, 1299, 1308, 1316, 1322, 1324, l328, 1333, 1361, 1362, 1366, 11373, 13'79, 1407, 1419, 1431, 1440, 1441, 1463, 1487, 1522, 11587, 1602

( see d u r a b i l i t y )

1017, 1396, 1476, 1571, 1585, 16100

1219, 1237, 1392, 1429, 153c;, 1539, 1IS66, 1590

1073, 1098, 1130, 1134, 1161., 1188, l :L90, 1198, 1214, 12251, 1254, 1278, 1372, 1449, 1520

(see br.idge)

1080, 1103, 1537

1014, 1329, 1043, 1048, 1084, 1089, 1106, 1125, 1199, 1215, 1274, 1280, 1298, 1313, 131!3, 1395, 1397, 1417, 1439, 1466, 1477, 1491, 1492, 1508, 1614

1091, 1096, 1235, 1364, 136'7, 1490, 1497, 1530, 1573, 1576, 1577, 1619

1006, 1009, 1010, 1012, 1015, :L020, 1023, 1027, 1030, 1032,. 1036, 1038, 1043, 1057, 1061,. :1072, 1074, 1078, 1079, 1080,. 1087, 1090, 1092, 1105, 1125,. 1129; 1132, :1154, 1163, 1174, 1177, 1209, 1210, 1250, 1253, 1265, 1283, 1313, 1314, 1325, 1332, 1342, 1343, 1373, 1374, 1404, 1433, 1450. 1452,

1139, 1166, 1184, 1226, 1255, 1285, 1316, 1334, 1346, 1377, 1438, 1456,

1143, 1146,, 1169, 1171,, 1194, 1204,, 1231, 1234,,

1302, 1310,, 1323, 1324,, 1339, 1340,

1384, 1401,

1460, 1462,

1260, 126L

1366, 1371,

1443, 1445,

1479, 1483, 1489, 1491, 1512, 1516, 1523, 1531, 1535, 1537, 1542, 1545, 1548, 1558, 1552,

1553, 1572, 1580, 1582, 1599, 1612

\

concrete production

corrosion

cracking

creep

1010, 1036, 1043, 1075, li06, 1121,

1240, 1242, 1255, 1305, 1307, 1314, 1434, 1448, 1450, 1493, 1510, 1524, 1543, 1565, 1598,

1160, 1214, 1216,

1024, 1035, 1085, 1407, 1430, 1444, 1498, 1499, 1617

1071 , 1173, 1206, 1233, 1295, 1336, 1362, 1390, 1416, 1462, 1506, 1526, 1626

1096, 1105, 1178, 1193, 1208, 1209, 1265, 1269, 1303, 1317, 1342, 1355, 1365, 1366, 1394, 1396, 1417, 1423, 1464, 1472, 1507, 1517, 1555, 1556,

1001, 1002, 1005, 1041, 1046, 1047, 1083, 1099, 1100, 1125, 1126, 1129, 1159, 1160, 1163, 1185, 1224, 1243, 1246, 1247, 1259, 1301, 1327, 1332, 1363, 1381, 1393, 1432, 1480, 1509, 1624

cryogenic temperature (see temperature)

curing

cyclic load

deicing agent

1012, 1013, 1023, 1139, 1176, 1187, 1276, 1337, 1345, 1429, 1434, 1445, 1497, 1504, 1525, 1607, 1625

(see fatigue)

1050, 1139, 1222, 1267, 1355, 1460, 1527, 1611,

1089, 1477,

1137, 1196, 1217, 1270, 1330, 1359, 1387, 1404, 1433, 1482, 1518, 1588,

1011, 1059, 1102, 1130, 1173, 1244, 1261, 1338, 1402, 1615,

1078, 1216, 1373, 1447, 1538,

1058, 1151, 1230 , 1298, 1411, 1474, 1528, 1618

1236, 1485,

1158, 1197, 1221, 1291, 1333, 1361, 1388, 1412, 1456, 1484, 1521, 1623,

1016, 1066, 1104, 1140, 1181, 1245, 1297, 1351, 1422, 1623,

1133, 1251, 1425, 1448, 1562,

1546

289

drying shrinkage

duct i 1 it y

durabi 1 it y

dynamic modulus

early strength

elast.ic modulus

elevated temperature

fatigue

1125, 1608

1132’6, 1097, 11226, 1294, 1.405

1022, 1024, 1037, 1040, 1060, 1064,

1145, 1148, 1183, 1187, 1207, 1220, 1267, 1286, 1 : 3 1 1 , 1321, 1369, 1370,

1407, 1408, 1428, 1435, 1443, 1446, 1459, 1463, 1470, 1477, 1488, 1489, 1496, 1498, 1505, 1511, 1522, 1539, 1550, 1551, 1568, 1584, 1612, 1614,

1101, 1111,

1385, 1389,

1072

1.025, ;.042, 1.069, ?.115, 1-153, 1-195, 1-229, 1.295, 3.335, 3.374, 1.390, 3.414, 3.437, 3.447, 3.465, 1.479, 3.490, 1.499, 3.513, 1.541, 1.552, 3.586, I. 625

1014, 1017, 3.028, 1084, 1093, 1.107, 1127, 1202, 3.212, 1274, 1280, 3.330, 1378, 1397, 1.402, 1429, 1434, 3.439, 1476, 1480, 3.492, 1556, 1561, 3.593,

1033, 1044, 1070, 1119, 1168, 1201, 1241, 1305, 1345, 1376, 1395, 1418, 1439, 1453, 1466, 1486, 1494, 1500, 1514, 1544, 1554, 1598,

1034, 1049, 1091, 1129, 1172, 1205, 1249, 1306, 1368, 1380, 1399, 1426, 1441, 1457, 1467, 1487, 1495, 1503, 1515, 1547 , 1563, 1610,

1041, 1081,

1218, 1273, 1347, 1351, 1409, 1425, 1461, 1.475, 1493, 1520, 1604

1120, 1121,

(see modulus of e1asticit.y)

(see termperature)

1003, 1013, 1-026, 1068, 1073, 1-077, 1096, 1098, 3.112, 1136, 1137, 3.142, 1:1517, 1163, 1.180, 1191, 1192, 3.194, 1232, 1256, 3-257, 1268, 1269, 3.281, 1290, 1300, 3.304, 1339, 1352, 3.358,

1044, 1079, 1128, 1149, 1182, 1203,

1282, 1320, 1363,

1258,

1.045, 1.094, 1135, 1.156, 1189, 1213, 1265, 1287, 1326, 1365,

2130

fibers

fire endurance

flexural strength

f l y ash

fracture toughness

freeze thaw

1377, 1383, 1387, 1388, 1392, 1398, 1403, 1412, 1415, 1442, 1464, 1471, 1476, 1482, 1512, 1517, 1518, 1575, 1581, 1585, 1595, 1596

1225, 1278, 1341, 1394, 1553

(see temperature)

1010, 1023, 1027, 1064, 1072, 1087, 1092, 1135, 1136, 1162, 1203, 1239, 1264, 1285, 1293, 1294, 1309, 1323, 1329, 1334, 1356, 1379, 1383, 1419, 1442, 1443, 1456, 1475, 1512, 1553

(see admixture-mineral)

1264, 1275, 1303, 1462

1025, 1049, 1115, 1220, 1288, 1344, 1418, 1481, 1494, 1548,

1031, 1034, 1037, 1070, 1075, 1087, 1148, 1167, 1184, 1235, 1254, 1274, 1292, 1295, 1300, 1348, 1382, 1390, 1441, 1463, 1467,

1496, 1528, 1529, 1563, 1567

1486, 1488, 1489,

frost resistance (see freeze thaw)

heat of hydration 1228, 1555

high early strength (see early strength)

high range water reducers (see admixture-chemical)

high- strength 1028, 1041, 1075, 1109, 1133, 1159, 1173, 1198, 1218, 1241, 1263, 1277, 1294, 1309,

1029, 1042, 1082, 1110, 1138, 1161, 1176, 1214, 1224, 1242, 1268, 1286, 1298, 1312,

1031, 1033, 1050, 1053, 1085, 1086, 1116, 1117, 1151, 1152, 1162, 1166, 1178, 1179, 1215, 1216, 1225, 1230, 1247, 1248, 1271, 1272, 1289, 1291, 1299, 1307, 1318, 1322,

1042, 1111, 1186, 1285, 1334 , 1408, 1468, 1490, 1546,

1039, 1065,

1118, 1158, 1168, 1185, 1217, 1240, 1252, 1276, 1293 , 1308,

1101,

1328,

291

h i g h t e m p e r a t u r e

impact s t r e n g t h

i n - s i t u s t r e n g t h

l a t e x

l i g h t w e i g h t aggregate

m i c r o c r a c k i n g

m i c r o s t r u c t u r e

m i x i n g

modulus o f e l a s t i c i t y

m u l t i a x i a l l o a d i n g

n o n d e s t r u c t i v e t e s t

1 3 3 1 , 1333, 1 3 3 7 , 1.354, l:36O, 1 3 6 1 , 1.379, 1 3 8 0 , 1 3 8 6 , 1411, 1 4 1 3 , 1 4 1 9 , 1 4 2 7 , 1431, 1 4 4 7 , 1 4 5 0 , 1451, 1 4 5 6 , 1 4 6 8 , 1 4 7 4 , 1 4 8 6 , l l502, 1 5 0 8 , 1 5 0 9 , 1 !521 , 1 5 2 5 , 1 5 2 7 , 11538, 1 5 4 0 , 1 5 4 6 , 1!559, 1 5 6 0 , 1 5 6 2 , 1 5 7 5 , 1 5 8 3 , 1 5 8 7 , 1 5 9 1 , 1t502, 1 6 0 3 , 1 6 0 9 , 1610, 1 6 1 1 , 1 6 2 1

1 3 4 3 , 1 3 7 0 , 1 3 8 9 , 1 4 2 0 , 1 4 4 8 , 1 4 5 7 , 1 4 9 6 , 1513, 1 5 2 9 , 1 5 4 9 , 1 5 6 4 , 1 5 8 9 , 1 6 0 5 , 1 6 1 5 ,

1 3 4 8 , 1 3 7 5 , 1 4 0 7 , 1 4 2 4 , 1 4 4 9 , 1 4 6 7 , 1 5 0 1 , 1 5 1 9 , 1 5 3 2 , 1558 , 1 5 6 5 , 159C1, 1 6 0 5 , 1 6 1 E ,

(see t e m p e r a t u r e )

1 0 1 8 , l :150 , 1 1 9 2 , 1 2 1 1 , 13451, 1 3 6 0 , 1 3 7 5 , 1 3 9 1 , 1 3 9 8 , 1 4 0 0 , 1 4 0 1 , 1 4 2 0 , 1 4 2 4 , 1 4 7 8

(see n o n d e s t r u c t i v e t e s t )

1 0 2 3 , l : lO2, 1 1 1 7 , 1 1 4 0 , 135c1, 11372, 1 4 7 9 , 1 5 2 0 , 1 5 7 4 , 1 5 9 2 , 1 5 9 3

( see a g q r e g a t e )

( s e e c r a c k i n g )

1 0 1 6 , 1 0 2 2 , 1 0 6 0 , 1 0 6 9 , 1 0 7 2 , 1111, 1205, 1 2 3 3 , 1 2 6 4 , 1 3 2 1 , 1 3 2 8 , 1 4 1 7 , 1 5 0 0 , 1502, 1 5 0 5 , 1 5 5 8 , 1t559, 1 5 6 0

(see c o n c r e t e p r o d u c t i o n )

1 0 0 9 , 1 0 4 7 , 1 0 6 6 , 1 0 6 8 , 1 0 7 4 , 1 1 2 5 , 1:154, 1 1 6 2 , 1 1 8 1 , 1 2 0 3 , 1 2 5 3 , 1 2 8 3 , 1 2 9 3 , 1 2 9 4 , 1 3 2 5 , 1 3 3 7 , 1.362, 1 4 1 3 , 1 4 1 9 , 1455, 1 5 1 2 , 1iS32

1 1 2 2 , 1 1 3 8 , 1155, 1239, 1 2 5 2 , 1.62 6

1 0 1 9 , 11332, 1 0 5 1 , 1 1 4 1 , 1 1 4 4 , 1 1 7 1 , 1 1 7 5 , 1 2 0 8 , 1 2 2 1 , 1 2 4 8 , 1 2 8 7 , 1335, 1 3 4 6 , 1 3 5 8 , 1421.,

1 5 2 6 , 11580 1 4 3 8 , 1 4 6 4 , 1 4 7 3 , 1 5 0 4 , 1 5 2 4 ,

2 92

(see pavement) overlay

patching

pavement

permeability

placing

polymer

porosity

proportioning

quality control

shear strength

shrinkage

(see pavement)

1014, 1073, 1114, 1188, 1278, 1330, 1410, 1475, 1514, 1613

1027, 1064, 1068, 1077, 1093, 1109, 1120, 1131, 1132, 1199, 1202, 1223, 1279, 1280, 1284, 1341, 1350, 1394, 1439, 1449, 1454, 1481, 1492, 1493, 1536, 1543, 1578,

1069, 1113, 1153, 1266, 1285, 1409, 1461, 1512, 1594,

1183, 1190, 1207, 1249, 1296, 1306, 1334, 1337, 1364, 1370, 1376, 1395, 1419, 1423, 1453, 1481, 1495, 1497, 1504, 1511, 1530, 1534, 1557, 1570, 1573, 1576, 1577, 1579, 1586, 1597, 1601, 1606, 1619, 1625

(see concrete production)

1009, 1020, 1023, 1048, 1061, 1064, 1082, 1085, 1134, 1191, 1263, 1300, 1309, 1331, 1359, 1418, 1442, 1460, 1472, 1510, 1570, 1574, 1614

1038, 1062, 1072, 1177, 1198, 1207, 1255, 1355, 1443, 1541, 1559

(see concrete production)

1039, 1076, 1103, 1146, 1151, 1166, 1195, 1227, 1305, 1306, 1353, 1410, 1446, 1450, 1523, 1524, 1527, 1528, 1538, 1540

1268, 1442, 1553, 1571, 1600

1002, 1008, 1041, 1043, 1087, 1099, 1113, 1114, 1130, 1140, 1193, 1231, 1250, 1259, 1412, 1421, 1489, 1509, 1615, 1623,

1009, 1016, 1021, 1046, 1049, 1083, 1100, 1102, 1104, 1124, 1125, 1129, 1173, 1181, 1185, 1243, 1246, 1247, 1261, 1372, 1402, 1422, 1432, 1454, 1588, 1592, 1608, 1624

293

silica fume (see admixture-mineral)

skid resistance (see abrasion)

slag (see admixture-mineral)

slump test (see workability)

strain capacity 1003, 1108, 1189, 1213, 1258, 1270, 1317, 1326, 1356, 1406, 1415, 1419

stress-strain relationship 1003, 1007, 1015, 1054, 1067, 1097, 1108, 1110, 1117, 1122, 1123, 1155, 1178, 1209, 1210, 1234, 1253, 1281, 1294, 1302, 1303, 1320, 1340, 1343, 1357, 1365, 1371, 1404, 1405, 1416, 1506, 1516, 1564, 1599, 1624

sulfates

sulphur concrete

sulphur impregnation

temperature

tensile strength

ultrasonic test

water-cement ratio

workability

(see durability)

1036, 1063, 1145, 1160, 1212, 1222

(see sulphur concrete)

1114, 1126, 1206, 1291, 1299, 1310, 1314, 1345, 1354, 1371, 1452, 1525, 1544, 1547, 1551, 1555, 1556, 1567, 1589, 1604, 1608, 1613

1005, 1009, 1054, 1055, 1088, 1095, 1147, 1150, 1170, 1175, 1211, 1232, 1263, 1281, 1336, 1349, 1406, 1413, 1458, 1478, 1574, 1585,

1030, 1061, 1108, 1154, 1180, 1239, 1294, 1356, 1416, 1484, 1 6 2 6

1041, 1052, 1066, 1074, 1132, 1143, 1156, 1169, 1203, 1210, 1256, 1257, 1304, 1315, 1392, 1400, 1433, 1455, 1517, 1535,

(see nondestructive test)

1004, 1074, 1076, 1090, 1200, 1204, 1292, 1353, 1483, 1488, 1531, 1534, 1 5 4 1

1027, 1053, 1061, 1065, 1074, 1101, 1116, 1184, 1231, 1238,

294

1260, 1382, 1455, 1528, 1542, 1569, 1612, 1624

295

Section I1

High Performance Fiber Reinforced Concrete

1978

2001. Kasperkiewicz, J., "REINFORCEMENT PARAMETER FOR FIBER CONCRETE," Bulletin de 1'Academie Polonaise des Sciences, Serie des Sciences Techniques, Vol. 26, NO. 1, 1978, pp. 65-72.

Different parameters used in the analysis of reinforcing effect of fibers in FRC are not directly applicable in the case of linearized fibers. A new parameter, q, being proportional to the total average length of fibers reinforcing the cross section of FRC specimens is proposed. Application of the parameter q to the experimental results from flexural, tensile, and impact strength tests, performed on concrete matrices reinforced with different types of steel fibers of 3-dimensional and l-dimensional orientation yielded satisfactory results. The coefficient of correlation has always been better than 0.6 even when quite different test groups have been compared.

296

1979

2002. K a s p e r k i e w i c z , J . , "TENSILE STRENGTH AND ULTIMATE STRAIN I N STEEL FIBER REINFORCED CONCRETE [WYTRZMALOSCI ODKSZTALCALNOSC GRANICZNA PRZY ROZCIAGANIU FIBROBETONU Z WLOKNEM STALOWYM]," Mechanika T e o r e t y c z n a i Stosawana , V o l . 1 7 , N o . 1, 1979, pp. 19-34.

F i b e r c o n c r e t e spec imens reinforced w i t h 2 % b y volume hooked s tee l f ibers have been tes ted i n d i rec t t e n s i o n . The f i b e r s were either o r i e n t e d i n two-dimens ions o r m a g n e t i c a l l y a l i g n e d i n one d i m e n s i o n . The s t r a i n a n d e l o n g a t i o n of t h e spec imens were measured u s i n g d i f f e r e n t t e c h n i q u e s . The f a i l u r e of a l l spec imens was a lways d u c t i l e , and t h e specimens reinforced i n o n e d imens ion showed d i s t i n c t s t r a i n h a r d e n i n g b e h a v i o r a n d m u l t i p l e c r a c k i n g .

2003. K o m l o s , K . , "WORKABILITY OF CONCRETE MIXES WITH RANDOMLY SPACED GLASS FIBERS [SPRACOVATEL NOST BETONOVYCH ZMESI S NAHODNE ROZPTYLENYMI SKLENYMI VLAKNAMI]," S t a v e b n i c k y Casopis, V o l . 2 7 , N o . 6 , J u n e 1979, pp. 361-376.

An i n v e s t i g a t i o n of c o n c r e t e mixes w i t h randomly spaced g l a s s fibers i s ca r r i ed ou t . T h e volume contents u s e d w e r e 0 .75 , 1 . 2 5 , 2 , and 2 . 5 p e r c e n t by volume. The w o r k a b i l i t y of t h e mixes w i t h randomly spaced f ibe r s w a s inves t iga ted . An e x p l a n a t i o n i s g i v e n as t o why FRC w o r k a b i l i t y decreases as t h e f iber c o n t e n t i n c r e a s e s . Comparison i s made w i t h p l a i n c o n c r e t e .

2004. R a h i m i , M . , and C . Kesler, "PARTIALLY STEEL FIBER REINFORCED MORTAR," Journal of t h e S t r u c t u r a l Div is ion , ASCE, V o l . 105 , No. ST1, J an 1 9 7 9 , pp. 101-109.

T h e major object ive of t h i s s t u d y was t o d e t e r m i n e t h e m o s t appropriate t h i c k n e s s of t he r e i n f o r c e d p o r t i o n of t h e f l e x u r a l member w i t h regard t o s t r e n g t h , mode of f a i l u r e , economy, and p r a c t i c a l i t y . T h i s s t u d y w a s l i m i t e d t o a s i n g l e specimen s i z e w i t h f i b e r - r e i n f o r c e d mortar u s i n g one f iber geometry a n d one f i b e r c o n t e n t . t h e t h i c k n e s s of t h e f iber r e i n f o r c e d l a y e r v a r i e d between 0 . 1 5 t o 1 . 5 i n c h e s .

297

2005. Swamy, R . N . , and H . Stavrides, "INFLUENCE OF F I B E R REINFORCEMENT ON RESTRAINED SHRINKAGE AND CRACKING," J o u r n a l of t h e American C o n c r e t e I n s t i t u t e , N o . 2 , Mar 1979, pp. 4 4 3 - 4 6 0 .

Drying s h r i n k a g e , when r e s t r a i n e d , c o n t r i b u t e s t o n e a r l y a l l t h e c r a c k i n g observed i n c o n c r e t e members before l o a d i n g . A free s h r i n k a g e t es t c a n n o t t h e r e f o r e give t h e t r u e p o t e n t i a l f iber r e i n f o r c e m e n t t o resist r e s t r a i n e d s h r i n k a g e stresses and t o c o n t r o l s h r i n k a g e c r a c k i n g . A r i n g type of r e s t r a i n e d s h r i n k a g e t es t i s reported t o d e m o n s t r a t e t h e a b i l i t y of sho r t , discrete fibers s u c h as po lypropy lene , g lass , a n d s teel t o c o n t r o l c r a c k i n g and resist t e n s i l e stresses a r i s i n g from r e s t r a i n e d s h r i n k a g e . Three series of f ree and r e s t r a i n e d s h r i n k a g e tes ts are reported u s i n g d i f f e r e n t mixes, t y p e of f ibers , and f iber c o n t e n t , I t i s shown t h a t t h e p r e s e n c e o f f ibers e x e r c i s e s a clear b u t small r e s t r a i n t t o f r e e s h r i n k a g e , and r e d u c e s d r y i n g s h r i n k a g e by a p p r o x i m a t e l y 2 0 % . When s h r i n k a g e i s r e s t r a i n e d , f iber r e i n f o r c e m e n t d e l a y s t h e f o r m a t i o n of t h e f i rs t crack, p r e v e n t s sudden f a i l u r e observed i n u n r e i n f o r c e d matrices, e n a b l e s t h e composite t o e x p e r i e n c e m u l t i p l e c r a c k i n g p r io r t o f a i l u r e , and r e d u c e s t h e crack width s u b s t a n t i a l l y . T h e f i be r r e i n f o r c e d spec imens were able t o resist 50 t o 1 0 0 p e r c e n t more t e n s i l e stresses, a n d c o n t i n u e d t o resist t h e shr inkage stresses even a f t e r 8 t o 1 2 months.

2006. Swamy, R . N . , S . A l - T a ' a n , and S . R . A l i , "STEEL F I B E R S FOR CONTROLLING CRACKING AND DEFLECTION," C o n c r e t e I n t e r n a t i o n a l , V o l . 1, N o . 8, Aug 1 9 7 9 , pp. 4 1 - 4 9 .

T e s t s are r e p o r t e d t o show t h a t t h e a b i l i t y o f f i b e r r e i n f o r c e m e n t t o c o n t r o l c r a c k i n g and d e f l e c t i o n i s a more i m p o r t a n t c o n s i d e r a t i o n i n practice t h a n improvements i n s t r e n g t h c h a r a c t e r i s t i c s . Three types of tes ts w i t h s t e e l f ibers are reported. I n tes ts of n o t c h e d beams i n f l e x u r e , t h e f i b e r s a re shown t o change t h e t e n s i l e c r a c k i n g b e h a v i o r from a n i n h e r e n t l y u n s t a b l e and u n c o n t r o l l e d s t a t e i n t o a slow, c o n t r o l l e d c r a c k growth . t h e p r e s e n c e of f iber r e i n f o r c e m e n t i s a l so shown t o i n c r e a s e t h e s t i f f n e s s a n d r e d u c e t h e d e f l e c t i o n of c o n v e n t i o n a l l y r e i n f o r c e d c o n c r e t e beams. I t a l so e n a b l e s higher grade s tee l and higher s t ee l stresses t o be u s e d w i t h o u t t h e d a n g e r of e x c e s s i v e c r a c k i n g a n d d e f l e c t i o n . T e s t s on f l a t s labs are reported t o show tha t s u b s t a n t i a l i n c r e a s e s i n shear r e s i s t a n c e imparted by the f ibers can be combined w i t h greater i n t e g r i t y of t h e s t r u c t u r a l m e m b e r a f t e r collapse and i n c r e a s e d ene rgy a b s o r p t i o n character is t ics .

2 98

2007 . Walkas, B. ,A. Januszkiewicz, and D . Jeruzal , "CONCRETE COMPOSITE WITH CUT STEEL FIBER REINFORCEMENT SUBJECTED TO U N I A X I A L TENSION," Journal of t h e American Concrete I n s t i t u t e , Vol. 76 , N o . 1 0 , O c t 1979 , pp. 1079-1092.

T h i s paper dea ls w i t h t he inves t iga t ion of t h e cracking behavior, s t r e n g t h proper t ies , and deformation p rope r t i e s of t e n s i l e specimens of concrete re inforced w i t h shor t s t e e l f i b e r s . Specimens w i t h d i f f e r e n t diameter f i b e r s and d i f f e r e n t f i b e r contents were inves t iga ted . I t was noticed t h a t t he addi t ion of c u t s teel f i b e r s t o t h e concrete increases i t s s t r e n g t h but up t o some c r i t i c a l amount of microreinforcement. A volume of s t e e l f i b e r s up t o 1 . 2 % seems t o be the best . The i n f l u e n c e of microreinforcement arrangement on the cracking behavior was analyzed on t h e b a s i s of x-ray photographs. I t was observed t h a t t h e loca t ion of t h e crack depends on the o r i en ta t ion and number of f i b e r s i n t h e cross sec t ion .

299

1980

2008. G h a l i b , M . A . , "MOMENT CAPACITY OF STEEL FIBER REINFORCED SMALL CONCRETE SLABS," J o u r n a l o f t h e American C o n c r e t e I n s t i t u t e , V o l . 7 7 , N o . 4 , J u l ] 1980, pp. 247-257.

- A

An a n a l y t i c a l approach based on experimental data i s u s e d t o d e t e r m i n e t h e u l t i m a t e moment c a p a c i t y and t h e c r a c k i n g moment o f f i b e r re inforced concrete s labs . Assuming a c e r t a i n f a i l u r e mechanism, p r e d i c t i o n e q u a t i o n s are deve loped which give t h e moment capacities, once t h e s p l i t t i n g t e n s i l e s t r e n g t h o f t h e f iber r e i n f o r c e d c o n c r e t e a n d t h e t h i c k n e s s o f t h e slabs are known. The a n a l y t i c a l p r e d i c t i o n s f i t t h e e x p e r i m e n t a l data f o r b o t h one way and t w o way s labs .

2009. Kormeling, H . A . , H . W . R e i n h a r d t , and S . P . Shah, "STATIC AND FATIGUE PROPERTIES OF CONCRETE BEAMS REINFORCED W I T H BARS AND FIBERS," J o u r n a l o f t h e American C o n c r e t e I n s t i t u t e , V o l . 77, No. 1, Jan-Feb 1980, p p . 36-43 .

T o s t u d y t h e i n f l u e n c e o f s t e e l f i b e r s on t h e f a t i g u e b e h a v i o r o f c o n v e n t i o n a l l y r e i n f o r c e d concrete s t r u c t u r e s , beams r e i n f o r c e d w i t h t h r e e d i f f e r e n t volumes o f r e i n f o r c i n g bars were tes ted i n a c o n s t a n t a m p l i t u d e f a t i g u e l o a d i n g . F o r e a c h amount of c o n v e n t i o n a l s t ee l , t h r e e t y p e s of f i b e r s w e r e u s e d . A d d i t i o n o f f i b e r s t o c o n v e n t i o n a l l y r e i n f o r c e d c o n c r e t e beams i n c r e a s e d t h e s t a t i c u l t i m a t e b e n d i n g moment and f a t i g u e l i f e , and decreased, f o r a g i v e n s t a t i c l o a d i n g and a g i v e n number o f c y c l e s , d e f l e c t i o n s and c r a c k w i d t h s . The r e i n f o r c i n g i n d e x parameter, Vf ( l / d ) , a d e q u a t e l y describes t h e v a r i o u s i n f l u e n c e s o f f i b e r s on t h e f a t i g u e b e h a v i o r o f r e i n f o r c e d c o n c r e t e beams. The b e n e f i c i a l e f f e c t s of f i b e r s d i m i n i s h a t h i g h e r volume o f r e i n f o r c i n g bars . R e i n f o r c e d concrete beams subjected t o a constant a m p l i t u d e f a t i g u e l o a d i n g e x p e r i e n c e a n i n c r e a s e i n d e f l e c t i o n s , crack width , a n d a v e r a g e stresses i n t h e bars.

300

2 0 1 0 . Nishioka, K . , S . Yamakawa,Y. Kameda, and S . Akihama, "PRESENT STATUS ON APPLICATIONS OF STEEL FIBER CONCRETE I N JAPAN," I n t e rna t iona l Journal of Cement Composites, Vol. 2 , N O . 4 , NOV 1980, pp. 205-232.

This paper repor t s a review of t he current s t a t u s of appl ica t ions of s t e e l f i b e r concrete i n Japan and t h e research relevant t o these appl ica t ions . The prefabr ica t ion of p a r t i t i o n walls and s t a i r c a s e s , and appl ica t ion t o tunnel l i n ings , pavements and deck s l abs , r e p a i r s and re f rac tory cas tab les a r e discussed. The development of a new pavement construct ion technique t o blend s t e e l f i b e r s i n t o t h e surface layer of f r e s h l y l a i d conventional concrete i s reported. The use of w e t and d r y processes of guni t ing w i t h s t e e l f i b e r s i s a l s o discussed.

2011. Ramakrishnan, V . , T . Brandshaug,W. V . Coyle, and E . K . Schrader, "A COMPARATIVE EVALUATION OF CONCRETE REINFORCED WITH STRAIGHT STEEL FIBERS AND F I B E R WITH DEFORMED ENDS GLUED TOGETHER I N BUNDLES," Proceedings, Journal of t h e American Concrete I n s t i t u t e , Vol. 7 7 , No. 3, May 1980, pp. 135-143.

This paper presents a comparative evaluat ion of 2 types of s t e e l f i be r s used as a re inforc ing mater ia l i n concrete . The f i b e r s were steel f i b e r s 1" long a s well a s 2" long f i b e r s w i t h deformed ends which were glued toge ther i n t o bundles with water-soluble adhesive. The test program included: (1) f l e x u r a l fa t igue ; ( 2 ) s t a t i c f l e x u r a l s t r eng th including s t r a i n def lec t ion , modulus of rupture , load-deflection curves, determination of f i r s t cracking load and determination of t he post cracking s t rength f o r 2 s i z e s of beams; (3) impact s t rength t o f i r s t crack and ul t imate f a i l u r e ; ( 4 ) compressive s t rength ; and 5) p l a s t i c workabili ty including V e b e , slump, and inverted cone tes t immediately a f t e r t e s t i n g and a f t e r 1 hour. The t e s t was r u n using 2 concentrations of co l l a t ed and hooked s t e e l f i b e r s w i t h pozzolan and s t r a i g h t cement mixes. Special care was taken t o i n s u r e consistency w i t h cement, aggregates, admixtures, procedures, and m i x temperatures. One major f inding was t h a t 60% of t he bundled f i b e r s w i t h hooked ends gave e s s e n t i a l l y t h e same composite proper t ies as 100% of t h e s t r a i g h t f i b e r s . Bundling was found t o enable t h e f i b e r s t o be mixed i n t o aggregates without b a l l i n g o r tangl ing .

301

2012. Rider, R. G., and R. H. Heidersbach, "DEGRADATION OF METAL-FIBER REINFORCED CONCRETE EXPOSED TO A MARINE ENVIRONMENT," STP 713, -osion in &ii.xlforcina S tee l in, American Society for Testing and Materials, Philadelphia, Pennsylvania, Aug 1980, pp. 75-92.

The objective of this research was to determine the effects of marine environment on the integrity of metal-fiber-reinforced concrete. Metal fiber reinforced concrete has potentials in the marine structures where the metal fibers may introduce tensile strength, abrasion resistance, and fatigue properties which may justify the added cost when compared to reinforced concrete. Metal-fiber reinforced concrete specimens were tested in flowing seawater and freshwater laboratory exposures. Comparisons were made to specimens exposed in the tidal zone of Narragansett Bay. Freeze-thaw experiments were also conducted. results were obtained using standard and modified ASTM testing procedures as well as electrochemical corrosion rate monitoring techniques. The results indicate that stainless steel fibers are needed in marine applications.

2013. Swamy, R. N., "INFLUENCE OF SLOW CRACK GROWTH ON THE FRACTURE RESISTANCE OF FIBER CEMENT COMPOSITES," International Journal of Cement Composites, Vol. 2, No. 1, Feb 1980, pp. 43-53.

Tests were reported on the fracture behavior of fiber concrete beams subjected to four-point loading in flexure. All beams had a single notch depth, but varying volume fractions of steel, alkali-resistant glass and polypropylene fibers. The beams were tested in a stiff machine, and the crack growth was monitored continuously using a microscope. The process of crack extension, as observed through the microscope, was shown to be complex, and the test results were analyzed in terms of the variations of load, deflection, and apparent fracture toughness with crack growth.

302

1981

2014. B a r r , B . G . , W . T . Evans, and R . C . D o w e r s , "FRACTURE TOUGHNESS'OF POLYPROPYLENE FIBER CONCRETE," I n t e r n a t i o n a l J o u r n a l o f Cement Composites a n d L i g h t w e i g h t Concrete, Vol. 3, N o . 2, May 1981, p p . 115-122.

T h i s p a p e r describes t w o tests which have been developed t o d e t e r m i n e t h e f r a c t u r e t o u g h n e s s o f concrete materials. The f r a c t u r e t o u g h n e s s i s determined from t h e load a t t h e c r a c k i n i t i a t i o n . The effect of i n t r o d u c i n g various amounts o f p o l y p r o p y l e n e f ibers on t h e f r a c t u r e toughness was discussed.

2015. B u t l e r , J. E . , a n d J . Keat ing , "PRELIMINARY DATA DERIVED USING A FLEXURAL CYCLIC MACHINE TO TEST P L A I N AND FIBROUS CONCRETE," Ma te r i aux e t C o n s t r u c t i o n s , Materials and S t r u c t u r e s , V o l . 1 4 , N o . 79, Jan-Feb 1981, pp. 25-33.

A f l e x u r a l c y c l i c l o a d i n g machine was i n v e s t i g a t e d as par t of a s t u d y o f t h e f a t i g u e c h a r a c t e r i s t i c s o f f i b r o u s c o n c r e t e . The per formance o f t h e machine h a s been v e r i f i e d d u r i n g an i n i t i a l program of work i n which t h e effect of t h e ra te of l o a d i n g on t h e u l t i m a t e f l e x u r a l s t r e n g t h of p l a i n and s teel f i b e r c o n c r e t e h a s been d e t e r m i n e d . A d e s c r i p t i o n o f t h e machine, de t a i l s of t h e v e r i f i c a t i o n o f i t s per formance as w e l l as t h e p r o c e d u r e s and r e s u l t s o f t h e i n i t i a l i n v e s t i g a t i o n are d i s c u s s e d .

2016. Hibbert, A . P., and D . J. Hannant, "IMPACT RESISTANCE OF FIBER CONCRETE," Transport and Road Resea rch L a b o r a t o r y Supplementary Report 654, 1981, p p . 1-28.

A d e s c r i p t i o n i s g i v e n f o r t h e d e t e r m i n a t i o n o f t h e impact e n e r g y o f c o n c r e t e r e i n f o r c e d w i t h d i s c o n t i n u o u s f ibers o f s teel o r twis ted f i b r i l l a t e d p o l y p r o p y l e n e f i l m . The d e s i g n and i n s t r u m e n t a t i o n of a Charpy t y p e o f pendulum impact t e s t machine i s o u t l i n e d , t h e machine b e i n g able of comple t e ly f r a c t u r i n g t h e specimen i n a s i n g l e blow. T h i s machine w a s u s e d t o determine t h e ene rgy abso rbed i n t h e f r a c t u r e p r o c e s s , b o t h from t h e a m p l i t u d e of t h e pendulum swing and a l s o from t h e record o f f o r c e deve loped on t h e pendulum head d u r i n g t h e impact. A v a r i e t y of s t e e l f i b e r t y p e s and t w o l e n g t h s o f chopped f i b r i l l a t e d p o l y p r o p y l e n e f i l m w e r e u sed t o produce composi tes w i t h t w o f i be r volume f r a c t i o n s and t h e s e were tested a t two ages. A s w e l l a s b e i n g tes ted i n impact , most of t h e f i b e r c o n c r e t e

303

t y p e s were f a i l e d i n f l e x u r e a t a conven t iona l slow rate of l o a d i n g and t h e energy a b s o r p t i o n was de termined from t h e area under t h e l o a d d e f l e c t i o n cu rve . T h e high work o f f r a c t u r e of these mater ia ls re la t ive t o p l a i n c o n c r e t e i s q u a n t i f i e d and it i s shown by comparison of t h e e n e r g i e s a t g iven d e f l e c t i o n s i n slow and f a s t l oad ing , t ha t t h e work of f r a c t u r e i s n o t p a r t i c u l a r l y ra te s e n s i t i v e .

2017 . Paul , B . K . , M . Po l ivka , and P . K . Mehta, "PROPERTIES OF F IBER REINFORCED SHRINKAGE-COMPENSATING CONCRETE," J o u r n a l of t h e American Concrete I n s t i t u t e , Vol . 78, No. 6, Dec 1981, pp. 488-492.

T e s t s w e r e carried o u t w i t h 2 t y p e s of s teel f ibe r s t o e v a l u a t e t h e i r r e s t r a i n i n g capabi l i ty i n shr inkage-compensat ing c o n c r e t e . The effect o f t h e f ibe r r e in fo rcemen t on t h e compressive f l e x u r a l s t r e n g t h and modulus o f e l a s t i c i t y was i n v e s t i g a t e d . T h e r e s u l t s i n d i c a t e t h a t s t ee l f ibers can be s u c c e s s f u l l y used f o r r e s t r a i n i n g shr inkage-compensat ing cements. I n c l u s i o n of f ibers i n c o n c r e t e improved t h e compressive and f l e x u r a l s t r e n g t h of b o t h p l a i n and c o n v e n t i o n a l l y r e i n f o r c e d shr inkage-compensat ing f iber r e i n f o r c e d c o n c r e t e . The differences i n t h e moduli were i n s i g n i f i c a n t f o r p r a c t i c a l pu rposes . Concrete c o n t a i n i n g b e n t f ibers showed less r e s t r a i n e d expansion and h i g h e r f l e x u r a l s t r e n g t h when compared t o c o n c r e t e w i t h s t r a i g h t f ibers .

2018. Ramakrishnan, V . , W . V. Coyle,L. F . Dahl, and E . K . Schrader, "A COMPARATIVE EVALUATION OF F I B E R SHOTCRETE, I' Concre te I n t e r n a t i o n a l : Design & C o n s t r u c t i o n , Vol. 3, No. 1, Jan 1 9 8 1 , pp. 59-69.

T h i s r e p o r t p r e s e n t s a comparat ive e v a l u a t i o n of t h e performance characterist ics of f iber s h o t c r e t e w i t h f o u r types of s t e e l f i b e r s . T h e f i b e r s used were two types of c o l l a t e d f ibers w i t h deformed ends, s t r a i g h t f ibers, and c u t s tee l t i r e c o r d . Three d i f f e r e n t f iber c o n c e n t r a t i o n s were used a t 0 .6 , 1 . 0 , and 1.3 p e r c e n t . T h e dry-process sanded mix s h o t c r e t e w i t h a water-cement r a t i o of 0 . 4 6 and a 5% e n t a r p e d a i r w a s u sed . T h i r t y s i x p a n e l s were made w i t h 1.5" and 3" t h i c k n e s s e s . T e s t p a n e l s were s h o t i n a raised v e r t i c a l p o s i t i o n a g a i n s t r i g i d plywood forms w i t h open bot toms. Saw and c o r e samples were made from t h e t es t p a n e l s and t h e fo l lowing tes t s were conducted: (1) cube compression t es t i n c l u d i n g u n i t weight; ( 2 ) f l e x u r a l tes ts i n c l u d i n g load d e f l e c t i o n cu rves ; (3) impact t e s t s ; ( 4 ) s h r i n k a g e measurements; and (5) p u l s e

3 04

ve loc i ty and dynamic modulus of e l a s t i c i t y t es t s . Col la ted f i b e r s w i t h hooked ends could be e f f e c t i v e l y used i n shotcre t ing and t h a t t h e y perform wel l . Excellent d i s t r i b u t i o n of f i b e r s was noted from X-ray photos. A l l of t h e shotcre te showed a tremendous a b i l i t y t o absorb impact loading; t h e hooked f i b e r s showing a f a r superior a b i l i t y than the s t r a i g h t f i b e r s . t h e s t a t i c f l exura l t e s t s showed t h a t an exce l len t end anchorage i s e s t ab l i shed i n t h e case of hooked f i b e r s r e s u l t i n g i n a high d u c t i l i t y of t h e sho tc re t e .

2 0 1 9 . Ramakrishnan, V . , W . V. Coyle,V. Kulandaisamy, and E . K . Schrader, "PERFORMANCE CHARACTERISTICS OF F I B E R REINFORCED CONCRETE WITH LOW F I B E R CONTENT," Proceedings, Journal of t he American Concrete I n s t i t u t e , Vol. 78 , No. 5, Sept-Oct 1981, pp. 388-394.

This report p resents t he performance c h a r a c t e r i s t i c s of f i b e r re inforced concrete with low f i b e r content . The f i b e r s used were 2" long co l l a t ed f i b e r s w i t h deformed ends which a r e glued together s ide by s ide i n t o bundles w i t h a water-soluble glue. The t e s t program included compressive s t rength; s t a t i c f l exura l s t r eng th including def lec t ion , modulus of rupture, load-deflection curves, and determination of t he post cracking s t rength ; f l exura l fa t igue ; impact s t r eng th t o f i r s t crack a t ul t imate; pulse ve loc i ty and s t a t i c and dynamic modulus of e l a s t i c i t y ; and p l a s t i c mixing. The complete s e r i e s of t e s t s were r u n f o r t h r e e concentrations of t h e co l l a t ed and hooked s t e e l f i b e r s and f o r t h e corresponding concrete without t h e addi t ion of f i b e r s . A l l f i b e r re inforced concrete showed a tremendous a b i l i t y t o absorb impact loading. Col la t ing enables t h e f i b e r s t o mixed w i t h aggregates without b a l l i n g or tangl ing and these f i b e r s were easy t o handle. T h e s t a t i c f l exura l t e s t shows t h a t an exce l len t end anchorage i s es tab l i shed i n t h e case of hooked s t e e l f i b e r s . The addi t ion of hooked and s t e e l f i b e r s , even i n small quan t i t i e s , considerably improves t h e post-load-carrying capacity and increases t h e toughness index and t h e energy absorbing capaci ty r e s u l t i n g i n a high d u c t i l i t y of t h e composite mater ia l . One se r ious drawback of high s t rength concrete i s i t s lack of d u c t i l i t y . T h i s drawback can be overcome w i t h t h e addi t ion of small q u a n t i t i e s of hooked s teel f i b e r s which w i l l increase t h e u l t imate s t r a i n capaci ty of t he concrete and provide adequate d u c t i l i t y .

305

2020. S c h r a d e r , E . K . , "IMPACT RESISTANCE AND TEST PROCEDURE FOR CONCRETE,'' J o u r n a l o f t h e American C o n c r e t e I n s t i t u t e , V o l . 78, N o . 2, M a r - A p r 1981, pp. 1 4 1 - 1 4 6 .

U n t i l now, t h e materials i n d u s t r y h a s been l a c k i n g a n acceptable and pract ical tes t t h a t d e m o n s t r a t e s t h e re la t ive b r i t t l eness and impact resistance o f v a r i o u s c o n c r e t e mixes and s imi la r c o n s t r u c t i o n mater ia ls . A simple portable and practical tes t h a s been deve loped t h a t pe r fo rms t h i s f u n c t i o n . The number o f impact blows delivered by a d r o p hammer are accumulated u n t i l t h e f i rs t v is ib le c r a c k occurs and u n t i l t h e tes t specimen i s forced t o s e p a r a t e by cont inued i m p a c t i n g . The t e s t is e s p e c i a l l y s u i t e d t o some of t h e newer and t o u g h e r c o n s t r u c t i o n materials such as f i b r o u s c o n c r e t e . I n i t i a l data shows t h a t it can a l so s e r v e as a n i n d i c a t o r o f o t h e r material p r o p e r t i e s such a s t o u g h n e s s , s t r a i n c a p a c i t y , and f a t i g u e pe r fo rmance .

2021. Swamy, R . N . , and S . A. Al-Ta'an, 'IDEFORMATION AND ULTIMATE STRENGTH I N FLEXURE OF REINFORCED CONCRETE BEAMS WITH STEEL FIBER CONCRETE," J o u r n a l of t h e American Concrete I n s t i t u t e , Vol. 78, N o . , 5, Sept-Oct 1981 , pp. 395-405.

T e s t s are reported on t h e i n f l u e n c e o f f i b e r r e i n f o r c e m e n t on t h e de fo rma t ion c h a r a c t e r i s t i c s and u l t i m a t e s t r e n g t h i n f l e x u r e o f concrete beams made w i t h 0 .79 i n c h maximum s i z e a g g r e g a t e s and re inforced w i t h bars w i t h minimum y i e l d s t r e n g t h of 66.7 and 8 9 . 5 k s i . The f i be r concrete was e i t h e r p r o v i d e d o v e r t h e whole d e p t h of t h e beam o r i n t h e e f f e c t i v e t e n s i o n zone o n l y s u r r o u n d i n g t h e s teel bars . While u l t i m a t e s t r e n g t h was increased o n l y m a r g i n a l l y , t h e f i b e r s arrested advanc ing c r a c k s and i n c r e a s e d p o s t c r a c k i n g s t i f f n e s s a t a l l stages o f l o a d i n g up t o f a i l u r e which r e s u l t s i n na r rower crack w i d t h s and s u b s t a n t i a l l y less d e f o r m a t i o n . The tes ts showed t h a t a t f a i l u r e t h e c o n c r e t e compress ive s t r a i n s r e a c h e d v a l u e s of 0 .005 t o 0 .006 and t h e s t ee l bars a t t a i n e d stresses w e l l i n excess of t h e i r y i e l d s t r e n g t h . An u l t i m a t e s t r e n g t h t h e o r y b a s e d on t h e B r i t i s h and American Codes and t a k i n g i n t o c o n s i d e r a t i o n t h e i n c r e a s e d s t ee l s t r a i n s a t f a i l u r e i s p r e s e n t e d and shows v e r y good agreement w i t h t h e s t r e n g t h d a t a . I t i s a l so shown t h a t t h e v a l u e of t h e bond e f f i c i e n c y factor i s not c r i t i ca l t o t h e a n a l y s i s .

306

2 0 2 2 . V i s a l v a n i c h , K . , and A. E . Naaman, "EVALUATION OF FRACTURE METHODS I N CEMENT COMPOSITES," J o u r n a l of t h e E n g i n e e r i n g Mechanics D i v i s i o n , ASCE, V o l . 1 9 7 , Dec 1981, pp. 1155-1171.

The a u t h o r s a t t e m p t t o compare t h e stress i n t e n s i t y factor and f r a c t u r e e n e r g i e s a n a l y t i c a l l y and e x p e r i m e n t a l l y u s i n g double c a n t i l e v e r beams made o u t of f iber r e i n f o r c e d c o n c r e t e , p l a i n c o n c r e t e , and asbestos cement. The stress i n t e n s i t y factor w a s c a l c u l a t e d u s i n g f o u r methods. The f r a c t u r e e n e r g y w a s computed u s i n g th ree t e c h n i q u e s : t h e compliance measured s t r a i n energy t e c h n i q u e , t h e q u a s i - s t a t i c e n e r g y t e c h n i q u e , and t h e of fse t f r a c t u r e ene rgy t e c h n i q u e . The f r a c t u r e toughness c o u l d n o t b e measured for f iber r e i n f o r c e d c o n c r e t e due t o i n s u f f i c i e n t specimen s i z e .

2 0 2 3 . V i s a l v a n i c h , K . , and A . E . Naaman, "FRACTURE METHODS I N CEMENT COMPOSITES," J o u r n a l of t h e Eng inee r ing Mechanics D i v i s i o n , ASCE, Vol. 107, 1981, pp. 1155-1171.

The i n v e s t i g a t i o n r e p o r t e d here i s par t of larger program on t h e f r a c t u r e of c o n c r e t e , FRC, and a s b e s t o s cement c o n c r e t e i n which a systematic eva lua t ion of v a r i o u s l i n e a r - e l a s t i c and e las t ic -p las t ic f r a c t u r e mechanics t e c h n i q u e s i s unde r t aken . The o b j e c t of t h i s paper i s t o compare t h e stress i n t e n s i t y factor and t h e f r a c t u r e ene rgy of t h e s e materials, as o b t a i n e d from d i f f e r e n t a n a l y t i c a l t e c h n i q u e s and from e x p e r i m e n t a l t es t s . I n order t o r educe t h e s i z e effects, doub le c a n t i l e v e r beam specimens a l l o w i n g v a l i d crack l e n g t h s of up t o 1 6 " w e r e u s e d . Several t es t measurements w e r e made s i m u l t a n e o u s l y t o allow t h e e v a l u a t i o n of s e v e r a l f r a c t u r e ene rgy t e c h n i q u e s f r o m t h e same specimen. The f r a c t u r e t e c h n i q u e s used i n c l u d e : (1) three a n a l y t i c a l methods t o de te rmine t h e stress i n t e n s i t y f r ac to r ; ( 2 ) t h e compliance measured s t r a i n ene rgy t e c h n i q u e ; t h e q u a s i - s t a t i c ene rgy measuring t e c h n i q u e ; and ( 4 ) an e n e r g y measuring t e c h n i q u e d e f i n e d as t h e o f f s e t f r a c t u r e ene rgy t e c h n i q u e t h a t takes i n t o accoun t permanent de fo rma t ion (o r o f f se t ) a t u n l o a d i n g . A l l of t h e a fo remen t ioned t e c h n i q u e s appear t o be appl icable f o r asbestos cement materials, b u t t h i s i s n o t t h e case f o r mortar o r F R C .

(3)

3 07

1982

2024. Barr, B . , and K . Liu, "GENERAL BEHAVIOR OF POLYPROPYLENE FIBER CONCRETE," C o n c r e t e (London) , Vol. 16, N o . 4, A p r 1982, p p . 33-35.

T h i s paper p r e s e n t s a review o f t h e l i t e r a t u r e t h a t deals w i t h t h e s t u d i e s of t h e a d d i t i o n of f i b e r s i n t o cements, mortars and concretes, and describes t h e development of t h e f r a c t u r e t o u g h n e s s t e s t . The t es t w a s a modified cube subjected t o eccentric compressive loads and t h e r e s u l t s o b t a i n e d f o r t o u g h n e s s are r e p r o d u c i b l e w i t h l o w values o f c o e f f i c i e n t of v a r i a t i o n .

2025. Craig, R . J . , S . Mahadev,C. C . P a t e 1 , M . V i t e r i , and C . K e r t e s z , "BEHAVIOR OF JOINTS USING REINFORCED FIBROUS CONCRETE," Proceedings, F i b e r R e i n f o r c e d C o n c r e t e : I n t e r n a t i o n a l Symposium, SP-81, American C o n c r e t e I n s t i t u t e , S e p t 1982, pp. 125-167.

The t e s t i n g program cons is ted o f t e n beam column j o i n t s w i t h h a l f o f t h o s e j o i n t s c o n t a i n i n g 1 . 5 % by volume of steel hooked f i b e r s . The beam column j o i n t s w e r e c o n s t r u c t e d w i t h less hoops t h a n a c o n v e n t i o n a l seismic j o i n t would h a v e . R e s u l t s i n d i c a t e d t h e f o l l o w i n g a b o u t t h e f iber r e i n f o r c e d j o i n t s : [ l l be t te r bond and conf inement were o b t a i n e d , [ 2 ] s t i f f e r m e m b e r , [31 h i g h e r moment c a p a c i t y , [ 4 ] h i g h e r s h e a r s t r e n g t h , [51 h i g h e r d u c t i l i t y , [ 61 s i g n i f i c a n t improvement i n t h e e n e r g y d i s s i p a t i o n c a p a c i t y as compared t o p l a i n concrete j o i n t s .

2026. Godfrey, K . A . , "FIBER REINFORCED CONCRETE," C i v i l E n g i n e e r i n g ( N e w York) , V o l . 52, N o . 11, Nov 1982, pp. 44-50.

H y d r a u l i c a p p l i c a t i o n s of f i b e r r e i n f o r c e d c o n c r e t e i n s p i l l w a y c h a n n e l s , t u n n e l s t h r o u g h d a m s a n d t h e i r abu tmen t s , a n d s p i l l i n g b a s i n s , r e f r a c t o r y a p p l i c a t i o n s i n a i r f i e l d pavements , and b u i l d i n g a p p l i c a t i o n s o f f iber c o n c r e t e i n c u r t a i n w a l l p a n e l s are d i s c u s s e d .

3 08

2027 . Johnston, C . D . , "DEFINITION AND MEASUREMENT OF FLEXURAL TOUGHNESS PARAMETERS FOR FIBER REINFORCED CONCRETE," Cement, Concrete, and Aggregates, V o l . 4 , NO. 2, 1982 , pp. 53-60.

C u r r e n t and pas t approaches t o assessing and d e f i n i n g t h e f l exura l toughness of f i b e r re inforced concrete a r e reviewed, and d i f f i c u l t i e s associated w i t h them a r e discussed. Refinements needed t o insure cor rec t ana lys i s and i n t e r p r e t a t i o n of t he load-deflection re la t ionships i n evaluat ion of t h e f l e x u r a l toughness a re i d e n t i f i e d . A new sys tem f o r def ining toughness i s proposed. I t comprises a s e r i e s of ind ices based on mater ia l behavior up t o a spec i f i ed mult iples of t h e f i r s t - c rack de f l ec t ion . T h i s system seems t o be superior t o t h e one c u r r e n t l y advocated by t h e ACI Committee 544 based on t h e mater ia l behavior up t o a de f l ec t ion of 0 . 0 7 5 i n . I t i s recommended a s t h e bases of t h e standard tes t method t o evaluate toughness, and i d e n t i f y appropriate provis ions f o r inclusion i n t h e standard.

2 0 2 8 . Johnston, C . D . , "STEEL F I B E R REINFORCED AND P L A I N CONCRETE: FACTORS I N F L U E N C I N G FLEXURAL STRENGTH MEASUREMENT," Proceedings , Journal of t h e American C o n c r e t e I n s t i t u t e , V o l . 79, N o . 2, 1982, pp. 131-138.

T h e development of standards f o r t e s t i n g f i b e r re inforced concrete i s a c u r r e n t concern t o many involved w i t h t h e design and u s e of t h e ma te r i a l . Because of i t s increased use i n forms of construct ion where f l e x u r a l performance i s important, a standard f o r f l e x u r a l t e s t i n g of FRC i s urgently needed. The major f a c t o r s inf luencing f l exura l s t rength measurement a r e i d e n t i f i e d . These f a c t o r s include span, depth, width, and mode of loading. I t i s shown how these f a c t o r s can be accounted f o r by a s i n g l e parameter t h a t represents t h e volume of t h e mater ia l i n a def inable zone of probable mater ia l f a i l u r e . Analysis of t h e authors experimental data and comparable data from other resources shows the va r i a t ion of f l exura l s t r e n g t h w i t h t h i s volume parameter t o be s imi l a r f o r both f i b e r re inforced and p l a in concretes. A r e l a t ionsh ip i s developed which permits t h e f l exura l s t rength i n any t e s t i n g arrangement t o be predicted from t h e va lue obtained i n any other arrangement. The s t rength of 1 8 x 6 x 6 i n c h specimens tested under t h i r d p o i n t loading i s used a s a reference.

3 09

2029. Kobayashi , K . , and R . Cho, lgFLEXURAL CHARACTERISTICS OF STEEL FIBRE AND POLYETHYLENE FIBRE HYBRID REINFORCED CONCRETE," Composites, Vol. 13, N o . 2, A p r 1982, pp. 164-168.

The effect o f u s i n g steel and p o l y e t h y l e n e f i b e r s t o g e t h e r i n c o n c r e t e h a s been i n v e s t i g a t e d , i n p a r t i c u l a r w i t h r e g a r d t o t h e f l e x u r a l properties of t h e composite. The i n t e n t i o n was t o produce a material combining t h e best qua l i t i e s of s t e e l / c o n c r e t e a n d p o l y e t h y l e n e / c o n c r e t e so as t o i n c r e a s e t h e f i r s t c r a c k i n g s t r e n g t h and t o u g h n e s s . The r e s u l t s i n d i c a t e d t h a t t h e f i rs t c r a c k i n g s t r e n g t h o f t h e h y b r i d composite was t h e same as t h a t of s teel f iber c o n c r e t e . It i s conc luded t h a t concrete w i t h s u p e r i o r q u a l i t y can be obtained u s i n g d i s c o n t i n u o u s s teel a n d p o l y e t h y l e n e f ibers i n randomly or ien ted s ta tes i n c o n c r e t e . Wi th in a pract ical r a n g e , t h e maximum h y b r i d e f f e c t w a s o b t a i n e d b y combining 1% by volume o f s t ee l a n d 3% by volume of p o l y e t h y l e n e .

2030. Ohama, Y.,S. Kan, and M . Miyara, "FLEXURAL BEHAVIOR OF STEEL FIBER REINFORCED POLYMER-MODIFIED CONCRETE," T r a n s a c t i o n s o f t h e J a p a n e s e C o n c r e t e I n s t i t u t e , V o l . 4 , Dec 1982, p p . 147-152.

T h i s paper describes t h e f l e x u r a l b e h a v i o r of s teel f iber r e i n f o r c e d polymer-modif ied c o n c r e t e (SFRPCC) which i s made by adding polymer dispers ion t o c o n v e n t i o n a l s teel f i b e r r e i n f o r c e d c o n c r e t e . SFRPCC specimens w i t h s t y r e n e - b u t a d i e n e rubber (SBR) l a t e x w e r e prepared a n d tested under f l e x u r a l l o a d i n g . L o a d - d e f l e c t i o n cu rve , t oughness , and maximum f i b e r s t r a i n on t h e t e n s i o n side i n f l e x u r e were c o l l e c t e d . The f l e x u r a l s t r e n g t h of SFRPCC w i t h s teel f i b e r c o n t e n t o f 2 % by volume and a polymer-cement r a t i o of 20% was 2 . 5 times t h a t of o r d i n a r y cement concrete . O t h e r f l e x u r a l p r o p e r t i e s were a l so improved w i t h i n c r e a s i n g polymer-cement r a t i o a n d f ibe r c o n t e n t . E m p i r i c a l e q u a t i o n s f o r t h e p r e d i c t i o n o f SFRPCC are proposed.

310

2031. Swamy, R . N . , and A . H . Jojagha, "IMPACT RESISTANCE OF STEEL FIBER REINFORCED LIGHTWEIGHT CONCRETE," I n t e rna t iona l Journal of Cement Composites and Lightweight Concrete, V o l . 4 , No. 4, Nov 1982, pp. 209-220.

T h i s paper r epor t s on the appl ica t ion of a t e s t method t o determine t h e impact r e s i s t ance of s t r u c t u r a l l ightweight concrete re inforced w i t h s teel f ibers . I t i s shown t h a t t h e tes t can e f f e c t i v e l y assess t h e impact r e s i s t ance of p l a i n and f iber concrete, and t h a t it i s ab le t o measure t h e d i f fe rences due t o f i b e r s shape and fiber geometry. Resistance t o impact and o the r suddenly appl ied loads i s now recognized a s one of t h e s i g n i f i c a n t proper t ies of f iber re inforced cementitious mater ia l s . U n t i l r e c e n t l y , t h e r e has been no simple and p r a c t i c a l tes t method t o measure t h i s property of f i b e r re inforced concrete and t o evaluate t h e e f fec t iveness of d i f f e r e n t types of f ibers i n enhancing t h e impact res i s tance of f i b e r concrete . More r e c e n t l y , t h e A C I Committee 5 4 4 has developed such a method and t h e t es t is being considered f o r inclusion a s an ASTM standard.

2032. Swamy, R . N . , and A . H . Jojagha, "WORKABILITY OF STEEL FIBRE REINFORCED LIGHTWEIGHT AGGREGATE CONCRETE," I n t e rna t iona l Journal of Cement Composites and Lightweight Concrete, V o l . 4, N o . 2 , May 1982, pp. 103-109.

The flow c h a r a c t e r i s t i c s of s t e e l f i b e r re inforced concrete made w i t h aggregates from pulverized f u e l ash and n a t u r a l sand a re reported. Four d i f f e r e n t types of f i b e r s with varying geometry and aspect r a t i o were s tud ied . T h e matrix incorporated a water-reducing/ p l a s t i c i z i n g agent, and i n some cases, cement was p a r t i a l l y replaced by 30% by weight of PFA. The workabi l i ty was determined using t h e slump tes t , t h e VB t es t and t h e inverted cone tes t . I t i s shown t h a t t h e inver ted slump cone tes t is ab le t o d i f f e r e n t i a t e s a t i s f a c t o r i l y t h e d i f fe rences i n workabili ty due t o shape and aspect r a t i o of t he f i b e r s . The r e s u l t s a r e compared t o i d e n t i c a l mixes without f i b e r s .

31 1

2033. Swamy, R . N . , and S . A . Ali, "PUNCHING SHEAR BEHAVIOR OF REINFORCED SLAB-COLUMN CONNECTIONS MADE WITH STEEL FIBER CONCRETE," J o u r n a l of t h e American Concre t e I n s t i t u t e , V o l . 79, N o . 5, Sept-Oct 1982, pp. 392-406.

Punching shear f a i l u r e s o c c u r sudden ly and produce c a t a s t r o p h i c r e s u l t s . The effect of f iber r e i n f o r c e m e n t on t h e de fo rma t ion and s t r e n g t h characterist ics of punching shear f a i l u r e s are d i s c u s s e d . The f ibers w e r e u sed th roughou t t h e s lab o r i n t h e punching shear zone of t h e column head. Comparative tes ts w e r e carried o u t on c o n n e c t i o n s w i t h bent-up s teel bars. The r e s u l t s show t h a t fibers reduce de fo rma t ions a t a l l s t a g e s of l o a d i n g , i n c r e a s e u l t i m a t e punching shear loads, and produce d u c t i l e shear f a i l u r e s . S u b s t a n t i a l i n c r e a s e i n d u c t i l i t y and ene rgy a b s o r p t i o n can be o b t a i n e d by u s i n g f iber c o n c r e t e . Bent up bars were found t o be more effective t h a n f iber r e i n f o r c e m e n t b u t rather v e r y labor i n t e n s i v e .

312

2034. Hannant, D . J . , "FIBER REINFORCED CEMENTS," F a b r i c a t i o n of Composites (Handbook of Composi tes) , Amsterdam, Ne the r l ands , Vol . 4 , 1983, pp. 429-500.

Topics of t h i s a r t i c l e i n c l u d e materials, t e s t i n g t e c h n i q u e s , t h e o r e t i c a l p r i n c i p l e s , f a b r i c a t i o n of f i b e r r e i n f o r c e d c o n c r e t e , f a b r i c a t i o n t e c h n i q u e s f o r p r e c a s t a p p l i c a t i o n s o f f i b e r c o n c r e t e , f a b r i c a t i o n of sheet materials from cements and mortars, asbestos-cement , a l t e r n a t i v e s t o asbestos-cement , and glass f ibe r r e i n f o r c e d c o n c r e t e materials.

2035. Kobayashi, K . , "DEVELOPMENT OF FIBER REINFORCED CONCRETE I N JAPAN," I n t e r n a t i o n a l J o u r n a l of Cement Composites and Lightweight Concrete , Vol. 5, No. 1, Feb 1983, pp. 27-40.

T h i s pape r d e s c r i b e s t h e p r o g r e s s made t o date i n t h e use o f f i b e r r e i n f o r c e d c o n c r e t e i n Japan . The development and manufacture of f i b e r s f o r r e i n f o r c i n g c o n c r e t e , an o u t l i n e o f r e s e a r c h on t h e v a r i o u s c h a r a c t e r i s t i c s of s teel f i b e r r e i n f o r c e d c o n c r e t e c o n s t r u c t i o n t echn iques , and examples of t h e a p p l i c a t i o n and placement of f iber c o n c r e t e are reviewed. I t i s estimated t h a t t h e q u a n t i t y of s t e e l f i b e r s used i n Japan i n 1981 amounted t o approximate ly 3,000 t o n s , about 2,500 t o n s of which were made from carbon s t ee l . Th i s paper e x p l a i n s t h e r easons why p r a c t i c a l a p p l i c a t i o n s of f i b e r r e i n f o r c e d c o n c r e t e have p r o g r e s s e d i n such a manner i n Japan . One of t h e main r easons i s t h a t approximate ly 85% of Japan i s mountainous and it i s prone t o ea r thquakes . These g e o g r a p h i c a l c o n d i t i o n s indicate t h a t SFRC i s a well s u i t e d composite material due t o i t s h i g h energy a b s o r p t i o n c a p a b i l i t i e s as w e l l a s h igh toughness .

2036. Naaman, A . E . , and V . S . Gopalaratnam, "IMPACT PROPERTIES OF STEEL FIBRE REINFORCED CONCRETE I N BENDING, The I n t e r n a t i o n a l J o u r n a l of Cement Composites and Lightweight Concrete , Vol. 5, N o . 4 , Nov 1983, pp. 225-233.

Bending p r o p e r t i e s of s t ee l f i b e r r e i n f o r c e d c o n c r e t e are s t u d i e d under v a r i o u s s t r a i n rates of l o a d i n g . Three volume f r a c t i o n s , t h r e e f iber a s p e c t r a t i o s , two mor tar mixes, and f o u r s t r a i n ra tes were i n v e s t i g a t e d . Depending on t h e volume f r a c t i o n s of f ibers, energy a b s o r p t i o n under h i g h s t r a i n r a t e l o a d i n g w a s found t o be 3 times h i g h e r t h a n t h a t under

313

s t a t i c l o a d i n g c o n d i t i o n s . T e s t i n g was t e r m i n a t e d when t h e midspan d e f l e c t i o n reached 0 .5" .

2037. P a t t o n , M . E . , and W . L . Whi t taker , "EFFECTS OF FIBER CONTENT AND DAMAGING LOAD ON STEEL FIBER REINFORCED CONCRETE STIFFNESS, " Proceed ings , J o u r n a l of t h e American Concre t e I n s t i t u t e , V o l . 80, N o . 1, Jan-Feb 1983, pp. 13-16.

The s t i f f n e s s of steel f iber r e i n f o r c e d c o n c r e t e and i t s s e n s i t i v i t y t o t h e f iber c o n t e n t and damaging l o a d are i n v e s t i g a t e d . An e x p e r i m e n t a l program i s implemented t o measure Young's modulus of P l a i n and SFRC beam samples, and t h e n t o damage these samples i n a c o n t r o l l e d manner. S u c c e s s i v e damage and modulus measurements lead t o t h e c o r r e l a t i o n of damage w i t h d e g r a d a t i o n of Young's modulus of SFRC materials. R e l a t i o n s h i p s of t h e s t i f f n e s s of t h e undamaged SFRC v e r s u s f iber c o n t e n t a n d t h e d e g r a d a t i o n of SFRC s t i f f n e s s w i t h damaging load.

2038. V i s a l v a n i c h , K., and A . E . Naaman, "FRACTURE MODEL FOR FIBER REINFORCED CONCRETE,1r J o u r n a l of t h e American C o n c r e t e I n s t i t u t e , V o l . 80, N o . 2, M a r - A p r 1983, pp. 128-138.

A f r a c t u r e model i s deve loped t o g e n e r a t e t h e complete growth r e s i s t a n c e cu rve , R c u r v e , f o r f i be r r e i n f o r c e d mortar, p l a i n c o n c r e t e , and asbestos cements . The crack growth mechanism i n these materials i s described i n terms of three d i f f e r e n t zones : stress-free, p s e u d o - p l a s t i c , and t h e process zone . T h e c o h e s i v e fo rce -d i sp lacemen t l a w , found t o be d i r e c t l y a f u n c t i o n of t h e r e i n f o r c i n g index and t h e bond properties of t h e f ibers, as w e l l as t h e crack shape were needed t o g e n e r a t e t he e n t i r e R-curve and t h e c r i t i ca l f r a c t u r e e n e r g y . A s u f f i c i e n t l y large number of spec imens were used f o r t h e computa t ion of t h e f r a c t u r e t o u g h n e s s of FRC mortar t o allow t h e p r o c e s s zone t o d e v e l o p .

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1984

2039. Akihama, S.,T. Suenaga, and T. Banno, "THE BEHAVIOR OF CARBON FIBER REINFORCED CEMENT COMPOSITES IN DIRECT TENSION," International Journal of Cement Composites and Lightweight Concrete, Vol. 6, No. 3, Aug 1984, pp. 159-168.

A low modulus carbon fiber made from pitch of petroleum was recently developed in Japan. This fiber has many advantages as a cement reinforcing fiber in terms of cost, mechanical properties and alkali resistance. A high performance fiber reinforced composite using carbon fibers is developed for various applications in building structures. The tensile strength characteristics are reported. It is shown that when 3% to 5% by volume of carbon fibers is added to the cement matrix, a ductile and tough new composite material with 80 to 140 kg per cm square tensile stress and 0 . 0 1 1 tensile strain capability is obtained.

2040 Anderson, W. F.,A. J. Watson, and P. J. Armstrong, "FIBER REINFORCED CONCRETE FOR THE PROTECTION OF STRUCTURES AGAINST HIGH VELOCITY IMPACT," Proceedings, Structural Impact and Crashworthiness, London, Vol. 2, July 1984, pp. 687-695.

This paper discusses the use of fiber-reinforced concrete materials to resist projectile impact. Target damage was quantified and correlated to the fiber concrete parameters. Instrumentation and high speed photography were used to investigate the failure mechanisms. In this project, the resistance of FRC for spray applications have been examined. Specimens 0 . 7 inA2 and various thicknesses have been prepared w i t h different mix proportions, cured and then impacted centrally with a 0.3 inch diameter copper-sheathed hardened steel projectile travelling at an approximately 2625 ft/s. It is concluded that the front face spalling can be controlled by incorporating increasing amounts of fibers within the concrete matrix, and in order to improve the design of materials which provide protection against projectile impact, it is desirable to have at least an empirical understanding of the impact and penetration mechanism.

315

2041. Batson, G . , T . T e r r y , and M. Chang, "FIBER REINFORCED CONCRETE BEAMS SUBJECTED TO COMBINED BENDING AND TORSION, If Proceed ings , F i b e r Reinforced Concre t e - I n t e r n a t i o n a l Symposium, A C I S p e c i a l P u b l i c a t i o n SP 81-3, American C o n c r e t e I n s t i t u t e , Det ro i t , 1984, p p . 51-68.

T e s t data u s i n g steel f ibers as t o r s i o n a l s h e a r r e i n f o r c e m e n t f o r 3 6 r e i n f o r c e d c o n c r e t e beams subjected t o combined bending and to r s ion were presented. Beams were loaded i n bending a t t h i r d p o i n t s and by t h i r d p o i n t t o r s i o n a l loading. S t r a i g h t s teel fibers o f 1" l o n g by 0.010 x 0.022 i n . i n cross s e c t i o n were u s e d . C o n t e n t s used were 0, 0 .5 , 1 . 0 , a n d 1 . 5 % by volume o f c o n c r e t e . T e s t data were compared t o a t h e o r y developed by M a r t i n fo r concrete beams reinforced w i t h l o n g i t u d i n a l s t ee l o n l y ( w i t h no closed s t i r r u p s ) and subjected t o bend ing and t o r s i o n . B e a m s w i t h 1% by volume of s t r a i g h t s teel f ibers i n combina t ion w i t h l o n g i t u d i n a l t o r s i o n a l r e i n f o r c e m e n t were e f f e c t i v e i n r e s i s t i n g t o r s i o n f o r a moment-to-torque r a t i o less than 2 . Moment-to-torque ra t ios greater t h a n 1 0 and c o n t a i n i n g 0 . 5 % f i b e r s were s u f f i c i e n t t o resist t o r s i o n a l stresses.

2042. Bonzel , J . , and M . Schmidt, "DISTRIBUTION AND ORIENTATION OF STEEL FIBERS I N CONCRETE AND T H E I R INFLUENCE ON THE QUALITY OF STEEL FIBER CONCRETE [VERTEILUNG UND ORIENTIERUNG VON STAHLFASERN I M BETON

UND EINFLUSS AUF D I E EIGENSCHAFTEN VON STAHLFASERBETON]," Beton, H e r s t e l l u n g , Verwendung, V o l . 3 4 , NO. 11, NOV 1984, pp. 463-470.

The compressive b e h a v i o r o f c o n c r e t e when it i s stressed by repeated loads can be improved by t h e a d d i t i o n of a t least 2% s t ee l f ibers by volume. P r e v i o u s i n v e s t i g a t i o n s revealed t h a t t h e a d d i t i o n of s teel f i b e r s was n o t a lways proport ional n o r were t h e fibers a lways o r i e n t e d randomly. T e s t r e s u l t s showed t h a t s teel f ibe r s w e r e ma in ly o r i e n t e d v e r t i c a l l y t o t h e d i r e c t i o n o f p r o d u c t i o n and c o n c r e t i n g when v a r i o u s s i z e d tes t spec imens w e r e tested. A ve r t i ca l t a b l e v ib ra to r w a s u s e d and u s u a l c o n c r e t i n g methods were employed.

31 6

2043. Brandt, A . M . , "ON THE OPTIMIZATION OF THE F I B E R ORIENTATION I N CEMENT-BASED COMPOSITE MATERIALS," Proceedings, Fiber Reinforced Concrete- In t e rna t iona l Symposium, A C I Special Publication SP 81-13, American Concrete I n s t i t u t e , Det ro i t , 1984, pp. 267-285.

Cracked concrete-l ike composites composed of b r i t t l e cement-based matrices and t h i n chopped s teel and g l a s s f i b e r s with a volume content l e s s than 3% a r e considered. These cracks might be admissible provided t h a t t h e s t r u c t u r e can sus t a in i t s own weight and other permanent ac t ions . Composites which possesses these p rope r t i e s may be co r rec t ly evaluated. T h i s can be done by tak ing i n t o account t h e i r a b i l i t y t o absorb t h e work of ex te rna l loads. The amount of t h i s work was chosen a s t h e objec t ive function and was ca lcu la ted considering i t s f i v e d i f f e r e n t components. Simplif ied r e l a t ionsh ips a r e derived from t h e assumed behavior of t h e f i b e r s i n t h e cracked matrix. I n t h i s inves t iga t ion , t h e angle of o r i en ta t ion of t h e p a r a l l e l f i b e r sys t em was considered a s t h e only design va r i ab le . The so lu t ion was obtained f o r an element subjected t o a x i a l tension using t h e necessary condi t ions f o r obtaining the maximum f r a c t u r e energy. The optimum or i en ta t ion angle of t h e f i b e r s w i t h respect t o the loading d i r ec t ion was determined. The angle was found t o vary between 18 and 40 degrees. The proposed method can be applied t o f u r t h e r appl ica t ions involving more complicated optimization problems.

2 0 4 4 . Craig, R . J . , "STRUCTURAL APPLICATIONS OF REINFORCED FIBROUS CONCRETE," Concrete In t e rna t iona l : Design & Construction, V o l . 6, No. 1 2 , Dec 1 9 8 4 , pp. 28-32.

The use of f i b e r re inforced concrete i s gaining increasing importance i n the bui lding mater ia l s a r e a . Hydraulic cements used i n bui lding mater ia l s a r e weak i n t ens ion , b u t w i t h t h e addi t ion of s u i t a b l e amount of f i b e r s , t h i s d i f f i c u l t y can be overcome. T h i s a r t i c l e d i scusses the bene f i t s of using t h i s mater ia l i n f lexure , shear, to rs ion , and columns. Applications and problems encountered during construct ion a r e discussed. Research needs a r e pointed ou t . The codes should be looked a t t o i n s u r e t h a t proper methods a r e employed and t h a t b e n e f i t s of f i b e r s a re f u l l y u t i l i z e d . The use of s t e e l f i b e r s i n s t r u c t u r a l appl ica t ions has come a long way i n t h e past decade but more research i s needed. t h e u s e of t he f i b e r s i n combination w i t h r e inforc ing bars should give t h e optimum choice t o t h e designer .

317

2045. Craig, R . J . , J . McConnel1,H. Germann,N. D i b , a n d F . Kashani , "BEHAVIOR OF REINFORCED FIBROUS CONCRETE COLUMNS," P roceed ings , Fiber R e i n f o r c e d Concre t e - I n t e r n a t i o n a l Symposium, A C I S p e c i a l P u b l i c a t i o n SP 8 1 - 4 , American C o n c r e t e I n s t i t u t e , Det ro i t , 1984, pp. 69-105.

A t o t a l of 3 6 r e i n f o r c e d f i b r o u s c o n c r e t e columns were tested t o s t u d y t h e i r behavior u n d e r p u r e a x i a l compress ion and c o m p r e s s i o n + b i a x i a l bend ing . T h e r e s u l t of t h i s e x p e r i m e n t a l program i s a t h e o r y which i n c o r p o r a t e s load-moment i n t e r a c t i o n diagrams. T h e theory proposed i s a m o d i f i c a t i o n of p r e v i o u s i n v e s t i g a t i o n r e s u l t s and e q u a t i o n s u s e d f o r r e i n f o r c e d a n d p l a n e c o n c r e t e . These m o d i f i c a t i o n s were i n t r o d u c e d t o ref lect t h e p r e s e n c e of f ibers i n t h e r e i n f o r c e d c o n c r e t e columns. T h e f i r s t series of these tes ts c o n s i s t e d of f i f t e e n 6 x 4 . 7 5 i n c h columns tested i n p u r e a x i a l compress ion . The columns c o n t a i n e d s t ee l f ibers h a v i n g volume f r a c t i o n s on t h e order of 0 % , 0 .75%, a n d 1 . 5 % . The t i e s p a c i n g of these columns r anged from 3 t o 9 i n c h e s . The second series c o n s i s t e d of t e s t i n g 2 1 unde r combined a x i a l load and b i a x i a l b e n d i n g .

2046. Craig, R . J . , S . Dunya,J. R iaz , a n d H . S h i r a z i , "TORSIONAL BEHAVIOUR OF REINFORCED FIBROUS CONCRETE BEAMS, 'I P r o c e e d i n g s , Fiber R e i n f o r c e d Concre t e - I n t e r n a t i o n a l Symposium, A C I Special P u b l i c a t i o n SP 81-2, American C o n c r e t e I n s t i t u t e , Det ro i t , 1984, pp. 17-49.

The object ive o f t h i s s t u d y w a s t o examine t h e t o r s i o n a l behavior of r e i n f o r c e d c o n c r e t e f i b r o u s beams u n d e r p u r e t o r s i o n and t o develop a theore t ica l approach t o a n a l y z e these beams. The behavior of f i b e r r e i n f o r c e d c o n c r e t e beams i n t o r s i o n was observed a n d a r ea l i s t i c method t o a n a l y z e s u c h beams when t h e y a re s u b j e c t e d t o t o r s i o n was presented. Nine beams were a n a l y z e d a n d e x p e r i m e n t a l l y tes ted. Two beams c o n t a i n e d no f ibers a n d s e v e n c o n t a i n e d d i f f e r e n t amount of f ibers . Two d i f f e r e n t t y p e s of f ibers were u s e d . A l l beams had t h e same l o n g i t u d i n a l bars b u t t h e hoop s p a c i n g var ied .

318

2047. G l i n i c k i , M. A . , "INVESTIGATION OF PROPERTIES OF FIBROUS CONCRETE MADE WITH STEEL FIBERS O R I G I N A T I N G FROM INDUSTRIAL STEEL SCRAPS [BADANIE WLASCIWOSCI FIBROBETONU Z SLOKNAMI STALOWYMI Z ODPADOW PRZEMYSLOWYCH] , I n z y n i e r i a i Budownictwo, V o l . 4 1 , No. 4 , A p r 1984, pp . 139-142.

R e s u l t s are presented for tes ts carried o u t on f i b e r concrete elements w i t h steel f ibers o r i g i n a t i n g from i n d u s t r i a l s teel scraps and w i t h Thibo s tee l f i b e r s . A f t e r e v a l u a t i n g t h e costs o f s teel f i b e r s a n d t h e mechan ica l propert ies of t h e obtained f ibrous c o n c r e t e , t h e a u t h o r s t a t e t h a t t h e a p p l i c a t i o n o f i n d u s t r i a l s teel scraps as s tee l fibers i s t e c h n i c a l l y a n d e c o n o m i c a l l y f e a s i b l e .

2048. Hasaba, S.,M. Kawamura,T. Koizumi, and K . Takemoto, "RESISTIBILITY AGAINST IMPACT LOAD AND DEFORMATION CHARACTERISTICS UNDER BENDING LOAD I N POLYMER AND HYBRID (POLYMER AND STEEL) FIBER REINFORCED CONCRETE, I'

P r o c e e d i n g s , F i b e r Reinforced Concre te - I n t e r n a t i o n a l Symposium, A C I S p e c i a l P u b l i c a t i o n SP 81-8, American C o n c r e t e I n s t i t u t e , Det ro i t , 1984, pp . 187-196.

T h i s paper reports a few re su l t s of t h e e x p e r i m e n t s carried o u t t o i n v e s t i g a t e t h e c h a r a c t e r i s t i c s o f d e f l e c t i o n of t h e polymer f i b e r a n d h y b r i d f i b e r r e i n f o r c e d c o n c r e t e beams under bend ing load. Some r e s u l t s on t h e dynamic s t r e n g t h t e s t of t h e polymer and h y b r i d f iber r e i n f o r c e d concrete beams by a Charpy impact tester m o d i f i e d for concrete specimens was a l s o discussed i n t h i s p a p e r . The polymer f ibers used i n polymer f i b e r r e i n f o r c e d concrete were f i l a m e n t s w i t h e x t r e m e l y small diameter. The s t ee l f i b e r s used i n t h i s i n v e s t i g a t i o n were r e l a t i v e l y t h i c k w i t h a r e c t a n g u l a r cross s e c t i o n o f 0 .079 x 0.024 i n c h e s . The f l e x u r a l s t r e n g t h of c o n c r e t e was improved by t h e a d d i t i o n of t h e polymer f ibers , and t h e polymer f i b e r r e i n f o r c e d c o n c r e t e beams showed more endurance a f t e r t h e i n i t i a t i o n of c r a c k s i n t h e spec imens . A method by a modified Charpy impact t es te r was p roposed i n t h i s s t u d y f o r e v a l u a t i n g t h e resistance of c o n c r e t e a g a i n s t impact loading. According t o t h e r e s u l t s o b t a i n e d using t h i s method, t h e r e s i s t i b i l i t y o f t h e polymer and h y b r i d f i b e r r e i n f o r c e d c o n c r e t e a g a i n s t impact l o a d i s a b o u t d o u b l e t h a t f o r p l a i n c o n c r e t e .

319

2049. Ibukiyama, S . , K . Seto, and S . Kokubu, "STEEL FIBER-REINFORCED CONCRETE OVERLAYS ON ASPHALT PAVEMENTS," P roceed ings , F i b e r R e i n f o r c e d Concre t e - I n t e r n a t i o n a l Symposium, A C I S p e c i a l P u b l i c a t i o n SP 81-17, American Concre t e I n s t i t u t e , Det ro i t , 1984, p p . 351-373.

Exper iments c o n c e r n i n g t h e b e a r i n g c a p a c i t i e s of t h i n s teel f i b e r r e i n f o r c e d c o n c r e t e (SFRC) slabs, which are m o s t i m p o r t a n t i n u s i n g SFRC for o v e r l a y s on a s p h a l t pavements , are r e p o r t e d , and i n s t a l l a t i o n o p e r a t i o n s and s e r v i c e a b i l i t i e s o f a c t u a l overlays are described. According t o l o a d i n g tests, SFRC slabs w i t h c r u s h e d r o c k and a s p h a l t - c o n c r e t e bases possess b e a r i n g capacities o f abou t 1 7 t o 22 t o n s . These s labs are t h o u g h t t o amply s u p p o r t of a c t u a l t r a f f i c loads. Consequent ly , it i s c o n s i d e r e d t h a t t h e u s e of SFRC which i s immune t o r u t t i n g and d i s t o r t i o n would p r o v i d e e x c e l l e n t r e s u r f a c i n g , smooth and d u r a b l e . I t i s f u r t h e r shown t h a t t h e y i e l d l i n e t h e o r y can be a p p l i e d t o d e s i g n o f r e s u r f a c i n g u s i n g SFRC. The u s e of s t ee l f ibers i s proved t o be v e r y e f f i c i e n t unde r severe c o n d i t i o n s . I n t h i s case, damage can be s u s t a i n e d and t h e c r a c k f o r m a t i o n can be improved. Much r e f e r e n c e mater ia l w a s o b t a i n e d r e g a r d i n g t h e t h i c k n e s s e s of t h e SFRC o v e r l a y s , j o i n t s p a c i n g s , and r e i n f o r c e m e n t of c o r n e r port i o n s .

2050. J i n d a l , R . L . , "SHEAR AND MOMENT CAPACITIES OF STEEL FIBER REINFORCED CONCRETE BEAMS," P roceed ings , F iber R e i n f o r c e d Concre te - I n t e r n a t i o n a l Symposium, A C I S p e c i a l P u b l i c a t i o n SP 81-1, American C o n c r e t e I n s t i t u t e , D e t r o i t , S e p t 1984, pp . 1-16 .

T e s t s were conduc ted on 4 4 beams t o s t u d y t h e e f f e c t s of s teel f i b e r s as s h e a r r e i n f o r c e m e n t and t o d e t e r m i n e i f t h e r e was any i n c r e a s e i n t h e shear/moment c a p a c i t y and change i n t h e mode o f f a i l u r e . Span l e n g t h s o f 30 and 60 i n c h e s were used f o r a s h e a r - s p a n r a t i o s a / d o f 2, 2 . 4 , 3 . 6 and 4 .8 , r e s p e c t i v e l y . S t e e l f i b e r s w i t h a 1% volume f r a c t i o n were u s e d i n a l l beams. T h e variables were t h e t y p e of f i b e r s , aspect r a t i o ( l / d ) o f t h e f ibers, and t h e s h e a r span r a t i o . T e s t r e s u l t s showed t h a t t h e s h e a r and moment c a p a c i t i e s o f SFRC beams v a r i e d f r o m 1 . 5 t o 1 . 9 2 a n d 1 . 1 2 t o 1 . 3 9 t i m e s t h o s e o f c o n v e n t i o n a l r e i n f o r c e d c o n c r e t e beams, r e s p e c t i v e l y . When SFRC w a s u sed , t h e mode of f a i l u r e changed from s h e a r mode t o f l e x u r a l mode. The s h e a r c a p a c i t y was i n c r e a s e d when f i b e r s h a v i n g a n aspect r a t i o o f 7 5 were u s e d . A d e s i g n method i s s u g g e s t e d f o r a n a l y z i n g and d e s i g n i n g SFRC beams. T h e o r e t i c a l r e s u l t s were i n good agreement w i t h e x p e r i m e n t a l r e s u l t s .

320

2051. J i n d a l , R . L . , and K . A . Hassan, "BEHAVIOUR OF STEEL FIBER REINFORCED CONCRETE BEAM-COLUMN CONNECTIONS," Proceedings , F i b e r Reinforced Concrete- I n t e r n a t i o n a l Symposium, A C I S p e c i a l P u b l i c a t i o n SP 81-5, Amer ican Concre te I n s t i t u t e , D e t r o i t , 1984, pp. 107-113.

S i x two-span cont inuous t y p e beam-column specimens of span 5 ' 7" each t e s t e d t o f a i l u r e . The beam c r o s s s e c t i o n w a s 6 x 1 0 inches and t h e column c r o s s s e c t i o n was 6 x 6 i n c h e s . The beam s e c t i o n c o n t a i n e d two bars each 1 / 2 i n c h i n diameter. Two t e s t specimens (Type A ) were of r e i n f o r c e d c o n c r e t e having s t i r r u p s as s h e a r r e in fo rcemen t . Another two specimens (Type B ) c o n t a i n i n g s t ee l f i b e r s of l e n g t h l", d iame te r = 0.01", and a 2% volume c o n t e n t of f i b e r s were tes ted. Type C specimens c o n t a i n e d SFR i n t h e connec t ion r e g i o n o n l y . An a x i a l compressive l o a d of 40 k i p s w a s a p p l i e d t o t h e column s e c t i o n . Ver t i ca l l oads were a p p l i e d t o each of t h e beams a t a d i s t a n c e equa l t o 4 6 . 3 i n c h e s from each end. T e s t r e s u l t s showed an i n c r e a s e of 20% and 1 0 % i n s h e a r and moment c a p a c i t i e s , r e s p e c t i v e l y , o f SFRC connec t ions over t h e RC connec t ions . SFRC connec t ions fa i led i n a d u c t i l e mode. SFRC w a s found t o be ve ry e f f e c t i v e i n t h e connec t ion r eg ion i n t h e specimens tes ted f o r l o w cycle f a t i g u e .

2052. Johnston, C . D . , "MEASURES OF THE WORKABILITY OF STEEL F I B E R REINFORCED CONCRETE AND THEIR PRECISION, 'I Cement, Concre te , and Aggregate, Vol. 6, No. 2 , 1984, pp . 74-83.

Measurements of t h e w o r k a b i l i t y of f r e s h l y mixed s teel f i b e r r e i n f o r c e d c o n c r e t e have been conducted u s i n g t h e t r a d i t i o n a l slump t e s t , t h e B r i t i s h S tanda rd V-B t es t and t h e t e s t u s i n g t h e t i m e f low through an i n v e r t e d slump cone r e c e n t l y i s s u e d by ASTM ( C 9 9 5 ) . D i f f e r e n c e s between t h e t e s t s i n terms of t h e e x t e n t t h e y assess t h e s t a b i l i t y , m o b i l i t y , and c o m p a c t i b i l i t y of f r e s h c o n c r e t e are i d e n t i f i e d , and t h e r e l a t i o n s h i p between t h e r e s u l t s o f each t y p e of t e s t are d iscussed i n t h i s c o n t e x t . The s i n g l e - o p e r a t o r , d e f i n e d as an o p e r a t o r t h a t i s conduct ing a s i n g l e t es t , and between-operator p r e c i s i o n , d e f i n e d as t h e p r e c i s i o n between t h e o p e r a t o r s , o f each t y p e of t e s t are examined u s i n g f o u r o p e r a t o r s r e p e a t i n g each t e s t f o u r d i f f e r e n t times on a t o t a l of 18 d i f f e r e n t mix tu res wi th a g g r e g a t e maximum s i z e , f i b e r c o n t e n t , and f i b e r a s p e c t r a t i o as t h e v a r i a b l e s . P r e c i s i o n is ana lyzed i n t e r m s of b o t h s t a n d a r d d e v i a t i o n and t h e c o e f f i c i e n t of v a r i a t i o n , and t h e dependance of each measure of p r e c i s i o n on t h e magnitude of t h e mean i s examined i n t e r m s of t h e c o r r e l a t i o n c o e f f i c i e n t s .

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2053. Johns ton , C . D . , "STEEL FIBER REINFORCED PAVEMENT TRIALS," Concre te I n t e r n a t i o n a l : Design and C o n s t r u c t i o n , Vol. 6, N o . 12, Dec 1984, pp. 39-43.

Three p r o j e c t s i n v o l v i n g steel f i b e r r e i n f o r c e d pavements s u b j e c t e d t o c i t y bus t r a f f i c are d e s c r i b e d . These p r o j e c t s have provided b o t h t h e ready-mixed c o n c r e t e producer and s t reet d e s i g n e r w i t h e x p e r i e n c e i n b a t c h i n g , mixing, p l a c i n g , and f i n i s h i n g FRC u s i n g a v a r i e t y of s teel f i b e r s . For pavements exposed t o heavy t r a f f i c l o a d i n g s , p a r t i c u l a r l y buss r o u t e s , performance i s promising, b u t acceptance of t h e mater ia l on a l a r g e scale w i l l depend on t h e costs invo lved b o t h i n p u r c h a s i n g and i n subsequen t ly h a n d l i n g and mixing t h e f ibers p r o p e r l y wi th t h e c o n c r e t e m a t r i x u s i n g c o n v e n t i o n a l equipment. Two p r o j e c t s were c o n s t r u c t e d i n 1973 and 1976 and were of f u l l dep th f i b r o u s c o n c r e t e r ang ing from 3 t o 6 i n c h e s w i t h c o n t r o l u n r e i n f o r c e d p l a i n c o n c r e t e s l a b s up t o 8 i n c h e s . The t h i r d , p l a c e d i n 1977, i s o f composi te c o n s t r u c t i o n w i t h f i b r o u s c o n c r e t e over l e a n ( e c o n c r e t e ) c o n c r e t e . P roduc t ion and placement t e c h n i q u e s and crack data are reviewed.

2054. K e e r , J . G., and A . Thorne, "PERFORMANCE OF POLYPROPYLENE-REINFORCED CEMENT SHEETING ELEMENTS," Proceedings, Fiber Reinforced Concrete- International Symposium, A C I S p e c i a l P u b l i c a t i o n SP 81-10, American Concre te I n s t i t u t e , D e t r o i t , 1984, pp. 213-231.

A po lypropy lene - re in fo rced cement composi te h a s been developed which i s cons ide red t o be an economic a l t e r n a t i v e t o asbestos cement. A major a p p l i c a t i o n of t h e composi te w i l l be c o r r u g a t e d s h e e t s f o r r o o f i n g and c l a d d i n g . Comparative tes ts on t h e behav io r f u l l - s i z e po lyp ropy lene - re in fo rced cement c o r r u g a t e d sheets and asbestos-cement s h e e t s under s i m u l a t e d un i fo rmly d i s t r i b u t e d l o a d s w e r e r e p o r t e d . R e s u l t s i n d i c a t e t h a t new s h e e t i n g of s imilar p r o f i l e can s u s t a i n t h e l o a d s r e q u i r e d i n I n t e r n a t i o n a l S t anda rds recommendations and remain serviceable. The q u a s i - d u c t i l e b e h a v i o r of t h e s h e e t i n g and e x c e l l e n t impact r e s i s t a n c e are c o n s i d e r a b l e advantages ove r t h e b r i t t l e behav io r of a s b e s t o s cement.

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2055. Kukreja , C . B. ,S. K . Kaushik,M. B . Kanchi, and 0. P . J a i n , "SHEAR CHARACTERISTICS OF REINFORCED F I B E R CONCRETE," I n s t i t u t e o f Engineers of I n d i a P a r t C 1 2 , Vol. 65, Sept 1984, pp. 89-95.

F ib rous c o n c r e t e i s a composi te material of c o n c r e t e m a t r i x w i t h even ly d i s t r i b u t e d closely spaced s t ee l f ibers . Add i t ion of small amount of c l o s e l y d i s t r i b u t e d discrete s teel f i b e r s t o c o n c r e t e improves i t s s t a t i c p r o p e r t i e s such as t e n s i l e , s h e a r and f l e x u r a l s t r e n g t h . An i n v e s t i g a t i o n under taken a t t h e U n i v e r s i t y of Roorkee t o o b t a i n in fo rma t ion on shear characteristics of r e i n f o r c e d f iber c o n c r e t e gave a maximum i n c r e a s e of 66% i n t h e shear s t r e n g t h as compared t o r e i n f o r c e d c o n c r e t e . The u l t i m a t e f a i l u r e l o a d a l so i n c r e a s e d by 66% by t h e a d d i t i o n of f i be r s of l / d r a t i o e q u a l t o 80.

2056. Lankard, D . R . , "PROPERTIES, APPLICATIONS: SLURRY INFILTRATED FIBER CONCRETE (SIFCON)," Concre te I n t e r n a t i o n a l : Design C Cons t ruc t ion , Vol . 6, No. 1 2 , D e c 1984, pp. 4 4 - 4 7 .

S t e e l f iber r e i n f o r c e d c o n c r e t e (SFRC) are t y p i c a l l y p r e p a r e d by adding the f ibers a l o n g t h e o t h e r c o n c r e t e i n g r e d i e n t s i n t h e mixing o p e r a t i o n . Using t h i s premix approach, it i s p o s s i b l e t o i n c o r p o r a t e up t o about 2 6 5 pcy (2% by volume) of f iber i n t o t h e c o n c r e t e . A t f i b e r c o n t e n t s i n excess of 2 % , t h e SFRC becomes d i f f i c u l t if n o t imposs ib l e t o mix and p l a c e . Inasmuch as t h e improvements i n c o n c r e t e p r o p e r t i e s a t t r i b u t e d t o f ibers i n c r e a s e as a f u n c t i o n of i n c r e a s i n g f i b e r c o n t e n t , t h i s s i t u a t i o n p l a c e s a l i m i t on t h e u l t i m a t e p r o p e r t y developed i n SFRC p r e p a r e d by t h e premix approach . Recent ly , a procedure has been developed wherein s t ee l f i b e r c o n t e n t s up t o 18% by volume have been p rov ided i n SFRC composi tes . The e n g i n e e r i n g p r o p e r t i e s of these h i g h l y r e i n f o r c e d composi tes (referred t o as S l u r r y I n f i l t r a t e d F i b e r C O N c r e t e o r SIFCON) are d i s c u s s e d a long w i t h a number of s u c c e s s f u l a p p l i c a t i o n s . S I F C O N c o n t a i n i n g p o r t l a n d cement and ca lc ium a lumina te cement-based p a s t e s and mor t a r s have e x h i b i t e d e n g i n e e r i n g p r o p e r t i e s w e l l beyond t h e range normal ly e x h i b i t e d by conven t iona l p o r t l a n d cement c o n c r e t e and SFRC material. I n a d d i t i o n t o having compressive s t r e n g t h s i n t h e 15 t o 30 k s i range and f l e x u r a l s t r e n g t h s i n the 5 t o 10 k s i range , S I F C O N materials have demonstrated o u t s t a n d i n g d u c t i l i t y and a b i l i t y t o resist c r a c k i n g and s p a l l i n g .

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2057. Lankard, D . R . , I1SLURRY INFILTRATED FIBER CONCRETE (SIFCON): PROPERTIES AND APPLICATIONS," P r o c e e d i n g s , Materials Resea rch S o c i e t y Symposia, V o l . 42, Nov 1 9 8 4 , pp. 277-286.

S t e e l f i b e r r e i n f o r c e d c o n c r e t e , SFRC, i s t y p i c a l l y prepared be a d d i n g t h e f iber a l o n g w i t h t h e o t h e r concrete i n g r e d i e n t s i n t h e mix ing o p e r a t i o n . When t h e f iber c o n t e n t exceeds 2 % by volume, t h e SFRC becomes d i f f i c u l t or even impossible t o mix and place. Inasmuch as improvements i n c o n c r e t e propert ies a t t r i b u t e d t o t h e f i b e r s i n c r e a s e as a f u n c t i o n o f i n c r e a s i n g t h e f i be r c o n t e n t , t h i s s i t u a t i o n places a l i m i t on t h e development of SFRC mortars. R e c e n t l y , a p r o c e d u r e h a s been h a s been developed where s teel volume c o n t e n t s up t o 20% have been provided. S l u r r y i n f i l t r a t e d f i b e r concrete (SIFCON) composites possess o u t s t a n d i n g s t r e n g t h , d u c t i l i t y , a n d c rack - spa11 r e s i s t a n c e .

2058. Lankard, D . R . , and J. K . N e w e l l , "PREPARATION OF H I G H L Y REINFORCED STEEL FIBER REINFORCED CONCRETE COMPOSITES," P r o c e e d i n g s , F i b e r R e i n f o r c e d Concre t e - I n t e r n a t i o n a l Symposium, ACI S p e c i a l P u b l i c a t i o n SP 81-14, American C o n c r e t e I n s t i t u t e , Det ro i t , 1 9 8 4 , pp. 287-306.

S t e e l f iber r e i n f o r c e d c o n c r e t e i s t y p i c a l l y prepared b y a d d i n g t h e f ibers a l o n g w i t h t h e o t h e r c o n c r e t e i n g r e d i e n t s i n t h e mixing o p e r a t i o n . Using t h i s premix approach , it i s possible t o i n c o r p o r a t e up t o 265 l b / y d 3 ( 2 % by volume) of f i b e r s i n t o t h e concrete. A t f i b e r conten ts greater t h a n 2%, SFRC becomes d i f f i c u l t t o mix i f n o t impossible. I n as much as t h e improvements i n t h e p r o p e r t i e s o f c o n c r e t e a t t r i b u t e d t o t h e f ibers i n c r e a s e as a f u n c t i o n of t h e f iber c o n t e n t , t h i s s i t u a t i o n places a l i m i t on t h e u l t i m a t e p r o p e r t y development i n SFRC prepared u s i n g t h e premix approach . R e c e n t l y , a p r o c e d u r e h a s been developed where in s teel f i b e r c o n t e n t s up t o 18% by volume have been p r o v i d e d i n SFRC c o m p o s i t e s . T h i s new mix i s known as S l u r r y I n f i l t r a t e d F i b e r C o n c r e t e , SIFCON. The e n g i n e e r i n g p r o p e r t i e s of t h e s e h i g h l y r e i n f o r c e d composites are discussed a l o n g w i t h a number of s u c c e s s f u l a p p l i c a t i o n s .

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2059 . Mansur, M . A . , and W . A . A l w i s , "REINFORCED F I B E R CONCRETE DEEP BEAMS WITH WEB O P E N I N G S , " I n t e rna t iona l Journal of Cement Composites and Lightweight Concrete, Vol. 6, N O . 4 , NOV 1 9 8 4 , pp. 263-271.

The r e s u l t s of 1 2 re inforced f i b e r concrete deep beams w i t h rectangular openings i n t h e web a r e reported. The beam dimensions and the s i z e of t h e openings were kept constant . The major parameters of t h e study were t h e volume f r a c t i o n of f i b e r s , opening loca t ion , shear span t o e f f e c t i v e depth r a t i o and t h e amount of web reinforcement. Test resu l t s i nd ica t e t h a t t h e amount of web reinforcement, e i ther i n t h e form of d i s c r e t e f i b e r s or a s continues reinforcement, and the loca t ion of t h e opening, were t h e p r inc ip l e parameters t h a t a f f e c t t he behavior and s t rength of deep beams. Available s t rength equations f o r p l a in concrete deep beams were shown t o provide a reasonable pred ic t ion of t h e ul t imate s t rength f o r t he f i b e r concrete beams a s w e l l .

2 0 6 0 . Morgan, D . R . , and D . N . Mowat, "A COMPARITIVE EVALUATION OF P L A I N , MESH, AND STEEL FIBER REINFORCED SHOTCRETE," Proceedings, Fiber Reinforced Concrete- In t e rna t iona l Symposium, A C I Special Publ icat ion SP 81-15, American Concrete I n s t i t u t e , Det ro i t , 1 9 8 4 , pp. 307-324.

L i t e ra tu re on t h e production and u s e of sho tc re t e i s very scarce . T h i s paper attempts t o present some of t he important proper t ies of shotcre te when loaded. A 5 x 5 x 2 .5 i n . shotcre te panels were fabr ica ted using p l a in concrete, p l a in shotcre te re inforced w i t h 2 x 2 i n . x 1 2 / 1 2 wire mesh, and shotcrete w i t h two concentrat ions of s t e e l f i b e r s . The panels were anchored a t 4 f t . centers and loaded t o destruct ion w i t h continuous monitoring of t h e load vs . def lec t ion . Under t h e conditions of t h e t e s t , t he improved res idua l load-carrying capacity of t he mesh and s t e e l f i b e r re inforced shotcre te a f t e r f i r s t cracking, compared t o p l a i n concrete, was well demonstrated. The s t e e l f i b e r re inforced shotcre te panels a l s o displayed improved r e s idua l load carrying capacity a f t e r t h e f i r s t crack compared t o t h e mesh reinforced sho tc re t e up t o 1 / 2 i n . deformations, and equivalent res idua l load carrying capaci ty a t deformations up t o 2 i n . The toughness and d u c t i l i t y c h a r a c t e r i s t i c s of t h e s t e e l f i b e r re inforced sho tc re t e were enhanced by increasing t h e volume concentration of s t e e l f i b e r s from 0 . 7 5 % t o 1.25% by volume.

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2 0 6 1 . Naaman, A. E . , "FIBER REINFORCED CONCRETE UNDER DYNAMIC LOADING," Proceedings, Fiber Reinforced Concrete- In t e rna t iona l Symposium, A C I Special Publ icat ion SP 81-7, American Concrete I n s t i t u t e , Det ro i t , 1984, pp. 169-179.

The o v e r a l l evaluation of t h e observed behavior of f i b e r re inforced concrete under dynamic loading i s presented. The term dynamic loading i s used t o descr ibe e i t h e r high-strain r a t e monotonic loading (impact) o r cyclic loading under high-stress range, high-strain r a t e s (simulating earthquake load ing) . Evaluation of t h e f r a c t u r e energy (or toughness) and t h e f a t igue l i f e of t h i s composite i s emphasized. The research program comprises four r e l a t e d p a r t s deal ing respec t ive ly w i t h : (1) t h e e f f e c t of t h e s t r a i n r a t e on t h e pul lout behavior of f i b e r s i n mortar, ( 2 ) t h e sur face energy of f i b e r re inforced mortar prisms i n tension, (3) t h e energy absorbed by t h e f i b e r re inforced mortar beams subjected t o impact loading, and ( 4 ) t h e behavior i n compression of f i b e r re inforced concrete cy l inders under high-strain r a t e s monotonic and cyclic loadings. While p a r t s 2 and 3 of t he program deal with s t e e l f i b e r s only, p a r t s 1 and 4 a l s o involve g l a s s , polypropylene, and polyester f i b e r s .

2 0 6 2 . Naaman, A . E . , S . P . Shah, and J . L . Throne, "SOME DEVELOPMENTS I N POLYPROPYLENE FIBERS FOR CONCRETE," Proceedings, Fiber Reinforced Concrete- In t e rna t iona l Symposium, ACI Special Publicat ion SP 81-18, American Concrete I n s t i t u t e , Det ro i t , 1984, pp. 375-396.

The main purpose of t h i s p ro j ec t was t o explore the f e a s i b i l i t y of using newly developed polypropylene (PP) f i b e r s a s reinforcement fo r port land cement concrete and t o compare t h e i r re inforc ing e f f ec t iveness w i t h asbestos , g lass , and s t e e l f i b e r s . The PP f i b e r s used were made of high t e n s i l e s t rength (up t o 80 k s i ) , high modulus, high s t r e t c h r a t i o ( 1 2 t o 1) polypropylene ribbon yarn supplied by AMOCO Synthet ic Fabr ics . The f i b e r s were c u t from a continuous s t r and obtained by properly tw i s t ing t w o PP ribbon yarns toge the r . Twisting l e d t o a subs t an t i a l increase i n t h e bonding p rope r t i e s of t h e f i b e r s (mechanical bond) and t h e i r r i g i d i t y was considered important during mixing. Different f ab r i ca t ion procedures and mortar mixes were descr ibed. R e s u l t s of an extensive series of f l e x u r a l beam and pul lout t e s t s t o improve bonding p rope r t i e s w e r e reported. Because s teel , g l a s s , asbestos , and polypropylene gave subs t an t i a l ly d i f f e r e n t s p e c i f i c g r a v i t i e s , performance comparison i s made not only on t h e b a s i s of t h e volume f r ac t ion but a l s o on weight f r a c t i o n s and r e l a t e d cos t s . Po ten t i a l usage of

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p o l y p r o p y l e n e f ibers and o t h e r organic f ibers i n c o n c r e t e matrices were stressed.

2063 . Packard , R . G . , and G . K . Ray, "PERFORMANCE OF FIBER-REINFORCED CONCRETE PAVEMENTS, P r o c e e d i n g s , F i b e r Reinforced Concre te - I n t e r n a t i o n a l Symposium, A C I S p e c i a l P u b l i c a t i o n SP 81-16, American C o n c r e t e I n s t i t u t e , Det ro i t , 1984, pp. 325-349.

The per formance of most of t h e f i b e r re inforced concrete pavement p r o j e c t s i n t h e U n i t e d S t a t e s ( 3 4 projects since 1971) are reported. These i n c l u d e e x p e r i m e n t a l s t r ee t a n d highway projects as w e l l as more r e c e n t l y c o n s t r u c t e d f u l l - s c a l e a i r p o r t pavements . While a f e w have per formed w e l l , many have deve loped defects e a r l y i n t h e i r service l i v e s . The l e s s o n s l e a r n e d s h o u l d h e l p engineers t o design f u t u r e p r o j e c t s t h a t w i l l provide be t t e r service. C a r e f u l c o n s i d e r a t i o n , and p e r h a p s a d d i t i o n a l r e s e a r c h , i s needed i n t h e areas o f j o i n t d e s i g n and s p a c i n g , load t r a n s f e r a t j o i n t s , f i b e r c o n t e n t , and t h i c k n e s s design.

2064. Raouf, Z. A . , and A . A . Hussa in , "TECHNICAL NOTES: SOME PROPERTIES OF STEEL FIBER CONCRETE AT EARLY AGES," I n t e r n a t i o n a l J o u r n a l of Cement Composites a n d L i g h t w e i g h t Concre t e , V o l . 6, N o . 2 , May 1984, p p . 117-121.

T h i s paper reports t h e u s e of pulse v e l o c i t y t o assess t h e s t r e n g t h o f s teel f i b e r reinforced c o n c r e t e a t e a r l y ages (3 t o 24 h o u r s ) . The e f f e c t s of f i b e r s on t h e s h e a r s t r e n g t h a t e a r l y ages was a l s o s t u d i e d . The r e s u l t s showed t h a t t h e a d d i t i o n o f s teel f ibe r s i n c r e a s e d t h e p u l s e v e l o c i t y , c o h e s i o n s t r e n g t h , and t h e a n g l e o f i n t e r n a l f r i c t i o n .

2 0 6 5 . R a v i n d r a r a j a h , S . R . , and C . T . Tam, "FLEXURAL STRENGTH OF STEEL FIBER REINFORCED CONCRETE BEAMS," I n t e r n a t i o n a l J o u r n a l of Cement Composites and L i g h t w e i g h t Concre t e , V o l . 6, N o . 4 , Nov 1984, p p . 273-278.

T h i s paper describes t h e i n f l u e n c e of s teel f i b e r d i s t r i b u t i o n on t h e u l t i m a t e s t r e n g t h of c o n c r e t e beams. The e f f e c t of d e l a y e d c a s t i n g between t h e p l a i n c o n c r e t e and t h e f i b e r c o n c r e t e l a y e r s on t h e u l t i m a t e s t r e n g t h o f c o n c r e t e beams w a s a l so i n v e s t i g a t e d . F o r t h e same amount o f f i b e r s used , s t r e n g t h of p a r t i a l l y r e i n f o r c e d beams w i t h fibers i n t h e bottom l a y e r s o n l y w a s a b o u t 25% more t h a n t h a t f o r f u l l y r e i n f o r c e d

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beams. The p resence of f i b e r s i n t h e compression zone d id n o t s i g n i f i c a n t l y improve t h e beams s t r e n g t h . A d e l a y i n c a s t i n g between t h e p l a i n c o n c r e t e and f i b e r c o n c r e t e l a y e r s d id n o t s i g n i f i c a n t l y change t h e u l t i m a t e s t r e n g t h of t h e p a r t i a l l y r e i n f o r c e d c o n c r e t e beams.

2066. Schrade r , E . K . , llDESIGN METHODS FOR PAVEMENTS WITH SPECIAL CONCRETES," Proceedings , Fiber Re in fo rced Concrete- I n t e r n a t i o n a l Symposium, ACI S p e c i a l P u b l i c a t i o n SP 81-9, American Concre te I n s t i t u t e , D e t r o i t , 1984, pp . 197-212.

A method f o r a d a p t i n g e x i s t i n g pavement t h i c k n e s s d e s i g n c u r v e s and formulas f o r s p e c i a l c o n c r e t e s i s p r e s e n t e d . The need f o r u s i n g materials c o n s i s t i n g of c o n c r e t e s t h a t c o n t a i n f iber r e in fo rcemen t o r high-range water r e d u c e r s i s d i s c u s s e d . These materials p o s s e s s p r o p e r t i e s which d i f f e r from c o n v e n t i o n a l r e i n f o r c e d c o n c r e t e . The r e s u l t i s a material which p o s s e s s e s f a t i g u e p r o p e r t i e s d i f f e r e n t from t h o s e assumed i n d e s i g n procedures f o r c o n v e n t i o n a l c o n c r e t e . T o u s e t h i s new mater ia l i n a p p l i c a t i o n s such as pavements, mechanical p r o p e r t i e s such as f a t i g u e shou ld be e v a l u a t e d c a r e f u l l y . Indeed, t h i s e v a l u a t i o n w i l l d e t e rmine whether o r n o t t o i n c r e a s e t h e pavement t h i c k n e s s , o r i f a more economical s e c t i o n w i t h decreased t h i c k n e s s can be used. The e f f e c t s of f a t i g u e shou ld be combined w i t h long-term s t r e n g t h g a i n s t o p r e d i c t u s a b l e s t r e n g t h s a v a i l a b l e throughout t h e d e s i g n l i f e of a pavement. I t i s p o s s i b l e t o have c o n c r e t e s w i t h lower e a r l y age l a b o r a t o r y s t r e n g t h s t h a t per form be t te r throughout t h e i r d e s i g n l i f e t h a n pavements w i th h i g h e r i n i t i a l l a b o r a t o r y s t r e n g t h s .

2 0 6 7 . S u a r i s , W . , and S . P . Shah, "TEST METHODS FOR IMPACT RESISTANCE OF FIBER REINFORCED CONCRETE," P roceed ings , Fiber Reinforced Concrete- In t e rna t iona l Symposium, A C I S p e c i a l P u b l i c a t i o n SP 81-12, American Concre te I n s t i t u t e , D e t r o i t , 1984, pp . 247-265.

I t i s w e l l a c c e p t e d t h a t f iber r e i n f o r c e d c o n c r e t e e x h i b i t s s u p e r i o r impact r e s i s t a n c e t h a n does p l a i n c o n c r e t e , and numerous t e s t s have been employed t o e v a l u a t e i t s impact r e s i s t a n c e . These i n c l u d e e x p l o s i v e tes ts and impact tes ts u s i n g p r o j e c t i l e s and impact we igh t s . Some of t h e s e t e s t s and t h e i r r e s u l t s are d e s c r i b e d i n t h i s p a p e r . Attempts t o o b t a i n more basic material pa rame te r s by conduct ing in s t rumen ted impact t e s t s w e r e d e s c r i b e d , and problems a s s o c i a t e d w i t h t h e i n t e r p r e t a t i o n of t h e i r r e s u l t s are d i s c u s s e d . F i n a l l y , a t e s t i n g method developed by t h e a u t h o r s w h i c h appears

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t o y i e l d bas i c mechanical p rope r t i e s of f i b e r re inforced concrete subjected t o impact, i s presented.

2068 . Taylor , M . A . , "COMPARISONS BETWEEN CLOSED-LOOP AND STRAIGHT METAL FIBERS I N CONCRETE," Magazine of Concrete Research, Vol. 36, N o . 1 2 6 , Mar 1 9 8 4 , pp. 31-41.

Concretes containing closed-loop f i b e r s and conventional s t r a i g h t f i b e r s are compared f o r workabili ty, bond s t rength , compressive s t rength , t e n s i l e s t rength , f l exura l s t r eng th and toughness. The concept of spacing i s t r e a t e d b r i e f l y . T e s t s i nd ica t e t h a t t h e f i b e r s have l i t t l e e f f e c t u n t i l a f t e r s i g n i f i c a n t cracking occurs. After cracking, closed loops o f f e r much b e t t e r i n t e g r i t y than s t r a i g h t f i b e r s Closed-loop f i b e r s reduce t h e v a r i a b i l i t y of both compressive and t e n s i l e s t rengths .

2 0 6 9 . Uomoto, T . , and K . Kobayashi, "MEASUREMENT OF F I B E R CONTENT OF STEEL F I B E R REINFORCED CONCRETE BY ELECTRO-MAGNETIC METHOD," Proceedings, Fiber Reinforced C o n c r e t e - I n t e r n a t i o n a l Symposium, A C I Special Publicat ion SP 81-11, American Concrete I n s t i t u t e , Det ro i t , 1984, pp. 233-246.

A simple t e s t method f o r measuring t h e s t e e l f i b e r content i n concrete i s presented. Fiber content i s considered a s one of t h e important indexes f o r q u a l i t y con t ro l of s t e e l f i b e r re inforced concrete. The prominent t es t method was compared t o o ther methods such as x-ray iaage tes ts and washing a n a l y s i s . The proposed method was found t o be n o t o n l y appl icable t o hardened concrete but a l s o t o f r e sh concrete a s wel l . The measurement can be done i n a matter of few minutes whether t h e t e s t i s performed i n t h e laboratory o r i n t h e f i e l d . A spec ia l electro-magnetic apparatus was made. The problems inves t iga ted using t h e apparatus included t h e e f f e c t s of d i s t r i b u t i o n and o r i en ta t ion of s teel f i b e r s . A p r a c t i c a l method f o r measuring s t e e l f i b e r content was c l a r i f i e d and t h e measured values showed good agreement w i t h t h e washing ana lys i s . Application of t h e apparatus f o r es t imat ing t h e modulus of rupture of beams was a l s o inves t iga ted .

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2070 . Zollo, R . F . , "COLLATED FIBRILLATED POLYPROPYLENE FIBERS," Proceedings, Fiber Reinforced Concrete- In t e rna t iona l Symposium, A C I Special Publ icat ion SP 81-19, American Concrete I n s t i t u t e , Det ro i t , 1984, pp. 397-409.

Research and development regarding f ibe r re inforced mater ia l s has evolved s t e a d i l y w i t h most notable progress having been made w i t h t h e per iodic introduct ion of new f i b e r types i n c l u d i n g mater ia l s and form o r shape, The use of c o l l a t e d f i b r i l l a t e d polypropylene f ibers (CFP) a t low f iber volumes improves many aspects of t h e production and app l i ca t ion of FRC, i n c l u d i n g mixing and placement. A series of tes ts designed t o assess t h e bas i c p rope r t i e s of CFP f ibrous concrete i n both t h e p l a s t i c and t h e hardened s t a t e a r e descr ibed. A s much a s possible , t hese tes t s were conducted i n accordance w i t h recommended ASTM and A C I Committee 544 procedures including tes ts f o r compression, f lexure, impact, s p l i t cyl inder , and pu l lou t . Other spec ia l ly designed tes ts include f lexure of composite s teel deck and concrete deck overlay specimens t o a f f e c t t h e replacement of welded wire f a b r i c i n such appl ica t ions , and shrinkage t e s t i n g . R e s u l t s i nd ica t e t h e bene f i t s derived from t h e use of CFP f i b e r s as a secondary reinforcement f o r crack con t ro l . A s i g n i f i c a n t reduction i n shrinkage i s found and there are p o s i t i v e con t r ibu t ions i n o t h e r s t r e n g t h performance a reas .

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1985

2071 . Barr, B . G . , E . D . Hasso, and K . L i u , "SHEAR STRENGTH OF FRC MATERIALS," Composites, Vol. 1 6 , N O . 4, 1985, pp. 326-334.

T h e shear s t rength of polypropylene and s t e e l f ibre-reinforced concretes have been determined using t h r e e t e s t specimen geometries - double notched beams and cy l inders i n addi t ion t o notched compact cubes. The specimen s i z e s and notch depths were var ied t o inves t iga t e whether t h e resul ts were reproducible and independent of t h e geometry. The bes t p rec is ion i n t he shear s t rength was found f o r a notch separat ion d is tance of 40-50 mm (1.57-1.97 i n . ) i n t he beam and c y l i n d r i c a l specimens. The cy l ind r i ca l specimens gave t h e bes t p rec is ion ove ra l l . The shear s t r eng th of t h e polypropylene f iber-reinforced concrete decreased w i t h increasing f i b e r content whereas t h a t of s t e e l f ib re- re inforced concrete increased. The shear s t r eng ths were found t o be dependant on t h e d i r e c t i o n of cas t ing of t h e specimens.

2 0 7 2 . Barr, B . , and M . R . Mohamad Noor, "THE TOUGHNESS I N D E X OF STEEL F I B E R REINFORCED CONCRETE," Journal of t h e American Concrete I n s t i t u t e , Vol. 82, No. 5, Sept-Oct 1985, pp. 622-629 .

A n a l t e r n a t i v e de f in i t i on of t h e toughness i n d e x i s proposed which has a number of advantages over t h e A C I d e f i n i t i o n . The toughness index i s obtained from t h e load-deflection graph and i s given by t h e a rea under t h e graph ( a t t h e point of two t i m e s t h e de f l ec t ion a t 1st crack) divided by 4 times t h e area under the graph a t t h e point of 1st crack. The proposed d e f i n i t i o n has t h e advantage t h a t it can be used f o r both conventionally mixed f i b e r reinforced concrete mortars and sheet l i k e mater ia l such a s g l a s s f i b e r re inforced concrete, GFRC. The toughness index r e s u l t s were obtained from th ree notched test-specimen geometries: compact compression, notched beam, and compact tension t e s t specimens. The r e s u l t s were found t o be independent of both geometry and notch depth and showed t h a t t h e toughness index of SFRC increased by 1 0 0 % a s t h e f i b e r content was increased i n t he range of 0.03-0.9% b y volume.

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2073. Bausch, D . , "NEW STEEL-FIBER CONCRETE TECHNIQUES FOR TUNNELING AND ROAD B U I L D I N G [STAHLFASERBETON FUER DEN STOLLEN- UND STRASSENBAU BEISPLIEL: BUNDESWEHRBAUTEN B E 1 LORCH], Beton, H e r s t e l l u n g , Verwendung, V o l . 35, N o . 1, J a n 1985, p p . 17-19.

A new s t e e l - f i b e r s h o t c r e t e t e c h n o l o g y i s b e i n g p r a c t i c e d i n a cont rac t sect ion o f t h e 'Bundeswehr' i n t h e Coblence area. More t h a n 200 e x p e r t s have c o n t r i b u t e d t h e i r knowledge about t u n n e l i n g and r o a d b u i l d i n g measures which are said t o be un ique i n t h i s p ro jec t . The b u i l d i n g - s i t e report in fo rms o f t h e p rac t ica l a p p l i c a t i o n o f t h e s e new t e c h n i q u e s .

2074. F a n e l l a , D . A . , and A. E . Naaman, "STRESS-STRAIN PROPERTIES OF FIBER REINFORCED MORTAR I N COMPRESSION," J o u r n a l o f t h e A m e r i c a n Concre t e I n s t i t u t e , V o l . 8 2 , N O . 4 , July-Aug 1985, pp . 475-483.

The purpose o f t h i s s t u d y w a s t o i n v e s t i g a t e and e v a l u a t e t h e stress-strain properties of f i b e r r e i n f o r c e d c o n c r e t e a n a l y t i c a l l y and e x p e r i m e n t a l l y . Three t y p e s o f f i b e r s were u s e d : s teel , glass, and p o l y p r o p y l e n e . F o r e a c h s teel f i b e r t y p e , t h r e e a s p e c t r a t i o s w e r e i n v e s t i g a t e d i n c o n j u n c t i o n w i t h t h r e e mortar matrices o f i n c r e a s i n g compress ive s t r e n g t h . The i n f l u e n c e of t h e s e p a r a m e t e r s on t h e peak stress and s t r a i n , t h e toughness r e s i s t a n c e , and t h e d e s c e n d i n g po r t ion o f t h e s t ress-s t ra in c u r v e i s s t u d i e d .

2075. G r a m , H . , "PRODUCTS OF STEEL FIBER REINFORCED CONCRETE- QUALITY ASSURANCE," P roceed ings , S t e e l F i b e r Concre t e , US-Sweden J o i n t Seminar (NSF-STU) Swedish Cement & Concrete Research I n s t i t u t e , Jun 1985, p p . 515-520.

S t e e l f i b e r r e i n f o r c e d concrete opened new a p p l i c a t i o n s i n t h e u s e of concrete. I n addi t ion t o new p r o d u c t i o n t e c h n i q u e s and labor t r a i n i n g , t h e i n t r o d u c t i o n o f t h i s new material a l so requi res new ways o f c o n t r o l l i n g t h e p r o d u c t i o n i n t h e f a c t o r y and new ways o f s p e c i f y i n g and check ing e x p e c t e d p r o p e r t i e s f o r t h e cus tomer o r u s e r o f t h e p r o d u c t . I t may be n e c e s s a r y t o i n t r o d u c e new t e s t methods and equ ipmen t . The need f o r q u a l i t y a s s u r a n c e a p p l i e d t o t h e p r o d u c t i o n o f b a l c o n i e s made o f f i b e r s h o t c r e t e i s discussed.

332

2 0 7 6 . Hi l lerborg, A . , "DETERMINATION AND S I G N I F I C A N C E OF THE FRACTURE TOUGHNESS OF STEEL FIBER CONCRETE," Proceedings of t h e Steel Fiber Concrete, US-Sweden J o i n t Seminar (NSF-STU), Stockholm, Sweden, J u n e 1985, pp. 257-271.

The t e n s i l e f r a c t u r e behavior of s t e e l f i b e r concrete i s discussed and compared t o t h a t of p l a in concrete . Where as p l a in concrete ceases t o t r a n s f e r stresses a f t e r cracking, s t e e l f i b e r s continue t o t r a n s f e r appreciable stresses even a f t e r t h e occurrence of wide cracks. The e f f e c t of t h i s d i f fe rence on the behavior of notched and unnotched beams w a s analysed using f i n i t e elements. T h i s was done using a f i c t i t i o u s crack model and a simple approximation f o r t h e stress-deformation proper t ies of t h e damaged zone . I t was concluded t h a t l i n e a r e l a s t i c f r a c t u r e mechanics can never be appl icable t o steel f i b e r concrete and t h a t p l a s t i c i t y theo ry should be employed in s t ead .

2 0 7 7 . Johnston, C . D . , "TOUGHNESS OF STEEL F I B E R REINFORCED CONCRETE," Proceedings of t h e Steel Fiber Concrete, US-Sweden Jo in t Seminar (NSF-STU) , Stockholm, Sweden, June 1985, pp. 333-360.

Methods of quan t i t a t ive ly determining t h e toughness of s t ee l f iber - re inforced concrete are judged and compared i n terms of four proposed c r i t e r i a . The methods discussed and compared include instrumented weighted-pendulum impact, instrumented drop-weight impact ( A C I 5 4 4 procedure), and four a l t e r n a t i v e forms of slow f lexure ( including A C I 544, Japan Concrete I n s t i t u t e , and ASTM recommended procedures, where toughness parameters a r e derived from t h e load-deflection curve f o r a simply supported beam subjected t o t h i r d point loading.

2 0 7 8 . Lankard, D . R . , "PREPARATION, PROPERTIES AND APPLICATIONS OF CEMENT-BASED COMPOSITES CONTAINING 5 TO 20 PERCENT STEEL F I B E R , " Proceedings of t he S t e e l Fiber Concrete, US-Sweden J o i n t Seminar (NSF-STU) , Stockholm, Sweden, J u n e 1985, pp. 199-217.

S l u r r y - i n f i l t r a t e d f i b e r reinforced concrete ( S I F C O N ) i s preplaced-fiber concrete (analogous t o preplaced aggregate concrete) with the placement of s t ee l f i b e r s i n a form o r mold, o r on a subs t r a t e , as t h e i n i t i a l construction s t e p . The preplaced f i b e r s a r e then i n f i l t r a t e d w i t h a f ine-grained, hydraul ic cement-based s l u r r y . Laboratory and f i e l d experience proved t h e uniqueness of S I F C O N as a concrete mater ia l t h a t exhib i t both high s t rength and high d u c t i l i t y . I t s

333

a b i l i t y t o resist spa l l i ng and cracking i n s t a t i c and dynamic loading s i t u a t i o n s i s f a r superior t o conventional SRFC and t o re inforced concrete . S I F C O N has t h e a b i l i t y t o be constructed a s massive sec t ions a s w e l l a s i n very t h i n sec t ions . This permits considerat ion i n a broad range of p o t e n t i a l appl ica t ions which include r e h a b i l i t a t i o n and r epa i r , r e f r ac to ry concrete, p recas t concrete, and explosive-resis tant s t r u c t u r e .

pavement and bridge

2 0 7 9 . L i u , K . , B . G. Barr, and J . Watkins, "MODE 11 FRACTURE OF F I B E R REINFORCED CONCRETE MATERIALS, 'I In t e rna t iona l Journal of Cement Composites and Lightweight Concrete, Vol. 7, No. 2 , May 1985, pp. 93-101.

T h i s paper descr ibes experimental r e s u l t s obtained f o r mode I1 ( shear ) f r a c t u r e of polypropylene and s t e e l f i b e r re inforced concrete. The mode I1 t e s t specimens w e r e 100 x 100 x 200 mm prisms, modified by t h e introduct ion of two opposite but displaced notches. A shear stress d i s t r i b u t i o n was observed i n t h e area between t h e roots of t h e two notches when t h e specimen was subjected t o a longi tudinal c e n t r a l loading. The f r a c t u r e toughness r e s u l t s i n shear were independent of t h e f i b e r content of t h e m i x f o r both types of f i b e r s . Toughness index r e s u l t s which a r e a measure of t h e post cracking performance of t he mater ia l were a l s o reported f o r s teel f i b e r re inforced concrete . Toughness i n d e x was observed t o increase w i t h increasing f i b e r content but o n l y a t half t h e ra te which i s achieved under mode I (crack opening displacement) condi t ions.

2080. Lorentsen, M . , "STEEL FIBER CONCRETE FOR STRUCTURAL ELEMENTS," Proceedings of t h e Steel Fiber Concrete, US-Sweden Jo in t Seminar (NSF-STU) , Stockholm, Sweden, June 1985, pp. 4 2 1 - 4 4 2 .

The research program described i n t h i s paper was conducted a t t he Royal I n s t i t u t e of Technology. Questions on t h e use of s t e e l f i b e r re inforced concrete a s a load bearing s t r u c t u r a l element were addressed. The objec t ive was t o study t h e f e a s i b i l i t y of introducing SFRC t o t h e Swedish market and t o s tandardize t h e design methods and tes t s r e l a t e d t o normally reinforced and pres t ressed concrete s t r u c t u r a l elements. SFRC was found t o be very e f f e c t i v e i n r e s i s t i n g shear and was recommended t o be used i n combination w i t h p res t ressed and nonprestressed reinforcement.

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2081. Mangat, P . S., and K . Gurusamy, "STEEL FIBER REINFORCED CONCRETE FOR MARINE APPLICATIONS," Proceedings, 4 t h In t e rna t iona l Conference on Behavior of Offshore S t r u c t u r e s , Delf t , The Netherlands, 1985, pp. 867-879 .

The d u r a b i l i t y of steel f i b e r re inforced concrete prism specimens exposed t o splash zone conditions i s discussed. Results up t o 300 cycles of marine spray exposure suggest t h a t t h e mechanical s t rength development of f i b e r concrete i s not impaired. The modulus of rupture increased by 1 0 0 % and up t o 1 6 f o l d increase i n energy absorption capaci ty was ev ident . Chloride penetrat ion was found reasonably represented by F l i c k ' s Law of d i f fus ion . The e f f e c t i v e surface of concentration of chlor ide was found t o be between 1 . 4 8 and 1 . 7 4 % by weight of cement and t h e d i f fus ion c o e f f i c i e n t ranged between 3.41 t o 7.13 x E-8 square cm./sec. The surface concentration increased w i t h time but t h e d i f fus ion coe f f i c i en t decreased. The chlor ide pene t ra t ion was somewhat higher i n f i b e r re inforced prism specimens when compared t o corresponding p l a in concrete specimens. N o corrosion of i n t e r n a l f i b e r s was evident even though chlor ide l e v e l s were up t o 1 . 7 % b y weight of cement a t zones near t h e surface of t he uncracked f i b e r prism specimens.

2082. Mangat, P . S., and M . Motamedi Azari, "A THEORY FOR THE CREEP OF STEEL F I B E R REINFORCED CEMENT MATRICES UNDER COMPRESSION," Journal of Material Science, V o l . 2 0 , 1985, pp. 1119-1133.

T h i s paper presents a t h e o r e t i c a l model t o pred ic t t h e creep of matrices reinforced w i t h randomly or ien ted d i s c r e t e s t e e l f i b e r s . The theory considers t h a t t h e composite i s represented by an al igned s t e e l f i b e r which i s surrounded b y a t h i c k c y l i n d e r of t h e cement matrix. The f i b e r provides r e s t r a i n t t o the flow component of creep of t h e matrix through t h e f i b e r matrix i n t e r f a c i a l bond s t rength . The delayed i n e l a s t i c s t r a i n component of t h e creep i s unaffected by the f i b e r . The bond s t rength was shown t o be a function of t h e shrinkage of t he cement matrix and t h e r a d i a l deformation caused by t h e sustained a x i a l s t r e s s . I n addi t ion, t h e s t a t e of s t r e s s i n t h e matrix a t t he in t e r f ace i s suggested t o influence g r e a t l y t h e bond s t r eng th . The theory was val idated by experimental data on concrete and mortar matrices re inforced w i t h melt e x t r a c t and hooked s teel f i b e r s , a t sustained s t r e s s - s t r eng th r a t i o s of 0.3 and 0 . 5 5 . An empirical expression i s presented t o determine t h e creep of steel f i b e r re inforced concrete, based on the knowledge of t h e creep i n t he unreinforced matrices and f i b e r s i z e and volume f r a c t i o n .

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2083. Mansur, M . A . , and P . Paramasivam, "FIBER REINFORCED CONCRETE BEAMS I N TORSION, BENDING, AND SHEAR, Journal of t h e American Concrete I n s t i t u t e , V o l . 82, No. 1, Jan-Feb 1985, pp. 33-39.

The r e s u l t s of 33 s t e e l f i b e r re inforced concrete beams under d i f f e r e n t combination of t o r s ion , bending, and t ransverse shear were reported. Based of t he observed s k e w bending mechanism of t o r s i o n a l f a i l u r e , equations were derived f o r t h e ana lys i s of such beams. The t h e o r e t i c a l model gives good predic t ions of t he u l t imate torque, mode of f a i l u r e , and torsion-bending-shear i n t e rac t ion behavior.

2084. Mansur, M . A , , and T . Y . L i m , "TORSIONAL BEHAVIOR O F REINFORCED F I B E R CONCRETE BEAMS," I n t e rna t iona l Journal of Cement Composites and Lightweight Concrete, V o l . 7 , NO. 4 , NOV 1985, pp. 261-267.

P u r e t o r s ion t e s t s w e r e conducted on rectangular f i b e r concrete beams reinforced i n t h r e e d i f f e r e n t ways; without bar reinforcement, w i t h longi tudina l bars only, and w i t h longi tudinal bars and t ransverse hoops. 15 tes ts inves t iga ted t h e influence of volume f r a c t i o n of d i s c r e t e s t e e l f ibers and t h e amount of longi tudina l and t ransverse reinforcement on t h e behavior and s t r eng th of beams. The tes t r e s u l t s i nd ica t e t h a t t h e f i b e r s can be bes t u t i l i z e d i n r e s i s t i n g t o r s i o n a l load only when t h e beams a r e provided w i t h continuous reinforcement i n both d i r ec t ions .

2085. Naaman, A . E . , "FIBER REINFORCEMENT FOR CONCRETE," Concrete In te rna t iona l , V o l . 7 , No. 3, Mar 1985, pp. 21-25.

A s e l e c t i v e chronological review of t he e a r l i e s t pa t en t s on f i b e r reinforcement f o r concrete i s presented. The underlying idea fo r each patent i s explained and t h e objec t ives a r e evaluated. The most des i r ab le f i b e r c h a r a c t e r i s t i c s a r e pointed out and c u r r e n t l y ava i l ab le f i b e r s a r e described.

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2086. Naaman, A . E . , and J . R . Hornrich, "PROPERTIES OF HIGH-STRENGTH FIBER REINFORCED CONCRETE," P r o c e e d i n g s o f ACI Symposium on High S t r e n g t h Concre t e , H . R u s s e l l , E d i t o r , SP-87, 1985, pp . 233-249.

The pu rpose o f t h i s s t u d y was t o i n v e s t i g a t e t h e e f f e c t s o f f i b e r r e i n f o r c e m e n t on t h e monotonic compress ive s t r e s s - s t r a i n propert ies o f h i g h s t r e n g t h f i be r r e i n f o r c e d mortar, i n p a r t i c u l a r , t h e d e s c e n d i n g b r a n c h . Toughness and d u c t i l i t y were s t u d i e d u s i n g s teel , po lypropy lene , and glass f i b e r s f o r v a r i o u s volume f r a c t i o n s and aspect r a t io s .

2087. Narayanan, R . , and A . S . Kareem-Palanjian, "SPACE TRUSS MODEL FOR FIBER-CONCRETE BEAMS I N TORSION," S t r u c t u r a l Eng inee r , V o l . 63, No. 1, Mar 1985, pp . 1 4 - 1 9 .

An a n a l y t i c a l model based on t h e s p a c e t r u s s concep t i s proposed f o r p r e d i c t i n g t h e t o r s i o n a l s t r e n g t h of s t e e l - f i b e r - r e i n f o r c e d concrete (SFRC) beams. The method i s val idated by comparison w i t h t h e t e s t d a t a ava i lab le i n p u b l i s h e d l i t e r a t u r e f o r t h e f o l l o w i n g cases: (1) beams r e i n f o r c e d w i t h f i b e r s ; ( 2 ) prestressed f i b e r concrete beams; (3) s teel f i b e r s i n combina t ion w i t h l o n g i t u d i n a l r e i n f o r c e m e n t ; and ( 4 ) s t ee l f ibe r s , l o n g i t u d i n a l r e i n f o r c e m e n t , and s t i r r u p s . I t i s s u g g e s t e d t h a t t h e proposed model i s a l so v a l i d f o r beams c o n t a i n i n g c o n v e n t i o n a l r e i n f o r c e m e n t o n l y ( i . e . , z e r o f i b e r c o n t e n t ) .

2088. Nordin, A . , and A . Ska rendah l , "STEEL FIBER CONCRETE- DEVELOPMENT AND USE," P roceed ings of t h e S t e e l F i b e r Concre t e , US-Sweden J o i n t Seminar (NSF-STU), Stockholm, Sweden, June 1985, pp . 143-157.

T h i s p a p e r d i s c u s s e s t h e development , manufac tu r ing , and u s e of p r e c a s t SFRC p r o d u c t s . N e w p r o d u c t i o n t e c h n i q u e s and some i m p o r t a n t a s p e c t s o f SFRC are addressed. Ekebro AB manufac tu res a number of SFRC p r o d u c t s . The f i r s t p r o d u c t i o n l i n e w a s based on a s l i g h t l y m o d i f i e d c o n v e n t i o n a l mix ing and c a s t i n g t e c h n i q u e . The company had deve loped a f i b e r s h o t c r e t e t e c h n i q u e c h a r a c t e r i z e d p r i m a r i l y by t h e c u t t i n g of t h e w i r e s t o f i b e r s i n t h e s p r a y n o z z l e .

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2089 . Robins, P . J . , and S . A . A u s t i n , '"CORE POINT-LOAD TEST FOR STEEL-FIBER-REINFORCED CONCRETE," Magazine of Concrete Research, Vol. 37, No. 133, Dec 1985, pp. 238-242.

The point-load t e s t , more commonly used i n geotechnical prac t ice , i s evaluated f o r appl ica t ions t o concrete t e s t i n g a s a p o t e n t i a l method f o r es t imat ing t h e s t rength of s tee l - f iber - re inforced concrete . Both diametral and a x i a l t es t configurat ions were inves t iga ted and the e f f e c t of load d i r ec t ion i n r e l a t i o n t o f i b e r o r i en ta t ion was explained. While the diametral tes t i s s u i t a b l e f o r measuring t h e s t r eng th of random three-dimensionally or ien ted f i b e r concrete, t h e a x i a l tes t was shown t o be more appropriate f o r assess ing t h e p rope r t i e s of an an i so t rop ic mater ia l such a s asprayed s t e e l - f i b e r concrete .

2 0 9 0 . Rostasy, F . S., and K . Hartwich, "COMPRESSIVE STRENGTH AND DEFORMATION OF STEEL FIBER REINFORCED CONCRETE UNDER H I G H RATE OF STRAIN," I n t e rna t iona l Journal of Cement Composites and Lightweight Concrete, Vol. 7 , No. 1, Feb 1985, pp. 21-28.

The influence of high s t r a i n r a t e s on t h e s t r eng th and deformation of f i b e r re inforced concrete ( 0 . 7 5 % and 1 .5% by volume hooked and s t r a i g h t f i b e r s ) i n un iax ia l and eccentric compression t e s t s i s reported. The t e s t s were performed on normal weight concrete w i t h a mean s t rength of 25 MPa (3 .6 k s i ) . R e s u l t s showed t h a t t h e dynamic s t rength i s about 2 0 % higher, a t which t h e u l t imate s t r a i n a l s o increases by 1 0 - 2 0 % . The f a i l u r e of t h e f i b e r concrete specimens occurred i n a much d u c t i l e manner a s compared t o p l a i n concrete . T h i s was found f o r s t a t i c and impact loading t o t h e same ex ten t . The r e s idua l s t a t i c s t rength of eccen t r i ca l ly loaded concrete was s l i g h t l y diminished by a dynamic preloading.

2 0 9 1 . Sahloul, M . , and X . Destree, "PRACTICAL I N V E S T I G A T I O N S I N T O STEEL F I B E R REINFORCED INDUSTRIAL FLOORS," Betonwerk and Fert igtei l -Technik [Prakt ische Untersuchungen Von Industrieboeden M i t S tah l fasern B e w e h r t ] , Vol. 51, No. 11, Nov 1985, pp. 747-751 .

The t e s t s l a b was designed f o r a concentrated load of 50 KN and contained a s a f e t y f a c t o r of 2 ( load a t rupture 1 0 0 K N ) . However, according t o the t es t r e s u l t s , t h e sa fe ty f a c t o r was found t o be g r e a t e r than 5 . The r e s u l t s showed t h a t high q u a l i t y FRC mixes can be obtained w i t h the addi t ion of a p l a s t i c i z e r and no v ib ra t ion .

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2 0 9 2 . Schupack, M . , "DURABILITY OF SFRC EXPOSED TO SEVERE ENVIRONMENTS," Proceedings of t he Steel Fiber Concrete, US-Sweden J o i n t Seminar (NSF-STU) , Stockholm, Sweden, June 1985, pp. 4 7 9 - 4 9 6 .

The corrosion performance experience of S F R C i n t h r e e d i f f e r e n t aggressive environments and t h e r e s u l t s of laboratory t e s t s performed are described. The corrosion of concrete was observed t o be l imi ted t o t h e uncracked surface f o r specimens t h a t have good a i r entrapment and a w / c r a t i o = 0 . 5 exposed t o a 1 0 year f reez ing and thawing cycles. The d u r a b i l i t y of both p l a i n concrete and FRC specimens was observed t o be the same a f t e r t e s t i n g . The f i b e r s of cracked SFRC specimens were corroded w i t h t i m e .

2093. Shah, S. P . , and A . Skarendahl, "STEEL F I B E R CONCRETE, US-SWEDEN J O I N T SEMINAR (NSF-STU)," Proceedings of the Steel Fiber Concrete, US-Sweden J o i n t Seminar (NSF-STU) , Stockholm, Sweden, June 1985.

T h i s seminar proceedings conta in 25 papers which dea l w i t h t h e addi t ion of randomly d i s t r i b u t e d s t e e l f i b e r s t o b r i t t l e cement based matrices. The t op ic s covered include: s tee l f i b e r re inforced shotcre te , s t e e l f i b e r shotcre te methods, s teel f i b e r use i n pavements and bridge decks, precast s teel f i b e r concrete panels, s t e e l f i b e r percentages i n composites, f r a c t u r e and toughness of s t ee l f i b e r concrete, mechanical proper t ies and d u r a b i l i t y of SFRC, s t e e l f i b e r concrete product performance, and q u a l i t y of s t ee l f i b e r re inforced concrete products.

2 0 9 4 . Shah, S . P . , and Y . S . Jeng, "FRACTURE RESISTANCE OF STEEL F I B E R REINFORCED CONCRETE," Proceedings of t h e S t e e l Fiber Concrete, US-Sweden Jo in t Seminar (NSF-STU), Stockholm, Sweden, June 1985, pp. 273-297.

A f r a c t u r e mechanics based t h e o r e t i c a l model i s presented t o pred ic t t h e crack propagation r e s i s t ance of s t e e l f i b e r re inforced cement based composites. Mode 1 crack propagation i n s tee l f i b e r mortars a re t r e a t e d i n t h e proposed model. The mechanism of t h e f r a c t u r e res is tance of SFRC can be separated as : s u b - c r i t i c a l crack growth i n t h e m a t r i x and t h e beginning of t h e f i b e r bridging e f f e c t ; post c r i t i c a l crack growth i n t h e matrix such t h a t t h e n e t stress i n t e n s i t y f a c t o r due t o t h e applied load and t h e f i b e r bridging closing s t r e s s e s remain constant; and a f i n a l s tage where t h e r e s i s t ance t o crack separat ion i s provided exclusively by f i b e r s . The response t o FRC during a l l these s tages w a s successful ly predicted from t h e knowledge of t h e

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m a t r i x f r a c t u r e proper t ies and t h e pull-out load vs . s l i p r e l a t ionsh ip of a s ing le f i b e r . The model was v e r i f i e d with t h e results of experiments conducted on notched beams reported here as w e l l as by o ther researchers .

2095. Swamy, R . N . , "STEEL FIBER CONCRETE FOR BRIDGE DECK AND B U I L D I N G FLOOR APPLICATIONS," Proceedings of t h e S t e e l Fiber Concrete, US-Sweden J o i n t Seminar (NSF-STU) , Stockholm, Sweden, June 1985, pp. 443-478.

This paper presents a comprehensive review on t h e u s e of s teel f i b e r concrete f o r bridge decks and bui ld ing f l o o r s l a b s . The da ta shown cover both normal weight and l ightweight concrete with s teel f i b e r s . Emphasis i s given t o t h e mix proportioning of t h e two concrete types so a s t o produce workable and compatible mixes without causing f i b e r bundling, segregation o r bleeding. Both mater ia l and engineering p rope r t i e s of s t e e l f i b e r concrete are discussed. The s t r u c t u r a l behavior of conventional re inforced concrete s l abs containing s teel f i b e r s i s presented w i t h p a r t i c u l a r reference t o deformation, cracking, s e rv i ce loads, and f a i l u r e . The s i g n i f i c a n t advantage of s t e e l f i b e r s i n s t r u c t u r a l members i s highl ighted The da ta presented in t h i s paper show t h a t SFRC of s t r u c t u r a l q u a l i t y can be s a t i s f a c t o r i l y proportioned f o r t h e u s e i n concrete br idge decks and bui lding f l o o r s with adequate flow and compact ibi l i ty c h a r a c t e r i s t i c s w i t h any s igns of f i b e r bundling o r non-uniform d i s t r i b u t i o n of f i b e r s . I t i s shown t h a t such concrete can be designed t o have adequate e a r l y s t rength , and can enhance t h e cracking, deformation, and s t rength behavior of re inforced concrete s l abs made with f i b e r concrete . Extensive data a r e presented t o show t h a t i n both normal weight and l ightweight concrete s labs , t he presence of f i b e r s i n concrete cont ro ls cracking and deformation, enhances s e r v i c e a b i l i t y and diagonal cracking loads, and imparts dramatic improvements i n d u c t i l i t y and energy absorption p rope r t i e s .

2 0 9 6 . Swamy, R . N . , and H . M . Bahiya, "THE EFFECTIVENESS OF STEEL F I B E R S AS SHEAR REINFORCEMENT," Concrete I n t e r n a t i o n a l : Design C Construction, V o l . 7 , N o . 3 , Mar 1985, pp. 35-40.

To evaluate t h e e f fec t iveness of s t e e l f i b e r s on shear s t rength and shear reinforcement, tes ts were conducted on both T-beams w i t h 2 t o 4 % main re inforc ing s t e e l and on rectangular beams. T h e f i b e r content was var ied t o a maximum of 1 . 2 % by volume, and t h e a b i l i t y of f i b e r s and s t i r r u p s t o a c t compositely was s tud ied .

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I t w a s shown t h a t f ibers c o n t r o l t h e dowel c r a c k i n g , and a l s o c o n t r o l d e f l e c t i o n , s t r a i n s , and r o t a t i o n s due t o shear l o a d s . S tee l fibers clearly enhance t h e u l t i m a t e shear s t r e n g t h of r e i n f o r c e d c o n c r e t e beams, w i t h t h e e x t e n t of such i n c r e a s e depending on t h e shape of t h e c r o s s - s e c t i o n , t h e amount of t e n s i o n s t ee l , and t h e f i b e r volume.

2 0 9 7 . Yerex 11, L . , T . H . Wenzel, and R . Davies, "BOND STRENGTH OF M I L D STEEL I N POLYPROPYLENE FIBER REINFORCED CONCRETE," J o u r n a l of t h e American Concre te I n s t i t u t e , V o l . 8 2 , No. 1, Jan-Feb 1985, pp . 40-45 .

An expe r imen ta l s t u d y w a s conducted t o de te rmine t h e effects of po lypropylene f ibers on t h e bond between c o n c r e t e and conven t iona l m i l d s teel r e in fo rcemen t . Two f iber l e n g t h s , f o u r f iber c o n t e n t s , and two water-cement r a t i o s were used f o r t h i s s tudy , as w e l l as t w o s i z e s of conven t iona l mi ld s t ee l r e i n f o r c e m e n t . T h e f i r s t series of t h e tests i n v e s t i g a t e d t h e ASTM S tanda rd T e s t Method C 23471 which describes t h e bond stress-slip r e l a t i o n s h i p . A second series of t es t s were des igned and used t o i n d i c a t e changes i n t h e t r a n s f e r l e n g t h s of t h e s e v e r a l c o n c r e t e mixes and mi ld s t e e l r e in fo rcemen t combina t ions . R e s u l t s showed t h a t t h e a d d i t i o n of polypropylene fibers to concrete does no e f f e c t t h e bond s t r e n g t h between t h e polypropylene f iber r e i n f o r c e d conc re t e , PFRC, and t h e conven t iona l m i l d s t e e l . The PFRC s t u d i e s e x h i b i t e d bond s t r e n g t h s imilar t o conven t iona l c o n c r e t e . Thus , d e s i g n e q u a t i o n s in t ended f o r conven t iona l r e i n f o r c e d c o n c r e t e may a l s o be used f o r PFRC.

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2098. Absi, E . , and A . E . Naaman, "MODELE RHEOLOGIQUE POUR LES BETONS DE FIBRES," P roceed ings , 3rd RILEM I n t e r n a t i o n a l Symposium on F i b e r R e i n f o r c e d Cement Composites, S h e f f i e l d , England, J u l y 1986.

A s t ress -s t ra in r e l a t i o n s h i p i s p roposed t o model t h e b e h a v i o r of f i b e r r e i n f o r c e d c o n c r e t e i n u n i a x i a l compress ion , e s p e c i a l l y i n t h e post c r a c k i n g r e g i o n where e x t e n s i v e c r a c k s and m i c r o c r a c k s are p r e s e n t . The e x p r e s s i o n allows f o r the model ing o f t h e a s y m p t o t i c b e h a v i o r observed a t h i g h d e f o r m a t i o n s , where such b e h a v i o r i s a l so a known c h a r a c t e r i s t i c s o f s o i l s . T h i s s t u d y r e p r e s e n t s a f i r s t e f f o r t by t h e a u t h o r s t o i d e n t i f y a n d model c e r t a i n mechan ica l c h a r a c t e r i s t i c s t h a t are common t o c o n c r e t e a n d s o i l mater ia ls .

2099. Akihama, S . , T . Suenage,H. Nakagawa, and K . Suzuk i , "INFLUENCES OF FIBER STRENGTH AND POLYMER IMPREGNATION ON THE MECHANICAL PROPERTIES OF CARBON FIBER REINFORCED CEMENT COMPOSITES," P r o c e e d i n g s , 3rd RILEM I n t e r n a t i o n a l Symposium on F i b e r R e i n f o r c e d Cement Composites, S h e f f i e l d , England, J u l y 1986.

The mechan ica l p r o p e r t i e s o f CFRC r e i n f o r c e d w i t h s h o r t discrete carbon f i b e r s are affected by t h e properties o f t h e f i b e r and cement m a t r i x , volume content , and t h e f i b e r - m a t r i x in te r fac ia l bond s t r e n g t h . T o examine t h e s e effect.^, direct t e n s i l e , compressive, f l e x u r a l , and f i b e r - m a t r i x i n t e r f a c i a l bond s t r e n g t h tes ts were conduc ted u s i n g two t y p e s of carbon f i b e r s and t h r e e t y p e s o f matrices, w i t h a maximum volume c o n t e n t of 5 . 3 % . P i t c h - b a s e d ca rbon f i b e r s were used , GP-CF, as w e l l as h i g h s t r e n g t h a n d h i g h modulus PAN t y p e carbon f i b e r s , HP-CF. To examine t h e e f f e c t s o f t h e matrices, t h e f o l l o w i n g t h r e e t y p e s of CFRC w e r e t es ted : a i r c u r e d CFRC, a u t o c l a v e d CFRC and polymer impregna ted CFRC a f t e r a u t o c l a v i n g . Based on t h e r e s u l t s o b t a i n e d , t h e i n t e r f a c i a l bond s t r e n g t h w a s changed by d i f f e r e n t c u r i n g methods, w i t h and w i t h o u t i m p r e g n a t i o n . The t e n s i l e and f l e x u r a l s t r e n g t h s were c o n s i d e r a b l y changed, even though t h e t y p e of f i b e r and f i b e r volume c o n t e n t w e r e t h e same.

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2 1 0 0 . Akihama, S . , H . Nakagawa,T. Takada, and M . Yamaguchi, "EXPERIMENTAL S T U D Y ON ARAMID FIBER REINFORCED CEMENT COMPOSITES AFRC MECHANICAL PROPERTIES OF AFRC WITH SHORT FIBERS," Proceedings, 3rd RILEM I n t e r n a t i o n a l Symposium on Fiber Reinforced Cement Composites, Shef f i e l d , England, J u l y 198 6.

An experimental study w a s performed t o confirm t h e e f f e c t s of aramid f i b e r used f o r re inforc ing cement-based matrices and t o obtain bas i c da ta f o r applying AFRC t o t h e c o n s t r u c t i o n and c i v i l engineering f i e l d s . The following s t rength tes ts were performed: d i r e c t t ens i l e , compressive, and f l e x u r a l t e s t s . Temperature, f i b e r length, volume c o n t e n t , age, and o the r parameters were var ied. The e f f e c t s of autoclave curing on drying shrinkage of AFRC were a l s o t e s t e d . The optimum autoclaving temperature w a s 1 4 0 degrees C which reduced t h e shrinkage t o around 3 7 % of t h a t by curing i n a i r . N u m e r i c a l r e s u l t s were obtained f o r t he d i r e c t t ens i l e s t r eng th and t h e modulus of rupture .

2101 . Akihama, S . , M . Kobayashi,T. Suenaga,H. Nakagawa, and K . Suzuk i , "EFFECT OF CFRC SPECIMEN GEOMETRY ON FLEXURAL BEHAVIOR," Proceedings, 3rd RILEM In t e rna t iona l Symposium on Fiber Reinforced Cement Composites, Shef f ie ld , England, 1 9 8 6 .

F l e x u r a l t e s t s were performed on beams and planks w i t h var ious shapes and dimensions t o obtain bas i c data f o r e s t ab l i sh ing a design method f o r CFRC members. These tes ts were performed by changing f a c t o r s such as t h e depth of t h e beam, span, t h e shear span (a /d) r a t io , t h e loading method, and t h e s p e c i f i c g rav i ty of CFRC. The e f f e c t of these f ac to r s on t h e modulus of rupture was inves t iga ted . As a r e s u l t of these experiments, it was proved t h a t t h e modulus of rupture of l a r g e s i z e CFRC specimens subjected t o t h i r d point loading i s sharply reduced a s t h e i r dimensions a re increased, compared w i t h r e s u l t s obtained f o r center point loading t e s t s (span = 10 cm) using 4 x 4 x 1 6 cm t e s t specimens.

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2102. Allen, H . G . , and C . K . J o l ly , "PREDICTION OF THE CREEP STRAIN BEHAVIOUR AND LONG-TERM TENSILE STRENGTH OF GLASS FIBRE REINFORCED CEMENTS AND MORTARS WHEN EXPOSED TO WEATHERING," Proceedings, 3rd RILEM In t e rna t iona l Symposium on Fiber Reinforced Cement Composites, Shef f ie ld , England, Ju ly 1 9 8 6 .

This paper i s based on t h e resul ts of s tud ie s of creep s t r a i n and na tu ra l weathering p rope r t i e s of g l a s s re inforced cement. These s tud ie s were c a r r i e d out under cont rac ts awarded t o t h e University of Southampton by t h e Building Research Establishment. Tensi le creep s t r a i n i s normally defined a s a function of t i m e . Hyperbolic, logarithmic, and exponential r e l a t ionsh ips a r e most commonly used t o descr ibe the s t r a i n versus t i m e curve. A very l a rge number of po in ts on t h e s t r a i n versus t i m e curve were recorded automatical ly f o r each of t h e samples t e s t e d , From t h i s da ta , t h e r e l a t ionsh ip most appropriate f o r g l a s s re inforced cementit ious mater ia l s i s i d e n t i f i e d s t a t i s t i c a l l y . I n addi t ion , t he r a t i o of t h e appl ied s t r e s s t o t h e shor t term u l t imate s t r e s s i s analyzed a s a function of time t o f a i l u r e when exposed t o weathering. Use of t he r e s u l t i n g r e l a t ionsh ip enables t h e ul t imate s t r e s s l e v e l f o r a design exposure period t o be determined from simple laboratory t e s t s on t h e f r e sh ly produced ma te r i a l .

2103 . Baggott, R . , and A . Sarandily, "VERY H I G H STRENGTH STEEL F I B E R REINFORCED AUTOCLAVED MORTARS," Proceedings, 3rd RILEM In t e rna t iona l Symposium on Fiber Reinforced Cement Composites, Shef f ie ld , England, J u l y 1986.

Calcium s i l i c a t e s prepared by reac t ing OPC (Ordinary Port land Cement) and s i l i c a i n t h e hydrothermal environment of an autoclave o f f e r c e r t a i n b e n e f i t s compared t o room temperature cured OPC based composites. These include g rea t e r s t rength , a more dimensional s t a b l e product w i t h respect t o moisture movement and a 2 4 hour f ab r i ca t ion cycle . The objec t ive of t h i s study was t o e s t a b l i s h improvements i n t h e s t r eng th of autoclaved mortars re inforced w i t h 1 4 % b y volume s teel f i b e r s . A novel mechanism of reinforcement was proposed f o r t he high volume f r a c t i o n composites.

3 4 4

2104. Ba laguru , P . , a n d J . Kendzulak, "FLEXURAL BEHAVIOR OF SLURRY INFILTRATED FIBER CONCRETE (SIFCON) MADE USING CONDENSED SILICA FUME," P r o c e e d i n g s of t h e second i n t e r n a t i o n a l c o n f e r e n c e on f l y a s h , s i l i c a fume, s l a g , a n d n a t u r a l p o z z o l a n s i n c o n c r e t e , p u b l i s h e d by t h e American C o n c r e t e I n s t i t u t e , SP-91, V o l . 2, Apr 1986, p p . 1215-1229.

T h i s p a p e r p r e s e n t s t h e r e s u l t s of a n e x p e r i m e n t a l i n v e s t i g a t i o n on t h e b e h a v i o r o f 60 s l u r r y i n f i l t r a t e d f i b e r c o n c r e t e (SIFCON) beams s u b j e c t e d t o s t a t i c a n d c y c l i c f l e x u r a l l o a d i n g . The object ive w a s t o s t u d y t h e i n f l u e n c e of f i b e r l e n g t h , f i b e r volume and s i l i c a fume on t h e s t r e n g t h and d u c t i l i t y of SIFCON under s t a t i c a n d c y c l i c f l e x u r a l l o a d i n g . The f i b e r s u sed w e r e s t ee l f ibers w i t h hooked e n d s . T h e f l e x u r a l s t r e n g t h o b t a i n e d w a s i n t h e o r d e r of 1 0 k s i .

2105 . Balaguru , P . N . , and V . Ramakrishnan, "FREEZE-THAW DURABILITY OF FIBER REINFORCED CONCRETE," S t r u c t u r a l J o u r n a l o f t h e American Concre t e I n s t i t u t e , Vo l . 8 2 , N o . 2, May-June 1986, p p . 374-382.

The object ive o f t h i s i n v e s t i g a t i o n w a s t o d e t e r m i n e t h e s i g n i f i c a n c e o f a i r c o n t e n t on t h e f r eeze - thaw r e s i s t a n c e of FRC and compare t h e r e s u l t s o b t a i n e d w i t h normal c o n c r e t e . A i r c o n t e n t was varied between 1 . 2 -10.8 p e r c e n t . High p e r c e n t o f a i r c o n t e n t improved t h e f r eeze - thaw d u r a b i l i t y . A s a r e s u l t , a minimum of 8% a i r c o n t e n t w a s recommended f o r c o n c r e t e s t r u c t u r e s exposed t o f r eeze - thaw c y c l e s . D u r a b i l i t y w a s improved when t h e cement c o n t e n t was i n c r e a s e d a n d t h e water t o cement r a t i o w a s d e c r e a s e d . The t o u g h n e s s i n d e x was n o t affected by t h e f r eeze - thaw c y c l e s .

2 1 0 6 . Balaguru , P . , and V . Ramakrishnan, "MECHANICAL PROPERTIES OF SUPERPLASTICIZED F I B E R REINFORCED CONCRETE DEVELOPED FOR BRIDGE DECKS AND HIGHWAY PAVEMENTS," P roceed ings , Concre t e i n T r a n s p o r t a t i o n , A C I SP 93, D e t r o i t , Michigan, Sep t 1986.

T h i s p a p e r p r e s e n t s t h e r e s u l t s o f a n e x p e r i m e n t a l i n v e s t i g a t i o n o f t h e p r o p e r t i e s o f s u p e r p l a s t i c i z e d f i b e r r e i n f o r c e d c o n c r e t e . E s s e n t i a l l y , t w o g roups of spec imens were tested; t h e f i r s t t o s t u d y t h e r e l a t i o n s h i p between t h e compressive s t r e n g t h and t h e modulus o f r u p t u r e and t h e second i s t o s t u d y t i m e dependent b e h a v i o r . A l t o g e t h e r , more t h a n 70 mix p r o p o r t i o n s were i n v e s t i g a t e d . T h e f i r s t g roup w e r e tested t o o b t a i n 2 8 day compress ive s t r e n g t h and 2 8 day modulus of r u p t u r e . T h e second g roup of specimens w e r e t es ted f o r compress ion , f l e x u r e , a n d f o r impact

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r e s i s t a n c e a t 1, 3, 7, 28, and 90 d a y s . Based on t h e e x p e r i m e n t a l r e s u l t s , an e m p i r i c a l e q u a t i o n s i m i l a r t o t h e one s p e c i f i e d i n t h e A C I Code 318-83 w a s p roposed t h a t relates t h e 28 day compress ive s t r e n g t h t o t h e 2 8 day modulus o f r u p t u r e .

2107. B a r r , B . G . , and E . D . Hasso, "FRACTURE TOUGHNESS TESTING BY MEANS OF THE SECRBB TElST SPECIMEN," I n t e r n a t i o n a l J o u r n a l of Cement Composites and L igh twe igh t Concrete, V o l . 8 , N o . 1, Feb 1986, p p . 3-9 .

The s i n g l e edge c r a c k round bar i n bend ing (SECRBB) t es t specimen i s a p r a c t i c a l tes t f o r t h e d e t e r m i n a t i o n of t h e f r a c t u r e toughness o f c o n c r e t e . The spec imens u s e d i n t h i s s t u d y were prepared from a s t a n d a r d 1 0 0 mm and 150 mm d i a m e t e r c y l i n d e r s w i t h a n o t c h d e p t h r a t i o i n t h e r a n g e of 0 . 2 < a / D < 0 . 5 . An e x p e r i m e n t a l e x p r e s s i o n w a s deve loped f o r b o t h c y l i n d e r s i z e s and hence f r a c t u r e t o u g h n e s s r e s u l t s were d e t e r m i n e d . The SECRBB t e s t geometry was used t o e v a l u a t e t h e f r a c t u r e t o u g h n e s s of a number of mixes. The e f f e c t of maximum coarse a g g r e g a t e s i z e was s t u d i e d w i t h i n c o n c l u s i v e r e s u l t s , namely, t h e f r a c t u r e toughness w a s r educed f o r a maximum a g g r e g a t e s i z e of 5 mm and 20 mm as compared t o t h e r e s u l t s o b t a i n e d u s i n g a 1 0 mm maximum a g g r e g a t e s i z e . The e f f e c t o f a d d i n g cr imped s t ee l f ibers i n t h e mix w a s a l so i n v e s t i g a t e d . The f racture t o u g h n e s s i n c r e a s e d w i t h i n c r e a s i n g f i b e r c o n t e n t b u t t h e i n c r e a s e w a s o n l y h a l f t h a t o b t a i n e d from o t h e r t e s t g e o m e t r i e s .

2108. Bonzel , J . , and M . Schmidt, "DISTRIBUTION AND ORIENTATION OF STEEL FIBERS I N CONCRETE AND THEIR INFLUENCE ON THE CHARACTERISTICS OF STEEL FIBER CONCRETE," P roceed ings , 3 r d RILEM I n t e r n a t i o n a l Symposium on F i b e r R e i n f o r c e d Cement Composi tes , S h e f f i e l d , England, 1986.

The b e a r i n g b e h a v i o r of c o n c r e t e , e s p e c i a l l y when stressed and s t r a i n e d by changing loads can be improved by t h e a d d i t i o n o f 2 % by volume o f f i b e r s . P r e v i o u s i n v e s t i g a t i o n s l e d t o t h e assumpt ion t h a t s t ee l f i b e r s have n o t a lways been d i s t r i b u t e d u n i f o r m l y i n c o n c r e t e and t h a t when d i s t r i b u t e d u n i f o r m l y t h e y are n o t o r ien ted randomly i n a l l d i r e c t i o n s . I n order t o g e t f u r t h e r i n f o r m a t i o n about a l l problems connec ted t o t h i s subjec t , e x t e n s i v e i n v e s t i g a t i o n s have been made a t t h e Research I n s t i t u t e of t h e Cement I n d u s t r y i n D u s s e l d o r f . The d i s t r i b u t i o n and o r i e n t a t i o n of t h e f ibers as w e l l a s t h e i r i n f l u e n c e on t h e d e t e r i o r a t i o n o f t h e f iber and m a t r i x p r o p e r t i e s have been s t u d i e d . A p e r f e c t i o n i n f i b e r a d d i t i o n might lead t o a un i fo rm

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d i s t r i b u t i o n of f i b e r s a s w e l l a s de t e r io ra t ion i n t he concrete mechanical proper t ies . The c h a r a c t e r i s t i c s of concrete can be improved i f f i b e r s a r e or ien ted perpendicular t o the d i r ec t ion of compressive s t r e s s e s o r p a r a l l e l t o t h e d i r ec t ion of t e n s i l e s t r e s s e s .

2109 . Cancho, A. V . , and V . Sanchez-Galvez, "A MICROMECHANICAL MODEL FOR THE TENSILE STESS-STRAIN CURVE OF F I B E R REINFORCED CEMENTS," Proceedings, 3rd RILEM In t e rna t iona l Symposium on Fiber Reinforced Cement Composites, Sheff ie ld , England, J u l y 1 9 8 6 .

Matrix microcracking i n f i b e r re inforced cements produces non l i n e a r t e n s i l e behavior t h a t inf luences some of t h e mechanical proper t ies such a s t he t e n s i l e s t r eng th and the f r ac tu re energy. This paper presents a microcracking theory of t h i s behavior. An a n a l y t i c a l expression is developed based on f r a c t u r e mechanics p r i n c i p l e s . Theoret ical expressions f o r t h e t e n s i l e s t r eng th and t h e microcracking f r a c t u r e work a r e obtained. Variables a f f ec t ing these p rope r t i e s a re taken i n t o considerat ion. They include: porosi ty , matrix f r a c t u r e res i s tance , and f i b e r content . Theoret ical r e s u l t s a r e v e r i f i e d aga ins t experimental r e s u l t s and a r e found t o be i n good agreement.

2 1 1 0 . Craig, R . J . , J . A . Parr,E. Germain,V. Mosquera, and S . Kamilares, "FIBER REINFORCED CONCRETE BEAMS I N T O R S I O N ,

Journal of t he American Concrete I n s t i t u t e , V o l . 83, N o . 6, Nov-Dec 1986, pp. 934-942.

An increasing i n t e r e s t i n t h e use of s t e e l f i b e r s t o improve t h e proper t ies of concrete led t o t h i s study of f i b e r concrete i n t o r s ion . The objec t ive of t h i s study was t o examine and record t h e behavior of f i b e r concrete i n pure to r s ion and t o provide methods f o r t o r s i o n a l behavior ana lys i s of t h e f i b e r concrete . Data w e r e drawn primari ly from e ight tes t beam specimens of var ious f i b e r content t e s t e d and compared w i t h p l a i n concrete d a t a . The da ta was a l s o used t o compare between t h e numerous combinations and percentages of s teel f i b e r s i n compression, s p l i t t i n g tension, tension, and the modulus of rupture . Additionally, t he data was used t o compare t h e o r e t i c a l ana lys i s of t h e same tes t beams w i t h respect t o t h e ul t imate torque, t o r s i o n a l s t i f f n e s s , and f r a c t u r e energy.

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2 1 1 1 . Delvasto, S . , A . E . Naaman, and J . L . Throne, "EFFECT OF PRESSURE CASTING ON H I G H STRENGTH FIBER REINFORCED MORTAR," I n t e r n a t i o n a l J o u r n a l of Cement Composite and Lightweight Concrete, V o l . 8, N o . 3, Aug 1986, pp. 181-190.

This study inves t iga t e s t h e e f f e c t s of applying pressure a f t e r cas t ing on t h e f l e x u r a l response of high s t r eng th f i b e r re inforced mortar i n which up t o 5% f i b e r s by volume were pre-mixed. High mortar s t r eng th w a s achieved by reducing porosi ty , adding f l y ash, and using supe rp la s t i c i ze r s . Variables including e igh t d i f f e r e n t types of f i b e r s , t h e i r volume f r a c t i o n i n t h e m i x , t w o mortar matrices, t w o values of pressure a f t e r cas t ing , and cas t ing o r i e n t a t i o n . Postcracking response de t e r io ra t ed due t o pressure while f l e x u r a l s t r eng th was improved. Composite modulus of rupture more t h a n 5000 p s i w a s observed with s t e e l f i b e r s . Toughness ind ices of up t o 90 were observed f o r polypropylene f i b e r s . Application of pressure a f t e r ca s t ing improves composite p rope r t i e s .

2 1 1 2 . El-Refai, F . E . , and E . H . Morsy, "SOME PROPERTIES OF FIBRE REINFORCED CONCRETE WITH SUPERPLASTICIZER," RILEM Symposium Proceedings, FRC 8 6 Developments i n Fiber Reinforced Cement and Concrete, R . N . Swamy, R . L . Wagstaffe, and D . R . Oakley , eds . , V o l . 1 & 2 , J u l y 1986.

An attempt has been made t o improve t h e workabi l i ty of FRC mater ia l s by t h e use of supe rp la s t i c i ze r s r a t h e r than increasing t h e water c o n t e n t . Variables include f i b e r c o n t e n t , supe rp la s t i c i ze r c o n t e n t , t e s t i n g methods, permeabili ty, and d u r a b i l i t y performances. T e s t s have shown a considerable improvements i n t h e c o n s i s t e n c y of t h e workabili ty of concrete . Other mechanical proper t ies were a l so improved. Such p rope r t i e s include t e n s i l e , f lexure , compressive, and impact r e s i s t ance .

2 1 1 3 . Faiyadh, F . I . , and M . A . A l - A u s i , "EFFECT OF ELEVATED TEMPRATURE AND METHOD OF RECOOLING ON THE COMPRESSIVE STRENGTH OF P L A I N AND FIBER REINFORCED CONCRETE," Proceedings, 3rd RILEM I n t e r n a t i o n a l Symposium on Fiber Reinforced Cement Composites, Shef f ie ld , England, J u l y 1986.

R e s u l t s i n t h i s paper show the va r i a t ion i n t he compressive s t rength of p l a i n and f i b e r re inforced concrete cubes when exposed t o e levated temperature. The cubes were reinforced w i t h 0 . 5 , 0 . 7 , and 1 . 0 percent by volume of s tee l hooked and g l a s s f i b e r s . The

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cubes were exposed t o temperature ranging between 20-800 degrees C f o r a period of 90 m i n u t e s . They were t e s t e d while they were hot, cooled i n a i r , and cooled i n water. Results showed t h e de t e r io ra t ion i n t h e compressive s t rength w i t h temperature f o r both p l a i n and f i b e r re inforced concrete. A t temperatures below 350 degrees C, f i b e r re inforced concrete cubers showed b e t t e r performance than p l a in concrete. A t temperatures higher than 100 and 350 degrees C, t he va r i a t ion i n t he f i b e r content had secondary e f f e c t s on the r e s idua l compressive s t r eng th . Recooling t h e specimens i n water caused f u r t h e r reduction i n t h e compressive s t r eng th .

2 1 1 4 . Gopalaratnam, V . S . , and S . P . Shah, "MICROMEHANICAL MODEL FOR THE TENSILE FRACTURE OF STEEL F I B E R REINFORCED CONCRETE," Proceedings, 3rd RILEM In t e rna t iona l Symposium on Fiber Reinforced Cement Composites, Shef f ie ld , England, J u l y 1 9 8 6 .

Observations from an experimental study on the t e n s i l e f r a c t u r e of s t e e l f i b e r re inforced concrete (SFRC) composites a re b r i e f l y summarized. Based on these observations, c h a r a c t e r i s t i c s des i red i n a n a l y t i c a l models f o r t h e f r ac tu re of SFRC a r e i d e n t i f i e d . Assumptions made i n a few cu r ren t ly used models a r e reviewed and evaluated, i n l i g h t of t h e des i red c h a r a c t e r i s t i c s . A micromechanical model f o r t h e idea l ized SFRC composite i s presented. T h i s model takes i n t o account t he two primary non-linear aspects of t h e f a i l u r e mechanism, namely: t h e i n e l a s t i c behavior of t he fiber-matrix i n t e r f a c e and t h e sof tening c h a r a c t e r i s t i c s of t h e unreinforced matr ix . The model i s a l s o observed t o be r e a l i s t i c a l l y s e n s i t i v e t o the reinforcement parameters such a s t h e f i b e r volume content, aspect r a t i o , and t h e e l a s t i c proper t ies of t h e f i b e r s .

2 1 1 5 . Kagan, M . Z . , "COMPARISON OF THE TENSILE STRENGTH O F CONCRETE AND STEEL-FIBER CONCRETE I N BLOCKS OF A TUNNEL

O c t 1986, pp. 589-591. L I N I N G , " Hydrotechnical Construction, V o l . 20 , No. 1 0 ,

C i rcu lar tunnel l i n i n g has a wide use i n t h e construct ion of subway tunnels and other underground s t r u c t u r e s . Reinforced concrete serves a s t he mater ia l f o r it and only under complex hydrogeological conditions i s it made of cas t i ron . The use of s t e e l f i b e r s was found t o solve t h e problem of s o i l impermeability under conditions of water s a t u r a t i o n . Steel f i b e r s a r e known f o r t h e i r higher crack r e s i s t ance indices than concrete due t o the increased values of t e n s i l e s t rength . An index defined a s the

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cleavage t e n s i l e s t rength was the subject of t h i s i nves t iga t ion .

2 1 1 6 . K e e r , J. G., and D . J. Hannant, "THE PREDICTION OF THE

COMPOSITE," RILEM Symposium Proceedings, FRC 86 Developments i n Fiber Reinforced Cement and Concrete, R . N . Swamy, R . L . Wagstaffe, and D . R . Oakley, eds . ,

LOAD-DEFLECTION BEHAVIOUR OF A F I B E R REINFORCED CEMENT

1986, pp. 1 - 6 .

For b r i t t l e FRC composites, t h e de f l ec t ion behavior i s not c r i t i c a l s ince an ul t imate f a i l u r e load i s a t t a i n e d a t low de f l ec t ions . However, t h e de f l ec t ions may become s i g n i f i c a n t as t h e ul t imate load i s approached and may i n p rac t i ce present s e r v i c e a b i l i t y problems. T h i s i s e spec ia l ly t r u e f o r pseudoductile FRC composites. A load-deflection r e l a t ionsh ip may be obtained from t h e d i r e c t tension and compression s t r e s s - s t r a i n r e l a t ionsh ips using simple bending theory and t r e a t i n g t h e cracked composite e s s e n t i a l l y a s a continuum. T h i s approach does no give s a t i s f a c t o r y agreement w i t h t h e experimental behavior. A new approach i s proposed which i s dependent on t h e behavior of a crack i n f l exura l members r a t h e r than t h e use of d i r e c t t e n s i l e s t r e s s - s t r a i n r e l a t ionsh ips . A moment-rotation r e l a t ionsh ip i s obtained f o r a cracked zone and a method i s suggested whereby t h e p a t t e r n of development of cracks can be pos tu la ted as t h e load i s increased. The use of t he crack development i n conjunct ion w i t h t h e moment-rotation character is t ics allows t h e pred ic t ion of t h e load-deflection behavior of t h e composite mater ia l f o r a p a r t i c u l a r loading regime. A s a t i s f a c t o r y co r re l a t ion i s found between t h e t h e o r e t i c a l and experimental load de f l ec t ion curves f o r polyolef in-reinforced cement composites.

2 1 1 7 . Komlos, K . , "LONG TERM SFRC STRENGTH, '' Proceedings, 3rd RILEM In t e rna t iona l Symposium on Fiber Reinforced C e m e n t Composites, Shef f ie ld , England, J u l y 1 9 8 6 .

The aim of t h i s paper i s t o provide information about t h e development of t h e s t rength c h a r a c t e r i s t i c s of SFRC w i t h i n t h e age of 360 days. A grade OPC 400 w a s used throughout t h i s experiment. S t r a igh t square s t e e l f i b e r s w i t h a diameter ranging between 0.018-0.025 inch and a length = 1.38" was used. The s t r eng th of t h e specimens kept on increasing u n t i l t h e age of 1 4 days and remained steady beyond t h a t da t e . T h i s implies t h a t t h e bond s t r eng th keeps on increasing up t o t h e mentioned da te and s t a b i l i z e s l a t e r on.

3 5 0

2118. Kormeling, H . A . , "SFRC I N UNIAXIAL IMPACT TENSILE LOADING AT 20 DEGREES C AND AT -170 DEGREES C , " Proceedings, 3rd RILEM In te rna t iona l Symposium on Fiber Reinforced Cement Composites, She f f i e ld , England, 1 9 8 6 .

T h i s paper presents t h e r e s u l t s of un iax ia l s t a t i c and impact t e n s i l e t e s t s performed on dr ied p l a i n and on 1 . 5 % s t r a i g h t s t e e l f i b e r re inforced concrete, both a t 20 degrees. C and a t -170 degrees. C . T h e low r a t e equipment (hydraul ic) and t h e h igh r a t e equipment ( S p l i t Hopkinson Bar) w i t h temperature cont ro l led t e s t chambers a r e b r i e f l y described. Loads and displacements were measured w i t h conventional devices. Experimental resu l t s a r e presented i n t h e form of stress-deformation curves. For low s t r a i n loading, they show an increase i n t h e s t rength , f r a c t u r e deformation and energy absorption a t lower temperatures. Fibers cause a s h i f t t o higher values than those obtained f o r p l a i n concrete . A t low temperatures, a deviat ion from t h i s behavior occurs f o r high s t r a i n loading. I n c e r t a i n cases, a small decrease i n the s t rength and deformation values i s observed.

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2 1 1 9 . L i , V . C . , and E . Liang, "FRACTURE PROCESSES I N CONCRETE AND F I B R E REINFORCED CEMENTITIOUS COMPOSITES," Journal of Engineering Mechanics, ASCE, Vol. 112, No. 6, June 1986, pp. 566-586.

T h i s paper discusses the f r a c t u r e processes of concrete and f i b e r re inforced composites w i t h spec ia l focus on t h e development of t he f r a c t u r e process zone w i t h respect t o the s t ress -separa t ion c o n s t i t u t i v e r e l a t ionsh ips of such mater ia l s . The suggestion i s t h a t t h e o v e r a l l mechanical behavior of concrete o r FRC s t r u c t u r e s could be s t rongly influenced by t h e s t ress -separa t ion cons t i t u t ive r e l a t ionsh ips , which i n t u r n can be a l t e r e d by engineering the microstructure of t h e mater ia l , espec ia l ly i n F R C . The process zone length i s found not t o be a mater ia l property, but depends on the geometry of t h e specimen and t h e loading configurat ions. A l l these r e s u l t s a r e shown e x p l i c i t l y by a simple numerical model of a center-crack panel subjected t o remote edge loading or t o wedge loading on t h e crack f aces . These ca lcu la t ions a l s o provide f u r t h e r understanding t o t h e v a l i d i t y of c e r t a i n f a i l u r e c r i t e r i a .

2 1 2 0 . Lub, K . B . , and M . S . Mathewst, "INFLUENCE OF STEEL F I B E R S ON THE BEHAVIOR OF CONVENTIONALLY REINFORCED THIN-WALLED HOLLOW BEAMS," The In t e rna t iona l Journal of Cement Composites and L i g h t w e i g h t Concrete, Vol. 11, No. 1, Feb 1986, pp. 47-55.

The aim of t h i s inves t iga t ion was t o s t u d y the inf luence of adding a spec ia l type of s t e e l f i b e r s (Thibo) t o conventionally re inforced thin-walled beams. To compare t h e influence of t h e f i b e r s , two i d e n t i c a l beams were a l s o cas t without f i b e r s , and f i v e were cas t and t e s t e d t o des t ruc t ion . T h e ob jec t ive of t h e inves t iga t ion was t o study t h e inf luence of a l ign ing the f i b e r s i n 1 - D and 2-D under appl ied shear and f l e x u r a l s t r e s s e s . Results showed t h a t t h e inclusion of f i b e r s increases the shear b u t not t he f l e x u r a l s t r eng th . The s t i f f n e s s and d u c t i l i t y of t h e beams were a l s o increased and w e r e dependant on t h e shear span r a t i o .

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2 1 2 1 . Mbaezue, J . I . , and R . M . Madu, "FLEXURAL CREEP OF POLYPROPYLENE F I B R E REINFORCED CONCRETE LAMINATE AS A MEASURE OF D U R A B I L I T Y , " RILEM Symposium Proceedings, FRC 86 Developments i n Fiber Reinforced Cement and Concrete, R . N . Swamy, R . L . Wagstaffe, and D . R . Oakley, eds . , 1 9 8 6 .

I n t h i s paper, an empirical equation i s obtained t o p red ic t t h e f l exura l creep of polypropylene f i b r e re inforced concrete laminate, making u s e of rheological and experimental r e s u l t s . The v a l i d i t y of t h e proposed model i s t e s t e d against predicted s t ra in- t ime curves and experimental da t a . The type of rheological model used i s determined by making some preliminary assumptions and considering t h e laminate a s a two dimensional composite of matrix re inforced by a regular a r r ay of s imi l a r f i b e r s and loaded f l exura l ly i n tension i n a d i r ec t ion p a r a l l e l t o t he f i b e r d i r e c t i o n . By applying bas ic equations governing motion and neglect ing body forces , an equation i s obtained ind ica t ing the type of rheological model t o be appl ied . T h i s model when analyzed gives a creep response equation whose constants a r e determined experimentally. The experiment involves the appl ica t ion of t e n s i l e loads by f l e x u r a l methods on t h e laminate and observation of creep def lec t ion over a long per iod . U s i n g n u m e r i c a l methods, the ensuing r e s u l t i s an empirical equation predic t ing creep.

2 1 2 2 . Meyer, A . , "COMPOSITION AND PROPERTIES OF THE F I B E R CONCRETE MATRIX [ZUSAMMENSETZUNG UND EIGENSCHAFTEN DER FASERBETON-MATRIX] , Betonwerk und Fert igtei l -Technik, V o l . 52, No. 1, Jan 1986 , pp. 52-58.

The cementitious matrix i s an e s s e n t i a l p a r t of f i b e r concrete and s i g n i f i c a n t l y influences i t s p rope r t i e s i n t h e f r e sh a s w e l l as i n t h e hardened s t a t e . Micro-concrete produced according t o t h e ru l e s of concrete technology has grea t technological advantages compared t o a matrix of cement pas te without aggregate. When formulating mixes, a s u f f i c i e n t degree of workabili ty i s a s important a s t he des i red p rope r t i e s of t h e hardened micro-concrete. The technica l proper t ies of micro-concrete can be adjusted w i t h i n a c e r t a i n range by the se l ec t ion of bas i c mater ia l s , t h e composition of t he mix and the conditions of t h e hardening process. The majority of t h e r e g u l a r i t i e s known from the concrete a l s o apply t o micro-concrete. A number of addi t ives and admixtures have proved t o influence c e r t a i n proper t ies of t he micro-concrete. The composition of t h e matrix i s determined by the f i b e r s used, t h e manufacturing

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process, t h e d imens ions o f t h e f iber c o n c r e t e e l e m e n t s and t h e load t o which t h e y are s u b j e c t e d .

2 1 2 3 . Nakagawa, T . , K . Suzuki , and A. Yanagisawa, "PRODUCTION OF STEEL F I B R E BY MACHINING PROCESS FOR SFRC," P r o c e e d i n g s , 3rd RILEM I n t e r n a t i o n a l Symposium on F iber R e i n f o r c e d Cement Composi tes , S h e f f i e l d , England, J u l y 1986.

Most of t h e f i b e r s fo r r e i n f o r c i n g cements and c o n c r e t e s have been manufac tu red by c u t t i n g o r s h e a r i n g process from s teel wire o r s t ee l s h e e t . The a u t h o r s have newly deve loped t h e f o l l o w i n g t w o t y p e s o f p r o d u c t i o n methods of s t e e l f ib re by machin ing p r o c e s s : (1) M i l l i n g method, where a s t ee l block i s machined w i t h a p l a i n m i l l i n g c u t t e r a n d t h e n e e d l e shaped chips become t h e f i b e r s . T h i s f iber w a s con f i rmed t o have an e x c e l l e n t r e i n f o r c i n g effect i n t h e c o n c r e t e . The s p e c i a l l y d e s i g n e d m i l l i n g machine f o r t h e e f f i c i e n t mass p r o d u c t i o n of steel f ibers was deve loped a n d it has been u s e d f o r a c t u a l p r o d u c t i o n i n Japan and West Germany. ( 2 ) Chat te r Machine Method: a round r o d i s machined b y a c h a t t e r i n g e l a s t i c c u t t i n g t o o l on a la the and t h e n e e d l e shaped ch ips become t h e f ibe r s . T h e f ibers made u s i n g t h i s process are s u i t a b l e f o r r e i n f o r c i n g cement mortar. The e x c l u s i v e e las t ic c u t t i n g t o o l i s ready for t h e a c t u a l p r o d u c t i o n . I t i s conc luded t h a t new manufac tu r ing processes of s tee l f i b e r s b y machin ing ( i . e . , t h e M i l l i n g method and Chat ter Machining Method) p roduce s t ee l f ibers w i t h s u f f i c i e n t q u a l i t y t o be u s e d i n c o n c r e t e . F r o m compar ison w i t h o t h e r e x i s t i n g s teel f ibers , these machined f ibers are s u p e r i o r i n q u a l i t y and i n c o s t . The machined f ibe r s manufac tu red by t h e above two methods have now been offered t o t h e u s e r s f rom s e v e r a l companies . The a u t h o r s believe t h a t t h e q u a l i t y of machined f ibers have t h e p o t e n t i a l t o be improved i n t h e f u t u r e .

2 1 2 4 . Nammur, G . G . , and A. E . Naaman, "STRAIN RATE EFFECTS ON TENSILE PROPERTIES OF FIBER REINFORCED CONCRETE," P r o c e e d i n g s , MRS Symposium on Cement Based Composi tes : S t r a i n Rate Ef fec t s on F r a c t u r e , S . Mindess, Ed i to r , Materials Research S o c i e t y , V o l . 64, 1986, pp. 97-118.

High s t r a i n ra tes lead t o a s u b s t a n t i a l m o d i f i c a t i o n s i n t h e s t r a i n rates ( o r s t r e s s - d i s p l a c e m e n t ) r e s p o n s e o f FRC i n t e n s i o n . These m o d i f i c a t i o n s i n c l u d e h ighe r s t r e n g t h a n d c o r r e s p o n d i n g s t r a i n , as w e l l as smaller d i s p l a c e m e n t a t f a i l u r e . The p u r p o s e of t h i s p a p e r i s t o i n v e s t i g a t e t he b e h a v i o r of FRC unde r impact t e n s i l e l o a d i n g , and t o s t u d y t h e

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e f f e c t of s t r a i n r a t e on post-cracking s t rength of t he composite. The va r i a t ion of t h e t ens i l e s t r eng th of t he matrix with t h e reinforcement parameters such a s t h e volume f r a c t i o n and t h e aspect r a t i o of t h e f i b e r s i s a l s o s tud ied i n t h i s paper. A spec ia l emphasis i s placed on t h e stress-displacement r e l a t ionsh ip a s a funct ion of t h e s t r a i n r a t e , where such a r e l a t ionsh ip i s developed from experimental da ta using t e n s i l e t e s t s on dogbone shape notched t e n s i l e prisms. The model h ighl ights t h e e f f e c t s of s t r a i n r a t e on t h e post-cracking toughness of t h e composite, a s w e l l a s t h e displacement a t f a i l u r e . The e f f e c t of s t r a i n r a t e on t h e post-cracking toughness of FRC i s a l s o addressed. The l i t e r a t u r e on impact e f f e c t s on concrete i n t ens ion (p l a in and f i b e r re inforced) i s b r i e f l y reviewed i n t h i s paper, and so i s t h e s t a t e of t he a r t t e s t i n g techniques of s t r a i n r a t e e f f e c t s .

2 1 2 5 . Narayanan, R . , and A . S . Kareem-Palanjian, "TORSION, BENDING, AND SHEAR I N PRESTRESSED CONCRETE BEAMS CONTAINING STEEL FIBERS," Journal of t h e American Concrete I n s t i t u t e , Vol. 83, No. 3, May-Jun 1986, pp. 423-431.

T e s t r e s u l t s of 27 p res t ressed beams containing s teel f ibers and subjected t o combined bending, t o r s ion , and shear were reported. The f i b e r content and t h e type of loading were var ied. No reduction i n t h e t o r s i o n a l capaci ty was detected even when t h e bending moment was s u b s t a n t i a l l y increased. In t e rac t ion curves were proposed which adequately give conservative values of t h e ul t imate capacity of pres t ressed f i b e r concrete beams under combined bending and t o r s i o n .

2 1 2 6 . Narayanan, R . , and A . S . Kareem-Palanjian, "TORSION I N BEAMS REINFORCED WITH BARS AND F I B E R S , " Journal of S t r u c t u r a l Engineering, V o l . 1 1 2 , No. 1, Jan 1986, pp. 53-66.

An experimental inves t iga t ion was ca r r i ed out t o assess t h e e f f e c t of incorporating s teel f i b e r s on the t o r s i o n a l behavior of conventionally re inforced beams i s reported. The study involved t e s t i n g 24 beams, w i t h p a r t i a l o r f u l l replacement of longi tudina l s t e e l reinforcement and/or s t i r r u p s by an equivalent volume f r a c t i o n of s t e e l f i b e r s . The t e s t s revealed t h a t t h e loads on f i r s t cracking observed on f i b e r re inforced beams were subs t an t i a l ly higher than those obtained i n s imi l a r beams w i t h conventional reinforcement. Increase of approximately 60% i n t he t o r s i o n a l capaci ty of t h e beams were observed, when t h e s t i r r u p s where p a r t i a l l y

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o r f u l l y replaced by an equivalent volume f r a c t i o n of f i b e r s .

2 1 2 7 . Narayanan, R . , and A . S . Palanjia:n, "FACTORS I N F L U E N C I N G THE STRENGTH OF STEEL FIBER REINFORCED CONCRETE," Proceedings, 3rd RILEM In t e rna t iona l Symposium on Fiber Reinforced Cement Composites, Shef f i e l d , England, J u l y 198 6 .

A method of comparative assessment of bond characterist ics of various types of s teel f i b e r s i s proposed i n terms of a non-dimensional bond e f f i c i ency f a c t o r (bond f a c t o r ) . The d e f i n i t i o n i s considered t o be a measure of t h e r e l a t i v e resistance of t h e f i b e r t o be pul led o u t from t h e m a t r i x . A l a rge number of pu l lout t e s t s w a s c a r r i ed o u t i n order t o obta in t h e da ta on Bond Factors . Concrete design s t r eng ths ranged between 25 t o 60 N/mrn2. Several parameters were considered: f i b e r type, length, and embedment length, and t h e s t rength of t h e m a t r i x . Such parameters a f f ec t ed t h e pul lout load. Safe values of Bond Factors were proposed based on t h e type of f i b e r used.

2128. Ohama, Y . , and M . Endo, "PROPERTIES OF HYBRID F I B R E REINFORCED POLYMER-MODIFIED CONCRETE," RILEM Symposium Proceedings, FRC 8 6 Developments i n Fiber Reinforced C e m e n t and Concrete, R . N . Swamy, R . L . Wagstaffe, and D . R . Oakley , eds . , Vol. 1 C 2 , 1986.

This paper dea ls with t h e p rope r t i e s of hybrid s t e e l f i b e r and polyethylene f i b e r re inforced polymer modified concrete ( H F R P C C ) . HFRPCC using a styrene-butadiene rubber l a t e x i s prepared w i t h various polyethylene f i b e r c o n t e n t s and polymer cement r a t i o s and a constant s teel f i b e r c o n t e n t of 1 % by volume. Flexural and compressive tes ts were c a r r i e d o u t . The f l e x u r a l toughness of t h e HFRPCC w a s remarkably improved w i t h a n increase i n polyethylene f i b e r c o n t e n t . Po lymer l a t e x modification improved t h e compressive s t rength of HFRPCC while polyethylene f i b e r reinforcement modification had l i t t l e e f f e c t .

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2129. O t t e r , D . , and A . E . Naaman, "STEEL FIBER REINFORCED CONCRETE UNDER STATIC AND CYCLIC COMPRESSIVE LOADING," P r o c e e d i n g s o f T h i r d I n t e r n a t i o n a l Symposium on Developments i n Fiber R e i n f o r c e d Cement and Concre t e , Edi ted by R . N . Swamy, R . L . Wags taf fe , and D . R . Oakley, Shef f i e l d , England, J u l y 1986.

A s t u d y o f t h e s t r e s s - s t r a i n r e l a t i o n s h i p of f i b e r r e i n f o r c e d c o n c r e t e unde r s t a t i c and c y c l i c compress ive l o a d i n g w a s conduc ted . D i f f e r e n t c o n c r e t e s t r e n g t h s , and d i f f e r e n t t y p e s , volume f r a c t i o n s , and aspect r a t io s of f i b e r s w e r e u s e d . Three s t r a i n ra tes f o r t h e c y c l i c l o a d i n g t e s t s s p a n n i n g from 1 0 % t o 90% of t h e s t r e n g t h observed i n t h e c o r r e s p o n d i n g monotonic t es t s were a p p l i e d . I n s t r u m e n t a t i o n i s d i s c u s s e d i n d e t a i l . R e s u l t s i n c l u d e d t h e i n f l u e n c e o f t h e f i b e r r e i n f o r c i n g parameters on t h e monotonic compress ive tests, t h e c y c l i c s t r e s s - s t r a i n c h a r a c t e r i s t i c s , a n d t h e number of c y c l e s t o f a i l u r e .

2130. Robins , P . J . , a n d S . A . Aus t in , "MELT EXTRACT FIBER- A NEW IMPETUS FOR STEEL FIBER SPRAYED CONCRETE," P r o c e e d i n g s , 3rd RILEM I n t e r n a t i o n a l Symposium on F i b e r R e i n f o r c e d Cement Composi tes , S h e f f i e l d , England, J u l y 1986.

I n t h e m i d - s e v e n t i e s , t h e B a t t e l l e Development C o r p o r a t i o n i n t r o d u c e d a new steel f i b e r produced by t h e m e l t e x t r a c t i o n process. The improved h a n d l i n g c h a r a c t e r i s t i c s , l o n g t e r m d u r a b i l i t y , and s u p e r i o r bond b e h a v i o r o f t h i s new f i b e r offered a p o t e n t i a l s o l u t i o n t o t h e mixing, h i g h rebound and p o s s i b l e c o r r o s i o n problems commonly associated w i t h t h e u s e of ca rbon s t ee l drawn w i r e and s l i t s h e e t f i b e r s . T h i s p a p e r h i g h l i g h t s t h e r e s u l t s of a series of i nves t iga t ions carried o u t t o evaluate and compare t h e p r o d u c t i o n and per formance of s p r a y e d c o n c r e t e c o n t a i n i n g m e l t e x t r a c t f ibers, drawn w i r e f ibers , and mesh r e i n f o r c e m e n t . Emphasis was placed on measu r ing t h e f l e x u r a l s t r e n g t h and toughness , as w e l l as on t h e f iber t y p e and c o n t e n t . The a d v a n t a g e s of u s i n g t h i s new c o n s t r u c t i o n material are d i s c u s s e d i n r e l a t i o n t o recent c o n s t r u c t i o n a p p l i c a t i o n s .

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2131. Rotondo, P . L . , and K . H . Wiener, "ALIGNED STEEL FIBERS I N CONCRETE POLES," C o n c r e t e I n t e r n a t i o n a l : Des ign and C o n s t r u c t i o n , Vol . 8, N o . 12, Dec 1986, pp. 22-27.

I n 1973, N o r t h e a s t U t i l i t i e s i n i t i a t e d a n i n v e s t i g a t i o n t o d e t e r m i n e s u i t a b l e a l t e r n a t i v e s f o r wooden e lec t r ic d i s t r i b u t i o n poles. A m a n u f a c t u r i n g method was devised t o p roduce c e n t r i f u g a l l y cast f i b e r c o n c r e t e p o l e s t h a t c o n t a i n a x i a l l y a l i g n e d s tee l f i b e r s as p r i m a r y r e i n f o r c e m e n t . Computer c o n t r o l l e d machines are now p roduc ing t h e s e poles fo r t h e s o u t h e a s t e r n U . S . and A u s t r a l i a . T h i s i s one of t h e f i rs t a p p l i c a t i o n s of s t ee l f ibe r r e i n f o r c e d c o n c r e t e i n h i g h l y stressed precast p r o d u c t s .

2132. S a k a i , M . , and N . Nakamura, "ANALYSIS OF FLEXURAL BEHAVIOUR OF STEEL FIBER REINFORCED CONCRETE," P r o c e e d i n g s , 3rd RILEM I n t e r n a t i o n a l Symposium on F i b e r R e i n f o r c e d Cement Composi tes , S h e f f i e l d , England, 1 9 8 6 .

I n order t o e v a l u a t e t h e f l e x u r a l t o u g h n e s s and d u c t i l i t y o f s tee l f i b e r r e i n f o r c e d c o n c r e t e (SFRC), t h e a u t h o r s conduc ted some s t u d i e s on t h e a n a l y s i s methods f o r t h e f l e x u r a l b e h a v i o r o f SFRC i n which t h e s h a p e and p r o p e r t i e s of s teel f i b e r s were e v a l u a t e d a f t e r c r a c k i n g o f t h e m a t r i x . The method w a s based on e v a l u a t i n g t h e mechan ica l c h a r a c t e r i s t i c s of s t ee l f ibers a n d p r o p e r t i e s of t h e m a t r i x and t h e n t o d e t e r m i n e t h e s t r e s s - s t r a i n r e l a t i o n s h i p o f SFRC. Beam t h e o r y was used i n t h e f l e x u r a l a n a l y s i s . The resul ts w e r e compared t o 1 6 cases o f e x p e r i m e n t s conduc ted w i t h d i f f e r e n t i n f l u e n c e f a c t o r s .

2133. S c h n e i d e r , B . , "STRUCTURAL APPLICATIONS OF SIFCON," P r o c e e d i n g s , A p p l i c a t i o n and Per formance o f S t r u c t u r a l Materials and E x t e r i o r Facades , ASCE, N e w York, NY, Oct 1986, pp. 1-15.

SIFCON ( S l u r r y I n f i l t r a t e d F i b e r C O N c r e t e ) i s a r e l a t i v e l y new composite material u t i l i z i n g s t ee l f i b e r r e i n f o r c e d c o n c r e t e i n a cement based m a t r i x . The mix ing p r o c e s s s tar ts w i t h a bed of p r e p l a c e d s t e e l f i b e r s i n t h e r ange of 5 t o 20 p e r c e n t by volume. The f iber bed i s t h e n i n f i l t r a t e d w i t h a l o w v i s c o s i t y c e m e n t i t i o u s s l u r r y . The r e s u l t i n g compos i t e mater ia l possesses a very h i g h compress ive s t r e n g t h as w e l l as d u c t i l i t y . SIFCON h a s the p o t e n t i a l f o r many a p p l i c a t i o n s i n t h e b u i l d i n g i n d u s t r y .

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2134. Sellevold, E . J . , S . M . Moell, and T . D a n i e l s s e n , "USE

REINFORCED CEMENTS," RILEM Symposium Proceedings, FRC 86 Developments i n Fiber Reinforced Cement and Concrete, R . N . Swamy, R . L . Wagstaffe, and D . R . Oakley, eds . , V o l . 1 & 2, J u l y 1986.

OF MICROSILICA ADDITIVES I N ASBESTOS FREE F I B R E

The u s e of micros i l ica o r benef ic ia ted condensed s i l i c a fume, i n FRC products is discussed and some new da ta are presented. Tests performed on microsi l ica cement based samples show t h a t f o r samples cured a t moderately elevated temperatures, t h e addi t ion of microsil ica s i g n i f i c a n t l y increases t h e f l e x u r a l s t r eng th . For room temperature cured samples, t h e f l e x u r a l s t rength w a s no t improved. R e s u l t s showed t h a t micros i l ica has an improved modifying e f f e c t on t h e pore s t r u c t u r e , and t h a t i t s pozzolainc a c t i v i t y i s high. Comparison of FRC and concrete mater ia ls i s presented. The Hatschek process i s discussed from t h e view point of using microsil ica add i t ives . A number of d i f f i c u l t i e s and questions w i t h regard t o mixing order , dispers ion, and f i l t r a t i o n are noted.

2135. Sharma, A . K., "SHEAR STRENGTH OF STEEL FIBER REINFORCED CONCRETE BEAMS," J o u r n a l of t h e American Concrete I n s t i t u t e , Vol. 83, No. 4 , July-Aug 1 9 8 6 , pp. 624-628.

Experimental work was ca r r i ed out t o compare seven norma l ly re inforced and f i b e r re inforced concrete beams subjected t o combined shear and bending. An empirical r e l a t ionsh ip f o r t h e predict ion of t h e shear s t rength of FRC beams was a r r ived a t . A l l beams were designed s o as t o f a i l i n shear . The beams were divided i n t o t w o groups: group S (no s t i r r u p s ) and group D ( w i t h s t i r r u p s ) . A l l beams w e r e rectangular i n cross sec t ion . S t e e l f i b e r s increased the shear capacity and t h e post-cracking s t r eng th . Uniform cracking was achieved due t o f i b e r addi t ion .

2 1 3 6 . Stebbins, R . J . , C . W . Josifek, and J . D . Jeniec, "EPOXY-BONDED, STEEL FIBER-REINFORCED T H I N CEMENTITIOUS OVERLAY AT ORLANDO INTERNATIONAL JETPORT, FLORIDA," Proceedings, 3rd RILEM I n t e r n a t i o n a l Symposium on Fiber Reinforced Cement Composites, Shef f ie ld , England, J u l y 1986.

The reasons f o r s e l ec t ing an epoxy-bonded, s t e e l f i b e r re inforced, cement/fly ash, superp las t ic ized overlay are discussed. The pro jec t f i e l d appl ica t ion procedure from e x i s t i n g concrete preparat ion t o pro jec t completion i s a l s o discussed. A t o t a l of 40000 sq. f t .

359

was a p p l i e d from 1 . 5 i n . t o 3 i n . t h i c k w i t h no s i g n s o f d e l a m i n a t i o n o r v i s i b l e c r a c k i n g e v i d e n t a f t e r t e s t i n g a t 90 d a y s m a t u r i t y . T o date, t h i s i s t h e largest project of i t s t y p e i n t h e s t a t e of F l o r i d a .

2137 . Sundara Raja I y e n g a r , K . T . , T . S . Naga ra j , and B . K . R a o , 'tSUPERPLASTICISED NATURAL RUBBER LATEX MODIFIED STEEL FIBRE REINFORCED CONCRETES," RILEM Symposium P r o c e e d i n g s , FRC 86 Developments i n F i b e r Reinforced Cement and Concrete, R . N . Swamy, R . L . Wags ta f f e , and D . R . Oakley, eds . , V o l . 1 & 2, J u l y 1986.

N a t u r a l rubber l a t e x concrete w i t h s u p e r p l a s t i c i z e r i s introduced as a new m a t r i x i n s teel f i b e r r e i n f o r c e d concrete (SFRC). Optimum dosage of l a t e x and s u p e r p l a s t i c i z e r h a s been used. Two d i f f e r e n t p e r c e n t a g e s o f s t e e l f ibers are i n t r o d u c e d . S t r e n g t h of t h e composite material under direct t e n s i o n and compress ion h a s been s tud ied . The load d e f l e c t i o n unde r f l e x u r a l and impact resistance have been determined and t h e s t r a i n r a t e c o n t r o l l e d machine have been u s e d i n t h i s e x p e r i m e n t a l s t u d y . The d e f o r m a t i o n c h a r a c t e r i s t i c s o f FRC were improved w i t h t h e a d d i t i o n of t h e new l a t e x mater ia l . I t i s concluded t h a t s u p e r p l a s t i c i z e d N a t u r a l Rubber L a t e x Modi f i ed SFRC e x h i b i t s h i g h e r d u c t i l i t y / e n e r g y a b s o r p t i o n ( t o u g h n e s s ) t h a n p l a i n concrete, and t h a t t h e new mater ia l h a s bet ter s y n e r g i s t i c e f f e c t s t h a n o r d i n a r y SFRC due t o t h e p r e s e n c e of r u b b e r i n t h e c o n c r e t e m a t r i x .

2138. Uyan, M . , Y . Atan , and M . A l i - T a s d e m i r , "BEHAVIOR OF GFRC MORTARS UNDER U N I - AND B I - AXIAL LOADING," P r o c e e d i n g s , 3rd RILEM I n t e r n a t i o n a l Symposium on F i b e r Reinforced Cement Composi tes , S h e f f i e l d , England, J u l y 1986.

I n t h i s e x p e r i m e n t a l i n v e s t i g a t i o n , t h e e f f e c t of f i b e r c o n t e n t and f i b e r l e n g t h on t h e s h o r t t e r m b e h a v i o r o f GFRC m o r t a r unde r u n i a x i a l a n d b i a x i a l l o a d i n g w a s i n v e s t i g a t e d . The GFRC w a s c o n s i d e r e d as a composite material and t h e s i m p l e m i x t u r e r u l e w a s applied t o it. Al though t h e compressive s t r e n g t h a n d t h e modulus o f e l a s t i c i t y decreased when glass f ibers were added, t h e r e w a s a considerable increase i n t h e f l e x u r a l s t r e n g t h , i n t h e compressive s t r a i n s , and i n t o u g h n e s s and impact s t r e n g t h s .

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2139. W e i , S . , J . A . Mandel, and S. Said, "STUDY OF THE INTERFACE STRENGTH I N STEEL FIBER-REINFORCED CEMENT-BASED COMPOSITES," Journal of t h e American Concrete I n s t i t u t e , Vol. 83, No. 4 , July-Aug 1 9 8 6 , pp. 597-605.

The p rope r t i e s of f iber-reinforced cement-based composite mater ia l s a r e dependent on t h e c h a r a c t e r i s t i c s of t h e f i b e r , t he matrix, and t h e fiber-matrix i n t e r f a c e . I n general , t h e nature and the behavior of t he matrix and t h e f i b e r a r e reasonably w e l l understood, b u t those of t he i n t e r f a c e a r e known i n considerably l e s s d e t a i l . This inves t iga t ion demonstrates t h a t t h e addi t ion of a c r y l i c polymer t o f i b e r re inforced mortar strengthens t h e matrix and improves t h e bond. Tensi le tests, f i b e r pul lout t e s t s , microhardness s tud ies , and e lec t ron microscopy s tud ie s w e r e conducted on mortar w i t h and without a c r y l i c polymer. The t e n s i l e s t rength, t h e i n t e r f a c i a l bond, and t h e energy required f o r f i b e r debonding was increased by a f a c t o r of 4 w i t h t h e addi t ion of 15% a c r y l i c polymer by weight of cement . Microhardness and t h e microstructure of an annular region of t h e composite surrounding a f i b e r were inves t iga ted t o explain the r e s u l t s .

2 1 4 0 . Zollo, F . , and G . B . Bouchacourt, "PLASTIC AND D R Y I N G SHRINKAGE I N CONCRETE CONTAINING COLLATED F I B R I L L A T E D POLYPROPYLENE F I B E R , " Proceedings, 3rd RILEM In t e rna t iona l Symposium on Fiber Reinforced Cement Composites, Sheff ie ld , England, 1986.

R e s u l t s of e a r l i e r s tud ies have indicated t h a t t h e addi t ion of low volumes of f i b r i l l a t e d polypropylene f i b e r s t o port land cement concrete helped t o reduce shrinkage and cont ro l cracking. These r e s u l t s prompted t h e subject s e r i e s of tests t o inves t iga t e p l a s t i c and drying shrinkage differences f o r f ib rous and companion non-fibrous specimens. Fibers of two manufacturers were used; one a t t he manufacturers recommended volume loading and the other a t t h ree l e v e l s of t h a t f i b e r volume loading. P l a s t i c shrinkage t e s t s i n accordance w i t h ASTM C827 and drying shrinkage t e s t s were used t o achieve t h e highest shrinkage r a t e . Control s t r eng th tes ts of compression, f lexure and s p l i t t i n g tension were reported f o r t he specimens obtained from the shrinkage t e s t batches. The tests showed t h a t t he use of f i b r i l l a t e d polypropylene f i b e r s r e su l t ed i n a s i g n i f i c a n t reduction i n the p l a s t i c and drying shrinkage when compared t o non-fibrous specimens.

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1987

2141. Ba laguru , P . N . , and A. E z e l d i n , "BEHAVIOR OF PARTIALLY PRESTRESSED BEAMS MADE WITH H I G H STRENGTH F I B E R REINFORCED CONCRETE,*I U e r Reinforced C o n c r e t e : P r o n d e s a n d l i c - , SP 105-24, American C o n c r e t e I n s t i t u t e , D e t r o i t , 1987, pp . 419-436.

T h i s paper p r e s e n t s t h e r e s u l t s of a n e x p e r i m e n t a l i n v e s t i g a t i o n on t h e b e h a v i o r o f p a r t i a l l y prestressed T beams c o n t a i n i n g s teel f i b e r s . High s t r e n g t h c o n c r e t e w i t h s t r e n g t h s h i g h e r t h a n 8,800 p s i , m i l d s teel w i t h y i e l d s t r e n g t h o f 60 k s i , 270 k s i 7 w i r e s t r a n d s , a n d 30 mm f i b e r s w i t h hooked e n d s were u s e d f o r t h e e n t i r e i n v e s t i g a t i o n . Condensed s i l i ca fume a n d h i g h r a n g e w a t e r r e d u c i n g m i x t u r e s were u s e d t o o b t a i n t h e h i g h s t r e n g t h c o n c r e t e . S i x T beams w e r e t es ted u s i n g a s i m p l y s u p p o r t e d span of 7 ' 6" a n d 2 c o n c e n t r a t e d loads. F i b e r c o n t e n t w a s var ied from 0 t o 250 pounds per c u b i c y a r d . Only minimum s h e a r r e i n f o r c e m e n t was provided fo r a l l beams. The f l e x u r a l r e i n f o r c e m e n t w a s d e s i g n e d t o create s h e a r f a i l u r e , i n order t o e v a l u a t e t h e f iber c o n t r i b u t i o n t o s h e a r a t l o w s h e a r s p a n s . T h e beams w e r e i n s t r u m e n t e d t o measure d i s p l a c e m e n t s i n t h e n o n p r e s t r e s s e d a n d p r e s t r e s s e d r e i n f o r c e m e n t , c u r v a t u r e , c r a c k s p a c i n g , c r a c k wid th , and d e f l e c t i o n . C y l i n d e r s were tes ted t o o b t a i n t h e compressive s t r e n g t h of c o n c r e t e . For lower s h e a r s p a n s , t h e c o n t r i b u t i o n of f i b e r s t o t h e s h e a r c a p a c i t y i s l o w . T h e f i b e r r e i n f o r c e d beams undergo more d e f o r m a t i o n before f a i l u r e .

2 1 4 2 . Ba laguru , P . , a n d J . Kendzulak, "MECHANICAL PROPEERTIES OF SLURRY INFILTRATED FIBER CONCRETE (SIFCON)," Fiber

ed Concre t e : P r o n w e s and ADpllCatlOnS, SP 105-14, American Concrete I n s t i t u t e , Det ro i t , 1 9 8 7 , p p . 247-268.

T h i s paper p r e s e n t s t h e r e s u l t s of a n e x p e r i m e n t a l i n v e s t i g a t i o n on t h e b e h a v i o r o f SIFCON s u b j e c t e d t o f l e x u r a l , s h e a r , and a x i a l t e n s i l e l o a d i n g . More emphas is w a s placed on t h e f l e x u r a l b e h a v i o r i n which t h e spec imens w e r e s u b j e c t e d t o s t a t i c a n d h igh a m p l i t u d e c y c l i c l o a d i n g . Four f i b e r l e n g t h s , namely: 30, 40, 50, and 60 mm and f o u r volume c o n t e n t s r a n g i n g f r o m 4 t o 1 2 % were u s e d . Fibers w i t h hooked e n d s w e r e u sed f o r t h e e n t i r e i n v e s t i g a t i o n . E f f e c t of t h e a d d i t i o n o f s i l i c a fume and s a n d t o t h e cement s l u r r y w a s i n v e s t i g a t e d u s i n g a selective g r o u p of spec imens made w i t h 8% f i b e r c o n t e n t . Freeze- thaw s t u d i e s w e r e a l so conduc ted u s i n g prisms which had 8 % by volume of f ibers . The behavior i n shear w a s s t u d i e d u s i n g direct

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s h e a r spec imens . P r o p e r t i e s i n a x i a l t e n s i o n w e r e i n v e s t i g a t e d u s i n g f o u r f i b e r c o n t e n t s and 50 mm f ibers . The r e s u l t s i n d i c a t e t h a t s t r e n g t h s up t o 1 0 , 000 p s i , 4 ,000 p s i , and 2,000 p s i can be o b t a i n e d i n f l e x u r e , d i rec t s h e a r , and a x i a l t e n s i o n , r e s p e c t i v e l y . The compos i t e w a s found e x t r e m e l y d u c t i l e i n a l l modes of l o a d i n g . Based on t h e tes ts conduc ted i n f l e x u r e , t h e a d d i t i o n of s i l i c a fume i n c r e a s e s t h e s t r e n g t h . Sand c a n be added t o t h e s l u r r y w i t h o u t r e d u c i n g t h e s t r e n g t h up t o a c e r t a i n cement-sand r a t i o . The d u c t i l i t y c h a r a c t e r i s t i c s are n o t affected by t h e a d d i t i o n of e i t h e r s a n d o r s i l i c a fume.

2 1 4 3 . Ba laguru , P . , and V . Ramakrishnan, "PROPERTIES OF LIGHTWEIGHT F I B E R REINFORCED CONCRETE," F ibe r

105-17, American C o n c r e t e I n s t i t u t e , De t ro i t , 1 9 8 7 , pp. l i c a t i o n s , SP

305-322.

T h i s paper p r e s e n t s t h e r e s u l t s of a n e x p e r i m e n t a l i n v e s t i g a t i o n o f t h e properties o f s t ee l f i b e r r e i n f o r c e d s t r u c t u r a l l i g h t w e i g h t c o n c r e t e . The c o n c r e t e w a s p r o p o r t i o n e d t o o b t a i n a compressive s t r e n g t h of a b o u t 6 ,000 p s i . The t a r g e t e d v a l u e s f o r t h e slump and a i r voids were 4-6 i n and 8%, respec t ive ly . C o l l a t e d fibers w i t h end hooks 300 mm l o n g w e r e u s e d f o r t h e e n t i r e i n v e s t i g a t i o n . The f r e s h c o n c r e t e w a s t es ted f o r t e m p e r a t u r e , slump, V-B t i m e , f l o w t ab le spread, a i r c o n t e n t and u n i t w e i g h t . The h a r d e n e d c o n c r e t e was tested f o r d r y u n i t we igh t , compressive s t r e n g t h , f l e x u r a l s t r e n g t h , s p l i t t i n g t e n s i l e s t r e n g t h , and s h r i n k a g e . I n a d d i t i o n t o t h e s e r e s u l t s , a comparative e v a l u a t i o n of normal we igh t and l i g h t w e i g h t f i b e r r e i n f o r c e d c o n c r e t e s i s a l s o presented. The results show t h a t highly workable, h i g h s t r e n g t h , l i g h t w e i g h t f i b e r r e i n f o r c e d c o n c r e t e c a n be p roduced s u c c e s s f u l l y . The ene rgy a b s o r p t i o n o f t h e l i g h t w e i g h t concrete w a s more t h a n t h a t o f normal we igh t c o n c r e t e .

2 1 4 4 . B a r r , B . , "THE FRACTURE CHARACTERISTICS OF FRC

e r t ies a n d l i c a t i m , SP 105-2, American MATERIALS I N SHEAR," U e r Reinforced C o n c r e t e :

C o n c r e t e I n s t i t u t e , Detroi t , 1987, p p . 27-53.

T h i s p a p e r i n v e s t i g a t e s t h e r e l a t i o n s h i p between t h e specimen g e o m e t r i c a l s i z e and t h e s h e a r s t r e n g t h of t h e f iber r e i n f o r c e d c o n c r e t e m o r t a r . Seven spec imens w i t h d i f f e r e n t g e o m e t r i e s w e r e s t u d i e d . T h e o b j e c t i v e was t o f i n d a be t te r d e f i n i t i o n for t h e t o u g h n e s s index , where no r e s t r i c t i o n may a p p l y on t h e t y p e o f tes t specimen u s e d . The t o u g h n e s s i n d e x d e f i n i t i o n proposed by t h e

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a u t h o r i s based on t h e load-def1ec:tion cu rve o b t a i n e d t o twice t h e d e f l e c t i o n a t f i r s t <:rack and i s bounded by a n upper bound e q u a l t o u n i t y and lower bound e q u a l t o 1 / 4 . T h i s d e f i n i t i o n i s compared t o t h a t proposed by Johns ton . R e s u l t s from t h e s t u d y showed t h a t t h e s h e a r s t r e n g t h i s independent of t h e s t e e l f i b e r c o n t e n t . However, s h e a r s t r e n g t h was found t o be p r o p o r t i o n a l t o glass FRC f i b e r c o n t e n t and i n v e r s e l y p r o p o r t i o n a l t o polypropylene FRC f i b e r c o n t e n t . For a l l t y p e s of f ibers, t h e toughness index w a s found t o be p r o p o r t i o n a l t o t h e f iber c o n t e n t .

2145. Chuang, T . , and Y . Mai, "BEHAVIOR OF STRAIN SOFTENING MATERIALS I N FLEXURAL BENDING," U e r R e i n f o r c e d

e te : P r o D e r t i e s m c a t i o u s , SP 105-5, American Concre te I n s t i t u t e , D e t r o i t , 1987, pp . 85-100.

T h i s s t u d y a t t e m p t s t o t h e o r e t i c a l l y p r e d i c t t h e complete l o a d - d e f l e c t i o n cu rve of s t r a i n s o f t e n i n g materials s u b j e c t e d t o bending. S t r a i n s o f t e n i n g phenomena occur s when t h e material e x h i b i t s n o n l i n e a r i t y p r i o r t o r each ing t h e peak l o a d on t h e s t r e s s - s t r a i n curve due t o t h e fo rma t ion of microcracks. Cement mor ta r r e i n f o r c e d w i t h s h o r t s t e e l f ibers i s an example of such a mater ia l . The t e n s i l e s t r a i n s o f t e n i n g response may a l s o be p r e d i c t e d if s p e c i f i c bending load-displacement d a t a i s g i v e n . I n t h i s a n a l y s i s , t h e s t r e s s - s t r a i n r e l a t i o n s h i p of t h e s t r a i n s o f t e n i n g material i s assumed t o be l i n e a r up t o t h e p o i n t of maximum l o a d i n b o t h t e n s i o n and compression. Young modulus i n t e n s i o n and compression i s assumed t o be t h e same. A uniform r e c t a n g u l a r beam s u b j e c t e d t o a fou r -po in t - load ing w a s u s e d . A n a l y t i c a l e x p r e s s i o n s f o r p r e d i c t i n g t h e i n t e r n a l moment w e r e developed f o r two zones: t h e l i n e a r r e g i o n and t h e c r a c k growth r e g i o n ( i . e . , r e g i o n a t which a v i s i b l e c r a c k i s seen t o d e v e l o p ) . For t h e s t r a i n s o f t e n i n g zone growth r eg ion , a numer ica l t e c h n i q u e was employed due t o t h e h igh n o n l i n e a r i t y of t h e e q u a t i o n s u s e d .

2 1 4 6 . C l a r k e , R . , and A . Sharma, "FLEXURAL BEHAVIOR OF FIBRO-FERROCRETE ONE-WAY SLABS," i, SP 105-27, American Concre te I n s t i t u t e , D e t r o i t , 1987, pp . 493-516.

F i b r o - f e r r o c r e t e can be v i s u a l i z e d as a new m a t e r i a l which j u d i c i a l l y combines r e i n f o r c e d c o n c r e t e wi th f i be r s t o g i v e a s t r o n g and e f f e c t i v e s t r u c t u r a l mater ia l . Th i s material can be r e a d i l y f a b r i c a t e d i n t o beams and f l a t p l a t e e lements which are s t r u c t u r a l l y e f f i c i e n t and s t r o n g . The p r e s e n t paper r e p o r t s t e s t s

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of 6 f ib ro- fer rocre te one way s l abs subjected t o f l e x u r a l loadings. The f ac to r s a f f e c t i n g t h e s t rength of such s l abs a r e examined. A theory i s presented t o determine t h e f l e x u r a l s t rength of f ib ro - fe r roc re t e one-way s l a b s . The ul t imate s t rengths obtained from 5 of t h e 6 tes t r e s u l t s exceed t h e ca lcu la ted values derived from the proposed theory, usual ly by 20 t o 30 percent .

2 1 4 7 . Craig, R . J . , "FLEXURAL BEHAVIOR AND D E S I G N OF REINFORCED FIBER CONCRETE MEMBERS," J Z i h ~ h f o r c e d

American Concrete I n s t i t u t e , Detroi t , 1987, pp. e te : P r o E r t i e s andADDllcatlons, SP 105-28,

517-563.

I n t h i s paper, design and ana lys i s methodologies w i l l be discussed so t h a t t h i s type of construct ion can be successfu l ly developed by engineers. R e s u l t s of 13 beams t e s t e d a t New Jersey I n s t i t u t e of Technology a r e presented t o show t h e nature of t h e f l exura l behavior. These beams a r e f o r : (1) normal concrete, ( 2 ) high s t r eng th concrete, and (3) l ightweight concrete w i t h and without f i b e r s . Most of t h e r e s u l t s of t h i s paper have not been reported previously. A computer program which accurately p red ic t s t h e f l exura l behavior of these beams and other f i b e r re inforced concrete members i s presented a s wel l . I n e l a s t i c and e l a s t i c behavior of FRC i n f lexure i s discussed. The main p a r t of t he paper concentrates on ana lys i s and design methods. A method developed a t N J I T i s explained f o r analyzing regular s ing ly reinforced, doubly reinforced, and "T" beams. Analysis equations and design methodologies a r e shown f o r each type of beam.

2148. Foote, R.,Y. Mai, and B. Co t t e re l l , "PROCESS ZONE SIZE AND CRACK GROWTH MEASUREMENT I N F IBER CEMENTS," F ibe r

105-3, American Concrete I n s t i t u t e , Det ro i t , 1 9 8 7 , pp. 55-70.

orced Concrete: Pro-es and B p g l i c a t i o u , SP

An inves t iga t ion i s ca r r i ed out t o measure the f r a c t u r e process zone, FPZ, i n wood f i b e r re inforced mortar using a computerized technique. Cracks over a length = 5.52 inches along t h e specimen were measured by means of a data acquis i t ion system which records the crack t i p growth using a uniform conductive bar g r i d p a t t e r n f o r t h e compact tension geometry. A broken bar ind ica ted t h a t t h e specimen i s cracked a t t h a t l oca t ion . Crack growth was observed t o be s t a b l e . Flexural t es t s w e r e performed on s t r i p s taken from t h e specimen s o t h a t t o obtain t h e s t i f f n e s s of t h e mater ia l a t t h e post cracking s tage . Average crack

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l e n g t h s = 31.5". FPZ was a l so obse rved t o i n f l u e n c e t h e K r c u r v e and hence must be i n c l u d e d i n any f r a c t u r e a n a l y t i c a l model.

2149. Gopalaratnam, V . S., and S . P . Shah, "FAILURE

er Seinforced m: PEpOerties MECHANISMS AND FRACTURE OF FIBER REINFORCED CONCRETE,"

-, SP 105-1, American C o n c r e t e I n s t i t u t e , Detroi t , 1987 , pp. 1-25.

T h i s paper d i s c u s s e s t h e v a r i o u s f a i l u r e and f r a c t u r e mechanisms of f iber r e i n f o r c e d c o n c r e t e such as m u l t i p l e f r a c t u r e of t h e m a t r i x p r io r t o composite f r a c t u r e , c a t a s t r o p h i c f a i l u r e and f iber p u l l - o u t f o l l o w i n g m a t r i x c r a c k i n g , and f r a c t u r e of sho r t f ibers w i t h o u t m u l t i p l e f r a c t u r e of t h e m a t r i x . I n t e r f a c i a l b o n d - s l i p and m a t r i x s o f t e n i n g are a l so d i s c u s s e d . A n a l y t i c a l models f o r t e n s i l e r e s p o n s e p r e d i c t i o n are p r e s e n t e d . I t i s concluded t h a t while several models are available t o model FRC, t h e t y p e of model t o be used is dictated by t h e a n t i c i p a t e d mechanism of f a i l u r e of t h e composi te and t h e t y p e of s o l u t i o n s desired.

2150. H o f f , G . C . , 'IDURABILITY OF FIBER REINFORCED CONCRETE I N A SEVERE MARINE ENVIRONMENT," P roceed ings , K a t h a r i n e and Bryant Mather I n t e r n a t i o n a l Symposium on C o n c r e t e D u r a b i l i t y , American Concre t e I n s t i t u t e , Det ro i t , SP 1001 Vole 1, 1987, pp. 997-1041.

The d u r a b i l i t y o f c o n c r e t e i n a mar ine envi ronment i s a f u n c t i o n of i t s m i x t u r e c o n s t i t u e n t s , f r eeze - thaw s u s c e p t i b i l i t y , a b r a s i o n resistance, f a t i g u e s t r e n g t h , and c o r r o s i o n of embedded metal. These problems u s u a l l y m a n i f e s t t hemse lves i n t h e t i d a l and s p l a s h zones of a s t r u c t u r e . Fiber r e i n f o r c e d c o n c r e t e h a s been shown t o have improved f a t i g u e c h a r a c t e r i s t i c s a n d improved c r a c k i n g b e h a v i o r o v e r c o n v e n t i o n a l c o n c r e t e . These properties can be advan tageous ly a p p l i e d t o c o n c r e t e i n a mar ine envi ronment p r o v i d e d t h e d u r a b i l i t y i n t h a t envi ronment i s s a t i s f a c t o r y . This p a p e r describes a large number of both l a b o r a t o r y a n d f i e l d fes ts of f iber r e i n f o r c e d c o n c r e t e s u b j e c t e d t o a s e v e r e exposure envi ronment t h a t have been conduc ted o v e r t h e las t 20 years. F i e l d tes ts i n both m i l d and mar ine envi ronments are i n c l u d e d . Performance data a n d m i x t u r e i n f o r m a t i o n from these s t u d i e s are provided.

366

2151. H o f f , G . C . , "DURABILITY OF FIBER REINFORCED CONCRETE I N A SEVERE MARINE ENVIRONMENT, P roceed ings , K a t h a r i n e and Bryant Mather I n t e r n a t i o n a l Symposium on Concre t e D u r a b i l i t y , American Concre t e I n s t i t u t e , Det ro i t , SP 100, V o l . 1, 1987, pp. 997-1041.

The d u r a b i l i t y of c o n c r e t e i n a mar ine envi ronment i s a f u n c t i o n of i t s m i x t u r e c o n s t i t u e n t s , f r eeze - thaw s u s c e p t i b i l i t y , a b r a s i o n r e s i s t a n c e , f a t i g u e s t r e n g t h , and c o r r o s i o n of embedded metal. These problems u s u a l l y m a n i f e s t t hemse lves i n t he t i d a l and splash zones of a s t r u c t u r e . Fiber r e i n f o r c e d c o n c r e t e have been shown t o have improved f a t i g u e characteristics and improved c r a c k i n g b e h a v i o r o v e r c o n v e n t i o n a l c o n c r e t e . These properties can be advan tageous ly applied t o c o n c r e t e i n a mar ine environment p r o v i d i n g t h e d u r a b i l i t y i n t h a t environment i s s a t i s f a c t o r y . T h i s paper describes a large number of b o t h l a b o r a t o r y and f i e l d t e s t s o f fiber r e i n f o r c e d c o n c r e t e s u b j e c t e d t o a s e v e r e exposure environment t h a t have been conducted over t h e l a s t 20 y e a r s . F i e l d tes ts i n b o t h m i l d and mar ine env i ronmen t s are i n c l u d e d . Performance data and m i x t u r e i n f o r m a t i o n from these s t u d i e s i s provided.

2152. H o m r i c h , J . R . , and A . E . Naaman, "STRESS-STRAIN PROPERTIES OF S I F C O N I N COMPRESSION,"

ete: ProDerties and U c a t i m , SP 105-16, American Concre t e I n s t i t u t e , Det ro i t , 1987, pp. 283-304.

The o b j e c t i v e of t h i s research i s t o s t u d y t h e s t r e s s - s t r a i n r e l a t i o n s h i p of s l u r r y i n f i l t r a t e d f i b e r r e i n f o r c e d c o n c r e t e , SIFCON, under s t a t i c u n i a x i a l direct compress ion . Behavior was i n f l u e n c e d by t h e f iber t y p e , cement mix, specimen p r e p a r a t i o n p rocedure , and t h e o r i e n t a t i o n of t h e f i b e r w i t h respect t o applied l o a d i n g . Four t y p e s of s l u r r y mixes w e r e u s e d a l o n g w i t h th ree t y p e s of steel f ibers. O r i e n t a t i o n o f t h e f ibers w a s se t i n t w o ways: f ibers pa ra l l e l and f ibers normal t o t h e d i r e c t i o n of t h e a p p l i e d compress ive force. Diagonal shear c r a c k i n g was found t o be t h e predominant mode of f a i l u r e . Toughness i n d e x of SIFCON i n compression was found t o exceed 50.

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2153. Houde, J . , A . Prezeau , and R . ROUX, "CREEP OF CONCRETE CONTAINING FIBERS AND SILICA FUME," U e r Reinforced 1, SP 105-6, American Concre t e I n s t i t u t e , D e t r o i t , 1987, pp. 101-110.

The purpose of t h i s e x p e r i m e n t a l program i s t o examine c r e e p of steel and po lypropy lene f i b e r r e i n f o r c e d mortar c o n t a i n i n g s i l i c a fume. The a d d i t i o n o f f ibers w a s obse rved t o i n c r e a s e t h e c r e e p d e f o r m a t i o n s by 20-40% due t o t h e i n c r e a s e i n t h e volume of a i r e n t r a p p e d when f ibers are added t o p l a i n c o n c r e t e . However, when 0-10% of s i l i ca fume w a s added, creep f o r b o t h p l a n e and f i b e r r e i n f o r c e d mortar had decreased by 30%. For h i g h e r p e r c e n t a g e s o f s i l i c a fume, t h e decrease i n c r e e p de fo rma t ion w a s on t h e order of 10-15%. Two e q u a t i o n s were u s e d t o p r e d i c t creep: t h e h y p e r b o l i c e q u a t i o n proposed by R o s s and t h e l o g a r i t h m i c e q u a t i o n proposed by t h e U n i t e d S t a t e s Bureau of Reclamation, USBR. Creep d e f o r m a t i o n s were c a l c u l a t e d based on a 56 and 280 day-obse rva t ion -pe r iod , DOP. The predicted creep a t 336 days u s i n g t h e 280 DOP was v e r y close t o t h e observed when t h e e q u a t i o n g i v e n by R o s s and USBR were u s e d . However, t h e 56 DOP gave less a c c u r a t e predicted c r e e p d e f o r m a t i o n s .

2154. Jamrozy, Z. , and J . Olek, "TECHNOLOGICAL ASPECTS OF STEEL F I B E R REINFORCED CONCRETES, 'I U e r Reinfarced

American Concre t e I n s t i t u t e , Det ro i t , 1987, pp . t e : Propert ies a n d c a t i u , SP 105-21,

375-390.

T h i s p a p e r c o n c e n t r a t e s on t h e t e c h n o l o g i c a l aspects of SFRC w i t h r e s p e c t t o w o r k a b i l i t y , u n c o n v e n t i o n a l compact ion t e c h n i q u e s , and l o w p r e s s u r e steam c u r i n g . The i n f l u e n c e of admix tu res a i d i n g t h e c o n s o l i d a t i o n and w o r k a b i l i t y i s i n v e s t i g a t e d . Such a d m i x t u r e s i n c l u d e f l y a s h and s u p e r p l a s t i c i z e r s . The compact ion methods i n v e s t i g a t e d i n c l u d e dewa te r ing , p r e s s i n g , s i m u l t a n e o u s d e w a t e r i n g and p r e s s i n g , and w h i r l i n g .

2155. Krenchel , H . , and S . P . Shah, "RESTRAINED SHRINKAGE TESTS WITH PP-FIBER REINFORCED CONCRETE," Fiber

c a t i w , SP 105-8, American Concre te I n s t i t u t e , Detroit , 1987, pp . 141-158.

R e s t r a i n e d sh r inkage tests w e r e carried o u t on r i n g specimens of c o n c r e t e r e i n f o r c e d wi th polypropylene f i b e r s . These f i b e r s had r e l a t i v e l y improved modulus of e l a s t i c i t y and enhanced bond wi th p o r t l a n d cement m a t r i x . To a c h i e v e uniform d i s p e r s i o n f o r t h e r e l a t i v e l y h igh f i b e r c o n t e n t ( 2 % volume f r a c t i o n ) employed, a conven t iona l pan mixer was a t t a c h e d wi th a high-speed a c t i v a t o r . It w a s observed t h a t even a f t e r s e v e r e d ry ing , no v i s i b l e c r a c k s ( c r a c k s wider t h a n 0 . 0 1 mm) appeared on t h e polypropylene f i b e r r e i n f o r c e d specimen.

2156. L im, T . Y.,P. Paramasivam, and S . L . L e e , "ANALYTICAL MODEL FOR TENSILE BEHAVIOR OF STEEL-FIBER CONCRETE," Materials J o u r n a l of t h e American Concrete I n s t i t u t e , Vol. 84, No. 4 , July-Aug 1987, pp . 286-298.

An a n a l y t i c a l model t o p r e d i c t t h e t e n s i l e behav io r of s tee l f i b e r c o n c r e t e (SFC) i s proposed. The model p r e d i c t s t h e e l a s t i c and pos t -c racking behav io r of SFC by c o n s i d e r i n g t h e t e n s i l e - l o a d e x t e n s i o n r e sponses of an uncracked and precracked SFC specimen. Based on e a s i l y q u a n t i f i a b l e material and mix pa rame te r s , t h e model i s shown t o g i v e good p r e d i c t i o n s when compared t o expe r imen ta l r e s u l t s from SFC mixes u s i n g two t y p e s of f i b e r s . The model a l so e s t a b l i s h e s a r a t iona l b a s i s f o r an i d e a l i z e d t e n s i l e s t r e s s - s t r a i n curve a p p l i c a b l e t o t h e a n a l y s i s of SFC m e m b e r s . The proposed model f o r t h e p r e d i c t i o n of t h e behavior of steel f i b e r c o n c r e t e i s shown t o g i v e good p r e d i c t i o n s of t h e load-extens ion behav io r o f SFC when compared t o expe r imen ta l r e s u l t s . I t p r o v i d e s a r a t i o n a l basis f o r an i d e a l i z e d t e n s i l e s t r e s s - s t r a i n curve t h a t can be used i n t h e a n a l y s i s of SFC members. Both t h e a n a l y t i c a l load-extens ion and i d e a l i z e d s t r e s s - s t r a i n curve can be c o n s t r u c t e d u s i n g fundamental p r o p e r t i e s of t h e c o n s t i t u e n t mater ia ls .

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2157. L i m , T . Y.,P. Paramasivam, and 2;. L . L e e , "BENDING BEHAVIOR OF STEEL-FIBER CONCRETE BEAMS," S t r u c t u r a l J o u r n a l of t h e American Concre te I n s t i t u t e , Vol. 84, No. 6, Nov-Dec 1 9 8 7 , pp. 524-536.

An a n a l y t i c a l and expe r imen ta l i n v e s t i g a t i o n i n t o t h e moment-curvature and t h e l o a d - d e f l e c t i o n characteristics of steel f iber r e i n f o r c e d c o n c r e t e i s r e p o r t e d . E x p l i c i t e x p r e s s i o n s were g iven for t h e modulus of e l a s t i c i t y and t h e t e n s i l e and compressive s t r e s s - s t r a i n behav io r of t h e composi te . The composi te w a s t reated as a bi-modulus material i n f l e x u r e , and t h e moment-curvature and l o a d - d e f l e c t i o n r e l a t i o n s h i p s i n t h e e l a s t i c and cracked range were d e r i v e d . T h i s approach s e r v e d as a u s e f u l t o o l f o r t h e p r e d i c t i o n of t h e f l e x u r a l s t r e n g t h and t h e q u a n t i f i c a t i o n of t h e toughness u s i n g a v a i l a b l e indexes . A n a l y t i c a l e x p r e s s i o n s t o predict t h e moment-curvature and l o a d - d e f l e c t i o n behav io r of SFRC beams are d e r i v e d . They give good p r e d i c t i o n of these r e l a t i o n s h i p s f o r s imply suppor t ed beams tested under t h i r d p o i n t and mid-point l o a d i n g s . Based on t h e q u a n t i f i a b l e mater ia l pa rame te r s and s i m p l i f y i n g i d e a l i z a t i o n s , t h e a n a l y t i c a l approach serves as a u s e f u l t o o l t o s t u d y the s t r e n g t h and deformat ion of SFRC beams i n bending . I n p a r t i c u l a r , f l e x u r a l toughness of SFRC beams c o u l d be e v a l u a t e d on a c o n s i s t e n t basis wi thout r e l y i n g so le ly on l a b o r a t o r y tes t p l o t s .

2158. L im, T . Y., and S . L . Lee, "SHEAR AND MOMENT CAPACITY OF REINFORCED STEEL-FIBER-CONCRETE BEAMS," Magazine of Concre te Research, V o l . 39 , N o . 140, Sept 1987, pp. 148-160.

An a n a l y t i c a l approach f o r p r e d i c t i n g t h e shear and moment c a p a c i t y of r e i n f o r c e d s t e e l - f i b e r - c o n c r e t e (RSFC) beams i s proposed. Recent p l a s t i c i t y a n a l y s e s f o r shear c a p a c i t y of r e i n f o r c e d c o n c r e t e beams are extended t o RSFC beams by i n c l u d i n g t h e c o n t r i b u t i o n of t h e fibers. Moment c a p a c i t y i s derived by u s i n g t h e u s u a l s e c t i o n a l a n a l y s i s and f u l l y p l a s t i c i z e d stress b l o c k s and f o r c e s . Analy t ica l ly predicted f a i l u r e l o a d s and modes of f a i l u r e agree w e l l w i t h test data from 22 beams tested as w e l l as w i t h data i n t h e l i t e r a t u r e . The a n a l y s i s allows f o r a direct comparison between t h e e f f e c t i v e n e s s of s t i r r u p s and f ibers as shear r e in fo rcemen t . The r e s u l t s sugges t t h a t f ibers can r e p l a c e ver t ical s t i r r u p s e i ther p a r t i a l l y o r wholly as long as p a r i t y i n t h e shear r e in fo rcemen t f a c t o r i s ma in ta ined .

370

2159. Lim, T.,P. Paramasivam, and S. Lee, "BEHAVIOR OF REINFORCED STEEL-FIBER-CONCRETE BEAMS IN FLEXURE," Journal of Structural Engineering, Vol. 113, No. 12, Dec 1987, pp. 2439-2458.

An analytical and experimental investigation was carried out to study the deformational behavior and strength of fiber reinforced concrete beams in flexure. Explicit expressions are derived for the moment-curvature and load-deflection relationships for simply supported beams based on idealized stress-strain relationships for steel and concrete. The flexural strength and ductility at ultimate loading conditions were increased in SFRC beams as compared to normal reinforced concrete beams.

2160. Mandel, J. A.,S. Wei, and S. Said, "STUDIES OF THE PROPERTIES OF THE FIBER-MATRIX INTERFACE IN STEEL FIBER REINFORCED MORTAR," Materials Journal of the American Concrete Institute, Vol. 84, No. 2, Mar-Apr 1987, pp. 101-109.

The properties of the interface between the fiber and matrix material have a significant effect on both the strength and toughness of a fiber reinforced composite. To model fiber debonding, it is necessary to determine the coefficient of adhesion between the fiber and matrix material. A procedure was developed to determine the coefficient of adhesion. This procedure utilizes the results of a fiber pullout test and finite element analysis. Interface properties between a straight steel fiber and two matrix materials (mortar both with and without polymer) were investigated. For a given fiber spacing, values for the coefficient of adhesion for a mortar matrix material with polymer were shown to be significantly higher than those without polymer. The average interfacial bond strength and stiffness for a matrix material with 10 percent by weight of cement of polymer were shown to be approximately twice the values measured using mortar matrix without polymer. The energy required for fiber debonding and pullout was also approximately doubled by adding 10 percent by weight of cement of the polymer.

371

2161. Mondragon, R . , "SIFCON I N COMPRESSION, Fiber ced C o n u e t e : Properties and, SP

105-1, American C o n c r e t e I n s t i t u t e , Detroi t , 1987, pp. 260-281.

T h i s a r t i c l e p r e s e n t s c o n c l u s i o n s derived from r e s e a r c h conduc ted on SIFCON. The a r t i c l e d i s c u s s e s t h e effect of v a r y i n g t h e water /cement ( w / c ) r a t i o and t h e f l y a s h t o cement r a t i o on t h e compressive s t r e n g t h . T h i s i n v e s t i g a t i o n showed t h a t c o n t r a r y t o ear l ie r i n v e s t i g a t i o n s , t h e s t r e n g t h of t h e s l u r r y c o n t r i b u t e s s i g n i f i c a n t l y t o t h e SIFCON s t r e n g t h , where a change i n t h e s l u r r y s t r e n g t h t e n d s t o be r e f l e c t e d i n a c o r r e s p o n d i n g change i n SIFCON s t r e n g t h . By u s i n g t h e same t y p e o f f i b e r s a n d v a r y i n g t h e s l u r r y i n g r e d i e n t s , a r a n g e of compress ive s t r e n g t h s v a r y i n g between 7 and 23 k s i w a s o b t a i n e d . D e c r e a s i n g t h e w / c and t h e w / c + f l y a s h r a t i o s i n c r e a s e d t h e compressive s t r e n g t h . I n c r e a s i n g t h e cement c o n t e n t a lso i n c r e a s e d t h e compressive s t r e n g t h . T h e r e f o r e , SIFCON c a n be e x p e c t e d t o g a i n p o p u l a r i t y i n a p p l i c a t i o n s where h i g h s t r e n g t h a n d d u c t i l i t y are needed .

2162. Naaman, A. E., " H I G H PERFORMANCE F I B E R REINFORCED COMPOSITES," P roceed ings , C o n c r e t e S t r u c t u r e s f o r t h e F u t u r e , IABSE Symposium, P a r i s , Versailles, 1987, p p . 371-376.

A brief s y n t h e s i s o f t h e b e h a v i o r a n d mechanics o f f iber r e i n f o r c e d cement based compos i t e s i n t e n s i o n , compress ion , and f l e x u r e i s p r e s e n t e d w i t h p a r t i c u l a r emphas is on t h e i r s t r e s s - s t r a i n , s t r e s s - e l o n g a t i o n , o r l o a d - d e f l e c t i o n r e l a t i o n s h i p s . The l a t e s t advances i n t h e f i e l d are c i ted and optimum s t r e n g t h and t o u g h n e s s propert ies a c h i e v a b l e u s i n g c u r r e n t t e c h n o l o g y are p o i n t e d o u t .

2163. Naaman, A. E . , J . K . Wight, a n d H . Abdou, " S I F C O N CONNECTIONS FOR SEISMIC RESISTANT FRAMES," C o n c r e t e I n t e r n a t i o n a l : Design and C o n s t r u c t i o n , V o l . 9, N o . 11, NOV 1987, p p . 34 -39 .

Progress i n t h e development o f a d u c t i l e moment r e s i s t i n g c o n n e c t i o n f o r precast development o f t h e c a s t - i n - p l a c e c o n n e c t i o n , which i s d e s i g n e d t o act as a p l a s t i c h i n g e d u r i n g e a r t h q u a k e s , i n c l u d e t h e u s e of S l u r r y I n f i l t r a t e d Fiber C o n c r e t e (SIFCON) as t h e m a t r i x , and t h e p l a c i n g o f t h e c o n n e c t i o n one o r t w o beam d e p t h s away f r o m t h e face of t h e column.

37 2

\

2 1 6 4 . Narayanan, R . , and I . Y . Darwish, "USE OF STEEL FIBERS AS SHEAR REINFORCEMENT, S t r u c t u r a l J o u r n a l o f t h e American Concre te I n s t i t u t e , V o l . 84, No. 3, May-Jun 1987, pp . 216-227.

I n v e s t i g a t i o n s on t h e behav io r of s teel f iber r e i n f o r c e d c o n c r e t e beams subjected t o s h e a r are p r e s e n t e d . The r e s u l t s of some 49 s h e a r tests carr ied o u t on s imply suppor t ed r e c t a n g u l a r beams under symmetr ica l ly p l a c e d c o n c e n t r a t e d loads are p r e s e n t e d and ana lyzed; of t h o s e , 10 beams c o n t a i n e d conven t iona l s t i r r u p s and 33 w e r e r e i n f o r c e d w i t h crimped s teel f i b e r s as web r e in fo rcemen t . The tes t r e s u l t s show t h a t t h e f i rs t crack s h e a r s t r e n g t h i n c r e a s e d s i g n i f i c a n t l y due t o t h e c r a c k - a r r e s t i n g mechanism of t h e f ibers ; t h e improvement i n t h e u l t i m a t e s h e a r s t r e n g t h w a s t o t h e same o r d e r as t h a t o b t a i n e d from conven t iona l s t i r r u p s even f o r a f i b e r volume f r a c t i o n o f 1%. The comparisons between t h e computed v a l u e s and t h e e x p e r i m e n t a l l y observed v a l u e s are shown t o val idate t h e proposed t h e o r e t i c a l t r e a t m e n t .

2165. Ramakrishnan, V.,G. Ober l ing , and P . T a t n a l l , "FLEXURAL FATIGUE STRENGTH OF STEEL FIBER REINFORCED CONCRETE,"

-, SP 105-13, American Concre te I n s t i t u t e , D e t r o i t , 1987, pp . 225-245.

t i e s and

T h i s pape r p r e s e n t s t h e r e s u l t s of a n expe r imen ta l i n v e s t i g a t i o n t o de te rmine t h e f l e x u r a l f a t i g u e s t r e n g t h o f c o n c r e t e r e i n f o r c e d w i t h c o l l a t e d hooked-end steel f i b e r s . The performance of f r e s h c o n c r e t e and t h e e l a s t i c and mechanical p r o p e r t i e s of hardened c o n c r e t e s w i th and wi thout f i b e r s are compared. The t e s t program inc luded t h e fo l lowing : (1) f l e x u r a l f a t i g u e and endurance l i m i t ; ( 2 ) s t a t i c f l e x u r a l s t r e n g t h i n c l u d i n g l o a d - d e f l e c t i o n cu rve , d e t e r m i n a t i o n of f i r s t crack load , and toughness index; (3 ) compressive s t r e n g t h ; ( 4 ) s t a t i c modulus; ( 5 ) p u l s e v e l o c i t y ; and ( 6 ) u n i t weight and w o r k a b i l i t y and f i n i s h a b i l i t y of f r e s h c o n c r e t e . Two c o n c e n t r a t i o n s of f ibers w e r e used throughout t h e program. S p e c i a l care w a s t a k e n t o i n s u r e c o n s i s t e n c y wi th cement, aggregates, admixtures , p rocedure , and mix t e m p e r a t u r e s .

373

2166. Ramakrishnan, V.,S. Gol lapudi , and R . Zellers, "PERFORMANCE CHARACTERISTICS AND FATIGUE STRENGTH OF POLYPROPYLENE F I B E R REINFORCED CONCRETE," Fiber

d CQaCZrete: Pro:, SP 105-9, American Concre te I n s t i t u t e , Det ro i t , 1987, pp. 159-177.

T h i s paper p r e s e n t s t h e r e s u l t s of a n e x p e r i m e n t a l i n v e s t i g a t i o n t o de te rmine t h e f l e x u r a l f a t i g u e s t r e n g t h of c o n c r e t e r e i n f o r c e d w i t h col la ted f i b r i l l a t e d po lypropy lene f ibers . The per formance of fresh c o n c r e t e and t h e e las t ic and mechanica l properties of hardened c o n c r e t e are compared f o r c o n c r e t e s w i t h and wi thou t f ibers . The t es t program i n c l u d e d : (1) f l e x u r a l f a t i g u e and endurance l i m i t ; ( 2 ) s t a t i c f l e x u r a l s t r e n g t h i n c l u d i n g l o a d - d e f l e c t i o n cu rve , d e t e r m i n a t i o n of f i r s t crack load, toughness index; ( 3 ) compressive s t r e n g t h ; ( 4 ) s t a t i c modulus; (5) p u l s e v e l o c i t y ; and (6) u n i t weight and w o r k a b i l i t y and f i n i s h a b i l i t y of fresh c o n c r e t e . The complete series of tes ts were r u n for three c o n c e n t r a t i o n s of fibers. No b a l l i n g or t a n g l i n g o c c u r r e d d u r i n g mixing and p l a c i n g . D u c t i l i t y and ene rgy a b s o r p t i o n was i n c r e a s e d due t o f iber a d d i t i o n . A s l i g h t i n c r e a s e i n t h e s t a t i c f l e x u r a l s t r e n g t h and a moderate i n c r e a s e i n t h e f a t i g u e f l e x u r a l s t r e n g t h w a s obse rved .

2167 . Roik, K. , C . Diekmann, and K . Schwalbenhofer , "COMPOSITE COLUMNS WITH STEEL FIBER REINFORCED CONCRETE [VERBUNDSTUETZEN MIT STAHLFASERBETON]," Bauingenieur ,

V o l . 62, N o . 4, A p r 1987, pp. 179-182.

T h i s paper p r e s e n t s t e s t s on s t ee l - conc re t e -compos i t e columns c o n s i s t i n g of s t ee l f iber r e i n f o r c e d c o n c r e t e encased wide f l a n g e H-sec t ions wi thou t a d d i t i o n a l r e i n f o r c e m e n t . The a u t h o r f o c u s e s on t h e s p a l l i n g of c o n c r e t e j u s t above t h e f l a n g e s of t h e H-sec t ions . P a r t i c u l a r a t t e n t i o n w a s given t o t h e e f f e c t of t y p e of loading on t h e f i r e r e s i s t a n c e . C a l c u l a t i o n s based on t h e e x p e r i m e n t a l l o a d - d e f l e c t i o n c u r v e s showed good agreement w i t h t h e measurements.

374

2168. Sood, V . , and S . Gupta, "BEHAVIOR OF STEEL FIBROUS CONCRETE BEAM-COLUMN CONNECTIONS, 'I W r R e i n f o r c e d

American Concre t e I n s t i t u t e , Det ro i t , 1987, pp. 437-474.

ete: P r w e s and, SP 105-25,

Expe r imen ta l i n v e s t i g a t i o n s w e r e made t o s t u d y t h e b e h a v i o r o f 50 c ros s - type , t e e - t y p e , and knee-type beam t o column c o n n e c t i o n s of c o n v e n t i o n a l and s t ee l f i b r o u s c o n c r e t e , when tested under s t a t i c as w e l l as s l o w c y c l i c f a t i g u e l o a d i n g . T e s t r e s u l t s showed t h a t SFC improved t h e d u c t i l i t y a t t h e j o i n t r e g i o n , i n c r e a s e d t h e load c a r r y i n g c a p a c i t y , decreased crack width , e l i m i n a t e d s h e a r r e in fo rcemen t and overcome t h e problem of s p a l l i n g of c o n c r e t e i n t h e j o i n t r e g i o n . T e s t i n g a l so i n c l u d e d 20 Knee-type c o n n e c t i o n s w i t h 1 2 specimens of e a c h t y p e t e s t e d under s t a t i c l o a d and 8 under s l o w c y c l i c f a t i g u e l o a d i n g . F i b e r volume f r a c t i o n varied between 0-1%. D e f l e c t i o n , r o t a t i o n s , s t r a i n s and crack wid ths were measured.

2 1 6 9 . So roush ian , P . , and Z . Bayasi , "PREDICTION OF THE TENSILE STRENGTH OF FIBER REINFORCED CONCRETE: A CRITIQUE OF THE COMPOSITE MATERIAL CONCEPT," F i b e r

105-4, American Concre t e I n s t i t u t e , D e t r o i t , 1 9 8 7 , pp. 71-84.

ed C m e t e : ProDerties m c a t i o u , SP

I n t h i s s tudy, ' t h e l a w of m i x t u r e s (a l so known as t h e composite mater ia l c o n c e p t ) , which assumes t h a t t h e p u l l - o u t r e s i s t a n c e i s a t t r i b u t e d o n l y t o t h e i n t e r f a c i a l bond, i s i n v e s t i g a t e d w i t h r e s p e c t t o p r e d i c t i n g t h e t e n s i l e s t r e n g t h o f s t ee l f i be r r e i n f o r c e d c o n c r e t e by rev iewing p r e v i o u s w o r k . Such s t u d y have r e v e a l e d t h a t t h e p u l l - o u t s t r e n g t h was governed by two mechanisms: (1) t h e i n t e r f a c i a l shear and ( 2 ) t h e f i be r dowel a c t i o n . The a u t h o r s concluded t h a t t h e p u l l - o u t behav io r may depend on s e v e r a l f a c t o r s . Such f a c t o r s i n c l u d e f i b e r l e n g t h , a s p e c t ra t io , i n c l i n a t i o n and r i g i d i t y . Other f a c t o r s are t h e s h e a r stresses between t h e m a t r i x and t h e f i b e r , m a t r i x properties, and t h e number of f ibers per u n i t area. The a u t h o r s have i n d i c a t e d t h a t f u r t h e r s t u d i e s are needed i n order t o c o r r e c t l y e v a l u a t e d i r e c t t e n s i o n t e s t s . Add i t ion of f i b e r s r e s u l t e d i n a 50% i n c r e a s e i n t h e peak t e n s i l e s tress as compared t o an i n c r e a s e of o n l y 30% i n t h e peak t e n s i l e s t r a i n . The s t u d y r e v e a l e d t h a t when peak t e n s i l e stress i s reached , t h e i n t e r f a c i a l bond stress w a s less t h a n i t s peak v a l u e . T h i s l e a d t o t he c o n c l u s i o n t h a t t h e f iber p u l l - o u t mechanism w a s n o t f u l l y e f f e c t i v e a t peak t e n s i l e stresses.

375

2170. Swamy, R . , R . Jones , and T . C h i a m , "SHEAR TRANSFER I N STEEL F I B E R REINFORCED CONCRETE,

Crete: P r o D e r t i e s - and, SP 105-29, American Concre te I n s t i t u t e , D e t r o i t , 1987, pp. 565-592.

T h i s paper p r e s e n t s e x t e n s i v e data on t h e i n f l u e n c e of s teel fibers, a l o n e o r i n c o n j u n c t i o n w i t h c o n v e n t i o n a l s t i r r u p s on shear t r a n s f e r i n c o n c r e t e . The t es t specimens used i n t h i s s t u d y were of t h e push-off t ype w i t h an i n i t i a l l y uncracked or cracked shear p l a n e . The main variables i n v e s t i g a t e d i n c l u d e f ibe r volume, amount o f s t i r r u p s , and t h e type of c o n c r e t e . R e s u l t s show t h a t t h e f i b e r s enhance t h e u l t i m a t e shear t r a n s f e r s t r e n g t h i n b o t h uncracked and precracked specimens. I n t h e l a te r , t h e u l t i m a t e shear s t r e n g t h can be expres sed on t h e basis of Coulomb's c r i t e r i o n . Fibers i n c r e a s e t h e r e s i d u a l shear t r a n s f e r s t r e n g t h , and t h e s h e a r t r a n s f e r s t i f f n e s s can be related t o t h e crack width . The s h e a r t r a n s f e r s t r e n g t h was g e n e r a l l y lower i n l i g h t w e i g h t c o n c r e t e t h a n i n normal weight c o n c r e t e .

2 1 7 1 . Wang, Y.,S. B a c k e r , and V . C . L i , IrAN EXPERIMENTAL STUDY OF SYNTHETIC FIBRE REINFORCED CEMENTITIOUS COMPOSITES," J o u r n a l of Materials Sc ience , Vol. 22, No. 12, D e c 1987, pp. 4281-4291.

Fiber c o n c r e t e i s cons ide red t o be one of t h e most e f f i c i e n t ways f o r improving t h e p r o p e r t i e s of c o n c r e t e . However, c u r r e n t s t u d i e s have focused on s teel and glass f i b e r r e i n f o r c e d matrices. T h i s paper r e p o r t s on t h e expe r imen ta l program, on t h e p r o p e r t i e s of v a r i o u s s y n t h e t i c f iber r e i n f o r c e d con t inuous composites, and t h e properties of t h e r e i n f o r c i n g f ibers . A c r y l i c , p o l y e s t e r , and aramid fibers were tested i n u n i a x i a l t e n s i o n , b o t h i n t h e i r fresh and hardened s t a t e s . Samples of these fibers were found t o l o o s e v a r y i n g amounts of s t r e n g t h w i t h t i m e , depending on t h e a g e i n g t empera tu re . Two d i f f e r e n t t es t methods were used t o measure t h e f i b e r - cement i n t e r f a c i a l bond s t r e n g t h . The t e n s i l e p r o p e r t i e s of c o n c r e t e r e i n f o r c e d w i t h acryl ic , nylon, and aramid fibers, i n terms of random d i s t r i b u t i o n o r u n i a x i a l a l ignment , were s t u d i e d by means o f three d i f f e r e n t tes ts : compact t e n s i o n , f l e x u r a l , and s p l i t t i n g t e n s i l e t es t s . T h e p r o p e r t i e s of c o n c r e t e , p a r t i c u l a r l y t h a t of a p p a r e n t d u c t i l i t y , were found t o be g r e a t l y improved by t h e i n c l u s i o n of such f iber r e in fo rcemen t .

37 6

2 1 7 2 . Wu, G., "STEEL F I B E R REINFORCED HEAT RESISTANT PAVEMENT, Fiber Reinfor_ced C w t e : Pr-es and -, SP 105-18, American Concre te I n s t i t u t e , D e t r o i t , 1987, pp . 323-350.

T h e Navy i s e v a l u a t i n g jet-blast and heat r e s i s t a n t materials f o r high t empera tu re pavements. The research program i n c l u d e s l a b o r a t o r y and je t exhaus t b l a s t tests. T h i s paper describes t h e je t exhaus t b l a s t t es t s on heat r e s i s t a n t pavement materials r e i n f o r c e d w i t h s t a i n l e s s steel f ibe r s . The optimum f iber c o n t e n t f o r t h e jet blast r e s i s t a n t pavement was about 0 .8 t o 1 . 2 % by volume. The t es t p a n e l s p r e p a r e d by c a s t i n g were s t r o n g e r t h a n t h o s e by gunning. The r e s u l t s from t h e j e t exhaus t b las t tests were used i n t h e d e s i g n of f u l l - s c a l e V/TOL tes t pad, AB-8B power check pads, and f i r e f i g h t i n g t r a i n i n g f ac i l i t i e s .

2 1 7 3 . Wu, G., and M . Jones , "NAVY EXPERIENCE WITH STEEL F I B E R REINFORCED CONCRETE AIRFIELD PAVEMENT," F i b e r

105-23, American Concre te I n s t i t u t e , D e t r o i t , 1987, pp. ed Concre te : Progerties a n d a t i o n s , SP

403-418.

T h i s pape r p r e s e n t s t h e U . S . Navy's expe r i ence w i t h the performance of s t e e l f iber reinforced concrete a i r f i e l d pavements and t h e t e c h n i q u e s e v a l u a t e d t o a l lev ia te t h e problem of exposed s u r f a c e s teel f i b e r s . T h e exposed s u r f a c e s teel fibers posed a p o t e n t i a l f o r e i g n o b j e c t damage hazard t o j e t eng ines and i n j u r y h a z a r d t o ground suppor t p e r s o n n e l . The Navy has e l e c t e d t o use t h e s t a n d a r d Navy PCC s l a b s i z e ( 1 2 . 5 f t x 15 f t ) and t h i c k n e s s f o r SFRC pavements because of s lab c u r l i n g and c o r n e r c r a c k i n g problems on SFRC pavements. The diamond blade bump g r i n d i n g t e c h n i q u e i s p r e f e r r e d f o r removing s u r f a c e s teel f ibers because of i t s c o s t and l i f e expec tancy .

3 7 7

1988

2 1 7 4 . A C I Committee 544, "DESIGN CONSIDERATIONS FOR STEEL F I B E R REINFORCED CONCRETE," S t r u c t u r a l J o u r n a l of t h e American Concre te I n s t i t u t e , V o l . 85, No. 5, Sep-Oct 1988, pp . 563-580.

The p r e s e n t s t a t e of development of d e s i g n p r a c t i c e s f o r f i b e r r e i n f o r c e d c o n c r e t e and mor t a r u s i n g s t e e l f ibers i s reviewed. Mechanical p r o e r t i e s are d i s c u s s e d , d e s i g n methods are p resen ted , and t y p i c a l a p p l i c a t i o n s are l i s t e d .

2175. ACI Committee 544, "MEASUREMENT OF PROPERTIES OF F I B E R REINFORCED CONCRETE," Materials J o u r n a l of t h e American Concre te I n s t i t u t e , V o l . 85, No. 6 , Nov-Dec 1988, pp . 583-593.

T h i s r e p o r t o u t l i n e s e x i s t i n g p rocedures f o r specimen p r e p a r a t i o n i n g e n e r a l and d i s c u s s e s t e s t i n g , w o r k a b i l i t y , f l e x u r a l s t r e n g t h , toughness , and energy a b s o r p t i o n . Newly developed tes t methods are p r e s e n t e d f o r t h e f i rs t t i m e f o r impact s t r e n g t h and f l e x u r a l t oughness . The a p p l i c a b i l i t y of t h e f o l l o w i n g tes t s t o f iber r e i n f o r c e d c o n c r e t e (FRC) a re reviewed: a i r c o n t e n t , y i e l d , u n i t weight , compressive s t r e n g t h , s p l i t t i n g t e n s i l e s t r e n g t h , f reeze- thaw r e s i s t a n c e , sh r inkage , c r eep , modulus of e l a s t i c i t y , c a v i t a t i o n , e r o s i o n , and a b r a s i o n r e s i s t a n c e .

2 1 7 6 . Alexander, D . , "FIBRE REINFORCED CONCRETE," J o u r n a l of Ferrocement , Vol . 18, N o . 3, J u l y 1988, pp. 293-299.

The pape r d e a l s w i t h b e n e f i t s d e r i v e d from f ibe r a d d i t i o n i n t e r m s of t h e t e n s i l e performance, ' s h e a r , d u c t i l i t y , and impact r e s i s t a n c e of s t ee l FRC compared p l a i n concrete. Product ion a s p e c t s ( such as composi te mixing and p r o c e s s c o n t r o l ) and some a p p l i c a t i o n s of SFRC are a l s o g i v e n .

378

2 1 7 7 . Balaguru, P . , and V . Ramakrishnan, "PROPERTIES OF F I B E R REINFORCED CONCRETE: WORKABILITY, BEHAVIOR UNDER LONG-TERM LOADING, AND AIR-VOID CHARACTERISTICS," Materials J o u r n a l of t h e American Concre te I n s t i t u t e , Vol. 85, No. 3, May-June 1988, pp. 189-196.

T h i s paper p r e s e n t s t h e r e s u l t s of a n expe r imen ta l i n v e s t i g a t i o n of t h e behav io r of steel f iber r e i n f o r c e d c o n c r e t e . The p r o p e r t i e s i n v e s t i g a t e d were: s e t t i n g times, slump and a i r c o n t e n t loss w i t h t i m e , creep and sh r inkage , and a i r - v o i d characterist ics i n c l u d i n g bubble s i z e d i s t r i b u t i o n . To compare t h e behav io r of f i b e r r e i n f o r c e d c o n c r e t e w i t h p l a i n c o n c r e t e , a l l of t h e p reced ing p r o p e r t i e s were a l s o i n v e s t i g a t e d f o r p l a i n c o n c r e t e mix tu res of similar composi t ion . C o l l a t e d 50 mm i n c h long s t ee l f ibers w i t h hooked ends w e r e used f o r t h e f iber c o n c r e t e . The exper iments were conducted u s i n g t h e a p p r o p r i a t e ASTM s t a n d a r d s . The a i r - v o i d characterist ics were s t u d i e d u s i n g t h e l i n e a r traverse method. T h e r e s u l t s i n d i c a t e d t h a t t h e s e t t i n g t i m e s were about t h e same f o r b o t h c o n c r e t e s . Fiber c o n c r e t e had lower slump and a i r c o n t e n t ; t h e ra te of loss of these parameters w i t h t i m e w a s a l s o s l i g h t l y less, b u t t h e c r e e p deformat ions were s l i g h t l y more.

2178 . B a r r , B . , A . Asgha r i , and T . G . Hughes, "TENSILE STRENGTH AND TOUGHNESS OF FRC MATERIALS," The I n t e r n a t i o n a l J o u r n a l of Cement Composites and Lightweight Concrete , V o l . 10 , No. 2, May 1988, pp. 101-107.

A new compact t e n s i l e t e s t specimen i s r e p o r t e d . The t e s t specimen i s p repa red by t h e i n t r o d u c t i o n of two no tches i n t o a p r i s m a t i c m e m b e r . The geometry i s loaded th rough f o u r p o i n t s i n such a way t h a t a zone of h igh t e n s i l e stresses i s c r e a t e d a long t h e l i n e j o i n i n g t h e r o o t s of t h e two n o t c h e s . Experimental r e s u l t s are g iven for p l a i n c o n c r e t e , po lypropylene FRC, and steel FRC. Both t h e t e n s i l e s t r e n g t h and t h e pos t - c rack ing toughness are i n v e s t i g a t e d . The pos t - c rack ing toughness i s measured by means o f two toughness i n d e x e s . R e s u l t s show t h a t t h e t e n s i l e s t r e n g t h i n c r e a s e as t h e s l o t s e p a r a t i o n d i s t a n c e i s i n c r e a s e d . The t e n s i l e s t r e n g t h r eco rded f o r FRC mixes were independent of t h e f i b e r c o n t e n t . The toughness index r e s u l t s show t h a t t h e pos t - c rack ing toughness i n c r e a s e d w i t h i n c r e a s i n g f i b e r c o n t e n t . Comparison w i t h f l e x u r a l t e s t i n g shows t h a t t h e toughness i n t e n s i o n i s much less t h a n t h e toughness achieved d u r i n g f l e x u r a l t e s t i n g . The c o e f f i c i e n t of v a r i a t i o n w a s h igh .

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2179 . Barr, B . , and A . Bouamrata, "DEVELOPMENT OF A REPORTED DROP-WEIGHT IMPACT TESTING APPARATUS FOR S T U D Y I N G F I B E R

NO. 6, NOV 1988, pp. 453-466. REINFORCED CONCRETE MATERIALS," Composites, Vol. 1 9 ,

The paper descr ibes t e s t i n g procedures developed t o determine t h e impact r e s i s t ance of f i b e r re inforced concrete ma te r i a l s . R e s u l t s a r e presented (from experimental work using a repeated drop-weight impact apparatus) f o r t h e impact resistance of polypropylene FRC. Two drop he ights were adopted and f i v e impacting masses were inves t iga ted together with t h e e f f e c t of t h e span length . Further va r i a t ions of impacting height , impacting mass and support span values a r e poss ib le using t h e impact apparatus .

2180. Berglund, J . W . , "A MODIFIED DUAL-MASS AMPLIFIER FOR HIGH-STRAIN-RATE TESTING OF S I F C O N I N UNIAXIAL COMPRESSION," Experimental Mechanics, Vol. 28, N o . 3, Sept 1988, pp. 281-287.

An experimental procedure i s described f o r obtaining compressive s t rength data a t high r a t e s of s t r a i n f o r s l u r r y - i n f i l t r a t e d f i b e r concrete ( S I F C O N ) . A Monterey Research Laboratory dual-mass shock ampl i f ie r was modified t o apply shor t durat ion compressive loads t o c y l i n d r i c a l t e s t samples a t r a t e s of s t r a i n from 1 4 t o 35/s. The data obtained are compared t o data from s t a t i c compressive stresses a t lower peak s t r a i n s a s compared t o s t a t i c s t rength values .

2181. C u r r i e , B . , and T . Gardiner, "BOND BETWEEN POLYPROPYLENE F I B E R S AND CEMENT MATRIX," The In t e rna t iona l Journal of Cement Composites and Lightweight Concrete, Vol. 11, No. 1, Feb 1988, pp. 3-9.

The bond between a cementitious, f i b r i l l a t e d , and non- f ib r i l l a t ed polypropylene meshes has been inves t iga ted . Single tapes , mult iple tapes , and tapes a s p a r t of t h e m e s h have a l l been t e s t e d . I t i s concluded t h a t f o r woven meshes, f i b r i l l a t i o n i s unnecessary and both bond performances can be increased by sur face treatment of t h e tape . I n t h e work reported here, it was recognized t h a t t h e f i b e r diameter, bond s t rength , shape of f i b e r s , curing condi t ions and t h e age of t h e specimens a l l would have an e f f e c t on t h e bond s t r eng th . T e s t s were conducted on:

1. s i n g l e weft t apes . 2 . mul t ip le weft tapes without t h e warp t apes . 3 . m u l t i p l e weft tapes w i t h t he warp tapes ( i . e . r t h e

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mesh i t s e l f ) . The matrix had a 0 . 4 water t o cement r a t i o and an aggregate t o cement r a t i o of 1:l. The aggregates consis ted of f i n e s i l i c a sand.

2182. Kocataskin, F . , T . Ozturan, and H . Y . Ersoy, "COMPOSITE MATERIALS APPROACH FOR THE PREDICTION OF CONCRETE PROPERTIES," Bul le t in of t h e Technical University of Is tanbul , V o l . 4 1 , No. 2, 1988, pp. 333-347.

A composite mater ia l s approach has been appl ied t o t h e s t u d y and predic t ion of t h e mechanical p rope r t i e s of concrete . Models and a n a l y t i c a l expressions of t h e composite property r e l a t i o n s recorded i n l i t e r a t u r e f o r t h e modulus of e l a s t i c i t y and t h e mechanical s t r eng th of f i b e r re inforced composites and concrete a r e summarized. The semi-emperical Halpin-Tsai model f o r t h e modulus of e l a s t i c i t y and a new e f f i c i ency f a c t o r model developed by t h e authors f o r mechanical s t rengths have been appl ied t o t h e evaluation of systematic experimental r e s u l t s on normal weight and l ightweight concrete w i t h good agreement.

2183. Mangat, P . S., and K . Gurusamy, "LONG TERM PROPERTIES UNDER MARINE EXPOSURE OF STEEL FIBRE REINFORCED CONCRETE C O N T A I N I N G PFA," Materials and Structures, 1988, pp. 352-358.

T h e paper presents resu l t s of t h e long-term mechanical p rope r t i e s and d u r a b i l i t y under marine exposure of a s t e e l f ib re reinforced concrete (SFRC) mix containing pulverized f u e l ash (PFA) which was developed f o r marine appl ica t ions . The mix was of proport ions by weight of (PFA : OPC : F . A : C . A ) of ( 0 . 2 6 : 0 . 7 4 : 1 . 5 1 : 0 . 8 4 ) with a water t o (OPCtPFA) r a t i o of 0 . 4 . The r e s u l t i n g cement content of t h e mix was 435 kg/cu.m. The concrete was reinforced w i t h low-carbon, corrosion r e s i s t a n t (galvanized) s t e e l f i b e r s . P r i s m specimens were cured i n t h e t i d a l zone a t Aberdeen beach, under wet-dry cycles of sea-water spray i n t h e laboratory, i n a water-tank i n t h e laboratory, and i n t h e laboratory a i r . The specimens were cured f o r up t o 1200 marine cycles of exposure ( 6 4 0 days) and were t e s t e d a t regular i n t e r v a l s of age. T h i s paper presents r e s u l t s on t h e long term compressive s t rength , f l e x u r a l s t rength , and energy absorption capaci ty a s measured from t h e load-deflection curves. The s t a t e of corrosion of f i b e r s i s a l s o described.

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2184. Nanni, A , , "SPLITTING-TENSION TEST FOR FIBER REINFORCED CONCRETE," Materials J o u r n a l of t h e American C o n c r e t e I n s t i t u t e , V o l . 85, N o . 4 , July-Aug 1988, pp . 229-233.

The s p l i t t i n g - t e n s i o n t es t can be u s e d t o d e t e r m i n e t h e c h a r a c t e r i s t i c t e n s i l e parameters o f f iber r e i n f o r c e d c o n c r e t e (FRC) commonly o b t a i n e d w i t h t h e s t a n d a r d f l e x u r a l t e s t . F i r s t c r a c k and u l t i m a t e s t r e n g t h s , as w e l l as toughness i n d e x e s , are computed from t h e load-deformat ion diagram g e n e r a t e d w i t h a specimen/apparatus/procedure more conven ien t t h a n t h a t of f l e x u r a l or direct t e n s i o n tes ts . Exper imen ta l d a t a f o r d i f f e r e n t t y p e s and c o n t e n t s of s tee l f i b e r s are r e p o r t e d and FRC response, as o b t a i n e d from t h e l i t e r a t u r e f o r similar compos i t ions , i s shown.

2185. Narayanan, R . , and I . Y . Darwish, "FIBER CONCRETE DEEP BEAMS I N SHEAR," S t r u c t u r a l J o u r n a l of t h e American C o n c r e t e I n s t i t u t e , V o l . 85, N o . 2, M a r - A p r 1988, p p . 141-149.

R e s u l t s o f t e s t s on 1 2 r e i n f o r c e d c o n c r e t e deep beams i n c l u d i n g 11 c o n t a i n i n g s teel f i b e r s as web r e i n f o r c e m e n t are r e p o r t e d . Three parameters were varied i n t h e s t u d y , namely, t h e volume f r a c t i o n o f t h e f ibers , t h e s h e a r span-to-depth r a t io , and t h e c o n c r e t e compress ive s t r e n g t h . The e f f e c t o f f iber i n c o r p o r a t i o n on t h e d e f l e c t i o n , s t r a i n s , c r a c k wid th , c r a c k p a t t e r n , f a i l u r e modes, c r a c k i n g s h e a r l o a d , and t h e u l t i m a t e shear load were examined. Resistance t o shear stresses and s p a l l i n g were improved by t h e a d d i t i o n o f f i b e r s . Based on t h e s e i n v e s t i g a t i o n s , a rapid method f o r computing t h e u l t i m a t e s h e a r c a p a c i t y of s t e e l f i b e r r e i n f o r c e d c o n c r e t e deep beams w a s s u g g e s t e d .

2186. O t t e r , D . E . , and A . E . Naaman, "PROPERTIES O F STEEL F I B E R REINFORCED CONCRETE UNDER CYCLIC LOADING," Materials J o u r n a l o f t h e American Concre t e I n s t i t u t e , V o l . 85, N O . 4 , July-Aug 1988, pp. 254-261.

An e x p e r i m e n t a l program w a s conduc ted t o s t u d y h i g h and l o w s t r e n g t h f iber r e i n f o r c e d c o n c r e t e unde r c y c l i c compressive l o a d i n g . Three d i f f e r e n t f iber volume f r a c t i o n s and f o u r t y p e s of s tee l f ibers w e r e u s e d . C y c l i c l o a d i n g c o n s i s t e d of 1 0 % t o 90% of monotonic compressive s t r e n g t h , c o n s t a n t s t r a i n , and l o a d i n g t o a s p e c i f i e d s t r a i n . The enve lope c u r v e c o n c e p t w a s found t o a p p l y t o f i b e r r e i n f o r c e d c o n c r e t e j u s t as it d i d f o r p l a i n c o n c r e t e . Toughness under c y c l i c l o a d i n g w a s c a l c u l a t e d up t o a s t r a i n v a l u e e q u a l t o 0 .020 . R e s u l t s showed t h a t t h e p r e s e n c e o f f i b e r s d id n o t enhance t h e no rma l i zed cyc l i c s t r e s s - s t r a i n r e l a t i o n s h i p of t h e

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fiber r e i n f o r c e d mortar, n o r d id it improve t h e r e l a t i o n s h i p between un load ing , r e l o a d i n g , and p l a s t i c s t r a i n s .

2187. Ouyang, C. ,W. S u a r i s , and W . F . Chang, "EFFECT OF SULFATE ATTACK ON COMPRESSION PROPERTIES OF CEMENT-BASED MIXTURES CONTAINING PHOSPHOGYPSUM," Materials J o u r n a l o f t h e American Concre t e I n s t i t u t e , V o l . 85, N o . 2, M a r - A p r 1988, pp. 82-89.

R e s u l t s from a series of tes ts conducted t o d e t e r m i n e t h e e x t e n t of s u l f a t e a t t a c k i n cement based m i x t u r e s c o n t a i n i n g phosphogypsum are p r e s e n t e d . A model f o r t h e m i x t u r e s under i n t e r n a l s u l f a t e a t t ack i s proposed based on a p r o g r e s s i v e f r a c t u r i n g c o n c e p t . A damage var iable i s d e f i n e d as a f u n c t i o n of t h e Powers ' gel-space r a t i o . The s u l f a t e a t t a c k ev idenced by t h e expans ion of t h e m a t r i x i s i n c o r p o r a t e d as a d d i t i o n a l n u c l e a t e d v o i d s . The compress ive properties o f t h e cement-based m i x t u r e s c o n t a i n i n g phosphogypsum i s found t o be predicted w e l l by t h i s model.

2188. P u r k i s s , J . A , , "TOUGHNESS MEASUREMENTS ON STEEL F I B E R CONCRETE AT ELEVATED TEMPRATURES," The I n t e r n a t i o n a l Journal of C e m e n t C o m p o s i t e s and L i g h t w e i g h t Concre te , V o l . 10 , N o . 1, Feb 1988, pp. 39-47.

The r e s u l t s from a series of tes ts are p r e s e n t e d which e v a l u a t e v a r i o u s d e f i n i t i o n s of t h e t o u g h n e s s i n d e x . The t e s t s a l so e v a l u a t e t h e t o t a l f r a c t u r e e n e r g y and t h e r e s i d u a l f l e x u r a l t e n s i l e s t r e n g t h s of p l a i n specimens and specimens c o n t a i n i n g duoform and crimped s teel f ibe r s . These r e s u l t s i n d i c a t e t h a t t h e d e f i n i t i o n of t h e toughness indexes which r e l y on a r b i t r a r y l i m i t s w i l l n o t be c o n s i s t e n t , where as d e f i n i t i o n s which r e l y on r e l a t i v e d e f o r m a t i o n s g i v e a c o n s t a n t t o u g h n e s s i n d e x v a l u e f o r t he t e m p e r a t u r e r a n g e s t u d i e d . T h e duoform f iber r e i n f o r c e d c o n c r e t e specimens posed t h e h ighes t ene rgy a b s o r p t i o n r equ i r emen t d u r i n g f r a c t u r e . The ene rgy a b s o r p t i o n r equ i r emen t f o r p l a i n and crimped f iber r e i n f o r c e d mortars was lower. T h i s r equ i r emen t i n c r e a s e d w i t h t h e volume f r a c t i o n . The r e s i d u a l f l e x u r a l t e n s i l e s t r e n g t h s of both t h e p l a i n and t h e f iber r e i n f o r c e d c o n c r e t e mortars d e c r e a s e d w i t h i n c r e a s i n g t e m p e r a t u r e s .

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2189. Schneider , B . , "SIFCON: A NEW B U I L D I N G MATERIAL," C o n s t r u c t i o n S p e c i f i e r , V o l . 4 1 , No. 1 2 , Dec 1988, pp . 86-89.

SIFCON ( S l u r r y - i n f i l t r a t e d F i b e r C O N c r e t e ) i s a r e l a t i v e l y new material composed of s h o r t s t ee l f i b e r s i n a portland-cement-based m a t r i x . I t d i f f e r s from c o n v e n t i o n a l s t e e l - f i b e r - r e i n f o r c e d c o n c r e t e (SFRC) i n which t h e 8 t o 20% by volume of s teel f ibers are p r e p l a c e d and t h e f i b e r bed i s t h e n i n f i l t r a t e d w i t h a low v i s c o s i t y , c e m e n t i t i o u s s l u r r y , The r e s u l t i n g material p o s s e s s e s v e r y h igh compressive s t r e n g t h , toughness , and d u c t i l i t y . F l e x u r a l p r o p e r t i e s of SIFCON i s a l so enhanced ove r t h e normal SFRC mix.

2190. Shah, S. P . , D . L u d i r d j a , J . I . Danie l , and B . Mobasher, "TOUGHNESS-DURABILITY OF GLASS FIBER REINFORCED CONCRETE SYSTEMS," Materials J o u r n a l of t h e American Concre te I n s t i t u t e , V o l . 85, No. 5, Sept-Oct 1988.

Glass f iber r e i n f o r c e d p a n e l s are i n c r e a s i n g l y b e i n g used by t h e p r e c a s t i n d u s t r y f o r c l a d d i n g p a n e l s of new c o n s t r u c t i o n and f o r r e t r o f i t p r o j e c t s (1987 volume: 100 m i l l i o n d o l l a r s ) . The widespread development of GFRC h a s r e s u l t e d from t h e development of a l k a l i - r e s i s t a n t g l a s s f i b e r s which have an improved r e s i s t a n c e t o t h e a l k a l i n e environment t h a t e x i s t s i n port land-cement based matrices. I n s p i t e of t h e improved a l k a l i r e s i s t a n c e , long-term wea the r ing t e s t s revealed t h a t GFRC p a n e l s e x h i b i t reduced t e n s i l e s t r e n g t h and a loss of d u c t i l i t y w i t h a g i n g . The s t r e n g t h r e d u c t i o n i s c u r r e n t l y e x p l i c i t l y accounted f o r i n d e s i g n recommendations. For many a p p l i c a t i o n s of GFRC, d u c t i l i t y i s a t least as impor t an t as t h e s t r e n g t h ( e . g . , connec t ions , d i f f e r e n t i a l movements) i n de t e rmin ing t h e i r s e r v i c e l i v e s . Th i s rev iew pape r a d d r e s s e s some a s p e c t s of long-term d u r a b i l i t y of GFRC sys tems.

2 1 9 1 . Shanmugmat, N . E., and S . Swaddiwudhipong, "STRENGTH OF FIBER REINFORCED CONCRETE DEEP BEAMS CONTAINING OPENINGS," The I n t e r n a t i o n a l J o u r n a l of Cement Composites and Lightweight Concre te , V o l . 10 , No. 1, Feb 1988, pp . 53-60.

An e m p i r i c a l formula t o p r e d i c t t h e u l t i m a t e s t r e n g t h o f f i b e r r e i n f o r c e d c o n c r e t e deep beams c o n t a i n i n g openings i s proposed. Experiments have been c a r r i e d o u t t o s t u d y t h e e f f e c t o f t h e p o s i t i o n of openings and s h e a r span t o t h e e f f e c t i v e d e p t h r a t i o on t h e s t r e n g t h of such beams. The beams w e r e s imply suppor t ed and were t e s t e d a t two p o i n t l o a d i n g u n t i l

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f a i l u r e . R e s u l t s showed t h a t t h e u l t imate s t r eng th pr imari ly depends upon t h e e x t e n t t o which t h e opening i n t e r c e p t s t h e na tu ra l load path. The experimental f a i l u r e loads were compared w i t h those obtained by using t h e proposed empirical formula.

2192 . Wang, Y . , V . C . L i , and S . Backer, "MODELING O F F I B E R PULL-OUT FROM A CEMENT MATRIX," The In t e rna t iona l Journal of Cement Composites and Lightweight Concrete, Vol. 10, NO. 3, Aug 1988, pp. 143-149.

Theoret ical ana lys i s of f i b e r pu l lout from a matrix reported i n t h e l i t e r a t u r e were b r i e f l y reviewed. The e f f e c t s of Poisson 's r a t i o , e l a s t i c f r i c t i o n a l bond s t rength , and t h e bond s t rength va r i a t ion w i t h s l ippage d is tance on t h e pul lout r e l a t i o n were discussed. A t h e o r e t i c a l model motivated by observations of f i b e r surface abrasion was developed t o predict t h e pul lout force-displacement r e l a t ionsh ip . The model takes i n t o considerat ion t h e va r i a t ion of t h e fiber-matrix f r i c t i o n a l bond w i t h t h e f i b e r s l ippage d is tance . Good agreement was achieved between t h e t h e o r e t i c a l and experimental r e s u l t s f o r nylon and polypropylene f ibers . The bond s t rength was found t o increase w i t h t h e s l ippage d is tance dur ing t h e pull-out t e s t .

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1989

2193 . E z e l d i n , A . S., and P . N . Ba laguru , "BOND BEHAVIOR OF NORMAL AND HIGH-STRENGTH FIBER REINFORCED CONCRETE," J o u r n a l of t h e American Concre te I n s t i t u t e , V o l . 86, N o . 5, Sept-Oct 1989, pp. 515-524.

Expe r imen ta l r e s u l t s on t h e bond b e h a v i o r of normal and high s t r e n g t h c o n c r e t e made w i t h and w i t h o u t f ibers are reported. A t o t a l of 18 mix p r o p o r t i o n s were i n v e s t i g a t e d . The variables w e r e : (1) s i l i c a fume c o n t e n t , ( 2 ) f iber l e n g t h , ( 3 ) fiber c o n t e n t , and 4 ) bar s i z e . The s i l i c a fume c o n t e n t was varied from 0 t o 20% by weight of cement. S t e e l f ibers w i t h hooked ends were used i n t h e q u a n t i t i e s of 0, 50, 75, and 100 pcy. T h e f iber l e n g t h s and r e i n f o r c e m e n t bar s i z e s w e r e w e r e 30, 50, and 60 mm and W3, 5, 6, and 8 respectively. The bond tests were conducted u s i n g a modified p u l l - o u t t es t i n which t h e c o n c r e t e s u r r o u n d i n g t h e bar was under un i fo rm t e n s i o n .

2 1 9 4 . G a s p a r i n i , D . A . , D . V e r m a , and A. Abdallah, "POSTCRACKING TENSILE STRENGTH OF FIBER REINFORCED CONCRETE, 'I Materials J o u r n a l of t h e American Concre t e I n s t i t u t e , V o l . 86, N o . 1, Jan-Feb 1989, pp. 10-15.

A p robabi l i s t ic model for p r e d i c t i n g t h e e x p e c t e d v a l u e and t h e v a r i a n c e of t h e p o s t - c r a c k i n g t e n s i l e s t r e n g t h of f i b e r r e i n f o r c e d c o n c r e t e i s p r e s e n t e d . Fibers are assumed t o o c c u r as a spa t i a l P o i s s o n process. O r i e n t a t i o n of t he f ibers i s assumed t o be of three types : (1) randomly o r i e n t e d i n space, ( 2 ) randomly o r i e n t e d w i t h i n a prescribed p l a n e , and (3 ) f ibers a l l a l i g n e d a l o n g t h e a x i s . A n a l y t i c a l s t r e n g t h p r e d i c t i o n s are compared w i t h e x i s t i n g s t r e n g t h data and t h e model assumpt ions are c r i t i c a l l y d i s c u s s e d . I t i s concluded t h a t even w i t h t h e s i m p l i f y i n g a s sumpt ions made, t h e t h e o r e t i c a l p r e d i c t i o n s of t h e mean and v a r i a n c e of t h e p o s t c r a c k i n g s t r e n g t h agree v e r y w e l l w i t h t h e e x p e r i m e n t a l data of Naaman e t a l , and t h a t of L i m e t a l . I t i s p a r t i c u l a r l y meaningfu l t h a t a la rge c o e f f i c i e n t of v a r i a t i o n i s both a n a l y t i c a l l y p red ic ted and e x p e r i m e n t a l l y obse rved . Q u a n t i f y i n g s t r e n g t h v a r i a b i l i t y i s n e c e s s a r y f o r s e t t i n g r e s i s t a n c e f a c t o r s and e s t i m a t i n g member r e l i a b i l i t y .

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2195. Grzybowski, M . , and S . P . Shah, "SHRINKAGE CRACKING OF FIBER REINFORCED CONCRETE,I' A Report t o t h e NSF C e n t e r f o r Sc ience and Technology of Advanced Cement-Based Materials, J u l y 1989, pp. 1-35.

Tests were conducted u s i n g a r ing - type specimen t o s i m u l a t e r e s t r a i n e d sh r inkage c r a c k i n g . Using t h i s t y p e of specimen, t h e effect of two t y p e s of f ibers ( s t ee l and p r o l y p r o p y l e n e ) , s e v e r a l amounts of f i b e r s ( 0 . 1 % t o 1.5%), v a r i o u s age of c o n c r e t e ( 2 hours t o f o u r d a y s ) , d i f f e r e n t d r y i n g p e r i o d s (up t o s i x w e e k s ) , and a g iven su r round ing environment (40% RH and 20 degrees C ) were s t u d i e d . The r e s u l t s w e r e s a t i s f a c t o r y and w e r e compared w i t h a t h e o r e t i c a l model developed by t h e a u t h o r s .

2 1 9 6 . Lub, K . B . , and T . Padmoes, "MECHANICAL BEHAVIOR OF STEEL FIBER-CEMENT MORTAR I N TENSION AND FLEXURE, INTERPRETED BY MEANS OF STATISTICS," Materials J o u r n a l of t h e American Concrete I n s t i t u t e , Vol. 86, No. 1, Jan-Feb 1989, pp . 1 6 - 2 7 .

The behav io r of t h in -wa l l ed s t ee l f iber-cement i n u n i a x i a l t e n s i o n i s r e l a t e d t o i t s behav io r i n pu re f l e x u r e by means of s ta t i s t ics . The stress-crack width diagram of u n i a x i a l t e n s i o n can, by means of r e g r e s s i o n a n a l y s i s , be approximated by a s t r a i g h t l i n e , as w e l l as f o r t h e average upper and lower l i m i t s . With t h e s e data, a lower l i m i t moment-rotation diagram, which agrees w i t h t h e t e s t data, i s ana lyzed i n p u r e f l e x u r e fo r n i n e box beams. I t shou ld be no ted t h a t t h e l o a d d e f l e c t i o n diagram w a s conve r t ed t o a moment-rotation diagram. T o d e t e c t t h e i n f l u e n c e of f i b e r a l ignment , two t y p e s of box beams were made by v a r y i n g t h e f i b e r a l ignment i n t h e bottom f l a n g e . Although t h e t e s t resu l t s of t h e two t y p e s d i f f e r cons ide rab ly , a h y p o t h e s i s t e s t i n g showed t h a t t h e d i f f e r e n c e i n t h e behav io r o f t h e two t y p e s w a s n o t s i g n i f i c a n t .

2 1 9 7 . Naaman, A . E . , G . Nammur,H. N a j m , and J . Alwan, "BOND MECHANISMS I N F IBER REINFORCED CEMENT-BASED COMPOSITES, It A Report on Research Sponsored by t h e A i r Force O f f i c e of S c i e n t i f i c Research, Grant No. F49620-87-C-0063, Report N o . UMCE 89-9, Department of t h e C i v i l Engineer ing , The U n i v e r s i t y of Michigan, Ann Arbor, M I , 48109, Aug 1989, pp. 233.

The main o b j e c t i v e of t h i s r e s e a r c h i s t o i n v e s t i g a t e t h e v a r i o u s fundamental mechanisms of bond, g e n e r a t e a r e l a t e d comprehensive expe r imen ta l data base, and develop r a t i o n a l a n a l y t i c a l models t o d e s c r i b e bond i n f i b e r r e i n f o r c e d cement based

387

composi tes . A p a r t i c u l a r focus i s p l a c e d a t c h a r a c t e r i z i n g bond by a bond s h e a r stress v e r s u s s l i p r e l a t i o n s h i p . Such a r e l a t i o n s h i p i s c o n s i d e r e d t o be a c o n s t i t u t i v e p r o p e r t y of t h e i n t e r f a c e , and, f o r g iven c o n d i t i o n s , i s cons ide red t o be l o c a t i o n independent . I t i s a lso t h e o b j e c t i v e of t h i s r e s e a r c h t o better assess t h e s h e a r stress d i s t r i b u t i o n a l o n g t h e f i be r as w e l l as t h e d i s t r i b u t i o n of normal stresses i n t h e f i b e r and t h e m a t r i x .

2 1 9 8 . Namur , G . G . , and A. E . Naaman, "BOND STRESS MODEL FOR F I B E R REINFORCED CONCRETE BASED ON BOND STRESS-SLIP RELATIONSHIP," Materials J o u r n a l o f t h e American Concre te I n s t i t u t e , Vol. 86, No. 1, Jan-Feb 1989, pp . 45-57.

T h i s pape r deals p r i m a r i l y w i t h bond i n f i b e r r e i n f o r c e d c o n c r e t e . Beginning w i t h a b r i e f review of s t u d i e s on bond i n r e i n f o r c e d and p r e s t r e s s e d c o n c r e t e and a summary of a n a l y t i c a l models developed by d i f f e r e n t r e s e a r c h e r s , it t h e n moves on t o t h e bond i n f iber r e i n f o r c e d c o n c r e t e . A comparison between i n t e r f a c i a l p r o p e r t i e s of RC and FRC i s drawn, fo l lowed by a rev iew of t h e expe r imen ta l work t h a t h a s been done on bond i n FRC, as w e l l as t h e r e l a t e d major f i n d i n g s . An a n a l y t i c a l model of t h e bond s h e a r stresses a t t h e f i b e r - m a t r i x i n t e r f a c e i n a pu re t e n s i l e FRC specimen i s t h e n d e r i v e d . The model p r e d i c t s t h e s h e a r s t ress d i s t r i b u t i o n a l o n g t h e f i b e r - m a t r i x i n t e r f a c e , t h e s l i p d i s t r i b u t i o n , and t h e normal t e n s i l e stresses i n t h e f i b e r and t h e m a t r i x . The model presumes a knowledge of t h e bond stress v s . s l i p f o r t h e g iven m a t r i x and r e i n f o r c e m e n t . P e r f e c t a l ignment between t h e f i b e r s as w e l l as s q u a r e packing are assumed. The model i s f i n a l l y used t o p r e d i c t numer i ca l ly t h e bond s h e a r stress i n a g iven t e n s i o n composi te u s i n g a s p e c i f i c bond- s l ip c u r v e .

2 1 9 9 Pai l lere , A . M . , M . B u i l , and J. J. Se r rano , "EFFECT OF FIBER A D D I T I O N ON THE AUTOGENOUS SHRINKAGE OF SILICA FUME CONCRETE," Materials J o u r n a l of t h e American Concre te I n s t i t u t e , Vol . 86, No. 2 , Mar-Apr 1989, pp . 1 3 9 - 1 4 4 .

I t h a s been found e x p e r i m e n t a l l y t h a t ve ry h igh s t r e n g t h s i l i c a fume c o n c r e t e s undergo e a r l y c r a c k i n g when deformat ion i s r e s t r a i n e d . Th i s phenomenon which o c c u r s even when t h e c o n c r e t e i s p r o t e c t e d a g a i n s t any e v a p o r a t i o n i s a t t r i b u t e d t o an i n t e n s e autogenous sh r inkage of c o n c r e t e , because of i t s e x c e p t i o n a l l y low w / c r a t i o ( 0 . 2 6 ) . An a t t e m p t has been made t o c o r r e c t t h i s weakness of t h e material by adding s teel f ibers .

388

Two t y p e s o f hooked fibers ( r a t i o s o f l e n g t h mm t o diameter i n hundred th of mm) 30/60 and 50/50 and 0 . 8 % f iber volume were used. For e a c h t y p e o f f i be r , t h e optimum sand-aggrega te r a t io , g i v i n g maximum slump, w a s determined t o g e t h e r w i t h t h e bending , and compress ive s t r e n g t h s of t h e r e s u l t i n g mater ia l . The f i b e r c o n c r e t e s have a n au togenous s h r i n k a g e lower t h a n t h e r e f e r e n c e c o n c r e t e , a n d undergo c r a c k i n g a t a l a t e r age u n d e r r e s t r a i n e d d e f o r m a t i o n .

2200. Ramakrishnan, V . , G . Y . Wu, and G . Hosal l i , "FLEXURAL BEHAVIOR AND TOUGHNESS OF FIBER REINFORCED CONCRETES," T r a n s p o r t a t i o n Resea rch Board, 6 8 t h Annual Meet ing, Washington, D . C . , J a n 1989.

T h i s paper p r e s e n t s t h e r e s u l t s o f a n e x p e r i m e n t a l i n v e s t i g a t i o n t o d e t e r m i n e t h e b e h a v i o r and per formance c h a r a c t e r i s t i c s o f t h e most commonly u s e d f i b e r r e i n f o r c e d concrete FRC f o r p o t e n t i a l a i r f i e l d pavements a n d o v e r l a y a p p l i c a t i o n s . A comparative e v a l u a t i o n of t h e s t a t i c f l e x u r a l s t r e n g t h i s p r e s e n t e d f o r c o n c r e t e s w i t h and w i t h o u t f iber r e i n f o r c e m e n t f o r d i f f e r e n t t y p e s o f f i b e r s (hooked end s tee l , s t r a i g h t s teel , c o r r u g a t e d steel , and p o l y p r o p y l e n e ) . Four d i f f e r e n t f i b e r c o n t e n t s were u s e d (0.5%,1.0%, 1 . 5 % and 2 . 0 % by v o l u m e ) . The s a m e bas ic m i x proportion w a s used for a l l mixes . N o s i g n i f i c a n t d i f f i c u l t y w a s e n c o u n t e r e d i n p l a c i n g and f i n i s h i n g c o n c r e t e s w i t h less t h a n 1% by volume f o r a l l f ibers . The maximum q u a n t i t y o f hooked s teel f i b e r s added w i t h o u t c a u s i n g b a l l i n g w a s l i m i t e d t o 1% by volume. C o r r u g a t e d s t e e l f i b e r s per formed t h e best i n f r e s h c o n c r e t e , even a t h i g h e r f iber c o n t e n t s (2% by volume), where no s i g n i f i c a n t b a l l i n g , b l e e d i n g , o r s e g r e g a t i o n was observed. Higher q u a n t i t i e s of s t r a i g h t f i b e r s c a u s e d b a l l i n g a n d h i g h e r amounts o f hooked s t ee l f ibe r s e n t r a p e d c o n s i d e r a b l e amount of a i r . The a d d i t i o n of f i b e r s i n c r e a s e d t h e c r a c k i n g s t r e n g t h by 15%-90%. The s t a t i c f l e x u r a l s t r e n g t h w a s i n c r e a s e d by 15%-129%.

2201. Ramakrishnan, V.,G. Y . Wu, and G . Hosa l l i , "FLEXURAL FATIGUE STRENGTH, ENDURANCE LIMIT, AND IMPACT STRENGTH OF F I B E R REINFORCED CONCRETES," T r a n s p o r t a t i o n Research Board, 6 8 t h Annual Meet ing, Washington, D . C . , J a n 1989.

I n many a p p l i c a t i o n s , p a r t i c u l a r l y i n pavements , bridge deck o v e r l a y s , o f f s h o r e s t r u c t u r e s , t h e f l e x u r a l f a t i g u e s t r e n g t h and endurance l i m i t a re i m p o r t a n t d e s i g n parameters because these s t r u c t u r e s are d e i g n e d on t h e basis o f f a t i g u e load c y c l e s . T h i s p a p e r p r e s e n t s t h e r e s u l t s o f an e x p e r i m e n t a l i n v e s t i g a t i o n t o d e t e r m i n e t h e b e h a v i o r and per formance

389

c h a r a c t e r i s t i c s of t he most commonly used FRC subjected t o f a t igue loading. A comparative evaluat ion of f a t igue p rope r t i e s i s presented f o r concretes w i t h and without f o r d i f f e r e n t types of f i b e r s (hooked end s t e e l , s t r a i g h t s t e e l , corrugated steel , and polypropylene). Two d i f f e r e n t f i b e r contents w e r e used ( 0 . 5 % and 1 . 0 % by volume). The same bas i c mix proportion was used f o r a l l mixes. The t es t program i n c l u d e d t h e determination of t h e concrete f resh and hardened p rope r t i e s such a s slump, vebe time, inverted cone t i m e , a i r content, u n i t weight and concrete temperature. The addi t ion of t h e four types of f i b e r s caused a considerable increase i n t h e f l e x u r a l f a t igue s t r eng th and t h e endurance l i m i t f o r 4 mil l ion cycles, t he hooked end s teel f i b e r s providing the highest ( 1 4 3 % ) .

2 2 0 2 . Said, S . , and J . A . Mandel, "MICROMECHANICAL STUDIES OF CRACK GROWTH I N STEEL FIBER REINFORCED MORTAR," Mater ia ls Journal of t h e American Concrete I n s t i t u t e , V o l . 86 , No. 3, May-June 1989, pp. 225-235.

I n t h e research reported i n t h i s paper, a micromechanical f i n i t e element model is developed t o simulate t h e response of a t y p i c a l region of a f i b e r re inforced mater ia l load from t h e onset of load t o f a i l u r e . With t h i s model, mechanical behavior of FRC mater ia l s can be studied, a s t h e magnitude and d i s t r i b u t i o n of t he stresses i n t h e matrix, f ibers , and fiber-matrix in t e r f ace are ca l cu la t ed . With t h i s knowledge, an understanding can be gained a s t o why t h e composite behaves a s it does. The t y p i c a l region inves t iga ted w i t h t he model i n c l u d e s a crack f ron t and t h e f i b e r s nearest t o t he crack f r o n t . The f i b e r s neares t t o t h e crack f r o n t have t h e most inf luence on t h e crack t i p s t r e s s e s and crack growth. The modes of f a i l u r e considered a r e t e n s i l e f a i l u r e and crack growth i n t h e matrix mater ia l , f a i l u r e of t h e f i b e r s , and i n i t i a t i o n and crack growth along t h e matr ix-f iber i n t e r f a c e . The model i s general i n t h a t t he mechanical p rope r t i e s of t h e matrix, f i b e r s , and t h e f iber-matr ix i n t e r f a c e a s w e l l a s t h e geometry of t h e composite a r e i n p u t s t o t h e model. Side-cracked tension specimens w i t h two rows of accurately posi t ioned s teel f i b e r s were t e s t e d and analyzed w i t h t he model. The purpose of t h i s s t u d y was t o v e r i f y the model and t o s t u d y the mechanisms of f a i l u r e i n the f i b e r re inforced cementit ious mater ia l s .

390

2203. Wang, Y . , and S . Backer, "TOUGHNESS DETERMINATION FOR FIBER REINFORCED CONCRETE," The In t e rna t iona l Journal of Cement Composites and Lightweight Concrete, V o l . 11, No. 1, Feb 1989, pp. 11-19 .

Methods c u r r e n t l y used t o evaluate t h e toughness of f i b e r re inforced concrete (FRC) were reviewed. Parameters represent ing the f r a c t u r e ene rgy determined from t h e a rea under t h e load-displacement curve obtained from conventional laboratory tes ts were discussed. An improved toughness parameter was proposed based on t h e secant compliance ( the displacement-load r a t i o ) , r a the r than judging by t h e load o r displacement alone a s done i n t he conventional methods. The new parameter was shown t o represent t h e toughness p rope r t i e s of FRC i n a more cons is ten t manner than o the r s imi l a r methods when appl ied t o a wide range of idea l ized load-displacement curves. However, l i k e other toughness parameters determined from t h e a rea under the load-displacement curve, i t s u s e should be l i m i t e d t o comparisons among r e s u l t s obtained under t h e same t e s t condi t ions.

2 2 0 4 . Yin, W . S . , E . C . Su,M. A . Mansur, and T . T . Hsu, "BIAXIAL TESTS OF P L A I N AND FIBER CONCRETE," Materials J o u r n a l of t h e A m e r i c a n C o n c r e t e I n s t i t u t e , V o l . 8 6 , N o . 3, May-June 1 9 8 9 , pp. 236-243.

Randomly or ien ted s teel f ibrous and p l a in concrete p l a t e s 6 x 6 x 1 . 5 i n . were subjected t o b i a x i a l compression. The compressive s t r e s s e s were appl ied through b rush type loading p la tens t o e l imina te the f r i c t i o n a l s t r e s s e s between t h e concrete specimens and t h e p l a t ens . The t e s t program covered four p r i n c i p l e compression tes t r a t i o s from 0 t o 1 and s t e e l f i b e r s wi th 1" and 3 / 4 " lengths, and volume f r a c t i o n of 1% t o 2 % . S t a t i c s t rength , deformational c h a r a c t e r i s t i c s , and t h e f r a c t u r e mechanism were evaluated. T e s t r e s u l t s show t h a t f i b e r concrete possesses higher s t rength than p l a i n concrete u n d e r b i a x i a l compressive loading. The increase i s a s h igh a s 35% i n t h e case of t he 1" f i b e r l eng th , 2 % volume f r ac t ion , and a s t r e s s r a t i o of 0 . 2 . For un iax ia l compression however, t h e increase i n t h e s t r e s s due t o f i b e r addi t ion was i n s i g n i f i c a n t . Observations of f a i l u r e modes reveals t h a t s p l i t t i n g - t y p e f a i l u r e occurs i n p l a in concrete, b u t f a u l t i n g t y p e f a i l u r e i s the norm i n f i b e r concrete .

391

Absi, E . A C I C o m m i t t e e 544 A k i h a m a , S . A l e x a n d e r , D . A l l e n , H. G . Anderson, W . F . B a g g o t t , R . B a l a g u r u , P. N .

B a r r , B . G. B a t s o n , G. B a u s c h , D . B e r g l u n d , J. W. B o n z e l , J . B r a n d t , A. M . B u t l e r , J. E . C a n c h o , A . V . C h u a n g , T . C l a r k e , R . C r a i g , R . J. C u r r i e , B . D e l v a s t o , S . E l - R e f a i , F . E . E z e l d i n , A. S . Faiyadh, F . I . Fane l l a , D . A. Foote, R . G a s p a r h i , D . A . G h a l i b , M . A . G l i n i c k i , M. A. G o d f r e y , K . A. G o p a l a r a t n a m , V. S . G r a m , H . G r z y b o w s k i , M . H a n n a n t , D . J. H a s a b a , S . H i b b e r t , A. P . H i l l e r b o r g , A. H o f f , G . C . H o r n r i c h , J . R . H o u d e , J . Ibukiyama, S . J a m r o z y , Z . J i n d a l , R . L . Johns ton , C . D .

2098 2174, 2175 2039, 2099, 2100, 2 1 0 1 2 1 7 6 2102 2 0 4 0 2103 2104, 2105, 2106, 2141, 2142, 2143, 2177 2014, 2071, 2107 2 0 4 1 2073 2180 2042, 2108 2043 2015 2 1 0 9 2145 2146 2025, 2044, 2045, 2046, 2110, 2147 2 1 8 1 2 1 1 1 2112 2193 2113 2074 2148 2194 2008 2047 2 0 2 6 2114, 2149 2075 2195 2034 2048 2016 2076 2150, 2 1 5 1 2152 2153 2049 2154 2050, 2 0 5 1 2027, 2028, 2052, 2053, 2077

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Kagan, M. Z. Kasperkiewicz, J. Keer, J. G. Kobayashi, K. Kocataskin, F. Komlos, K. Kormeling, H. A .

Krenchel, H. Kukreja, C. B. Lankard, D. R. Li, V. C. Lim, T. Y. Liu, K. Lorentsen, M. Lub, K. B. Mandel, J. A . Mangat, P. S. Mansur, M. A . Mbaezue, J. I. Meyer, A. Mondragon, R. Morgan, D. R. Naaman, A. E.

Nakagawa, T. Nammur, G. G. Nanni, A. Narayanan, R. Nishioka, K. Nordin, A . Ohama, Y. Otter, D. E. Ouyang, C. Packard, R. G. Paillere, A . M. Patton, M. E. Paul, B. K. Purkiss, J. A . Rahimi, M. Ramakrishnan, V.

Raouf, Z. A . Ravindrarajah, S . R Rider, R. G. Robins, P. J. Roik, K. Rostasy, F. S . Rotondo, P. L. Sahloul, M. Said, S. Sakai, M.

2115 2001, 2002 2054, 2116 2029, 2035 2182 2003, 2117 2009, 2118

2155 2055 2056, 2119 2156, 2079 2 0 8 0 2120, 2 1 6 0 2081, 2059, 2 1 2 1 2122 2 1 6 1 2060 2061, 2197 2123 2124, 2184 2087, 2 0 1 0 2088 2030, 2129, 2187 2063 2199 2037 2017 2188 2004 2011, 2 2 0 1 2064 2065 2012 2089, 2167 2090 2 1 3 1 2 0 9 1 2202 2132

2057, 2058, 2078

2157, 2158, 2159

2196

2082, 2183 2083, 2084

2062, 2085, 2086, 2162, 2163,

2198

2125, 2126, 2127, 2164, 2185

2128 2 1 8 6

2018, 2019, 2165, 2166, 2200

2130

3 93

Schneider, B. Schrader, E. K. Schupack, M. Sellevold, E. J. Shah, S. P. Shanmugmat, N. E. Sharma, A. K. Sood, V. Soroushian, P. Stebbins, R. J. Suaris, W. Sundara Raja Iyengar, K. T. Swamy, R. N.

Taylor, M. A. Uomoto, T. Uyan, M. Visalvanich, K. Walkas, B. Wang, Y. Wei, S. Wu, G. Yerex, I1 L. Yin, W. S. Zollo, R. F.

2133, 2020, 2092 2134 2093, 2191 2135 2168 2169 2136 2067 2137 2005, 2033,

2068 2069 2138 2022, 2007 2171, 2139 2172, 2097 2204 2070,

2189 2066

2094, 2190

2006, 2013, 2021, 2031, 2032, 2095, 2096, 2170

2023, 2038

2192, 2203

2173

2140

3 94

\

Abrasion resistance Accelerated curing Accelerated tests Additives Admixtures Air content Air entrainment Air pavements Air void characteristics Airports Air-void Alkali restraint glass fibers App 1 i cat ions Aramid fibers Asbest 0s Autoclaving

Beams

Beam-to-column connections Bending

2175

2154

2190

2030, 2112, 2134, 2 1 4 1

2154

2105, 2175, 2177

2143

2173

2177

2172

2177

2190

2044

2100

2034, 2054

2103

2009, 2022, 2041, 2083,

2168, 2185, 2 1 9 1

2025, 2051, 2168

2006, 2008, 2009, 2011,

2017, 2019, 2021, 2027,

2030, 2036, 2041, 2045,

2048, 2050, 2059, 2065,

2099, 2101, 2104, 2111,

2120, 2125, 2128, 2130,

2134, 2135, 2136, 2140,

2143, 2145, 2147, 2157,

2159, 2162, 2165, 2166,

2183, 2185, 2188, 2191,

2199, 2200, 2 2 0 1

2141,

2015,.

2028,

2046,

2083,

2116,

2132,

2142,

2158,

2174,

2196,

395

Biaxial bending 2204

Biaxial compressive stresses 2204

Bond-slip relationship 2097 Bond strength 2062, 2068, 2097, 2099, 2114,

2124, 2127, 2139, 2160, 2181,

2192, 2193, 2198

Carbon fibers Cavitation Charpy test Chemical additives Chloride Collated fibers Columns Compacting Composite material Compression

Concrete compaction Concrete spalling Connections Construction Corrosion

Crack

2039, 2085, 2099, 2 1 0 1

2175

2016, 2048

2066

2 0 8 1

2070

2033, 2045, 2 0 5 1

2154

2 0 9 1

2011, 2019, 2020, 2068, 2082,

2090, 2099, 2100, 2106, 2110,

2113, 2117, 2128, 2129, 2134,

2136, 2138, 2140, 2143, 2152,

2157, 2161, 2162, 2165, 2175,

2180, 2183, 2185, 2186, 2187,

2199, 2204

2042

2167

2025, 2033, 2051, 2163, 2168

2010

2012, 2081, 2088, 2092, 2130,

2150, 2151, 2183

2013, 2014, 2023, 2038, 2048,

2076, 2094, 2098, 2119, 2141,

2145, 2149, 2155, 2156, 2170,

2178, 2181, 2185, 2195, 2200,

2202

396

Growth

Measurement

P ropaga t ion Width

Creep

C y c l i c l o a d i n g

Deep beams D e f l e c t i o n Degree of w o r k a b i l i t y Delayed c a s t i n g Descending b ranch Design methods Direct t e n s i l e t e s t Dowel c r a c k i n g

Drop weight Drying s h r i n k a g e

D u c t i l i t y

D u r a b i l i t y

Dynamic Loading

Modulus of e l a s t i c i t y

E la s t i c modulus Endurance l i m i t

Energy Absorp t ion

D i s s i p a t i o n

2013, 2014, 2038, 2094, 2145,

2148

2156

2013, 2076, 2094, 2119, 2202

2185

2082, 2102, 2121, 2153, 2174,

2177

2019, 2066, 2104, 2129, 2186

2 2 0 1

2059, 2120, 2185, 2 1 9 1

2006, 2048, 2116

2003

2065

2074

2080

2002, 2100

2096

2077, 2 1 7 9

2155

2020, 2025, 2033, 2054, 2060,

2086, 2093, 2132, 2147, 2159,

2168, 2203

2012, 2081, 2092, 2102, 2121,

2150, 2151, 2174, 2183

2048

2019

2 1 1 1

2 2 0 1

2013, 2016, 2024, 2027, 2033,

2054, 2072, 2118, 2183, 2181,

2188, 2203

2025

3 97

F a t i g u e tes ts

Fer rocement Fiber

Bund l ing C o n c r e t e poles Con ten t measurement D i s t r i b u t i o n Manufac tu r ing O r i e n t a t i o n P r o d u c t i o n P u l l - o u t R e i n f o r c e d columns R e i n f o r c e d c o n c r e t e pavements

F ib r i l l a t ed fibers

F i b r o - f e r r o c e m e n t F i n i t e e l e m e n t method

F l e x u r a l F a t i g u e Strength

Toughness F l y ash F r a c t u r e

Energy Mechanics Methods

Process zone Toughness

Freez- thaw

2009, 2011, 2051,

2165, 2166, 2 2 0 1

2 1 4 6

2095

2 1 3 1

2069

2065, 2108

2123

2001, 2108

2123

2149, 2139

2167

2063

2 1 4 0

2 1 4 6

2076, 2202

(see F a t i g u e ) (see Bending)

(see B e n d i n g ) 2111, 2154, 2 1 6 1

2005, 2013, 2016,

2038, 2043, 2076,

2094, 2107, 2109,

2118, 2119, 2148,

2170, 2178

2022, 2043, 2109,

2076, 2 1 4 9

2023

2038, 2119, 2148

2014, 2022, 2079,

2012, 2092, 2105,

2175

2066, 2151,

2022, 2023,

2079, 2093,

2110, 2114,

2149,

2110, 2188

2107

2151, 2174,

3 98

Glass f i b e r s

Gypsum

High speed photography High s t r a i n ra te High s t r e n g t h Hooked f i b e r s HRWR Hybrid

Fibers

Mixes Hydraulic a p p l i c a t i o n s

Impact

Inve r t ed cone t es t

J o i n t s

Latex

Law of mixtures

Lightweight concre te

Load-def l e c t i o n r e l a t i o n s h i p

Marine Environment

Exposure S t r u c t u r e s

Measurement of f i b e r content

Mechanical p r o p e r t i e s M e l t e x t r a c t f i b e r s Microconcrete

2003, 2086, 2034, 2102, 2138

2187

2040

2090

2103, 2111, 2147, 2186, 2193

2002

2141, 2143

2029

2029, 2048, 2128

2026

2016, 2118, 2019, 2020, 2031,

2040, 2048, 2067, 2077, 2090,

2138, 2179, 2 2 0 1 ( a l s o see U n i a x i a l i m p a c t ) 2 0 1 1

2025

2137

2169

2032, 2143, 2147, 2170

2116

2150, 2 1 5 1

2012, 2183

2 0 8 1

2069

2174, 2093

2130

2122

399

Microcracking Microsil ica Mix proportioning Mode I1 f rac ture Modulus

of e l a s t i c i t y of rupture

Moment-curvature Monotonic loading

Notched beams

One way s labs Optimization

P a r t i a l p res t ress ing P a r t i a l l y reinforced mortar

Pavements

Phosphogypsum P las t i c i ze r s Point load t e s t Poisson's r a t i o

Poles

Polymers

Polypropylene f i b e r s

Porosity Precast connections Probabi l i s t ic methods

2109, 2202

2134

2095

2079

2017, 2037, 2175, 2182

2019, 2100, 2101, 2106, 2110,

2 1 1 1

2157

2 1 2 9

2006

2146

2043

2 1 4 1

2004

2010, 2049, 2053, 2063, 2066,

2172, 2173

2187

(see superplasticizers) 2089

2192

2 1 3 1

2030, 2048, 2066, 2128, 2134,

2137, 2139, 2160

2014, 2024, 2029, 2054, 2062,

2070, 2071, 2085, 2086, 2097,

2111, 2121, 2140, 2153, 2166,

2178, 2179, 2181, 2192, 2 2 0 1

2109

2163 (a l so see connections) 2194

400

Process zone Pu l l -ou t t e s t

P u l s e v e l o c i t y Punching shear

R c u r v e R e s i s t i v i t y R e s t r a i n e d s h r i n k a g e t es t Ring specimen Rubber l a t e x

SECRBB t e s t S e g r e g a t i o n Shear

Shot Crete Shr inkage

SIFCON

S i l ica fume Slab

C u r l i n g Slump tes t S p a l l i n g

S p l i t t i n g t e n s i l e s t r e n g t h Steel f iber

Concre te

(see Fracture) 2094, 2127, 2139, 2149, 2160,

2169, 2192, 2193, 2198

2019, 2064

2033

2038

2048

2005, 2155, 2195

2195

2137

2107

2095

2006, 2025, 2033, 2050, 2051,

2055, 2059, 2064, 2071, 2083,

2096, 2120, 2125, 2135, 2141,

2142, 2144, 2158, 2164, 2170,

2185, 2 1 9 1

2018, 2060, 2073, 2088, 2093

2005, 2017, 2140, 2143, 2155,

2175, 2195, 2 1 9 9

2056, 2057, 2058, 2078, 2104,

2133, 2142, 2152, 2161, 2163,

2180, 2189

2104, 2141, 2142, 2153, 2199

2006, 2008, 2033, 2146, 2173

2173

2011, 2177

2168 (also see concrete spa11 ing) 2110, 2140, 2175, 2184

2002, 2004, 2008, 2009, 2010,

2011, 2021, 2025, 2029, 2030,

4 01

D i s t r i b u t i o n Mixes O r i e n t a t i o n

S t r e s s - s t r a i n r e l a t i o n s h i p S t i f f n e s s

S t r a i n Energy Hardening R a t e

S o f t e n i n g S u l f a t e a t tack S u p e r p l a s t i c i z e r s S y n t h e t i c f ibers

T e n s i l e Cracking F r a c t u r e behav io r S t r a i n S t r e n g t h

2032, 2037,

2045, 2046,

2052, 2053,

2060, 2063,

2069, 2162,

2077, 2080,

2085, 2087,

2093, 2096,

2110, 2111,

2118, 2122,

2145, 2150,

2172, 2173,

2188, 2191,

2042, 2065

2073

2042

2074, 2 1 5 6

2021, 2037,

2040,

2047,

2055,

2064,

2071,

2081,

2089,

2098,

2113,

2125,

2161,

2178,

2196,

2 1 6 0

2041,

2050,

2058,

2066,

2074,

2083,

2090,

2107,

2115,

2126,

2164,

2182,

2201,

2022

2002

2015, 2124

2145

2187

2111, 2112, 2137, 2154

2 1 7 1

2042,

20511,

2059,

206'7,

2075,

2084,

2091,

210l3,

211'7,

2131,

2170,

2184,

2202

2 0 0 6

(see Fracture) 2157

2007, 2039, 2043, 2068, 2076,

2099, 2100, 2102, 2109, 2110,

2114, 2115, 2124, 2139, 2142,

4 0 2

Torsion

Toughness

Index

Resistance Truss model

Ultimate flexural strength Uniaxial

Impact Tension

VeBe test

Water cement ratio Weathering Web opening Workability

Yield

2156, 2157, 2162, 2169, 2178,

2184, 2188, 2193, 2194, 2196,

2198, 2 1 9 9 (also see U n i a x i a l t e n s i o n and S p l i t t i n g t e n s i l e s t r e n g t h ) 2041, 2045, 2046, 2083, 2084,

2087, 2110, 2125, 2 1 2 6

2014, 2022, 2024, 2027, 2033,

2060, 2072, 2077, 2079, 2086,

2105, 2107, 2130, 2132, 2138,

2144, 2157, 2178, 2188, 2201,

2203

2013, 2027, 2072, 2074, 2111,

2144, 2157, 2079, 2200, 2203

2074

2087

(see F l e x u r e )

2118

2007

2 0 1 1

2 1 6 1

2102

2059

2003, 2011, 2032, 2052, 2068,

2095, 2112, 2143, 2154, 2175,

2165, 2166

2175

4 0 3

High Performance Concretes An Annotated Bibliography 1974-1989

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