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ACI 363.2R-11

Reported by ACI Committee 363

Guide to Quality Controland Assurance

of High-Strength Concrete

Guide to Quality Control and Assurance of High-Strength Concrete

First PrintingJuly 2011

ISBN 978-0-87031-703-3

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Guide to Quality Control and Assuranceof High-Strength Concrete

Reported by ACI Committee 363

ACI 363.2R-11

High-strength concrete (HSC) has emerged as a viable material to use asan alternative to conventional normal-strength concrete in infrastructuresystems to reduce member cross section, extend member span length,reduce the number of system members, or enhance system sustainability.This guide offers general information on the quality control and testing ofHSC. Recommendations are based on the current state of knowledgegained from worldwide experimental research, analytical work, and fieldapplications of HSC systems used in concrete structures.

Keywords: acceptance criteria; compressive strength; concrete placement;creep; curing; delivery; modulus of elasticity; sampling; shrinkage; statisticalconcepts; strength evaluation; testing; trial batching; quality assurance;quality control.

CONTENTSChapter 1—Introduction and scope, p. 2

1.1—Introduction1.2—Scope

Chapter 2—Notation and definitions, p. 22.1—Notation2.2—Definitions

Chapter 3—Planning, p. 33.1—Introduction3.2—Preconstruction meeting3.3—Trial batches3.4—Prequalification of concrete suppliers and precon-

struction testing

Chapter 4—Quality assurance and quality control, p. 6

4.1—Introduction

Ronald G. Burg* Neil. P. Guptill Mark D. Luther Bryce P. Simons*

Michael A. Calderone* William M. Hale Barney T. Martin Jr. Robert C. Sinn

James E. Cook* Jerry S. Haught Charles K. Nmai* Konstantin Sobolev

Daniel Cusson Tarif M. Jaber Clifford R. Ohlwiler Houssam A. Toutanji

Per Fidjestol Daniel C. Jansen Michael F. Pistilli* Dean J. White II

Seamus F. Freyne Anthony N. Kojundic Henry G. Russell* John T. Wolsiefer Sr.

Brian C. Gerber Federico Lopez Flores Michael T. Russell* Paul Zia

Shawn P. Gross* Mauricio Lopez Ava Shypula

Consulting members

Antoine E. Naaman Adel R. Zaki

Luc R. Taerwe

*Committee members who prepared this guide.

John J. Myers*

Chair

2 GUIDE TO QUALITY CONTROL AND ASSURANCE OF HIGH-STRENGTH CONCRETE (ACI 363.2R-11)

4.2—Concrete plant4.3—Delivery4.4—Placing4.5—Curing

Chapter 5—Testing, p. 85.1—Introduction5.2—Background5.3—Sampling5.4—Frequency of testing5.5—Compressive strength specimens5.6—Modulus of elasticity5.7—Shrinkage and creep5.8—Prequalification of testing laboratories

Chapter 6—Evaluation of compressive strength test results, p. 16

6.1—Statistical concepts6.2—Strength evaluation

Chapter 7—References, p. 177.1—Referenced standards and reports7.2—Cited references

CHAPTER 1—INTRODUCTION AND SCOPE1.1—Introduction

The cement and concrete industry’s interest in high-strength concrete prompted the American Concrete Instituteto form ACI Committee 363 in 1979. The mission of thecommittee was to study and report information on high-strength concrete (HSC). HSC is considered one type ofhigh-performance concrete (HPC) that is most often specifiedfor enhanced strength characteristics, although may also bespecified for its improved durability. ACI 363R was the firstdocument produced by this committee in 1984, andcontained significant information regarding material selec-tion, mixing and placing, inspection and testing, physicalproperties, structural design, economics, and examples ofapplications.

This guide is an extension of ACI 363R and presentsguidelines to facilitate the proper evaluation of HSC throughcorrect quality control (QC) and testing. HSCs may beproduced with innovative materials and procedures notcovered in this guide. This guide is not intended to restrictthe use of new or innovative QC practices or testing methodsas they become available or necessary. The user is cautionedthat this guide is for general usage only, and individualprojects may require additional QC and testing effort.

1.2—ScopeThis guide discusses QC and testing practices of HSC. HSC

usually is associated with structures that have been optimizedfor performance. Therefore, a high degree of confidence inconcrete quality should be achieved through the inspectionand testing process. This process can be conducted by theproducer and contractor as QC and by the owner or the owner’srepresentative as quality assurance (QA). Those involved inQC and testing need to know the unique characteristics of HSC

to better assist the architect/engineer in evaluating thestructure’s potential performance.

Concrete with a specified compressive strength of 10,000 psi(70 MPa) can be produced from local aggregates in all areasof the U.S. and Canada. When the specified strengthsubstantially exceeds that produced previously in a particularmarket area, special measures are necessary to make asuccessful progression to the use of the higher-strengthconcrete. This guide details those measures.

Because the definition of HSC has changed over the years,ACI Committee 363 defined a range of concrete strengths forits activities, as explained in ACI 363R. For the purpose of thisguide, HSC is defined as having a specified compressivestrength of 8000 psi (55 MPa) or greater, and it does notinclude polymer-impregnated concrete, epoxy concrete, orconcrete made with artificial normalweight and heavyweightaggregates. Changes in material properties, production andinspection techniques, or testing methods occur continuouslyfrom lower-strength to higher-strength concretes. Experienceshows that in most cases, the special measures recommendedin this guide should be applied for concrete with compressivestrength greater than approximately 8000 psi (55 MPa).

CHAPTER 2—NOTATION AND DEFINITIONS2.1—Notationfc′ = specified compressive strength of concrete, psi

(MPa)

2.2—DefinitionsACI provides a comprehensive list of definitions through

an online resource, “ACI Concrete Terminology,” athttp://terminology.concrete.org. Definitions provided hereincomplement that resource.

concrete, high-strength (HSC)—concrete that has aspecified compressive strength of 8000 psi (55 MPa) or greater.

quality assurance (QA)—actions taken by an organizationto provide and document assurance that what is being done andwhat is being provided are in accordance with the contractdocuments and standards of good practice for the work.

quality control (QC)—actions taken by an organizationto provide control and documentation over what is beingdone and what is being provided so that the applicable standardof good practice and the contract documents for the work arefollowed.

self-consolidating concrete (SCC)—is highly flowable,nonsegregating concrete that can spread into place, fill theformwork, and encapsulate the reinforcement without anymechanical consolidation. In general, SCC is concrete madewith conventional concrete materials and, in some cases, witha viscosity-modifying admixture (VMA). SCC has also beendescribed as self-compacting concrete, self-placing concrete,and self-leveling concrete, which all are subsets of SCC.

water-cementitious material ratio (w/cm)—the ratio ofthe mass of water, excluding that absorbed by the aggregate,to the mass of cementitious material in a mixture, stated as adecimal.

GUIDE TO QUALITY CONTROL AND ASSURANCE OF HIGH-STRENGTH CONCRETE (ACI 363.2R-11) 3

CHAPTER 3—PLANNING3.1—Introduction

QC and testing of HSC is more critical than it is fornormal-strength concrete because seemingly minor deviationsfrom specified requirements can result in major deficiencies inquality or test results. For example, it is well-documented(Carino et al. 1994) that compressive-strength test results aremore sensitive to testing conditions as the strength of theconcrete increases.

The quality of HSC is controlled by the quality anduniformity of the ingredients, and by the mixing, placing,and curing conditions. A high level of QC is very importantfor those involved in the production, testing, transportation,placing, and curing of the concrete. Careful consideration ofplacing restrictions, workability, difficulties during transpor-tation, field curing requirements, and the inspection andtesting process is required. Thorough planning and team-work by the inspector, contractor, architect/engineer, producer,and owner are essential for the successful use of HSC.

This chapter reviews critical activities before the start ofconstruction. A preconstruction meeting is very important toclarify the roles of the members of the construction team andreview the planned QC and testing program. Specialattention is required during the trial-batch phase to assurethat selected mixtures will perform as required under fieldconditions. Planning for inspection and testing of HSCinvolves giving attention to personnel requirements,equipment needs, test methods, and the preparation andhandling of test specimens. Additional general informationon the inspection of concrete is contained in ACI 311.4R.

3.2—Preconstruction meetingSmall variations in mixture proportions and deviations

from standard testing practices can have greater adverseeffects on the strength of HSC than on normal-strengthconcrete. Therefore, project participants should meet beforeconstruction to clarify contract requirements, discussplanned placing conditions and procedures, and review theplanned inspection and testing programs of the various parties.The effects of time, temperature, placing, consolidation, andcuring should be reviewed. Acceptance criteria for standard-cured test specimens, in-place tests, and core test resultsshould be established. The capabilities and qualifications ofthe contractor’s work force, the inspection staff, and thetesting and batching facilities should also be reviewed.

The preconstruction meeting should establish lines ofcommunication and identify responsibilities. It is especiallyimportant to review the procedures the inspector will followwhen noncompliance with contract requirements is found orsuspected. Such advance understanding minimizes futuredisputes and allows members of the construction team toparticipate in the quality process. Timely and accuratereporting is important. Arrangements should be made todistribute inspection reports and test data as soon as possible.Trial production batches should have established a workablemixture, but it may be necessary to make adjustments due tosite conditions such as changing weather. Because HSCrelies on a low water-cementitious material ratio (w/cm) for

strength potential, responsibility for field addition of waterand admixtures should be discussed and defined clearly. Theready mixed concrete producer is essential to that discussionbecause the producer is familiar with and responsible for theproduct. Individuals should be identified, such as theconcrete supplier’s QC personnel, who will have the authorityto add admixtures or water at the site. For verification that theconcrete provided conforms to established requirements,procedures should be established for documenting what,when, and how much was added to the concrete at the site.

3.3—Trial batchesData on some HSC mixtures used previously are given in

Tables 3.1 to 3.3. These data are provided only for guidance,and trial batches with local materials would supersede thesetables for specific projects. ACI 211.4R provides guidanceon proportioning some HSC mixtures.

Where historical data are not available, the developmentof an optimum HSC mixture requires a large number of trialbatches (Blick et al. 1974; Cook 1982). Materials andproportions should initially be evaluated in the laboratory todetermine the appropriate material proportions and theirrelative characteristics. Sufficient lead time should beallowed because high-strength mixtures containing fly ash,silica fume, or slag cement are often evaluated at 56 and90 days. After the work has been completed in the laboratory,production-sized batches are recommended because laboratorytrial batches sometimes exhibit strengths and other propertiesdifferent from those achieved in production. For instance,the efficiency of small laboratory mixers is much less thanthat of production mixers, which can affect the dispersionand performance of chemical admixtures and supplementarycementitious materials. Because HSCs usually contain bothchemical admixtures and supplementary cementitiousmaterials including silica fume, and a high volume ofcementitious materials, they tend to be stickier thanconventional concrete mixtures. Production trials can beused to establish optimum batching and mixing sequencesthat can reduce problems before the start of the project.Where truck mixing is used, the maximum load that can bemixed adequately should be determined, but practice has shownthat this usually is less than 90% of the truck’s rated mixingcapacity. Based on experience, batches of HSC smallerthan 4 yd3 (3 m3) should not be mixed in truck mixers.

3.4—Prequalification of concrete suppliers and preconstruction testing

Bidders should be prequalified before the award of asupply contract for concrete with a specified strength of10,000 psi (70 MPa) or higher, or at least 1000 psi (7 MPa)higher than previously produced in the market local to theproject. The implications of the project specifications,whether prescription- or performance-based, should be fullyunderstood by all bidders.

3.4.1 Trial batches—The complexity of the prequalificationprocess depends on local experience. Where the specifiedstrength has been widely produced for previous projects, areview of available test data may adequately measure


performance. When strength higher than previouslysupplied is specified, or where there is limited experience inthe supply of that strength of concrete, a more detailedprequalification procedure should be carried out. This shouldgenerally include the production of a trial batch of theproposed mixture proportions. The trial concrete should becast into monoliths representative of typical structural sizeson the project. Fresh concrete should be tested for slump, aircontent, and temperature. Hardened concrete should be

tested to determine compressive strength and modulus ofelasticity based on standard-cured cylinders and on coresdrilled from the monolith. Strengths of cores and standard-cured cylinders tested at the same age should be correlated.In massive elements, core strength may vary with distancefrom the surface due to different temperature histories.Therefore, relationships should be established for a specificcore depth. If cores need to be removed during construction,the correlation allows interpretation of core strength results.

Table 3.1—Composition of experimental concretes produced in a ready mixed concrete plant (CPCA 1995)

Mixture ingredients and concrete properties

Concrete type

Reference Silica fume Fly ash Slag + silica fume

w/cm 0.30 0.30 0.30 0.30 0.25

Ingredients

Water, lb/yd3 (kg/m3) 214 (127) 216 (128) 217 (129) 221 (131) 216 (128)

Cement ASTM Type II, lb/yd3 (kg/m3) 759 (450) 716 (425) 615 (365) 384 (228) 283 (168)

Silica fume, lb/yd3 (kg/m3) — 76 (45) — 76 (45) 91 (54)

Fly ash, lb/yd3 (kg/m3) — — 160 (95) — —

Slag, lb/yd3 (kg/m3) — — — 308 (183) 539 (320)

Dolomitic limestone ingredients

Coarse aggregate, lb/yd3 (kg/m3) 1850 (1100) 1870 (1110) 1880 (1115) 1870 (1110) 1850 (1110)

Fine aggregate, lb/yd3 (kg/m3) 1370 (815) 1370 (810) 1370 (810) 1350 (800) 1230 (730)

HRWR,* fl oz/yd3 (L/m3) 395 (15.3) 362 (14) 336 (13) 310 (12) 336 (13)

Slump

After 45 minutes, in. (mm) 4-1/4 (110) 7 (180) 6-3/4 (170) 8-3/4 (220) 8-1/4 (210)

Average compressive strength

At 28 days, psi (MPa) 14,360 (99) 15,950 (110) 13,050 (90) 15,230 (105) 16,530 (114)

At 91 days, psi (MPa) 15,810 (109) 17,110 (118) 16,100 (111) 17,550 (121) 18,280 (126)

At 1 year, psi (MPa) 17,260 (119) 18,420 (127) 18,130 (125) 18,420 (127) 19,870 (137)*High-range water-reducer for these mixtures was a sodium salt of a naphthalene sulfonate.

Table 3.2—High-strength concrete mixtures used for different projects (CPCA 1995)


Mixture No.*

1 2 3 4 5 6

w/cm 0.35 0.37 0.27 0.31 0.25 0.25

Ingredients

Water, lb/yd3 (kg/m3) 329 (195) 278 (165) 228 (135) 244 (145) 219 (130) 226 (134)

Cement, lb/yd3 (kg/m3) 851 (505) 760 (451) 843 (500) 531 (315) 865 (513) 701 (416)

Silica fume, lb/yd3 (kg/m3) — — 30 (15) 61 (36) 72 (43) 57 (34)

Fly ash, lb/yd3 (kg/m3) 101 (60) — — — — —

Slag, lb/yd3 (kg/m3) — — — 231 (137) — —

Coarse aggregate, lb/yd3 (kg/m3) 1740 (1030) 1740 (1030) 1850 (1100) 1900 (1130) 1820 (1080) 1850 (1100)

Fine aggregate, lb/yd3 (kg/m3) 1060 (630) 1260 (745) 1180 (700) 1260 (745) 1160 (685) 1200 (710)

Admixtures

Water reducer, fl oz/yd3 (L/m3) 25 (0.98) — — 23 (0.90) — —

Retarding admixture, fl oz/yd3 (L/m3) — 116 (4.50) 47 (1.80) — — 12 (0.450)

Air-entraining admixture, fl oz/yd3 (L/m3) — — — — — 3 (0.125)

High-range water reducer, fl oz/yd3 (L/m3) — 290 (11.25) 362 (14.00) 153 (5.90) 406 (15.70) 129 (5.00)

Average compressive strength

At 28 days, psi (MPa) 9430 (65) 10,000 (69) 13,490 (93) 12,040 (83) 17,260 (119) 10,880 (75)

At 91 days, psi (MPa) 11,460 (79) 12,620 (87) 15,520 (107) 13,490 (93) 21,030 (145) —*Mixture No. 1 = Water Tower Place, Chicago (1975); 2 = Joigny Bridge, France (1989); 3 = La Laurentienne Building, Montreal (1984); 4 = Scotia Plaza, Toronto (1987); 5 = TwoUnion Square, Seattle (1988); and 6 = Portneuf Bridge, Quebec (1992).


The monolith should also be instrumented to determine themaximum internal temperature and the temperature gradientsdeveloped throughout the cross section.

Qualified suppliers can be selected based on their successfulpreconstruction trials. After the start of construction, furthertrials are desirable to confirm the field performance of thesubmitted and accepted mixtures. Further testing may also berequired on full-scale mockups of structural subassemblagesto determine the potential for cracking problems, such as at theinterface between structural elements of different thickness.

Provisions in the project specifications for concrete with aspecified strength of 10,000 psi (70 MPa) or higher, or atleast 1000 psi (7 MPa) higher than previously supplied,should assign the concrete supplier responsibility for QC ofthe mixed concrete and its ingredients.

Variations in temperature and humidity during the projectmay adversely affect the characteristics of the concrete.Laboratory and field tests should be performed to evaluatethe effects of environmental conditions on the properties offreshly mixed and hardened concrete. In particular, slumploss between the batch plant and the project site should beevaluated to ensure adequate slump at the time of placing.During periods of high temperature or low humidity, it maybe necessary to adjust the concrete mixture using retardingor high-range water-reducing admixtures in varied dosagerates and addition sequences.

3.4.2 In-place strength—It is also useful to correlateaccelerated and in-place tests with standard cured cylindersfollowing the procedures in ACI 228.1R. The potentialstrength of concrete supplied to a site cannot be known toosoon. Any serious shortfall of in-place strength is betterdiscovered early rather than late. If in-place testing is to be

used, it is recommended that a correlation with standard-cured cylinders be made at the prequalification trials. ACI228.1R provides guidance on the limitations of various in-place test methods.

3.4.3 Air entrainment—For air-entrained mixtures, closecontrol of air content is required. The air content andresulting air-void system in the hardened concrete isparticularly important for HSC subjected to cycles offreezing and thawing under moist conditions. HSC in exteriorvertical members is usually not critically saturated withwater and has a w/cm below 0.4; therefore, air entrainment isnot required. When needed, HSC has excellent resistance tofreezing and thawing if it contains an appropriate volume ofair and an adequate air-void system. ACI 201.2R givesrequirements for total air content, and ACI 212.3R listsrequirements for air-void parameters for protection againstdamage from freezing and thawing. ACI 212.3R characterizesa satisfactory air-void system as having a spacing factor of0.008 in. (0.20 mm) or less and a specific surface of 600 in.2/in.3

[24 mm2/mm3]) or greater. Some HSCs, including concreteswith low air contents (less than 4%) and coarse air-voidsystems (spacing factors greater than 0.008 in. [0.20 mm])have proven durable in freezing and thawing environments(Philleo 1986). If an HSC does not have an air-void systemthat meets the recommendations of ACI 201.2R and 212.3R,its resistance to freezing and thawing and deicer scalingshould be evaluated by laboratory testing according toASTM C666/C666M and C672/C672M. Samples for thesetests should be obtained from concrete produced and placedin a manner consistent with anticipated field methods. Whilethere is some controversy among researchers as to exactlimits, it is believed that only concrete with an exceptionally

Table 3.3—Typical proportions in commercially available high-strength concrete mixtures (10,000 to 20,000 psi [70 to 140 MPa]) (Burg and Ost 1992)


Mixture number*

1 2 3 4 5 6

w/cm 0.280 0.287 0.290 0.220 0.231 0.320

Ingredients

Water*, lb/yd3 (kg/m3) 266 (158) 270 (160) 261 (155) 243 (144) 255 (151) 238 (141)

Cement, ASTM Type I, , lb/yd3 (kg/m3) 950 (564) 800 (475) 820 (487) 950 (564) 800 (475) 550 (327)

Silica fume, lb/yd3 (kg/m3) — 40 (24) 80 (47) 150 (89) 125 (74) 45 (27)

Fly ash, lb/yd3 (kg/m3) — 100 (59) — — 175 (104) 147 (87)

Coarse aggregate SSD†, lb/yd3 (kg/m3) 1800 (1070) 1800 (1070) 1800 (1070) 1800 (1070) 1800 (1070) 1890 (1120)

Fine aggregate SSD, lb/yd3 (kg/m3) 1090 (647) 1110 (659) 1140 (676) 1000 (593) 1000 (593) 1250 (742)

Admixtures

HRWR, Type F‡, fl oz/yd3 (L/m3) 300 (11.6) 300 (11.6) 290 (11.2) 520 (20.1) 425 (16.4) 163 (6.3)

HRWR, Type G‡, fl oz/yd3 (L/m3) — — — — — 84 (3.2)

Retarder, Type D, fl oz/yd3 (L/m3) 29 (1.12) 27 (1.06) 25 (0.97) 38 (1.46) 39 (1.50) —

Slump, in. (mm) 7-3/4 (195) 9-3/4 (250) 8-1/2 (215) 10 (255) 9-1/4 (235) 8 (205)

Average compressive strength of 6 x12 in. (152 x 305 mm) cylinders

At 28 days, psi (MPa) 11,400 (79) 12,840 (89) 13,330 (92) 17,250 (119) 15,520 (107) 10,600 (73)

At 91 days, psi (MPa) 12,550 (87) 14,560 (100) 13,920 (96) 19,120 (132) 17,310 (119) 12,850 (89)*Mass of total water in mixture including water in admixtures.†Maximum nominal aggregate size: Mixtures 1 to 5, 1/2 in. (12.5 mm); Mixture 6, 1 in. (25 mm).‡High-range water-reducer meeting ASTM C494/C494M requirements.


low w/cm (less than 0.21) and high compressive strength(greater than 20,000 psi [135 MPa]) is likely to be resistant tofreezing-and-thawing damage without air entrainment. This isrelated to a disconnected capillary structure resulting in alow porosity level for HSC. Most project specifications,however, require air entrainment in concretes exposed tofreezing and thawing, irrespective of strength level.

Achieving and maintaining a satisfactory air-void systemin high-workability mixtures that contain high-range water-reducing admixtures can be difficult, especially when theconcrete is placed by pumping (Lessard et al. 1996).Pumping over long distances with upward or downwardvertical runs can reduce the number of small air bubbles andincrease the number of larger ones. This can increase thespacing factor to an unacceptable value. Therefore, it isimportant that the air-void characteristics be evaluated onhardened samples taken at the point of placing the concrete.

3.4.4 Temperature considerations—Each HSC mixturehas unique heat evolution and heat dissipation characteristicsfor a particular curing environment. Maximum temperaturesand thermal gradients and their effects on constructibilityand long-term design properties should be determinedduring preconstruction trials. Computer simulation of thelikely thermal history can be used to establish appropriatecuring and protection (Roy et al. 1993). In addition,temperature-matched curing systems may be used to evaluatethe effects of temperature history on strength development(Wainright and Tolloczko 1983).

The higher cement contents of HSC may develop highinternal concrete temperatures and thermal gradients inexcess of 11°F/ft (20°C/m), especially in uninsulated massplacements. Burg and Ost (1992), however, showed thatthermal gradients were similar to those for conventional-strength concretes. Tests on 3 ft (1 m) square columns (Cooket al. 1992) showed lower cracking tendency in HSC due tothermal gradients because of the higher internal tensilestrengths at any given age. Burg and Ost (1992) showed thatin-place strength and stiffness were not adversely affectedwhere the maximum internal temperature during hydrationreached 172°F (78°C). Some guidelines, however, such asthe AASHTO “Load and Resistance Factor Design BridgeSpecification” (2006), currently limit the maximum concretetemperature to 160°F (71°C) for heat-cured concrete to limitthe potential for delayed ettringite formation (DEF). Thearchitect/engineer should understand the effects of heatgeneration in the various structural elements and addressthese in the project specifications (ACI 207.2R). Specificationsfor mass concrete often limit the temperature differencebetween the concrete interior and surface.

On a high-rise project in Seattle, Drake (1985) established amaximum acceptable differential of 40°F (22°C) between thecenter and exterior of a 6 ft (1.8 m) cube. On a high-rise projectin Montreal, Aïtcin et al. (1985) considered a gradient of 11°F/ft(20°C/m) to be acceptable. Ghosh and Bickley (1978) devel-oped a method of calculating the maximum temperature differ-ential to control cracking in the wall of the CN Tower. Atemperature differential of 36°F (20°C) was found to be accept-able for the 1.5 ft (0.5 m) thick walls.

CHAPTER 4—QUALITY ASSURANCEAND QUALITY CONTROL

4.1—IntroductionThe duties of QA/QC personnel should be defined clearly

in the contract documents. Comprehensive and timelyQA/QC permits confidence in the use of advanced designprocedures, frequently expedites construction, and improvesquality in the finished product. Conversely, the results ofpoor QA/QC can be costly for all parties involved. QA/QCpersonnel should be experienced with their respective duties,including the batching, placing, curing, and testing of HSC.QA/QC personnel should be able to provide evidence ofsuch training, experience, or both. Personnel in charge ofQA/QC programs should demonstrate capabilities at leastequivalent to certification as an ACI Concrete ConstructionInspector. Other QC personnel should demonstrate capabilitiesat least equivalent to certification as an ACI Concrete FieldTesting Technician—Grade I and Concrete Strength TestingTechnician.

This chapter reviews critical issues dealing with the qualityof HSC, and concludes with specific recommendations forincorporation of these concerns into the QA/QC program.Some of these recommendations are not unique to HSC, butrepresent good practice for quality concrete in general. Asmentioned previously, however, the quality of HSC can beaffected adversely if care is not exercised in all phases ofproduction, inspection, and testing.

4.2—Concrete plantQA/QC personnel should concentrate their efforts at the

concrete plant until consistently acceptable batching isachieved. Thereafter, spot checking the plant is recommendedunless the complexities of the project demand full-timemonitoring. In many cases, full-time inspection at thebatching facility is not necessary. Full-time inspection isrecommended for concretes with design strengths greaterthan 10,000 psi (70 MPa).

At the concrete plant, QA/QC personnel should ensurethat the facilities, moisture meters, scales, and mixers(central, truck, or both) meet the project specificationrequirements and that materials and procedures are asestablished in the planning stages. QA/QC personnel shouldbe aware of the importance of batching HSC, such as usingproper sequencing of ingredients, especially when pozzolansor slag cement are used. Scales, flow meters, and dispensersshould be checked monthly for accuracy, and should be cali-brated every 6 months. Moisture meters should be checkeddaily. These checks and calibrations should be documented.Plants that produce HSC should have printed records for allmaterials batched. Entries showing deviations from acceptedmixture proportions are provided with some plant systems.

The QC/QA inspector should be present at the batchingconsole during batching and should verify that the acceptedtypes and amounts of materials are batched. Batch weightsshould fall within the allowable tolerances set forth byproject specifications. The ASTM C94/C94M and NationalReady Mixed Concrete Association (NRMCA 2008) PlantCertification plans contain weighing tolerances applicable to


HSC production. These tolerances should be followed ifnot otherwise specified.

When not witnessing the entire batching operation,QA/QC personnel should perform or witness the followingtests at least once daily (or once per 8-hour shift).• Moisture content of fine and coarse aggregates in

accordance with ASTM C566.• Aggregate gradations (fine and coarse) in accordance

with ASTM C136.• Material finer than the No. 200 (75 μm) sieve in

accordance with ASTM C117.Moisture content tests should be repeated after rain and the

other tests should be repeated after deliveries of new batchesof materials.

HSC may rely on a combination of chemical admixturesand supplementary cementitious materials to enhancestrength development. Certain combinations of admixturesand portland cements exhibit different strength developmentcurves. Therefore, it is important for QA/QC personnel towatch for deviations in the type or brands of mixture ingredientsfrom those submitted and accepted. Substitutions should notbe allowed without the prior understanding of all parties.Reference samples of cementitious materials should be takenat least once per day or per shipment in case tests are neededlater to investigate low strengths or other deficiencies.

Sources of additional mixture water, such as wash water orany leftover concrete remaining in the truck drum beforebatching, should be identified. These should be emptiedfrom the truck before batching.

4.3—DeliveryHSC can be successfully mixed and transported in a

number of ways. The QA/QC personnel should recognizethat prolonged mixing will cause slump loss and result inlower workability. Adequate job control should be establishedto prevent delays. When practical, withholding some of thehigh-range water-reducing admixture until the truck arrivesat the job site or site-addition of high-range water-reducingadmixtures may be desirable. High-range water-reducingadmixtures with extended slump retention characteristicsmay preclude the need for job-site additions of admixture torecover slump. Truck mixers should rotate at agitation speedwhile waiting for discharge at the site. Failure to do so canlead to severe slump loss.

When materials are added at the site, proper mixing isrequired to avoid nonuniformity and segregation. QA/QCpersonnel should pay close attention to site mixing andshould verify that the mixture is uniform. ACI 304R containsinformation on proper mixing.

Truck mixers used to transport HSC should be inspectedregularly and certified to comply with the checklistrequirements of the NRMCA Certification of Ready MixedConcrete Production Facilities (NRMCA 2008). Truckmixers should be equipped with a drum revolution counter,and their fins should comply with NRMCA criteria.

The concrete truck driver should provide a delivery ticketthat contains the information specified in ASTM C94/C94M.

Every ticket should be reviewed by the inspector beforedischarge of concrete.

Chemical admixtures can be used to increase workabilitytime. High-range water-reducing admixtures are often usedto increase the fluidity of concrete for a definite time.QA/QC personnel should be aware of that period and shouldknow whether redosing with additional admixture ispermitted. If the batch is redosed, the amount of admixtureadded to the truck with a calibrated delivery system shouldbe recorded and the truck drum should be turned at least anadditional 30 revolutions at mixing speed. Therefore, thedelivery ticket should also provide a space for recording thefollowing information:• Water or admixtures added by authorized personnel at

the job site.• Approximate quantity of concrete in truck when

additional water or admixture is added.• Number of drum revolutions at mixing speed after the

addition of water or admixture.The addition of water at the job site should be permitted

only if this was agreed to at the preconstruction meeting andif the maximum specified w/cm is not exceeded.

4.4—PlacingPreparations at the project site are important. In particular,

the contractor should be ready for placing the first truckloadof concrete. QA/QC personnel should verify that forms,reinforcing steel, and embedded items are ready and that theplacing equipment and vibration equipment (includingstandby equipment) are in working order before the contractorplaces the concrete.

HSC is typically produced with slumps in excess of 8 in.(203 mm). Despite their fluid appearance, these mixturesrequire thorough consolidation (Fiorato and Burg 1991). Allconcrete should be consolidated quickly and thoroughly.Standby vibratory equipment is recommended, with at leastone standby vibrator for every three required vibrators. Theprovisions in ACI 309R should be followed for properconsolidation.

In construction, different strength concretes are oftenplaced adjacent to one another. QA/QC personnel should beaware of the exact location for each approved mixture. Whentwo (or more) concrete mixtures are being used in the sameplacement, it is mandatory that sufficient control be exercised atthe point of discharge from each truck to ensure that theintended concrete is placed as specified.

Many times, mushrooming is performed over column andshear wall locations when placing floor slabs; that is, HSC ismushroomed around those locations to form a cap beforeplacing lower-strength concrete around it in the slab. QA/QCpersonnel should be aware of how far the cap should extend.Because cold joints are not allowed between the twoconcretes, the inspector should determine that the high-strength mushroom is still plastic enough to blend with thelower-strength slab concrete. Planning is necessary todetermine the best procedures. Consideration should begiven to the use of retarding admixtures. The boundarybetween the HSC and lower-strength concrete should be


consolidated thoroughly by vibration. The inspector shouldmaintain field notes regarding mushroom placements so thatthere is a record of placement.

4.5—CuringThe potential strength and durability of HSC will be fully

developed only if it is properly cured for an adequate periodbefore being placed in service or being subjected toconstruction loading. Many acceptable methods for curingare available, as discussed in ACI 308R. HSCs, however, areextremely dense and impermeable. Therefore, appropriatecuring methods for various structural elements should beselected in advance. QA/QC personnel should verify that theaccepted methods are properly employed in the work.

HSCs usually do not exhibit much bleeding, and withoutprotection from loss of surface moisture, plastic shrinkagecracks have a tendency to form on exposed surfaces. Curingshould begin immediately after finishing, and in some cases,other protective measures should be used during thefinishing process. Curing methods include fog misting,applying an evaporation retarder, covering with polyethylenesheeting, or applying a curing compound.

Water curing of HSC is recommended because of the loww/cm employed. Klieger (1957) reported that concretes withlow w/cm benefited more by the application of additionalsurface water than concretes with high w/cm. Water curingof vertical members is usually impractical, and other curingmethods should be employed, such as leaving the forms inplace. For interior columns, additional curing after form-work removal is usually is not necessary because durabilityis not a problem. The period during which the forms are inplace may be adequate in such instances. When forms arereleased or removed at early ages (typically less than 1 day),prevention of thermal cracking should be considered byproviding insulation, particularly in cold weather.

The inspector should monitor and record ambienttemperatures and temperatures at the surface and center oflarge concrete components so that the design/construction teamcan effectively make any adjustments, such as changes inmixture proportions or the use of insulating forms, during thecourse of the project. Concrete delivered at temperatures thatexceed specification limits should be rejected unless alternativeprocedures have been agreed to at the preconstructionmeeting. The inspector should monitor that curing proceduresare according to project specifications, particularly those atearly ages, to control the formation of plastic shrinkage cracks.

CHAPTER 5—TESTING5.1—Introduction

Measurement of mechanical properties during constructionprovides the basic information needed to evaluate whetherdesign considerations are met and the concrete is acceptable.Experience indicates that the measured strength of HSC ismore sensitive to testing variables than is normal-strengthconcrete. Therefore, the quality of these measurements isvery important. Factors having little or no effect on tests of3000 psi (20 MPa) concrete can be significant on tests ofHSC, especially for compressive strength.

This chapter provides guidance on the special considerationsfor successful testing of HSC. The chapter begins withbackground information on compressive strength testing.This is followed by discussions of sampling, amount oftesting, and various details about test specimens.

5.2—BackgroundIn a research program on compressive strength testing of

HSC, Burg et al. (1999) pointed out, “The various ASTMstandards that prescribe the methods to cast, cure, preparespecimen ends, and test concrete specimens were developedbased on concretes with compressive strengths in the orderof 1500 to 6000 psi (10 to 41 MPa).” Researchers have longinvestigated various methods of determining compressivestrength and suggested different capping materials andmethods. Gonnerman (1924) studied the effects of cylinderend conditions on measured compressive strength usingvarious capping materials, such as beaver board, cork, lead,rubber, and white pine. The currently used sulfur-based caps,along with caps made from gypsum plaster, hydro stone, anddry shot, were investigated by Troxell (1942). Werner(1959) investigated the effects of rough cylinder ends beforecapping and end planeness requirements, and concluded thatfor compressive strengths exceeding 5000 psi (35 MPa), theprovisions of ASTM C192/C192M would require revision.

Henning (1961) concluded that steel cylinder molds werepreferable to waxed paper molds when testing concretes withstrengths over 5000 psi (35 MPa). Test standards, however,were not changed to reflect his recommendation.

Testing and acceptance standards based on past studiesmay not be applicable to HSCs that are now commerciallyavailable. Sanchez and Hester (1990) pointed out therequirement for strict attention to QC on projects incorpo-rating concrete with strengths of 12,000 to 14,000 psi (85 to100 MPa). Rosenbaum (1990) noted that the availability anddevelopment of higher-strength concrete had outpaced theupdating of testing practices to ensure reliable results.

Inadequate testing techniques and interlaboratoryinconsistencies have been found to cause more problemsthan have actually occurred with the concrete. Hester (1980)found differences in measured compressive strengthsbetween laboratories to be as high as 10%, depending on themixture and laboratories used. In a series of tests at fourlaboratories on cylinders from one load of HSC, differencesin measured strengths as high as 11% at 28 days wereobserved, as shown in Fig. 5.1. In that study, one laboratoryfabricated the cylinders and ground their ends. The cylinderswere subsequently shipped to the four laboratories fortesting, which was done under direct observation of theinvestigators. Thus, even when specimen fabrication is not avariable, wide variations in measured strengths can occur.

Kennedy et al. (1995) found that within-laboratory andbetween-laboratory standard deviation increased as the meancompressive strength of the concrete increased (Fig. 5.2). Inthat study, data were obtained from an interlaboratoryprogram that involved 15 laboratories, six mixtures, and fivereplicates per mixture. The data are compared with otherinterlaboratory studies in Fig. 5.3. The data from Detwiler


and Bickley (1993) were based on blind testing of a similargroup of laboratories and were not directly comparable to theinterlaboratory study. In the blind testing, laboratorypersonnel were not aware which specimens being testedbelonged to the interlaboratory program. The data by Gray(1990) were from another interlaboratory program in BritishColumbia.

Because of the inherent variability in measuring compressivestrength, ACI 214R and 318 caution against reliance on asingle test result. Adequate planning, with review ofpersonnel and laboratory qualifications and strict adherence tostandard procedures, should help prevent questions aboutthe quality of testing during construction. The laboratoryshould be accredited or inspected for conformance to therequirements of ASTM C1077. Field and laboratory testingpersonnel should be experienced and trained properly.They should have documented prior experience withHSC testing and have demonstrated the capabilitiesnecessary for certification as ACI Concrete Field TestingTechnician—Grade I and Concrete Laboratory TestingTechnician—Grade I, or equivalent.

5.3—SamplingAs discussed in Chapter 6, statistical methods are an excellent

means to evaluate HSC. For such statistical procedures to bevalid, the data (slump, unit weight, temperature, air content,and strength) should be derived from samples obtainedthrough a random sampling plan designed to reduce thepossibility that choice will be exercised by the testingtechnician. Random-number tables should be used to selecttrucks that will be sampled during the placing operations.The samples taken from a truck should represent the qualityof concrete supplied. Therefore, composite samples shouldbe taken in accordance with ASTM C172/C172M. Theyshould be combined and remixed to ensure uniformity beforetesting the properties of the freshly-mixed concrete orcasting test specimens. Random sampling, however, does

not replace the need to ensure that the first truckload ofconcrete conforms to the specifications.

These samples are representative of the quality of concretedelivered to the site, and may not truly represent the qualityof the concrete in the structure, which may be affected by siteplacing and curing methods. If additional test samples arerequired to check the quality of the concrete at the point ofplacement (as in pumped concrete), this should be establishedat the preconstruction meeting.

5.4—Frequency of testingTests for air content, unit weight, slump or slump flow,

and temperature should be made on the first truckload eachday to establish that batching is adequate. For self-consolidatingconcrete (SCC), ASTM developed standard test methods forslump flow (ASTM C1611/C1611M), passing ability

Fig. 5.1—Interlaboratory variation of measured compressivestrength based on data by Kennedy et al. (1995). (Note: 1 MPa= 145 psi.)

Fig. 5.2—Within-laboratory repeatability and between-laboratory reproducibility from interlaboratory programwith 15 laboratories (five replicates for each concretemixture), based on data by Kennedy et al. (1995). (Note:1 MPa = 145 psi.)

Fig. 5.3—Comparison of variability in three interlaboratorystudies, adapted from Kennedy et al. (1995). (Note: 1 MPa= 145 psi.)


(ASTM C1621/C1621M), and coarse aggregate segregation(ASTM C1610/C1610M). The coarse aggregate segregationtest method is not recommended for field use. For moreinformation on SCC, refer to ACI 237R and the PCI guide-line on SCC (PCI Self-Consolidating FAST Team 2003).

If adjustments are made to mixture proportions, the firsttruck after these changes have been made should be sampled.Subsequent tests should be performed on a random basis.When visual inspection reveals inconsistent concrete, itshould be rejected unless additional tests show it to beacceptable. Such test results should not be counted in thestatistical evaluation of the mixture unless they are made onrandom samples.

The architect/engineer can generally take advantage of thefact that HSC that contains fly ash or slag cement developsconsiderable strength at later ages, such as 56 and 90 days. Itis common to specify more test specimens than wouldnormally be required. The technician should be prepared totake a large enough sample to cast all test specimens. Underno circumstances should the technician use other samples totop off test specimens. If the sample is too small, the concreteshould be discarded, and another sample should be taken.Only a reasonable number of specimens, however, can bemade correctly within the correct time period for each sample.No more than nine specimens should be made per sampleunless sufficient personnel and facilities are available to handlethem properly. ACI 318-08, Section 5.6.2.4, (ACI Committee318) requires three specimens per test age if 4 x 8 in. (102 x203 mm) cylinders are used. ACI Committee 363 concurswith this recommendation for high-strength concrete andfurther recommends three specimens for each test age beused even if 6 x 12 in. (152 x 305 mm) cylinders are used.Holding three specimens in reserve is appropriate if laterage testing becomes necessary.

Where later ages are specified for acceptance purposes, itmay be desirable to make an early assessment of potentialstrength by testing early-age specimens or specimens withaccelerated curing.

5.5—Compressive strength specimensBecause much of the interest in high-strength structural

concrete is limited to compressive strength, thesemeasurements are of primary concern. The primary functionof standard laboratory-cured specimens is to provideassurance that the concrete mixture as delivered to the jobsite has the potential to meet contract specificationrequirements. The potential strength and variability of theconcrete can be established only by specimens made, cured,and tested under standard conditions.

5.5.1 Specimen size and shape—ASTM C31/C31M specifiesthe use of 4 x 8 in. (102 x 203 mm) cylinders when approvedby the engineer. The standard specimen is a cylinder with adiameter of 6 in. (152 mm) and a height of 12 in. (305 mm).This specimen size has evolved over the years from practicalconsiderations, and the design and construction team isfamiliar with the empirical values obtained. This specimensize may lead to practical problems when testing HSC becausethe crushing loads may exceed the capacities of available

testing machines. The use of 4 x 8 in. (102 x 203 mm) cylin-drical specimens has also been done successfully to determinecompressive strength (Forstie and Schnormeir 1981).

Cook (1989) indicated that for a mixture with a designstrength of 10,000 psi (70 MPa), the strengths of 4 in. (102 mm)diameter cylinders were approximately 5% higher than thoseof 6 in. (152 mm) diameter cylinders. Burg and Ost (1992)found that, in the range of 10,000 to 20,000 psi (70 to 140 MPa),4 in. (102 mm) diameter cylinder strengths were generallywithin approximately 1% of the 6 in. (152 mm) diametercylinder strengths. Carino et al. (1994) found that thedifferences were less than 2%.

The use of the smaller test cylinders is acceptable providedthat strength is determined in accordance with ASTMC39/C39M. Research by Burg et al. (1999) suggests thatwhere rigid upper platens are used, the test results for bothspecimen sizes are the same. Carino et al. (1994) suggestedthat the strength differences between the two cylinder sizesmay be related to differences in density. When 4 in. (102 mm)diameter cylinders have been used for QA/QC testing in theU.S., strength reductions have not been applied to themeasured strengths. This committee recommends the use of4 x 8 in. (102 x 203 mm) cylindrical specimens for thecompressive strength determinations of HSC.

Regardless of specimen size, the size used to evaluate trialmixture proportions should be consistent with the size specifiedfor acceptance testing, and should be acceptable to thearchitect/engineer. If necessary, the relationship between thecompressive strengths of the two specimen sizes can bedetermined at the laboratory or field trial stage using thetesting machine that will be used for the project.

5.5.2 Mold type—Molds should meet the requirements ofASTM C470/C470M. The type of mold material, the abilityto hold its shape, and its watertightness can have a significanteffect on measured compressive strength. Consolidation ismore effective with rigid molds. Rigid single-use plasticmolds with wall thicknesses of 1/4 in. (6 mm) or greater havebeen used successfully for 10,000 psi (70 MPa) concrete(Forstie and Schnormeir 1981). Plastic molds should have acap to maintain a circular shape. Close-fitting caps also canbe used to minimize loss of moisture. Flat caps should beavoided, as they deform the concrete surface. A domed capthat provides a clearance of at least 1/2 in. (13 mm) shouldbe used. In all cases, loss of moisture should be prevented.Even high-quality cardboard molds produce compressivestrength results approximately 13% lower than when steelmolds are used (Blick 1973). Therefore, cardboard molds arenot recommended. Because of these noted differences, themold type used for field specimens should be the same as themold type used to develop the design mixture.

5.5.3 Consolidation of test specimens—Test specimensshould be consolidated properly. Applicable ASTM C31/C31Mand C192/C192M procedures should be followed.

5.5.4 Field handling and initial curing—Proper fieldhandling and initial curing of compressive strength test speci-mens during the first 48 hours are important aspects for ensuringstandard conditions, because the later-age strength of concretespecimens can be sensitive to initial curing temperatures.


This committee recommends that for initial curing ofHSC, all test cylinders in the field, after molding andfinishing, be placed immediately in water saturated withcalcium hydroxide and maintained at a storage temperatureof 68 to 78°F (20 to 26°C) for a period of up to 48 hours inaccordance with Section 10.1 of ASTM C31/C31M (Pistilliet al. 1992). The tank curing temperatures should be moni-tored in the field with a maximum/minimum thermometer ora continuous temperature recorder. Guidelines for the use oftemperature recorders are provided in ASTM C511.

Chamberlin (1952) studied the effects of initial andsubsequent curing temperatures on the strength development ofnormal-strength concrete test cylinders. For specimens withnonstandard initial curing temperatures maintained for up to24 hours before standard laboratory curing at 73°F (23°C),he reported that at age 28 days and later, the test cylinderswith higher initial curing temperatures had lower strength;and at later ages, the strength was dependent on the initialtemperatures, but was only slightly affected by the length oftime this temperature was maintained.

There are indications that the later-age strength of HSCmay not be as sensitive to the early-age temperature as isnormal-strength concrete. For example, Aïtcin and Riad(1988) indicated that the early temperature rise due to hydrationof high-strength mixtures containing silica fume with a w/cmbelow 0.30 dramatically increases the 7-day strength withoutaffecting the 28-day strength. Those results were based ontest cylinders subjected to a temperature cycle similar to thatobtained in two large HSC columns.

The curing of HSC in a structural member normally variesfrom the curing of representative standard specimens fromsamples obtained in accordance with ASTM C172/C172M,and prepared and cured in accordance with ASTMC31/C31M. The internal temperature of the concretemember may greatly exceed the ambient temperature, whiletest specimens are cured at approximately 73°F (23°C).Although standard test specimens used to evaluate thepotential strength of the concrete may be cured at lowertemperatures than the in-place concrete, studies (Day1994) have shown that the 28-day strength of standard,laboratory-cured specimens is a good indicator of potentialstrength. Furthermore, design equations were developedbased on compressive strength determined by standard-curedcylinders and structural performance based on large-scalespecimens. If an accurate determination of the strength ina HSC component is required, temperature-matched curedtest specimens (Wainright and Tolloczko 1983) should beused instead of standard-cured test specimens.

An adequate working area for specimen fabrication and aninitial curing facility should be provided at the job site. It ismore difficult to maintain the proper initial curing temperaturewith HSC specimens than with lower-strength concretespecimens because of the higher heat of hydration. As aresult, the temperature of the field curing environment caneasily exceed the upper limit of 80°F (27°C) allowed byASTM C31/C31M. The curing environment can beimproved by providing ventilation around specimens and bysubmerging the specimens in temperature-controlled water

baths. The testing technician should monitor the ambientcuring temperatures in the field with maximum/minimumthermometers or continuous temperature recorders. Thesetemperatures should be reported with the strength test data.

Because work by Aïtcin and Riad (1988) established thatmaximum temperatures just below 80°F (27°C) duringhydration did not reduce ultimate strength, the ASTM limitof 80°F (27°C) appears to be an appropriate upper limit forstandard field curing. The 1994 edition of CSA A23.1requires initial (field) curing temperature for test cylinders ofconcretes with specified strengths of 10,000 psi (70 MPa) orhigher to be 73.5 ± 3.5°F (23 ± 2°C).

The use of in-place testing is recommended to determinethe adequacy of curing, form removal time, or when a struc-ture may be put into service. Techniques for in-place testingare discussed in ACI 228.1R. Field-cured cylinders,however, are appropriate in the precast industry and, if theyare to be used, the storage and handling of field-cured spec-imens should be discussed at the preconstruction conference.

5.5.5 Transporting to laboratory—Test specimens thathave been stored under water should be transported to thelaboratory between 1.5 and 5 days after casting. The technicianshould exercise caution to ensure that the specimens havegained sufficient strength to resist handling stresses beforeshipping to the laboratory. This is particularly importantwhen retarding or high-range water-reducing admixtures areadded. During transportation, the specimens should beprotected by adequate cushioning material to preventdamage from jarring, and should be protected from damageby freezing temperatures or loss of moisture.

5.5.6 Laboratory curing—Standard laboratory moist-curingafter initial standard curing at the job site should strictlyfollow ASTM C31/C31M.

5.5.7 Specimen preparation—ASTM C39/C39M requiresthat the ends of test cylinders be ground or capped so that theloading surfaces are plane to within 0.002 in. (0.05 mm).When HSC cylinders are capped, the thickness and strengthof the cap is more important than it is for lower-strengthconcrete. Gaynor and Wedding (1964), Saucier (1972), andLobo et al. (1994) investigated the effect of the thickness ofsulfur mortar caps on compressive strengths of normal-strength concrete and HSCs. A uniform cap thickness of1/16 in. (2 mm) or less was found to be necessary for HSC.Thicker caps result in reduced measured compressive strength.

Capping should comply with ASTM C617. Sulfur mortarswith 2 in. (50 mm) cube strengths between 8000 and 10,000 psi(55 and 70 MPa) at the time of testing are acceptable forHSC up to design strengths of 10,000 psi (70 MPa). Above10,000 psi (70 MPa), test strengths less than the actual strengthof the specimens may be obtained with greater variability in thetest results (Rosenbaum 1990). Due to friction between thecap and steel platen, the cap is confined, and has a higherstrength than the 2 in. (50 mm) cube strength. The beneficialeffect of confinement was demonstrated by Gaynor andWedding (1964), who reported that the compressive strengthof 2 in. (50 mm) diameter cylinders of capping compoundincreased as the height of the cylinder was reduced. Cappinghas been used successfully for strengths up to 17,000 psi


(117 MPa) provided that cap thickness is limited to 1/16 in.(2 mm) (Lobo et al. 1994). Not all capping materials,however, are satisfactory. For concrete strengths above10,000 psi (70 MPa), tests should be made to demonstratethe suitability of the capping material. Typically, cappedcylinders are tested and compared with cylinders preparedby end grinding. It appears that the compressive strength ofthe capping material may not be the only, or even the mostimportant, mechanical property; the elastic modulus may bejust as important. Further research is needed in this area.Without prior experience, testing of sulfur mortars beforeproduction testing of concrete is recommended to determineoptimum melting temperatures and the time after castingrequired to develop adequate strength. Specimens shouldnever be tested immediately after capping. ASTMC39/C39M requires at least 2 hours of waiting after capping;longer times may be needed for HSC (Lobo et al. 1994).Laboratory technicians should practice with the designatedcapping material to produce a consistent 1/16 in. (2 mm)thick cap. The ends of test cylinders should be sawn orground if necessary to produce uniformly thin caps. This isespecially important when the finished ends of cylinders arerough or are not perpendicular to the cylinder axis. Caps shouldbe sounded for air voids by tapping with a coin (ASTM C617)before testing. Hollow caps should be removed and specimensrecapped. Sulfur mortars should not be reused.

The problems associated with capping can be eliminatedby grinding the ends of test cylinders using equipment madefor that purpose. Pistilli and Willems (1993) suggested thatspecimen ends be ground to a planeness of 0.001 in. (0.025 mm)and 0.3 degrees perpendicularity for concretes exceedingdesign strengths of 10,000 psi (70 MPa). Cylinders withends prepared by grinding have less variable test results anda higher average strength for concrete stronger than10,000 psi (70 MPa).

Unbonded cap systems, composed of polymeric pads inrestraining rings (Fig. 5.1) have been used successfully onHSC up to 19,000 psi (130 MPa) (Pistilli and Willems 1993).Test specimens, however, should be carefully prepared so thatpoor end conditions do not have a negative effect on the testresults. ASTM C1231/C1231M tolerance requirements for theplaneness of ends should not be exceeded, and its otherrequirements should be followed. ASTM C1231/C1231Mdoes not permit the use of unbonded caps for acceptance

testing of concrete with strength above 7000 psi (50 MPa).The qualification testing procedure in ASTM C1231/C1231M,however, can be used during the trial batch stage todemonstrate whether an unbonded cap system is suitable forthe particular concrete. Because unbonded caps result inexplosive failures of test cylinders, even when high-capacitystiff testing machines are used, safety precautions should beused to avoid injury to laboratory personnel.

An alternative unbonded capping method using dry sand(Fig. 5.4) was introduced in France (Boulay and de Larrard1993; Boulay 1996). Similar procedures were explored inthe U.S. in the late 1920s (Carino et al. 1994). In thisapproach, a steel mold is used to hold dry sand. The cylinderis positioned in the sand using a jig similar to that used forcapping with sulfur. The sand is vibrated, and moltenparaffin is poured around the cylinder to keep the sand inplace while the other end is prepared in a similar fashion.The compressive strength of cylinders tested using the sandbox system was found to be from 0 to 5% lower than groundcylinders, depending on strength level. The method wasadopted as a standard in France.

5.5.8 Testing apparatus—Due to the higher loads carriedby HSC test specimens, compression machine characteristicsinfluence results (Noguchi and Tomosawa 1996). Machinecharacteristics that can affect the measured strength includecalibration accuracy, longitudinal and lateral stiffness, andalignment of the machine components, type of platens, andthe behavior of the platen spherical seating. Testing machinesshould meet the requirements of ASTM C39/C39M. Based onpractical experience, it is recommended that the machineshould have a load capacity at least 20% greater than theexpected ultimate load of the cylinders. Premature damage totesting machines and loss of calibration has occurred becauseof large numbers of explosive failures at high loads. Testingmachines should incorporate devices to protect personnelfrom concrete fragments that may be propelled duringexplosive failures.

Carino et al. (1994) summarized the desirable stiffnesscharacteristics of testing machines:

Testing machine stiffness is an important factor incompressive strength testing. The effect of longi-tudinal stiffness on the post-peak response isunderstood, and hard machines are needed to avoid

Fig. 5.4—Unbonded cap systems: (a) polymeric pads restrained by metal ring; and(b) sand in rigid metal container (Boulay and de Larrard 1993; Boulay 1996).


explosive failures. On the other hand, the effect oflongitudinal stiffness on strength is not understood.There are conflicting opinions and data, so additionalstudy is warranted. The effect of lateral stiffness onstrength is understood. A laterally stiff machineassures uniform straining of the specimen in thepresence of eccentric loading, due to eitherheterogeneity of the specimen or misalignment. Theadequacy of the lateral stiffness can be evaluated bya proving device that measures the uniformity ofstraining as a function of degree of misalignment.

British Standard BS 1881, Part 115, (British StandardsInstitute 1986) describes one procedure for evaluating thelateral stiffness of testing machines. A metal tube instrumentedwith strain gauges is positioned between the loadingplatens at different amounts of eccentricity, and the straingauge readings are recorded. A laterally stiff machine canmaintain uniform deformation of the tube with increasingeccentricity of the tube.

The use of proper platen size and design is critical. Theupper platen should have a spherically seated bearing blockthat is able to rotate and achieve full contact with the specimenunder initial load. To ensure uniform compression of the testspecimen, however, the block should be fixed whenapproaching the ultimate load. The spherical bearing blockand seating should be kept clean and coated thinly with lightoil. The block will not become properly fixed if pressure-type greases are used.

Figure 5.5 shows the ASTM C39/C39M dimensionalrequirements for the spherically seated platen of a compression-testing machine. Laboratories typically use the same platenfor testing 4 and 6 in. (102 and 152 mm) diameter cylinders.Work by Burg et al. (1999) indicates that load transfer fromspherically seated platens into test specimens can affect themeasured strength. Some platens that meet the dimensionalrequirements of ASTM C39/C39M produce nonstandardload transfer into high-strength 6 in. (152 mm) diameterspecimens, but can transfer load properly for 4 in. (102 mm)specimens. This may explain cases where 4 in. (102 mm)cylinders have higher measured compressive strengththan 6 in. (152 mm) cylinders. In those cases, the smaller-diameter specimens may actually represent a more realisticmeasure of the compressive strength.

Figure 5.6 shows the key dimensions of two sphericallyseated bearing platens used in an interlaboratory studyconducted by Burg et al. (1999) to examine the effects oftesting variables on the measured strengths of high-strengthcylinders. Both platens satisfied the minimum dimensionalrequirements of ASTM C39/C39M; however, one platen hada smaller ball radius and a thinner bearing plate. In addition,the smaller platen had a two-part bearing plate as shown inFig. 5.6(b). In that study, a unique sensor system was used tomeasure the contact stresses between the platens and ends ofa 6 in. (152 mm) diameter aluminum cylinder. The sensorsystem allowed comparison of the cylinder end stressdistributions. Schematics of the measured distributions areshown in Fig. 5.6. It can be seen that the smaller spherically-

Fig. 5.5—Dimensional requirements for spherically-seatedplaten according to ASTM C39/C39M.

Fig. 5.6—Dimensions of: (a) adequate; and (b) inadequatespherically-seated bearing blocks and approximate shapestress distributions on ends of cylinders (Burg et al. 1999).(Note: 1 mm = 0.394 in.)


seated block resulted in a concentration of the stress at thecenter of the cylinder, whereas the larger and stiffer blockshowed the expected distribution with higher stress at theperimeter. Thus, the two blocks resulted in drasticallydifferent distributions at the end of the 6 in. (152 mm) diametercylinder. Figure 5.7 shows the reduction in measuredcompressive strength of 6 in. (152 mm) diameter cylinderstested with the less stiff spherically seated platen comparedwith cylinders tested with the stiffer platen. The adverse effectof the inadequate platen increased with increasing concretestrength. This study concluded that spherically seated platenswith large ball diameters and thick bearing plates should beused for testing 6 in. (152 mm) diameter cylinders.

Correct positioning of the specimen is crucial to uniformand accurate results. The permissible eccentricity of the testspecimen depends on the lateral stiffness of the testingmachine. To determine the criticality of specimen positioningfor a particular testing machine, an aluminum cylinder thesame size as the proposed test cylinders and instrumentedwith three strain gauges at midheight can be used. Thecylinder is placed in the testing machine and loaded to theanticipated concrete cylinder failure load. Strain readingsfrom each gauge are recorded as the aluminum cylinder isloaded. If the specimen is properly positioned, strain readingsshould be nearly identical around the periphery of thealuminum specimen. If not, the specimen can be repositioned,and the loading repeated. Once an acceptable location isdetermined, it should be marked so that actual test specimenscan be positioned properly.

Testing procedures and the condition and calibration of themachine should be investigated if compressive strengthresults are lower than expected or highly variable.

5.6—Modulus of elasticityThe modulus of elasticity is an important property that

often needs to be determined for HSC applications; however,there are no significant differences in the testing of HSC formodulus of elasticity compared with normal-strength

concrete. When specified, the modulus of elasticity shouldbe measured according to ASTM C469/C469M. The use of6 x 12 in. (152 x 305 mm) test cylinders is preferred.However, 4 x 8 in. (102 x 203 mm) test cylinders areacceptable. It is preferred to use a continuous electronicrecording of the stress-strain data during the test rather thanvisually reading a dial or a digital gauge. Particular attentionshould be given to the setup of the compressometer accordingto ASTM C469/C469M to obtain accurate test results.

5.6.1 Dynamic modulus of elasticity—It may be more costeffective to substitute dynamic modulus of elasticity testing(ASTM C215) for a portion of the static modulus tests,particularly when the modulus requirements are specified asan acceptance criteria for the material supplied. Thedynamic modulus and transverse frequency (ASTM C215)are higher than the static modulus determined by ASTMC469/C469M. Standard linear regression plots should bedeveloped during the preconstruction testing phase tocorrelate the static to the dynamic results. It is not recom-mended to use 4 x 8 in. (102 x 203 mm) cylinders fordynamic modulus testing; only 6 x 12 in. (152 x 305 mm)cylinders give reasonable correlation results.

5.7—Shrinkage and creepFor long-span bridges and tall high-rise buildings, time-

dependent deformations are important design considerations.The accuracy of the predicted deformations can be improvedby using measured values of creep and shrinkage of theconcrete to be used in the structure. Consequently, specifica-tions sometimes include requirements for creep andshrinkage of the HSC mixtures that may be required for thesestructures. In such instances, testing during development ofthe concrete mixtures is typically required to ensure that thespecified performance property can be attained beforeapproval of the mixtures and the start of construction. Theresults of such testing are used, for example, in the long-termvertical shortening and load distribution predictions for tallbuildings. Other applications that may require creep andshrinkage testing include offshore structures, mass concretepours, prestressed concrete structures, and elevated ordepressed temperature environments. Creep and shrinkagetesting should preferably be correlated and performed in tandemwith modulus of elasticity and compressive strength testing.

5.7.1 Shrinkage—When specified, shrinkage testingshould be performed in accordance with ASTMC157/C157M. The size of the shrinkage test prism and anydeviations from the standard 28-day period of moist curingor reference age for the initial measurement detailed inASTM C157/C157M can be specified, if desired. Preferably,shrinkage testing should extend over a period of 1 year to permitdata-fitting and extrapolation to predict ultimate shrinkagestrain using the form of the ACI 209R equation or othersuitable method. Very few commercial testing laboratorieshave the specimen molds, controlled temperature andhumidity environments, and expertise required for shrinkagetesting. Therefore, caution should be exercised in choosing atesting laboratory for shrinkage testing.

Fig. 5.7—Effect of spherically-seated platen on measuredcompressive strength of 6 in. (150 mm) cylinders as a functionof concrete strength (Burg et al. 1999). (Note: 1 MPa =145 psi.)


5.7.2 Creep—When specified, creep testing should beperformed in accordance with ASTM C512/C512M. In thistest, time-dependent strains are measured on concrete cylindersloaded in compression. The stress level on the specimens ismaintained constant at a value not to exceed 40% of theconcrete compressive strength at the age of loading. Up tothe 40% level, creep strain is taken as proportional to thestress level. Creep testing is expensive and requires specialequipment that is only available at a few commercial testinglaboratories and some universities. Therefore, it should onlybe specified when necessary. Any deviations from thestandard procedure should be clearly spelled out in theproject specifications.

ASTM C512/C512M requires drying shrinkagemeasurements on companion unloaded cylinders so that theshrinkage strains can be subtracted from the strainsmeasured on the loaded cylinders. It is important that theshrinkage and creep cylinders be the same size and be handledand stored identically from time of casting until the end of thetest; otherwise, they can have different properties, and a distor-tion of the test results will occur. It should be noted that theshrinkage measurements on the companion cylinders do notrepresent a standard drying shrinkage test. In addition, becauseshrinkage measurements are not required to begin until the testcylinders are loaded, both the companion and loaded cylinderswould have experienced shrinkage before the start of strainmeasurements.

The standard specimen required by ASTM C512/C512Mis a 6 in. (152 mm) diameter cylinder with a length of at least11.5 in. (290 mm). Typical creep frames are capable ofstressing a 6 in. (152 mm) diameter cylinder to approximately2500 psi (17 MPa). This means that the compressive strengthof these cylinders cannot be more than 6250 psi (43 MPa) ifstressed to the 40% level. If stressed to a lower level, themagnitude of the time-dependent strains is less and themeasured data are less accurate. It is recommended that thestress level be not less than 20% of the compressive strengthat the age of loading. Consequently, for concrete compressivestrengths greater than 12,500 psi (86 MPa), it is necessary touse special high-strength frames. To avoid this limitation,project specifications sometimes permit the use of 4 in. (102mm) diameter specimens. Smaller specimens have thedisadvantage of being more difficult to align in the creepapparatus. If 4 in. (102 mm) diameter cylinders are used, it isrecommended that they have a length of at least 8 in. (203mm), but not shorter than a length equal to the gauge lengthof the measuring device plus 1.5 in. (38 mm).

End preparation of creep cylinders is extremely importantto facilitate concentric loading and elimination of high spots.ASTM C512/C512M permits the use of capping, lapping, orfitting end plates normal to the axis of the cylinder at the timeof casting. For HSC, the use of lapping is recommended.

The standard age of loading is 28 days. Other loading ages,however, are permitted. For creep of concrete used inprestressed concrete beams, an age of loading correspondingto the age when the strands are released is appropriate,although logistics may make this difficult to achieve. Forcreep of concrete used in columns of high-rise buildings, an

age later than 28 days may be more appropriate. When thecomplete creep behavior of a concrete is needed, specimensshould be loaded at ages of 2, 7, 28, 90, and 365 days.

ASTM C512/C512M requires that the test continue for1 year after loading. In addition to providing more reliabledata, this test duration permits data-fitting and extrapolationto predict ultimate specific creep using the form of theACI 209R equation or other suitable method. In manyconstruction projects, however, this duration is too longand, consequently, earlier ages for reporting data arespecified. All tests should continue for at least 90 daysafter loading for usable results. Creep strain may be reportedas specific creep (creep strain/stress) or creep coefficient (creepstrain/initial elastic strain). If loading of the creep specimens isnot accomplished expeditiously, some creep may occur beforethe first reading after loading is obtained. This results in themeasured elastic strain being larger and the creep strain beingsmaller than it really is and distorts the creep coefficient morethan the specific creep. ASTM C512/C512M suggests that themethod of least squares be used to determine the initial elasticstrain in this situation. The creep strain obtained by ASTMC512/C512M is the creep of cylinders at one stress levelunder standard environmental conditions. It does not neces-sarily represent the creep that occurs in an actual structure;therefore, the data needs to be carefully interpreted for appli-cation to full-size structures. Because creep measurementsare affected by the volume-surface ratio of the test specimens,any measurements on small cylinders need to be adjusted todetermine the creep on full-size structural members. Correc-tions for the volume-surface ratio may be applied in accor-dance with ACI 209R or other suitable method. For creep ofconcrete in large members, it may be more appropriate tomeasure the creep on sealed cylinders so that the adjustmentbetween the member size and the cylinder size is less.When sealed cylinders are used, it is important that thecylinder is fully sealed using materials such as copper orbutyl rubber and that the seal is not broken during loading ofthe cylinders.

5.8—Prequalification of testing laboratoriesA laboratory should be examined from two perspectives

(Bickley 1993): 1) how it has performed in the past; and2) how well it is equipped to perform properly in the future.Past test data for HSC analyzed in accordance with ACI214R shows within-test variability as a measure of the testingconsistency of the laboratory. The qualifications and experienceof technicians and inspectors should be reviewed. Thelaboratory should be accredited or inspected for conformanceto the requirements of ASTM C1077. The architect/engineershould recommend an acceptable testing laboratory.

A comprehensive internal QC protocol that covers testprocedures; the use, care, and calibration of testing equipment;and the checking and reporting procedures to be followed is asign of a well-run laboratory. Records should show that theprotocol has been followed for previous projects.

Depending on the results of the review of the past andpotential performance of the laboratory, some tests of


personnel and equipment can be made to conclude theprequalification examination (Bickley 1993).

CHAPTER 6—EVALUATION OF COMPRESSIVE STRENGTH TEST RESULTS

6.1—Statistical conceptsThe first step in evaluating QC procedures is determining

whether the distribution of the compressive strength testresults follows a normal frequency distribution. Cook (1989)suggests that skewed distributions may occur for HSCbecause the compressive strength may be limited by theaggregate strength. This can be the case for concrete strengthsexceeding 10,000 psi (70 MPa). The distribution should beinvestigated to determine if it deviates from a normal distribu-tion. As suggested by Cook (1989), the skewness and kurtosis(peakedness of the distribution) are evaluated by calculatingthe third and fourth moments of the distribution about themean. Available data indicate that a normal frequency distri-bution is achieved for concrete with compressive strength inthe range of 6000 to 10,000 psi (40 to 70 MPa) (Cook 1982).Thus, the procedure recommended by ACI 214R, whichassumes a normal distribution, is usually a convenient tool forevaluating the quality of production and testing of HSC.

ACI 214R provides the appropriate standards of controlfor specified strengths over 5000 psi (34.5 MPa). These stan-dards of control were adopted based on examination andanalysis of compressive strength test data by ACI Commit-tees 214 and 363. The strength data examined were obtainedusing 6 x 12 in. (152 x 305 mm) cylinders. The standards ofcontrol are therefore applicable to these size specimens, andcan be considered applicable with minor differences to othercylinder sizes, such as 4 x 8 in. (102 x 203 mm) recognizedin ASTM C31/C31M.

In practice, HSC has a lower coefficient of variation thannormal-strength concrete, not because of the strength level,but because a higher degree of control is maintained in theproduction and testing of HSC. Continual review of the fieldtest results and the maintenance of records in the form ofcontrol charts, or other means, are recommended to assesswhether the desired level of control is being achieved.

Early-age control of concrete strength can be achieved bymaking and testing accelerated-cured specimens accordingto ASTM C684, especially where later-age (56- or 90-day)strength tests are the final acceptance criterion. Evaluation ofthese data should follow job-specific criteria developed at anearly phase of concreting.

Where ages later than 28 days are specified for acceptance,ACI 214R evaluation procedures can be used.

6.2—Strength evaluationACI 318 recognizes that some test results are likely to be

lower than the specified strength. ACI 318-08, Section5.6.3.3 (ACI Committee 318) for standard cured specimens,states that:

5.6.3.3 — Strength level of an individual class ofconcrete shall be considered satisfactory if both ofthe following requirements are met:

(a) Every arithmetic average of any three consecu-tive strength tests (see 5.6.2.4) equals or exceeds fc′ ;

(b) No strength test (average of two cylinders) fallsbelow fc′ by more than 500 psi when fc′ is 5000 psior less; or by more than 0.10fc′ when fc′ is more than5000 psi.

Evaluation and acceptance of the concrete can be judgedimmediately as test results are received during the course ofthe work. Strength tests failing to meet these criteria willoccur occasionally (approximately one in 100 tests), eventhough concrete strength and uniformity are satisfactory.Allowance should be made for such statistically expectedvariations in deciding whether the strength level beingproduced is adequate.

HSCs may continue to gain significant strengths after theacceptance test age, especially if fly ash or slag cement areused. During the evaluations to establish mixture proportions, astrength development curve should be established indicatingpotential strength over time. If questions arise concerningthe load-carrying capacity of a structure, however, ACI 318allows investigation by analysis using core test results or byload testing. In cases where load testing a structure is notpractical, analytical investigations using the strength resultsfrom extracted cores, or in-place tests (ACI 228.1R), aremore appropriate. Tests to evaluate the durability of theconcrete (refer to ACI 201.2R) should be performed sepa-rately on cores other than those used for strength tests.

As mentioned in Chapter 4, a correlation curve should beestablished for each high-strength mixture to relate thestrength of extracted cores (normally 4 in. [102 mm]) indiameter) to the strength of specimens used for acceptancetesting, that is, 6 x 12 in. (152 x 305 mm) or 4 x 8 in. (102 x203 mm) cylinders. Then, if coring becomes necessary, therelationship has been established, agreed upon, and is readyfor conclusive interpretation. In the absence of correlationdata, the provision 5.6.5.4 of ACI 318-08 (ACI Committee318) should be used. This provision requires that the averagestrength of a set of three cores be equal to at least 85% of fc′ ,and no single core be less than 75% of fc′ .

Cook (1989) reported that tests of 4 in. (102 mm) diametercores taken from 30 x 30 in. (760 x 760 mm) columns of10,000 psi (70 MPa) concrete resulted in average strengthsas shown in Table 6.1.

Burg and Ost (1992) reported on 4 in. (102 mm) coresdrilled from 4 ft (1220 mm) cubes of concrete with compressivestrength in the range of 10,000 to 20,000 psi (70 to 140 MPa).Sets of three cores at 91 days and 14 months produced averagestrengths as shown in Table 6.2.

In tests at 1, 2, and 7 years of age on 4 in. (102 mm) diametercores from columns made with 10,000 psi (70 MPa) concrete,Bickley et al. (1991, 1994) obtained the results shown inTable 6.3. The cementitious system in this concrete wasType I portland cement plus silica fume and slag cement.

Aïtcin and Riad (1988) reported 2-year core strengthsfrom columns made with Type I cement and silica fume. Theaverage 2-year core strength was 97% of the strength of


28-day moist-cured cylinders. These data indicate that theacceptance criteria for core strengths specified in ACI 318are also applicable to HSC.

CHAPTER 7—REFERENCES7.1—Referenced standards and reports

The standards and reports listed below were the latesteditions at the time this document was prepared. Becausethese documents are revised frequently, the reader is advisedto contact the sponsoring group if it is desired to refer to thelatest version.

American Concrete Institute201.2R Guide to Durable Concrete207.2R Report on Thermal Volume Change Effects

on Cracking of Mass Concrete209R Prediction of Creep, Shrinkage, and

Temperature Effects in Concrete Structures

211.4R Guide for Selecting Proportions for High-Strength Concrete with Portland Cementand Fly Ash

212.3R Report on Chemical Admixtures forConcrete

214R Guide to the Evaluation of Strength TestResults of Concrete

228.1R In-Place Methods to Estimate ConcreteStrength

237R Self-Consolidating Concrete301 Specifications for Structural Concrete304R Guide for Measuring, Mixing, Trans-

porting, and Placing Concrete308R Guide to Curing Concrete309R Guide for Consolidation of Concrete311.4R Guide for Concrete Inspection318 Building Code Requirements for Structural

Concrete and Commentary363R Report on High-Strength Concrete

ASTM InternationalC31/C31M Standard Practice for Making and Curing

Concrete Test Specimens in the FieldC39/C39M Standard Test Method for Compressive

Strength of Cylindrical Concrete SpecimensC94/C94M Standard Specification for Ready-Mixed

ConcreteC117 Standard Test Method for Materials Finer

than 75-μm (No. 200) Sieve in MineralAggregates by Washing

C136 Standard Test Method for Sieve Analysis ofFine and Coarse Aggregates

C157 Standard Test Method for Length Change ofHardened Hydraulic-Cement Mortar andConcrete

C172/C172M Standard Practice for Sampling FreshlyMixed Concrete

C192/C192M Standard Practice for Making and CuringConcrete Test Specimens in the Laboratory

C215 Standard Test Method for FundamentalTransverse, Longitudinal, and TorsionalFrequencies of Concrete Specimens

C469/C469M Standard Test Method for Static Modulus ofElasticity and Poisson’s Ratio of Concretein Compression

C470/C470M Standard Specification for Molds forForming Concrete Test Cylinders Vertically

C494/C494M Standard Specification for ChemicalAdmixtures for Concrete

C511 Standard Specification for Mixing Rooms,Moist Cabinets, Moist Rooms, and WaterStorage Tanks Used in the Testing ofHydraulic Cements and Concretes

C512/C512M Standard Test Method for Creep of Concretein Compression

C566 Standard Test Method for Total EvaporableMoisture Content of Aggregate by Drying

Table 6.1—Strength cores from 30 in. (760 mm)square columns (Cook 1989)

Age at test, days

Moist-cured cylinder strength at same age, %

Range Average

7 94 to 105 99

28 84 to 97 91

56 78 to 94 84

180 78 to 94 86

365 93 to 107 98

Table 6.2—Strength of cores from 4 ft (1220 mm) cubes (Burg and Ost 1992)

Cementitious system

Age at test, days

28-day moist-cured 6 x 12 in.(152 x 305 mm) cylinder strength, %

Range Average

I

91

95 to 106 99

I + SF + FA 93 to 96 95

I + SF 85 to 90 88

I + SF 93 to 104 98

I + SF + FA 102 to 105 103

I + SF + FA 107 to 110 108

I + SF

426

109 to 123 117

I + SF + FA 104 to 106 105

I + SF 94 to 98 96

I + SF 100 to 111 107

I + SF + FA 104 to 113 109

I + SF + FA 122 to 124 123*I = Type I portland cement; SF = silica fume; FA = fly ash.

Table 6.3—Column core strength at later ages (Bickley et al. 1991, 1994)

Age at test, years

Average 28-day moist-cured cylinder strength, %

Range Average

1 90 to 109 97

2 91 to 107 100

7 97 to 100 99


C617 Standard Practice for Capping CylindricalConcrete Specimens

C666/C666M Standard Test Method for Resistance ofConcrete to Rapid Freezing and Thawing,

C672/C672M Standard Test Method for Scaling Resis-tance of Concrete Surfaces Exposed toDeicing Chemicals

C684 Standard Test Method for Making, Accel-erated Curing, and Testing ConcreteCompression Test Specimens

C1077 Standard Practice for Laboratories TestingConcrete and Concrete Aggregates for Usein Construction and Criteria for LaboratoryEvaluation

C1231/C1231M Standard Practice for Use of UnbondedCaps in Determination of CompressiveStrength of Hardened Concrete Cylinders

C1610/C1610M Standard Test Method for Static Segrega-tion of Self-Consolidating Concrete UsingColumn Technique

C1611/C1611M Standard Test Method for Slump Flow ofSelf-Consolidating Concrete

C1621/C1621M Standard Test Method for Passing Ability ofSelf-Consolidating Concrete by J-Ring

These publications may be obtained from the followingorganizations:

American Concrete Institute38800 Country Club DriveFarmington Hills, MI 48333-9094www.concrete.org

ASTM International100 Barr Harbor DriveWest Conshohocken, PA 19428www.astm.org

7.2—Cited referencesAASHTO, 2006, “AASHTO LRFD Bridge Construction

Specifications,” second edition, 2004 with 2006 InterimRevisions, American Association of State Highway andTransportation Officials, Washington, DC.

ACI Committee 318, 2008, “Building Code Requirementsfor Structural Concrete (ACI 318-08) and Commentary,”American Concrete Institute, Farmington Hills, MI, 473 pp.

Aïtcin, P.-C., and Riad, N., 1988, “Curing Temperatureand Very High-Strength Concrete,” Concrete International,V. 10, No. 10, Oct., pp. 69-72.

Aïtcin, P. C.; Laplante, P.; and Bedard, C., 1985,“Development and Experimental Use of a 90 MPa (13,000 psi)Field Concrete,” High-Strength Concrete, SP-87, AmericanConcrete Institute, Farmington Hills, MI, pp. 51-70.

Bickley, J. A., 1993, “Prequalification Requirements forthe Supply and Testing of Very High-Strength Concrete,”Concrete International, V. 15, No. 2, Feb., pp. 62-64.

Bickley, J. A.; Ryell, J.; Rogers, C.; and Hooton, R. D.,1991, “Some Characteristics of High-Strength Structural

Concrete,” Canadian Journal of Civil Engineering, V. 18,No. 5, pp. 885-889.

Bickley, J. A.; Ryell, J.; Rogers, C.; and Hooton, R. D.,1994, “Some Characteristics of High-Strength StructuralConcrete: Part 2,” Canadian Journal of Civil Engineering,V. 21, No. 6, pp. 1084-1087.

Blick, R. L., 1973, “Some Factors Influencing High-Strength Concrete,” Modern Concrete, V. 36, No. 12, Apr.,pp. 38-41.

Blick, R. L.; Petersen, C. F.; and Winter, M. E., 1974,“Proportioning and Controlling High-Strength Concrete,”Proportioning Concrete Mixes, SP-46, American ConcreteInstitute, Farmington Hills, MI, pp. 144-166.

Boulay, C., 1996, “Capping HPC Cylinders with the SandBox: New Developments,” Proceedings, Fourth InternationalSymposium on the Utilization of High Strength/HighPerformance Concrete, Paris, France, May, pp. 197-202.

Boulay, C., and de Larrard, F., 1993, “The Sand-Box, ANew Capping System for Testing HPC Cylinders,” ConcreteInternational, V. 15, No. 4, Apr., pp. 63-66.

British Standards Institute, 1986, “Testing Concrete,Specification for Compression Testing Machines forConcrete (BS 1881-115),” London, UK, 14 pp. (withdrawn)

Burg, R. G., and Ost, B. W., 1992, “Engineering Properties ofCommercially Available High-Strength Concretes,” PCAResearch and Development Bulletin RD104T, PortlandCement Association, Skokie, IL.

Burg, R. G.; Calderone, M. A.; Detwiler, G.; Jansen, D. C.;and Williams, T. J., 1999, “Compression Testing of HSC:Latest Technology,” Concrete International, V. 21, No. 8,Aug., pp. 67-76.

Canadian Standards Association, 2009, “Concrete Materialsand Methods of Concrete Construction (A23.1-09/A23.2-09),”Mississauga, ON, Canada, 653 pp.

Carino, N. J.; Guthrie, W. F.; and Lagergren, E. S., 1994,“Effects of Testing Variables on the Measured CompressiveStrength of High-Strength (90 MPa) Concrete,” NISTIR5405, National Institute of Standards and Technology,Gaithersburg, MD, Oct., 141 pp.

Chamberlin, W. H., 1952, “Effect of Initial CuringTemperatures on Compressive Strength and Durability ofConcrete,” Concrete Laboratory Report No. C-625, U.S.Bureau of Reclamation, Denver, CO.

Cook, W. D.; Miao, B.; Aïtcin, P. C.; and Mitchell, D., 1992,“Thermal Stresses In High-Strength Concrete Columns,” ACIMaterials Journal, V. 89, No. 1, Jan.-Feb., pp. 61-68.

Cook, J. E., 1982, “Research and Application of High-Strength Concrete Using Class C Fly Ash,” ConcreteInternational, V. 4, No. 7, July, pp. 72-80.

Cook, J. E., 1989, “10,000 psi Concrete,” ConcreteInternational, V. 11, No. 10, Oct., pp. 67-75.

CPCA, 1995, Design and Control of Concrete Mixtures,sixth edition, Canadian Portland Cement Association,Ottawa, ON, Canada.

Day, R. L., 1994, “Strength Measurement of ConcreteUsing Different Cylinder Sizes: A Statistical Analysis,” Cement,Concrete, and Aggregates, V. 16, No. 1, June, pp. 21-30.


Detwiler, R. J., and Bickley, J. A., 1993, “An Analysis ofInterlaboratory Test Program Results,” New ConcreteTechnology: Robert E. Philleo Symposium, SP-141, T. C.Liu and G. C. Hoff, eds., American Concrete Institute,Farmington Hills, MI, pp. 103-115.

Drake, K. D., 1985, “High Strength Concrete in Seattle,”High-Strength Concrete, SP-87, American Concrete Institute,Farmington Hills, MI, pp. 21-34.

Fiorato, A. E., and Burg, R. G., 1991, “Application ofHigh-Strength Concrete to Drilled Shafts,” Proceedings,16th Annual Members’ Conference, Deep FoundationsInstitute, Chicago, IL, Oct.

Forstie, D. A., and Schnormeier, R., 1981, “Developmentand Use of 4 by 8-Inch Concrete Cylinders in Arizona,”Concrete International, V. 3, No. 7, July, pp. 42-45.

Gaynor, R. D., and Wedding, P. A., 1964, “Studies ofCapping Procedures for Concrete Cylinders: Effects of Typeof Material and Cap Thickness (Series J-128),” JointTechnical Information Letter No. 227/216, National Sandand Gravel Association/National Ready Mixed ConcreteAssociation, Silver Spring, MD, Nov., 8 pp.

Ghosh, R. S., and Bickley, J. A., 1978, “A Method forCalculation of the Maximum Permissible Thermal Shock toAvoid Cracking of the CN Tower,” Canadian Journal ofCivil Engineering, V. 5, No. 1, Mar., pp. 134-137.

Gonnerman, H. F., 1924, “Effects of End Condition ofCylinder in Compression Tests of Concrete,” ASTMProceedings, V. 24, Part 24, Philadelphia, PA, pp. 1036-1064.

Gray, R. J., 1990, “Results of an Interlaboratory ConcreteTesting Program: Part I,” Cement, Concrete, and Aggregates,V. 12, No. 1, pp. 12-23.

Henning, N. E., 1961, “Concrete Test Molds and CappingMaterials,” ACI JOURNAL, Proceedings V. 58, No. 7, Jan.,pp. 851-854.

Hester, W. T., 1980, “Field Testing High-StrengthConcretes: A Critical Review of the State-of-the-Art,”Concrete International, V. 2, No. 12, Dec., pp. 27-38.

Kennedy, S.; Detwiler, R.; Bickley, J. A.; and Thomas,M., 1995, “Results of an Interlaboratory Test Program:Compressive Strength of Concrete,” Cement, Concrete, andAggregates, V. 17, No. 1, June, pp. 3-10.

Klieger, P., 1957, “Early High-Strength Concrete forPrestressing,” Proceedings, World Conference on PrestressedConcrete, San Francisco, CA, pp. A5.1-A5.14.

Lessard, M.; Baalbaki, M.; and Aïtcin, P. C., 1996, “Effectof Pumping on Air Characteristics of Conventional Concrete,”Transportation Research Record No. 1532, TransportationResearch Board, Washington, DC, pp. 9-14.

Lobo, C. L.; Mullings, G. M.; and Gaynor, R. D., 1994,“Effect of Capping Materials and Procedures on theMeasured Compressive Strength of High-StrengthConcrete,” Cement, Concrete, and Aggregates, V. 16, No. 2,Dec., pp. 173-180.

NRMCA, 2008, “Plant Certification Checklist—Section 3,Certification of Ready Mixed Concrete Production Facilities,”Quality Control Manual, National Ready Mixed ConcreteAssociation, Silver Spring, MD, 30 pp.

Noguchi, T., and Tomosawa, F., 1996, “Effect of Charac-teristics of Testing Machine on Measured CompressiveStrength of High Strength Concrete,” Proceedings of theFourth International Symposium on the Utilization of HighStrength/High Performance Concrete, Paris, France, May,pp. 301-308.

PCI Self-Consolidating Concrete FAST Team, 2003,“Interim Guidelines for the Use of Self-ConsolidatingConcrete in PCI Member Plants,” PCI Journal, May-June,pp. 14-18.

Philleo, R. E., 1986, “Freezing and Thawing Resistance ofHigh-Strength Concrete,” NCHRP Synthesis No. 129, Trans-portation Research Board, Washington, DC, 31 pp.

Pistilli, M. F.; Cygan, A.; and Burkart, L., 1992, “ConcreteSupplier Fills Tall Order,” Concrete International, V. 14,No. 10, Oct., pp. 44-47.

Pistilli, M. F., and Willems, T., 1993, “Evaluation ofCylinder Size and Capping Method in Compression StrengthTesting of Concrete,” Cement, Concrete and Aggregates,V. 15, No. 1, pp. 59-69.

Rosenbaum, D. B., 1990, “Is Concrete Becoming TooStrong to Test?” Engineering News Record, V. 224, No. 3,Jan., pp. 56-58.

Roy, D. M.; Scheetz, B. E.; Sabol, S.; Brown, P. W.; Shi,D.; Licastro, P. H.; Idorn, G. M.; Andersen, P. J.; andJohanson, V., 1993, “Maturity Model and Curing Technology,”Strategic Highway Research Program Report SHRP-C-265,National Research Council, Washington, DC, Feb.

Sanchez, A., and Hester, W. T., 1990, “Designer-ContractorDialogue and High-Strength Concrete Construction,” TheConstruction Specifier, V. 43 No. 12, pp. 56-62.

Saucier, K. L., 1972, “Effect of Method of Preparation ofEnds of Concrete Cylinders for Testing,” MiscellaneousPaper No. C-72-12, U.S. Army Engineer WaterwaysExperiment Station, Vicksburg, MS, Apr., 51 pp.

Troxell, G. E., 1942, “The Effect of Capping Methods andEnd Condition Before Capping Upon the CompressiveStrength of Concrete Test Cylinders,” Proceedings, V. 41,Committee Reports, Technical Papers, ASTM International,West Conshohocken, PA, pp. 1038-1045.

Wainright, P. J., and Tolloczko, J. J. A., 1983, “ATemperature-Matched Curing System Controlled byMicrocomputer,” Magazine of Concrete Research, V. 35,No. 124, Sept., pp. 164-169.

Werner, G., 1959, “The Effect of Type of Capping Materialon the Compression Strength of Concrete Cylinders,”Proceedings, V. 58, Committee Reports, Technical Papers,ASTM International, West Conshohocken, PA, pp. 1166-1181.

As ACI begins its second century of advancing concrete knowledge, its original chartered purposeremains “to provide a comradeship in finding the best ways to do concrete work of all kinds and inspreading knowledge.” In keeping with this purpose, ACI supports the following activities:

· Technical committees that produce consensus reports, guides, specifications, and codes.

· Spring and fall conventions to facilitate the work of its committees.

· Educational seminars that disseminate reliable information on concrete.

· Certification programs for personnel employed within the concrete industry.

· Student programs such as scholarships, internships, and competitions.

· Sponsoring and co-sponsoring international conferences and symposia.

· Formal coordination with several international concrete related societies.

· Periodicals: the ACI Structural Journal and the ACI Materials Journal, and Concrete International.

Benefits of membership include a subscription to Concrete International and to an ACI Journal. ACImembers receive discounts of up to 40% on all ACI products and services, including documents, seminarsand convention registration fees.

As a member of ACI, you join thousands of practitioners and professionals worldwide who share acommitment to maintain the highest industry standards for concrete technology, construction, andpractices. In addition, ACI chapters provide opportunities for interaction of professionals and practitionersat a local level.

American Concrete Institute38800 Country Club DriveFarmington Hills, MI 48331U.S.A.Phone: 248-848-3700Fax: 248-848-3701

www.concrete.org



The AMERICAN CONCRETE INSTITUTE

was founded in 1904 as a nonprofit membership organization dedicated to publicservice and representing the user interest in the field of concrete. ACI gathers anddistributes information on the improvement of design, construction andmaintenance of concrete products and structures. The work of ACI is conducted byindividual ACI members and through volunteer committees composed of bothmembers and non-members.

The committees, as well as ACI as a whole, operate under a consensus format,which assures all participants the right to have their views considered. Committeeactivities include the development of building codes and specifications; analysis ofresearch and development results; presentation of construction and repairtechniques; and education.

Individuals interested in the activities of ACI are encouraged to become a member.There are no educational or employment requirements. ACI’s membership iscomposed of engineers, architects, scientists, contractors, educators, andrepresentatives from a variety of companies and organizations.

Members are encouraged to participate in committee activities that relate to theirspecific areas of interest. For more information, contact ACI.

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