Low Heat High Performance Concrete Glass Fiber … Heat High Performance Concrete for Glass Fiber...
Transcript of Low Heat High Performance Concrete Glass Fiber … Heat High Performance Concrete for Glass Fiber...
Low Heat High Performance Concrete for Glass Fiber Reinforced Polymer Reinforcement
by
Alien Jawara
A Thesis Submitted to the Faculty of Graduate Studies of
the University of Manitoba in Partial Fulfillment of the Requirements of the Degree of
Master of Science
Structural Engineering Division Department of Civil Engineering
University of Manitoba Wmnipeg, Manitoba
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LOW HEAT mGH PERFORMANCE CONCRETE FOR GLASS FIBER REINFORCED POLYMERREllWORCEMrnNT
BY
ALIEU JAWARA
A ThesislPracticum submitted to the Faculty of Graduate Studies of The University
of Manitoba in partial fulfillment of the requirements of the degree
of
MASTER OF SCIENCE
ALIEU JAWARA©1999
Permission has been granted to the Library of The University of Manitoba to lend or sen copies of this thesislpracticnm, to the National Library of Canada to microfilm this thesis and to lend or sen copies of the ~ and to Dissertations Abstracts International to publish an abstract of this thesis/practicum.
The author reserves other publication rights, and neither this thesis/practicum nor extensive extracts from it may be printed or otherwise reproduced without the author's written permission.
----------------------ACKNOWLEDGMENTS
The author would like to acknowledge the following people who were vital to the research performed for this testing program.
• Dr. Sami Rizkalla for his guidance and continuous support throughout the research work;
• Atomic Energy of Canada Limited for providing the financial support for this research;
• Messrs. Moray McVey of ISIS Canada, Scott Sparrow and Roy Hartle of University of Manitoba and Nazeer Khan of AECL for their assistance in fabricating and testing the specimens;
• ISIS Canada staff for their support and cooperation;
• Professor John Glanville for reviewing the final draft of this thesis.
---------------------------------ABSTRACT
Low heat high performance concrete (LHHPC) is concrete with low cement
content, a consequent low heat of hydration and a relatively low alkalinity. The research
program described in this thesis was designed to study Lffi-lPC in terms of mechanical
properties, structural behaviour and durability under freezing and thawing. The
durability of reinforcement (steel and GFRP) in the low alkaline environment of LHHPC
is also investigated.
Use of glass fiber reinforced polymer (GFRP) as a replacement for conventional
steel reinforcement has increased rapidly for the last ten years. The non-corrosive
characteristics and high strength-to-weight ratio of GFRP might significantly increase the
service life of structures. However, the chemical composition of glass is known to be
unstable in the high alkaline environment of concrete pore water. The low alkalinity of
LHHPC might have beneficial effects in the use of GFRP as reinforcement for this new
concrete. The low alkalinity might, on the other hand accelerate corrosion of steel
reinforcement.
Over sixty standard size cylinders were cast and tested to study the mechanical
properties of LIll-IPC and the results indicate compressive strengths of over 70 ~a at 28
days for LHHPC.
Abstract
Eight beams of rectangular section were cast and tested to study the behaviour of
the reinforced LHHPC. The results indicate a higher strength and ductility for LHHPC
than the control normal conventional concrete (Nee) beams.
The results from the air-entrained concrete indicate that LHHPC has an excellent
durability factor against freezing and thawing while maintaining high compressive
strengths for an air content of 4.6 percent.
The tensile strength ofGFRP bars embedded in both LHHPC and NCe, at 60°C,
are identical after one month.
iii
TABLE OF CONTENTS
Acknowledgements
Abstract
Table of Contents
List of Tables
List of Figu res
1. Introduction
1.1 General
1.2 Objectives
1.3 Scope and Contents
2. Literature Review
2.1 General
2.2 Constituents ofLHHPC
2.2.1 Sulfate-Resistant Portland Cement (Type 50)
2.2.2 Silica Fume
2.2.3 Silica Flour
2.2.4 Liquid Superplasticizer (Disal)
1
ii
iv
vii
ix
1-1
1-2
1-2
2-1
2-1
2-1
2-1
2-2
2-2
2-3
2.2.S Mix Water
2.2.6 LSL Sand
2.2.7 Granite Gravel
2.2.8 Pea Stone Gravel
2.3 Properties ofLHHPC
2.4 Freeze-Thaw Durability of Concrete
2.S Glass Fiber Reinforced Polymer Reinforcements
2.S.1 Mechanical Properties of GFRP
2.S.2 Durability ofGFRP in Concrete
3. Experimental Program
3.1 Phase I: Material Properties
3.1.1 Materials
3.1.2 Instrumentation and Test Procedure
3.2 Phase II: Structural Behaviour
3.2.1 Materials
3.2.2 Instrumentation
3.3 Phase III: Durability Aspects
3.3.1 Freeze-Thaw Cycles
3.3.1.1 ~erials
3.3.1.1 Methodology
3.3.2 DurabilityofGFRP inLHHPC
3.3.2 Durability of Steel in LHHPC
v
Table of Contents
2-3
2-3
2-4
2-4
2-S
2-7
2-8
2-9
2-10
3-1
3-1
3-2
3-3
3-4
3-4
3-S
3-6
3-6
3-6
3-7
3-8
3-10
4. Test Results and Discussions
4.1 Phase I: Material Properties
4.2 Phase II: Structural Behaviour
4.2.1 Load-Deflection Behaviour
4.2.2 Crack Patterns and Failure Modes
4.2.3 Strain Distribution
4.2.4 Ductility
4.2.5 Analytical Model
4.3 Phase m: Durability Aspects
4.3.1 Freeze-Thaw Cycles
4.3.2 Compressive Strength
4.3.2 Durability of Reinforcements in LHHPC
5. Summary and Conclusions
5.1 Phase I: Material Properties
5.2 Phase II: Structural Behaviour
5.3 Phase ill: Behaviour under Cycles of Freezing and Thawing
5.4 Durability of Reinforcements
5.5 Recommendations for Future Research
6. References
vi
Table of Contents
4-1
4-1
4-7
4-7
4-10
4-12
4-13
4-14
4-15
4-15
4-17
4-17
5-1
5-1
5-2
5-3
5-4
5-4
6-1
-------------- LIST OF TABLES
Table
2.1 Resuhs of the 28-day LHHPC from CANMET 2-14
2.2 Results of the 90-day LHHPC from CANMET 2-15
3.1 Mix Design for LIllIPC and SHPC 3-12
3.2 Details of Beams Reinforced by Steel 3-13
3.3 Details of Beams Reinforced by GFRP 3-13
3.4 Mix Design and Properties for Different Batches of the Freeze-Thaw Samples 3-14
3.5 Test Dates for Durability Specimens for Steel and GFRP Reinforcements 3-15
4.1 14 Day Test for Batch 1 4-19
4.2 28 Day Test for Batch 1 4-19
4.3 90 Day Test for Batch 1 4-20
4.4 28 Day Test for Batch 2 ofLIllIPC 4-21
4.5 14 Day Test for Batch 3 ofLHHPC 4-22
4.6 28 Day Test for Batch 3 ofLIDIPC 4-22
4.7 90 Day Test for Batch 3 ofLHHPC 4-23
4.8 180 Day Test for Batch 3 ofLHHPC 4-23
4.9 28 Day Test for Batch 4 ofLHHPC 4-24
4.10 90 Day Test for Batch 4 ofLHHPC 4-24
List of Tables
4.11 180 Day Test for Batch 4 ofLIllIPC 4-25
4.12 Average Strength at Different Ages for 100 rom Diameter Cylinders 4-26
4.13 Average Strength and Elastic Moduli at Different Ages for 150 mm Diameter
Cylinders 4-26
4.14 Summary of Test Results for all Tested Beams in Phase II 4-27
4.15 Durability Factor for the Specimens with Different Air Contents 4-28
4.16 28 Day Compressive Strength Results for Cylinders with Different Air
Contents 4-29
4.17 Tension Test Results ofGFRP Bars after 36 days of Embedding in Concrete 4-29
viii
LIST OF FIGURES
Figure
2.1 Particle Size Distribution of the Components ofLHHPC 2-16
2.2 Strength Development in LHHPC and SHPC 2-17
2.3 Tensile Strength ofLHHPC and SHPC 2-18
2.4 Shrinkage ofLHHPC and SHPC with Varying Duration of Water Curing 2-19
2.5 pH ofLHHPC and SHPC as a Function of Time After Casting 2-20
2.6 Temperature Rise in LHHPC and SHPC 2-21
3.1 Picture and Schematic of Cylinder Testing System 3-16
3.2 Design and Instrumentation for Beams Reinforced by Steel and GFRP 3-17
3.3 Stress-Strain Diagram for 15M Steel Reinforcing Bar 3-18
3.3 Stress-Strain Diagram for 12M C-Bar Reinforcing Rod 3-19
3.5 Picture and Schematic of Beam Test Set-Up 3-20
3.6 Testing of Fundamental Transverse Frequency 3-21
3.7 Tension Specimen to Investigate the Durability ofGFRP in Concrete 3-22
4.1 28 Day Stress-Strain in Compression from Batch 1 4-30
4.2 Comparison of Different End-Preparations 4-31
4.3 Strength vs. Age ofLIllIPC, SHPC and NCC 4-32
4.4 Changes in Stress-Strain Behaviour with Age ofLHHPC 4-33
List of Figures
4.5 Load-Deflection Behaviour ofLHHPC and NeC Reinforced by Steel 4-34
4.6 Load-Deflection Behaviour ofLHHPC and Nee Reinforced by GFRP 4-35
4.7 Load-Deflection Behaviour ofNCC Reinforced by Steel and GFRP 4-36
4.9 Crack Pattern at Failure for Beams Reinforced by Steel 4-38
4.9 Crack Pattern at Failure for Beams Reinforced by Steel 4-38
4.10 Crack Pattern at Failure for Beams Reinforced by GFRP 4-39
4.11 Load vs. Reinforcement Strain for Beams Reinforced by GFRP 4-40
4.12 Strain Distribution at Ultimate for Beams Reinforced by Steel 4-41
4.13 Strain Distnoution at Ultimate for Beams Reinforced by GFRP 4-42
4.14 Analytical vs. Experimental for NCC Beam Reinforced by Steel 4-43
4.15 Analytical vs. Experimental for LHHPC Beam. Reinforced by Steel 4-44
4.16 Average Fundamental Transverse Frequency for LHHPC Prisms 4-45
4.17 Freeze-Thaw Cycling Specimens after 300 Cycles 4-46
4.18 Stress-Strain Diagrams for Cylinders with Different Air Contents 4-47
4.19 Compressive Strength and Durability Factor for Freeze-Thaw Samples 4-48
4.20 Picture of Durability Tension Specimen (with GFRP) at Failure 4-49
x
1. INTRODUCTION
1.1 General
Low heat high performance concrete (LHHPC) mix design was patented by
Atomic Energy of Canada Limited (AECL) in July 1996 [United States Patent #
5,531,823]. The purpose of the research conducted by AECL was to investigate the
suitability of using LmIPC in the construction of waste disposal facilities and massive
concrete plugs. The use of LHHPC would substantially reduce the heat of hydration of
mass concrete structures and therefore reduce the potential for thermal cracking.
LHHPC has the characteristic of low heat of hydration of 15°C compared to 45
°C in standard high perfonnance concrete (SHPC). The low heat of hydration is of great
advantage for massive concrete structures where thermal cracking is considered to be a
serious problem. LHHPC also has a relatively low alkalinity level of pH 9, which may be
advantageous for concrete structures reinforced with glass tiber reinforced polymer
(GFRP) reinforcements where high pH might cause deterioration of the glass fibers.
The research topic of this thesis includes an extensive experimental program
conducted at the University of Manitoba to evaluate the suitability of using LHHPC for
concrete structures including structures reinforced by GFRP reinforcements. The short
term behaviour was studied while the long tenn behaviour is currently being investigated.
Chapter I. lntroduction
1.2 Objectives
The various specific objectives of this research program are:
1. to detennine the fundamental characteristics of LffilPC. The characteristics
include properties such as compressive strength. elastic modulus and strain at
ultimate load. Maturity of the concrete with time was also investigated.
2. to evaluate the performance of LHHPC as concrete for structural members.
reinforced by steel as well as GFRP reinforcement. subjected to flexure.
3. to detennine the durability of LHHPC using accelerated freezing and thawing
tests. The effect of air content on the durability and compressive strength was
also investigated in this phase.
4. to detennine the effect of the low pH of LflliPC on the durability of GFRP
reinforcement.
1.3 Scope and Contents
In order to have an efficient experimental program and to achieve the desired
objectives, the research is divided into three phases:
Phase I: Material Properties:
This phase was designed to study the fundamental characteristics of LfllIPC. The
characteristics studied include axial compressive strength. modulus of elasticity 9 stress
strain characteristics and maturity. Sixty standard cylinders were cast and tested in
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Chapter I. Introduction
compression using an MTS closed-loop cyclic loading testing machine. The variables
included the size of cylinders (100 mm or 150 nun diameter) and the type of end
preparation (either capped or ground). The cylinders were tested at ages 14, 28, 90 and
180 days. Standard high perfonnance concrete (SHPC) and nonna! conventional concrete
(NCe) were used for comparison with LIDIPC.
Phase U: Structural Behaviour
This phase was designed to study the structural behaviour of LffiIPC. The
program included eight singly-reinforced LHHPC beams tested in flexure up to failure.
The various parameters considered in this phase were the reinforcement ratio and the type
of reinforcement. An additional four beams fabricated with NeC were also tested and
used as control specimens.
Phase ill: Durability Aspects
This phase was designed to study the durability aspects of LHHPC. Phase III is
subdivided into two parts. The first part includes investigation of the durability of the
LmIPC subjected to freezing and thawing cycles. Three different batches of LIfl-IPC
were manufactured with different air contents. The effect of the amount of air entrained
in the concrete on the freeze-thaw durability and the compressive strength is studied.
The second part of Phase III was designed to study the effect of the low alkaliniry
of LHHPC on the tensile strength of GFRP reinforcements and the corrosion of steel in
comparison to NCC. It has been reported that glass fibre deteriorates in alkaline solution
and the degree of deterioration increases with increasing pH and temperature of the
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Chapter 1. lntroduction
solution [Katsuki and Uomoto; prediction of deterioration of glass fibres due to alkali
attack]. It is anticipated that the low pH value of LHHPC is beneficial to the use of
GFRP but will accelerate the corrosion of steel reinforcement. Generally, steel
reinforcement is protected against corrosion by the highly alkaline concrete-pore solution
(PH in excess of 12.5). Such alkaline environments cause the passivation of the steel.
This research is focussed on evaluating the long-term structural behaviour of
LHHPC with GFRP and steel reinforcements in comparison with Nee. Due to the time
constraints of the study, this thesis includes the initial results of the research. Other
researchers at the University of Manitoba will present the long-tenn results in the future.
The following is a brief description of the contents of each chapter in the thesis:
Chapter 2: Literature Review
This chapter reviews the work available in the literature related to low heat high
performance concrete. The properties of GFRP and their durability in concrete are also
presented. Due to the lack of any literature or work conducted on the durability of
LHHPC, the durability standard for high performance concrete in tenns of freezing and
thawing are reviewed to provide data base for the new work presented in this thesis.
Chapter 3: Experimental Program
This chapter describes the experimental program of the research including the
three phases conducted at the University of Manitoba. Detailed description of the
material used and the instrumentation are discussed. The experimental program is
divided into the three phases described above.
1-4
Chapter I. Introduction
Chapter 4: Results and discussions
This chapter presents the results of the three phases of the experimental program.
Analyses of the test results in terms of load-deflection behavior, member ductility, crack
pattern and failure modes are described. The results for the different phases are presented
separately.
Chapter S: Summary and Conclusions
A Summary of the different phases of the investigation is presented. The main
conclusion for the short-tenn structural behaviour is discussed.
1-5
2. Literature Review
2.1 General
This chapter presents an overview of the work reported in the literature in the field
of low heat high performance concrete (LIrnPC). The majority of the research on
LHHPC has been carried out by the Canada Centre fur Min{;r~l and Energy Technology
(CANMET) under contract with Atomic Energy of Canada Limited (AECL). The
chapter also includes a brief review of the durability of concrete under the effect of
freezing and thawing cycles. The properties of glass fiber reinforced polymer
reinforcements (GFRP) and their durability in concrete is also reviewed.
2.2 Constituents of LHHPC
This section describes the various constituents of LfllIPC and their unique
characteristics that give the concrete its outstanding qualities.
2.2.1 Sulfate-Resistant Portland Cement (Type 50)
Sulfate-Resistant Portland Cement (type 50) used in this project was supplied by
LaFarge. Type 50 Portland cement is generally used in conditions where the concrete is
subject to sulfate action.
Chapter 2. Literature Review
2.2.2 Silica Fume
The silica fume used was obtained from SKW Canada Incorporated. This
material contains 96.5 percent silicon dioxide (Si02) with a specific surface area of 18 to
20 m2/g. The average particle diameter is 0.1 to 0.2 J.lm with a generally spherical shape.
The bulk density of this material is 250 to 300 kglm3 and the specific gravity is 2.2. This
material is chemically reactive and is considered to be part of the cementitious
component of the mixes for LHHPC. Silica fume acts like a filler and as a pozzolan. A
pozzolanic material reacts with calcium hydroxide produced during the hydration of the
cement to form a cementitious product, which helps to block the pores and provide a
dense and impermeable concrete. The use of silica fume as a replacement for a part of
the cement has been shown to result in a considerable increase in compressive strength.
The use of silica fume is therefore of particular interest in high perfonnance concrete.
There have been several independent studies on the use of silica fume as a cement
replacement over the last decade. R. D. Hooton, 1993, summarized the influence of silica
fume in imparting higher resistance to sulfate attack, alkali reactive aggregates, and
freezing and thawing. Carette et aI, 1989 found out that the addition of silica fume causes
a small increase in the rate of strength gain up to 28 days. However, at later ages the
plain concrete continued to gain strength while the silica fume concrete appeared to have
reached a threshold.
2.2.3 Silica Flour
Silica flour is made from mined quartzite and contains approximately 100 percent
silicon dioxide (Si02). The specific surface area of this material is 0.350 m2/g. The bulk
2-2
Chapter 2~ Literature Review
density is 850 kglmJ and the pH is 6.8. This material is non-reactive and is used as a
filler. The particle size distribution ranges from 0.50 to 75 f.lm.
2.2.4 Liquid Superplasticizer (Disal)
The liquid superplasticizer (Disal) was manufactured by Handy Chemicals
Limited. The use of superplasticisers is beneficial in the production of high strength
concrete. They disperse cement particles and increase the fluidity of the concrete.
Therefore they are used to increase the workability of the concrete at a constant water
cement ratio or to reduce the amount of water in the mix and maintain the required
workability.
2.2.5 Mix Water
The mix water used in this project was obtained from the City of Winnipeg water
system.
2.2.6 LSL Sand
LaFarge supplied the LSL sand. It was used as a substitute for the LHHPC sand
normally used by AECL. The particle size distribution reveals that the two sands are
very similar but the LSL sand is slightly finer (Figure 2.1). In this application the particle
size difference is considered to be insignificant. The LSL sand was used because of its
availability on site at the concrete plant.
2-3
Chapter 2. Literature Review
2.2.7 Granite Gravel
The granite gravel was obtained by AI Meisner Limited from a quarry operated by
the Province of Manitoba, located 10 Ian east of the town of Seven Sisters, Manitoba.
This material was crushed and washed by AI Meisner Limited. After crushing of the
material, the particle size distribution was between 5 and 13 nun (Figure 2.1). This
material contains micro-fractures as a result of the blasting and crushing processes.
2.2.8 Pea Stone Gravel
LaFarge supplied the pea stone gravel. This is a sub-rounded material consisting
of approximately 95 percent limestone and 5 percent granite. The particle sizes of the
material ranges from one to ten rom and had a moisture content of 4.4 percent. The
particle size analysis information can be seen in Figure 2.1.
The properties of aggregates that are of importance in the production of high
strength concrete are shape, grading, strength, and chemical and physical interaction with
the cement paste, which affect the bond between the aggregates and the mortar. Shape
and grading of the aggregate influence the water requirement of the concrete. The level
of strength achieved in high strength concrete is often limited by the mechanical
properties of the aggregate and the bond with the cement paste. Gjorv et aI, 1987
reported that for concrete strengths of up to 70-90 MPa the concrete fracture is mostly
characterised by bond failure between aggregate particles and the cement paste. For
concrete strengths greater than 90 :MPa, the fracture is mainly controlled by the strength
of the aggregates. A compressive strength of 165 MPa at 28 days was achieved using
Jasper aggregate (Gjorv et ai, 1987). Strength levels of 260 rvlPa were obtained using
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Chapter 2. Literature Review
special aggregates such as calcined bauxite (Hose, 1990). Generally, the strength of the
coarse aggregate has a greater effect on the strength of the concrete than that of the fine
aggregate (Meininger, 1978).
2.3 Properties of Low Heat High Performance Concretes
The Canada Center for Mineral and Energy Technology (CA.N}dET), under
contract with AEeL, has conducted laboratory-scale studies of concrete samples,
including LHHPC. The studies provided data on the thermo-mechanical properties of the
concretes. The purpose of their study was to establish the basic mechanical properties of
low heat and standard high perfonnance concretes (SHPC) in uniaxial and triaxial
compression at ambient and elevated test temperatures.
In a presentation in 1996, Dr. Malcolm Grey of AECL reported that the
unconfined compressive strengths of LIllIPC are very well stabilized around 20, 40 and
70 MPa for 3-, 7- and 28-day old concretes, respectively, as shown in Figure 2.2. Figure
2.2 also shows the relationship of the unconfined compressive strength with curing time
and water-cementitious (W/CM) ratio of LffiIPC compared with SHPC. The tensile
strength of LIDIPC is virtually zero until three days of nonnal curing, and it increases to
6 MPa at 28 days. Figure 2.3 shows a comparison of the split cylinder tensile strengths
between LHHPC and SHPC. Unlike LHHPC, SHPC has a tensile strength of about 5
MPa after only one day of curing. The tensile strengths of LffilPC and SHPC are
identical after 28 days of curing.
2-5
Chapter 2., Literature Review
The report from AECL also discussed the shrinkage characteristics of LHHPC.
The shrinkage of LHHPC is shown to be very sensitive to the duration of water curing.
Shrinkage of LID-IPC decreased dramatically with the duration of water curing. After
one day of curing under water, the 1 OO-day shrinkage of LHHPC was 850 J.1£,
significantly higher than the 550 J,l£ of SHPC. With 7 days of water curin& the 100-day
shrinkage of LHHPC dropped to 400 J,l£, which was lower than the shrinkage of SHPC.
Figures 2.4 (a) to Cd) show the shrinkage ofLHHPC compared with SHPC with different
duration of water curing.
SOOg of granulated mortars each of LHHPC and SHPC were cured under water
for 28 days after casting and measured for pH using a Becham pH meter equipped with
an Ag-AgCl electrode, [United States Patent # 5,531,823]. The results for LHHPC and
SHPC are presented in Figure 2.5 and show that after six months, the pH of LHHPC and
the SHPC mixtures are stable at 9.65 and 12.30, respectively.
To detennine the temperature rise during hydratio~ AECL researchers measured
the temperatures with time at the center of cubical specimens poured into an insulated
box with a specimen volume of 0.027 m3, [United States Patent # 5,531,823]. The
temperature rise of the LHHPC and SHPC specimens is shown in Figure 2.6. The
temperature rise of LIDIPC was only 15°C, which is far lower than the 43 °C
temperature rise of SHPC.
In June 1995, researchers at CANMET conducted compressive tests on 102 nun
diameter LHHPC and SHPC specimens at confining pressures of 0, 4.5, 9, 18 and 36
l\1Pa and at temperatures of 23°, 50° and 90°C. Both the 28-day and 90-day old
specimens were tested under each condition to study the thenno-mechanical properties of
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Chapter 2~ Literature Review
the two types of concrete. It was observed that at confining pressures below 9 MP~ both
concretes exhibited elastic behaviour. At and above 9 MP~ the concretes exhibited
pseudo-plastic behaviour. The results of CANMET show that SHPC has a higher
compressive strength than LHHPC. The 90-day old specimens displayed higher strength
than the 28-day specimens~ and the increase in strength was found to be more pronounced
in the LHHPC. Heating up to 90°C reduced the strengths of both concretes but it was
noted that the reductions were larger for SHPC than for LfiliPC. Tangent Young's
modulus and Poisson's ratio seemed to be unaffected by the confining pressure and
temperature. The 90-day SHPC and LIflIPC had slightly higher tangent Young's moduli
than the concretes that were cured for 28-day. Tables 2.1 and 2.2 summarize the results
of the thermo-mechanical properties of LffilPC at 28 days and 90 days, respectively.
2.4 Freeze-Thaw Durability of Concrete
One of the major problems of concrete is its susceptibility to damage during
freezing and thawing cycles when it is in a saturated or near saturated condition. There
has been much research in the field of high performance concrete to study behaviour
under cycles of freezing and thawing. No research was conducted to study the behaviour
of LffiIPC under cycles of freezing and thawing; therefore, literature in the field of high
performance concrete is presented.
Cohen et aI, 1992~ subjected non-air-entrained high-strength concrete specimens
with 0.35 water-cementitious materials ratio and 10 percent silica fume by mass of
Portland cement to freeze-thaw cycles. The specimens were cured in saturated lime-
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Chapter 2~ Literature Review
water for periods of7, 14,21, and 56 days to evaluate the effects of the duration of curing
on their frost resistance properties. The use of frost resistant aggregates in their research
implies that the failure of non-air- entrained concrete could be attributed only to the
cracking of the paste and not the aggregate. It was found that silica fume improved the
frost resistance mechanism of the paste in the concrete. All specimens failed when tested
in accordance with ASTM C 666 Standard Tests, Procedure A, using 60 percent relative
modulus as the failure criterion. Cohen et al found out that after 300 cycles the modulus
of elasticity dropped to 4.6 percent of its original value while the compressive strength
only dropped to 72.7 percent of its original value.
There have been several criticisms of the testing conditions of ASTM C 666 as
being too harsh and not representative of actual environmental exposure. Ghaffoori et ai,
1997, made a comparison of the perfonnance of concrete pavers tested under ASTM C
67 to that of ASTM C 666. The test results revealed significant variation in the amount
and rate of deterioration, and the mode of failure. In view of the diverse results obtained
by Ghafoori et ai, development of a new freezing and thawing procedure, representative
of cement-based materials and the field exposure conditions appears to be warranted.
2.5 Glass Fiber Reinforced Polymer Reinforcements
The use of glass fiber reinforced polymer (GFRP) is a promising solution for the
corrosion problems of steel reinforcement in concrete structures. In addition to its non
corrosive characteristics and magnetic neutrality, its light weight leads to lower costs of
transportation, handling on the job site, and installation, compared to steel reinforcement.
2-8
Chapter 2, Literature Review
The use of GFRP bars as replacement of tensile steel bars can also reduce the overall cost
of construction if one takes into account the cost associated with maintenance and
prolonged durability [Al-Salloum et ai, 1996].
2.5.1 Mechanical Properties of GFRP
The GFRP reinforcement used in Phase II of this study is 12 m.m diameter "C
BAR TM" produced by Marshall Industries Composites, Inc. of the United States, with E
glass as fiber type. C-BAR reinforcing rods with E-glass as fiber type are designated as
Type G C-BAR reinforcing rods. The ultimate tensile strengths of E-glass reinforcing
rods range from 550 l\APa to 1000 MPa, depending on the test methodology, fiber type,
fiber volume fraction and size of bars [Marshall industries composites inc.]. The typical
stress-strain diagram of the bars is a straight line up to the point of failure. The modulus
of elasticity is a function of the fiber type and the fiber volume fraction. A reference
value is 42 GPa. The nominal weight of C-BAR reinforcing rod is 0.25 kglm for 12 mm
diameter bars [Marshall industries composites inc.]. The 12 nun C-BAR deformed bars
have a nominal cross-section barrel diameter and cross-sectional area of 12 mm and 113
mm2, respectively. The surface of the bar is deformed to improve the bond between the
bar and concrete. The defonnations spacing and height of 12 M C-BAR rods are 6.1 and
1.0 mm, respectively.
S.H. Rizkalla et ai, 1997, tested 12M C-BAR reinforcing rods for their material
characteristics. The results of the tension tests they performed indicate that failure
occurred within the anchorage zone with a recorded ultimate stress, ultimate strain and
Poisson's ratio of640 MPa, 1.58 percent and 40.6 GPa, respectively_ Rizkalla et aI also
2-9
Chapter 2. Literature Review
performed pull-out tests on the 12 M C-BAR rods and found out that their bond strengths
in confined concrete is in the order of 21 MPa provided that the compressive strength of
the concrete is at least 44 ~a. The unfactored development length of the 12 M C-BAR
can be conservatively estimated as 180 mm (12 times the diameter).
2.5.2 Durability of GFRP in Concrete
Over the last decade~ fiber reinforced plastic (FRP) such as glass~ have emerged as
one of the most exciting solutions to the deterioration problems caused by the corrosion
of steel reinforcement in structural concrete [Katawaki et al~ 1992]. However, the high
pH value (12.5-13.0) of the concrete pore water creates a potentially damaging
environment for the GFRP reinforcements. It is known that all commercial glass fibers
are based on fused silica. The chemical, physical and mechanical integrity of glass fiber
is provided by a continuous 3-dimensional network of silica-oxygen-silica bonds [Warren
et ai, 1936]. It so happens that this bond is particularly susceptible to hydroxyl attack as
explained by the following chemical equation:
-Si-O-Si- + OR Si-OH + SiO (in solution)
Therefore the drastic strength loss of all commercial glass fibers that are exposed
to strong alkali solutions can be due to the occurrence of the above chemical reaction [B.
A. Proctor, 1985].
The high pH value (12.5-13.0) of normal concrete may cause the corrosion of
fiberglass and thus the degradation of the FRP rebars containing fiberglass. As
2-10
Chapter 2, Literature Review
concluded by Bank et ai, 1995, the main disadvantage of using GFRP arises from the
high alkalinity of the surrounding concrete.
L. C. Bank et al examined the deteriorated E-glass GFRP bars when embedded in
concrete and subjected to environmental conditions. Observations of surfaces and cross
sections of the bars by optical microscopy and SEM revealed a variety of degradation
phenomena. Smooth bars developed surface blisters and showed significant deterioration
of the polymeric matrices in layers close to the surface of the bar to a depth of
approximately 15 fiber diameters. Helically wrapped bars showed degradation of both
the resin and the fiber in the helical wraps and degradation at the interface between the
core and the wraps. Sand-coated bars were found to have developed a dense network of
surface layer cracks surrounding the sand particles which lead to flaking of this layer, as
well as degradation of the interfaces between the three layers in the bar.
Katsuki et al, 1995 used acrylic cases of 10 x 10 x 20 cm capable of
accommodating twenty FRP rods in each case. The cases were kept airtight by filling the
holes for pouring alkali solution and inserting FRP rods with silicone. The part (20cm
long) of the FRP rods (40cm long) which were immersed in alkali solution was the
portion subjected to tensile test. The anchoring parts of the FRP rods were not affected by
alkali. The test medium was 1.0 molll aqueous NaOH at 40°C for GFRP and the
deterioration was detected by tensile test and microscope observation after 7 days of
immersion.
Accelerated aging tests in continuously hot wet conditions had been proven to be
well correlated with real weathering [Aindowet aI, 1984]. A typical accelerated aging
test was proposed by K.. L. Litherland et ai, 1981. In this test, a small block of cement
2-11
Chapter 2. Literature Review
paste or mortar was cast around a glass fiber strand with proper protection to prevent
damage of the fiber at the edge of the block. After 24 hours of curing at 100 percent RH9
specimens were transferred to a suitable storage environmen~ most commonly at 50°C,
for the required period and then tested in direct tension. A linear fonnula was derived to
predict the time required in real environment for the fiber to reach the strength value
obtained in the accelerated test. In a more recent study, Max L. Porter et ai, 1997,
exposed GFRP rebars to accelerated aging in a tank containing alkaline solution with pH
value of 12.5 to 13 at 60°C for 2 to 3 months. This condition, they suggested, was
simulating approximately 50 years of real weather aging. Their results show that the
accelerated aging and the stress corrosion severely reduced the ultimate tensile strength
and the maximum strain capacity of the GFRP rebars.
Nanni, 1992, proposed two procedures for testing prestressed FRP in alkaline
environment. In the first procedure, the prestressed FRP rods were anchored in a test cell
with the central segments of the rods exposed to the alkaline solution, which was
composed of 0.2 percent Ca (OHh, 1.0 percent NaOH and 1.4 percent KOH by weight.
The prestressing forces were at the values of 0.6, 0.7 and 0.8 of the rated capacity of the
rods. The time of stress-rupture failure was recorded or the residual strengths were
obtained through tensile test. In the other procedure, a pretentioned rod was embedded
along the centroidal axis of a concrete prism, 360 mm long and 100 X 100 mm in cross
section. The concrete was maintained wet and at constant temperatures of 20°C and 60
°e. The initial prestressing forces were 0.5, 0.6 and 0.8 of the rated capacity. After 1, 3
and 12 months from construction, the tendons were pulled to failure.
2-12
Chapter 2. Literature Review
The above literature offers a background to the study of the durability of GFRP in
LHHPC. The present experimental program., which is described in detail in chapter 3, is
composed of embedding 500 mm long GFRP bars in a concrete prism. The specimens
are immersed in a water bath maintained at 60°C and tested in tension after the required
curing period of 1, 3, 6, 9, 12 and 24 months. The degree of deterioration is detennined
by the loss of tensile strength in the GFRP bar.
2-13
Chapter 2, Literature Review
Table 2.1, Results of the 28-day LHHPC from CANMET
Temp (OC) Confining Modulus of Poisson's Ratio Ultimate
pressure (MPa) Elasticity (GPa) Stress (~a)
23 0.0 36.26 0.114 74.90
4.S 36.65 0.147 94.03
9.0 35.66 0.110 108.22
18.0 35.06 0.112 122.01
36.0 33.65 0.072 144.S0
50 0.0 34.85 0.188 67.27
4.S 34.89 0.129 90.73
9.0 34.43 0.114 10S.S6
18.0 34.S7 0.126 109.43
36.0 35.38 0.120 122.87
90 0.0 31.30 0.145 66.95
4.5 32.63 0.069 88.18
9.0 32.32 0.131 103.11
18.0 33.90 0.081 108.15
36.0 38.02 0.068 111.00
2-14
Chapter 2., Literature Review
Table 2.2~ Results of the 90-day LHHPC from CANMET
Temp (OC) Confining Modulus of Poisson's Ratio Ultimate
pressure (MPa) Elasticity (GPa) Stress (rvtPa)
23 0.0 38.18 0.144 89.19
4.5 38.84 0.119 110.45
9.0 39.61 0.106 124.76
18.0 39.83 0.200 133.85
36.0 41.25 0.194 148.05
50 0.0 36.92 0.109 81.65
4.5 37.46 0.158 103.65
9.0 38.15 0.128 117.92
18.0 38.19 0.155 125.51
36.0 39.02 0.161 131.86
90 0.0 34.00 0.157 74.93
4.5 34.85 0.126 97.46
9.0 35.21 0.107 113.27
18.0 36.28 0.108 113.99
36.0 37.85 0.102 117.36
2-15
Q)
.~ CIl ~
~ §
I o [) ~
100 ~ -. ::At;:a.w6
1--~------4---~----~~~~~~-tt7'L-------~IIr---------l I • 75 I
50
25
o
Silica flour
0.001 0.01 0.1
Figure 2.1, Particle Size Distribution of the Components of LHHPC (from AECL)
2-16
10
Coarse aggregate
100
~ i 5 ~ Q}
> .-en en
~ ~ ]
i 8
150
125 +-~ LHupe (W/CN - 0.51) .. .. '" .. ~- .... ~ ... -I
--~-- LHHPe CH/CM - 0,59) • SHPC (WICK • 0.24)
100 .-1 ....................~. ....r · ........ " ......
75
50
25
o
... ",
... ~I ~,
,._to ~~o
~"
fI''''
...... ...-::. " ... ___ .w ........ """" .......... w.~~ .. ?... . . "..J. ...... ,,:~~::l f~ Concretes
10
Curing Time (days) - Logscale
Figure 2.2, Strength Development in LHHPC and SHPC (from AECL)
2-17
100
""""' ~ '-'
i ~.l:l cQoo
~.~ .f1 CI)
~~ ~ s-.b 0 oou ~:s 5 ~ r-.J:::I
00 Q) ..-.~ f-
12 , •••.• • ...... .. n. • .
, " " , ,
'I . " n. • .......
--- SHPC Tensile strength ~ LHHPC Tensile strength --~- SHPC M TIC Percent --~- LHHPC - TIC Percent
9 f • t ... "~C' t. • ........ , ... " •• ,. ....... '. n: .•.• If +."U.""' ...... ".,1 4 t,. '" ... ,.. •• ,. " ..... , '1' ... • •• '"
~ - . 6(' ..
3 ...... , .... , 0, .•••••
I ............... -...
I __ • ___ .,.,-. __ ~ 'F ... 14+,.,""""""" ~
J I ,
I I ,
I , I
I.
................... ..,.....,.
v ... -. ................
.................. -0
........ ....... _-_ .. __ ...... _-. III iliA
_ .. . l
0 0 O~---r~~-T~~~-r------MOMM~----~~--~~--~~~~
10 100
Figure 2.3, Tensile Strengths of LHHPC and SHPC (from AECL)
2-18
1 day under water
+ . = . . *- ! . = .
I . 1 7 days under water
SAPC 400 -'-O"- LBHPC
-
1 10 100 1 O00 I 10 1 O0 1000
Time afier casting (days) Time after casting (days)
Figure 2.4, Shnnkage of LHHPC and SHPC with varying duration of water curing ( h m AECL)
13
12~ __ ~----~~ .. --.. --~--------~ ________ ~
11
a
S high performance concrete
Low-heat highpedOiliJ8IICC concn:le
100
Time (days)
200
Figure 2.5, pH ofLHHPC and SHPC as a function of time after casting (from AECL)
2-20
U 0
Q) V'l
~
~ ~ Q)
~ f-4
50T'----------------~--------------~1-, ----------------
40r---o--
-LHHPC SHPC
30 ~ I • 6 ~I
20
10
0
-10 : ' ,. I 4, ., I , i I 10 100 1000
Time After Mixing (days)
Figure 2,6, Temperature Rise in LHHPC and SHPC (from AECL)
2-21
3. ---------------------------- Experimental Program
In this chapter, the experimental program of three phases is described. Detailed
description of the materials used and the instrumentation are also provided.
3.1 Phase I: Material Properties
The experimental program of this phase involves subjecting concrete cylinders to
axial compression stresses.
Casting and curing of all test specimens was conducted according to ASTM C
192 - 90a, Standard Practice for Making and Curing Concrete Test Specimens in the
Laboratory. The test procedure for the modulus of elasticity was done according to
ASTM C 469 - 87~ Standard Test Methodfor Static Modulus of Elasticity and Poisson's
Ratio of Concrete in Compression.
Sixty standard cylinders were cast and tested in compression using an MTS
closed-loop cyclic loading testing machine. The variables included the size of cylinders
(100 mm or 150 mm diameter) and the type of end preparation (either capped or ground).
The cylinders were tested at ages 14, 28, 90 and 180 days. Standard high performance
concrete (SHPC) and normal conventional concrete (NCC) were also tested to provide
Chapter 3. Experimental Program
comparison with LmIPC. Four different batches ofLHHPC were cast and tested in this
investigation.
3.1.1 Materials
The mix design for the four batches of LHHPC is given in Table 3.1. The mix
design for different batches were slightly altered to improve workability and maintain the
desirable strength. Batch 1 has a water-cementitious materials (w/cm) ratio of 0.54 and a
superplasticizer content of 8 kglm3; batch 2 has a w/cm ratio of 0.53 and a
superplasticizer content of 10.32 kg/m3• Batch 3 and 4 have a w/cm ratio of 0.54 and a
superplasticizer content of 10.32 kg/m3• The other constituents of the concrete (cemen4
silica. fume, silica flour, and aggregates) were not altered in the mix design. The
properties of the constituents are described in chapter 2. At the end of the experimental
phase, the mix design used for batch 3 was selected as the acceptable mix fonnulation for
LHHPC. Therefore ail subsequent batches, including those in phase 2 and 3, were done
according to batch 3. Batch 4 was done to confirm the results obtained from batch 3.
The mix design for SHPC is also included in Table 3.1. The mix design for NCe
was not available from the local supplier that provided the concrete.
The various constituents were thoroughly mixed in a power-driven revolving
drum. The materials in the mixer were mixed for three to four minutes each time after
water was added. Upon completion of the mixing, the slump was measured and
recorded. The cylinder molds, made out of plastic, were lightly coated with mineral oil
and then the concrete was placed. The concrete was placed in the molds in three layers of
equal volume using a scoop. Consolidation of the concrete cylinders was done by
3-2
Chapter 3. Experimental Program
rodding. Each of the layers is rodded 25 times using a 16 nun diameter rod for the 150
nun diameter cylinders while the 100 nun diameter cylinders were rodded using a 10 mm
diameter rod 20 times per layer. The cylinders were covered with plastic sheets
immediately after finishing to prevent evaporation of water fron1. the unhardened
concrete. The cylinders were removed from the molds approximately 24 hours after
casting and immediately brought to a curing room., which is kept at a constant
temperature of 23°C and 100 percent humidity. At the end of the curing period, the
specimens were capped in accordance to ASTM C 617 - 87, Standard Practice for
Capping Cylindrical Concrete Specimens. The capping of the cylinders was done at the
University of Manitoba one day prior to testing taking care not to allow moisture loss
from the specimens. The specimens to be ground were shipped to the AECL laboratories,
in the wet condition, for end grinding and then shipped back to the University of
Manitoba Research and development facilities for testing.
3.1.1 Instrumentation and Test Procedure
The tests were conducted at room temperature, maintained at approximately 23°C.
The load was applied using a MTS closed-loop cyclic loading testing machine under a
stroke control rate of 0.15 mmlmin. The test setup is shown in Figure 3.1 (a) and (b).
The test procedure conforms to ASTM C 469-87a (Standard Test Method for Static
Modulus of Elasticity of Concrete) and C 39 (Standard Test Method for compressive
Strength of Concrete). The cylinders were instrumented with an electrical extensiometer,
which is calibrated to read the axial strain of the concrete cylinder. The data acquisition
3-3
Chapter 3~ Experimental Program
system automatically recorded the axial strain of concrete cylinders from the
extensiometer and the load from the machine and the data was saved into a file.
3.2 Phase II Structural Behaviour
The program included eight singly reinforced LHHPC beams tested in flexure to
failure. The various parameters considered in the program are the reinforcement ratio
and the type of reinforcement. The beams are 150 X 350 nun, with a total length of 4.0
m, as shown in Figure 3.2. The beams are simply supported with a 3.7 m clear span. A
summary of the overall dimensions and reinforcement ratio of the specimens is given in
Tables 3.2 and 3.3 for steel and GFRP reinforcements, respectively. An additional four
beams fabricated with NCC were also tested in this phase and used as control specimens.
3.2.1 Materials
The average compressive strength of the concrete for the LHHPC and NCe, at the
time of testing, used for the beams reinforced by steel was 80 and 40 MPa, respectively.
The average values for the beams reinforced by GFRP were 82 and 38 MPa for LIllIPC
and Nee, respectively. The measured yield stress of the steel reinforcement was 425
MPa with elastic modulus of 177,000 MPa, tested according to ASTM A 370 (Standard
Test Methods and Definitions for Mechanical Testing of Steel Products). The GFRP
reinforcement used in this study was "C-BAR TM" produced by Marshall Industries
Composites, Inc. of the United States. The bars have a nominal diameter of 12 nun and
consists of E-Glass fibres and an epoxy resin matrix. The measured maximum tensile
3-4
Chapter 3~ Experimental Program
strength and the modulus of elasticity of the GFRP bars were 532 MPa and 34,300 MPa,
respectively. The measured average ultimate tensile strain of the bars is 0.015. The
stress-strain diagrams for the reinforcing steel and GFRP bars are shown in Figures 3.3
and 3.4, respectively.
3.2.2 Instrumentation
The beams were instrumented by (a) three electrical strain gauges mounted on the
longitudinal tensile reinforcement in the constant moment zone to measure the tensile
strain; (b) one Pi Gauge fixed to the top concrete surface in the constant moment zone to
measure the concrete compressive strain; and (c) two Linear Variable Displacement
Transducers (L VDT) located at mid-span to measure the midspan deflection. The load
was applied using an MTS closed-loop cyclic loading testing machine under a stroke
control rate of 0.50 mmlmin. The beams were monotonically loaded at two points load
configuration, as shown in Figures 3.5(a) and (b), and loaded to failure. During the test,
the applied load, the vertical deflection at mid-span, the strains in the longitudinal tensile
reinforcing bars, and the compressive strain of the concrete in the constant moment zone
were recorded using a 16-channel data acquisition system. Prior to testing, the beams
were painted with a latex white paint to facilitate locating and mapping the crack
initiation and propagation. Cracks were marked and crack widths were measured at each
load increment.
3-5
Chapter 3, Experimental Program
3.3 Phase III Durability Aspects
This phase is subdivided into two parts. The first part includes investigation of
the durability of the LHHPC subjected to freezing and thawing cycles. The second part
of Phase III is designed to study the effect of the low alkalinity of LHHPC on the
durability of reinforcement. The two kinds of reinforcements considered are GFRP and
steel.
3.3.1 Freeze-Thaw Cycles
The program includes casting three batches of LHHPC with different air content.
Nine prisms were cast (three from each batch) and subjected to cycles of freezing and
thawing. The casting and curing of specimens followed the same procedure described in
Phase 1. The fundamental transverse frequency (FTF) of the prisms was measured at
intervals up to a total nwnber of cycles of 300 at which the testing was terminated. In
addition to the prisms, nine standard concrete cylinders were cast and tested at 28 days to
determine the effect of the percentage of air content on the compressive strength.
3.3.1.1 Materials
The constituents of the batches include cement (type 50), silica fume, silica flour,
fine and coarse aggregates, superplasticizer, water and air entrainment admixtures
(AEA). The amount of AEA was varied to study the effect of the air entrainment ratio
while the other constituents are kept the same. The mix design and the properties of the
different batches are given in Table 3.4. The only difference in the constituents of the
3-6
Chapter 3~ Experimental Program
different batches shown in Table 3.4 is the amount of AEA. It can be seen that increasing
the amount of AEA increases the slump and the air content and decreases the unit weight
of the concrete.
3.3.1.2 Methodology
Three prisms (76 X 100 X 400) together with three standard 150 nun diameter
concrete cylinders were cast from each batch. The prisms and the cylinders were cured in
98 percent humidity and at a temperature of 23 °C. Freeze-thaw cycling for the prisms
started after 14 days of curing. The FfF of the specimens was measured prior to cycling.
The freeze-thaw cycling was stopped at intervals of approximately 20 cycles to measure
the FTF of the specimens. The specimens were protected from moisture loss while they
were out of the cycling apparatus. The position of the specimens in the apparatus was
rotated and turned end-for-end when returned This ensures that the specimens are
subjected uniformly to similar exposure.
The freeze-thaw cycling machine was set to complete one cycle in 3.5 hours. A
cycle consisted of lowering the temperature of the specimens from 4.4 to -18 °C followed
by increasing the temperature from -18 to 4.4 °C. The test methodology was according to
ASTM C 666 - 92, Standard Test Method for Resistance of Concrete to Rapid Freezing
and Thawing, procedure A (Rapid Freezing and Thawing in Water).
The measurements for FTF was done according to ASTM C 215 - 91, Standard
Test Method for Fundamental Transverse Frequency of Concrete Specimens. The
method adopted was the forced resonance method. In this method, the specimen is forced
to vibrate by an electro-mechanical driving unit. The specimen response is monitored by
3-7
Chapter- 3. Experimental Program
a light weight pickup unit on the specimen. The driving frequency is varied until the
measured specimen response reaches maximum amplitude. The value of the frequency
causing maximum response is the resonant frequency of the specimen. A specimen being
tested for fundamental transverse frequency is shown in Figure 3.6 (a). Figure 3.6(b) is a
schematic of a test specimen showing the locations of the driver and needle pickup units
for the fundamental transverse frequency. The specimen is supported on soft rubber pads
at the nodal points so that it may vibrate freely in the transverse mode. The location of
the nodal points for the transverse mode of vibration is 0.224 of the length of the
specimen from each end. Vibrations are a maximum at the ends, approximately three
fifths of the maximum at the center, and zero at the nodal points.
The axial compressive strength and the modulus of elasticity was determined in
accordance with ASTM C469 - 87a, Static Modulus of Elasticity and Poisson's Ratio of
Concrete in Compression. Nine 150 rom diameter concrete cylinders, three from each
batch, were tested for compressive strength, modulus of elasticity and stress strain
characteristics using an MrS closed loop testing machine.
3.3.2 Durability of GFRP in LHHPC
The program included casting a total of 20 LHHPC and 20 Nee specimens. Each
specimen contained 500 mm GFRP bar (Isorod™), 15 mm diameter, located at the center
of a concrete specimen as shown in Figure 3.7 (a) and (b). The GFRP bars were
machined in the middle section to reduce the cross sectional area to one half its initial
value. The length of the reduced section was 80 nun. Therefore rupture of the specimens
was expected to occur within the middle 80 DUD length. These details were selected to
3-8
Chapter 3. Experimental Program
expose the glass fibres directly to the alkali effect of the concrete pore waters and help
accelerate the process of deterioration.
Four threaded steel rods were cast in each end of the concrete to apply tension to
the concrete specimen. A gap of 10 rom was provided in the middle of the specimen
between the threaded rods to ensure cracking of the concrete specimen at this location
an~ consequently, rupture of the bar within the reduced section of the bar. A 40 nun
notch was introduced along the middle segment of the specimen prior to loading to
predetermine the location of the crack due to the applied tension loads. Based on the
section and the material properties use~ the cracking load of the concrete was predicted
to be 10 kN. Otherwise, if the concrete section was not notche~ the cracking load of the
125 X 125 specimen concrete would have been approximately 78 kN.
The casting procedure followed the same methodology used in phases I and II.
The specimens were stripped from the fonns after three days and then brought into the
hot water bath. The bath was maintained at a temperature of 60 ac. Three specimens
from each concrete batch were removed from the hot water bath and subjected to axial
tension to evaluate the tensile strength of the GFRP bars after 1, 3, 6, 9 and 12 months of
curing. Figure 3.5 shows the important days in this research and the activities performed
on those days. It is important to note that most of these activities are long term plans that
will be carried out by future researchers.
The tensile strength of the GFRP bars after 36 days of exposure in the concrete
environment at 60 ac were determined. A constant tension force was applied to the
concrete specimen at a stroke control rate of 0.5 rom per minute. The results of these
tests are presented in chapter 4.
3-9
Chapter 3~ Experimental Program
3.3.3 Durability o(Steel in LHHPC
This part of the durability study was designed to study the effect of the low pH of
LHHPC on the corrosion of steel. It was expected that the low pH of LffilPC would
accelerate the corrosion of steel reinforcement. Generally, steel reinforcement is
protected against corrosion by the highly alkaline concrete-pore solution (PH in excess of
12.5). Such alkaline environment causes the passivation of the steel, that is an
impermeable oxide layer is fonned on the steel surface protecting it from corrosion. This
passivation may be impaired by either a reduction in the alkalinity of the concrete or by
the presence of a sufficient amount of chloride ions.
The specimens for this particular investigation had dimensions of 125 X 125 X
500 mm with a 500 mm 15 M steel rod centered in it. The specimens had the same
dimensions as the specimens for the investigation of the durability of GFRP in concrete.
The specimens for the investigation of the corrosion of steel are for qualitative studies
only; therefore no threaded rods are embedded to transfer the tension to the steel. The
specimens were notched in the middle after they were stripped, before immersing into the
water bath, to make sure that it was cracked and to facilitate the migration of water to the
steel reinforcement and accelerate corrosion. Only three specimens were made from each
concrete type of LHHPC and NeC. The specimens were stripped from their forms after
three days from casting and immersed in a water bath. The specimens were taken out of
the water bath after one month and kept in air for two weeks. This process was repeated
until the required curing period of 6, 12 or 24 months was reached. After the required
curing period, the specimen was to be cracked at various locations to qualitatively study
the extent of corrosion and to note any difference between the steel embedded in LHHPC
3-10
Chapter 3" Experimental Program
and Nee. Table 3.5 also provides the test dates for these sets of specimens.
3-11
Chapter 3. Experimental Program
Table 3.1, Mix Design for LHHPC and SHPC, Quantities in kglm3
LHHPC SHPC
Component Batch 1 Batch 2 Batch 3 & 4
Portland Cement (type 50) 97.02 97.02 97.02 497.00
Silica Fume 97.02 97.02 97.02 49.7
Silica Flour 193.85 193.85 193.85 0.00
Fine Aggregates 894.74 894.74 894.74 703.20
Coarse Aggregates 1039.59 1039.59 1039.59 1101.00
Superplasticizer 8.00 10.32 10.32 5.5
Water 93.74 88.59 90.54 118.14
W/cm 0.54 0.53 0.54 0.23
3-12
Chapter 3, Experimental Program
Table 3.2, Details of Beams Reinforced by Steel
Beam Type of b, d. rc Ee fy Es As p Age of
Design Concrete mm mm (MPa) (GPa) (MPa) (GPa) (mm!) (%) Concrete at
Testing ation·
(days)
LS1.8-1 LHHPC 150 300 80 39.5 450 177 800 1.8 33
LS1.8-2 3S
LS2.7-1 1200 2.7 39
LS2.7-2 42
NS1.8-1 NCC 150 300 40 33.6 450 177 800 1.8 28
NS2.7-1 1200 2.7 32
Table 3.3, Details of Beams Reinforced by GFRP
Beam Type of b, d. rc Ec fu Es As p Age of
Design Concrete mm mm (MPa) (GPa) (MPa) (GPa) (mm2) (%) Concrete at
Testing ation
(days)
LOO.S-l LHHPC ISO 300 82 33.4 532 34 226 0.5 53
LOO.S-2 60
LGI.S-l 678 1.5 48
LGl.S-2 50
NOO.S-I NCC 150 300 38 36 532 34 226 0.5 34
NG1.5-1 678 1.5 36
• The first two letters In the beam desIgnation refers to the type of concrete and the type of remforcement: L refers to low heat high performance concrete (LHHPC) and N refers to nonnal conventional concrete (NCe). S refers to steel reinforcement and G refers to glass fibre reinforced polymer (GFRP) reinforcement.
3-13
Chapter 39 Experimental Program
Table 3.4; Mix Design and the Properties of the Different Batches of the Freeze .. Thaw
Samples
Constituents Quantity in kglm.) for different batches
Batch 1 Batch 2 Batch 3
Cement 97.02 97.02 97.02
Silica fume 97.02 97.02 97.02
Silica flour 193.85 193.85 193.85
Fine aggregates 894.74 894.74 894.74
Coarse aggregates 1039.59 1039.59 1039.59
Superplasticizer 10.32 10.32 10.32
Water 108.60 108.60 108.60
AEA (ml/kg of concrete) 0.000 0.310 0.571
Slump(mm) 220 230 240
Unit weight (lqifm") 2474 2396 2229
Air Content (%) 1.6 4.6 10.0
3-14
Chapter 3. Experimental Program
Table 3.5, Test Dates for Durability Specimens for Steel and GFRP Reinforcement
Date Activity
Thursday, December 10, 1998 Cast specimens made from NeC
Thursday, December 17, 1998 Cast specimens made from LHHPC
Friday, January 15, 1999 Tension test for GFRP embedded in Nee for 36 days
Friday, January 22, 1999 Tension test for GFRP embedded in LHHPC for 36 days
Thursday, March 4, 1999 Tension test for GFRP embedded in NCC for 3 months
Thursday, March 11, 1999 Tension test for GFRP embedded in LHHPC for 3 months
Thursday, June 10, 1999 Tension test for GFRP embedded in NCe for 6 months
Qualitative study of corrosion of steel embedded in NeC for 6 months
Thursday, June 17,1999 Tension test for GFRP embedded in LHHPC for 6 months
Qualitative study of corrosion of steel embedded in LHHPC for 6 months
Thursday, September 9, 1999 Tension test for GFRP embedded in NCC for 9 months
Thursday, September 16, 1999 Tension test for GFRP embedded in LHHPC for 9 months
Thursday, December 9, 1999 Tension test for GFRP embedded in NCe for 12 months
Qualitative study of corrosion of steel embedded in Nee for 12 months
Thursday, December 16, 1999 Tension test for GFRP embedded in LHHPC for 12 months
Qualitative study of corrosion of steel embedded in LHHPC for 12 months
Thursday, December 7, 2000 Tension test for GFRP embedded in Nee for 24 months
Qualitative study of corrosion of steel embedded in Nee for 24 months
Thursday, December 14,2000 Tension test for GFRP embedded in LID-IPC for 24 months
Qualitative study of corrosion of steel embedded in LHHPC for 24 months
3-15
Figure 3.1 (a), Picture of Cylinder in a Compression Testing Machine
Figure 3.1 (b), Schematic of Testing System
2
~~
d
"
I ~~
d/2 ~,
pin
~~
d/2
" I
3-16
1 Top Loading Plate
-""l1lI d .. ... -po
S train ring
E xtensiometer
... -..... Test Specimen
I Bottom Plate
loading points
\ v r.r\.f:)"" V / -Strain gauge ~
~ ~ 13-6 f 6 mill steel bar
~5() . .
150 1300 1100 1300 ]50
3m'IDJ 30!lO 300IO 30iD 50 4 15M dcfonned • 6 15M dcfonllcd 2 ) 2M defonncd • 6 12M dcfonllcd
50 steel bars 50 GFRPbars 50 GFRP bars ~ steel bars ......---.,. ~ ...--.. 150 150 150 150
design for beams dcsign for beams design for beams design for beams
reinforced by stcel reinforced by stcel rcinforced by GFRP rcinforced by GFRP p:::: 1.8% p:::2.7% p = 0.5% P = 1.5%
Figure 3.2, Design and Instrumcntation for Bcams Rcinforced by Stcel and GFRP
3-17
700 -,-------------- -.---- --.- -- -- .-- ...... --
600
500 -
i 400
:I -en
! tn 300-
200 .
100
o .----------.. --- .---. o
T
5
Figure 3.3, Stress-Strain Diagram for 15M Steel Reinforcing Bar
.. _--- ---_.- .... -_ .. --- ... ~'------------~-.--'--'.' -------~----.--~--.
Tension Test on 15M Steel Bar Yield Stress = 450 MPa Strain at yield = 2.7 * 10.3
Modulus of elasticity = 194 GPa
-I' -J'
10 15 20 25
Strain X 103
3-18
600 -,---------.--
500
Tension Test on 12M C-Bar Reinforcing Rod
'ii' Q. ~
400
-= 300 .
;;
200 -
100 -
o -r---· o
Stress at rupture = 531.8 MPa Strain at rupture = 15.39 * 10-3
Modulus of elasticity = 34.0 GPa
. ,--- -r I
2 4 6
Figure 3.4. Stress-Strain Diagram for 12M C·Bar Reinforcing Rod
8 10 12 14 16 18
Strain X 103
3-19
Figure 3.5(a), Beam Test Set-Up
Figure 3.5 (b), Schematic of Beam Test Set-Up
.. Load Cell Reinforcement Strain Gauge
i ______ :...:;:; _ _ ..1= __ t::=
.- LVOr
~
3-20
Figure 3.6 (a), Picture of Test Setup for Fundamental Transverse Frequency
Figure 3.6 (b), Schematic for Measuring Fundamental Transverse Frequency
supports
Figure 3.6, Testing of Fundamental Transverse Frequency
3A21
38 J. /Driving point
Pickup unit
Figure 3.7 (a), Tension Specimen to Investigate the Durability of GFRP in Concrete
Four 12 mm diameter threaded steel
rods to apply tension on the GFRP rod Bar cross section reduced
Spirals for confinemen of the concrete around
t
the threaded rods -- rt-II
, .. Figure 3.7 (b), Schematic Drawing of Tension Specimens
~, -
I II
,
in this region
- , ~ , "
I n r I I
80 , ...
500
, I
500 X 125 X 125 25 mm Steel Plate bolted to the concrete threaded rod prior to tension
~
- ...
I I I I
\ t ,
, I
I
...
~
...,
V 15 mm diameter GFRPbar
4. ----------- Test Results and Discussions
This chapter presents the results of all the three phases of the experimental
program undertaken in this investigation. Analyses and discussions of the test results are
also described. The results for the different phases are presented separately following the
same sequence used in chapter 3.
4.1 Phase I: Material Properties
Tables 4.1 to 4.13 provide a summary of the measured values for all the tests
conducted in this phase. Results are presented in the form of tables which summarize the
strength (re), the modulus of elasticity (Ee) and the strain at ultimate stress. The stress
strain properties, presented in the form of graphs, are included in this report.
Test results indicated that the compressive strength of LHHPC ranged between 70
and 75 l\1Pa at 28 days. A gradual increase in the strength up to 107 MPa after six
months of curing was also measured for the same concrete batch.
As reported in chapter 3, four separate batches of LHHPC were cast and tested to
provide a comprehensive data of the material properties as affected by age of concrete,
the type of end preparation and water cementitious ratio (w/cm). Tables 4.1 to 3 provide
the measured values of the 150 mm diameter cylinders fabricated from batch 1 and tested
Chapter 49 Test Results and Discussions
at ages 14, 28 and 90 days for LffilPC, NCC and S.HPC. The main objectives for these
tests were to compare the stress-strain behaviour of the different types of concrete and the
type of end-preparation (either capped or ground). The 14 and 28-day tests were
conducted using capped cylinders while the 90-day test (Table 4.3) was conducted using
the two types of end-preparation. The value for the modulus of elasticity was measured'
for 28 and 90 days. The results in Table 4.1 to 4.3 suggest that the average compressive
strength of LHHPC increased from 46.7 MPa at an age of 14 days to 60.7 and 70.6 at
ages 28 and 90 days, respectively. The compressive strength of LHHPC was consistently
higher than that ofNCC and lower than that of SHPC. Grinding of the concrete cylinders
resulted in an increase in the average compressive strength up to five percent compared to
capping. The measured average elastic modulus ofLmIPC was 36,250 rvtPa at 28 days.
Table 4.4 gives test results of 150 rom diameter cylinders fabricated from batch 2
and tested at the age of 28 days. The main objectives of these tests were to compare the
accuracy of the testing equipment and the effect of end-preparation. Four cylinders were
tested at the Whiteshell laboratories of Atomic Energy of Canada (AECL) for
compressive strength and six cylinders were tested at the University of Manitoba for
compressive strength and modulus of elasticity. Test results from both labs showed that
grinding of the cylinders gave an average of about four percent higher strength than
capped specimens. Ground specimens showed a lower standard deviation for the
compressive strength than that of the capped cylinders.
Tables 4.5 to 8 summarize the results of the third batch of LHHPC. The
specimens were tested at the ages of 14, 28, 90 and 180 days. All cylinders in this batch
were ground. Two different cylinder sizes were used; 100 mm diameter cylinders which
4-2
Chapter 4. Test Results and Discussions
were mainly used to determine the compressive strength and 150 nun diameter standard
cylinders which was used for both compressive strength and elastic modulus. The height
to diameter ratio of both sizes is equal to two. The strain at ultimate for the 150 mm
diameter cylinders was also measured. Test results of cylinders from this batch indicate
that the average value for compressive strength for LfllIPC increased from 56 MPa at 14 .
days to 104 MPa at 180 days. The average modulus of elasticity also increased from
37,700 MPa to 43,133 MPa at 180 days. The compressive strength obtained from 100
nun diameter cylinders were consistently higher than the compressive strengths obtained
from the 150 mm diameter cylinders by about five percent. The strain at ultimate
increased with the age of concrete, consistent with the measured increase in the
compressive strength.
The fourth batch of LHHPC was identical in the mix design used in batch 3. The
results of the 28, 90 and ISO-day tests are summarized in Tables 4.9 to 11. The fmdings
from this batch in terms of strength, stifthess and stress-strain characteristics are very
similar to those of batch 3. The average value of the compressive strength was 72 MPa at
28 days, 98 MPa at 90 days and 103 MPa at 180 days. The strength of 100 nun diameter
cylinders was on average12 percent higher than the 150 mm diameter cylinders. The test
results of this program suggest that the cylinder size affects the value of the compressive
strength and therefore strength should be quoted according to the size of cylinders.
Tables 4.12 and 13 give the average strength and modulus of elasticity of LHHPC
cast in batch 3 and 4 at different ages for 100 nun diameter and 150 mm diameter
cylinders, respectively. The results from batch 1 and 2 were not included in the average
since they mainly served to reach the adequate mix. design used in batches 3 and 4 and
4-3
Chapter 4, Test Results and Discussions
were also useful to study the effect of end-preparation. Some 100 mm diameter cylinders
are excluded from the average because they failed at an early loading stage due to
improper alignment of the samples in the testing machine. This phenomenon is more
pronounced in small diameter cylinders since they are very sensitive to eccentricities that
occur due to accuracy in alignment. Test results also indicate that the compressive·
strength of LHHPC continues to increase with age. The elastic modulus does- not change
significantly from 14 to 90 days of age but there was a measured increase of 12 percent
from 90 days to 180 days.
The elastic modulus has been correlated with compressive strength in numerous
studies with the result of empirical equations being proposed Existing formulae for
predicting the static modulus of elasticity of concrete, such as that incorporated in CSA
A23.3-94 or that recommended by ACI 318, are written in terms of the compressive
strength and the unit weight of the concrete. The fonnulae are empirically based on
experimental results with the majority of the results for concrete with strengths in the
range of 15 to 40 MPa [Oluokun et ai, 1991]. Ahmad and Shah (1985) proposed one of
the most widely accepted empirically based relationships between the compressive
strength and the static modulus of elasticity for both normal and high strength concretes.
Table 4.13 provides the predicted elastic moduli for LHHPC at different ages based on
the compressive strength (f c) values according to CSA A23.3-94, clause 8.6.2.2, the
predicted elastic moduli by an equation proposed by Ahmad and Shah, PCl Journal,
1985, and by ACI 318-95, clause 8.5.1. The three equations are:
4-4
Chapter 4,1 Test Results and Discussions
E < ~ ( 3300 J 1'< + 6900 ) ~~~ y, eSA A23.3 94, clause 8.6.2.2
Ec = 43r:.s ~f'cXl 0-3, ACI 318-95, clause 8.5.1
In the above equations, both Ec and f c are given in MPa.
CSA A23.3 94 clause 8.6.2.2 underestimates the elastic modulus of LHHPC at 14 days
by 10 percent, but it predicts very accurately the modulus of elasticity at 2S days. The 90
and ISO-day elastic moduli are overestimated by up to 12 percent. The elastic moduli as
predicted by the equation suggested by Ahmad and Shah agrees with the predictions by
CSA A23.3 94 clause 8.6.2.2, within 5 percent. Therefore, CSA A23.3 94 clause 8.6.2.2
could be used to estimate the modulus of elasticity of LHHPC. The prediction of the
modulus of elasticity by ACI 31S-95, clause 8.5.1 is in agreement with the experimental
results at 14 days within 0.5 percent, but overestimates the modulus of elasticity at 28, 90
and ISO days by up to 23 percent.
Figure 4.1 shows the 28 day compression stress-strain curve of SHPC, NeC and
LIrnPC cast in batch 1. The stress-strain graphs for LHHPC, SHPC and NCC are quite
similar in pattern. LHHPC specimens have a higher elastic modulus than NCC
specimens but slightly lower than SHPC specimens. LHHPC has a more linear ascending
branch than NCC but not as much as SHPC.. The strain at ultimate for LHHPC is also
higher than that ofNCC but lower than that of SHPC.
4-5
Chapter 4, Test Results and Discussions
Figure 4.2 shows stress-strain behaviour of four LHHPC cylinders cast from batch
1 and tested at 90 days. Two of the cylinders were capped prior to testing and have
strengths of 68.7 and 72.8 lvIPa while the other two were ground and had compressive
strengths of 74 and 77 MPa. The strength of the specimens with ground ends was on
average 6.7 percent higher than the specimens that were capped. The elastic moduli of .
the ground cylinders are steeper than those of the capped cylinders. The cylinders that
were ground had a 15 percent higher elastic modulus than those that were capped.
Figure 4.3 shows the increase in the strength with age of LHHPC, SHPC and
NCC up to 90 days. The strength of SHPC does not change after 28 days. NCC had a
slight increase in strength of 6 percent from 28 days to 90 days. LmIPC had a 30
percent increase in strength from 28 days to 90 days. This suggests that structures built
with LHHPC are very conservative of the 28 day strength which is stated in the Canadian
Code for structural design. Therefore, the 28 day values underestimate the strength of
concrete in structures using LffilPC. This characteristic, which does not exist for NCC
or SHPC, is considered to be an important advantage.
Figure 4.4 shows stress-strain behaviour ofLHHPC after 14, 28, 90 and 180 days
of curing. There was a gradual increase in strength from 55 MPa at 14 days to 104 MPa
at 180 days. The stiffuess also increased marginally with age, as can be observed in the
increase in the slope of the linear portion of the stress-strain relationship. The strain at
ultimate also increased slightly with age from 14 days to 180 days.
4-6
Chapter 49 Test Results and Discussions
4.2 Phase n: Structural Behaviour
Analyses of the results of testing reinforced concrete beams using LHHPC are
described in tenns of load-deflection behavior, ductility, crack pattern and failure modes
in the following sections.
The maximum loads and the loads at failure for all tested beams are given in
Table 4.14, including the yield load for the beams reinforced by steel. Table 4.14 also
provides the mid-span deflection, tensile strains in the reinforcements and the strains of
the compression zone of the concrete. The ductility index (J,ld), defined by the ratio of the
deflection at failure to the deflection at the load causing yield of the steel reinforcements,
is shown in Table 4.14.
4.2.1 Load-Deflection Behaviour
The load-deflection behaviour of the tested beams show that the deflection
increases linearly with an increase of the applied load in the pre-cracking stage and also
linearly with lower stiffness after cracking until yield of steel or rupture of GFRP
reinforcement as shown in Figures 4.5 and 4.6, respectively. It could also be seen in
Figure 4.5 that beams reinforced by steel (N-S and L-S series for NCe and LHHPC,
respectively) exhibit significant defonnation after yielding of the steel without increase of
the applied load until crushing of concrete in the compression zone. In contrast, beams
reinforced by GFRP, Figure 4.6, (N-G and L-G series for NCC and LfllIPC,
respectively) deflect linearly and proportionally to the applied load until failure.
4-7
Chapter 4, Test Results and Discussions
-In Figure 4.5, the stiffuess of the beams with LHHPC before and after cracking is
consistently higher than that for beams with NCC for the two steel reinforcement ratios of
1.8 percent and 2.7 percent. This behaviour is due to the higher elastic modulus of
LflliPC in comparison to NCe as presented previously in Phase 1. Initial cracking
occurred at loads ranging from 30 to 35 kN at which the calculated equivalent tensile·
strength of concrete is 6.0 .rv1Pa to 8.5 'MFa. Yield of the steel reinforcement for the
beams with a 1.8 percent reinforcement ratio occurred at a load of 131 leN for NCC and
139 kN for LHHPC beams. For the beams with 2.7 percent reinforcement ratio, yield
occurred at a load of 196 leN for NCC and an average load of 209 kN for the LHHPC
beams. The ultimate load of beams with a 1.8 percent reinforcement ratio was on
average 167 kN and 137 leN for LHHPC and Nee, respectively. The ultimate load of the
beams with a 2.7 percent reinforcement ratio was on average 223 kN and 201 kN for
LHHPC the NCe, respectively. The average deflection at ultimate for LHHPC beams
with a reinforcement ratio of 1.8 percent was 64 percent higher than the beams with
Nec. The same behaviour was observed for beams with a 2.7 percent reinforcement
ratio, where the deflection at ultimate was 75 percent higher for beams with LHHPC than
Nce. These results suggest, in general, that the LHHPC exceeded the perfonnance of
NCC in both strength and ductility at the two reinforcement steel ratios used in this
investigation.
The load-deflection curves for beams reinforced by GFRP is linear up to the
initiation of the first crack and continue to be linear with lower stiffuess until failure as
shown in Figure 4.6. The average cracking load for the LHHPC beams with 0.5 percent
GFRP reinforcement ratio was 14.6 kN, while the cracking load of an identical NCC
4-8
Chapter 4. Test Results and Discussions
beam was 13.6 kN. The LffiIPC beams with a 1.5 percent reinforcement ratio first
cracked at an average load of 14 leN, while their identical NCC beam cracked at a load of
15 kN. Therefore, the type of concrete did not affect the cracking load and the behaviour
of the beams with the different types of concrete is identical. The stifthess of the beams
with LHHPC and NCe are very similar for the two reinforcement ratios considered in .
this investigation. Beams with a higher reinforcement ratio have stiffer load-deflection
behaviour, as expected from classical theory of reinforced concrete. The results show
that LHHPC beams have slightly lower strength and deflection at ultimate load than their
corresponding NCe beams reinforced by GFRP. However, with the limited number of
beams tested, the slight difference does not suggest any trend in behaviour between
LHHPC and Nce. These results suggest that LHHPC performs in a similar fashion as
Nee for structural concrete reinforced by GFRP.
Figure 4.7 shows the comparison of the load-deflection behaviour of all tested
Nee beams reinforced by steel and GFRP. It can be seen that the load-deflection
behaviour for beams reinforced by GFRP is quite different from the load-deflection
behaviour of the conventional steel reinforcements. These results indicated that the
overall stiffhess of beams reinforced with GFRP is much less than that of beams
reinforced with steel due to the lower elastic modulus of GFRP. The results also
indicated that increasing the reinforcement ratio of GFRP increases the overall stiffitess
of the beams. Therefore, to achieve the same serviceability conditions as the beams
reinforced with steel, the reinforcement ratios of GFRP should be increased
proportionally to the ratio of the elastic modulus of the steel to the GFRP reinforcements.
4-9
Chapter 4, Test Results and Discussions
This ratio is in the order of 5 according to the tension tests perfonned on the steel and
GFRP reinforcement bars used in this program.
Figure 4.8 shows a similar comparison of load-deflection behaviour of LHHPC
reinforced by steel and GFRP. Increasing the reinforcement ratio of GFRP significantly
increases the stiffuess and ultimate load of LHHPC beams, as sho\m in Figure 4.8, .
similar to the perfonnance ofNCC. The behaviour follows the typical behaviour of NCC
structures, which result in reduction of ductility by increasing the steel reinforcement
ratio. One can conclude from these results that LIDIPC is acceptable as a structural
concrete material and can even exceed the perfonnance of NCe due to its higher modulus
and strength.
4.2.2 Crack Patterns and Failure Modes
The failure loads and modes for the tested beams are also summarized in Table
4.14. All the beams reinforced by steel failed by crushing of concrete in the compression
zone.
The crack pattern at failure of LHHPC and Nee beams reinforced with steel and
GFRP are shown in Figures 4.9 and 10, respectively. Cracking in the constant moment
zone consists predominantly of vertical cracks. In the case of steel reinforced beams,
Figure 9, a larger number of cracks at ultimate was observed for beams with a steel
reinforcement ratio of 2.7 percent compared to beams with a reinforcement ratio of 1.8
percent for both types of concrete. It should be noted that both ratios are less than the
balanced reinforcement ratio. It is also important to report that beams with LHHPC have
the same number of cracks as measured for beams with Nee at ultimate.
4-10
Chapter 4. Test Results and Discussions
The occurrence of cracks in beams reinforced with GFRP with reinforcement
ratios of 0.5 percent and 1.5 percent were considerably fewer in number than in beams
reinforced by steel. For the 0.5 percent GFRP reinforcement ratio, crack numbers were
very small due to rupture of GFRP at a very early stage. Increasing the GFRP ratio as
shown in Figure 4.10 increased crack numbers. Therefore, one can conclude that the
behaviour of LHHPC is similar to NCe for both steel and GFRP reinforcements.
The failure mode of beams reinforced by steel is due to crushing of the concrete
in the compression zone after considerable deflection following yielding of the steel
reinforcement.
The beams with LHHPC reinforced by GFRP failed by rupture of the GFRP
reinforcement at average ultimate strains ranging from 0.0100 to 0.0127, as shown in
Figure 4.11. It should be noted that these values are 59 to 75 percent of the specified
ultimate strain of the bar according to the manufacturer. This behaviour is attributed to
defects on the bars observed during tensile tests perfonned on the bars. The concrete
strains for the beams with LHHPC at failure varied from 0.0014 to 0.003. Failure of the
NCC beam, N-G-0.5-1, occurred by rupture of the GFRP reinforcement at an ultimate
strain of 0.0021 while the compressive strain in the concrete was 0.003. The GFRP bar
used for this specimen had a high ultimate strain compared to the other beams that failed
due to rupture of the GFRP reinforcement. The only beam reinforced by GFRP that
failed by crushing of the concrete was N-G-l.5-1 at a maximum concrete strain of 0.004
while the strain in the GFRP reinforcement at failure was 0.015.
Test results suggest that the performance ofLHHPC is similar to NCe when used
as structural members reinforced by steel and GFRP reinforcements. A higher
4-11
Chapter 4, Test Results and Discussions
percentage of GFRP reinforcement is recommended to provide adequate def1ectio~ crack
pattern and strength for both LHHPC and NCC.
4.2.3 Strain Distribution
The strain distribution along the depth of the cross-section of the beam was
determined from the measured values of the compressive strain at the extreme fibre of the
compression zone and the tensile strain in the longitudinal reinforcement. The strain
distribution between th~ top compression layer and the reinforcement is assumed to be
linear. The strain distribution at ultimate for beams reinforced by steel and GFRP are
shown in Figures 4.12 and 13, respectively. For the beams reinforced by steel, in Figure
4.12, it can be seen, as expected from the classical theory of reinforced concrete
structures, that the compressive zone depth at ultimate increases with an increase in the
steel reinforcement ratio as shown clearly for beams L-S-l.8-1 and L-S-2.7-1. The
difference between these two beams is the amount of steel reinforcement. The
compression zone depth for L-S-2.7-1 is 43 percent greater than L-S-l.8-1. For the same
reinforcement ratio of 1.8 percent, the compressive zone depth at ultimate is greater for
beams with NCC than that for beams with LHHPC due .to the higher compressive
strength of LHHPC. This is shown clearly with the two beams L-S-1.8-1 and N-S-1.8-1.
The compression zone depth for N-S-1.8-1 is 13 percent greater than L-S-1.8-1. The
values of strain at ultimate are not available for beam N-S-2.7-1 and L-S-2.7-2 due to
failure of the strain gauges before reaching the ultimate load.
For the beams reinforced by GFRP, the behaviour is similar to beams reinforced
with steel reinforcements. The depth of the compression zone increased as the
4-12
Chapter 4. Test Results and Discussions
percentage of reinforcement increased from 0.5 percent to 1.5 percent Due to the
varying rupture strain of the GFRP reinforcemen4 the increase of the neutral axis depth at
ultimate was not consistent with the increase of the reinforcement ratio.
Strain measurements, which are nonnally used to define the mode of failure,
indicate that LIllfPC behaves similar to NCC as a structural material.
4.2.4 Ductility
The ductility index (Jld) was calculated for beams reinforced by steel in terms of
the ratio of the deflection at ultimate to the deflection at yield of the tensile steel
reinforcement. Ductility is an important factor in the design of reinforced concrete
members as it allows adequate warning and redistribution of loads before failure of the
system.
LflHPC and NCC beams with a reinforcement ratio of 1.8 percent have an
average ductility index of 4.6 and 2.7, respectively. LHHPC and NCC beams with 2.7
percent reinforcement ratio have an average ductility index of 2.7 and 1.5, respectively.
Therefore, LHHPC beams showed, on average, a 75 percent higher ductility than their
corresponding NCe beams. For both LHHPC and NCe beams, increasing the
reinforcement ratio from 1.8 to 2.7 percent reduces the ductility index.
The ductility index was not calculated for beams reinforced by GFRP due to the
lack of yielding phenomena of GFRP reinforcement, which behaves elastically up to
rupture. These results indicate that using LIUlPC may increase the ductility of
structures. This is considered as one of the most desirable characteristics for structures,
especially in the seismic zones.
4-13
Chapter 4, Test Results and Discussions
4.2.5 Analytical Model
In order to predict the behaviour of the test beams, computer program "Response"
version 1.0 [M. P. Collins and D. Mitchell, 1997], was used to determine the moment
curvature response at mid-span. The program was developed to determine the load
deformation response of a reinforced or prestressed concrete cross-section subjected to
moment, shear, and axial load. The program uses the layer-by-Iayer approach and
material characteristics of the concrete and reinforcement to determine the moment
curvature behaviour of a given section.
To compare the analytical model to the experimental results, the LHHPC beams
(L-S-2.7-1 and L-S-2.7-2) and NCe beam (N-S-2.7-1) with 2.7 percent steel
reinforcement ratio, were analysed for their moment-curvature response at mid-span.
The experimental and theoretical response for Nee and LHHPC are shown in Figures
4.14 and 4.15, respectively. The stress-strain results from the compression tests on
concrete cylinders and tension tests on the steel reinforcing materials were used as input
for the analytical data. The iterations from the analytical response was terminated when
the maximum compressive strain in the concrete was equal to the crushing strain in the
experimental concrete beam.
The predicted moment-curvature response was in good agreement with the
experimental behaviour for both LHHPC and NCe in terms of cracking load, yield and
uhimate loads within 3 percent. The stiffuess before and after cracking was also in close
agreement. Given the above resuhs, the computer pro~ ''Response'' could be used to
analyse and predict the load-deformation behaviour ofLHHPC.
4-14
Chapter 4. Test Results and Discussions
4.3 Phase ITI: Durability Aspects
The study of the durability aspects~ as discussed previously ~ is divided into two
main parts: durability in freezing and thawing cycles and the durability of reinforcement
in concrete. The two types of reinforcement considered are GFRP and steel.
4.3.1 Freeze-Thaw Cycles
An important factor in determining the durability of concrete specimens is the
relative dynamic modulus of elasticity (RDIvIE) which can be expressed by the following
equation:
Where:
C = Number of complete freeze-thaw cycles
Ec = RDME after c cycles of freezing and thawing.
Dc = Fundamental Transverse Frequency (FTF) after c cycles of freezing and thawing.
n = FfF at 0 cycles of freezing and thawing.
The FIF decreases (and therefore the RD:ME) as the specimen is subjected to an
increasing number of cycles. That is an indication that deterioration is taking place in the
concrete. Figure 4.14 shows a graph of the average FfF for the different air contents at
each interval. The slight discrepancies in the trend of FfF with increasing number of
cycles are due to the accuracy of the instrumentation.
4-15
Where:
Chapter' 4, Test Results and Discussions
The durability factor (DF) is calculated based on the following equation:
DF = EN (N/300)
EN = relative dynamic modulus of elasticity after N cycles
N = number of cycles at which RDME reaches 60 percent of the initial
modulus or 300, whichever is less.
The RDME is calculated after every interval. The freeze-thaw prism specimens, .
P 1 and P3 reached 60 percent of their initial modulus after 46 cycles while specimen P2
reached 60 percent of its initial modulus after only 29 cycles. Therefore the value ofN to
determine the durability factor for 40 percent loss in RDh-ffi is 46 for specimens PI and
P3 but only 29 for specimen P2. Specimens P4 to P9 did not reach a loss of 40 percent
up to 300 cycles, therefore N value for these specimens is 300. Table 4.15 shows the
values of the number of cycles at which test was tenninated (N) and the durability factor
for all the specimens.
The surfilces of the prisms were observed to peel off as a resuh of repeated cycles
of freezing and thawing. Figure 4.15 shows a picture of the specimens after 300 cycles.
The picture qualitatively shows the extent of deterioration, due to repeated cycles of
freezing and thawing, compared to a control specimen which was continuously cured at a
temperature of 23°C and 100 percent relative humidity. The surface scaling of the
specimens is worst in the specimens with 1.6 percent air content. The surface scaling in
the specimens with 4.6 and 10 percent air content are identical in nature but not as severe
as the specimens with 1.6 percent air content.
4-16
Chapter4~ Test Results and Discussions
4.3.2 Compressive StreDgth
Table 4.16 gives values of the compressive stre~ modulus of elasticity and
strain at ultimate for all the tested cylinders after 28 days of curing. Figure 4.16 shows
the stress-strain characteristics of the cylinders made from the different batches. The
cylinders with 1.6 percent air content had an average 28 day compressive strength of 70.7
MPa. The compressive strength resuhs in Table 4.16 suggest that increasing the air
content of the concrete mix results in a loss of compressive strength. The average'
compressive strength decreased by five percent when the air content was increased to 4.6
percent. There was a 15 percent decrease in compressive strength when the air content
was increased from 1.6 to 10.0 percent.
Similarly, the average modulus of elasticity decreased by 3 percent when the air
content was increased from 1.6 to 4.6 percent. The modulus of elasticity decreased by 15
percent when air content was increased from 1.6 to 10 percent.
The strain at ultimate also decreased with an increase in the amount of air
entrained. Figure 4.17 shows a graph of the compressive strength against air content
superimposed with a graph of the durability factor.
Based on the limited experimental results of compressive strength and durability,
the optimum air content ofLHHPC should be in the order of five percent.
4.3.3 Durability of Reinforcements in LHHPC
This portion of the thesis presents the results of the effects of LHHPC on the
performance of the reinforcing materials for concrete structures.
4-17
Chapter 47 Test Results and Discussions
The results of the tensile tests of GFRP reinforcing rods embedded along the
centroidal axis ofa concrete prism, 500 mm long and 125 X 125 mm in cross-section are
presented. Due to time constraints, this thesis provides only the results of the tensile
strength of the GFRP bars after 36 days of being embedded in a concrete environment
maintained at 60°C. These results are presented in Table 4.17. All the specimens failed
by rupture of the GFRP bar at its reduced section in the middle of the specimen. Figure
4.18 shows one of the specimens at firilure, which represents a typical failure mode for all .
the tested specimens.
The average tensile strength of the GFRP bars embedded in LmIPC is 55.1 kN
and the average tensile strength for the bars embedded in NCC is 56.7 kN. These results
are within experimental variability and no conclusions can be drawn at this point.
Further tests on the GFRP specimens are planned at 6, 9, 12 and 24 months of being
embedded in concrete. The results of the program at the end of the 24 months will
provide a trend in the reduction of tensile strength with duration of exposure in concrete
environment at 60°C.
The resuhs of the qualitative studies of the corrosion of steel in LHHPC are not
available in this thesis due to time constraints.. The first qualitative studies is scheduled
to take place after six months of exposure to the wet and dry cycles currently taking place
on the specimens.
4-18
Chapter 4. Test Results and Discussions
Table 4.1, 14 Day Test for Batch 1
Concrete Mix Specimen # Compressive
Strength (MPa)
LHHPC Bl-14-LH-l * 48.1
Bl-14-LH-2 45.3
SHPC Bl-I4-SH-l 78.3
BI-14-SH-2 80.9
NCC Bl-l4-NC-l 32.3
Bl-14-NC-2 32.0
. . * specimen # IS gIVen as: Batch # - Age - Concrete type - SpecImen sequence .
Table 4.2,28 Day Test for Batch 1 Concrete Mix Specimen # Compressive Elastic Modulus
Strength (MPa) (MPa)
LHHPC Bl-28-LH-l 60.7 36,300
BI-28-LH-2 60.8 36,200
SHPC BI-28-SH-l 94.1 42,100
Bl-28-SH-2 91.0 43,000
NCC Bl-28-NC-l 42.3 32,900
Bl-28-NC-2 46.3 33,400
4-19
Chapter 4, Test Results and Discussions
Table 4.3,90 Day Test for Batch 1 , Concrete Mix Specirnen # End-Finishing Compressive
Strength @Pa)
NCC B 1 -90-NC- 1 Capped 50.0
B 1-90-NC-2 43.8
LHHPC B 1 -90-LH- 1 Capped 66.8
B 1-90-LH-2 70.6
B 1 -90-LH-3 Ground 72.9
SHPC B 1-90-SH- 1 Capped 91.0
B 1 -90-SH-2 90.6
B 1-90-SH-3 Ground 93.4
B 1 -90-SH-4 9 1 .O
not available
Modulus (MPa)
Chapter 49 Test Results and Discussions
Table 4.49 28 Day Test for Batch 2 ofLHHPC
Specimen # End-Finishing Compressive Elastic Modulus
Strength (MPa) (MPa)
Tests Conducted at The University of Manitoba
UM-l Capped 62.7 37,900
UM-2 61.3 34,500
UM-J 59.2 36,600
UM-4 Ground 63.3 35,500
UM-5 63.0 34,500
UM-6 59.7 35,200
Tests conducted at AECL
WS-I Capped 64.0 N/A
WS-2 51.5
WS-3 Ground 65.5
WS-4 64.2
4-21
Chapter 4, Test Results and Discussions
Table 4.5, 14 Day Test for Batch 3 of LHHPC
Table 4.6, 28 Day Test for Batch 3 of LHHPC
Specimen #
B3-14-150-l*
B3-14-150-2
B3-14-150-3
Strength (MPa)
55.9
56.0
52.0
Specimen #
B3-28-150-1
B3-28- 150-2
B3-28-150-3
Elastic Modulus
(MPa)
39,100
38,100
35,800
1 58.6
Strength (MPa)
69.8
71.4
69.8
*Specimen # is given as: batch # - age - cylinder diameter - specimen sequence.
Strain at Utimate
(x 103)
1.8104
1.909
1.9717
N/A
B3-14-100-5
B3-14100-6
N/A
58.0
58.4
Elastic Moduius
W a )
41,100
40,500
39,500
B3-28- 100-5
B3-28- 100-6
Strain at Ultimate
(X 1031
2.187
2.232
2.2496
NIA
70.7
71.1
N/A
Chapter 4, Test Results and Discussions
Table 4.7,9û Day Test for Batch 3 of LHHPC
Specimen #
83-90- 150- 1
B3-90- 150-2
B3-90- 150-3
B3-90- 100-4
B3-90- 100-5
B3-90- 100-6
Table 4.8, 180 Day Test for Batch 3 of LHHPC
Specimen #
B3-180-150-1
B3-180- 150-2
B3-180-150-3
B3-180-100-4
B3- 180- 100-5
B3-180- 100-6
value not inciuded in the average due to prernature failure
Strength (MPa)
86.0
85.4
89.7
90.9
77,4*
92.9
* value not inciuded in the average
Strength ( m a )
104.0
104.0
103.7
66.4'
104.1
104.4
Elastic Modulus
V a )
40,000
38,100
43,100
NIA
Strain at Ultimate
(X 103)
2-386
NIA
2.440
NIA
Elastic Modulus
w a )
42,500
42,900
44,000
N/A
Strain at Ultimate
(X 103)
2.7097
2.7369
2.6644
NJA
Chapter 4y Test Results and Discussions
Table 4.9, 28 Day Test for Batch 4 ofLHHPC
Specimen # Strength (MPa) Elastic Modulus Strain at Ultimate
(MPa) (X 103)
B4-28-150-1 67.7 33,000 2.6798
84-28-150-2 70.6 33,600 2.6977
84-28-150-3 65.8 34,500 2.2406
B4-28-100-4 79.2 N/A N/A
B4-28-100-5 59.0*
B4-28-100-6 76.7
* value not mcluded m the average
Table 4.10, 90 Day Test for Batch 4 ofLHHPC
Specimen # Strength (MPa) Elastic Modulus Strain at Ultimate
(MPa) ex 103)
84-90-150-1 93.3 35,000 3.011
B4-90-150-2 91.7 34,300 3.068
84-90-150-3 91.3 34,000 3.151
B4-90-100-4 103.8 N/A N/A
B4-90-100-5 108.6
B4-90-100-6 N/A
4-24
Chapter 4, Test Results and Discussions
Table 4.11, 180 Day Te5ty Batch 40fLHHPC
Specimen # Strength (MPa) Elastic Modulus Strain at Ultimate
(MPa) (X 103)
84-180-150-1 96.7 33,000 2.6798
84-180-150-2 101.8 33,600 2.6977
84-180-150-3 97.6 34,500 2.2406
B4-180-100-4 98.9 N/A N/A
B4-180-1oo-5 111.4
B4-180-100-6 108.4
4-25
Chapter 4, Test Results and Discussions
Table 4.12., Average Strength at Different Ages for 100 mm Diameter Cylinders
Age (days) Strength (MPa), f' c Standard Deviation
14 58.3 0.305
28 73.2 4.526
90 99.1 8.525
180 107.1 3.487
Table 4.13, Average Strength and Elastic Modulus at Different Ages for 150 nun
Diameter Cylinders
Age Strength Measured Predicted Predicted Elastic Predicted Elastic
(days) f'c Elastic Elastic Moduli Moduli According Moduli
(MPa) Modulus according to to Ahmad and According to ACI
Ec CSAA23.3 Shah, 1985 318-95
(GPa) (GPa) (GPa) CGPa)
14 54.6 37.7 33.8 35.9 37.9
28 69.2 37.0 37.2 38.8 42.7
90 89.6 37.4 41.3 42.1 48.6
180 101.3 41.9 43.4 43.9 51.7
4-26
Chapter 4, Test Results and Discussions
Table 4.14, Summary of Test Results for all Tested Beams in Phase II Yield Maximum Failure J.ld
Beam Type of Type of p Load Ay £Cy Esy Load Au £c Es Load Au £Cu Es Mode of
Concrete Reinforcement (%) (kN) (mm) • 10.3 III 10.3 (kN) (mm) ... 10.3 • 10.3 (kN) (mm) • 10.3 • 10'] Failure
LS-l.8-1 LHHPC Steel 1.8 137 17.4 1.16 2.15 160 73.3 3.21 17.17 148 80.7 3.45 19.21 4.638 Yield
LS .. 1.8 .. 2 139 20.8 0.59 2.30 173 95.2 N/A 14.84 173 95.6 N/A 18.26 4.596 Followed
LS·2.7 .. 1 2.7 202 19.5 1.57 2.23 226 43.4 2.94 7.26 182 49.1 2.77 N/A 2.518 by
LS-2.7-2 203 21.5 1.40 2.46 219 57.4 3.04 15.38 189 62.3 4.04 15.01 2.898 Crushing
NS-l.8 .. ) NeC 1.8 131 19.8 2.10 2.30 137 30.3 2.58 15.46 115 53.6 3.62 17.47 2.707 of
NS-2.1-1 2.7 191 21.4 2.21 2.47 201 28.1 2.28 4.67 72 31.8 N/A N/A 1.486 Concrete
LG-O.5 .. 1 LHHPC GFRP 0.5 N/A N/A N/A N/A 41 47.9 1.39 10.52 41 47.9 1.39 10.52 N/A Rupture
LG-0.5-2 52 71.3 2.22 14.51 53 74.9 2.32 12.60 ofGFRP
LG-I.5-) 1.5 104 57.2 3.04 10.10 104 57.2 3.04 10.10
LG-1.5-2 106 65.9 3.06 12.70 106 65.9 3.06 12.70
NO-O.S-! NCC ~ 64.6 77.8 2.986 20.96 64.6 77.8 2.986 20,96
NO-l.5 .. } 1.5 139 72.6 4.09 15.31 139 72.6 4.09 15.31 Crushmg
of
Concrete
4 .. 27
Chapter 4, Test Results and Discussions
Table 4.15, Durability Factor for the specimens with different air contents
Specimen Air content Number of cycles RD?vfE when Durability Average
(%) when test was test was factor Durability
terminated terminated factor
PI 1.6 46 37.6 5.8 6.1
P2 29 49.0 4.7
P3 46 50.8 7.8
P4 4.6 300 89.2 89.2 81.4
P5 300 73.2 73.2
P6 300 81.9 81.9
P7 10.0 300 90.7 90.7 84.5
P8 300 82.4 82.4
P9 300 80.5 80.5
4-28
Chapter 4~ Test Results and Discussions
Table 4.16, 28 Day Compressive Strength Results for Cylinders with Different Air
Contents
Specimen Air content (%) Compressive Modulus of Strain at ultimate
Strength (MPa) Elasticity (MPa) (X 103)
Cl 1.6 71.8 39.6 2.387
C2 70.6 41.1 2.240
C3 69.6 40.3 2.167 .
C4 4.6 65.8 39.2 2.231
C5 68.0 38.9 2.314
C6 67.7 39.0 2.268
C7 10.0 63.5 34.0 N/A
C8 57.2 35.2 2.176
C9 59.4 34.0 2.195
Table 4.17, Tension Test Results ofGFRP Bars after 36 days of Embedding in Concrete
Concrete Type Specimen # Tensile Average Tensile Standard
Strength (kN) Strength (kN) Deviation (kN)
LHHPC LH-36-1 55.3 55.1 0.416
LH-36-2 54.3
LH-36-3 55.7
Nee NC-36-1 55.4 56.7 0.696
NC-36-2 56.8
NC-36-3 57.8
4-29
100 Specimen E (GPa)
90 NC-1 32.9 NC-2 33.4 LH-1 36.3
80 LH-2 36.2 SH-1 42.1 SH-2 43.0
70
60 ..... ftI a..
:IE - 50 en
! tn
40
30
20
10
o o 0.5
Figure 4.1, 28-Day Stress-Strain In Compression Results from Batch 1
fcu (MPa)
42.3 46.3 60.7 60.8 94.1 91.0
Strain at ultimate
1
2.000 2.212 2.157 2.230 2.683 2.393
1.5
Strain X 103
4-30
LH·2
LH-1 --'"
NC·2
2 2.5 3
80 -"------- -----
70 -
80 -
so
l :i - 40
j 30 -
20 -
10
.. ----- r-- '- --, J -
0 0.5 1
Figure 4.2, Comparison of Different End·
"
L .. G .. 2
Specimen L-C-1 L-C-2 L-G-1 L-G-2
E (GPa)
34.6 36.4 42.7 39.1
fe" (MPa) Strain at ultimate 68.7 2.070 72.8 2.300 77.0 2.190 74.0 2.291
Note: -C .. means the specimen Is capped -G- means the specimen Is ground
,-- r---- "1--- -
1.5 2 2.5
Strain X 103
Preparations, Capped VSt Ground, after 90 Days of Curing 4 .. 31
3
100 -r------···-- .... -~-------
80 .
'i 60
:I -i c ~ In 40-
20 .
o ~-.---- ... - .. o
- ------_. ,- _. ~-
20
Figure 4.3, Strength vs. Age of LHHPC, SHPC and NCC
_ .. , -...... - . -_.- .- .-- -... --- .----1' ........ - .....
40 60 80 100
Age (Days)
4-32
120 -------------_. --.-... -----. -~---. -- --- ........ ---
100
80 --
:: ::E - 60-
! In
40 -
20 -
0-
a --- -------_.,
0.5
Figure 4.4, Changes In Stress-Strain Behaviour with Age of LHHPC Cast In Batch 3
T - 1 - . - I
1 1.5 2 2.5 3 3.5
Strain x 103
4-33
250
200
150 ..
-Z .¥ -" ~
100
50 -
o· ,.--"~--- ... - ,- -
0 10 1-
20
N-S-2.7-1
Failure mode for aU beams was yielding of steel followed by crushing of concrete
"1 ' I
30 40 50
Deflection (mm)
Figure 4.5, lHHPC and NCC Reinforced by Steel 4-34
L-S-1.8-2
L-S .. 1.S-1
l' , I' - " 1-'-'
60 70 80 90 100
160~~-- ----- ~
140 -
120
100
-~ L-G-1.5 .. 1 - 80 -'U
~
60 - N-G .. 0.5-1
40 -
20
o -----.----.------- - ..- . , - . -- , .._--,
o 10 20 30 40 50 60 70 80 90 Deflection (mm)
Figure 4.6. LHHPC and Nce Beams Reinforced by GFRP 4-35
250 ~r<--<--'~
N-S-2.7-1 200
150 -. N-S-1.8-1 -z
~ -'tJ
~ 100 -
50 .
o 'r'--~ ---- - - T' 1<
o 10 20 30 40
Figure 4.7, NCe Beams ReInforced by Steel and GFRP
J .<
50
Deflection (mm)
4-36
1 r'
60 70
N-G-0.5-1
< .... -r
80 90 100
250 T-·--·.-.-·-~~·
200 .
L-S .. 2.7-1 L-S-1.8-2
150 .
-Z .:.= -" • 0
1111 ~I L-G .. 1.5-2 ..J
100 .
L·G .. 0.5 .. 2 50 .
o ·.-·_· __ ··_·····_·--T·· r -. 'I . "f r . "1 "r' ...
0 10 20 30 40 50 eo 70 80 90 100 Deflection (mm)
Figure 4.8, LHHPC Reinforced by Steel and GFRP 4·37
". • ... _.1' ..... __ ..... "'I~·-·r 1";.4, .1,1' ,
'Ir.'f.·~ . I .:~. t i .. { I .~. ~~i~ . j.: I ". '. ". \ ;: .... \~~"\'.~~' .',
!
.] ....... 1 •• \... ('" "'....), ..' , ••• } '.';).:,' ' . .j.," , I .: . i' > ;.:' . ,,' , . .. ) .: 1 ,.~. \. ~" ~ ~ , .;., ':,. \' •.•• ,:;>. '1 ~'.J 'f' .', .'
. '.. I ! \ -I ['k . '\ \ ", '. ..' ~ ;:. ".', I ~ ~ t .. , '. 1 , •
~ .. '-. .' ....,,~. ~. o.l " \ t':, 1 I:. ) · ... /f '. ' .i . . ~~: .:}l~.'" "~~"',l\'" '/1,.) '. - ..... / 1·.,'·. .. .. ~!. .,.(. ..• .'
,:: r'~; i;" ~" i'/;; "~ ";",' ;~J;:~ ,(:: ~';;' ~ ,~.~;., ~ '~':: f:;' .,\;:; • r·~·.' . .,Af ·; . \', \. '." "I! ,~. )'" . '.' .\ \ ; ... t· H: ...•. ,!~ =[.. t', I .• ,; ;~/~,v ~ ,.\ I. ; I 1·\ ) ,'.'
~ ., r 1,1 • '. • : .~: .' 1 I ,- , r /. )', • \ I\. I; • • ... t." I II ,
) .1' ;,.' '.,"" \. ( '.. \ ' " T': ,·'·":'~I
Figure 4,9 (a), LHHPC, p = 1.8 % Figure 4.9 (b), NCC, p = 1.80/0
't~:;~~i ~?~~ l~~~ I \ 'WI
\ . .'r.r\t. . .r, ~ I "11 \ ~'f.~o '. . 0.) ~ ~~l~ ~('
... ~a ,1.,,..,,""
~J .,:;' ,_V:o:,.. .:f'".' ,:r .. ~:t., . . ... j:::"> ,~;~~~ 'j •• {'t"~f'''''' I'" .'. ,I'" /.1 .,.'~' ';0 •••• ,., •• '\" ]' 1'):', ~. ~.;~-.; , ... _.' .~ .. i -',' ,.' 1
'., T.). 'r·.,.J' !.J. '", , (;~ j ,."tj·· .At· :.~/l,"', :1' ....... '" ., ... \ I:. !t'. I '''" '1'1'';;'.)" I~'~
"·f' I,XI '.(1. )'. \ ". ,,' \ .... '1 "A":Y' ' ," • ,I . , • .,' l' i ~ r.., .. . ,
.Itl ~(,))' h'-'-'f' \;j ( f , ..... ~ :'''~ '. ,.' I ~.:~..J.~l.!it~, \ it\ . :' r~'\' ! '! . ~! \, I. I ' . i \ I '., ! ,\ .. ' \! : t·: J1i
J' .... ; ~o (-'~ 1 :;';'
( (Jr, j:.f)
\ :'le~t.2tt '. ~.~l~ l ( \ \ . . ·:~:i
Figure 4.9 (c), LHHPC, p = 2.7 % Figure 4,9 (d), NCC, p = 2.7 0/0
Figure 4.9, Crack Pattern at Failure for Beams Reinforced by Steel, Failure Mode for all Beams is Crushing of Concrete
4-38
Figure 4.10 (a), LHHPC, p = 0.5 %, Failure Mode: Rupture of GFRP
'-."'1":
'\' I~\I .:. I 1,', *
\ ", ,~,1·.. ~ 'J'
\ I '" ~,,, ~r', l
. , "·j~s. J I' f ~ . .....
i\( n
'v
I II ( ;I. J
II,
Figure 4.10 (c), LHHPC, p = 1.5 %,
Failure Mode: Rupture of GFRP
. '. ;1',: ", -:. " .. j ~
...... ·f'.,
"
,I :h' '.'
, .', • II
I
Figure 4.1 0 (b), NCC, P = 0.5 %, Failure Mode: Rupture of GFRP
Figure 4.10 (d), NCC, p = 1.5 0/0, Failure Mode: Crushing of Concrete
Figure 4.10, Crack Pattenl at Failure for Berons Reinforced by GFRP
4-39
160 -r------
140 1
120
100 .
-z .a.: :; 80-
~
60 -
40 -
20 .J..JII~' H
o --- ---o
----~---.-..
/
. .---5
Figure 4.11, Reinforcement Strain for LHHPC and NCC Beams Reinforced by GFRP
- N-G-1.5-1 crushing failure mode
rupture failure mode ,
/lL-G-1.S-1 rupture failure mode
N-G-0.5-1
L-G-0.5-2 rupture failure mode
- 1 --·r·
10 15 20 25
Reinforcement Strain X 103
4-40
150 150 150
45.7 N/A
p;::: 1.8 %
~8 ~I ~s
L-S-l.8-) L-S-l.8-2 N-S-I.8-J
llQ. ill ilU.
p=2.7% 30n
~s c1s ~I 0,0150
L-S-2.7-1 L-S-2.7-2 N-S-2.7-1
Figure 4.12, Strain Distribution at Ultimate for Beams Reinforced by Steel
4-41
150 L.
0,0014 ISO 0,0023 ISO ,/ 0,0013
<I v1. 17.5 3S.0 _ 46.7 I 1
p = 0.5 % LUll L I 300
As AI I ~~ CJ :;. c::::J
0.0126
L-G-O.5~1 L-G-O.5-2 N-G-O.s-}
150 0.0030 ISO 0.0029 ISO 0.0039
~9.31 t:.
Vf60.8 'i /fX63.0 I 1
30(}
l ! I l / I I I
P = 1.S % A4 Ali A. c::l " c:::J " CJ
1 'I _'"
0.0147 -- -r- -r- . -r-
L-G-I.5-l L-G-I.S-2 N-G-I.S·1
Figure 4.13, Strain Distribution at U1timate for Beams Reinforced by GFRP
4 .. 42
140~,----------------------------------------------------------------------------~
120 i /' /' i IN-S-2.7-1 Bcu = -4.083 * 10.3
Analytical
Eo = -3.972 * 10.3
I
100
-E ~ -c 80 C'a Q. en "C
!i 1;; .. 60 c Q)
E 0 :E
40
20
o ~~~--------------------~--------------~-----------------~-------------------~--------------------~-----------------~-------------------------~--------------------~--------------------~ o 5 10
Figure 4.14 Analytical vs. Experimental for NCC Reinforced by Steel
15 20 25 30 35 40 45
Curvature (rad *103 I m)
4-43
160~--------------------------------------------------~========~----------,
140
120
E z 100 ~ -c " i" 'a i 80 -; .., Ii ~ 60 :I
40
20
Analytical Ee = -4.158 ", 10.3
L-S-2.7-2 Eeu = -4.031 * 10.3 L-S-2.7-1
Eeu = -4.041 II 10.3
O+---------------------~------------------~------------------------~------------------~--------------------~--------------------~------------------------~----------------~
o 10
Figure 4.15 Analytical vs. Experimental for LHHPC Reinforced by Steel
20 30 40 50 60 70 80
Curvature (rad *103 I m)
4-44
3.0 -,----- ------------------ --.- _ .... _---..... _ .. -.-. -.~.~.---- ------
2.5 -
N :x: -~
~/4.6%air
c: CD ~ a" 2.0 . ! IL
! ~ c t! 1.5-~
i c
i c ::I 1.0-IL CD
i ~
0.5
0,0 -1-·----------------- -- -----.--.. -----, ---0-
o 50
-, . 100
Figure 4.16, Average Fundamental Transverse Frequency for Freeze-Thaw Prisms
---I -.- r
150 200
Number of Cycles
4-45
0% air
1.6% air
-r -, 250 300 350
4.6~) Air'lO.O % Air
300 Cycles
Figure 4.17, Freeze-Thaw Cycling Specimens after 300 Cycles
4-46
80 .... .. . .. -.... - . - ~- ........ .
70·
60 -
l :s 50 --i UJ CI» 40 .2:
i & 30· CJ
20
10 -
o o
.,.. -, -1
0.5 1 1.5
Figure 4.18, Comparison of Stress .. Straln Diagrams for Cylinders with Different Air Contents
, 2 2.5 3
Compressive Strain X 103
4~47
1 1-
3.5 4 4.5 5
75, --~~---- "------
70 -
-ca a. :IE -5 g- 65 "
~ In
~ 'm e a. E o 60-u >-! GO
'"
55 ·1
50 -.o
•
I
--"-T·· ...
2
•
I
4
Figure 4.19, Compressive Strength and Durability Factor
• Durability Factor
•
....
, . 1 ."
6 8 10
Air Content (%)
4-48
---""-"---"------, 100
1 90
" 80
·70
- 60
50
- 40
1- 30
1- 20
10
··0
12
... ~ :. ~ :s l! :s Q
Figure 4.20, Picture of Durability Tension Specimens at Failure
4-49
5. ------------------------ Summary and Conclusions
Various specific conclusions could be drawn from each of the three phase of the
project.
5.1 Phase I Material Properties
1. The stress-strain heha viour of LIllIPC, in general, is very similar in pattern to
those ofNCC and SHPC.
2. The stress-strain graphs show that LHHPC achieves a higher strength and a higher
ultimate strain at failure in comparison to NCC. Therefore, the ultimate strain for
LHHPC can safely be assumed to be 0.0035 as it is currently stated in the Canadian
Code.
3. LHHPC had an increase in strength of almost 50 percent from 28 days to 180
days. This is an excellent characteristic that does not exist for NCC or SHPC.
4. Test results of the compressive strength tests showed that grinding of the
cylinders prior to testing gives a more reliable value for the strength in comparison to
capping as an end preparation.
Chapter 5~ Summary and Conclusions
5. Test results showed that smaller specimens (100 mm diameter cylinders) have, on
average, five percent more strength than larger specimens (150 mm diameter cylinders).
6. Three empirical equations were used to predict the modulus of elasticity of
LffiIPC. The equation provided by CSA A23.3-94 and the one provided by Ahmad and
Shah, ACI Journal, 1985 gave good estimates of the modulus of elasticity. The equation
provided by ACI 318-95 gave a good estimate for the modulus of elasticity at 14 days age
but overestimates the values at 28 days to 180 days by up to 23 percent. Therefore the
equations recommended by Ahmad and Sh~ ACI Jownal, 1985, and the one provided
by CSA A23.3-94 can be used to estimate the modulus of elasticity of LHHPC.
5.2 Phase n Structural Behaviour
Twelve beams with LHHPC and Nee were tested to failure. The following
conclusions can be drawn.
1. Beams 'With LffiIPC showed similar load-deflection behaviour to beams
fabricated 'With NCC.
2. The ultimate load and deflection \1.ere higher for beams with LfllIPC reinforced
by steel than NeC with the same reinforcement ratio.
3. Ductility of LHHPC beams reinforced by steel were about 70 percent higher than
Nee beams with the same reinforcement ratio.
5-2
Chapter S. Summary and Conclusions
4. The number of cracks at ultimate is about the same for beams with LHHPC in
comparison to beams with NCe.
S.3 Phase III Behaviour under Cycles of Freezing and Thawing
1. The durability of the concrete from freezing and thawing increases with an
increase in the amount of air entrained. There is a great increase in the durability factor
(from 6.1 to 81.4 percent) when the air content is increased from 1.6 to 4.6 percen~ while
the increase in the durability factor when the air content is increased from 4.6 percent to
10.0 percent is only 3.1 percent
2. The compressive strength decreases with an increase in the amount of air
entrained. The decrease in compressive strength when the air content was increased from
1.6 to 4.6 percent was five percent but the decrease was 15 percent when the air content
was increased from 1.6 to 10.0 percent. The modulus of elasticity follows the same trend
as the compressive strength.
3. Given the limited experimental results, the optimum air content appears to be in
the order of five percent when the concrete is to be exposed to any freezing and thawing.
5-3
Chapter 5, Summary and Conclusions
5.4 Durability of Reinforcements
The tensile strengths of the GFRP bars embedded in both LHHPC and NCC are
within experimental variability after 36 days of curing. Other researchers at the
University of Manitoba will report the results of future test specimens.
The qualitative results of the degree of corrosion of steel in concrete will also be
presented by future researchers at the University of Manitoba.
s.s Recommendations for Future Research
1. The current research investigated the material properties of LffiIPC cured at 23
°C and 100 percent humidity up to six months. The compressive strength of
LHHPC was found to increase during the six months of curing when the
compressive of SHPC and NCC reached a threshold after three months of curing
under the same conditions. Future research couId focus on long term properties of
LHHPC to evaluate its threshold ultimate strength.
2. All the beams that were tested in this program were designed to have bond and
shear capacity higher than the flexural capacity so that their flexural behaviour
could be studied. Future research could focus on studying the shear and bond
behaviour of LHHPC with steel and GFRP reinforcements.
3. . The study of the freeze-thaw durability was based on ASTM C 666 - 92,
Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing,
procedure A (rapid freezing and thawing in water). With this practice the
5-4
Chapter 5~ Summary and Conclusions
specimens are subjected to freezing and thawing after 14 days of moist curing.
For LHHPC., the concrete at 14 days would have only gained SO percent of its
strength at six months. LIllIPC specimens with different air content could be
subjected to freeze-thaw cycles after six months of curing to help study the effect
of the high strength on the freeze-thaw durability.
5-5
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