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



4.2.1 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


4.3.2 Compressive Strength

4.3.2 Durability of Reinforcements in LHHPC

5. Summary and Conclusions



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



4.4 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





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

1-2

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

1-3

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


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

2-4


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

2-6


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-

2-7


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


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


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


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


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


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.


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


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


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.


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


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


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


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


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


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


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


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.


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


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


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


-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


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


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


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


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


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


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


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.


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


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


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


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)


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


Table 4.5, 14 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


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


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


(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


Table 4.11, 180 Day Te5ty Batch 40fLHHPC


(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


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


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


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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