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117 Pages·2009·2.91 MB·English

STEEL FIBER REINFORCED CONCRETE MADE WITH
FIBERS EXTRACTED FROM USED TYRES

BY

NASIR BEDEWI

ADVISOR: PROFESSOR DR. -ING. ABEBE DINKU

A thesis submitted to
The Schools of Graduate Studies of Addis Ababa University
in partial fulfillment of the requirements for the Degree of
Master of Science in Civil Engineering
(Construction Technology and Management)

NOVEMBER 2009
ADDIS ABABA UNIVERSITY
SCHOOL OF GRADUATE STUDIES

FACULTY OF TECHNOLOGY
DEPARTMENT OF CIVIL ENGINEERING

STEEL FIBER REINFORCED CONCRETE MADE WITH
FIBERS EXTRACTED FROM USED TYRES

BY

NASIR BEDEWI

APPROVED BY BOARD OF EXAMINERS:

PROFESSOR ABEBE DINKU (Dr.-Ing)
ADVISOR

INTERNAL EXAMINER

EXTERNAL EXAMINER

CHAIRMAN
DECLARATION

I the undersigned, declare that this thesis is my original work and has not been presented for a
degree in any other university, and that all sources of materials used for the thesis have been duly
acknowledged.

Name Nasir Bedewi
Signature _____________
Place Addis Ababa University, Addis Ababa
Faculty of Technology
Date of submission November 2009
ACKNOWLEDGEMENTS

Acknowledgements to all who have contributed to the completion of this thesis are not an easy
task because so many people have participated in one way or another. To list them all will be
difficult, but I would like to place in record my deep gratitude and indebtedness to my advisor
Prof. Abebe Dinku (Dr. Ing.) for his precious advise, timely response, valuable comments and
guidance. I owe my learning of concrete to him.

I wish to express my sincere thanks to Ato Daniel Kifle, Demis Melaku, Abiy Fanta and Liben
Bekele from the Construction Material Testing Laboratory of Civil Engineering Department at
Addis Ababa University for their devoted assistance from the preparation to testing of the
concrete specimens. I also would like to thank Ato Tasew Mekuria and Masresha Wendimu from
the Mechanical Engineering Workshop of Addis Ababa University for their technical assistance.
My special thanks are also due to Ato Melese and Bisrat for cutting the steel fibers to the
required length and for making them available on time.

My sincere gratitude goes to Ato Alemayehu Emiru, Matador Addis Tyre Research and
Development Manager, and W/ro Abay Gosaye for sharing their experience with no restriction,
for providing the relevant data and for allowing me to carry out the tensile strength of the steel
fibers at their laboratory. My special thanks also go to at Yohannes G. Kidan, Messebo Cement
Factory Quality Control Manager for providing the quality control certificate.

I gratefully acknowledge Addis Ababa University and ENYI Construction for sponsoring the
partial sum of the research expense. I am also thankful to Messay Yohannes and Elias Ahmed for
printing all the number of copies required.

Last but not list, my gratefulness is due to all member of my family, friends, colleagues and all
my well wishers for their whole hearted cooperation, inspiration and encouragement without
which it would have been not only difficult but impossible to complete this work.

Nasir Bedewi
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ABSTRACT

Concrete is considered a brittle material, primarily because of its low tensile strength and low
tensile strain capacity. The low tensile strength of concrete is due to internal flaws and micro-
cracks present in the concrete. The use of randomly distributed, discrete fibers to improve the
mechanical properties of the matrix is an age-old and intuitive concept. Recently, worldwide
researches have been devoted to the use of steel fibers recovered from used tyres in concrete.
The concrete obtained by adding these fibers evidenced a satisfactory improvement of the fragile
matrix, mostly in terms of toughness and post cracking behavior. As a consequence steel fibers
extracted from used tyres appear to be a potential candidate for steel fiber reinforced concrete.

To this effect this research work was undertaken aiming to investigate the mechanical behavior
of concrete reinforced with steel fibers recovered from used tyres and to quantify the benefits
obtained by the concept of SFRC over conventional concrete. For this purpose a bead wire
having a diameter of 0.89 mm extracted from burnt used tyres was used and three grades of
SFRC namely C-25, C-40 and C-60 were produced incorporating three different volumes of fiber
i.e. 0.5%, 1.0%, and 1.5%. Furthermore each volume fraction enclosed three different fiber
lengths namely 20mm, 40mm and 60mm. For comparison purposes, plain control samples were
also considered. The test program included slump test, compressive strength test, impact
resistance test, flexural tensile strength and toughness tests including load-deflection curve,
determination of first-crack point, and toughness index.

Workability of fresh concrete was largely influenced by the presence of steel fiber; on the other
hand it was unlikely to achieve considerable improvements in compressive strength by steel fiber
inclusion. Due to the addition of fibers, the flexural tensile strength and the post-crack energy
absorption capacity were greatly increased. As far as impact test is concerned both the first crack
and ultimate failure strength were enormously improved. The interesting results confirm the
promising application of concrete reinforced with steel fibers extracted from used tyres.
However, further, research work is still necessary in order to have a more in-depth understanding
of the material properties and to evaluate possible practical applications.
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS .......................................................................................................... i
ABSTRACT .................................................................................................................................. iii
LIST OF TABLES ..................................................................................................................... viii
LIST OF FIGURES ..................................................................................................................... ix
LIST OF ANNEXES .................................................................................................................... xi
LIST OF ABBREVATIONS ...................................................................................................... xii

CHAPTER ONE
INTRODUCTION..........................................................................................................................1
1.1 GENERAL .................................................................................................................................1
1.2 OBJECTIVE OF THE THESIS .......................................................................................................4
1.3 RESEARCH SIGNIFICANCE ........................................................................................................4
1.4 METHODOLOGY .......................................................................................................................5
1.5 STRUCTURE OF THE RESEARCH ...............................................................................................6

CHAPTER TWO
COMPREHENCIVE REVIEW OF FIBER REINFORCED CONCRETE ...........................8
2.1 GENERAL .................................................................................................................................8
2.2 HISTORICAL BACKGROUND .....................................................................................................9
2.3 FIBER TYPES ..........................................................................................................................10
2.3.1 Glass Fibers ...................................................................................................................11
2.3.2 Synthetic Fibers .............................................................................................................12
2.3.3 Natural Fibers ................................................................................................................13
2.4 FIBER REINFORCED VERSUS CONVENTIONALLY REINFORCED CONCRETE .............................15
2.5 FIBER MATRIX BOND ............................................................................................................15
2.6 PROPERTIES OF FIBER REINFORCED CONCRETE ....................................................................17
2.6.1 Strength..........................................................................................................................17
2.6.2 Toughness ......................................................................................................................17
2.6.3 Impact Resistance ..........................................................................................................18
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2.6.4 Fatigue ...........................................................................................................................18
2.6.5 Creep and Shrinkage......................................................................................................18
2.6.6 Durability .......................................................................................................................19
2.7 FACTORS AFFECTING PROPERTIES OF FIBER REINFORCED CONCRETE ..................................19
2.7.1 Relative Fiber Matrix Stiffness .....................................................................................20
2.7.2 Volume of Fibers ...........................................................................................................20
2.7.3 Aspect Ratio of the Fiber ...............................................................................................20
2.7.4 Orientation of Fibers ......................................................................................................22
2.7.5 Workability and Compaction of Concrete .....................................................................22
2.7.6 Size of Aggregates .........................................................................................................23
2.7.7 Mixing ...........................................................................................................................23
2.8 MEASUREMENT OF TOUGHNESS AND IMPACT RESISTANCE OF FIBER REINFORCED
CONCRETE ...................................................................................................................................23
2.8.1 Toughness Measurement for FRC .................................................................................24
2.8.1.1 ASTM C 1018 Standard Test Method ...................................................................25
2.8.1.2 JSCE SF-4 Standard Test Method .........................................................................27
2.8.2 Impact Resistance Measurement for FRC .....................................................................27
2.8.2.1 Repeated drop weight test .....................................................................................28
2.9 ECONOMIC EVALUATION OF FIBER REINFORCED CONCRETE ................................................30

CHAPTER THREE
STEEL FIBER REINFORCED CONCRETE ..........................................................................32
3.1 GENERAL ...............................................................................................................................32
3.2 FUNDAMENTALS OF SFRC .....................................................................................................34
3.2.1 Steel Fiber Types ...........................................................................................................34
3.2.2 Steel Fiber Properties ....................................................................................................35
3.2.3 Properties of Freshly Mixed SFRC ...............................................................................36
3.2.4 Properties of Hardened SFRC .......................................................................................38
3.2.4.1 Behavior under static loading ................................................................................38
3.2.4.2 Behavior under impact loading .............................................................................40
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3.2.4.3 Fatigue behavior ....................................................................................................40
3.2.4.4 Toughness and ductility .........................................................................................40
3.2.4.5 Creep and shrinkage ..............................................................................................41
3.2.4.6 Modulus of elasticity and Poisons ratio.................................................................41
3.2.5 Durability of SFRC........................................................................................................41
3.2.6 Mix Design consideration for SFRC .............................................................................42
3.2.7 Mixing, Placing and Finishing of SFRC .......................................................................43
3.2.7.1 Mixing ...................................................................................................................43
3.2.7.2 Placing ...................................................................................................................44
3.2.7.3 Finishing ................................................................................................................45
3.2.8 Curing and Protection ....................................................................................................45
3.2.9 Practical Application of SFRC ......................................................................................45
3.3 STEEL FIBERS EXTRACTED FROM USED TYRE AS REINFORCEMENT IN SFRC ........................47
3.3.1 General ..........................................................................................................................47
3.3.2 Tyre Construction and Composition .............................................................................47
3.3.3 Application for Used Tyres ...........................................................................................49
3.2.7.1 Reuse and retread ..................................................................................................50
3.2.7.2 Reprocess and recycle ...........................................................................................51
3.2.7.3 Energy recovery .....................................................................................................53
3.3.4 Use of Steel Fiber Extracted From Used Tyres .............................................................53

CHAPTER FOUR
EXPERIMENTAL STUDY ........................................................................................................58
4.1 EXPERIMENTAL PROGRAM ....................................................................................................58
4.2 MATERIALS ...........................................................................................................................58
4.2.1 Cement ...........................................................................................................................58
4.2.2 Aggregates .....................................................................................................................59
4.2.3 Water .............................................................................................................................60
4.2.4 Chemical Admixtures ....................................................................................................60
4.2.5 Steel Fiber ......................................................................................................................61
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4.3 MIX PROPORTIONS ................................................................................................................65
4.4 SPECIMEN PREPARATION .......................................................................................................67
4.5 TESTING PROCEDURES ...........................................................................................................67
4.5.1 Testing of Fresh Concrete .............................................................................................67
4.5.2 Testing of Hardened Concrete .......................................................................................68

CHAPTER FIVE
RESULTS AND DISCUSSION ..................................................................................................69
5.1 TEST RESULTS OF FRESH CONCRETE PROPERTIES ................................................................69
4.2.1 Slump Test .....................................................................................................................69
5.2 TEST RESULTS OF HARDENED CONCRETE PROPERTIES .........................................................72
5.2.1 Compressive Strength ....................................................................................................72
5.2.2 Flexural Strength ...........................................................................................................77
5.2.2.1 Flexural tensile strength ........................................................................................77
5.2.2.2 Flexural toughness .................................................................................................83
5.2.3 Impact Resistance ..........................................................................................................98

CHAPTER SIX
CONCLUSIONS AND RECOMMENDATIONS ...................................................................105
6.1 CONCLUSIONS .....................................................................................................................105
6.2 RECOMMENDATIONS ...........................................................................................................107

REFERENCES ...........................................................................................................................109
ANNEXES ..................................................................................................................................111

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LIST OF TABLES
Table 2.1 Physical Properties of some selected glass fibers .....................................................12
Table 2.2 Selected synthetic fiber types and properties ............................................................13
Table 2.3 Typical properties of Some Naturally Occurring fibers ............................................14
Table 2.4 Typical fiber–matrix pullout strength .......................................................................16
Table 2.4 Effects of Aspect Ratio on Strength and Toughness .................................................22
Table 3.1 Range of proportions for normal weight SFRC ........................................................43
Table 3.2 Typical Compositions and Gross Weights of Tyres .................................................48
Table 4.1 Chemical, Physical and Mechanical Properties of the Cement .................................59
Table 4.2 Sieve analysis and physical characteristics of the aggregates ...................................60
Table 4.3 Properties of the Superplasticizer..............................................................................60
Table 4.4 Tensile strength, breaking load and elongation at break of RSF and VSF ...............64
Table 4.5 Summary of geometry and tensile strength of VSF, RSF and ISF ...........................65
Table 4.6 Mix proportions for the three mix series ...................................................................66
Table 5.1 Results of slump values .............................................................................................70
Table 5.2 Average 28 day compressive strength results ...........................................................74
Table 5.3 Average 28 day Flexural Tensile Strength results ....................................................78
Table 5.4 Calculated average Energy absorption ......................................................................84
Table 5.5 Energy Absorption and Toughness Indices for Mix series I .....................................96
Table 5.6 Energy Absorption and Toughness Indices for Mix series II ...................................97
Table 5.7 Energy Absorption and Toughness Indices for Mix series III ..................................97
Table 5.8 Impact resistance test results .....................................................................................99

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