abrham_kebede

ADDIS ABABA UNIVERSITY

SCHOOL OF GRADUATE STUDIES

FACULTY OF TECHNOLOGY

DEPARTMENT OF CIVIL ENGINEERING

THE USE OF RECYCLED RUBBER TIRES AS A PARTIAL REPLACEMENT FOR COARSE

AGGREGATES IN CONCRETE CONSTRUCTION

A thesis submitted to the School of Graduate Studies of the Addis Ababa

University in partial fulfillment of the requirements for the degree of Master of

Science in Civil Engineering (Construction Technology and Management)

By Abrham Kebede Seyfu

Advisor: Professor Abebe Dinku (Dr.-Ing.)

June 2010

ADDIS ABABA UNIVERSITY

SCHOOL OF GRADUATE STUDIES

FACULTY OF TECHNOLOGY

DEPARTMENT OF CIVIL ENGINEERING

THE USE OF RECYCLED RUBBER TIRES AS A PARTIAL REPLACEMENT FOR COARSE AGGREGATES IN CONCRETE

CONSTRUCTION

By Abrham Kebede Seyfu

June 2010

Approved by Board of Examiners

Professor Abebe Dinku (Dr. -Ing.)

Advisor Signature Date

Dr. -Ing Adil Zekaria

External Examiner Signature Date

Dr. Esayas G/youhannes

Internal Examiner Signature Date

Ato Geremew Sahilu

Chairman Signature Date

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ACKNOWLEDGEMENTS I am so delighted to seize this opportunity and express my heartfelt gratitude to my advisor

Professor Abebe Dinku (Dr.Ing.). He provided me a lot of expert guidance, valid comments,

suggestions, continuous support and untiring efforts not only while carrying out this research

work but also throughout the entire postgraduate program. His dedication and excellence

have always been an inspiration for my academic and professional career.

I am so thankful to the Addis Ababa University School of Graduate Studies for providing me

the platform to undergo my postgraduate studies and for delivering the financial support

required for this thesis. My Special thank goes to Ato Daniel Kifle and his colleagues in the

Material testing laboratory for their cooperation and assistance while carrying out the various

tests. The mechanical engineering workshop staffs have given their hands while preparing a

modified apparatus for impact resistance test. Their willingness is highly appreciated.

This research work would not have been feasible without the sincere cooperation and support

of the organizations and individuals who have provided me with all the relevant information

and data. These are, Matador Addis Tire, Environmental Development Action-Ethiopia

(ENDA), The Ethiopian Tire and Rubber Economy plant PLC and Traditional tire recyclers

in Addis Ababa. The manual cutting of the tires into the required small sizes was not an easy

task and Ato Shume Gizachew, who is one of the traditional tire recyclers, has helped me a

lot.

I would also like to give thanks to my friends who gave me the encouragement and

unconditional support while carrying out this research. Besides, I am so grateful to all the

people who helped me in one way or the other while carrying out this research.

I am greatly indebted to my family, sisters and brothers for their faith in me. Their support,

encouragement and advice were invaluable. They gave me due attention and delivered what

they can throughout my academic career. They helped me to be where I am today.

Beyond all, my usual thank goes to the Almighty God for He is in all that exists.

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TABLE OF CONTENTS

ACKNOWLEDGEMENTS..……………………………………………………………... i

TABLE OF CONTENTS…………………………………………………………………. ii

LIST OF TABLES………………………………………………………………………… vi

LIST OF FIGURES……………………………………………………………………….. vii

LIST OF ANNEXES……………………………………………………………………… viii

LIST OF ABBREVIATIONS…………………………………………………………….. ix

ABSTRACT……………………………………………………………………………….. x

1. INTRODUCTION……………………………………………………………………… 1

1.1 Background of the Study…………………………………………………………. 1

1.2 Statement of the Problem………………………………………………………… 3

2. OBJECTIVES, SCOPE AND METHODOLOGY OF THE STUDY……………...

5

2.1 Objectives of the Study…………………………………………………………. 5

2.1.1 General Objective…………………………………………………………… 5

2.1.2 Specific Objectives …………………………………………………………. 5

2.2 Scope of the Study……………………………………………………………….. 6

2.3 Methodology of the Study……………………………………………………….. 6

2.4 Terminology ……………………………………………………………………... 7

3. LITERATURE REVIEW……………………………………………………………… 8

3.1 General Characteristics and Constituents of Concrete…………………………... 8

3.1.1 Characteristics of Concrete…………...…………………………………...... 8

3.1.2 Constituents of Concrete………….…..…………………………………….. 9

3.1.2.1 Cement…………………………………………………………………. 9

3.1.2.1.1 Types of Portland Cements…………………….…..……………... 9

3.1.2.2 Aggregates……….……..……………………………………………… 11

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3.1.2.2.1 Natural Aggregates……………………………………………….. 11

3.1.2.2.2 Non Natural Aggregates………………………………………….. 12

3.1.2.3 Water …………………………………………………………………. 13

3.1.2.4 Chemical Admixtures………….………………………………………. 13

3.2 The Use of Recycled Materials in Concrete Construction………………………. 16

3.2.1 General………………………………………….…………………………... 16

3.2.2 Recycling of Waste Tires…………………..……………………………….. 17

3.2.2.1 Composition of a Tire………………………….……………….……… 17

3.2.2.2 The Need for recycling of Waste Tires………………………………… 18

3.2.2.3 Methods of Recycling Tires………………………………..……….…. 22

3.2.2.4 Benefits of Recycled Tires…..…………………………………………. 22

3.3 Material Constituents of Rubberized Concrete……………………………...…… 23

3.3.1 General………………………………………………………………….…... 23

3.3.2 Rubber Aggregate……………………………………………………….….. 23

3.3.2.1 Surface Treatment of Rubber Aggregates……………………………... 28

3.3.3 Natural Aggregates in Rubberized Concrete………………………………. 29

3.3.4 Cement in Rubberized Concrete…………………………………………..… 30

3.3.5 Admixtures in Rubberized Concrete…………………...…………………… 31

3.3.6 Water in Rubberized Concrete……………………………………..……….. 31

3.4 Properties of Fresh Rubberized Concrete………………...……………………… 31

3.4.1 Aesthetics…………………………………………………………….……... 31

3.4.2 Workability ………………………………………………………………… 31

3.4.3 Air Content…………………………………………………..……………… 32

3.5 Properties of Hardened Rubberized Concrete…….……………………………… 32

3.5.1 Unit Weight……………………………………….………………………... 32

3.5.2 Compressive Strength ………………………………………………….…... 33

3.5.3 Tensile Strength…………………………………………………………… 34

3.5.4 Impact Strength and Other Mechanical Properties……...…………………... 34

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3.5.5 Flexural Strength………………………………………..…………………... 35

3.6 Applications of Rubberized Concrete……………………………………………. 36

3.7 Cost Considerations in Rubberized Concrete…………………………………… 38

3.7.1 Used Tire Recycling Costs…......…………………………………………… 38

3.7.2 Cost Savings due to Material substitution …………………………………. 38

3.7.3 Cost Savings through Performance…………………………………………. 39

3.7.4 Whole life Cost reductions ………………………………………………… 40

3.7.5 Cost Savings by Protecting the Environment ………………………………. 40

4. MATERIAL PROPERTIES AND MIX DESIGN…………………………………... 42

4.1 General………………………………………………………………………….. 42

4.2 Cement………………………………………………………………………….. 42

4.3 Aggregates……………………………………………………………………… 42

4.3.1 Properties of the Fine Aggregate………….………………………………… 43

4.3.1.1 Sieve Analysis for Fine Aggregate and Fineness Modulus…………..... 43

4.3.1.2 Specific Gravity and Absorption Capacity for Fine Aggregate……… 45

4.3.1.3 Moisture Content for Fine Aggregate………………………………… 45

4.3.1.4 Silt Content of Fine Aggregate……………………………………….. 45

4.3.1.5 Unit Weight of Fine Aggregate………………………………………. 46

4.3.2 Properties of the Coarse Aggregate…………………………………………. 46

4.3.3 Rubber Aggregate…………...………………………………………………. 48

4.4 Chemical Admixture……………………..………………………………………. 49

4.5 Water…………………………………………………………...………………… 50

4.6 Selection of Concrete Mix Proportions (Mix Design)............................................ 50

4.6.1 General……………………………………………………………………… 50

4.6.2 Testing Arrangement ……………………………………..………………… 51

4.6.3 Trial Mixes……………………………..…………………………………… 52

4.6.4 Batching of Materials…...…………………………………………………... 54

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4.6.5 Mixing And Test Sample Preparation..……………………………………... 55

5. TEST RESULTS AND DISCUSSIONS………………………………………………. 57

5.1 General…………………………………………………………………………… 57

5.2 Fresh Concrete Properties………………………………………………………... 57

5.2.1 Workability Test………..…………………………………………………… 57

5.3 Hardened Concrete Properties……………...…………………………………….. 59

5.3.1 Determination of Unit Weight………………………………………………. 59

5.3.2 Compressive Strength Test ………………………….……………………... 62

5.3.3 Splitting Tensile Strength Test………………………..…………………….. 68

5.3.4 Impact Resistance Tests…………….………………………………………. 72

5.3.4.1 Drop Weight Test……………………………………………………… 73

5.3.5 Flexural Strength Tests……………………………………………………… 75

6. CONCLUSIONS AND RECOMMENDATIONS……………………………………. 79

6.1 Conclusions………………………………………………………………………. 79

6.2 Recommendations………………………………………………………………... 81

REFERENCES……………………………………………………………………………. 84

ANNEXES…………………………………………………………………………………. 87

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LIST OF TABLES

Table 3.1 Typical solid wastes that have been considered as Aggregate for Concrete. 13

Table 3.2 Percentage Composition of a Passenger and a Truck Car …......…… 18

Table 4.1 Sieve Analysis Test for Fine aggregate……………………... 44

Table 4.2 Physical Properties of the Coarse aggregate…………………... 46

Table 4.3 Sieve analysis for Coarse Aggregate……………………….. 47

Table 4.4 Material Constituents of the Trial mix ……………………... 52

Table 4.5 Slump and Compressive Strength Test Results of the Trial mix…..….. 53

Table 4.6 Mix Proportioning for 1m3 of concrete……………………... 54

Table 4.7 Mix Proportions for 0.068 m3 of concrete……………...…………………… 55

Table 5.1 Slump Test Results………………………………………………………….. 57

Table 5.2 Unit Weights of the control and Rubberized concretes…………… 60

Table 5.3 Compressive Strength Test Results ……….………………………………... 63

Table 5.4 Splitting Tensile Strength Test Results……………………... 69

Table 5.5 Impact Resistance Test Results …………………………………………… 74

Table 5.6 Flexural strength Test Results……...……………………. 76

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LIST OF FIGURES

Fig. 1.1 Stockpiles of Waste tires………………………………………………… 3

Fig. 3.1 Samples of Coarse granules of Waste tire………………………………. 25

Fig. 3.2 Mechanically Shredded Fine Tires………………………………………… 26

Fig. 3.3 Tire Rubber cuts of 4.12 mm……………………………………………. 26

Fig. 4.1 Graph for Sieve analysis of Fine aggregate…….………………………… 44

Fig. 4.2 Graph for Sieve analysis of Coarse aggregate…………………………… 47

Fig. 4.3 Used Medium Truck Tires………………………………………………… 48

Fig. 4.4 20 mm size Rubber aggregate…………………………………………….. 48

Fig. 4.5 Rubber aggregates coated with Cement paste…….……………………….. 49

Fig. 4.6 Concrete mixing using a Pan mixer……………………………………….. 56

Fig. 5.1 Slump Test………………………………………………………………… 57

Fig. 5.2 Graphical Comparison of Unit weight values…………….…...…………... 62

Fig. 5.3 Compressive Strength Development…….……………………………….. 65

Fig. 5.4 Comparisons of Compressive strength Test Results..................................... 67

Fig. 5.5 Splitting tensile strength Test……………………………………………… 68

Fig. 5.6 Comparisons of Splitting tensile strength Test Results………………..… 71

Fig. 5.7 Failure patterns of Concrete cylinders after Splitting tensile strength tests.. 72

Fig. 5.8 A Concrete sample arranged for Impact Resistance test…………………... 73

Fig. 5.9 Comparisons of Flexural strength Test Results………………...….…....... 78

viii

LIST OF ANNEXES

ANNEX A Material Properties………………………………………………… 87

A1 Physical properties of fine aggregate……………………………… 87

A2 Physical properties of coarse aggregate…………………………… 88

ANNEX B Mix Design………………………………………………………...... 90

B1 Mix Design for C15 (Trial Mix)………………….............................. 90

B2 Mix Design for C25 (Trial Mix)…………………………………….. 91



B5 Mix Design for C15 (Final Mix)……………………………………. 94




ANNEX C Compressive Strength and Unit weight results 98

C1 7th Day Test Results………………………………………………… 98

C2 28th Day Test Results………………………………………………... 102

C3 56th Day Test Results………………………………………………... 106

ANNEX D Splitting tensile strength test results……………………………… 110

ANNEX E Impact resistance test results……………………………………… 113

ANNEX F Flexural strength test results……………………………………… 116

ANNEX G Photos……………………………………………………………….. 119

ix

LIST OF ABBREVIATIONS CCl4 Carbon tetra chloride

DOE Department of Environment

F.M. Fineness Modulus

Fig. Figure

ggbs Ground granulated blast furnace slag

gm Gram

HRWR High range water reducing

kg Kilogram

Kg/m3 Kilogram per meter cube

Km2 Kilometer square

lt litre

m meter

m3 Meter cube

mm Millimeter

MOC Magnesium Oxychloride Cement

MPa Mega Pascal

Mt Metric Tone

OPC Ordinary Portland cement

SSD Saturated Surface dry

t tone

U.S.A. United States of America

UK United Kingdom

w/c Water cement ratio

wt. weight

% Percent

x

ABSTRACT

Concrete is one of the most widely used construction materials in the world. Cement and

aggregate, which are the most important constituents used in concrete production, are the

vital materials needed for the construction industry. This inevitably led to a continuous and

increasing demand of natural materials used for their production. Parallel to the need for the

utilization of the natural resources emerges a growing concern for protecting the environment

and a need to preserve natural resources (such as aggregate) by using alternative materials

which are recycled or waste materials. In this research, a study was carried out on the use of

recycled rubber tires as a partial replacement for coarse aggregates in concrete construction

using locally available waste tires.

In the first part of this thesis, the background of the study and the extent of the problem were

discussed. A review of relevant literatures was done to study previous works in the subject

matter. The research was carried out by conducting tests on the raw materials to determine

their properties and suitability for the experiment. Concrete mix designs are prepared using

the DOE method and a total of 16 mixes were prepared consisting of four concrete grades

(C15, C25, C30 and C40). The specimens were produced with percentage replacements of the

coarse aggregate by 10, 25 and 50 % of rubber aggregate. Moreover, a control mix with no

replacement of the coarse aggregate was produced to make a comparative analysis. The

prepared samples consist of concrete cubes, cylinders and beams.

Laboratory tests were carried out on the prepared concrete samples. The lists of tests

conducted are; slump, unit weight, compressive strength, splitting tensile strength, impact

resistance and flexural strength tests. The data collection was mainly based on the tests

conducted on the prepared specimens in the laboratory.

The test results were compared with the respective conventional concrete properties and show

that there is a reduction in compressive strength of the concrete due to the inclusion of rubber

aggregates. Even though this may limit its use in some structural applications, it has few

desirable characteristics such as lower density, higher impact resistance, enhanced ductility,

and a slight increase in flexural strength in the lower compressive strength concrete

categories. The overall results show that it is possible to use recycled rubber tires in concrete

construction as a partial replacement for coarse aggregates. Nevertheless, the percentage of

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replacement should be limited to a specified amount and the application should be restricted

to particular cases where the improved properties due to the rubber aggregates are desirable

and when the corresponding demerits of the rubber aggregates don’t affect the use of the

structure.

Key Words: Aggregate, Compressive strength, Concrete, Flexural strength, Impact

resistance, Recycled tires, Rubberized concrete, Splitting tensile strength,

Unit weight, Workability.

1

1. INTRODUCTION 1.1 Background of the Study Cement and aggregate, which are the most important constituents used in concrete

production, are the vital materials needed for the construction industry. This inevitably led to

a continuous and increasing demand of natural materials used for their production. Parallel to

the need for the utilization of the natural resources emerges a growing concern for protecting

the environment and a need to preserve natural resources, such as aggregate, by using

alternative materials that are either recycled or discarded as a waste.

Concrete strength is greatly affected by the properties of its constituents and the mix design

parameters. Because aggregates represent the major constituent of the bulk of a concrete

mixture, its properties affect the properties of the final product. An aggregate has been

customarily treated as an inert filler in concrete. However, due to the increasing awareness of

the role played by aggregates in determining many important properties of concrete, the

traditional view of the aggregate as an inert filler is being seriously questioned. Aggregate

was originally viewed as a material dispersed throughout the cement paste largely for

economic reasons. It is possible, however, to take an opposite view and to look on aggregate

as a building material connected into a cohesive whole by means of the cement paste, in a

manner similar to masonry construction. In fact aggregate is not truly inert and its physical,

thermal, and sometimes chemical properties influence the performance of concrete [1].

Aggregate is cheaper than cement and it is, therefore, economical to put into the mix much of

the former and as little of the latter as possible. Nevertheless, economy is not the only reason

for using aggregate: it confers considerable technical advantages on concrete, which has a

higher volume stability and better durability than hydrated cement paste alone [1].

According to Kumaran S.G. et al, the goal of sustainability is that life on the planet can be

sustained for the foreseeable future and there are three components of sustainability:

environment, economy, and society [2]. To meet its goal, sustainable development must

ensure that these three components remain healthy and balanced. Furthermore, it must do so

simultaneously and throughout the entire planet, both now and in the future. At the moment,

the environment is probably the most important component and an engineer or architect uses

sustainability to mean having no net negative impact on the environment.

2

Among the many threats that affect the environment are the wastes which are generated in the

production process or discarded after a specific material ends its life time or the intended use.

The wastages are divided as solid waste, liquid waste and gaseous wastes. There are many

disposal ways for liquid and gaseous waste materials. Some solid waste materials such as

plastic bottles, papers, steel, etc can be recycled without affecting the environment. However,

studies on how to dispose some solid wastes such as waste tires in the most beneficial ways

are not yet fully exhausted.

Tire is a thermoset material that contains cross-linked molecules of sulphur and other

chemicals. The process of mixing rubber with other chemicals to form this thermoset material

is commonly known as vulcanization. This makes postconsumer tires very stable and nearly

impossible to degrade under ambient conditions. Consequently, it has resulted in a growing

disposal problem that has led to changes in legislation and significant researches worldwide

[3]. On the other hand, disposal of the waste tires all around the world is becoming higher

and higher through time. This keeps on increasing every year with the number of vehicles, as

do the future problems relating to the crucial environmental issues.

Kumaran S.G. et al stated that the increasing piles of waste tires will create the accumulation

of used tires at landfill sites and presents the threat of uncontrolled fires, producing a complex

mixture of chemicals harming the environment and contaminating soil and vegetation. It was

estimated that in the UK alone, 37 million car and truck tires are being discarded annually

and this number is set to increase. This is considered as one of the major environmental

challenges the World is facing because waste rubber is not easily biodegradable even after a

long period of landfill treatment. One of the solutions suggested was the use of tire rubber as

partial replacement of coarse aggregate in cement-based materials [2].

If the tire is burned, the toxic product from the tire will damage the environment and thus

creating air pollution. Since it is not a biodegradable material, this may affect the fertility of

the soil and vegetation. Sometimes it may produce uncontrolled fire. Similarly, the other

challenge to the human society is in the form of carbon dioxide emission and green house

emission. These emissions are considered as highly threatening wastes to the universe [2].

Since 1990, it has been the policy of the State of Arizona that the recycling and reuse of

waste tires are given the highest priority. The Arizona Department of Transportation (ADOT)

has long supported the use of recycled waste tire rubber in asphalt rubber hot mix. A

3

cooperative work between ADOT and Arizona State University (ASU) was conducted to

extend the use of crumb rubber in portland cement concrete mixes. The intent was to use such

mixes on urban development related projects. A list of feasible projects was identified.

Examples are roadways or road intersections, sidewalks, recreational courts and pathways,

and wheel chair ramps for better skid resistance. This collaboration has also expanded to

include members from industry associations, concrete suppliers and consultants. Several

crumb rubber in concrete test sections were built throughout the state of Arizona and are

being monitored for performance [4]. Figure 1.1 below shows stockpiles of waste tires.

Fig. 1.1 Stockpiles of Waste tires [3]

Hence, all the above studies suggest that there is a strong need to use recycled materials in

concrete and specifically waste tires should be used in an environmental friendly way. For

this, concrete construction can be considered as a very realistic and convenient area of

application.

1.2 Statement of the problem Concrete has been a major construction material for centuries. Moreover, it would even be of

high application with the increase in industrialization and the development of urbanization.

Yet concrete construction so far is mainly based on the use of virgin natural resources.

Meanwhile the conservation concepts of natural resources are worth remembering and it is

very essential to have a look at the different alternatives. Among them lies the recycling

4

mechanism. This is a twofold advantage. One is that it can prevent the depletion of the scarce

natural resources and the other will be the prevention of different used materials from their

severe threats to the environment.

It has been well reported that about 1 billion of used automobile tires are generated each year

globally [5]. Specifically, 275 million of used rubber tires accumulate in the United States

and about 180 million in European Union [6]. In Ethiopia, the amount of waste tires is

expected to increase with the increase of vehicles. In addition to that, the traditional ways of

recycling tires in our country like as a shoe making material and other tools is decreasing

nowadays. This is considered as one of the major environmental challenges facing

municipalities around the world because waste rubber is not easily biodegradable even after a

long period of landfill treatment. The best management strategy for scrap tires that are worn

out beyond hope for reuse is recycling. Utilization of scrap tires should minimize

environmental impact and maximize conservation of natural resources. The regulatory

practices include landfill bans and scrap tire fees. Because rubber waste does not biodegrade

readily, even after long periods of landfill treatment, there is renewed interest in developing

alternatives to disposal. One possible solution for this problem is to incorporate rubber

particles into cement-based materials. Scrap tires can be shredded into raw materials for use

in hundreds of crumb rubber products [7].

The other part of the problem is that aggregate production for construction purpose is

continuously leading to the depletion of natural resources. Moreover, some countries are

depending on imported aggregate and it is definitely very expensive. For example, the

Netherlands does not possess its own aggregate and has to import [6]. This concern leads to a

highly growing interest for the use of alternative materials that can replace the natural

aggregates.

Therefore, the use of recycled waste tires as an aggregate can provide the solution for two

major problems: the environmental problem created by waste tires and the depletion of

natural resources by aggregate production consequently the shortage of natural aggregates in

some countries.

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2. OBJECTIVES, SCOPE AND METHODOLOGY OF

THE STUDY 2.1 Objectives of the study 2.1.1 General Objective

Most of the time, used tire rubber is not noticed to be applied in a useful way. It is rather

becoming a potential waste and pollutant to the environment. Moreover, the collecting

process of waste tires is not very costly as compared to the extraction or production of

mineral aggregates used in normal concrete. Hence, this study is intended to show the

feasibility of using crumb rubber concrete in Ethiopia as a partial replacement for coarse

aggregate in concrete. The general objective of this research is to evaluate the fresh and

hardened properties of the concrete produced by replacing part of the natural coarse

aggregate with an aggregate produced from locally available recycled tire rubber.

2.1.2 Specific Objectives

The specific objectives of the research are listed as follows:

1) With the increase in urbanization in Ethiopia, the number of cars and consequently the

amount of used tire is going to increase significantly in the near future. Hence, the non-

environmental nature of these wastes is going to be a potential threat. This study can show

an alternative way of recycling tires by incorporating them into concrete construction. Of

course, the concept that the problem emerges from urbanization and the solution goes

along with it can also be appreciated. Therefore, it is the aim of this study to introduce an

environmental friendly technology, which can benefit the society and the nation.

2) Application of used tires in concrete construction is a new technology and a well-

developed mix design for material proportioning is not available. Through this study, it is

intended to arrive at a suitable mix proportion and percent replacement using locally

available materials by partial replacement of the natural coarse aggregates with recycled

coarse rubber aggregates. Hence the possibility of using waste tires as an alternative

construction material will be investigated.

3) By conducting different laboratory tests on prepared specimens, it is intended to analyze

the results. Moreover, from the properties of the concrete the advantages and

disadvantages of using it will be figured out.

6

2.2 Scope of the study 1) This study concentrated on the performance of a single gradation of crumb rubber. The

waste tires are collected from local sources and manually cut into pieces to achieve a

uniform size of 20 mm, which is the maximum aggregate size in the mix design.

2) The influence of different gradations of the rubber aggregate on concrete properties was

not evaluated in this study but it should be considered in future researches.

3) All the waste tires collected were chosen from those manufactured by Matador Addis Tire

S.Co to avoid any inconsistent properties that may arise by mixing materials from

different sources. The properties of waste tires from other tire manufacturers were not

included in this study.

4) The study was done on four grades of concrete (C15, C25, C30, and C40). The influence

of using recycled tires in high strength concrete was not covered in the present study. The

percentage replacements were limited to three categories i.e. 10, 25 and 50% replacement

of the natural coarse aggregate. The different effects, which can be observed in different

percentages of replacements, were not included in the present study.

2.3 Methodology of the study The different methods utilized in this research include the following:

i) Background study

Literature survey was carried out to review previous studies related to this thesis.

ii) Collection of raw Materials

All the required materials were collected and delivered to the laboratory. These are;

Cement, fine aggregate, coarse aggregate, used rubber tires and admixture.

iii) Material Tests

Tests were conducted on the raw materials to determine their properties and suitability

for the experiment.

iv) Mix Proportioning (Mix Design)

Concrete mix designs were prepared using the Department of Environment (DoE)

method. A total of 16 mixes with four types of concrete grades (C15, C25, C30 and C40)

7

were produced. They were prepared with coarse aggregate replacements by 10, 25 and

50 % of the rubber aggregate. A control mix with no rubber aggregate replacement was

produced to make a comparative analysis.

v) Specimen preparation

The concrete specimens were prepared in the A.A.U, Faculty of Technology, Civil

Engineering Department Material Testing laboratory. The prepared samples consist of

concrete cubes, cylinders and beams.

vi) Testing of Specimens

Laboratory tests were carried out on the prepared concrete samples. The tests conducted

were slump, unit weight, compressive strength, splitting tensile strength, impact

resistance and flexural strength tests.

vii) Data collection

The data collection was mainly based on the tests conducted on the prepared specimens

in the laboratory.

viii) Data Analysis and Evaluation

The test results of the samples were compared with the respective control concrete

properties and the results were presented using tables, pictures and graphs. Conclusions

and recommendations were finally forwarded based on the findings and observations.

2.4 Terminology There are various terminologies given by different researchers to the concrete produced by

replacing recycled tires. In a study by Chou L.H. et al, the resulting concrete formed by the

addition of rubber aggregates was named as ‘rubcrete’ [8]. Whereas Olivares F.H. et al used

the term ‘recycled tire rubber-filled concrete’ [9]. The term ‘rubber modified concrete’ was

referred to the resulting concrete by Kumaran S.G. et al [2]. Other researchers used the

naming ‘rubberized concrete’ in their studies [10-13]. All this terminologies have been used

to describe a similar product formed by incorporating recycled tires. Using varieties of names

at the same time may lead to ambiguity and some confusion over time. To promote clear

understanding of the subject, the term ‘rubberized concrete’ is used throughout this thesis.

8

3. LITERATURE REVIEW 3.1 General Characteristics and Constituents of Concrete 3.1.1 Characteristics of Concrete

Concrete is a composite material composed of coarse granular material (the aggregate or

filler) embedded in a hard matrix of material (the cement or binder) that fills the space

between the aggregate particles and glues them together [14]. In its simplest form, concrete is

a mixture of paste and aggregates. The paste, composed of Portland cement and water, coats

the surface of the fine and coarse aggregates. Through a chemical reaction called hydration,

the paste hardens and gains strength to form the rock-like mass known as concrete.

Concrete is the world’s most important construction material. The quality and performance of

concrete plays a key role for most of the infrastructures including commercial, industrial,

residential and military structures, dams, power plants and transportation systems. Concrete is

the single largest manufactured material in the world and accounts for more than 6 billion

metric tons of materials annually. In the United States, federal, state, and local governments

have nearly $1.5 trillion dollars in investment in the U.S. civil infrastructure. The worldwide

use of concrete materials accounts for nearly 780 billion dollars in annual spending [15].

The ability of concrete to be cast to any desired shape and configuration is an important

characteristic that can offset other shortcomings. Good quality concrete is a very durable

material and should remain maintenance free for many years when it has been properly

designed for the service conditions and properly placed. Of course, proper use of the structure

for the intended function can have a significant role. Through choice of aggregate or control

of paste chemistry and microstructure, concrete can be made inherently resistant to physical

attack, such as from cycles of freezing and thawing or from abrasion and from chemical

attack such as from dissolved sulfates or acids attacking the paste matrix or from highly

alkaline pore solutions attacking the aggregates. Judicious use of mineral admixtures greatly

enhances the durability of concrete. The main advantages of concrete as a construction

material are the ability to be cast, being economical, durability, fire resistance, energy

efficiency, on-site fabrication and its aesthetic properties. Whereas the disadvantages are low

tensile strength, low ductility, volume instability and low strength to weight ratio [14].

Numerous advances in all areas of concrete technology including materials, mixture

proportioning, recycling, structural design, durability requirements, testing and specifications

9

have been made. Innovative contracting mechanisms have been considered, explored and

tried. Some progresses have been made in utilizing some of these technology innovations.

The main concrete making materials are discussed below.

3.1.2 Constituents of Concrete

3.1.2.1 Cement

Cement is a generic name that can apply to all binders. The chemical composition of the

cements can be quite diverse but by far the greatest amount of concrete used today is made

with Portland cements [14]. For this reason, the discussion of cement in this thesis is mainly

about the Portland cement.

Portland cement, the basic ingredient of concrete, is a closely controlled chemical

combination of calcium, silicon, aluminum, iron and small amounts of other ingredients to

which gypsum is added in the final grinding process to regulate the setting time of the

concrete. Lime and silica make up about 85% of the mass. Common among the materials

used in its manufacture are limestone, shells, and chalk or marl combined with shale, clay,

slate or blast furnace slag, silica sand, and iron ore. Each step in the manufacturing of

portland cement is checked by frequent chemical and physical tests in plant laboratories. The

finished product is also analyzed and tested to ensure that it complies with all specifications

[16].

The term "Portland" in Portland cement originated in 1824 when an English mason obtained

a patent for his product. This was because his cement blend produced concrete that resembled

the color of the natural limestone quarried on the Isle of Portland in the English Channel [14].

3.1.2.1.1 Types of Portland Cements Different types of portland cement are manufactured to meet different physical and chemical

requirements for specific purposes. The American Society for Testing and Materials (ASTM)

Designation C 150 provides for eight types of portland cements [17].

TYPE I

Type I is a general-purpose portland cement suitable for all uses where the special properties

of other types are not required. It is used where cement or concrete is not subject to specific

exposures, such as sulfate attack from soil or water, or to an objectionable temperature rise

due to heat generated by hydration. Its uses include pavements and sidewalks, reinforced

10

concrete buildings, bridges, railway structures, tanks, reservoirs, culverts, sewers, water pipes

and masonry units.

TYPE II

Type II portland cement is used where precaution against moderate sulfate attack is

important, as in drainage structures where sulfate concentrations in ground waters are higher

than normal but not unusually severe. Type II cement will usually generate less heat at a

slower rate than Type I. With this moderate heat of hydration (an optional requirement), Type

II cement can be used in structures of considerable mass, such as large piers, heavy

abutments, and heavy retaining walls. Its use will reduce temperature rise which is especially

important when the concrete is placed in warm weather.

TYPE III

Type III is a high-early strength portland cement that provides high strengths at an early

period, usually a week or less. It is used when forms are to be removed as soon as possible, or

when the structure must be put into service quickly. In cold weather, its use permits a

reduction in the controlled curing period. Although richer mixtures of Type I cement can be

used to gain high early strength, Type III, high early- strength portland cement, may provide

it more satisfactorily and more economically.

TYPE IA, IIA, IIIA

Specifications for three types of air-entraining portland cement (Types IA, IIA, and IIIA) are

given in ASTM C 150. They correspond in composition to ASTM Types I, II, and III,

respectively, except that small quantities of air-entraining materials are inter ground with the

clinker during manufacture to produce minute, well distributed, and completely separated air

bubbles. These cements produce concrete with improved resistance to freeze-thaw action.

TYPE IV

Type IV is a low heat of hydration cement for use where the rate and amount of heat

generated must be minimized. It develops strength at a slower rate than Type I cement. Type

IV portland cement is intended for use in massive concrete structures, such as large gravity

dams, where the temperature rise resulting from heat generated during curing is a critical

factor.

11

TYPE V

Type V is sulfate-resisting cement used only in concrete exposed to severe sulfate action

principally where soils or ground waters have high sulfate content.

3.1.2.2 Aggregates

Aggregates generally occupy 70 to 80 % of the volume of concrete and can therefore be

expected to have an important influence on its properties. They are granular materials derived

for the most part from natural rock and sands. Moreover, synthetic materials such as slag and

expanded clay or shale are used to some extent, mostly in lightweight concrete. In addition to

their use as economical filler, aggregates generally provide concrete with better dimensional

stability and wear resistance. Based on their size, aggregates are divided into coarse and fine

fractions. The coarse aggregate fraction is that retained on the 4.75 mm sieve. While the fine

aggregate fraction is that passing the same sieve [14].

Based on their origin, aggregates can be classified as natural aggregates and non natural

aggregates [1].

3.1.2.2.1 Natural Aggregates

Mineral aggregates consist of sand and gravel, stones and crushed stone. Construction

aggregates make up more than 80 percent of the total aggregates market, and are used mainly

for road base, rip-rap, cement concrete, and asphalt. In 1998, roughly 3,400 U.S. quarries

produced about 1.5 billion tons of crushed stone, of which about 1.2 billion tons was used in

construction applications [18]. The sources of mineral aggregates are by directly extracting

from the original sources like river basins or by manufacturing them into a desired shape

from the parent rock in a crasher mill. It was also found out that manufactured sand offers a

viable alternative to the natural sand by providing a higher compressive strength and

delivering environmental benefits [19].

All natural aggregate particles are originally formed as part of a larger parent mass. This may

have been fragmented by natural processes of weathering and abrasion or artificially by

crushing. Thus, many properties of the aggregate depend entirely on the properties of the

parent rock, e.g. chemical and mineral composition, specific gravity, hardness, strength,

physical and chemical stability, pore structure, and color. On the other hand, there are some

properties possessed by the aggregate but absent in the parent rock: particle shape and size,

surface texture and absorption. All these properties may have a considerable effect on the

quality of the concrete, either in the fresh or in the hardened state [1].

12

3.1.2.2.2 Non Natural Aggregates

This category consists of aggregates that are artificial in origin. The reasons for their advent

in concrete construction are:

i) Environmental considerations are increasingly affecting the supply of aggregate.

ii) There are strong objections to opening of pits as well as to quarrying.

iii) At the same time, there are problems with the disposal of construction

demolition waste and with dumping of domestic waste.

However, these types of waste can be processed into aggregate for use in concrete and this is

increasingly being done in a number of countries, for example, in the Netherlands [1]. Wide

varieties of materials come under the general heading of solid wastes. These range from

municipal and household garbage, or building rubble, such as brick and concrete, through

unwanted industrial byproducts such as slag and fly ash or discarded or unused materials such

as mine tailings [14]. Recycled tire rubbers can be categorized under municipal wastes. Table

3.1 below shows the different solid wastes that have been considered as aggregates for

concrete with their composition and the associated industry.

Table 3.1 Typical solid wastes that have been considered as aggregate for Concrete [14].

Material Composition Industry

Mineral wastes Natural rocks Mining and mineral

processing

Blast furnace slags Silicates or alumino silicates of

calcium and magnesium silicate

glasses

Iron and Steel

Metallurgical slags Silicates, aluminosilicates and glasses Metal refining

Bottom ash Silica glasses Electric power

Fly ash Silica glasses Electric power

Municipal wastes Paper, glass, plastics, metals Commercial and household

wastes

Incinerator residues Container glass and metal and silica

glasses

Municipal and Industrial

wastes

Building rubble Brick, concrete, reinforcing steel Demolition

13

3.1.2.3 Water

Water is a key ingredient in the manufacture of concrete. Attention should be given to the

quality of water used in concrete. The time-honored rule of thumb for water quality is “If you

can drink it, you can make concrete with it.” A large amount of concrete is made using

municipal water supplies. However, good quality concrete can be made with water that would

not pass normal standards for drinking water [14].

Mixing water can cause problems by introducing impurities that have a detrimental effect on

concrete quality. Although satisfactory strength development is of primary concern,

impurities contained in the mix water may also affect setting times, drying shrinkage, or

durability or they may cause efflorescence. Water should be avoided if it contains large

amounts of dissolved solids, or appreciable amounts of organic materials [14].

3.1.2.4 Chemical Admixtures

Admixtures are ingredients other than water, aggregates, hydraulic cement, and fibers that are

added to the concrete batch immediately before or during mixing. A proper use of admixtures

offers certain beneficial effects to concrete, including improved quality, acceleration or

retardation of setting time, enhanced frost and sulfate resistance, control of strength

development, improved workability, and enhanced finish ability. It is estimated that 80% of

concrete produced in North America these days contains one or more types of admixtures.

According to a survey by the National Ready Mix Concrete Association, 39% of all ready-

mixed concrete producers use fly ash, and at least 70% of produced concrete contains a

water-reducer admixture [20].

The ASTM C494 specification covers materials for use as chemical admixtures to be added

to hydraulic-cement concrete mixtures in the field for the purpose or purposes indicated by

dividing into eight types as follows [16,17].

Type A - Water-Reducing Admixtures

This category of admixtures usually reduces the required water content for a concrete mixture

by about 5 to 10 percent. Consequently, concrete containing a water-reducing admixture

needs less water to reach a required slump than untreated concrete. The treated concrete can

have a lower water-cement ratio. This usually indicates that a higher strength concrete can be

produced without increasing the amount of cement. Recent advancements in admixture

technology have led to the development of mid-range water reducers. These admixtures

14

reduce water content by at least 8 percent and tend to be more stable over a wider range of

temperatures. Mid-range water reducers provide more consistent setting times than standard

water reducers do.

Type B - Retarding Admixtures

They slow the setting rate of concrete. Therefore, they are used to counteract the accelerating

effect of hot weather on concrete setting. High temperatures often cause an increased rate of

hardening which makes placing and finishing difficult. Retarders keep concrete workable

during placement and delay the initial set of concrete. Most retarders also function as water

reducers and may entrain some air in concrete.

Type C- Accelerating Admixtures

They increase the rate of early strength development by reducing the time required for proper

curing and protection, and speeding up the start of finishing operations. Accelerating

admixtures are especially useful for modifying the properties of concrete in cold weather.

Type D- Water-Reducing and Retarding Admixtures

The purpose of these admixtures are to offset unwanted effects of high temperature, such as

acceleration of set and reduction of 28-day compressive strength, and to keep concrete

workable during the entire placing and consolidation period.

The benefits derived from retarding formulations include the following:

1. Permits greater flexibility in extending the time of set and the prevention of cold joints;

2. Facilitates finishing in hot weather; and

3. Permits full form deflection before initial set of concrete

Type E- Water-Reducing and Accelerating admixtures

Accelerating admixtures are added to concrete to shorten the setting time and accelerate the

early strength development of concrete. Some of the widely used and effective chemicals

accelerate the rate of hardening of concrete mixtures. The list includes; calcium chloride,

other chlorides, triethanolamine, silicates, fluorides, alkali hydroxide, nitrites, nitrates,

formates, bromides, and thiocyanates. The earlier setting time and increased early strength

gain of concrete brought about by an accelerating admixture will result in a number of

benefits, including reduced bleeding, earlier finishing, improved protection against early

exposure to freezing and thawing, earlier use of structure, and reduction of protection time to

15

achieve a given quality. Accelerators do not act as anti-freeze agents; therefore, protection of

the concrete at early ages is required when freezing temperatures are expected.

Type F- Water-Reducing, high range Admixtures

Super plasticizers, also known as plasticizers or high-range water reducers, reduce water

content by 12 to 30 percent and can be added to concrete with a low-to-normal slump and

water-cement ratio to make high-slump flowing concrete. Flowing concrete is a highly fluid

but workable concrete that can be placed with little or no vibration or compaction. The effect

of super plasticizers lasts only 30 to 60 minutes, depending on the brand and dosage rate, and

is followed by a rapid loss in workability. Because of the slump loss, super plasticizers are

usually added to concrete at the jobsite.

The primary difference between these admixtures and conventional water-reducing

admixtures is that high-range water-reducing (HRWR) admixtures, can reduce the water

requirement, without the side effect of excessive retardation. By varying the dosage rate and

the amount of mixing water, an HRWR admixture can be used to produce:

1. Concrete of normal workability at a lower w/c ratio;

2. Highly flowable, nearly self-leveling concrete at the same or lower w/c as concrete of

normal workability; and

3. A combination of the two; that is, concrete of moderately increased workability with a

reduction in the w/cm.

When used for the purpose of producing flowing concrete, HRWR admixtures facilitate

concrete placement and consolidation.

Type G - Water-Reducing, High range, and Retarding Admixtures

When the super plasticizers are also retarding, they are called type G admixtures. The

admixture manufacturer should be able to provide information covering typical dosage rates,

times of setting, and strength gain for local materials and conditions. But it was found out that

the rate of application of a particular chemical admixture used has no pronounced effect on

the strength of concrete [21].

16

3.2 The Use of Recycled Materials in Concrete Construction

3.2.1 General

Waste materials are common problems in modern living. Waste accumulates from a number

of sources including domestic, industrial, commercial and construction. These waste

materials have to be eventually disposed of in ways that do not endanger human health. In

light of this, waste minimization is increasingly seen as an ecologically sustainable strategy

for alleviating the need for the disposal of waste materials, which is often costly, time and

space consuming, and can also have significant detrimental impacts on the natural

environment. Nowadays governments and organizations have been concerned with

developing policies and programs to bring about successful outcomes to waste minimization.

This is seen as being essential to reduce the total amount of waste materials going into

landfill, especially in the urban areas where land is very scarce. The use of recycled materials

is often cheaper for the consumers of the end product. Hence, there is also an economic

justification for promoting its use.

Construction is the largest consumer of natural resources. In addition to being a major

consumer of natural resources, the construction industry is also one of the largest generators

of waste. Due to the increasing concern of the limited amount of remaining landfill space for

disposal, some countries like the UK prompted to introduce the Landfill Tax and a waste

strategy in an attempt to secure behavioral changes and meet new waste targets. This tax,

together with the aggregates levy has largely encouraged the use of alternative materials in

construction. The aggregate levy in the UK is around £1.60 per tone and its main objectives

are to reduce the demand for primary aggregates and encourage the use of alternatives [22].

When considering a waste material as a concrete aggregate, three major areas are relevant.

The economy, compatibility with other materials, and the concrete properties. The

economical use of waste material depends on the quantity available, the amount of

transportation required, the extent of the benefits, and the mix design requirements [14].

The use of recycled materials generated from transportation, industrial, municipal and mining

processes in transportation facilities is an issue of great importance. Recycled concrete

aggregates and slag aggregates are being used where appropriate. As the useable sources for

natural aggregates for concrete are depleted, utilization of these products will increase.

Utilization of fly ash and ground granulated blast furnace slag (ggbs) in concrete addresses

17

this issue in addition to improving concrete properties. The replacement of Portland cement

by fly ash or ggbs reduces the volume of cement utilized which is a major benefit since

cement manufacturing is a significant source of carbon dioxide emissions worldwide. Silica

fume is a comparatively expensive product and it is added in smaller quantities in concrete

mixture rather than as a cement replacement [15].

It was also emphasized that the possibility of using solid wastes as aggregates in concrete

serves as one promising solution to the escalating solid waste problem. The use of concrete

for the disposal of solid wastes has concentrated mostly on aggregates, since they provide the

only real potential for using large quantities of waste materials [14]. The effect of waste

materials on concrete properties must be considered. For example, the lower modulus of

elasticity of glass compared to that of good quality rock will lower the elastic modulus of

concrete. Crushed recycled concrete has been used as an aggregate, producing concrete with

strength and stiffness equal to about two-thirds of that obtained using natural aggregates.

These effects will be much more pronounced if low strength, low modulus materials such as

rubber and plastics are used. Scrapped tires have been proposed for use in concretes where

high resiliency rather than strength are required [14].

All of these applications greatly emphasize the different attempts of using recycled materials

in concrete and their respective advantages achieved so far. One of today’s major problems

and which will continue to do so for the foreseeable future is the environmental pollution

resulting from industrial wastes and waste living materials. Particularly among the waste

materials in the advancement of civilization are discarded waste tires. The main reason for

this is that the amount of waste tires is increasing at an alarming rate due to the large number

of cars and trucks.

3.2.2 Recycling of Waste Tires

3.2.2.1 Composition of a Tire

A tire is an assembly of numerous components that are built up on a drum and then cured in a

press under heat and pressure. Heat facilitates a polymerization reaction that crosslinks

rubber monomers to create long elastic molecules. These polymers create the elastic quality

that permits the tire to be compressed in the area where the tire contacts the road surface and

spring back to its original shape under high-frequency cycles [23].

18

The fundamental materials of modern tires are rubber and fabric along with other compound

chemicals. Their constructive make-up consists of the tread and the body. The tread provides

traction while the body ensures support. Before rubber was invented, the first versions of tires

were simply bands of metal that fit around wooden wheels in order to prevent wear and tear.

The most recent and popular type of tire is pneumatic, pertaining to a fitted rubber based ring

that is used as an inflatable cushion and generally filled with compressed air. Pneumatic tires

are used on many types of vehicles [24]. Table 3.2 below shows the typical composition of a

passenger tire and track tire respectively by listing the major classes of materials used to

manufacture tires with the percentage of the total weight of the finished tire that each material

class represents. From the percentage values of the composition, it can be observed that the

main difference between the passenger car and truck car is in the composition of natural

rubber and synthetic rubber. Otherwise, the other constituent materials are added in the same

quantity for both types.

Table 3.2 Percentage Composition of Materials for a Passenger and a Truck car [24].

Material passenger car Truck car

Natural rubber 14 % 27 %

Synthetic rubber 27 % 14 %

Carbon black 28 % 28 %

Steel 14-15 % 14-15 %

Fabric, fillers, accelerators,

antiozonants, etc.

16-17 % 16-17 %

3.2.2.2 The Need for Recycling of Waste Tires

Properly handled, scrap tires do not present any major environmental problems. If improperly

handled however, scrap tires can be a major threat to the environment. Tires exposed to the

elements can hold water and be a breeding space for mosquitoes that carry disease. Tire piles

can be set on fire through arson or accident. These fires are difficult to put out, and produce

heavy smoke and toxic run off to waterways. Tire piles can also harbor other vermin, such as

rats and snakes [13].

19

In the past waste tires were greatly used as a fuel source and they have been one of the major

markets for scrap tires. However, landfills became the most popular low-cost option for

disposal of tires after using them as a fuel source was prohibited in many countries due to

their high amount of environmental pollution. The scrap tire recovery rate declined,

promoting new legislation that supported research into methods for increasing tire recovery,

reuse, and recycling. As states reduce tire stockpiles and subsequently shift the focus of their

legislation concerning scrap tire management, scrap tire markets will likely be strengthened

and encouraged [25].

Different countries have a variety of strategies and methods regarding scrap tire management.

The US Environmental Protection Agency estimated that approximately 270 million scrap

tires per annum are discarded in the US, adding to stockpiles totaling 2-3 billion tires around

the country [22]. The disposal of waste tires represents a major issue in the solid waste

dilemma because there are more than 242,000,000 scrap tires, approximately one tire per

person and equivalent to 3 million tons, generated each year in the United States alone

[12,26]. It was stated that, in the U.S.A, State legislation regarding scrap tires was initiated in

the 1990’s to combat problems related to the disposal of tires in landfills and piles. Currently,

scrap tire management is governed by state legislation in all but two states in the United

States. Many states are actively working to clean up tire piles, 38 states ban whole tires from

landfills, and 11 states ban all scrap tires from landfills. More recent amendments to original

scrap tire legislation represent a shift in the focus of tire legislation toward reducing the

obstacles of developing scrap tire markets. The details of these amendments vary from state

to state. For example, Oregon passed legislation to create a Waste Tire Program. The

legislation did not ban tires from landfills, but created a $1 fee on each new tire sold at retail

price. The revenue from this fee was allocated to scrap tire-recycling programs. The

legislation and the programs were successful for several years and recovery rates for scrap

tires reached 98% [25].

Management of waste tires is also a big concern in the European countries. The EU Directive

on End of Life Vehicles also specifies targets for increasing reuse and recovery within this

waste stream. There are several established markets which will have to absorb those tires that

would have gone to landfill before the new legislation was introduced. If arisings of used tires

do not fall then these markets should either have to expand their consumption or new markets

should be developed for them [22]. Landfill disposal of scrap tires is becoming increasingly

20

difficult and the EU Directive on the landfill of waste (1999/31/EC – The Landfill Directive)

enforced that: The disposal of whole tires to landfill was banned since July 2003 and the

disposal of shredded tires to was banned starting from July 2006. This ban does not include

where tires are used in engineering applications for the development of a landfill site [27]. In

the UK, Concentrating on solutions for post-consumer tires was considered vital because of

the immediate challenge of the landfill directive which banned the disposal of whole tires to

landfill and also prohibited shredded tires later. It is estimated that 4Mt of waste tire is

generated each year in the UK and only 200,000t is currently recycled [22]. Currently only

about 4.5% of tires are recycled in civil engineering applications. These tend to be small-

scale applications in single projects. However, the potential market in civil engineering

applications is enormous because about £1.8bn is spent annually in the UK on concrete

products.

In 2008, Singaporeans discarded about 6 million tons of waste tire, of which 56% was

recycled, most of it from the commercial and industrial sectors. Considering the limited land

area of Singapore (approximately 680 km2), it is part of its strategy to abolish landfill sites

altogether and reduce the need for additional incineration plants, so as to increase the current

56% recycling rate to 60% by 2012. It is also reported that New Zealand produces around 3

million waste tires per year, with estimates varying from 2.2 to 4 million waste tires per year

and the country is currently looking for different alternatives for recycling waste tires with a

more emphasis given to engineering applications. Currently, New Zealand does have some

waste tire processors that shred tires either to render them acceptable for land filling or to

provide tire chips for such purposes as playground surface cover, drainage material, horse

arena surfaces, embankment construction and land erosion control [27].

Coming to the Ethiopian experience, like in most developing countries tire recycling in our

country is practiced informally. Tire recyclers are part of the informal sector manufacturers

that also includes artisans, weavers, service providers etc. The sector provides goods that are

substitute to conventional products produced in industries, which are beyond reach to most

customers. Moreover, it provides employment and income to many. The culture of recycling

seems to have taken naturally from collection to the final stage of producing recyclable

materials. It is a common practice to separate solid waste at household level for sale, which

for most low-income groups is a source of income.

21

According to the tire recyclers, tire-recycling dates to the time cars emerged in Ethiopia. It is

said to have started in Asmara in 1928. During the Italian invasion an Italian individual,

whose name is difficult to trace today, introduced the technique of using waste tires for

recycling. And then two individuals brought the technique to the capital city in 1962. It has

taken almost 34 years for the practice to reach Addis Ababa from Asmara. An elderly tire

recycler recalls that there were only two types of shoes produced from old tire: bale'kertas

kene'matcha and sandals. The bale'kertas kene'matcha is a special type of shoe made to resist

hard surface in the countryside [28]. A sandal is a type of shoe with a buckle. It is strong,

durable, and expensive. Then an Italian introduced a cheaper kind giving the name berebaso.

The berebaso sandals were worn during the Italian invasion. Even today, it is still a popular

shoe in some rural areas. It is given different names in different parts of the country (chefere,

legibe, anekew, shebet etc.) [28].

Today, the way these sandals are made is changed. It is made in a simple way with traditional

tools. A place with a name of "Goma Tera" in Addis is where old, large and small tires are

recycled. They pay between 30 and 60 birr for old tires. Old tires are obtained from car

owners selling their old tires, tire-repairing garages (Gomistas), auction at Matador Addis

Tire Factory, governmental and nongovernmental organizations. Out of these old tires, they

make shoe soles, heels and straps, sandals, doormats, stool and chair seats, conveyor belts,

ceiling divider etc. The wires are used for fencing, making egg holders (containers). The

strings out of the tire are used for musical instruments, thread (jeemat) coming out from the

tire is used for sewing shoes, bags, etc. The leftover bits and pieces from recycled tires are

bought by road constructors and used as fuel to melt the tar (asphalt). Thus in the past times,

each part of old tires are either recycled or recovered. But according to the recyclers the need

for these products are decreasing nowadays mainly due to modernization and the change in

the living condition of the urban people.

The Ethiopian tire and rubber economy plant plc is the pioneer company in Ethiopia in

reprocessing of tires. The company has stayed in the business for more than 45 years. The

company produces tiles, neolin sheets, car mats, foot mats, microcellular sheets, sandal,

billiard rubber etc from rubber and tire [29].

Recently, the Ethiopian government made a proclamation regarding used tires on the

‘Federal negarit gazette no.13 February 2007’ under solid waste management proclamation

No. 513/2007 article 9. And it states that [30]:

22

i) The importation of used tires into Ethiopian territory for the purpose of disposal is

prohibited.

ii) The importation of used tires for environmentally acceptable use shall be

determined by directives issued by the authority.

The modern approach to assessing the total environmental resource cost of a product or

industry is to calculate the mass balance of natural resources consumed and wastes produced

over the lifetime of the product or process under scrutiny [18]. A great resource use is

associated with tire use, particularly the fuel used to overcome the rolling resistance of tires.

As a result the greatest outputs are emissions (CO2 and H2O) resulting from fuel combustion.

Hence, the recycling of waste tires and using them in a more usable form is mandatory at the

current time. Post-consumer tires possess properties that make them very suitable for use as

an alternative to primary and secondary aggregates in a number of different applications.

Post-consumer, or used tires are those that have come to the end of their useful life in terms

of their intended use. Materials that come to the end of their normal working life will become

waste, and require some form of treatment or disposal.

3.2.2.3 Methods of Recycling Tires

The numerous techniques and technologies available for processing postconsumer tires are

enumerated below [3].

1. Shredding and Chipping: This is mechanical shredding of the tires first in to bigger sizes

and then into particles of 20 – 30 mm in size.

2. Crumbing: It is the processing of the tire into fine granular or powdered particles using

mechanical or cryogenic processes. The steel and fabric component of the tires are also

removed during this process.

3. DeVulcanising: This is the treatment of tire with heat and chemicals to reverse the

vulcanisation process in the original tire production.

4. Pyrolysis and Gasification: These are two thermal decomposition processes carried out

under different conditions. The processes produce gas, oil, steel, and carbon black (char).

5. Energy Recovery: It is the incineration of tires to generate energy.

3.2.2.4 Benefits of Recycled Tires

A wide range of potential sectors which can benefit from using rubber from waste tires are

identified. The areas were grouped into five classes [3].

23

a) Civil engineering, non-road

b) Civil engineering, road and infrastructure

c) Sport, safety and outdoor surfaces

d) Consumer and industrial products, and

e) Energy

The proposed benefits of using waste tires in construction are three-fold:

a) They can offer distinct engineering benefits over traditional aggregates.

b) They can be used as an alternative to primary materials thereby reducing an environmental

burden on extraction.

c) Their use can help to reduce burden of waste disposal (including illegal stockpiling and

disposal, such as fly-tipping, with their associated risks) and the impacts on the

environment associated with some other uses of tires [22].

Waste tires have hardness and elasticity properties superior to those of rubber, good

resistance to weathering, can be used for preventing impact damage, and as a pavement

making material, because of their low specific gravity which is lower than most construction

materials [31]. Crumb rubber from shredded tires has been successfully added to asphalt and

is widely used. For example, it was used as a wearing course in Arizona and in two Colorado

pilot projects. However, the addition of rubber to concrete is a newer technology [10].

The following section discusses the application of recycled tires in concrete.

3.3 Material constituents of Rubberized Concrete

3.3.1 General The production of concrete using waste tire rubber added in different volume proportions is a

very infant technology. Partially replacing the coarse or fine aggregate of concrete with some

quantity of small waste tire cubes can improve qualities such as low unit weight, high

resistance to abrasion, absorbing the shocks and vibrations, high ductility and so on to the

concrete. Moreover, the inclusion of rubber into concrete results in higher resilience,

durability and elasticity. In constructions that are subject to impact effects the use of

rubberized concrete will be beneficial due to the altered state of its properties [2].

3.3.2 Rubber Aggregate

Rubber aggregates are obtained by reduction of scrap tires to aggregate sizes using two

general processing technologies: mechanical grinding or cryogenic grinding. Mechanical

24

grinding is the most common process. This method consists of using a variety of grinding

techniques such as ‘cracker mills’ and ‘granulators’ to mechanically break down the rubber

shred into small particle sizes ranging from several centimeters to fractions of a centimeter.

The steel bead and wire mesh in the tires is magnetically separated from the crumb during the

various stages of granulation, and sieve shakers separate the fiber in the tire [13].

Cryogenic processing is performed at a temperature below the glass transition temperature.

This is usually accomplished by freezing of scrap tire rubber using liquid nitrogen. The

cooled rubber is extremely brittle and is fed directly into a cooled closed loop hammer-mill to

be crushed into small particles with the fiber and steel removed in the same way as in

mechanical grinding. The whole process takes place in the absence of oxygen, so surface

oxidation is not a consideration. Because of the low temperature used in the process, the

crumb rubber derived from the process is not altered from the original material [13].

At the early stages of research related to the use of recycled tires, chips were available and

most of the time the particles contained steel wires and polyester fibers. With the advances in

technology, now the recyclers are capable of removing all the wires and polyester fibers. In

addition, the tire chips that were used at the early stages are disappearing and being replaced

by crumbed rubber which has small or no residue of fibers and wires [32]. This tire crumb, a

high specification product available in a range of grading from 0.5 mm to 30 mm, has been

used by manufacturers and installers in the construction industry for around twenty-five years

and the annual consumption continues to increase year on year [33].

Shredded tires can be used as filler material for soils, foundations and pavements. Crumbed

or pulverized tire rubber can be combined with other polymeric material to form mats,

playground tiles, or road barriers among others. By itself, it can be used as an aggregate for

asphalt pavements or concrete mixes. Similar to the recycling of polymers, a solution is to

substitute part of the aggregate in concrete mixes with pulverized tire rubber or shredded tires

[32]. The idea of using tires as aggregates initially emerged from the reason that they have

physical properties that can be substituted for existing materials, or because their properties

provide an advantage over existing materials. These include; Durability, low unit weight,

high hydraulic conductivity, low horizontal stress, flexibility for construction and thermal

resistivity [27].

Concrete can be made by replacing some of its fine or coarse aggregate with granulated

rubber crumbs from used rubber tires. These granulated rubber crumbs are achieved through

25

a process of cutting the tire rubber to create crumbs small enough to replace an aggregate as

fine as sand or as coarse as gravel. Such kind of concrete is used in the manufacture of

reinforced pavements and bridge structures and have a better resistance to frost and ice

thawing [27].

In an experiment by Kumaran S.G. et al, two rubberized concrete mixes were developed

using fine rubber granules in one mix and coarse rubber granules in the second. While these

two mixes were not optimized and their design parameters were selected arbitrarily, their

results indicated a reduction in compressive strength of about 50 % with respect to the control

mixture. The elastic modulus of the mix containing coarse rubber granules was reduced to

about 72 % of that of the control mixture. Whereas, the mix containing the fine rubber

granular showed a reduction in the elastic modulus to about 47 % of that of the control

mixture. The reduction in elastic modulus indicates higher flexibility, which may be viewed

as a positive gain in rubberized concrete mixtures used as stabilized base layers in flexible

pavements [2]. The starting point for this experiment was the works of other researchers who

used crumbed waste tire fibers (average length 12.5 mm) and short polypropylene fibers

(length from 12-10 mm) to modify concrete [2]. The research was conducted using the grade

of cement 53, to improve the strength and fine sand plus coarse aggregate of a combination of

10 mm and 20 mm. The waste tire rubber was used in the form of chips and fibers by

partially replacing the coarse aggregate with 0, 5, 10, 20 and 25 % values. Figure 3.1 below

shows the waste tires chips used in the above mentioned experiment as a partial replacement

of coarse aggregate in the concrete. The size of the waste tire chips were 25, 50 and 75 mm

by 7 mm with an anchorage hole of different diameters.

Fig. 3.1 Samples of Coarse granules of Waste Tire [2]

26

Ling T.C. and Hasanan M.N. conducted a research using crumb rubber produced by

mechanical shredding as a fine material with the gradation close to that of natural sand. In

this study, two particle sizes of crumb rubber were used: 1-3 mm and 3-5 mm as a partial

substitute for sand in the production of concrete paving block [34]. Figure 3.2 below shows

the mechanically shredded fine tires.

Fig. 3.2 Mechanically Shredded Fine Tires [34]

A research by Yunping Xi et al used two types of rubber particles of different sizes (large and

small to study the size effect on mechanical properties of rubberized concrete. The average

size of large particles was 4.12 mm, and the average size of small particles was 1.85 mm. The

test results indicated that the particle size used in this study has no significant effect on

compressive strength, brittleness and toughness of the concrete produced [35]. Figure 3.3

below shows rubber cuts of 4.12 mm.

Fig. 3.3 Tire Rubber Cuts of 4.12 mm [35]

In a quite different manner, a study by Prakash P. et al has used crumb rubber to replace

cement. The focus of the experimental program was to investigate the performance of

Cement Stabilized Soil Blocks with treated crumb rubber as a partial replacement of cement

27

to produce cement stabilized soil blocks. By using cement as a binder and conventional soil

cement stabilized blocks production process, the treated crumb rubber cement stabilized soil

blocks were more durable and absorbed higher energy under impact [7].

Mixtures can be made using ground tire in partial replacement by volume of coarse aggregate

and fine aggregate. Based on the workability, an upper level of 50 % of the total aggregate

volume may be used. Strength data developed in an investigation (compressive and flexural)

indicates a systematic reduction in the strength with the increase of rubber content. From a

practical viewpoint, rubber content should not exceed 20 % of the aggregate volume due to

severe reduction in strength. Once the aggregate matrix contains nontraditional components

such as polymer additives, fibers, iron slag, and other waste materials, special provisions

would be required to design and produce these modified mixes [2].

Most investigators replaced either the fine or coarse aggregates in the concrete mixes

partially or wholly by volume of rubber aggregate. Ling T. C. et al used natural aggregates

which include natural river sand as the fine aggregate and crushed granite with nominal size

less than 10 mm as the coarse aggregate and finally replaced part of the fine aggregate with a

rubber aggregate [34]. Gintautas S. et al also used crumb rubber as fine aggregate

replacement [6]. And Kaloush K.E. et al also used crumb rubber particles sizes of about 1

mm [4]. Whereas Michelle Danko et al used recycled tires as a partial replacement of coarse

aggregate to produce rubberized concrete [26].

Preparing waste tire powders and thin tire fibers is time, effort and money consuming.

Sometimes the cost may be so high that it cannot be justified by its gain in performance.

Because larger sized chips or fibers are very easy to produce, it is expected that the cost of

larger sized chips or fiber-modified concrete will be very low. Indeed, waste tire chips and

fiber is uniquely different to other waste materials, because its production method does not

require any sophisticated machineries and it is easy to handle it economically. Much debate is

still rising on whether recycled rubber is better used as a fine aggregate or as a coarse

aggregate. However, whatever the case it may be, one thing is clear so far i.e. the introduction

of recycled rubber aggregate changes the properties of concrete [26].

28

3.3.2.1 Surface Treatment of Rubber Aggregates

Studies have suggested that the rougher the rubber aggregate used in concrete mixtures the

better the bonding developed between the particles and the surrounding matrix, and therefore

the higher the compressive strength achieved. If the bond between rubber aggregate and the

surrounding cement paste is improved, then significantly higher compressive strength of

rubberized concrete could be obtained and to achieve enhanced adhesion, it is necessary to

pre-treat the rubber aggregate [13].

Pre-treatments vary from washing rubber aggregate with water to acid etching, plasma pre-

treatment and various coupling agents. The acid pretreatment involves soaking the rubber

aggregate in an acid solution for 5 minutes and then rinsing it in water. It was reported that

when observed through a microscope, the pre-treatment of rubber aggregate with acid

increased the surface roughness of rubber, which had improved its attachment to the cement

paste [13]. According to Neville A.M., it is generally found that as the paste aggregate bond

increases so does the strength [1]. In rubberized concrete, the strength loss of the concrete is

minimized, and the toughness of the concrete is enhanced by surface treatment of the rubber

particles using coupling agents.

Yunping Xi et al suggested that an 8 % silica fume pretreatment on the surface of rubber

particles could improve properties of rubberized mortars. On the other hand, directly using

silica fume to replace equal amount (weight) of cement in concrete mix has the same effect.

Saturated NaOH solution can also be used to treat waste tire rubber powders. It was found

that NaOH surface treatment increased rubber/cement paste interfacial bonding strength and

resulted in an improvement in strength and toughness in waste tire powder modified cement

mortar [35]. Michelle Danko et al applied pre-treating of the rubber with a sodium hydroxide

solution to modify its surface, affecting the interfacial transition zone and allowing the rubber

to better adhere with the cement paste. The use of treated tire rubber as addition to cement

paste shows satisfactory results in concrete mechanical properties such as impact resistance

and ductility [26].

Carbon tetrachloride was also utilized for pretreatment of rubber aggregates. It was attempted

to clean the rubber using water and carbon tetrachloride (CCL4) solvent and water and a latex

admixture cleaner. Results show that concrete containing washed rubber aggregate achieved

about 16% higher compressive strength than concrete containing untreated rubber aggregates.

29

A much larger improvement in compressive strength (about 57%) was obtained when rubber

aggregates treated with CCL4 were used [13].

The other method employed two coating system: coating with cement paste and coating with

Methocel cellulose ether solution, a water-soluble polymer derived from cellulose. However,

it was found that, although coating the rubber aggregate with cement paste can increase the

compressive strength of the mixture by 30%, little improvement in flexural strength was

observed compared with rubberized concrete containing plain rubber aggregate. Little

improvement was observed when using rubber aggregate coated with Methocel. The use of

Methocel reduced the compaction of the fresh concrete due to the high viscosity of the

rubberized solution. This coating might also hinder the further hydration of the cement during

curing and thus can further affect the compressive strength of the concrete. Later on, a single

coating with cement paste only was experimented by Cairns R. et al. They had used coating

with a rich mix of cement paste and allowed it to sufficiently dry by exposing it to air. The

results showed that rubber aggregate coated with cement paste has improved properties [13].

The overall results show that using proper coupling agents to treat the surface of rubber

particles is a promising technique, which produces a high performance material suitable for

many engineering applications.

3.3.3 Natural Aggregates in Rubberized Concrete

Rubberized concrete is produced by partially replacing the mineral aggregates with rubber.

Therefore, the mineral aggregates are still part of the constituents as in the conventional

concrete. Natural aggregates are usually obtained by mining or from natural sources like river

in the case of sand. The coarse and fine aggregates are usually mined separately.

Occasionally, aggregate is obtained as a by-product of some other processes (e.g., slag or

recycled concrete). Aggregates may be crushed and may be washed [19]. They are usually

separated into various size fractions and reconstituted to satisfy the grading requirements.

They may need to be dried. A modest amount of energy is involved in all these processes.

There is no specialty in the type of mineral aggregates used in rubberized concrete. The

discussion in section 3.1.2.2.1 of this literature review is also applicable here.

30

3.3.4 Cement in Rubberized Concrete

The choice of cement for a particular application depends on the availability, the cost and on

the particular circumstances of equipment, skilled labor force, speeds of construction and of

course on the exigencies of the structure and its environment [1]. Wide varieties of cements

were used to produce rubberized concrete by different researchers.

Ling T.C. and Hasanan M.N. used ordinary Portland cement in their research [34]. Ordinary

Portland cement is suitable for many applications and it can also be used conveniently in

rubberized concrete. On the other hand, Kumaran S.G et al used recycled tire rubber in

concrete mixes made with magnesium oxychloride cement, where the aggregate was replaced

by fine crumb rubber up to 25% by volume. The results of compressive and tensile strength

tests indicated that there is better bonding when magnesium oxychloride cement is used. The

researchers discovered that structural applications could be possible if the rubber content is

limited to 17% by volume of the aggregate [2].

Cairns R. et al reported that the type of cement used in rubberized concrete mixtures greatly

affects the mechanical strength. Recycled tire rubber aggregates were used in concrete

mixtures made with both Magnesium Oxychloride Cement (MOC) and Ordinary Portland

Cement (OPC). The percentage substitution of fine aggregate ranged from zero to 90 %,

increasing by 15% for each set. It was observed that 90% loss of the compressive strength

occurred for both the OPC rubberized concrete and MOC rubberized concrete when rubber

was replaced by 90% of the fine aggregate (25% of the total aggregate). Whether with or

without rubber aggregate inclusion, the MOC concrete exhibited approximately 2.5 times the

compressive strength of the OPC concrete. The OPC concrete samples containing 25% of

rubber by total aggregate volume retained 20% of their splitting tensile strength after initial

failure, whereas the MOC concrete samples with similar rubber content retained 34% of their

splitting tensile strength after initial failure. The ratio of the MOC rubberized concrete tensile

strength to OPC rubberized concrete tensile strength rose from 1.6 to 2.8 with increased

amounts of rubber. They argued that the high-strength and bonding characteristics provided

by Magnesium Oxychloride cement greatly improved the performance of rubberized

concrete mixtures and that structural applications could be possible if the rubber content is

limited to 17% by total volume of the aggregate [13].

All the above studies show that a careful attention needs to be given to the type of cement to

be used in rubberized concrete before starting the concrete mix preparation.

31

3.3.5 Admixtures in rubberized concrete

The development of chemical admixtures has revolutionized concrete technology in the last

fifty years. The use of air entraining admixtures, accelerators, retarders, water reducers and

corrosion inhibitors are commonly used for bridges and pavements. To improve the strength

characteristics and other mechanical properties of rubberized concrete, some admixtures

(chemical or mineral) can be added as a partial replacement of cement to get more

workability and strength enhancement of rubberized concrete [2].

3.3.6 Water in rubberized concrete

No special considerations are necessary for the use of water in the production of rubberized

concrete. The discussion in section 3.1.2.3 of this literature review is also applicable for this

part.

3.4 Properties of Fresh Rubberized Concrete 3.4.1 Aesthetics

Cairns R. et al found that rubberized concrete showed good aesthetic qualities. The

appearance of the finished surface was similar to that of ordinary concrete and surface

finishing was not problematic. However, the authors reported that mixes containing a high

percentage of larger sized rubber aggregate required more work to smooth the finished

surface. They also found that the color of rubberized concrete did not differ noticeably from

that of ordinary concrete. However, occasionally spots of rubber came to the surface, and

need to push the pieces back down when working the finish [13].

3.4.2 Workability

A decrease in slump was observed with increase in rubber aggregate content. For rubber

aggregate contents of 40% by total aggregate volume, the slump was close to zero and the

concrete was not workable by hand. Such mixtures had to be compacted using a mechanical

vibrator. Mixtures containing fine crumb rubber were, however, more workable than mixtures

containing either coarse rubber aggregate or a combination of crumb rubber and tire chips

[13]. It was found that increasing the size or percentage of rubber aggregate decreased the

workability of the mix and subsequently caused a reduction in the slump values obtained.

From the same study, it was noted that the size of the rubber aggregate and its shape

(mechanical grinding produces long angular particles) affected the measured slump [13].

32

Rubber filled concrete tends to have a reduction in slump and density compared to ordinary

Portland cement concrete. Reduction of around 85% on slump has been reported when

comparing traditional aggregate concrete with mixes containing recycled rubber. Other

researchers found out that roughly textured, angular, and elongated particles require more

water to produce workable concrete than smooth, rounded compact aggregate [26,36].

The slump values of mixes containing long, angular rubber aggregate were lower than those

for mixes containing round rubber aggregate (cryogenic grindings). Round rubber aggregate

has a lower surface/volume ratio. Therefore, less mortar will be needed to coat the

aggregates, leaving more to provide workability. The angular rubber aggregates form an

interlocking structure resisting the normal flow of concrete under its own weight; hence,

these mixes show less fluidity. It is also possible that the presence of the steel wires

protruding from the tire chips also contributed to the reduction in the workability of the

concrete mix [13].

3.4.3 Air content

There is a higher air content in concrete mixtures containing rubber when compared to

control mixtures. Even without any air-entrainment admixtures being introduced, it has been

reported that the air content is significant. The higher air content of rubberized concrete

mixtures may be due to the non-polar nature of rubber aggregates and their ability to entrap

air in their jagged surface texture. When non-polar rubber aggregate is added to the concrete

mixture, it may attract air as it repels water [26]. This increase in air voids content would

certainly produce a reduction in concrete strength, as does the presence of air voids in plain

concrete [1]. Since rubber has a specific gravity greater than 1, it can be expected to sink

rather than float in the fresh concrete mix. However, if air is trapped in the jagged surface of

the rubber aggregates, it could cause them to float. Cairns R. et al have observed this

segregation of rubber aggregate particles in practice [13].

3.5 Properties of Hardened Rubberized Concrete

3.5.1 Unit Weight

The replacement of natural aggregates with rubber aggregates tends to reduce the density of

the concrete. This reduction is attributable to the lower unit weight of rubber aggregate

compared to ordinary aggregate. The unit weight of rubberized concrete mixtures decreases

as the percentage of rubber aggregate increases [26]. The unit weight (density) of concrete

33

varies, depending on the amount and density of the aggregate, the amount of air that is

entrapped or purposely entrained, and the water and cement contents, which in turn are

influenced by the maximum size of the aggregate.

Because of low specific gravity of rubber particles, unit weight of mixtures containing rubber

decreases with the increases in the percentage of rubber content. Moreover, increase in rubber

content increases the air content, which in turn reduces the unit weight of the mixtures. At

30% rubber content, the dry density diminished to about 95 % of the normal concrete.

However, the decrease in dry density of rubber is negligible when rubber content is lower

than 10-20 % of the total aggregate volume [34]. The reduction in the unit weight of the

rubberized concrete mix increases as the percentage crumb rubber added increases [2, 4].

3.5.2 Compressive Strength

Compressive strength tests are widely accepted as the most convenient means of quality

control of the concrete produced. Tests conducted by Kumaran S.G. et al on rubberized

concrete behavior, using tire chips and crumb rubber as aggregate substitute of sizes 38, 25

and 19 mm exhibited reduction in compressive strength by 85% and tensile splitting strength

by 50% but showed the ability to absorb a large amount of plastic energy under tensile and

compressive loads [2].

Kaloush K.E. et al also noted that the compressive strength decreased as the rubber content

increased. Part of the strength reduction was contributed by the entrapped air, which

increases as the rubber content increases. Investigative efforts showed that the strength

reduction could be substantially reduced by adding a de-airing agent into the mixing truck

just prior to the placement of the concrete [4].

In another study by Ling T.C. and Hasanan M.N, test results have shown that there was a

systematic reduction in the compressive strength with the increase in rubber content from 0 %

to 30 % [34]. According to Felipe J.A. and Jeannette Santos, a maximum strength reduction

of 50% was noted for a mix with 14% substitution in their studies [32]. Nevertheless, in a

very different approach, Hanson aggregates achieved higher compressive strength in crumb

rubber concrete by reducing entrapped air in the mix [10].

34

In most of the previous studies, a reduction in compressive strength was noted with the

addition of rubber aggregate in the concrete mix but there is still a possibility of greatly

improving the compressive strength by using de-airing agents [1].

3.5.3 Tensile Strength

The tensile strength of rubber containing concrete is affected by the size, shape, and surface

textures of the aggregate along with the volume being used indicating that the strength of

concretes decreases as the volume of rubber aggregate increases [26]. As the rubber content

increased, the tensile strength decreased, but the strain at failure also increased. Higher tensile

strain at failure is indicative of more energy absorbent mixes [4]. Tests conducted on

rubberized concrete behavior, using tire chips and crumb rubber as aggregate substitute of

sizes 38, 25 and 19 mm exhibited reduction in splitting tensile strength by 50% but showed

the ability to absorb a large amount of plastic energy under tensile loads [2].

3.5.4 Impact Strength and other mechanical properties

Previous investigations have shown that the addition of rubber aggregate into the concrete

mixture produces an improvement in toughness, plastic deformation, impact resistance and

cracking resistance of the concrete. For concrete, it is found that the higher the strength, the

lower the toughness. It is difficult to develop high strength and high toughness concrete

without modifications. Owing to the very high toughness of waste tires, it is expected that

adding crumb rubber into concrete mixture can increase the toughness of concrete

considerably. Laboratory tests have shown that the introduction of waste tire rubber

considerably increase toughness, impact resistance, and plastic deformation of concrete [34].

An analysis was carried out on rubberized concrete that used 15% replacement of waste tire

for an equal volume of mineral coarse aggregate. It was used as a two phase material as tire

fiber and chips dispersed in concrete mix. The result is that there is an increase in toughness,

plastic deformation, impact resistance and cracking resistance. However, the strength and

stiffness of the rubberized sample were reduced. The control concrete disintegrated when

peak load was reached while the rubberized concrete had considerable deformation without

disintegration due to the bridging caused by the tires. The stress concentration in the rubber

fiber modified concrete is smaller than that in the rubber chip modified concrete. This means

the rubber fiber modified concrete can bear a higher load than the rubber chip modified

concrete before the concrete matrix breaks [2].

35

Using rubber waste in concrete, less concrete module of elasticity is obtained. Modulus of

elasticity is related to concrete compressive strength and the elastic properties of aggregates

have substantial effect on the modulus of elasticity of concrete. The larger the amount of

rubber additives added to concrete, the lesser the modulus of elasticity [6]. It is hypothesized

that rubber crumbs may function as a distribution of mini expansion joints inside the

concrete. Thus, the crumb rubber concrete may exhibit good characteristics in controlling

crack initiation and propagation. To evaluate this hypothesis further, in January 2003, the first

of several test slabs was built. The slab contained crumb rubber consisting of 25% of the

concrete mix by volume and it was placed without any joints in the laboratory. No shrinkage

cracks have been observed. The intended use of the slab was to serve as a truck parking

facility. The results show that the crumb rubber concrete mix had more ductility and

comparable toughness values as to the control mix [4].

Results of tension test, fatigue test and ultrasound velocity test showed that the rubberized

concrete has higher energy dissipation capacities than regular concrete, that is, the resulting

concrete has high toughness and high ductility. The failure modes of the rubberized concrete

indicate that the rubber concrete samples can withhold very large deformation and still keep

their integrity [35]. It was also stated that Concrete containing rubber aggregate has a higher

energy absorbing capacity referred to as toughness. In all failure tests, the crumb rubber

concrete specimens stayed intact (did not shatter) indicating that the rubber particles may be

absorbing forces acting upon it [26]. Such behavior may be beneficial for a structure that

requires good impact resistance properties. The increase was more pronounced in concrete

samples containing larger-size rubber aggregates [4, 13].

Hence, from the studies so far, the use of rubberized concrete can be a very feasible and

realistic approach in applications where a higher toughness and impact strength is required.

3.5.5 Flexural Strength

Kaloush K.E. et al found that the flexural strengths of rubberized concrete decreased as the

rubber content in the mix increased [4]. On the contrary, Kang Jingfu et al reported that there

is an improvement in flexural strength by the addition of rubber aggregates in roller

compacted concrete. In comparison with the control concrete, when the compressive strength

was kept constant for roller compacted concrete, the flexural strength, and ultimate tension

elongation increased with the increase of rubber content [37].

36

3.6 Applications of Rubberized Concrete There is a growing evidence for the feasibility of substituting waste tire rubber with a portion

of natural aggregate in concrete production. While very little rubber from used tires goes into

the production of new tires, hosts of other products made from recycled tire rubber have

come to market in many areas of applications.

Chips of shredded tire rubber are used as a fill in engineering projects. More finely cut and

screened tire rubber is used in playground and landscaping areas. Crumb rubber is used to

make better asphalt, while rubber mixed with urethane is used to make athletic track surfaces

and a variety of molded products. The crumb rubber market has been one of the fastest-

growing scrap tire markets over the last few years [7].

Among the largest projects that utilized higher contents of crumb rubber in concrete was an

experimental outdoor tennis court in Phoenix. Leading to the final construction of this tennis

court, a series of experimental test slabs (0.61m x 1.22m in size, with a thickness of 5 to 8

cm) were built in January 2003 with rubber content varying between 20 to 130 kg of crumb

rubber per m3 of concrete. The experimental testing program included compressive strength,

flexural strength, indirect tensile strength, and thermal coefficient of expansion tests. The

preliminary results were very encouraging [4].

The introduction of waste tire rubber considerably increased toughness, impact resistance,

and plastic deformation of concrete, offering a great potential for it to be used in sound/crash

barriers, retaining structures and pavement structures. A study revealed that it is possible to

fabricate block containing rubber up to 30 % by sand volume using chemical and mineral

admixtures, which gives better bonding characteristics to rubber and significantly improves

the performance of crumb rubber concrete paving block [34]. New Zealand does have some

current waste tire processors that shred tires either to render them acceptable for land filling

or to provide tire chips for such purposes as playground surface cover, drainage material,

horse arena surfaces, embankment construction and land erosion control [27].

There are also uses of rubberized concrete in building applications. It has been shown that

crumb rubber additions in structural high strength concrete slabs improved its fire resistance,

reducing its spalling damage under fire. This material provides a good mechanical behavior

under static and dynamic actions and is being used for road pavement applications. The

results of recycled tire rubber-filled concrete (RRFC) under fatigue loads show the feasibility

37

of using this composite material as a rigid pavement for roads on elastic sub grade [9]. Barnet

J. et al suggested that landscaping applications like playground surface cover, athletic field

turf amendment, and running track construction is a potential market. Rubber strips can also

be partially embedded into concrete surfaces, such as in paving slabs, concrete floors,

highway crash barriers, bollards, etc. to soften tread or dampen any impact [11].

Applications in the areas of horse arenas and playgrounds and landscape materials show that

crumb rubber can bring some improved qualities to concrete. For it absorbs force and

bounces back, does not freeze, and is not biodegradable. Small proportions of rubber are also

used as an energy absorbing material in children’s play areas to prevent injury. In January

2003, Hanson's Aggregates built the first of several test slabs. The slab contained around 180

kg of crumb rubber per m3 (representing 25 percent of the concrete mix by volume) and was

placed without any joints. No shrinkage cracks have been observed after a period of more

than a year. This slab serves as a truck parking facility [10].

Currently, the waste tire rubberized concrete is used in precast sidewalk panel, non-load

bearing walls in buildings and precast roof for green buildings. It can be widely used for

development related projects such as roadways or road intersections, recreational courts and

pathways and skid resistant ramps. With this new property, it is projected that these concretes

can be used in architectural applications such as nailing concrete, where high strength is not

necessary, in wall panels that require low unit weight, in construction elements and Jersey

barriers that are subject to impact, in railroads to fix rails to the ground. Roofing tiles and

other concrete products can now be made lighter with Rubberized concrete [13]. Benefits

from using recycled rubber in landscaping projects include project cost savings, and

improved product performance and safety. Greenhouse gas and public health benefits result

from diverting tires from landfills and tire piles [25].

Looking at the possibilities for crumb rubber in future concrete products, one can visualize

high-rises that are lighter in weight and more resistant to cracking. Moreover, concrete bases

for heavy pounding machinery that absorb the sound and withstand the pressure can be

achieved. All the applications discussed above show that there is a huge potential advantage

that can be exploited from the use of rubberized concrete. It is a very promising technology

that can deliver various outstanding benefits to the construction sector.

38

3.7 Cost Considerations in Rubberized Concrete The use of recycled tires in concrete construction is an infant technology and the number of

used tires that are recycled in civil engineering applications is very low at the current time.

However, any new concrete products developed for the market need to be feasible in terms of

cost, including material costs and production processes or the resulting advantage of

improved properties should surpass any cost increment that may occur. The different factors

associated with the cost of rubberized concrete are discussed below.

3.7.1 Used Tire Recycling Costs

The costs incurred from postconsumer tire use are proportional to the degree of treatment,

processing and transportation required in producing and delivering the finished material to

the construction site. Tire recycling processes involve the reduction of used tires into smaller

pieces such as chip and crumb sizes for reuse or further processing. For most current uses of

recycled tires, the production processes attempt to add value to the basic material. This can be

achieved by, for example, reducing the size, or by separating out the various components

such as rubber, steel and fiber to produce a purer material. In addition, more value can be

added by treating the crumb rubber in some way to improve its characteristics. However, as

the amount of processing increases, the production costs and hence the price of the material

also increases. This strategy is beneficial for producers and customers where the added value

improves the profit margin for the producer and the cost of the new material is less than the

material it replaces. Therefore, the economics of using recycling rubber in concrete can be

expected to change, including the production costs, as the market potential of new products

develops. The important economic drivers in a free-market economy are competition and the

profit motive. As more recyclers enter the market, it can be expected that competition will

bring down the cost of the recycled materials [18].

3.7.2 Cost Savings due to Material substitution

The other approach is to consider the replacement value of virgin materials used in current

products. This calculates the acceptable price for rubber aggregate based upon the current

price of virgin materials less an allowance for the cost of process changes. In this approach,

the principle is that the use of rubber aggregate should be cost neutral. The acceptable price

for rubber aggregate can then be compared with the actual price [13]. The process change

costs are dependent on the particular application and are therefore difficult to estimate at

39

present. The cost of rubber aggregates also varies widely depending on the source of the

rubber and the amount of processing during production.

Taking the UK government as an example, its policy is to reduce demand for virgin materials

and encourage the use of recycled materials by promoting a market solution through a

mixture of statutory regulation and economic measures. The Landfill Tax was introduced in

October 1996 to discourage the land filling of inert and active waste and the value of the tax

is set to increase over time. The European Union legislation currently bans the disposal of

whole tires in landfill sites. The implementation of the landfill ban will undoubtedly improve

the viability and economics of tire recycling. It is possible that the tire retailers will need to

pay more to the tire recyclers to take the used tires and that this cost will be passed on to tire

purchasers [22].

Cost savings can be made by substituting aggregates for tires. Tires weigh less than most

other options. The cost of transporting the equivalent m3/km in tires will thus be less than for

other aggregates, however, the distance differential should also be considered carefully to

ensure that any additional distance required to deliver tires or tire materials does not negate

the advantage.

3.7.3 Cost Savings through Performance

One of the most powerful drives for engineers to adopt alternative recycled materials is if

they can be shown to offer significant technical advantages. The increasing use of industrial

by-products such as pulverized fuel ash since the 1950s either as lightweight fills, lightweight

aggregates for low-density concrete and for low bearing capacity ground fills, was entirely

driven by their low weight and durability advantages [22].

In general, the value added in production and processing will determine the viability of any

type of recycling. This is the case for basic rubber crumb and chip products as well as any

products incorporating these materials. The first stage is to determine the additional

production costs for potential rubberized concrete products, which can then be set against the

benefits of using these products. For example, using ground rubber in landscaping

applications resulted in significant cost savings from decreased project maintenance and from

the benefits related to improved product performance (e.g. safety and suitability) [25].

40

Therefore, rubberized concrete can offer significant technical advantages and associated cost

savings. Extended life expectancy and the increased durability of structures using rubber

aggregate should add cost effectiveness over the long term by offsetting renewal and

reducing repair and maintenance costs.

3.7.4 Whole life Cost reductions

The cost savings potentially afforded by tires through material substitution and performance

(lower construction, maintenance and renewal costs) could over the lifetime of a structure

significantly reduce its ‘whole-life cost’. The objective of whole life costing is to minimize

long-term expenditure by taking all costs associated with the provision of a structure into

account including initial construction and subsequent maintenance, and monitoring and

selecting the approach that offers the best value in the longer term [22].

3.7.5 Cost Savings by Protecting the Environment

One of the sustainability targets set by some governments for the construction industry is

replacing natural aggregates with secondary or recycled alternatives while also reducing

waste disposal. However, for use of alternative aggregates to be sustainable, there must be an

economic supply of sufficient quantity. There must also be methods of quality assurance plus

specification and a market appropriate to the costs of the processed wastes, as well as good

technical performance [3]. The accumulation of used tires at landfill sites presents the threat

of uncontrolled fires, producing a complex mixture of chemicals harming the environment

and contaminating soil and vegetation. Reuse and recycling generally costs the environment

less in resources to the benefit of wider society [3]. Additional benefits from using ground

rubber in landscaping applications include benefits related to avoided disposal space savings

(landfill space, land space), reduced risks to human health from tire piles, and avoided

emissions from tire pile fires. The need for quarrying and waste disposal is reduced with the

associated environmental impacts as well [25].

Provided that the cost of rubber aggregate can be kept to the lower end of the range, it can be

seen that the cost increase should not be onerous for manufacturers. The less stringent

processing requirements for rubber aggregate used in concrete are likely to further reduce the

cost of rubber aggregate in this application. Simultaneously, environmental concerns are

increasing all over the world. The recent Copenhagen summit of different nations has

demonstrated how big and critical are the environmental issues and the problem our world is

facing due to it. A growing fraction of the public in many modern societies would not hesitate

41

to favor the environmental protection. And that implies a certain willingness to pay more for

a commodity that is clearly identified as environmentally friendly or to contain recycled

materials. Recycling is associated with a number of cost items, like collection, separation,

processing, transportation, and the required capital investments. On the other hand, solid

waste that is not recycled or reused needs to be disposed in landfills, with direct costs in the

form of tipping fees and indirect costs in the form of environmental impact and depletion of

suitable landfill capacities. Hence, the successful use of waste tire chips and fibers in concrete

could provide one of the environmentally responsible and economically viable ways of

converting this waste into a valuable resource.

So far, a review of the characteristics and constituents of concrete in general has been done.

Following that, the use of recycled materials in concrete construction was discussed with

recycling tires as the main subject. Previous works on rubberized concrete were also

presented in this chapter. In addition, the production of rubber aggregates and the different

surface treatment methods utilized by other researchers were clearly seen. Moreover, in the

final parts of this chapter, the fresh and hardened properties of rubberized concrete were

thoroughly reviewed. As to the knowledge of the author of this research, there is no reported

research in Ethiopia in the use of recycled tires in concrete construction until now. Thus, the

research is aimed at evaluating the fresh and hardened properties of concrete produced by

partial replacement of the natural coarse aggregates with rubber aggregates that are obtained

from local sources and physically reprocessed for the purpose of this research.

All the information in this literature review have provided with a sufficient knowledge to go

to the next part of the research. In the subsequent chapter, the different tests conducted and

the properties of the ingredient materials from the test results are presented. Moreover, the

mix proportioning procedure utilized is also explained.

42

4. MATERIAL PROPERTIES AND MIX DESIGN

4.1 General Concrete mixtures with and without rubber aggregates for different compressive strength

values were prepared in this research work. The materials used to develop the concrete mixes

in this study were fine aggregate, coarse aggregate, rubber aggregate, cement, water and

admixture. A total of 16 mixes were prepared consisting of four types of concrete grades

(C15, C25, C30 and C40) with partial replacements of the coarse aggregate by 10, 25 and

50% of the rubber aggregate. Moreover, a control mix with no replacement of the coarse

aggregate was produced to make a comparative analysis. In the subsequent parts, the different

materials used in this study are discussed.

4.2 Cement The cement type used in this research was imported Maple Leaf OPC cement manufactured

in Pakistan. The main reason for using Ordinary Portland Cement (Type I) in this study is

that, this is by far the most common cement in use and is highly suitable for use in general

concrete construction when there is no exposure to sulphates in the soil or groundwater [1].

The choice of OPC from PPC also avoids any uncertainties in the results of the test.

4.3 Aggregates The relevant tests to identify the properties of the aggregates that were intended to be used in

this research were carried out. After that, corrective measures were taken in advance before

proceeding to the mix proportioning. In general, aggregates should be hard and strong, free of

undesirable impurities, and chemically stable. Soft, porous rock can limit strength and wear

resistance; it may also break down during mixing and adversely affect workability by

increasing the amount of fines. Aggregates should also be free from impurities: silt, clay, dirt

or organic matter. If these materials coat the surfaces of the aggregate, they will isolate the

aggregate particles from the surrounding concrete, causing a reduction in strength. Silt, clay,

and other fine materials will also increase the water requirements of the concrete, and organic

matter may interfere with cement hydration. To proportion suitable concrete mixes, certain

properties of the aggregate must be known. These are; shape and texture, size gradation,

moisture content, specific gravity and bulk unit weight [14].

43

4.3.1 Properties of the Fine Aggregate

The fine aggregate sample used in this experiment was purchased from local sand suppliers at

Addis Ababa around ‘Legehar area’. To investigate its properties and suitability for the

intended application, the following tests were carried out.

- sieve analysis for fine aggregate and fineness modulus

- Specific gravity and absorption capacity for fine aggregate

-Moisture content for fine aggregate

-Silt content for fine aggregate

-Unit weight of fine aggregate

4.3.1.1 Sieve Analysis for Fine Aggregate and Fineness Modulus

Sieve analysis is a procedure for the determination of the particle size distribution of

aggregates using a series of square or round meshes starting with the largest. It is used to

determine the grading, fineness modulus, an index to the fineness, coarseness and uniformity

of aggregates. The quality of concrete to be produced is very much influenced by the

properties of its aggregates. Aggregate grain size distribution or gradation is one among these

properties and should be given due consideration [38].

The original test sample was not meeting the gradation requirement and therefore blending of

the fine aggregate passing the 1.18 mm sieve was done with the original sample in a

proportion of 60%:40%. Table 4.1 below shows the percentage passing each sieve size and

Figure 4.1 shows the corresponding graph.

44

Table 4.1 Sieve Analysis Test for Fine Aggregate.

Sieve Size

(mm)

Wt. of Sieve (gm)

Wt. of Sieve and Retained

(gm)

Wt. Retained

(gm)

% age Retained

Cumul. Retained

% passing

Lower Limit

Upper Limit

9.5 586 586 0 0.00 0.00 100.00 100.00 100

4.75 567 576 9 1.80 1.80 98.20 95.00 100.00

2.36 521 535 14 2.80 4.60 95.40 80.00 100.00

1.18 529 584 55 11.00 15.60 84.40 50.00 85.00

0.06 506 719 213 42.60 58.20 41.80 25.00 60.00

0.03 478 627 149 29.80 88.00 12.00 10.00 30.00

0.015 462 512 50 10.00 98.00 2.00 2.00 10.00pan 423 431 8 1.60 99.60 0.40

Fig. 4.1 Graph for Sieve analysis of Fine aggregate

Fineness modulus (F.M) = ∑ cumulative coarser (%) ………………..[38] 100 F.M. = 266.2/100 =2.66

0.00

20.00

40.00

60.00

80.00

100.00

120.00

9.5 4.75 2.36 1.18 0.6 0.3 0.15

% P

assi

ng

Sieve Size

Fine Aggregate

% Passing

Lower Limit

Upper Limit

45

4.3.1.2 Specific gravity and absorption capacity of fine aggregate

The specific gravity of an aggregate is considered to be a measure of strength or quality of

the material. The specific gravity of a substance is the ratio between the weight of the

substance and that of the same volume of water. This definition assumes that the substance is

solid throughout. Aggregates, however, have pores that are both permeable and impermeable.

The structure of the aggregate (size, number, and continuity pattern) affects water absorption,

permeability, and specific gravity [38].

The following results were found for the fine aggregate sample.

Bulk Specific gravity=2.41

Bulk Specific gravity (SSD basis)=2.51

Apparent specific gravity=2.69

Absorption capacity =4.38 %

4.3.1.3 Moisture content of fine aggregate

A design water cement ratio is usually specified based on the assumption that aggregates are

inert (neither absorb nor give water to the mixture). But in most cases aggregates from

different sources do not comply with this i.e. wet aggregates give water to the mix and drier

aggregates take water from the mix affecting in both cases, the design water cement ratio and

therefore workability and strength of the mix. In order to correct for these discrepancies, the

moisture content of aggregates has to be determined [38].

The moisture content of the fine aggregate sample used in this study was tested at different

times prior to mixing and it was found to be in the range of 2.04 %.

4.3.1.4 Silt content of fine aggregate

Sand is a product of natural or artificial disintegration of rocks and minerals. Sand is obtained

from glacial, river, lake, marine, residual and wind-blown deposits. These deposits however

do not provide pure sand. They often contain other materials such as dust, loam and clay that

are finer than sand. The presence of such materials in sand used to make concrete or mortar

decreases the bond between the materials to be bound together and hence the strength of the

mixture. The finer particles do not only decrease the strength but also the quality of the

mixture produced resulting in fast deterioration. Therefore, it is necessary that one make a

test on the silt content and check against permissible limits [38].

From the silt content test performed on the sand, it was found that the original silt content

was 11%. According to the Ethiopian standard, it is recommended to wash the sand or reject

46

if the silt content exceeds a value of 6 % [38]. Therefore, it was necessary to wash the sand to

improve the property. Finally, the silt content reached 2% that is within the acceptable range.

4.3.1.5 Unit weight of fine aggregate

Unit weight can be defined as the weight of a given volume of graded aggregate. It is thus a

density measurement and is also known as bulk density. But this alternative term is similar to

bulk specific gravity, which is quite a different quantity, and perhaps is not a good choice.

The unit weight effectively measures the volume that the graded aggregate will occupy in

concrete and includes both the solid aggregate particles and the voids between them. The unit

weight is simply measured by filling a container of known volume and weighing it. Clearly,

however, the degree of compaction will change the amount of void space, and hence the

value of the unit weight. Since the weight of the aggregate is dependent on the moisture

content of the aggregate, a constant moisture content is required. Oven dried aggregate

sample is used in this test [38]. The unit weight of the fine aggregate sample used was found

to be 1520 kg/m3.

4.3.2 Properties of the coarse aggregate

Coarse aggregate for concrete shall consist of natural gravel or crushed rock or a mixture of

natural gravel and crushed rock. Coarse aggregate used in this research was purchased

from Tikur Abay Construction Company.

In a similar manner like the fine aggregate, laboratory tests were carried out to

identify the physical properties of the coarse aggregate and the results are shown in

Table 4.2 below. Table 4.3 shows the sieve analysis test results and figure 4.2 shows the

corresponding graph.

Table 4.2 Physical Properties of the Coarse Aggregate.

Description Test Result

Moisture content 1.37 %

Unit weight of coarse aggregate 1533.25 kg/m3

Bulk Specific gravity 2.79

Bulk specific gravity(SSD basis) 2.84

Apparent specific gravity 2.93

Absorption capacity 1.72 %

Crushing value of aggregate 17.83 %

Los Angeles Abrasion Test 14.9 %

47

Table 4.3 Sieve Analysis for the Coarse Aggregate.

Sieve Size

(mm)

Wt. of Sieve (gm)

Wt. of Sieve and Retained

(gm)

Wt. of Retained

(gm)

% Retain.

Cum. Retain.

% Pass.

Lower Limit

Upper Limit

37.5 1188 1188 0 0.00 0.00 100.00 100.00

19 1419 1419 0 0.00 0.00 100.00 90.00 100.00

12.5 1166 3645 2479 48.36 48.36 51.64 40.00 80.00

9.5 1171 2682 1511 29.48 77.84 22.16 20.00 55.00

4.75 1194 2222 1028 20.05 97.89 0.35 0.00 10.00

Pan 1060 1150 90 1.76 99.65 0.35 0.00 5.00

Fig. 4.2 Graph for Sieve analysis of Coarse aggregate

0.00

20.00

40.00

60.00

80.00

100.00

120.00

37.5 19 12.5 9.5 4.75

% P

assi

ng

Sieve Size

Natural Coarse Aggregate

% Passing

Lower Limit

Upper Limit

48

4.3.3 Rubber aggregate

The source of the rubber aggregate was recycled tires which were collected from the local

market commonly known as ‘Goma Tera’ around Merkato area, Addis Ababa. For uniformity

of the concrete production and convenience, all the tires collected were from those which

were originally produced from Matador Addis Tire factory and the type was a medium truck

tire as shown in figure 4.3. The reason for this is that the factory is the only tire producing

company in the country as the other tires in the market are imported ones and the reason for

choosing medium truck tires is that they can give the required shape and size which is similar

to the common natural gravel.

This study has concentrated on the performance of a single gradation of crumb rubber

prepared by manual cutting. The maximum size of the rubber aggregate was 20 mm as shown

in figure 4.4. Specific gravity test was conducted on the rubber aggregate chips and found to

be 1.123. The rubber aggregates used in the present investigation were made by manually

cutting the tire in to the required sizes. It was very laborious, time consuming and was not

easy to handle at the initial stages. However, all this complications can be easily sorted out if

a large scale production is devised and proper cutting tools and machineries are made for this

particular usage.

Fig. 4.3 Used medium truck tires Fig. 4.4 20 mm size Rubber aggregate

To come up with a rough cohesive surface of the rubber aggregate, surface treatment was

done using cement paste. Rubber aggregates coated with cement paste were produced as

follows:

- After thoroughly washing the sample to remove dusts and impurities from

the surface of the particles, the rubber aggregates were then immersed in

49

water for 24 hours until all particles were fully saturated (wetted both inside

and on the surface).

- The plain rubber aggregates were then taken to the saturated surface dry

(SSD) condition by spreading them in a thin layer on a clean surface free

from dust and rolled in a towel until all visible films of water are removed.

In this condition, the rubber aggregate reached the saturated surface dry

condition and thus requiring no alteration to the quantity of mixing water.

- The next step was the surface treatment of the rubber aggregates. For this

the procedure suggested by Cairns R. et al was adopted which utilizes a

coating with cement paste. The rubber aggregates were thoroughly coated

with a thin layer of cement paste, a mixture of cement powder and water.

The average weight of cement used for coating was 3.23 kg for every cubic

meter of the rubberized concrete. The coated rubber aggregates were then

air dried by spreading them on a clean surface for about 24 hours.

All the cement paste coating had an effect on the hydrophilicity of the rubber allowing it to

adhere better to the cement paste that surrounded it as per the previous experience discussed

in the literature review part of this research section 3.3.2.1. The rubber aggregate particles

coated with cement paste are shown in figure 4.5 below.

4.5 (a) 4.5 (b)

Fig. 4.5 Rubber aggregates coated with Cement paste

4.4 Chemical Admixture The admixture used in this research was Conplast SP430 which is a high performance super

plasticizing admixture produced by FOSROC constructive solutions. Conplast SP430

50

conforms to ASTM C494 as Type A and Type F depending on the dosage used [39]. The

main reasons for using this admixture in this study are:

-To make possible major reductions in water cement ratio which allows the

production of desired strength concrete without excessive cement contents and

also satisfying the durability requirements in the mix design procedure.

-To achieve increased workability levels with lower water cement ratios.

-To achieve improved cohesion and particle dispersion which minimizes

segregation and bleeding. This is a very essential characteristic as it can

strengthen the weak cohesive nature and the floating tendency of rubber

aggregates in the concrete.

The supplier’s product catalogue recommends a dosage that ranges from 0.70 to 2.00

liters/100 kg of cementitious material for a high workability concrete [39]. In this research,

the minimum dosage of 0.7 liters/100 kg of cement was applied to the concrete mixes in all

cases of the control concretes as well as the rubberized concrete mixes. The actual values

used for each concrete class can be referred from Tables 4.6 and 4.7.

4.5 Water

The quality of the water plays a significant role in concrete production. Impurities in water

may interfere with the setting of the cement, may adversely affect the strength of the concrete

or cause staining of its surface, and may also lead to corrosion of the reinforcement. For these

reasons, the suitability of water for mixing and curing purposes should be considered. In this

research, tap water supplied by Addis Ababa water and sewerage authority at room-

temperature was used in all mixes.

4.6 Selection of Concrete mix Proportions (Mix Design)

4.6.1 General

The selection of mix proportions is a process of choosing suitable ingredients of concrete and

determining their relative quantities with the object of producing as economically as possible

concrete of certain minimum properties, notably strength, durability and a required

consistency. The key to achieving a strong, durable concrete rests in the careful proportioning

and mixing of the ingredients. A concrete mixture that has no enough paste to fill all the

voids between the aggregates will be difficult to place and will produce rough, honeycombed

surfaces and porous concrete. A mixture with an excess of cement paste will be easy to place

51

and will produce a smooth surface; however, the resulting concrete is likely to shrink more

and be uneconomical. A properly designed concrete mix will possess the desired workability

for the fresh concrete and the required durability and strength for the hardened concrete.

Portland cement's chemistry comes to life in the presence of water. Cement and water form a

paste that coats each particle of stone and sand. Through a chemical reaction called hydration,

the cement paste hardens and gains strength. The character of the concrete is determined by

the quality of the paste. The strength of the paste, in turn, depends on the ratio of water to

cement. High-quality concrete is produced by lowering the water-cement ratio as much as

possible without sacrificing the workability of fresh concrete [16]. Generally, using less water

produces a higher quality concrete provided the concrete is properly placed, consolidated, and

cured and fulfills any durability requirements requested.

4.6.2 Testing Arrangement

In this study, a total of 16 mixes consisting of four types of concrete grades ( C15, C25, C30

and C40) were produced with partial replacements of the coarse aggregate by 10, 25 and 50

% of the rubber aggregate. Moreover, a control mix with no replacement of the coarse

aggregate was produced to make a comparative analysis. The mix design process adopted

was the Department of Environment (DOE) method.

The mixture proportions of the basic ingredients i.e. cement, water, and fine aggregate, were

the same for the control concrete and rubberized concrete. However, a certain amount of the

coarse aggregate was replaced by an equal volume of rubber aggregate to form rubberized

concrete. Four control mix designs, C15, C25, C30 and C40 were prepared for this

investigation. The main reason for selecting this concrete grades is that these are by far the

most commonly used concrete grades for most of the concrete construction works and hence

application of the research can be more feasible.

The following tests were performed on the different concrete samples produced in this study.

1) Slump test for workability

2) Determination of unit weight of hardened concrete

3) Compressive strength test (7th, 28th, and 56th day)

4) Splitting tensile strength test

5) Impact Resistance test, and

6) Flexural strength test

52

4.6.3 Trial Mixes

Before proceeding to the preparation of the main mix design of the research, trial mixes were

prepared for each of the control mixes. A particular mix design method determines a set of

mix proportions for producing a concrete that has approximately the required properties of

strength and workability. The method however is based on simplified classification for type

and quality of the materials and it remains to check whether or not the particular aggregates

and cement selected for use in a given case will behave as anticipated. This is the object of

making the trial mix, and the subsequent feedback of information from the trial mix is an

essential part of the mix design process [40]. Table 4.4 below shows the material constituents

of the trial mix.

Table 4.4 Material constituents of the Trial mixes.

Grade Comp. streng

(MPa) Cement (kg/m3)

Fine agg. (kg/m3)

Coarse Agg. (kg/m3)

water (kg)

Admixture (lit/m3)

C15 15 310 660 1285 170 2.17

C25 25 330 655 1270 170 2.31

C30 30 360 645 1250 170 2.52

C40 40 380 640 1240 170 2.66

The slump test and compressive strength test results of the trial mix are tabulated in Table 4.5

below. The 7-day compressive strength tests are conducted for the trial mixes and the result is

extrapolated to possible 28-day strength. Sidney Mindess et al suggested that the ratio of the

28-day strength to the 7-day strength lies between 1.3 and 1.7 but is usually less than 1.5 and

it depends on the cement type and curing temperature [14]. In other words, the 7 day strength

will be on the range between 60 and 75 % of the 28 day strength. For this study, considering

the relative early strength development of OPC cement, the maximum value of 75 % of

strength achievement at the 7 day was assumed to forecast the 28-day strength of the trial

mixes. Later on, it was found out that the compressive strength test results of the final mixes

have shown a similar trend of relationship between the 7th and the 28th day strengths.

53

Table 4.5 Slump and Compressive Strength Test results of the Trial mix.

Grade Slump (mm)

Comp. Strength (MPa)

7 day Forecasted 28 day

C15 8 36.25 45

C25 19 39.15 49

C30 23 44.3 55

C40 11 48.27 60

For the workability, the designed slump was 10-30 mm. Hence, all the slump results except

for C15 are within the intended range.

For the purpose of preparing the final mix design, it was necessary to evaluate the

compressive strength test results of the trial mix. The 7th and the forecasted 28th day

compressive strength test results revealed that the attained results have exceeded the original

intended values. This led to the understanding that there is still much more room for adjusting

the mix design and a more economical mix can be produced. Based on this, the mix design

was readjusted and the final proportioning for the main concrete samples was prepared.

The mix proportions of the final mix are presented in Table 4.6 below. The designations A,

B, C and D indicate the concrete grades of 15, 25, 30 and 40 MPa compressive strengths

respectively. Whereas M1, M2, M3 and M4 indicate the corresponding concrete grades with

percentage rubber aggregate replacements of 0, 10, 25 and 50 % of the coarse aggregate

respectively.

Example AM1- stands for the mix of C15 concrete with no rubber aggregate replacement

AM2- stands for C15 concrete with 10 % volume of the coarse aggregate of the

control mix replaced by an equivalent volume of the rubber aggregate.





54

Table 4.6 Mix Proportioning for 1m3 of Concrete.

Type Grade Cement (kg/m3)

Water (kg/m3)

Fine agg. (kg/m3)

Coarse agg. (kg/m3)

Rubber agg. (kg/m3)

Admix. (lit/m3)

AM1 Control C-15 230 170 690 1340.0 0.0 1.61 A M2 C-15 230 170 690 1206.0 53.0 1.61 A M3 C-15 230 170 690 1005.0 132.5 1.61 A M4 C-15 230 170 690 670.0 264.9 1.61 BM1 Control C-25 280 170 670 1305.0 0.0 1.96 B M2 C-25 280 170 670 1174.5 51.6 1.96 B M3 C-25 280 170 670 978.8 129.0 1.96 B M4 C-25 280 170 670 652.5 258.0 1.96 CM1 Control C-30 320 170 660 1275.0 0.0 2.24 C M2 C-30 320 170 660 1147.5 50.4 2.24 C M3 C-30 320 170 660 956.3 126.0 2.24 C M4 C-30 320 170 660 637.5 252.1 2.24 DM1 Control C-40 360 170 645 1250.0 0.0 2.52 D M2 C-40 360 170 645 1125.0 49.4 2.52 D M3 C-40 360 170 645 937.5 123.6 2.52 D M4 C-40 360 170 645 625.0 247.1 2.52

4.6.4 Batching of Materials

Saturated Surface dry aggregates were used for the concrete mixes under research. Cement

and aggregates were batched by weight while water and chemical admixtures were batched

by volume. Chemical admixtures in the form of solutions were mixed with water and used in

the preparation of concrete mixes. All the replacement for the coarse aggregate was done on a

volume basis. To come up with the required volume of concrete to be produced, the total

number of test specimens has to be to be determined primarily. Hence, the specimens

required were as follows:

Nine cube samples for compressive strength test =0.03m3

Two cylinder samples for tensile strength test =0.01 m3

Two beam samples for flexural strength test =0.01m3

Two cylinder samples for impact resistance test =0.01 m3

Total =0.06 m3

55

An additional 11 % volume is considered for the compaction factor as well as for the wastage

that certainly occurs during the mixing and casting process. Finally, the required concrete

volume to be produced in each of the 16 test arrangements was found to be 0.068 m3. Prior to

the mixing process, all the required ingredients to produce the overall volume of concrete

planned were delivered to the laboratory.

Table 4.7 Mix Proportions for 0.068 m3 of concrete.

Type Grade Cement

(kg) Water (kg)

Fine agg. (kg)

Coarse agg. (kg)

Rubber agg. (kg)

Admix. (lit)

AM1 Control C-15 15.64 11.56 46.92 91.12 0.00 0.11 A M2 C-15 15.64 11.56 46.92 82.01 3.60 0.11 A M3 C-15 15.64 11.56 46.92 68.34 9.01 0.11 A M4 C-15 15.64 11.56 46.92 45.56 18.02 0.11 BM1 Control C-25 19.04 11.56 45.56 88.74 0.00 0.13 B M2 C-25 19.04 11.56 45.56 79.87 3.51 0.13 B M3 C-25 19.04 11.56 45.56 66.56 8.77 0.13 B M4 C-25 19.04 11.56 45.56 44.37 17.54 0.13 CM1 Control C-30 21.76 11.56 44.88 86.70 0.00 0.15 C M2 C-30 21.76 11.56 44.88 78.03 3.43 0.15 C M3 C-30 21.76 11.56 44.88 65.03 8.57 0.15 C M4 C-30 21.76 11.56 44.88 43.35 17.14 0.15 DM1 Control C-40 24.48 11.56 43.86 85.00 0.00 0.17 D M2 C-40 24.48 11.56 43.86 76.50 3.36 0.17 D M3 C-40 24.48 11.56 43.86 63.75 8.40 0.17 D M4 C-40 24.48 11.56 43.86 42.50 16.81 0.17

4.6.5 Mixing and Test Sample Preparation

It is essential that the mix ingredients are properly mixed so as to produce fresh concrete in

which the surface of all aggregate particles is coated with cement paste and which is

homogeneous on the macro-scale and therefore possessing uniform properties [1]. Thorough

mixing is essential for the complete blending of the materials that are required for the

production of homogeneous, uniform concrete [14]. The type of mixer used in the laboratory

for this research is a pan type as shown in Figure 4.6 below.

56

Fig. 4.6 Concrete Mixing using a Pan Mixer

According to Neville A.M., this type of mixer has a considerable advantage as compared to

the other types especially for this kind of research work. Pan mixers offer the possibility of

observing the concrete in them, and therefore of adjusting the mix in some cases. They are

particularly efficient with stiff and cohesive mixes. They are also suitable for mixing very

small quantities of concrete hence they are mostly used in the laboratory [1].

All the dry ingredients were blended together prior to adding water. All batches were then

wet-mixed by adding the required water and super plasticizer admixture SP430 was also

added to the wet mix.

In this chapter, the materials used in the research work were discussed. After identifying the

properties of the materials, the testing arrangement was presented which was followed by the

mix proportioning of the trial and final mixes respectively. In the subsequent chapter, the test

results and discussions are presented.

57

5. TEST RESULTS AND DISCUSSIONS 5.1 General This section describes the results of the tests carried out to investigate the various properties

of the rubberized concrete mixes prepared in contrast with the control mixes. In the

succeeding parts, the results for workability, unit weight, compressive strength, splitting

tensile strength impact resistance and flexural strength tests are presented. Analysis and

discussions are also made on the findings.

5.2 Fresh Concrete Properties

5.2.1 Workability Test

A concrete mix must be made of the right amount of cement, aggregates and water to make

the concrete workable enough for easy compaction and placing and strong enough for good

performance in resisting stresses after hardening. If the mix is too dry, then its compaction

will be too difficult and if it is too wet, then the concrete is likely to be weak [38].

During mixing, the mix might vary without the change very noticeable at first. For instance, a

load of aggregate may be wetter or drier than what is expected or there may be variations in

the amount of water added to the mix. These all necessitate a check on the workability and

strength of concrete after producing. Slump test is the simplest test for workability and are

most widely used on construction sites. In the slump test, the distance that a cone full of

concrete slumps down is measured when the cone is lifted from around the concrete. The

slump can vary from nil on dry mixes to complete collapse on very wet ones. One drawback

with the test is that it is not helpful for very dry mixes [38]. The slump test carried out was

done using the apparatus shown in Figure 5.1 below.

Fig. 5.1 Slump Test

58

The mould for the slump test is in the form of a frustum of a cone, which is placed on top of a

metal plate. The mould is filled in three equal layers and each layer is tamped 25 times with a

tamping rod. Surplus concrete above the top edge of the mould is struck off with the tamping

rod. The cone is immediately lifted vertically and the amount by which the concrete sample

slumps is measured. The value of the slump is obtained from the distance between the

underside of the round tamping bar and the highest point on the surface of the slumped

concrete sample. The types of slump i.e. zero, true, shear or collapsed are then recorded.

Table 5.1 shows the results of the slump test for the control concretes and the rubberized

concretes.

Table 5.1 Slump Test Results.

No. Specimen Grade % rubber w/c ratio Slump (mm) 1 AM1 C 15 0.00 0.75 32

2 AM2 C 15 10.00 0.75 38

3 AM3 C 15 25.00 0.75 41

4 AM4 C 15 50.00 0.75 49

5 BM1 C 25 0.00 0.60 7

6 BM2 C 25 10.00 0.60 14

7 BM3 C 25 25.00 0.60 21

8 BM4 C 25 50.00 0.60 42

9 CM1 C 30 0.00 0.53 9

10 CM2 C 30 10.00 0.53 15

11 CM3 C 30 25.00 0.53 21

12 CM4 C 30 50.00 0.53 27

13 DM1 C 40 0.00 0.47 8

14 DM2 C 40 10.00 0.47 16

15 DM3 C 40 25.00 0.47 18

16 DM4 C 40 50.00 0.47 13

The introduction of recycled rubber tires to concrete significantly increased the slump and

workability. All concrete mixes were designed to have a slump of 10-30 mm. As can be seen

from the results above, the control concretes (BM1, CM1 and DM1) had a slump of less than

59

10 mm which is below the designed value whereas the result for AM1 (32 mm) is close to the

designed range.

It was noted that the slump has increased as the percentage of rubber aggregate was increased

in all samples except DM4 which needs further investigation. In the low strength category

(AM1, AM2, AM3 and AM4 ) the observed slump is between 32 mm and 49 mm. This

shows that the workability decreases as the strength of the concrete increases for a given

amount of w/c ratio in rubberized concrete. But in the literature review it was noted that

different researchers reported a reduction in slump in rubberized concrete mixes [13, 26, and

36]. The possible reason for the differences between the previous studies and this research

can be the use of admixtures. Super plasticizing admixtures greatly increase the workability

of the concrete and the improvement to the workability of the rubberized concrete can be

attributed to the admixture. In most of the earlier studies, the use of admixtures to improve

the workability of the concrete was not explained. Nevertheless, in a research by Kumaran

S.G. et al, an admixture was used in rubberized concrete mix design but its effect on the

workability of the rubberized concrete mix was not clearly explained [2].

A different observation which was noticed while casting the rubberized concrete was that the

rubber aggregates have a high tendency to come out to the top surface when vibrated by a

table vibrator. This is due to the low specific gravity of the rubber aggregate. In general,

rubberized concrete mixes did not pose any difficulties in terms of finishing, casting, or

placement and can be finished to the same standard as plain concrete.

5.3 Hardened Concrete Properties The different tests that have been carried out to establish the hardened properties of the

concrete samples produced were; determination of unit weight, compressive strength,

splitting tensile strength, impact resistance and flexural strength tests.

5.3.1 Determination of Unit weight

The unit weight values used for the analysis of this section are measured from the concrete

cube samples after 28 days of standard curing. From the results, it was found out that a

reduction of unit weight up to 24 % was observed when 50 % by volume of the coarse

aggregate was replaced by rubber aggregate in sample AM4. Whereas 3.39 and 9.48 %

reductions were observed for 10 and 25 % rubber aggregate replacement in samples AM2 and

AM3 respectively. In the second category (B group) a reduction in unit weight of 3.57 %,

60

7.72 and 18.62 % was noted for 10, 25 and 50 % of the coarse aggregate replacement by

rubber aggregate. In samples CM1, CM2 and CM3 the reduction in unit weight was 4.18,

6.48 and 16.92 % for 10, 25 and 50 % of the replacement of coarse aggregate with the rubber

aggregate respectively. In Mix category D, a reduction in unit weight of 2.53, 6.41 and 14.02

% were seen for the respective increments in the replacement of rubber aggregates.

The low specific gravity of the rubber chips, 1.123, as compared to the mineral coarse

aggregates, 2.84, produced a decrease in the unit weight of the rubberized concrete, as shown

in Table 5.2. Since crumb rubber is nearly two and half times lighter than the mineral coarse

aggregate, it was expected that the mass density of the mix would be significantly reduced.

The results for the unit weight are presented in Table 5.2 below and Figure 5.2 demonstrates

the comparative decrease in unit weight of the rubberized concrete in contrast with the

respective control concrete.

Table 5.2 Unit weights of the control concretes and rubberized concrete.

No. Specimen Grade % rubberUnit wt. (kg/m3)

% Reduction

1 AM1 C 15 0.00 2468.82 0.00

2 AM2 C 15 10.00 2385.21 3.39

3 AM3 C 15 25.00 2234.90 9.48

4 AM4 C 15 50.00 1874.45 24.08

5 BM1 C 25 0.00 2508.78 0.00

6 BM2 C 25 10.00 2419.33 3.57

7 BM3 C 25 25.00 2314.99 7.72

8 BM4 C 25 50.00 2041.75 18.62

9 CM1 C 30 0.00 2482.95 0.00

10 CM2 C 30 10.00 2379.16 4.18

11 CM3 C 30 25.00 2322.07 6.48

12 CM4 C 30 50.00 2062.89 16.92

13 DM1 C 40 0.00 2573.41 0.00

14 DM2 C 40 10.00 2411.57 2.53

15 DM3 C 40 25.00 2315.58 6.41

16 DM4 C 40 50.00 2127.26 14.02

61

5.2 (a)

5.2 (b)

5.2 (c)

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

AM1 AM2 AM3 AM4

Unit w

eight (kg/m

3 )

Specimens

C ‐15

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

BM1 BM2 BM3 BM4

Unit w

eight (kg/m

3 )

Specimens

C‐25

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

CM1 CM2 CM3 CM4

Unit w

eight (kg/m

3 )

Specimens

C‐30

62

5.2 (d)

Fig. 5.2 Graphical Comparison of Unit weight values

Using concrete with a lower density can result in significant benefits in terms of load bearing

elements of smaller cross-section and a corresponding reduction in the size of foundations.

Occasionally, the use of concrete with a lower density permits construction on ground with a

low load-bearing capacity. Furthermore, with lighter concrete, the formwork need withstand a

lower pressure than would be in case with normal weight concrete, and also the total mass of

materials to be handled is reduced with a consequent increase in productivity. Concrete that

has a lower density also gives better thermal insulation than ordinary concrete [1]. Therefore,

the reduced density of concrete containing rubbers aggregates can provide with all the

benefits mentioned which are associated with a lower density.

5.3.2 Compressive strength Test

The compressive strengths of concrete specimens were determined after 7, 28 and 56 days of

standard curing. For rubberized concrete, the results show that the addition of rubber

aggregate resulted in a significant reduction in concrete compressive strength compared with

the control concrete. This reduction increased with increasing percentage of rubber aggregate.

Losses in compressive strength of 11.38 % (AM2), 16.30 % (BM2), 19.04 % (CM2) and

17.25 % (DM2) were observed when 10% of the coarse aggregate was replaced by an

equivalent volume of rubber aggregate. The observed losses of strength when 25 % of the

coarse aggregate was replaced by rubber aggregate were 28.19 % (AM3), 29.62 % (BM3),

34.94 % (CM3) and 31.15 % (DM3). For rubberized concrete containing 50% by volume of

rubber aggregate replacement, losses of 55.55 % (AM4), 64.02 % (BM4), 61.67 % (CM4)

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

DM1 DM2 DM3 DM4

Unit w

eight (kg/m

3 )

Specimens

C‐40

63

and 59.22 % (DM4) were noticed. Table 5.3 below shows the results of the 7th, 28th and 56th

day compressive strength tests.

Table 5.3 Results of compressive strength tests.

Compressive

Strength (MPa) % Strength loss

No. Spec. Grade %

rubber 7

days28

days56

days 7

days 28

days 56

days

1 AM1 C 15 0.00 15.07 22.50 28.19 0.00 0.00 0.00

2 AM2 C 15 10.00 13.93 19.94 24.07 7.57 11.38 14.64

3 AM3 C 15 25.00 13.35 16.15 19.97 11.39 28.19 29.18

4 AM4 C 15 50.00 7.20 10.00 13.32 52.23 55.55 52.74

5 BM1 C 25 0.00 29.33 41.09 46.62 0.00 0.00 0.00

6 BM2 C 25 10.00 24.30 34.39 40.17 17.15 16.30 13.84

7 BM3 C 25 25.00 23.55 28.92 31.08 19.69 29.62 33.34

8 BM4 C 25 50.00 12.17 14.78 18.00 58.51 64.02 61.39

9 CM1 C 30 0.00 35.78 49.13 55.34 0.00 0.00 0.00

10 CM2 C 30 10.00 31.71 39.78 47.37 11.39 19.04 14.41

11 CM3 C 30 25.00 19.92 31.97 36.83 44.33 34.94 33.45

12 CM4 C 30 50.00 14.22 18.83 23.63 60.27 61.67 57.30

13 DM1 C 40 0.00 42.47 55.74 60.20 0.00 0.00 0.00

14 DM2 C 40 10.00 37.25 46.13 51.40 12.29 17.25 14.62

15 DM3 C 40 25.00 32.53 38.38 48.51 23.40 31.15 19.42

16 DM4 C 40 50.00 16.20 22.73 28.42 61.86 59.22 52.80

Figure 5.3 below illustrates the trend of strength development in the different concrete

specimens prepared and Figure 5.4 shows the comparison of the strength achieved in contrast

with the control concrete.

Compressive

Stren

gth (M

Pa)

1

1

2

2

3

3

4

4

5

Compressive

Stren

gth (M

Pa)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

AM1

BM1

5.

5.3

AM2

BM2

64

.3 (a)

3 (b)

Specimens

C‐15

Specimens

C‐25

AM3

BM3

AM4

7 days

28 day

56 day

BM4

7 days

28 days

56 days

s

ys

ys

65

5.3 (c)

5.3 (d)

Fig. 5.3 Compressive Strength Development

0.00

10.00

20.00

30.00

40.00

50.00

60.00

CM1 CM2 CM3 CM4

Compressive

Stren

gth (M

Pa)

Specimens

C‐30

7 days

28 days

56 days

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

DM1 DM2 DM3 DM4

Compressive

Stren

gth (M

Pa)

Specimens

C‐40

7 days

28 days

56 days

66

5.4 (a)

5.4 (b)

5.4 (c)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

7 days 28 days 56 days

Compressive

Stren

gth(MPa

)

Duration

C‐15AM1

AM2

AM3

AM4

0.00

10.00

20.00

30.00

40.00

50.00

7 days 28 days 56 daysCompressive

Stren

gth(MPa

)

Duration

C‐25

BM1

BM2

BM3

BM4

0.00

10.00

20.00

30.00

40.00

50.00

60.00

7 days 28 days 56 daysCompressive

Stren

gth (M

Pa)

Duration

C‐30

CM1CM2CM3CM4

67

5.4 (d)

Fig. 5.4 Comparisons of Compressive strength Test Results

The reason for the compressive strength reductions could be attributed both to a reduction of

quantity of the solid load carrying material and to the lack of adhesion at the boundaries of

the rubber aggregate. Soft rubber particles behave as voids in the concrete matrix.

Considering the very different mechanical properties of mineral aggregates and rubber

aggregates, mineral aggregates usually have high crushing strength and they are relatively

incompressible, whereas rubber aggregates are ductile, compressible and resilient. Rubber

has a very low modulus of elasticity of about 7MPa and a Poisson’s ratio of 0.5 [13].

Therefore, rubber aggregates tend to behave like weak inclusions or voids in the concrete,

resulting in a reduction in compressive strength. It is well known that the presence of voids in

concrete greatly reduces its strength. The existence of 5 % of voids can lower strength by as

much as 30 % and even 2 % voids can result in a drop of strength of more than 10% [1].

Another observation while carrying out the compressive strength test was the nature of crack

formation. In rubberized concrete, crack formation is different from plain concrete because

bond strength between rubber and cement paste is poor than that of between aggregate and

cement paste. Therefore, initial cracks were formed around rubber aggregates and cement

paste in rubberized concrete.

Although the compressive strength values have considerably decreased with the addition of

waste tire pieces as seen in Table 5.3, their values are still in a reasonable range for a 10 and

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

7 days 28 days 56 days

Compressive

Stren

gth (M

Pa)

Duration

C‐40

DM1DM2DM3DM4

68

25 % replacement values because the intended compressive strength of 15, 25, 30, and 40

MPa respectively were achieved in these categories.

5.3.3 Splitting tensile strength Test

The common method of estimating the tensile strength of concrete is through an indirect

tension test. The splitting tensile test is carried out on a standard cylinder tested on its side in

diametral compression. The horizontal stress to which the element is subjected is given by the

following equation.

Horizontal tension σt= 2P/πLD ...………………….……………… [14]

Where: P - the applied compressive load

L- the cylinder length, and

D- the cylinder diameter

The test is carried out on cylindrical specimens using a bearing strip of 3 mm plywood that is

free of imperfections and is about 25 mm wide. The specimen is aligned in the machine and

the load is then applied [14]. Figure 5.5 below shows the testing method for splitting tensile

strength test and Table 5.4 shows the splitting tensile strength test results. The relative

percentage of strength loss with respect to the control mixes are also tabulated together.

Fig. 5.5 Splitting tensile strength Test

3 mm plywood

69

Table 5.4 Splitting Tensile Strength Test Results.

No. Spec. Grade %

rubber Splitting Load(kN)

Splitting Streng. (MPa)

% Strength loss

1 AM1 C 15 0 172 2.43 0.00

2 AM2 C 15 10 139.95 1.98 18.63

3 AM3 C 15 25 126.9 1.80 26.22

4 AM4 C 15 50 97.5 1.38 43.31

5 BM1 C 25 0 242.9 3.44 0.00

6 BM2 C 25 10 189.8 2.69 21.86

7 BM3 C 25 25 168.95 2.39 30.44

8 BM4 C 25 50 110.95 1.57 54.32

9 CM1 C 30 0 274.6 3.88 0.00

10 CM2 C 30 10 221.8 3.14 19.23

11 CM3 C 30 25 134.75 1.91 50.93

12 CM4 C 30 50 120.9 1.71 55.97

13 DM1 C 40 0 257 3.64 0.00

14 DM2 C 40 10 278.35 3.94 -8.31

15 DM3 C 40 25 188.4 2.67 26.69

16 DM4 C 40 50 139.8 1.98 45.60

For rubberized concrete, the results show that the splitting tensile strength decreased with

increasing rubber aggregate content in a similar manner to that observed in the compressive

strength tests. However, there was a relatively smaller reduction in splitting tensile strength

as compared to the reduction in the compressive strength.

Losses of up to 18.63% (AM2), 21.86 % (BM2), 19.23 % (CM2) and a gain of 8.31% (DM2)

were observed when 10% of the coarse aggregate was replaced by rubber aggregate. The

observed losses of strength when 25 % of coarse aggregate was replaced by rubber aggregate

were 26.22% (AM3), 30.44 % (BM3), 50.93 % (CM3) and 26.69 % (DM3) were noticed.

Likewise, for rubberized concrete containing 50% by volume of rubber aggregate, losses of

43.31 % (AM4), 54.32 % (BM4), 55.97 % (CM4) and 45.6 % (DM4) were observed. The

comparison of the results with the control concretes are shown graphically in Figure 5.6

below.

70

5.6 (a)

5.6 (b)

5.6 (c)

0.000.501.001.502.002.503.00

AM1 AM2 AM3 AM4Splitting

stren

gth (M

Pa)

Specimen

C‐15

0.00

1.00

2.00

3.00

4.00

BM1 BM2 BM3 BM4Splitting

Stren

gth(MPa

)

Specimen

C‐25

0.00

1.00

2.00

3.00

4.00

5.00

CM1 CM2 CM3 CM4

Splitting

Stren

gth (M

Pa)

Specimen

C‐30

71

5.6 (d)

Fig. 5.6 Comparisons of Splitting tensile strength Test Results .

One of the reasons that splitting tensile strength of the rubberized concrete is lower than the

conventional concrete is that bond strength between cement paste and rubber tire particles is

poor. Besides, pore structures in rubberized concretes are much more than traditional

concrete [26].

The splitting tensile strength test samples for control and rubberized concrete are shown after

testing in Figure 5.7. It can be observed that the rubberized concrete does not exhibit typical

compression failure behavior. The control concrete shows a clean split of the sample into two

halves, whereas concrete with the rubber aggregate tends to produce a less well-defined

failure.

5.7 (a) Control concrete at failure 5.7 (b) Control concrete after test

0.00

1.00

2.00

3.00

4.00

5.00

DM1 DM2 DM3 DM4

Spliting Stren

gth (M

Pa)

Specimen

C‐40

72

5.7 (c) Rubberized concrete at failure 5.7 (d) Rubberized concrete after test

Fig. 5.7 Failure patterns of Specimen during and after Splitting tensile strength tests

5.3.4 Impact Resistance Tests

Impact strength is of importance when concrete is subjected to a repeated falling object, as in

pile driving, or a single impact of a large mass at a high velocity. The principal criteria are the

ability of a specimen to withstand repeated blows and to absorb energy. Concrete made with

a gravel coarse aggregate has a low impact strength [1].

Several types of tests have been used to measure the impact resistance of concrete. These can

be classified broadly, depending upon the impacting mechanism and parameters monitored

during impact, into the following types of tests [41]:

a) Weighted pendulum charpy-type impact test

b) Drop-weight test

c) Constant strain-rate test

d) Projectile impact test

e) Split-Hopkinson bar test

f) Explosive tests

g) Instrumented pendulum impact test

In this study, the drop weight test was used.

73

5.3.4.1 Drop weight Test

The simplest of the impact tests is the repeated impact drop weight test. This test yields the

number of blows necessary to cause prescribed levels of distress in the test specimen. This

number serves as a qualitative estimate of the energy absorbed by the specimen at the levels

of distress specified.

Concrete samples are made in molds according to procedures recommended for compressive

cylinders but with an average depth of 63.5 mm and they can be sawn from full size cylinders

to yield a specimen of the proper thickness. The samples are coated on the bottom with a thin

layer of petroleum jelly or heavy grease. Then they are placed on the base plate within the

positioning lugs with the finished face up. The drop hammer is placed with its base upon the

steel ball and held there with just enough down pressure to keep it from bouncing of the ball

during the test [41].

The hammer is dropped repeatedly and the number of blows required to cause the first visible

crack on the top and to cause ultimate failure are both recorded. Ultimate failure is defined as

the opening of cracks in the specimen sufficiently so that the pieces of concrete are touching

three of the four positioning lugs on the base plate. Results of the test exhibit a high

variability and may vary considerably with the different types of mixtures [41]. Fig 5.8 below

shows a concrete sample arranged for impact resistance test in this study. And Table 5.5

shows the results of impact resistance test. The results in the table are the mean of four test

samples as shown in annex E and hence some figures show decimals in the number of blows.

Fig. 5.8 A Concrete sample arranged for Impact resistance test

74

Table 5.5 Results of Impact Resistance test.

No. Spec. Grade %

rubber

Sample height (mm)

No. of Blows Δ Increase/Decr. 1st

Crack Ultimate Failure

1st Crack

Ultimate Failure

1 AM1 C 15 0.00 64.69 17.25 21.00 0.00 0.00

2 AM2 C 15 10.00 64.31 128.50 143.25 111.25 122.25

3 AM3 C 15 25.00 65.34 181.00 197.25 163.75 176.25

4 AM4 C 15 50.00 65.04 55.00 70.75 37.75 49.75

5 BM1 C 25 0.00 65.51 59.25 69.50 0.00 0.00

6 BM2 C 25 10.00 66.19 148.75 158.75 89.50 89.25

7 BM3 C 25 25.00 64.95 186.50 203.75 127.25 134.25

8 BM4 C 25 50.00 64.83 38.00 50.75 -21.25 -18.75

9 CM1 C 30 0.00 65.85 517.00 523.50 0.00 0.00

10 CM2 C 30 10.00 63.97 599.50 618.25 82.50 94.75

11 CM3 C 30 25.00 65.50 639.75 672.25 122.75 148.75

12 CM4 C 30 50.00 63.92 103.00 132.00 -414.00 -391.50

13 DM1 C 40 0.00 64.37 654.00 676.25 0.00 0.00

14 DM2 C 40 10.00 63.83 682.00 694.75 28.00 18.50

15 CM3 C 40 25.00 64.73 629.75 647.00 -24.25 -29.25

16 DM2 C 40 50.00 64.75 118.00 140.25 -536.00 -536.00

For rubberized concrete, the results show that the addition of rubber aggregate resulted in a

significant increase in impact resistance compared with the control concrete. This increment

increased with increasing percentage of rubber aggregate for a 10 % and 25 % rubber

aggregate replacement in mixes A, B and C. In the case of mix D, a reduction in impact

resistance was noticed at 25 % replacement of the rubber aggregate. In all mixes except mix

A, the impact resistance value for a 50 % rubber aggregate replacement was lower than the

control concrete.

The test results shows that the addition of rubber aggregate to concrete at a lower percentages

of 10 and 25 % enhanced the impact resistance of the concrete greatly and hence the

application of rubberized concrete can be of great help in structures which are exposed to

vibrations and impact loads.

75

5.3.5 Flexural strength Tests

This test gives another way of estimating tensile strength of concrete. During pure bending,

the member resisting the action is subjected to internal actions or stresses (shear, tensile and

compressive). For a bending force applied downward on a member supported simply at its

two ends, fibers above the neutral axis are, generally, subjected to compressive stresses and

those below the neutral axis to tensile stresses.

For this load and support system, portions of the member near the supports are subjected to

relatively higher shear stresses than tensile stresses. In this test, the concrete member to be

tested is supported at its ends and loaded at its interior locations by a gradually increasing

load to failure. The failure load (loading value at which the concrete cracks heavily) is then

recorded and used to determine the tensile stress at which the member failed, i.e. its tensile

strength [38].

The prepared beam samples were tested after 28 days of standard curing and the results of

flexural strength tests for the control concretes and the rubberized concretes are summarized

below in Table 5.6. The calculation of the flexural stress at failure is as follows:

C =D/2 cm; M=PL/3 N.m ; I=bd3/12 m4 ; σ=Mc/I MPa .……….………….[38]

Where: P = Failure Load σ = Bending Strength

M = Maximum Moment L = Span of Specimen

I = Moment of Inertia D = Depth of specimen

C = Centroidal depth B = Width of the specimen

76

Table 5.6 Flexural Strength Test Results.

No. Spec. Grade % rubber Failure Load

(KN) Flexural Strength

(MPa) % Strength

loss

1 AM1 C 15 0.00 9.1 9.10 0.00

2 AM2 C 15 10.00 9.45 9.45 -3.85

3 AM3 C 15 25.00 5.2 5.20 42.86

4 AM4 C 15 50.00 5.7 5.70 37.36

5 BM1 C 25 0.00 11.1 11.10 0.00

6 BM2 C 25 10.00 11.35 11.35 -2.25

7 BM3 C 25 25.00 10.1 10.10 9.01

8 BM4 C 25 50.00 6 6.00 45.95

9 CM1 C 30 0.00 12.05 12.05 0.00

10 CM2 C 30 10.00 10.75 10.75 10.79

11 CM3 C 30 25.00 8.6 8.60 28.63

12 CM4 C 30 50.00 6.5 6.50 46.06

13 DM1 C 40 0.00 13.3 13.30 0.00

14 DM2 C 40 10.00 9.5 9.50 28.57

15 DM3 C 40 25.00 9.3 9.30 30.08

16 DM4 C 40 50.00 5.75 5.75 56.77

The results show that the flexural strength increased compared to the control mix for rubber

aggregate content of 10 % and for the low strength concrete classes (i.e. AM2 and BM2). In

these two categories of concretes, for rubber aggregate content of 25% and 50% a flexural

strength reduction was observed as compared to the control mix. This indicates that

improvements in flexural strength are limited to a relatively small rubber aggregate contents.

On the other part for mix C (C 30) and Mix D (C40) a reduction in flexural strength is seen in

all concrete samples containing the rubber aggregate. The observed percentage losses in mix

C are 10.79, 28.69 and 46.06 % for a rubber content of 10, 25 and 50 percents respectively.

Whereas the percentage loss in mix D was 28.57, 30.08 and 56.77 % for a rubber aggregate

content of 10, 25 and 50 percents respectively. Figure 5.9 below shows a graphical

representation of the comparison on the flexural strength of the control concretes and the

rubberized concretes.

77

5.9 (a)

5.9 (b)

5.9 (c)

0.00

2.00

4.00

6.00

8.00

10.00

AM1 AM2 AM3 AM4

Flexural Stren

gth (M

Pa)

Specimen

C‐15

0.002.004.006.008.0010.0012.00

BM1 BM2 BM3 BM4Flexural Stren

gth(MPa

)

Specimen

C‐25

0.002.004.006.008.00

10.0012.0014.00

CM1 CM2 CM3 CM4Flexural Stren

gth (M

Pa)

Specimen

C‐30

78

5.9 (d)

Fig. 5.9 Comparison of flexural strength test results

From the results obtained, it can be concluded that as the amount of rubber content increases,

the reduction in the flexural strength also increases with a concrete of medium and high

strength compressive values. Nevertheless, a good advantage of increase in flexural strength

can be achieved with a lower strength concretes C15 and C25 and by limiting the

replacement value to only 10 % of the coarse aggregate.

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

DM1 DM2 DM3 DM4

Flexural Stren

gth (M

Pa)

Specimen

C‐40

79

6. CONCLUSIONS AND RECOMMENDATIONS The general objective of this research was to evaluate the fresh and hardened properties of a

concrete produced by replacing part of the natural coarse aggregates with an aggregate

produced from locally available recycled waste tire and subjected to local conditions. From

the test results of the samples, as compared to the respective conventional concrete

properties, the following conclusions and recommendations are drawn out.

6.1 Conclusions 1. The introduction of recycled rubber tires into concrete significantly increased the slump

and workability. It was noted that the slump has increased as the percentage of rubber was

increased in all samples except DM4 which is with a targeted compressive strength of 40

MPa and a 50 % replacement of rubber aggregates for the natural coarse aggregates.

2. A reduction in unit weight of up to 24% was observed when 50% by volume of the coarse

aggregate was replaced by rubber aggregate in sample AM4 which is with a targeted

compressive strength of 15 MPa. A much similar trend of reduction in unit weight of the

rubberized concrete was observed in all the other samples containing rubber aggregates.

The low specific gravity of the rubber chips as compared to the mineral coarse aggregates

produced a decrease in the unit weight of the rubberized concrete. Crumb rubber is nearly

two and half times lighter than the conventional mineral coarse aggregate and hence it can

be expected that the mass density of the mix would be relatively lower. Rubberized

concrete can be used in non load bearing members such as lightweight concrete walls,

building facades, or other light architectural units, thus the rubberized concrete mixes

could give a viable alternative to the normal weight concrete.

3. For rubberized concrete, the test results show that the addition of rubber aggregate resulted

in a significant reduction in concrete compressive strength compared with the control

concrete. This reduction increased with increasing percentage of rubber aggregate. Losses

in compressive strength ranging from 11.38 % to 64.02 % were observed. The reason for

the strength reduction could be attributed both to a reduction of quantity of the solid load

carrying material and lack of adhesion at the boundaries of the rubber aggregate, soft

rubber particles behave as voids in the concrete matrix. Therefore, rubber aggregate tends

to behave like weak inclusions or voids in the concrete resulting in a reduction in

compressive strength. Although the compressive strength values have considerably

80

decreased with the addition of waste tire pieces, their values are still in the reasonable

range for a 10 % and 25 % replacement values because the intended compressive strengths

of 15, 25, 30 and 40 MPa were achieved in this categories.

4. The results of the splitting tensile strength tests show that, there is a decrease in strength

with increasing rubber aggregate content like the reduction observed in the compressive

strength tests. However, there was a smaller reduction in splitting tensile strength as

compared to the reduction in the compressive strength.

One of the reasons that splitting tensile strength of the rubberized concrete is lower than

the conventional concrete is that bond strength between cement paste and rubber tire

particles is poor. Besides, pore structures in rubberized concretes are much more than

conventional concrete.

5. The visual observation of the patterns of failure mode revealed that the rubberized concrete

does not exhibit typical compression failure behavior. The control concrete shows a clean

split of the sample into two halves, whereas the rubber aggregate tends to produce a less

well defined failure. Moreover, the mode of failure was a gradual type rather than the

brittle failure in the control concretes. This may be an indication more ductility in

rubberized concrete than the control concrete. However, it has to be clearly investigated by

carrying out ductility tests.

6. The Impact resistance test results show that the addition of rubber aggregate resulted in a

significant increase in impact resistance compared with the control concrete. These results

shows that the addition of rubber aggregate to concrete at a lower replacements of 10 and

25 % enhanced the impact resistance of the concrete greatly. Hence, the application of

rubberized concrete can be of great help in structures that are exposed to vibrations and

impact loads.

7. A significant advantage of increase in flexural strength was achieved in lower strength

concretes, C15 and C25, by limiting the replacement amount to only 10 % of the coarse

aggregate. In these two categories of concretes, for rubber aggregate contents of 25 and 50

% a flexural strength reduction was observed compared to the control mixes. The

reduction indicates that improvements in flexural strength are limited to relatively small

rubber aggregate contents. Since the tendency of the flexural strength test results are a bit

different from the other strength test results, this needs to be investigated through more

81

research. In general, it can be concluded that as the amount of rubber content increases,

the reduction in the flexural strength also increases

8. A reduced compressive strength of concrete due to the inclusion of rubber aggregates

limits its use in some structural applications. Nevertheless, it has few desirable

characteristics such as lower density, higher impact and toughness resistance, enhanced

ductility, and a slight increase in flexural strength in the lower strength concretes.

9. The use of rubber aggregates from recycled tires addresses many issues. These include;

reduction of the environmental threats caused by waste tires, introduction of an

alternative source to aggregates in concrete, enhancing of the weak properties of concrete

by the introduction of different ingredients other than the conventionally used natural

aggregates and ultimately leading to the conservation of natural resources. In addition to

meeting recycling and sustainability objectives, it aims is to produce products with

enhanced properties in specific applications.

10. In some applications of concrete, it is demanded that concrete should have low unit

weight, Medium strength, high toughness and high impact resistance. Although concrete

is the most commonly used construction material, it does not always fulfill these

requirements. One of the ways to improve these properties can be the addition of the

rubber into concrete as an aggregate. The overall results of this study show that it is

possible to use recycled rubber tires in concrete construction as a partial replacement for

coarse aggregates. However, the percentage replacement should be limited to specified

amounts as discussed above and the application should be restricted to particular cases

where the improved properties due to the rubber aggregates outweigh the corresponding

demerits that may occur due to them.

6.2 Recommendations

1. Even though the use of waste tires for various applications by traditional recyclers has been

a common practice in Ethiopia so far, with the increase in urbanization and the change in

the living conditions of the society, the old ways cannot continue with time. Hence, there

will be a potential accumulation of waste tires especially in the larger cities of the country.

So far, the Government has made an attempt by declaring the solid waste management

proclamation on the Negarit gazette prohibiting the import of waste tires. Moreover, the

82

country should also enforce laws regarding the management of waste tires before the

problem expands and reaches to an uncontrollable level.

2. Since the use of rubber aggregates in concrete construction is not a common trend in our

country, more studies and research works need to be done in this area and academic

institutions should play a great role.

3. Tire manufacturers and importers in the country should be aware of the environmental

consequences of waste tires and they should have research centers that promote an

environmental friendly way of tire reprocessing.

4. Most of the time, it is observed that designers and contractors go to a high strength and

expensive concrete to get few improved properties such as impact resistance in parking

areas and light weight structures for particular applications. Nevertheless, these properties

can be achieved through the application of rubberized concrete by first conducting

laboratory tests regarding the desired properties. Therefore, the use of rubberized concrete

as an alternative concrete making material needs an attention.

5. Since the long-term performance of these mixes was not investigated in the present study,

the use of such mixes is recommended in places where high strength of concrete is not as

important as the other properties.

6. Future studies should be continued in the following areas as part of the extension of this

research work.

i) In this research, a constant dosage of admixture was used for a particular mix

category. It will be more helpful if the effects of various dosages of admixtures are

investigated.

ii) The effect of using de-airing agents to decrease the entrapped air in rubberized

concrete should be studied. Consequently, a considerable increase in compressive

strength can be achieved.

iii) The existence of any chemical reactions between the rubber aggregate and other

constituents of the rubberized concrete to make sure that there is no undesirable

effects that are similar to alkali-silica and alkali-carbonate reactions in natural

aggregates needs to be investigated.

83

iv) This research was done by preparing single graded rubber aggregates of size 20 mm.

The effect of different sizes should be studied in the future. Besides to this, the

effects in different percentage replacements other than those made in this research

needs to be investigated.

v) The test results in this study are based on results taken after 7th, 28th and 56th days of

standard curing of the test samples. The long-term effects of rubberized concrete

needs to be studied to find out the relevant properties associated with the age of the

concrete.

84

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[2] Kumaran S.G., Nurdin M. and Lakshmipathy M., A Review on Construction Technologies that Enable Environmental Protection: Rubberized Concrete, USA, Science Publications, 2008.

[3] Groom R.E., Hanna J.A. and Tutu O., New Products incorporating Tire Materials, Northern Ireland: Questor Centre, 2005.

[4] Kaloush K.E, George B. W. and Han Z., Properties of Crumb Rubber Concrete, Arizona: Arizona State University, 2004.

[5] Vanessa C., Linda G., Ase H., Joanne W. And Krishna R., Use of Shredded Tires as a Lightweight Backfill Material for Retaining Structures, Chicago: University of Illinois at Chicago, 1995.

[6] Gintautas S., Audrius G. and Benjaminas C., Deformation Properties of Concrete With Rubber Waste Additives, Lithuania: Kaunas University of Technology, 2007.

[7] Prakash P., Sharma S.C. and Murthy C.S., Study of Crumb Rubber waste in Cement stabilized soil blocks, Bangalore, 2006.

[8] Chou L.H., Chun K.L., Chang J.R. and Lee M.T., Use of waste rubber as Concrete additive, Taiwan: Waste Management and Research, Vol. 25, No. 1, 2007.

[9] Olivares F.H., Barluenga G., Landa B.P., Bollati M. and Witoszek B., Fatigue behavior of Recycled tire rubber-filled concrete and Its implications in the Design of Rigid pavements, Madrid : Elsevier Ltd, 2006.

[10] Carol Carder, Rubberized concrete, Colorado: Rocky Mountain Construction, 2004.

[11] Barnet J. and Associates Ltd, Recycling and Secondary Aggregates, Dublin, 2004.

[12] Emiroglu M., Kelestemur M.H. and Yildiz S., An Investigation on ITZ Microstructure of The Concrete Containing Waste Vehicle Tire, Istanbul: Firat University, 2007.

[13] Cairns R., Kew H.Y. and Kenny M.J., The Use of Recycled Rubber Tires in Concrete Construction, Glasgow: The Onyx Environmental Trust, 2004.

[14] Sidney Mindess, Young J.F. and David Darwin, Concrete, 2nd edition, New Jersey: Prentice hall, 2003.

[15] Naik T.R. and Moriconi G., Environmental-friendly durable Concrete made with Recycled materials for Sustainable Concrete Construction, Milwaukee: University of Wisconsin, 2005.

85

[16] The Portland Cement Association, http://www.cement.org, 2009.

[Viewed 11 July 2009]

[17] ASTM International Standards, http: // www.astm.org/standards, 2009. [Viewed 04 August 2009]

[18] Meyer C., Concrete As a Green Building Material, New York, 2004.

[19] Shewaferaw Dinku, The Use of Manufactured Sand In Concrete Production: Test Results And Cost Comparison, MSc Thesis, Addis Ababa, 2006.

[20] The US Department of Transportation Federal Highway Administration, http://www.fhwa.dot.gov,2009. [Viewed 13 Sept. 2009]

[21] Tigist Getaneh, Investigation on the Potential Use of Available Materials for the Production of High Strength Structural Concrete, MSc Thesis, Addis Ababa, 2002.

[22] Wallis M.J., Sustainable Re-use of Tires in Port, Coastal and River Engineering, Seattle: HR Wallingford, 2005.

[23] Wikipedia the Free Encyclopedia, http://en.wikipedia.org, 2009 [Viewed 27 March 2009]

[24] The Rubber Manufacturers Association, http://www.rma.org, 2009 [Viewed 13 March 2009]

[25] John Stutz, Sara Donahue, Erica Mintzer, and Amy Cotter, Recycled Rubber Products in Landscaping Applications, Boston: Tellus Institute,2003.

[26] Michelle Danko, Edgar Cano and Jose Pena, Use of Recycled Tires as Partial replacement of Coarse Aggregate in the Production of Concrete, Purdue University Calumet, 2006.

[27] Paul Hallett, The Use of Post-Consumer Tires as Aggregate, London: ais, 2002.

[28] Mengistu Zerga, Yagelegelu Gomawochn meliso belela tikim lay mawal, Addis Ababa: Environmental development action-Ethiopia, 2001.

[29] Ethiopian Tire and Rubber Economy Plant P.L.C., 2009. [Brochure]

[30] Federal Negarit Gazette of the Federal Democratic Republic of Ethiopia, Solid Waste Management Proclamation, 13th year, No. 13, Addis Ababa, 2007.

[31] Naik T.R. and Rafat Siddique, Properties of Concrete Containing Scrap Tire rubber -an Overview, Milwaukee, 2002.

[32] Felipe J.A., Jeannette Santos, The Use of Recycled Polymers and Rubbers in Concrete, Florida, 2004.

86

[33] Michael Abbott, Crumb Rubber in Sport And Play, Dundee, 2001.

[34] Ling T.C. and Hasanan M.N., Properties of Crumb Rubber Concrete Paving Blocks with and without Facing Layer, Kuala lumpur, 2006.

[35] Yunping Xi, Yue Li, Zhaohui Xie, and Lee J.S., Utilization of Solid Wastes (Waste Glass and Rubber Particles) as Aggregates in Concrete, Colorado, 2003.

[36] U.S. Army Engineer Research and Development Center, Reuse Of Concrete Materials From Building Demolition, Washington DC, 2004.

[37] Kang Jingfu, Han Chuncui and Zhang Zhenli, Roller-Compacted Concrete using Tire-Rubber Additive, Tianjin,2008.

[38] Abebe Dinku, Construction Materials Laboratory Manual, Addis Ababa University Printing Press, Addis Ababa, 2002.

[39] Fosroc Product Catalogue, 2009.

[40] Abebe Dinku, DOE Method of Mix Design Process, Addis Ababa, 2008. [Lecture, AAU, Faculty of Technology, Civil Engineering Department, 2007/2008]

[41] ACI Committee 544, Measurement of Properties of Fiber Reinforced Concrete, ACI 544.2R-89.

1- Moisture Content

500 gm490 gm

2.04 %

2- Unit weight of Aggregates

4830 gm

26505 gm21675 gm

14265.12 cc

1.52 gm/cm3

3- Specific Gravity and Absorbtion Capacity

Gravimetric (Pycnometer) Procedure

500 gm479 gm

1271 gm1572 gm

water to calibration mark

Bulk Specific gravity= A/(B+500-C) = 2.41

2.51 Apparrent Specific Gravity= A/(B+A-C) 2.69 Absorption(%)= 100*(500-A)/A 4.38 %

weight original sample in air=A=weight of oven-dry sample in air (gm)=

Annex A: Material Properties

A1:Physical Properties of the Fine Aggregate

Bulk Specific gravity(SSD basis)= 500/(B+500-C)

ResultDescription

Moisture content w (%)= 100*(A-B)/B

Rodding ProcedureWeight of Measure

Weight of Measure and rodded aggregate

A- Weight of original sampleB- Weight of oven dry sample

B= weight of pycnometer filled with water=C=weight of pycnometer with sample and

Net rodded Aggregatevolume of Measure

Rodded Unit weight

87

A2: Physical Properties of the Coarse Aggregate

1- Moisture Content

A- Weight of original sample 2000 gmB- Weight of oven dry sample 1973 gm

1.37 %

2- Unit weight of Aggregates

Rodding Procedure

Weight of Measure 4830 gm

26702 gmNet rodded Aggregate 21872 gmvolume of Measure 14265.12 cc

Rodded Unit weight 1.53 gm/cc1533.25 kg/m3

3- Specific Gravity and Absorbtion Capacityof Coarse Aggregate

4944 gm5029 gm

3259.5 gm

2.79

2.84

Apparent Specific Gravity = A/(A-C) 2.93

Absorbtion Cap.(%)= 100*(B - A)/A 1.72 %

Bulk Specific Gravity(SSD basis) =B/(B-C)

ResultDescription

Moisture content w (%)= 100*(A-B)/B

Weight of Measure and rodded aggregate

A= weight of oven dry sample in airB = Weight of SSD sample in airC= weight of saturated sample in water

Bulk Specific Gravity= A/(B-C)

88

ResultDescription

4 Crushing Value of Aggregtae

The test is done on agg. that passes 12.5mm sieveand retained on 10.0mm ASTM sieve

A= the mass of surface dry sample (gm) = 2810 gmB= mass of the fraction passing 2.36mm = 501 gm

Percentage finesness = B/A 17.83 %

5 Los Angeles Abrasion Test

The Los Angeles Abrasion value is the % of finnespassing 1.18mm that gives the Abrasion resistance.

A= the mass of specimen before abrasion 5000 gmB= the mass of specimen after abrasion 4255 gm

Abrasion Value= 100*(A-B)/A 14.9 %

89

Stage ItemReference orcaculation

1SELECTION OF TARGET W/C RATIO.

1.1 Characteristic strength Specified 15 N/mm2 at 28 daysProportion defective 5%

1.2 Standard deviation (σ) N/mm2 or no data 6 N/mm2

1.3 Margin M=kσ k= 1.64 M= 9.84 N/mm2

1.4 Target mean strength fc= fck+M = 15 + 9.84 25 N/mm2

1.5 Cement Type specified OPC1.6 Aggregate type coarse crushed

fine uncrushed1.7 Free water/cement ratio 0.75 Use the lower value1.8 Maximum free water/cement ratio specified 0.55 √

2SELECTION OF FREE WATER CONTENT

2.1 Slump or V-B specified 10-30mm2.2 Max. aggregate size specified 20 mm2.3 Free-water content 170 kg/m3

3DETERMINATION OF CEMENT CONTENT

3.1 Cement content [Free water ÷(w/c)] 309 kg/m3

3.2 Maximum Cement Content specified _ kg/m3

3.3 Minimum Cement Content specified kg/m3

3.4 Modified FW/C _

4DETERMINATION OF TOTAL AGGREGATE

4.1 Relative density of aggregate (SSD) 2.66 known4.2 concrete density 2425 kg/m3

4.3 Total aggregate content 1946 kg/m3

5

SELECTION OF FINE AND COARSE AGGREGATE CONTENT

5.1 Grading of fine aggregate BS 882 Zone 25.2 Proportion of fine aggregate 30-37 % take 34 %5.3 Fine aggregate content 661.6 kg/m3 take 660 kg/m3

5.4 Coarse aggregate content 1286 kg/m3

Quantitiescement

(kg) Water (kg)

fine aggregate

(kg)per m3(to nearest 5 kg) 310 170 660.0per trial mix of 0.011m3 3.41 1.87 7.26

ANNEX B: MIX DESIGN (DOE method)B1: C-15 Trial Mix

14.13

[=concrete density - water content -cement content]

values

coarse agg. (kg)

1285

90





1.3 Margin M=kσ k= 1.64 M= 13.12 N/mm2



fine uncrushed1.7 Free water/cement ratio 0.58 Use the lower value1.8 Maximum free water/cement ratio specified 0.55 √






3.3 Minimum Cement Content specified 330 kg/m3

3.4 Modified FW/C 0.52




5




Quantitiescement

(kg) Water (kg)

fine aggregate


B2:C-25 (Trial Mix)

13.97


values

coarse agg. (kg)

1270

91





1.3 Margin M=kσ k= 1.64 M= 13.12 N/mm2



fine uncrushed1.7 Free water/cement ratio 0.52 √ Use the lower value1.8 Maximum free water/cement ratio specified 0.55











5




Quantitiescement

(kg) Water (kg)

fine aggregate


B3: C-30 (Trial Mix)

13.75


values

coarse agg. (kg)

1250

92





1.3 Margin M=kσ k= 1.64 M= 13.12 N/mm2



fine uncrushed1.7 Free water/cement ratio 0.45 √ Use the lower value1.8 Maximum free water/cement ratio specified 0.55











5




Quantitiescement

(kg) Water (kg)

fine aggregate


B4: C-40 (Trial Mix)

13.64


values

coarse agg. (kg)

1240

93





1.3 Margin M=kσ k= 1.64 M= 9.84 N/mm2



fine uncrushed1.7 Free water/cement ratio 0.75 √ Use the lower value1.8 Maximum free water/cement ratio specified _






3.3 Minimum Cement Content specified _ kg/m3

3.4 Modified FW/C




5




Quantitiescement

(kg) Water (kg)

fine aggregate

(kg)per m3(to nearest 5 kg) 230 170 690.0per a mix of 0.068 m3 15.64 11.56 46.92

B5: C-15 (Final Mix)

91.12


values

coarse agg. (kg)

1340

94





1.3 Margin M=kσ k= 1.64 M= 13.12 N/mm2










3.4 Modified FW/C




5




Quantitiescement

(kg) Water (kg)

fine aggregate



88.74


values

coarse agg. (kg)

1305

95





1.3 Margin M=kσ k= 1.64 M= 13.12 N/mm2










3.4 Modified FW/C




5




Quantitiescement

(kg) Water (kg)

fine aggregate



86.7


values

coarse agg. (kg)

1275

96





1.3 Margin M=kσ k= 1.64 M= 13.12 N/mm2










3.4 Modified FW/C




5




Quantitiescement

(kg) Water (kg)

fine aggregate



85


values

coarse agg. (kg)

1250

97

ANNEX C: Compressive Strength and Unit Weight Test ResultsC1: 7 Day Test Results

L W H

1 15.01 15.00 15.18 3,418.45 8,386.00 343.10 15.25 2.45

2 14.95 15.07 15.12 3,407.16 8,264.00 335.20 14.90 2.43

3 14.92 15.01 15.06 3,372.90 8,290.00 338.60 15.05 2.46

14.96 15.03 15.12 3,399.50 8,313.33 338.97 15.07 2.45

1 14.91 14.98 15.04 3,357.41 8,032.00 320.00 14.22 2.39

2 15.00 14.97 15.09 3,388.00 8,126.00 314.60 13.98 2.40

3 14.95 14.96 15.10 3,375.57 8,044.00 305.50 13.58 2.38

14.95 14.97 15.08 3,373.66 8,067.33 313.37 13.93 2.39

1 15.00 15.20 14.93 3,403.82 7,806.00 296.10 13.16 2.29

2 15.35 15.03 14.96 3,453.71 7,724.00 286.40 12.73 2.24

3 15.02 15.19 15.01 3,421.87 7,770.00 318.70 14.16 2.27

15.12 15.14 14.97 3,426.47 7,766.67 300.40 13.35 2.27

1 14.93 14.97 15.13 3,379.79 6,825.00 166.20 7.39 2.02

2 15.34 15.30 15.15 3,555.05 6,939.00 168.90 7.20 1.95

3 15.07 14.99 15.15 3,424.65 6,800.00 158.10 7.00 1.99

15.11 15.09 15.14 3,453.16 6,854.67 164.40 7.20 1.99

10

25

50

Mean

Mean

Volume (cm3) Failure Load [kN]

AM4 C 15

Mean

AM1 0

AM2 C 15

Mean

AM3 C 15

Comp. Strength

[Mpa]

Unit Weight [gm/cm3]

C 15

Sample No. Specimen Grade % rubber Weight (gm)Dimensions (cm)

98


L W HVolume (cm3) Failure Load

[kN]Comp.

Strength [Mpa]



1 15.19 15.05 15.09 3,450.41 8,539.00 676.80 30.08 2.47

2 15.01 15.14 15.33 3,485.36 8,550.00 645.60 28.68 2.45

3 15.33 15.33 15.20 3,569.80 8,698.00 657.30 29.22 2.44

15.17 15.17 15.21 3,501.86 8,595.67 659.90 29.33 2.45

1 15.03 15.03 15.39 3,476.63 8,177.00 528.70 23.49 2.35

2 15.02 15.00 15.05 3,390.09 8,066.00 535.80 23.81 2.38

3 15.34 15.34 15.61 3,672.33 8,651.00 575.70 25.59 2.36

15.13 15.12 15.35 3,513.02 8,298.00 546.73 24.30 2.36

1 15.01 15.01 15.01 3,381.53 7,663.00 518.10 23.00 2.27

2 15.03 15.03 15.20 3,433.71 7,914.00 517.30 22.99 2.30

3 15.01 14.97 15.16 3,406.69 7,911.00 555.10 24.67 2.32

15.02 15.00 15.12 3,407.31 7,829.33 530.17 23.55 2.30

1 15.06 15.02 15.29 3,456.77 6,926.00 263.60 11.72 2.00

2 15.00 15.00 15.34 3,451.06 7,272.00 305.90 13.60 2.11

3 15.19 15.05 15.22 3,478.52 7,034.00 251.70 11.18 2.02

15.08 15.02 15.28 3,462.12 7,077.33 273.73 12.17 2.04

0

10

25

Mean

Mean

Mean

Mean

50

BM3

BM1

BM2

BM4

C 25

C 25

C 25

C 25

99



[kN]Comp.

Strength [Mpa]



1 15.00 15.24 14.97 3,422.38 8,456.00 807.40 35.88 2.47

2 14.96 15.27 14.92 3,406.50 8,446.00 793.50 35.26 2.48

3 15.06 15.18 15.05 3,438.77 8,440.00 814.80 36.21 2.45

15.01 15.23 14.98 3,422.55 8,447.33 805.23 35.78 2.47

1 14.98 15.00 15.19 3,410.47 8,267.00 710.00 31.55 2.42

2 15.03 15.25 14.98 3,431.72 8,239.00 672.40 29.88 2.40

3 15.32 15.58 15.30 3,652.13 8,791.00 758.10 33.69 2.41

15.11 15.27 15.16 3,498.10 8,432.33 713.50 31.71 2.41

1 14.99 15.19 14.99 3,413.43 7,669.00 411.80 18.30 2.25

2 14.87 15.23 14.89 3,371.49 7,778.00 481.90 21.42 2.31

3 14.95 15.27 15.09 3,446.43 7,756.00 451.60 20.04 2.25

14.94 15.23 14.99 3,410.45 7,734.33 448.43 19.92 2.27

1 15.00 15.00 15.30 3,442.50 7,239.00 355.10 15.78 2.10

2 15.20 15.10 15.10 3,465.75 7,103.00 303.70 13.49 2.05

3 15.00 15.10 15.30 3,465.45 7,116.00 301.20 13.38 2.05

15.07 15.07 15.23 3,457.90 7,152.67 320.00 14.22 2.07

Mean

0

C 30

C 30

C 30CM4

Mean

Mean

Mean

10

CM3 25

50

CM2

CM1 C 30

100



[kN]Comp.

Strength [Mpa]



1 15.20 15.00 15.00 3,420.00 8,445.00 960.50 42.67 2.47

2 15.00 15.10 14.90 3,374.85 8,445.00 948.80 42.17 2.50

3 14.90 15.20 15.00 3,397.20 8,451.00 957.80 42.56 2.49

15.03 15.10 14.97 3,397.35 8,447.00 955.70 42.47 2.49

1 15.00 15.20 15.00 3,420.00 8,191.00 794.70 35.31 2.40

2 15.10 15.30 15.10 3,488.55 8,328.00 850.70 37.81 2.39

3 15.30 15.30 15.40 3,604.99 8,882.00 869.20 38.62 2.46

15.13 15.27 15.17 3,504.51 8,467.00 838.20 37.25 2.42

1 15.30 15.00 15.00 3,442.50 7,755.00 610.70 32.00 2.25

2 14.90 15.20 15.00 3,397.20 8,051.00 748.30 33.26 2.37

3 15.30 14.90 15.10 3,442.35 7,986.00 727.50 32.33 2.32

15.17 15.03 15.03 3,427.35 7,930.67 695.50 32.53 2.31

1 15.30 15.00 15.00 3,442.50 7,396.00 372.40 16.54 2.15

2 15.00 15.40 15.10 3,488.10 7,341.00 379.60 16.87 2.10

3 15.00 15.00 15.20 3,420.00 7,219.00 341.50 15.18 2.11

15.10 15.13 15.10 3,450.20 7,318.67 364.50 16.20 2.12

25

50

Mean

Mean

Mean

DM2 C 40

DM3 C 40

DM4 C 40

10

Mean

DM1 C 40 0

101

C: Compressive Strength and Unit weight Test ResultsC2: 28 Day Results

L W H

1 15.00 14.90 15.00 3,352.50 8,386.00 510.50 22.68 2.50

2 14.90 15.00 15.00 3,352.50 8,264.00 502.40 22.32 2.47

3 15.00 15.00 15.10 3,397.50 8,290.00 506.20 22.49 2.44

14.97 14.97 15.03 3,367.50 8,313.33 506.37 22.50 2.47

1 15.00 15.00 15.20 3,420.00 8,162.00 485.90 21.59 2.39

2 15.00 14.90 15.00 3,352.50 8,002.00 438.80 19.49 2.39

3 15.30 15.30 15.30 3,581.58 8,532.00 421.30 18.73 2.38

15.10 15.07 15.17 3,451.36 8,232.00 448.67 19.94 2.39

1 15.00 15.00 15.10 3,397.50 7,556.00 301.40 13.39 2.22

2 15.00 15.00 15.20 3,420.00 7,704.00 342.30 15.20 2.25

3 15.00 15.00 15.20 3,420.00 7,620.00 392.00 17.41 2.23

15.00 15.00 15.17 3,412.50 7,626.67 345.23 15.33 2.23

1 15.00 15.00 15.30 3,442.50 6,368.00 145.80 6.48 1.85

2 15.00 15.00 15.20 3,420.00 6,289.00 97.00 4.30 1.84

3 15.00 15.00 15.30 3,442.50 6,660.00 168.00 7.45 1.93

15.00 15.00 15.27 3,435.00 6,439.00 136.93 6.08 1.87

Comp. Strength

[Mpa]


AM1 C 15 0

Volume (cm3)Specimen Grade % rubber Dimensions (cm)

AM3 C 15 25

Weight (gm) Failure Load [kN]

Mean

AM2 C 15 10

Mean

Sample No.

Mean

AM4 C 15 50

Mean

102


L W HComp.

Strength [Mpa]


Volume (cm3)Specimen Grade % rubber Dimensions (cm) Weight (gm) Failure Load [kN]

Sample No.

1 15.20 15.20 15.00 3,465.60 8,947.00 959.20 42.63 2.58

2 14.90 15.00 15.40 3,441.90 8,484.00 911.10 40.49 2.46

3 15.00 15.00 15.10 3,397.50 8,425.00 903.70 40.16 2.48

15.03 15.07 15.17 3,435.00 8,618.67 924.67 41.09 2.51

1 15.00 15.00 15.00 3,375.00 8,134.00 792.00 35.34 2.41

2 15.00 15.00 15.20 3,420.00 8,156.00 677.30 30.09 2.38

3 15.10 15.00 15.20 3,442.80 8,480.00 849.40 37.75 2.46

15.03 15.00 15.13 3,412.60 8,256.67 772.90 34.39 2.42

1 15.00 15.00 15.10 3,397.50 7,886.00 649.10 28.88 2.32

2 15.30 15.30 15.30 3,581.58 8,244.00 661.30 29.39 2.30

3 15.00 15.00 15.00 3,375.00 7,837.00 641.20 28.50 2.32

15.10 15.10 15.13 3,451.36 7,989.00 650.53 28.92 2.31

1 15.00 15.10 15.30 3,465.45 7,030.00 352.00 15.43 2.03

2 15.10 15.00 15.30 3,465.45 7,143.00 353.10 15.69 2.06

3 15.00 15.00 15.30 3,442.50 7,007.00 297.70 13.23 2.04

15.03 15.03 15.30 3,457.80 7,060.00 334.27 14.78 2.04

BM3 C 25 25

BM1 C 25 0

Mean

BM2 C 25 10

Mean

Mean

BM4 C 25 50

Mean

103


L W HComp.

Strength [Mpa]



Sample No.

1 15.00 15.00 15.30 3,442.50 8,457.00 1,111.50 49.40 2.46

2 15.00 15.00 15.10 3,397.50 8,463.00 1,102.90 49.02 2.49

3 15.00 15.10 15.00 3,397.50 8,498.00 1,102.00 48.97 2.50

15.00 15.03 15.13 3,412.50 8,472.67 1,105.47 49.13 2.48

1 15.00 15.10 15.50 3,510.75 8,247.00 912.50 40.55 2.35

2 15.00 15.00 15.30 3,442.50 8,212.00 832.20 36.99 2.39

3 15.00 15.00 15.18 3,415.50 8,218.00 940.20 41.79 2.41

15.00 15.03 15.33 3,456.25 8,225.67 894.97 39.78 2.38

1 15.00 14.90 15.18 3,392.73 7,945.00 677.90 30.12 2.34

2 15.20 15.30 15.70 3,651.19 8,525.00 760.80 33.81 2.33

3 15.00 15.10 15.10 3,420.15 7,945.00 665.10 29.56 2.32

15.07 15.10 15.33 3,488.02 8,138.33 701.27 31.16 2.33

1 15.00 15.00 15.40 3,465.00 7,055.00 427.50 19.00 2.04

2 15.00 15.10 15.20 3,442.80 7,199.00 454.30 20.19 2.09

3 15.00 15.00 15.37 3,458.25 7,144.00 389.60 17.31 2.07

15.00 15.03 15.32 3,455.35 7,132.67 423.80 18.83 2.06

CM3 C 30 25

CM1 C 30 0

Mean

CM2 C 30 10

Mean

Mean

CM4 C 30 50

Mean

104


L W HComp.

Strength [Mpa]



Sample No.

1 15.00 15.00 15.20 3,420.00 8,532.00 1,259.55 55.98 2.49

2 15.30 15.30 15.50 3,628.40 8,988.00 1,265.40 56.24 2.48

3 15.00 15.00 15.30 3,442.50 8,535.00 1,237.73 55.01 2.48

15.10 15.10 15.33 3,496.97 8,685.00 1,254.23 55.74 2.48

1 15.30 15.30 15.50 3,628.40 8,684.00 1,066.73 47.41 2.39

2 15.00 15.00 15.20 3,420.00 8,276.00 1,065.60 47.36 2.42

3 15.00 15.00 15.30 3,442.50 8,280.00 981.45 43.62 2.41

15.10 15.10 15.33 3,496.97 8,413.33 1,037.93 46.13 2.41

1 15.00 15.00 15.00 3,375.00 7,779.00 855.00 38.00 2.30

2 15.00 15.00 15.20 3,420.00 8,037.00 877.50 39.00 2.35

3 15.00 15.00 15.10 3,397.50 7,839.00 858.38 38.15 2.31

15.00 15.00 15.10 3,397.50 7,885.00 863.63 38.38 2.32

1 15.00 15.00 15.50 3,487.50 7,379.00 503.78 22.39 2.12

2 15.00 15.00 15.50 3,487.50 7,466.00 522.00 23.20 2.14

3 15.00 15.00 15.20 3,420.00 7,268.00 508.73 22.61 2.13

15.00 15.00 15.40 3,465.00 7,371.00 511.50 22.73 2.13

DM3 C 40 25

DM1 C 40 0

Mean

DM2 C 40 10

Mean

Mean

DM4 C 40 50

Mean

105

C: Compressive Strength and Unit weight ResultsC3: 56 Day Results

L W H

1 14.96 15.03 15.14 3,403.08 8,329.00 613.90 27.28 2.45

2 14.97 14.96 15.13 3,388.16 8,408.00 659.80 29.31 2.48

3 14.98 15.05 15.25 3,438.09 8,420.00 629.80 27.99 2.45

14.97 15.01 15.17 3,409.78 8,385.67 634.50 28.19 2.46

1 14.97 14.95 15.05 3,370.24 8,191.00 589.50 26.20 2.43

2 15.31 15.02 15.13 3,477.41 8,314.00 555.90 24.70 2.39

3 14.98 15.00 15.20 3,413.63 7,962.00 567.00 25.20 2.33

15.09 14.99 15.12 3,420.43 8,155.67 570.80 25.37 2.38

1 15.00 15.00 15.40 3,465.00 7,765.00 448.60 19.93 2.24

2 15.00 15.30 15.30 3,511.35 7,767.00 450.00 20.00 2.21

3 15.00 15.00 15.30 3,442.50 7,818.00 503.90 22.40 2.27

15.00 15.10 15.33 3,472.95 7,783.33 467.50 20.78 2.24

1 15.00 15.20 15.10 3,442.80 6,869.00 369.00 16.40 2.00

2 14.90 15.20 15.50 3,510.44 7,279.00 385.90 17.15 2.07

3 15.20 15.00 15.00 3,420.00 6,714.00 360.00 16.00 1.96

15.03 15.13 15.20 3,457.75 6,954.00 371.63 16.52 2.01

Comp. Strength

[Mpa]


AM1 C 15 0


AM3 C 15 25


Mean

AM2 C 15 10

Mean

Sample No.

Mean

AM4 C 15 50

Mean

106


L W HComp.

Strength [Mpa]



Sample No.

1 14.99 15.00 15.16 3,408.05 8,508.00 987.20 43.87 2.50

2 15.26 15.30 15.35 3,583.18 8,974.00 1,079.80 47.99 2.50

3 14.97 14.99 15.09 3,385.97 8,517.00 1,080.40 48.01 2.52

15.07 15.10 15.20 3,459.07 8,666.33 1,049.13 46.62 2.51

1 14.98 14.97 15.23 3,413.08 8,235.00 870.10 38.66 2.41

2 15.03 15.00 15.21 3,428.87 8,318.00 912.80 40.57 2.43

3 14.99 14.89 15.11 3,372.79 8,193.00 929.20 41.30 2.43

15.00 14.95 15.18 3,404.91 8,248.67 904.03 40.18 2.42

1 15.30 15.30 15.60 3,651.80 8,346.00 705.80 31.35 2.29

2 15.00 15.10 15.20 3,442.80 7,817.00 736.80 32.75 2.27

3 15.00 14.90 15.30 3,419.55 7,823.00 655.80 29.14 2.29

15.10 15.10 15.37 3,504.72 7,995.33 699.47 31.08 2.28

1 14.90 15.20 15.30 3,465.14 6,979.00 407.25 18.10 2.01

2 15.30 15.30 15.40 3,604.99 7,265.00 380.25 16.90 2.02

3 15.10 15.00 15.10 3,420.15 6,980.00 427.50 19.00 2.04

15.10 15.17 15.27 3,496.76 7,074.67 405.00 18.00 2.02

BM3 C 25 25

BM1 C 25 0

Mean

BM2 C 25 10

Mean

Mean

BM4 C 25 50

Mean

107


L W HComp.

Strength [Mpa]



Sample No.

1 15.30 15.30 15.40 3,604.99 8,903.00 1,260.00 56.00 2.47

2 14.90 15.00 15.30 3,419.55 8,467.00 1,237.50 55.00 2.48

3 15.00 15.00 15.20 3,420.00 8,514.00 1,238.18 55.03 2.49

15.07 15.10 15.30 3,481.51 8,628.00 1,245.23 55.34 2.48

1 15.10 15.00 15.40 3,488.10 8,437.00 1,111.73 49.41 2.42

2 15.10 15.00 15.40 3,488.10 8,371.00 1,029.60 45.76 2.40

3 15.10 15.10 15.20 3,465.75 8,334.00 1,055.93 46.93 2.40

15.10 15.03 15.33 3,480.65 8,380.67 1,065.75 47.37 2.41

1 14.90 15.10 15.10 3,397.35 7,866.00 838.58 37.27 2.32

2 15.20 15.10 15.00 3,442.80 7,766.00 855.00 38.00 2.26

3 15.00 15.10 15.30 3,465.45 7,908.00 792.90 35.24 2.28

15.03 15.10 15.13 3,435.20 7,846.67 828.83 36.84 2.28

1 15.00 15.00 15.20 3,420.00 7,204.00 540.00 24.00 2.11

2 15.00 15.00 15.20 3,420.00 7,038.00 567.84 25.24 2.06

3 15.00 15.00 15.40 3,465.00 7,249.00 486.84 21.64 2.09

15.00 15.00 15.27 3,435.00 7,163.67 531.56 23.63 2.09

CM3 C 30 25

CM1 C 30 0

Mean

CM2 C 30 10

Mean

Mean

CM4 C 30 50

Mean

108


L W HComp.

Strength [Mpa]



Sample No.

1 15.00 15.00 15.00 3,375.00 8,522.00 1,327.50 59.00 2.53

2 15.00 15.00 15.20 3,420.00 8,449.00 1,354.50 60.20 2.47

3 15.00 15.00 15.30 3,442.50 8,566.00 1,381.50 61.40 2.49

15.00 15.00 15.17 3,412.50 8,512.33 1,354.50 60.20 2.49

1 15.00 15.00 15.20 3,420.00 8,279.00 1,172.25 52.10 2.42

2 15.00 15.00 15.30 3,442.50 8,257.00 1,165.50 51.80 2.40

3 15.00 15.00 15.30 3,442.50 8,272.00 1,131.75 50.30 2.40

15.00 15.00 15.27 3,435.00 8,269.33 1,156.50 51.40 2.41

1 15.00 15.00 15.10 3,397.50 7,792.00 1,104.75 49.10 2.29

2 15.00 15.00 15.40 3,465.00 7,806.00 1,096.88 48.75 2.25

3 15.00 15.00 15.20 3,420.00 8,085.00 1,072.97 47.69 2.36

15.00 15.00 15.23 3,427.50 7,894.33 1,091.53 48.51 2.30

1 15.00 15.00 15.40 3,465.00 7,140.00 629.72 27.99 2.06

2 15.00 15.00 15.50 3,487.50 7,243.00 652.50 29.00 2.08

3 15.00 15.00 15.40 3,465.00 7,373.00 635.91 28.26 2.13

15.00 15.00 15.43 3,472.50 7,252.00 639.38 28.42 2.09

DM3 C 40 25

DM1 C 40 0

Mean

DM2 C 40 10

Mean

Mean

DM4 C 40 50

Mean

109


L W H

1 14.96 15.03 15.14 3,403.08 8,329.00 613.90 27.28 2.45

2 14.97 14.96 15.13 3,388.16 8,408.00 659.80 29.31 2.48

3 14.98 15.05 15.25 3,438.09 8,420.00 629.80 27.99 2.45

14.97 15.01 15.17 3,409.78 8,385.67 634.50 28.19 2.46

1 14.97 14.95 15.05 3,370.24 8,191.00 589.50 26.20 2.43

2 15.31 15.02 15.13 3,477.41 8,314.00 555.90 24.70 2.39

3 14.98 15.00 15.20 3,413.63 7,962.00 567.00 25.20 2.33

15.09 14.99 15.12 3,420.43 8,155.67 570.80 25.37 2.38

1 15.00 15.00 15.40 3,465.00 7,765.00 448.60 19.93 2.24

2 15.00 15.30 15.30 3,511.35 7,767.00 450.00 20.00 2.21

3 15.00 15.00 15.30 3,442.50 7,818.00 503.90 22.40 2.27

15.00 15.10 15.33 3,472.95 7,783.33 467.50 20.78 2.24

1 15.00 15.20 15.10 3,442.80 6,869.00 369.00 16.40 2.00

2 14.90 15.20 15.50 3,510.44 7,279.00 385.90 17.15 2.07

3 15.20 15.00 15.00 3,420.00 6,714.00 360.00 16.00 1.96

15.03 15.13 15.20 3,457.75 6,954.00 371.63 16.52 2.01

Comp. Strength

[Mpa]


AM1 C 15 0


AM3 C 15 25


Mean

AM2 C 15 10

Mean

Sample No.

Mean

AM4 C 15 50

Mean

106


L W HComp.

Strength [Mpa]



Sample No.

1 14.99 15.00 15.16 3,408.05 8,508.00 987.20 43.87 2.50

2 15.26 15.30 15.35 3,583.18 8,974.00 1,079.80 47.99 2.50

3 14.97 14.99 15.09 3,385.97 8,517.00 1,080.40 48.01 2.52

15.07 15.10 15.20 3,459.07 8,666.33 1,049.13 46.62 2.51

1 14.98 14.97 15.23 3,413.08 8,235.00 870.10 38.66 2.41

2 15.03 15.00 15.21 3,428.87 8,318.00 912.80 40.57 2.43

3 14.99 14.89 15.11 3,372.79 8,193.00 929.20 41.30 2.43

15.00 14.95 15.18 3,404.91 8,248.67 904.03 40.18 2.42

1 15.30 15.30 15.60 3,651.80 8,346.00 705.80 31.35 2.29

2 15.00 15.10 15.20 3,442.80 7,817.00 736.80 32.75 2.27

3 15.00 14.90 15.30 3,419.55 7,823.00 655.80 29.14 2.29

15.10 15.10 15.37 3,504.72 7,995.33 699.47 31.08 2.28

1 14.90 15.20 15.30 3,465.14 6,979.00 407.25 18.10 2.01

2 15.30 15.30 15.40 3,604.99 7,265.00 380.25 16.90 2.02

3 15.10 15.00 15.10 3,420.15 6,980.00 427.50 19.00 2.04

15.10 15.17 15.27 3,496.76 7,074.67 405.00 18.00 2.02

BM3 C 25 25

BM1 C 25 0

Mean

BM2 C 25 10

Mean

Mean

BM4 C 25 50

Mean

107


L W HComp.

Strength [Mpa]



Sample No.

1 15.30 15.30 15.40 3,604.99 8,903.00 1,260.00 56.00 2.47

2 14.90 15.00 15.30 3,419.55 8,467.00 1,237.50 55.00 2.48

3 15.00 15.00 15.20 3,420.00 8,514.00 1,238.18 55.03 2.49

15.07 15.10 15.30 3,481.51 8,628.00 1,245.23 55.34 2.48

1 15.10 15.00 15.40 3,488.10 8,437.00 1,111.73 49.41 2.42

2 15.10 15.00 15.40 3,488.10 8,371.00 1,029.60 45.76 2.40

3 15.10 15.10 15.20 3,465.75 8,334.00 1,055.93 46.93 2.40

15.10 15.03 15.33 3,480.65 8,380.67 1,065.75 47.37 2.41

1 14.90 15.10 15.10 3,397.35 7,866.00 838.58 37.27 2.32

2 15.20 15.10 15.00 3,442.80 7,766.00 855.00 38.00 2.26

3 15.00 15.10 15.30 3,465.45 7,908.00 792.90 35.24 2.28

15.03 15.10 15.13 3,435.20 7,846.67 828.83 36.84 2.28

1 15.00 15.00 15.20 3,420.00 7,204.00 540.00 24.00 2.11

2 15.00 15.00 15.20 3,420.00 7,038.00 567.84 25.24 2.06

3 15.00 15.00 15.40 3,465.00 7,249.00 486.84 21.64 2.09

15.00 15.00 15.27 3,435.00 7,163.67 531.56 23.63 2.09

CM3 C 30 25

CM1 C 30 0

Mean

CM2 C 30 10

Mean

Mean

CM4 C 30 50

Mean

108


L W HComp.

Strength [Mpa]



Sample No.

1 15.00 15.00 15.00 3,375.00 8,522.00 1,327.50 59.00 2.53

2 15.00 15.00 15.20 3,420.00 8,449.00 1,354.50 60.20 2.47

3 15.00 15.00 15.30 3,442.50 8,566.00 1,381.50 61.40 2.49

15.00 15.00 15.17 3,412.50 8,512.33 1,354.50 60.20 2.49

1 15.00 15.00 15.20 3,420.00 8,279.00 1,172.25 52.10 2.42

2 15.00 15.00 15.30 3,442.50 8,257.00 1,165.50 51.80 2.40

3 15.00 15.00 15.30 3,442.50 8,272.00 1,131.75 50.30 2.40

15.00 15.00 15.27 3,435.00 8,269.33 1,156.50 51.40 2.41

1 15.00 15.00 15.10 3,397.50 7,792.00 1,104.75 49.10 2.29

2 15.00 15.00 15.40 3,465.00 7,806.00 1,096.88 48.75 2.25

3 15.00 15.00 15.20 3,420.00 8,085.00 1,072.97 47.69 2.36

15.00 15.00 15.23 3,427.50 7,894.33 1,091.53 48.51 2.30

1 15.00 15.00 15.40 3,465.00 7,140.00 629.72 27.99 2.06

2 15.00 15.00 15.50 3,487.50 7,243.00 652.50 29.00 2.08

3 15.00 15.00 15.40 3,465.00 7,373.00 635.91 28.26 2.13

15.00 15.00 15.43 3,472.50 7,252.00 639.38 28.42 2.09

DM3 C 40 25

DM1 C 40 0

Mean

DM2 C 40 10

Mean

Mean

DM4 C 40 50

Mean

109

ANNEX D: Splitting Tensile Strength Test Results

1 188.30 2.66

2 155.70 2.20

172.00 2.43

1 143.50 2.03

2 136.40 1.93

139.95 1.98

1 124.30 1.76

2 129.50 1.83

126.90 1.80

1 96.20 1.36

2 98.80 1.40

97.50 1.38

1 247.10 3.50

2 238.70 3.38

242.90 3.44

1 197.50 2.79

2 182.10 2.58

189.80 2.69

Mean

AM4 C 15 50

Mean

BM1 C 25 0

Mean

BM2 C 25 10

Mean

Failure Load [kN] Splitting Strength

[σt=2P/πLD] (MPa)

AM1 C 15 0

Sample No. Specimen Grade % rubber

AM3 C 15 25

Mean

AM2 C 15 10

Mean

110



[σt=2P/πLD] (MPa)


1 147.70 2.09

2 190.20 2.69

168.95 2.39

1 100.00 1.41

2 121.90 1.72

110.95 1.57

1 263.20 3.72

2 286.00 4.05

274.60 3.88

1 230.80 3.27

2 212.80 3.01

221.80 3.14

1 133.30 1.89

2 136.20 1.93

134.75 1.91

1 114.40 1.62

2 127.40 1.80

120.90 1.71

Mean

CM4 C 30 50

Mean

CM3 C 30 25

Mean

BM4 C 25 50

Mean

CM1 C 30 0

Mean

CM2 C 30 10

Mean

BM3 C 25 25

111



[σt=2P/πLD] (MPa)


1 266.40 3.77

2 247.60 3.50

257.00 3.64

1 271.50 3.84

2 285.20 4.03

278.35 3.94

1 185.40 2.62

2 191.40 2.71

188.40 2.67

1 144.20 2.04

2 135.40 1.92

139.80 1.98

Mean

DM4 C 40 50

Mean

DM3 C 40 25

DM1 C 40 0

Mean

DM2 C 40 10

Mean

112

ANNEX E: Impact Resistance Test Results

Sample height (mm) 1st Crack Ultimate Failure

1 AM1 C 15 0.00 1 64.28 15.00 18.00

2 64.91 15.00 19.00

3 65.03 27.00 31.00

4 64.53 12.00 16.00

64.69 17.25 21.00

2 AM2 C 15 10.00 1 64.23 110.00 121.00

2 64.89 141.00 147.00

3 64.31 134.00 139.00

4 63.80 129.00 166.00

64.31 128.50 143.25

3 AM3 C 15 25.00 1 65.58 203.00 215.00

2 66.26 191.00 220.00

3 65.30 160.00 171.00

4 64.21 170.00 183.00

65.34 181.00 197.25

4 AM4 C 15 50.00 1 66.01 58.00 141.00

2 66.11 66.00 77.00

3 63.24 62.00 23.00

4 64.79 34.00 42.00

65.04 55.00 70.75

5 BM1 C 25 0.00 1 66.13 77.00 86.00

2 65.38 54.00 61.00

3 65.57 60.00 76.00

4 64.94 46.00 55.00

65.51 59.25 69.50

5 BM2 C 25 10.00 1 66.00 138.00 146.00

2 68.18 190.00 196.00

3 65.35 127.00 146.00

4 65.23 140.00 147.00

66.19 148.75 158.75

Specimen Grade Sample No.% rubber

Mean

Mean

No. of Blows

Mean

Mean

Mean

Mean

No.

113




No. of Blows

No.

8 BM3 C 25 25.00 1 62.33 170.00 190.00

2 66.23 160.00 193.00

3 65.79 220.00 230.00

4 65.44 196.00 202.00

64.95 186.50 203.75

8 BM4 C 25 50.00 1 65.30 40.00 48.00

2 66.00 32.00 40.00

3 63.62 43.00 66.00

4 64.38 37.00 49.00

64.83 38.00 50.75

8 CM1 C 30 0.00 1 66.66 680.00 685.00

2 66.71 414.00 417.00

3 65.32 554.00 568.00

4 64.72 420.00 424.00

65.85 517.00 523.50

8 CM2 C 30 10.00 1 62.78 580.00 630.00

2 65.17 674.00 681.00

3 64.49 549.00 560.00

4 63.43 595.00 602.00

63.97 599.50 618.25

8 CM3 C 30 25.00 1 66.64 650.00 690.00

2 66.25 615.00 641.00

3 65.40 680.00 734.00

4 63.70 614.00 624.00

65.50 639.75 672.25

8 CM4 C 30 50.00 1 65.39 100.00 146.00

2 63.65 150.00 181.00

3 63.11 92.00 110.00

4 63.51 70.00 91.00

63.92 103.00 132.00

Mean

Mean

Mean

Mean

Mean

Mean

114




No. of Blows

No.

8 DM1 C 40 0.00 1 63.71 674.00 687.00

2 64.21 681.00 684.00

3 64.38 622.00 664.00

4 65.18 639.00 670.00

64.37 654.00 676.25

8 DM2 C 40 10.00 1 64.34 630.00 644.00

2 64.13 689.00 706.00

3 63.66 676.00 685.00

4 63.18 733.00 744.00

63.83 682.00 694.75

11 CM3 C 40 25.00 1 64.72 636.00 648.00

2 66.25 639.00 658.00

3 64.13 629.00 645.00

4 63.80 615.00 637.00

64.73 629.75 647.00

14 DM2 C 40 50.00 1 64.99 130.00 146.00

2 63.46 119.00 144.00

3 65.21 111.00 136.00

4 65.34 112.00 135.00

64.75 118.00 140.25Mean

Mean

Mean

Mean

115

ANNEX F: Flexural Strength Test Results

L B D

150 10 10

10.50 1,750.00 8.3333E-06 5.00 10.50

250 10 10

7.70 1,283.33 8.3333E-06 5.00 7.70

50 10 109.10 1,516.67 8.3333E-06 5.00 9.10

150 10 10

8.30 1,383.33 8.3333E-06 5.00 8.30

250 10 10

10.60 1,766.67 8.3333E-06 5.00 10.60

50 10 109.45 1,575.00 8.3333E-06 5.00 9.45

150 10 10

6.70 1,116.67 8.3333E-06 5.00 6.70

250 10 10

3.70 616.67 8.3333E-06 5.00 3.70

50 10 105.20 866.67 8.3333E-06 5.00 5.20

150 10 10

6.30 1,050.00 8.3333E-06 5.00 6.30

250 10 10

5.10 850.00 8.3333E-06 5.00 5.10

50 10 105.70 950.00 8.3333E-06 5.00 5.70

150 10 10

11.10 1,850.00 8.3333E-06 5.00 11.10

250 10 10

11.10 1,850.00 8.3333E-06 5.00 11.10

50 10 1011.10 1,850.00 8.3333E-06 5.00 11.10

150 10 10

11.80 1,966.67 8.3333E-06 5.00 11.80

250 10 10

10.90 1,816.67 8.3333E-06 5.00 10.90

50 10 1011.35 1,891.67 8.3333E-06 5.00 11.35

σ [Mpa]Sample

No. Specimen Grade % rubber P [kN]

AM4 C 15 50

AM1 C 15 0

Mean

AM2 C 15 10

Mean

AM3 C 15 25

Mean

Mean

BM1 C 25 0

Mean

BM2 C 25 10

Mean

Dimensions (cm)

M [N.m] I [m4] C [cm]

116


L B D σ [Mpa]Sample


Dimensions (cm)

M [N.m] I [m4] C [cm]

150 10 10

10.50 1,750.00 8.3333E-06 5.00 10.50

250 10 10

9.70 1,616.67 8.3333E-06 5.00 9.70

50 10 1010.10 1,683.33 8.3333E-06 5.00 10.10

150 10 10

6.90 1,150.00 8.3333E-06 5.00 6.90

250 10 10

5.10 850.00 8.3333E-06 5.00 5.10

50 10 106.00 1,000.00 8.3333E-06 5.00 6.00

150 10 10

12.00 2,000.00 8.3333E-06 5.00 12.00

250 10 10

12.10 2,016.67 8.3333E-06 5.00 12.10

50 10 1012.05 2,008.33 8.3333E-06 5.00 12.05

150 10 10

10.70 1,783.33 8.3333E-06 5.00 10.70

250 10 10

10.80 1,800.00 8.3333E-06 5.00 10.80

50 10 1010.75 1,791.67 8.3333E-06 5.00 10.75

150 10 10

8.60 1,433.33 8.3333E-06 5.00 8.60

250 10 10

8.60 1,433.33 8.3333E-06 5.00 8.60

50 10 108.60 1,433.33 8.3333E-06 5.00 8.60

150 10 10

5.70 950.00 8.3333E-06 5.00 5.70

250 10 10

7.30 1,216.67 8.3333E-06 5.00 7.30

50 10 106.50 1,083.33 8.3333E-06 5.00 6.50

BM4 C 25 50

BM3 C 25 25

Mean

CM4 C 30 50

Mean

CM1 C 30 0

Mean

CM2 C 30 10

Mean

CM3 C 30 25

Mean

Mean

117


L B D σ [Mpa]Sample


Dimensions (cm)

M [N.m] I [m4] C [cm]

150 10 10

12.50 2,083.33 8.3333E-06 5.00 12.50

250 10 10

14.10 2,350.00 8.3333E-06 5.00 14.10

50 10 1013.30 2,216.67 8.3333E-06 5.00 13.30

150 10 10

7.30 1,216.67 8.3333E-06 5.00 7.30

250 10 10

11.70 1,950.00 8.3333E-06 5.00 11.70

50 10 109.50 1,583.33 8.3333E-06 5.00 9.50

150 10 10

9.30 1,550.00 8.3333E-06 5.00 9.30

250 10 10

9.30 1,550.00 8.3333E-06 5.00 9.30

50 10 109.30 1,550.00 8.3333E-06 5.00 9.30

150 10 10

5.00 833.33 8.3333E-06 5.00 5.00

250 10 10

6.50 1,083.33 8.3333E-06 5.00 6.50

50 10 105.75 958.33 8.3333E-06 5.00 5.75

0

Mean

DM2 C 40 10

Mean

Mean

DM3 C 40 25

Mean

DM4 C 40 50

DM1 C 40

118

119

ANNEX G: Photos

Waste medium truck tires

Shredding of tires

Manual cutting of the shredded tires into small sizes to form rubber aggregate

120

Samples of rubber aggregate

Washing of rubber aggregate to remove impurities and then surface drying

Surface Coating of the rubber aggregate

Rubber aggregate coated with cement paste

121

A concrete mix which is ready for casting

Slump Test

Specimen preparation using molds

Mechanical vibration using a table vibrator and Compressive strength test

122

Splitting tensile strength test

Failure patterns of control concrete after splitting tensile strength test

123

Failure patterns of rubberized concrete after splitting tensile strength test

Immpact Resistaance testing a

Flexu

124

apparatus an

ural Strength

nd Test samp

h Test

ple after failuure

125

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 Abrham Kebede Seyfu

Signature …………………

Place Addis Ababa University, School of Graduate Studies, Faculty

of Technology, Department of Civil Engineering, Addis Ababa

Date of submission June 2010

abrham_kebede

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