Acknowledgment

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Acknowledgment

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

my supervisor Dr Muhammad Ali. He provided me with a lot of expert guidance,

valid comments, suggestions and 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 also very grateful to Dr Stephanie Barnett for her valuable suggestion

regarding this project work and for her grateful help in many topics.

I am so thankful to the University of Portsmouth, School of Civil Engineering

and Surveying (SCES) for providing me the platform to undergo my postgraduate

studies and for delivering the financial support required for this dissertation. My

Special thanks go to Mr Andrew Brooks, Mr Martin Colvill and their colleagues in the

concrete test laboratory for their cooperation and assistance while carrying out the

various tests.

I would also like to thank 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 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.

Contents

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Contents

ACKNOWLEDGMENT ............................................................................................... I

CONTENTS .............................................................................................................. II

LIST OF FIGURES .................................................................................................... IV

LIST OF TABLES ...................................................................................................... VI

ABSTRACT ............................................................................................................ VII

CHAPTER 1: INTRODUCTION ............................................................................... 1

1.1 Background ......................................................................................... 1

1.2 Aims and Objectives ............................................................................ 2

1.3 Scope of work ...................................................................................... 2

CHAPTER 2: LITERATURE REVIEW ........................................................................ 4

2.1 Classification of scrap tires .................................................................. 4

2.2 Characteristic Properties of rubberised concrete ................................. 4

2.2.1 Specific weight ................................................................................... 4

2.2.2 Workability ......................................................................................... 5

2.2.3 Durability ............................................................................................ 7

2.2.4 Water absorption ............................................................................... 7

2.2.5 Toughness and impact resistance ...................................................... 8

2.2.6 Freeze - thaw protection .................................................................... 8

2.3 Mechanical Strength - Properties ......................................................... 8

2.3.1 Rubber Content and Particle Size ...................................................... 9

2.3.2 Surface Texture .................................................................................. 9

2.3.3 Effect of Using Special Cements....................................................... 11

2.3.4 Strength ............................................................................................ 12

2.3.5 Stress-strain relationship ................................................................. 13

2.4 Civil Engineering Applications of Rubberized Concrete .......................14

2.4.1 Pavement Applications .................................................................... 14

2.4.2 Geotechnical Applications ............................................................... 15

2.4.3 Concrete Blocks ................................................................................ 15

2.4.4 Other Applications ........................................................................... 15

2.5 Conclusion ..........................................................................................16

CHAPTER 3: METHODOLOGY ..............................................................................17

3.1 Materials ............................................................................................18

3.1.1 Cement ............................................................................................. 18

3.1.2 Aggregates ....................................................................................... 19

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3.1.3 Measurement of the specific weight ............................................... 20

3.2 Sieve Analysis .....................................................................................21

3.3 Concrete Mix Design ...........................................................................22

3.4 Slump Test Procedure .........................................................................24

3.5 Machinery and Equipment .................................................................25

3.5.1 Digital Balance:................................................................................. 25

3.5.2 Moulds ............................................................................................. 26

3.5.3 Pan Mixer Machine .......................................................................... 26

3.5.4 Table Vibrator .................................................................................. 27

3.5.5 Water Tank ....................................................................................... 27

3.5.6 Compressive Test Machine .............................................................. 27

3.5.7 Milling Machine ............................................................................... 28

3.5.8 Elastic Young’s Modulus and Flexural Strength Test Machine ........ 29

3.5.9 Ultrasonic Pulse Velocity (UPV Pundit) ............................................ 30

3.5.10 Schmidt hammer .......................................................................... 30

CHAPTER 4: RESULTS AND DISCUSSION ..............................................................32

4.1 Fresh Concrete ...................................................................................32

4.1.1 Workability (Slump Test).................................................................. 32

4.2 Hardened Concrete.............................................................................33

4.2.1 Water absorption ............................................................................. 33

4.2.2 Compressive Strength ...................................................................... 34

4.2.3 Flexural Strength .............................................................................. 37

4.2.4 Elastic Young’s Modulus Test ........................................................... 39

4.2.5 Compressive Strength of Cylinders after the Elastic Modulus Test . 41

4.2.6 Ultrasonic Pulse Velocity .................................................................. 41

4.2.7 Rebound Hammer Test .................................................................... 43

CHAPTER 5: CONCLUSION AND RECOMMENDATIONS ........................................45

5.1 Conclusion ..........................................................................................45

5.2 Recommendations..............................................................................47

REFERENCES ..........................................................................................................48

APPENDIX .............................................................................................................50

List of figures

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List of figures

Figure 1: Graph of workability (Retrieved from Khatib & Bayomy, 1999, p. 208). ....... 6

Figure 2: Average slump test results for each rubber percentage (Retrieved from Mavroulidou & Figueiredo, 2010, p. 361). ..................................................................... 7

Figure 3: Effect of washing rubber particles with water on compressive strength of rubcrete mixtures (Retrieved from Tanatala, Lepore, & Zandi, 1996, p. 3). ............... 10

Figure 4: Rubber aggregate coated with cement paste (Retrieved from Cairns, Kew, & Kenny, 2004, p. 31). ..................................................................................................... 10

Figure 5: Effect of cement type on compressive strength (Retrieved from Beil and Lee, 1996). .................................................................................................................... 11

Figure 6: Effect of cement type on split tensile strength (Retrieved from Beil and Lee, 1996). ........................................................................................................................... 12

Figure 7: Comparison between strength reduction and rubber content (Retrieved from Batayneh, Iqbal, & Ibrahim, 2008, p. 2174). ....................................................... 12

Figure 8: Compressive Strength results (Retrieved from Khatib & Bayomy, 1999, p. 209) .............................................................................................................................. 13

Figure 9: Relationship between stress and strain for different rubber contents (Retrieved from Batayneh, Iqbal, & Ibrahim, 2008, p. 2175). ..................................... 14

Figure 10: Snowcrete cement by Lafrage. ................................................................... 18

Figure 11: Coarse aggregate 20mm (left) and 10mm (right). ...................................... 19

Figure 12: Sand. ............................................................................................................ 19

Figure 13: Chipped Rubber (left), crumb rubber (right). ............................................. 20

Figure 14: Chipped rubber soaked in cement paste. ................................................... 20

Figure 15: Specific Weight measurement. ................................................................... 21

Figure 16: Sieve Analysis of the limestone aggregates. ............................................... 22

Figure 17: Bad distribution of chipped rubber during vibrating process. ................... 24

Figure 18: Slump test cone mould. .............................................................................. 24

Figure 19: Forms of slumps. ......................................................................................... 25

Figure 20: Digital Balance............................................................................................. 25

Figure 21: Metal Moulds. ............................................................................................. 26

Figure 22: Pan mixer machine. .................................................................................... 26

Figure 23: Vibrating table............................................................................................. 27

Figure 24: Water Tank. ................................................................................................. 27

Figure 25: Compressive Strength Machine. ................................................................. 28

Figure 26: Milling Machine. ......................................................................................... 28

Figure 27: Chipped rubber protrusion. ........................................................................ 28

List of figures

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Figure 28: Elastic Young’s Modulus and Flexural Strength Test Machine. .................. 29

Figure 29: Elastic Modulus Testing Apparatus. ............................................................ 30

Figure 30: Pundit. ......................................................................................................... 30

Figure 31: Rebound hammer chart. ............................................................................. 31

Figure 32: Schmidt hammer. ........................................................................................ 31

Figure 33: Slump forms. ............................................................................................... 32

Figure 34: The samples after the removal from the water. ........................................ 33

Figure 35: Cubes’ water absorption. ............................................................................ 34

Figure 36: Compressive Strength Chart. ...................................................................... 35

Figure 37: Cubes’ failure (Mix 1, 2, 3, 4, 5 in row). ...................................................... 36

Figure 38: Compressive Strength Comparison. ........................................................... 37

Figure 39: Brazilian Test. .............................................................................................. 38

Figure 40: Flexural Strength Chart. .............................................................................. 39

Figure 41: Non-totally damaged beam. ....................................................................... 39

Figure 42: Elastic Young's Modulus Chart. ................................................................... 40

Figure 43: Cylinders’ failure in Elastic Young’s Modulus Test Procedure. ................... 41

Figure 44: Cylinders’ Compressive Strength ................................................................ 41

Figure 45: Mass into water weighting. ........................................................................ 42

Figure 46: UPV Chart. ................................................................................................... 43

Figure 47: Relationship between standard deviation and characteristic strength (Retrieved from Teychenné, Franklin, & Erntroy, 1997, p. 16).................................... 50

Figure 48: Relationship between compressive strength and free-water/ cement ratio (Retrieved from Teychenné, Franklin, & Erntroy, 1997, p. 16).................................... 51

Figure 49: Approximate compressive strength (N/mm2) of concrete mixes made with a free-water/cement ratio of 0.5 (Retrieved from Teychenné, Franklin, & Erntroy, 1997, p. 17). ................................................................................................................. 51

Figure 50: Approximate free-water contents (kg/m3) required to give various levels of workability (Retrieved from Teychenné, Franklin, & Erntroy, 1997, p. 17). ........... 52

Figure 51: Estimated wet density of fully compacted concrete (Retrieved from Teychenné, Franklin, & Erntroy, 1997, p. 18). ............................................................. 52

Figure 52: Recommended proportions of fine aggregate according to percentage passing a 600 μm sieve (Retrieved from Teychenné, Franklin, & Erntroy, 1997, p. 18). ...................................................................................................................................... 52

List of Tables

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List of Tables

Table 1: Rubber categories according it size (Retrieved from Oikonomou & Mavridou, 2009, p. 215). ................................................................................................................. 4

Table 2: Mix proportion of rubber concrete (Retrieved from Batayneh, Iqbal, & Ibrahim, 2008, p. 2173). ................................................................................................. 5

Table 3: Workability test results (Retrieved from Cairns, Kew, & Kenny, 2004, p. 16). 6

Table 4: Concrete Mix Description. .............................................................................. 17

Table 5: Labels of samples. .......................................................................................... 17

Table 6: Typical Properties of snowcrete Portland cement (Retrieved from Lafarge, 2012). ........................................................................................................................... 18

Table 7: Specific weight calculations of aggregate using Archimedes’ method. ......... 21

Table 8: Mix design portions (kg/m3). .......................................................................... 23

Table 9: Mix design quantities (kg) based on specimens’ total volume. ..................... 23

Table 10: Slump Test Results. ...................................................................................... 32

Table 11: Rebound Hammer Test Results. ................................................................... 44

Table 12: Concrete mix design form (Retrieved from Teychenné, Franklin, & Erntroy, 1997, p. 15). ................................................................................................................. 50

Table 13: Sieve Analysis. .............................................................................................. 53

Table 14: Water Absorption for Cubes. ....................................................................... 53

Table 15: Water Absorption for Cylinders. .................................................................. 54

Table 16: Water Absorption for Beams. ...................................................................... 54

Table 17: Cubes’ Compressive Strength. ..................................................................... 55

Table 18: Flexural Strength Results.............................................................................. 55

Table 19: Results of elastic young’s modulus test. ...................................................... 56

Table 20: Density of Cubes. .......................................................................................... 56

Table 21: Cylinders’ compressive Strength after elastic young’s modulus test. ......... 57

Table 22: UPV Results. ................................................................................................. 57

Abstract

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Abstract

Waste rubber tires are accumulated worldwide in large amounts into landfills

causing an increasing hazard to the environment. In order to eliminate this serious

environmental threat there is a keen interest in the recycling or reclaiming of these

solid wastes. Last three decades many researches have been done investigating the

potentials of these wasted rubber tires to be used in civil engineering works. There are

many prospects on these wastes as far as the civil engineering industry is concerned,

one such example is the use of mixture of rubber obtained from waste tires in

concrete. It has been proven to enhance properties and helps natural resources to be

conserved as well as to reduce the environmental threat due to these depositions.

Additionally, rubber tire utilisation could have also economic benefits mainly because

a waste material costs less than a virgin material. However, the sustainable

development in this industry is not very popular and investigation into the re-use of

rubber tire material needs more work.

The main purpose of this research is to investigate the potential of rubberised

concrete to be used in structural applications as structural concrete. It is widely

acceptable that the rubber in concrete reduces the strength. Nevertheless, it should be

analysed how much the rubber affects the main properties of concrete in small

percentage of substitution especially the compressive strength.

Through the experimental procedure the basic properties of rubberised concrete

are analysed carrying out conclusions on how these properties could be negative or

positive for future potential applications.

Furthermore, on this research are contacted comparisons on the experiments

results with other relevant works that have been done currently.

Introduction

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Chapter 1: Introduction

1.1 Background

Major environmental problems are increasing throughout the time leading the

government of United Kingdom to take measures in order to reduce these problems.

Thus, the solid waste management is one of the major environmental concerns

worldwide.

One of the major waste management problems in the UK is the disposal of waste

tires coming from millions of cars and trucks. According to research of Cairns, Kew,

& Kenny in 2004 (p. 5) , it is estimated that 37 million car and truck tires are being

discarded annually and this number is set to increase, in line with the growth in road

traffic and car ownership, by a further 39% by 2011 and 63% by 2021. At present, it

is thought that 11% of post-consumer tires are exported, 62% are reused, recycled or

sent for energy recovery and 27% are sent to landfill (shredded tire), stockpiled

(whole tire) or dumped in illegal tire dumps.

However, the rubber tires are not a biodegradable material and last many years

thus they remain in landfills causing a serious threat to the environment. The rubber

tires contain large quantities of oxygen in their particles, which is possible to cause

fire in appropriate conditions due to inflammable components causing damages either

to human health and atmosphere pollution (Oikonomou & Mavridou, 2009, p. 214).

A well-known example is that of Heyope in Powys, Wales, where the largest

landfill site in Britain for such scrap tires was located (this held over 9,000,000 tires).

In 1989 an intense fire took hold deep inside the mass of scrap tires and had

subsequently been burning for eleven years. This caused extensive pollution to the

atmosphere and the local water system (Mavroulidou & Figueiredo, 2010, p. 359).

Additionally, rubber tires accumulation into landfill provides the best conditions

for mosquitos breeding causing a further significant problem on human health (Nehdi

& Khan, 2001, p. 3). These are the major reasons that the European Union has

adopted laws to prevent the disposal of tires in to landfill sites in order to give

motivations to member countries to identify new recycling methods of this material.

There are a few potential recycling ways for the rubber tires and the largest route

is in civil engineering industry. However, the usage of this material at this sector is

Introduction

P a g e | 2

currently very low. This is due to the lack of high volume applications and products

involving recycled tires, as it is a material under investigation and not too widespread

until today. Currently only 4.5% of rubber tires are recycled in civil engineering

applications. Most of these tires are used in small scale applications in single projects.

However, considering the enormous number of £1.8 billion that is spent annually only

in the United Kingdom on concrete products, it is easily understandable that this is a

very potential market for this material. (Cairns, Kew, & Kenny, 2004, p. 6).

1.2 Aims and Objectives

The main aim of the research is to investigate the viability of re-use of shredded

rubber tires as a replacement material in concrete.

The specific points that this research aims are as follow:

How the rubber in concrete in small percentage of replacement affect the

main properties of it.

Investigation of the influences of different sizes of shredded rubber tires

into concrete.

To investigate the main structural properties of rubberised concrete.

To observe changes on properties of pre-treatment rubber aggregate.

To find potential ways to improve some of the major properties of

rubberised concrete.

To investigate potential applications in civil engineering market.

1.3 Scope of work

All methods were conducted according to the British Standards and all machinery

and equipment that were used are described on the relevant chapter with every detail.

The programme of work undertaken is summarised below:

Basic Properties of rubber and limestone aggregate:

Sieve analysis for all aggregates.

Evaluation of specific weight for each material that was used.

Fresh rubberised concrete characteristics:

Mix design,

Workability,

The workability is measured through the slump values of the samples.

Introduction

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Hardened rubberised concrete characteristics:

The following tests were carried out to establish some of the main properties of

concrete that most people are concerned:

Water absorption,

Compressive Strength,

Flexural Strength,

Elastic Young’s Modulus Test,

Compressive strength after the Elastic Young’s Modulus Test,

Ultrasonic Pulse Velocity,

Rebound Hammer,

Literature Review

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Chapter 2: Literature Review

2.1 Classification of scrap tires

Rubber from vehicles tires, after being shredded into smaller pieces, can often be

reused in civil engineering applications, mainly using either as aggregate and sand

substituent in concrete. Two main methods are used to grind tires to the required size:

the first method is related to ambient size reduction using mechanical processes at or

above room temperature and the second method is related to cryogenic size reduction

by the use of liquid nitrogen or commercial agents to reduce the tire to the desired

size. The first process produces rubber chips with a rough surface, while cryogenic

grinding is generally used for the production of rubber in the form of powder. By

reducing the particle size of worn tires, separation of steel wires and textile fibres can

be achieved as well as a further treatment of the worn tires so that commercial particle

sizes are created. Scrap tires are shredded for use in various applications, with the

actual size, ranging from >300 mm to <500 µm, depending upon the intended use

(Oikonomou & Mavridou, 2009, p. 215).

Table 1: Rubber categories according it size.

Characterization Size

Cuts >300 mm

Shred 50–300 mm

Chips 10–50 mm

Granulate 1–10 mm

Powder <1 mm

Fine powder <500 µm

2.2 Characteristic Properties of rubberised concrete

2.2.1 Specific weight

The natural aggregates in traditional concrete present a higher specific weight

than rubber aggregates. As a result, the specific weight of a rubberized concrete

strongly depends on the percentage of rubber content into the concrete. Thus,

increasing the content of rubber, the specific weight is decreased and vice versa (Ling,

Nor, & Lim, 2010, p. 40). However, Nehdi & Khan in 2001 (p. 4) stated that this

decrease is almost negligible for rubber contents lower than 10 to 20% of the total

aggregate volume.

Literature Review

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Moreover, the experiment of Ling, Nor, & Lim in 2010 (p. 40) shows that

increasing the rubber content, the air content is increased respectively.

Table 2 illustrates the results of the experiment that has been done by Batayneh,

Iqbal, & Ibrahim in 2008 (p. 2173) showing the unit weight of concrete for various

rubber contents (for all cases water content is 252 Kg/m3, cement content is 446

Kg/m3 and coarse aggregate is 961 Kg/m

3).

Table 2: Mix proportion of rubber concrete.

Crumb rubber

content (%)

Fine Aggregates

(Kg/m3)

Rubber

(Kg/m3)

Unit Weight

(Kg/m3)

0 585 0 2399.0

20 468 67.51 2217.0

40 351 135.0 2068.3

60 234 202.5 1987.0

80 117.2 270.0 1830.6

100 0.0 337.6 1740.6

2.2.2 Workability

The workability is defined as the ease with which concrete can be mixed,

transported and been put into moulds, is affected by the interactions of tire rubber

particles and mineral aggregates (Oikonomou & Mavridou, 2009, p. 216). The

measurement unit of workability is the value of slumps that through a slump test.

It has been observed that the rubber aggregate shape contributes to the slump

value (workability). The workability is immediately connected with the shape of

aggregates. Mixes containing long, angular rubber aggregate presents lower slump

values than mixes with round rubber aggregate as the last has lower surface-volume

ration. As a result less mortar is needed to coat the aggregates and the rest provide

workability. It is suggested that 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 mix (Cairns, Kew, & Kenny, 2004, p. 16). The results of this experiment are

shown on the table below. For group C, rubber aggregate coated with cement paste

has been used, and for group P plain rubber aggregate substitutes the coarse aggregate

of the control mix. The water cement ration is 0.48.

Literature Review

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Table 3: Workability test results.

Sample % of rubber Slump (mm)

Control Mix 0 55

C10 10 14

C25 25 3

C50 50 0

P10 10 16

P25 25 6

P50 50 0

Khatib & Bayomy in 1999 (p. 208) observed that a decrease in slump with

increased rubber aggregate content by total aggregate volume. The results showed that

in concrete with 40% content of rubber aggregate, 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. The figure below shows the results from the workability

test.

Group A: crumb rubber replaces sand

Group B: Tire chips replace coarse aggregate

Group C: combination of crumb and chips rubber in equal quantities

Figure 1: Graph of workability.

The graph below from the experiment of Mavroulidou & Figueiredo in 2010

confirms the previous observation. Figure 2 show how the workability is affected by

the rubber content in concrete for both cases, with coarse rubber aggregates (CRA)

and fine rubber aggregates (FRA).

Literature Review

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Figure 2: Average slump test results for each rubber percentage.

2.2.3 Durability

There has not been a great deal of research on the durability of concrete modified

with waste rubber. Cement mortars containing waste rubber showed a decrease in

chloride ion penetration as the percentage of tire rubber increases. There is a further

decrease in chloride ion penetration when adding commercial products comprising an

anionic bitumen emulsion and SBR latex. On the other hand for a given water-cement

ratio and with a moist curing period of 3 and 7 days, the use of rubber increased the

chloride ion penetration through concrete and the degree of ion permeability depended

on the rubber percentage used. After 28 days of curing there was a greater reduction

in the magnitude of the chloride ion penetration into the mortar (Oikonomou &

Mavridou, 2009, p. 220).

2.2.4 Water absorption

The water absorption of a material is one of the major factors that influence the

durability of concrete. The cement paste could be modified with tire rubber elements

decreasing the water absorption of the cement due to the property of rubber to repel

water. Furthermore, the particles of rubber could reduce the speed of absorption that

flow into the mass. In other words, substituting partially into the cement shredded

rubber wastes, the water absorption is decreased and as a consequence the cement

paste gains durability. The experiment from Benazzouk, et al. in 2007 works as a

proof where they replaced partially tire rubber into the cement and the result was the

reduction of the hydraulic transport properties, proving the improved durability of

cement that contain rubber tire.

Literature Review

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2.2.5 Toughness and impact resistance

The toughness is the capacity of a material to absorb energy and is generally

defined by the area under load – deflection curve of a flexural specimen. The

toughness usually is measured in Joules (energy units) (Rafat & Tarun, 2004, p. 567).

The rubber is more elasticity material than any constituent of concrete. Thus, a

rubberized concrete is expected to present larger toughness and that means larger

energy absorption providing smaller impact resistance. However, this property of

rubber influences the mechanical properties of the rubberized concrete giving smaller

strengths.

Topçu & Avcular in 1997 claimed that the impact resistance of concrete increases

when rubber aggregates are incorporated into the concrete mixtures. The increase in

resistance was derived from the enhanced ability of the material to absorb energy.

2.2.6 Freeze - thaw protection

One of the biggest concerns of the traditional concrete is the low freeze – thaw

protection of it. The major problem in case that the environmental temperature is

lower than 0 degree of Celsius then the water that exist on the particles of the cement

are freezing as a consequence the water’s volume expands by 9%. This expansion of

water causing forces in the internal of the concrete structure resulting cracks that

causes loss of strength. One solution to this problem is the air entrained concrete.

Adding big voids in the concrete, allows the water expansion to be applied no forces

on the concrete’s components. Another, usual solution is the reduction of water

content. Although, the concrete losses its workability. In both solutions, the

compressing strength of concrete is reduced.

Thus, many studies have been done investigating the potential of a rubberized

concrete that will have better results in frost conditions. Major characteristic of the

rubberized concrete is the energy absorption. It is under investigation whether this

kind of concrete could absorb the water expansion forces without any cracks on

concrete mass.

2.3 Mechanical Strength - Properties

According to many studies that have been done for the mechanical strength of

rubberized concrete, it has been noticed that the major parameters that greatly affect

the strength are size, proportion, and surface texture of rubber particles, and the type

of cement used in such mixtures.

Literature Review

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2.3.1 Rubber Content and Particle Size

Various experiment results have shown that the coarse grading of rubber granules

reduces the compressive strength of the rubberized concrete more than the fine

grading. Eldin & Senouci in 1993 fully replaced the coarse aggregates with rubber

chips. This replacement contributed either to compressive and tensile strength

reduction by 85% and 50% respectively. However, when the fine aggregate was

replaced fully by fine crumb rubber, the strength reduction was up to 65% and 50%

for compressive and tensile strength reduction. The experiments of Topçu & Avcular

(1997) and Khatib & Bayomy (1999) confirm the previous statement, showing similar

results in strength reduction. However, results of tests carried out by Fatuhi & Clark

(1996) indicate the opposite trend.

2.3.2 Surface Texture

Many studies have shown that one major parameter which contributes to strength

is the bond between aggregate and the surrounding cement paste. It has been noticed

that rubber aggregates with rougher surface give better bonding and as a result the

compressive strength is increased. Tanatala, Lepore, & Zandi in 1996 argued that one

effective way to increase this bonding in order to achieve higher compressive strength

is to pre-treat the rubber aggregate.

According to Cairns, Kew, & Kenny (2004, p. 21) Pre-treatments vary from

washing rubber aggregate with water to acid etching, plasma pre-treatment and

various coupling agents. The acid pre-treatment involves soaking the rubber aggregate

in an acid solution for 5 minutes and then rinsing it with water. As observed through a

microscope, the pre-treatment of rubber aggregate with acid increased the surface

roughness of rubber, which improves its attachment to the cement paste.

Significant improvements in compressive strengths have been found through the

experiment of Rostami, Lepore, Silverstraim, & Zundi in 2000 where they cleaned the

rubber by two ways, firstly cleaning them with water (Figure 3) and secondly with

water, carbon tetrachloride (CCL4) solvent and water and a latex admixture cleaner.

The results showed 16% higher compressive strength for the simply cleaned rubber

and 57% for the rubber aggregates that treated with CCL4, in comparison with the

untreated rubber (Nehdi & Khan, 2001, p. 6).

Literature Review

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Figure 3: Effect of washing rubber particles with water on compressive strength of rubcrete

mixtures.

Another method that improves the strength is the coating of rubber with the

cement paste. It has been tried by Li, Li, & Li in 1998 and the result was significant

with the compressive strength to increases by 30%. However, the flexural strength

presents small improvements by this method.

Figure 4: Rubber aggregate coated with cement paste.

Segre & Joekes in 2000 tried a surface-treated putting rubber aggregates in

aqueous solution of sodium hydroxide (NAOH) for 20 minutes at room temperature

conditions. The results of abrasion resistance experiments that have been performed

with test specimens containing plain rubber aggregate or NAOH treated rubber show

that the NAOH treated rubber present significantly lower mass loss than specimens

containing plain rubber aggregate. This experiment proves that the rubber aggregate

after an appropriate treatment could present higher adhesion.

Literature Review

P a g e | 11

2.3.3 Effect of Using Special Cements

According to Biel and Lee (1996) the type of cement that is used in rubberized

concrete highly affects the mechanical properties such as strength. On this research

the tire rubber particles substitute the fine aggregates from 0% to 90% by increments

of 15%. Furthermore, they have added to each sample both magnesium oxychloride

cement and Portland cement, in order to observe the effects of different cements. It

has been observed that concrete with 90% fine aggregate substitution (25% by total

volume) presents 90% reduction on compressive strength both for magnesium

oxychloride cement (MOCRC) and Portland cement (PCRC) (Figure 5).

Figure 5: Effect of cement type on compressive strength.

It also can be observed that in case of concrete without rubber the magnesium

oxychloride cement gives compressive strength almost 2.5 times higher than Portland

cement concrete.

The Portland cement concrete samples containing 25% of rubber by total

aggregate volume retained 20% of their splitting tensile strength after initial failure,

whereas the magnesium oxychloride cement concrete samples with similar rubber

content retained 34% of their splitting tensile strength after initial failure (Figure 6).

The ration between MOCRC and PCRC tensile strength starts from 1.6 (0%

substitution) ending to 2.8 (25% substitution). It was argued by the authors that the

magnesium oxychloride cement provides higher strengths and better bonding

characteristics to rubcrete mixtures and it could have a great performance in structural

applications if the rubber content does not exceed 17% by total volume of the

aggregate.

The effects of using blended cements, fibre reinforcement, chemical admixtures,

polymer resins, and other additives in rubcrete remain to be investigated

Literature Review

P a g e | 12

Figure 6: Effect of cement type on split tensile strength.

2.3.4 Strength

The major property of concrete is the high compressive strength. As far as

rubberized concrete, it can be noticed that has lower strength than the traditional

concrete. Thus, it can be used mainly for secondary usages that are not required high

strengths. Figure 7 illustrates a graph that has been extracted from the experiment of

Batayneh, Iqbal, & Ibrahim (2008), where some rubberized concrete specimens have

been tested for various percentages of crump rubber content.

Figure 7: Comparison between strength reduction and rubber content.

On the other hand Khatib & Bayomy in1999 tried to investigate the influence of

rubber for three different substututions.

Crumb ruber replaces sand (Group A).

Chipped rubber replaces coarse aggregate (Group B).

Combination of crumb and chipped rubber (Group C).

The results of compressive strength are shown below.

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P a g e | 13

Figure 8: Compressive Strength results.

It is easily understandable from the figure that the substitution of traditional

aggregate in concrete with crumb rubber content influences in a big grade the

mechanical properties of concrete. Furthermore, it can be noticed that the flexural,

tensile and compression strengths are affected negative by the same way.

2.3.5 Stress-strain relationship

On the same experiment have been investigated the stress strain relationship of

the rubberized concrete (Figure 9). There are two significant conclusions that could be

noticed through this graph. Firstly, as the rubber content increasing, the maximum

stress is reduced. Secondly, the concrete containing less rubber is more brittle due to

energy absorption property of rubber.

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Figure 9: Relationship between stress and strain for different rubber contents.

2.4 Civil Engineering Applications of Rubberized Concrete

Currently, the number of used tires which are recycled in civil engineering

applications is very low and there is a potential to develop new markets for the

products incorporating recycled tires. This includes about £1.8bn annual expenditure

on concrete products in the UK alone. However, any rubberized concrete products

developed for the market need to be feasible in terms of cost, including material costs

and production processes. This section considers the potential of rubberized concrete

in various civil engineering applications. The discussion focuses on rubberized

concrete blocks, which show the greatest potential for market development at present.

However, the potential utilization of rubber aggregate in composite construction is

also considered (Cairns, Kew, & Kenny, 2004, p. 67).

Many studies have proved that concrete modified with tire rubber can be used in

applications where mechanical properties are not of prime importance. However, in

civil engineering there is a huge range of potential applications that do not required

extremely strong mechanical properties.

2.4.1 Pavement Applications

According to research of Oikonomou & Mavridou (2009, p. 234), pavements

made of rubberized asphalt mixed with aggregates have been constructed widely with

great success. Such sections have better skid and rutting resistance, and improved

fatigue cracking resistance, while their service life can be greater than that of

conventional sections. Moreover, it is possible to lay pavements made of rubberized

asphalt under a wide range of climatic conditions, as mentioned by many researchers.

Furthermore, higher rubber content blocks with low strength and high toughness

characteristics could be used for specific applications that do not require a high-

Literature Review

P a g e | 15

strength such as sidewalks and playgrounds and may be viable for other applications,

depending on the percentage of crumb rubber used (Ling, Nor, & Lim, 2010, p. 44).

2.4.2 Geotechnical Applications

Tire chips are advantageous for use in geotechnical applications because of their

low density and high durability, shear strength and thermal insulation; in many cases

they are also cheaper compared with other fill materials. The use of tire rubber as a

lightweight geomaterial for embankments or as backfill against retaining walls is very

promising and should be promoted. Thus, large volumes of waste tires can be

consumed (Oikonomou & Mavridou, 2009, p. 235).

2.4.3 Concrete Blocks

Ling, Nor, & Lim in 2010 (p. 44) stated that blocks incorporating crumb rubber

are found to have slightly higher sound absorption coefficients, and this property may

resolve the noise generation problem faced by conventional concrete block

pavements. A series of laboratory accelerated loading tests has been carried out and

encouraging results on the structural performance of rubberized concrete pavement

blocks are obtained. It is therefore suggested that rubberized concrete pavement

blocks products could be introduced for varied paving applications.

2.4.4 Other Applications

One of the most significant properties of rubberized concrete is undoubtedly the

light unit weight of it where makes this material quite attractive for architectural

applications that require this property such as stone backing, nailing concrete, false

facades and for interior small scale constructions. Moreover, it is expected on the near

future this type of concrete to find new routs of utilization in highway construction as

a shock absorber, in sound barriers as a sound absorber, and also in buildings as an

earthquake shock-wave absorber (Topçu & Avcular, 1997). However, more research

is required before such recommendations can be made.

Additionally, Fatuhi & Clark in 1996 (p. 236) suggest a list of interesting

applications where cement based materials containing rubber could have potential

usages. These include areas:

• Where vibration damping is required, such as in foundation pads for machinery,

and in railway stations.

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• Where resistance to impact or explosion is required, such as in jersey barriers,

railway buffers, and bunkers.

• For trench filling and pipe bedding, in artificial reef construction, for pile heads

and paving slabs. The present authors are currently conducting research exploring

new areas of application for rubcrete mixtures, which potentially can use large

volumes of this material. Focus is particularly on emerging geotechnical construction

methods in which buffer layers of a low-strength high-ductility material are required

to absorb excessive delayed deformations (Nehdi & Khan, 2001, p. 8).

2.5 Conclusion

Waste tire management is a serious global concern as huge amounts of wastes are

stockpiled every year in landfills causing very dangerous environmental threats.

Therefore, there is a keen demand for alternative utilization of these wastes to be

recycled.

This study examines some of the basic properties either for concrete with rubber

coarse aggregates (rubberized concrete) and for rubber fine aggregate (rubcrete)

giving for each category potential applications in civil engineering works, such as an

aggregate or additive in cement products, in road construction, as lightweight fill for

embankments or as backfill material for retaining walls. The results of these studies

show that concrete modified with tire rubber can be used in applications where

mechanical properties are not of prime importance.

However, it can be noticed that many potential uses in the civil engineering

industry of this waste material is still under investigation having a very prospective

future.

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Chapter 3: Methodology

The tests conducted for the current research investigates the influence of the

rubber aggregate as a replacement material into concrete. The rubber tires can be

shredded into different size so it is possible to re-use as a substitute both for coarse

and fine aggregate.

One of the main purposes of this research was to investigate the potential of

recycled rubber to be used in structural applications. Thus, this research concentrates

to test high level rubberised concrete strength. It has been already identified from

literature that the rubber in concrete reduces the strength significantly, thus all the

substitutes in this project did not exceed the 10% replacement mark.

Table 4 highlights the five different concrete mixes that were used for fresh and

hardened concrete tests. Tests were performed on cubes, cylinders and beams. Three

replicates were prepared and utilised for each test.

Table 4: Concrete Mix Description.

Mix No Abbreviation Description

1 C The control mix has been done according to the mix design, without

rubber replacement.

2 F.A. Crumb rubber replaces fine aggregate by 10% of its volume

3 C.A. Chipped rubber replaces coarse aggregate by 10% of its volume

4 C.A.C.P. Chipped rubber soaked in cement paste replaces coarse aggregate by

10% of its volume

5 F.C.A.C.P. Chipped rubber soaked in cement paste replaces coarse aggregate by

5% and crumb rubber replaces fine aggregate by 5% of its volume.

Table 5: Labels of samples.

Sample Label Mix 1 Label Mix 2 Label Mix 3 Label Mix 4 Label Mix 5

Cube 1 C1 F.A.1 C.A.1 C.A.C.P.1 F.C.A.C.P.1

Cube 2 C2 F.A.2 C.A.2 C.A.C.P. 2 F.C.A.C.P.2

Cube 3 C3 F.A.3 C.A.3 C.A.C.P. 3 F.C.A.C.P.3

Cylinder 1 C1 F.A.1 C.A.1 C.A.C.P.1 F.C.A.C.P.1

Cylinder 2 C2 F.A.2 C.A.2 C.A.C.P. 2 F.C.A.C.P.2

Cylinder 3 C3 F.A.3 C.A.3 C.A.C.P. 3 F.C.A.C.P.3

Beam 1 C1 F.A.1 C.A.1 C.A.C.P.1 F.C.A.C.P.1

Beam 2 C2 F.A.2 C.A.2 C.A.C.P. 2 F.C.A.C.P.2

Beam 3 C3 F.A.3 C.A.3 C.A.C.P. 3 F.C.A.C.P.3

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3.1 Materials

3.1.1 Cement

Snowcrete (CEM I) 52.5R cement produced by Lafarge manufacture company

was utilised during this trial. Snowcrete has similar properties to ordinary Portland

cement, the only difference being the white colour (Figure 10). Other properties of the

cement utilised during the trial is shown in Table 6.

Does not contain any white pigments or additives.

Similar setting time to Bulk Portland Cement.

Higher early and later strengths than Portland cement CEM l 42.5.

Naturally low in Chromium (VI) (below 2ppm).

(Lafarge, 2012)

Table 6: Typical Properties of snowcrete Portland cement.

Figure 10: Snowcrete cement by Lafrage.

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3.1.2 Aggregates

Two different kinds of aggregate were used during the trial. The traditional

limestone aggregates, and the rubber aggregates. Both aggregates are separated

according to their size into two categories:

Traditional limestone aggregates

Coarse Aggregate (2 different sizes 10mm and 20mm) (Figure 11)

Fine Aggregates (approximate 0.2-0.3mm) (Figure 12)

Figure 11: Coarse aggregate 20mm (left) and 10mm (right).

Figure 12: Sand.

The limestone aggregates are supplied by the laboratory of University of

Portsmouth. All aggregates were held into laboratory’s temperature and moisture

environment (20 ± 5°C). Two different sizes of uncrushed aggregate have been used

for the mix design, 10 mm and 20 mm.

Rubber aggregates

Chipped rubber pre-treatment in cement paste

Chipped Rubber (14-10mm)

Crumb Rubber (0.6mm)

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Figure 13: Chipped Rubber (left), crumb rubber (right).

The rubber aggregates are produced by CRUMB RUBBER LTD (Crumb Rubber

LTD, 2012).

The chipped rubber replaces the limestone aggregates into the concrete as they

have similar size, and the crumb rubber replaces sand (fine aggregate).

Cement paste was prepared blending 800g cement with 400g water (w/c ratio

0.5). Chipped rubber added to this mixture and was blending till the whole amount of

cement paste to spread on rubber’s surfaces. Immediately after this procedure the

chipped rubber was spread on a clean dry surface for 24 hours (Figure 14).

Figure 14: Chipped rubber soaked in cement paste.

3.1.3 Measurement of the specific weight

At this point it should be referred that the rubber has almost the half specific

weight than the natural aggregates and for this reason all the substitutions that have

been done are based on volume and not on weight. Nevertheless, all the substitution

have been done according to weight taking into account the ratio between specific

weights of rubber and natural aggregate. For example if this ratio is 0.5 (the half),

Methodology

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then 100g of natural aggregates are replaced by 50g of rubber, so in this way the

volume of two materials are equal.

For the specific weight measurement it has been followed the Archimedes’

method. A small amount of each material has been chosen, the weight was measured

on balance and volumes were measured through graded tube that was full of water

(Figure 15). The specific weight was calculated dividing weight with volume. The

results are shown on Table 7.

Figure 15: Specific Weight measurement.

Table 7: Specific weight calculations of aggregate using Archimedes’ method.

Calculated Specific Gravity of Aggregates

Material Weight

(g)

Initial Reading

V1 (mL)

Reading

V2 (mL)

Volume

(mL)

Specific

Weight (g/mL)

Fine Aggregate 758 1200 1500 300 2.53

Coarse Aggregate 20mm 1000 1040 1420 380 2.63

Coarse Aggregate 10mm 1000 988 1390 402 2.49

Rubber Chipped Aggregate 180 1200 1364 164 1.10

Rubber Crumb Aggregate 180 1200 1364 164 1.10

Ratio of Specific Weight Crumb / Fine 0.43

Ratio of Specific Weight Chipped / Coarse 0.43

3.2 Sieve Analysis

The sieve analysis has been conducted from other students of the department both

for natural and rubber aggregates (Table 13). The chart below is based on the

researches by:

Limestone aggregate: (Konstantinou, 2011, p. 12)

Chipped rubber: (Hayat, 2011, p. 42)

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Crumb Rubber: (Desmond, 2012, p. 21)

Figure 16: Sieve Analysis of the limestone aggregates.

3.3 Concrete Mix Design

For the purposes of this experiment it was required to be formed:

3 cubes (100mm × 100mm × 100mm)

3 cylinders (100mm diameter, 200mm height)

3 beams (100mm × 100mm × 500mm)

The total volume of concrete that was needed to be produced:

Cubes Volume: 0.103m × 3

= 0.003m

3

Cylinders Volume: πr2

× height × 3 = 3.14 × (0.10m/2)2 × 0.2m × 3

0.00471239m3

Beams Volume: 0.10

2m × 0.50m × 3

= 0.015m

3

Total Volume = 0.003m3 + 0.0047m

3 + 0.015m

3 = 0.0227m

3

Final Total Volume = 0.0227m3 × 1.10 ≈ 0.025m

3

The volume of the cone for the slump test was not included to the above

calculations as the amount of fresh concrete was used after the test for the filling of

the rest samples.

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The form on Table 12 assisted to the determination of the control concrete mix

design portions and both tables and graphs where used on this form, are shown in the

Appendix chapter.

All substitutions of the rubber have been done as mentioned before, based on the

specific weight ratios of Table 7 (volume substitution). The tables below show the

quantities that were used for the five mix designs.

Table 8: Mix design portions (kg/m3).

Mix Cement

(kg/m3)

Water

(kg/m3)

Traditional Aggregate Rubber Tire

Aggregate Unit Weight

(kg/m3)

Fine

aggregate

(kg/m3)

Coarse Aggregate

(kg/m3)

Crumb

Rubber

(kg/m3)

Chipped

Rubber

(kg/m3) 10mm 20mm

1 390 195 582 394 789 0 0 2350

2 390 195 523.8 394 789 25.282 0 2317.082

3 390 195 582 354.6 710.1 0 50.728 2282.428

4 390 195 582 354.6 710.1 0 50.728 2282.428

5 390 195 552.9 374.3 749.55 12.641 25.364 2299.755

Table 9: Mix design quantities (kg) based on specimens’ total volume.

Mix Cement

(kg)

Water

(kg)

Traditional Aggregate Rubber Tire

Aggregate Total Weight

(kg) Fine

aggregate

(kg)

Coarse

Aggregate(kg) Crumb

Rubber

(kg)

Chipped

Rubber

(kg) 10mm 20mm

1 9.744 4.872 14.540 9.844 19.712 0.000 0.000 58.712

2 9.744 4.872 13.086 9.844 19.712 0.632 0.000 57.889

3 9.744 4.872 14.540 8.859 17.741 0.000 1.267 57.023

4 9.744 4.872 14.540 8.859 17.741 0.000 1.267 57.023

5 9.744 4.872 13.813 9.351 18.726 0.316 0.634 57.456

The sampling and mix procedure was followed according to instructions of

British Standard (BS 1881-125:1986).

It should be referred that throughout the vibrating procedure was observed that

samples containing chipped rubber presented uneven distribution on aggregate (Figure

17). The chipped rubber had trend to go to the top of the sample due to its low specific

weight. Some strokes were required in order to improve this distribution.

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Figure 17: Bad distribution of chipped rubber during vibrating process.

3.4 Slump Test Procedure

The slump test procedure was followed after the mixing of concrete as it is

defined from the British Standards (BS 1881-102 1983). The mould for the slump test

should be in cone shape and the sizes are given bellow:

diameter of base: 200 ± 2 mm

diameter of top: 100 ± 2 mm

height 300 ± 2 mm

Before the concrete sampling a cone mould was placed on a smooth, horizontal,

rigid and non-absorbent surface (Figure 18). When the mixing procedure finished, the

cone mould was filled in three layers of concrete and for each layer 25 strokes of a

tamping rod were required in order to compact the concrete.

Figure 18: Slump test cone mould.

After the filling, the mould was removed slowly and carefully in 5s to 10s, in

such a manner as to impart minimum lateral or torsional movement to the concrete

Methodology

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and then immediately, the mould was placed near to specimen and the difference

between the heights of them was measured using a rule.

The test is only valid if it yields a true slump, this being a slump in which the

concrete remains substantially intact and symmetrical as shown in Figure 19.

Figure 19: Forms of slumps.

Immediately, after finishing of this procedure the tested specimen was not wasted

and was used for the sampling. This is the reason that the volume of the cone was not

included on the concrete volume calculation.

3.5 Machinery and Equipment

All equipment and machines that were used for the experiments are supplied and

located on the laboratory of University of Portsmouth.

3.5.1 Digital Balance:

The digital balance is manufactured by Precisa LTD with maximum capacity of

40.1kg.

Figure 20: Digital Balance.

Methodology

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3.5.2 Moulds

All mixes are casted in metal moulds that cover the British Standard

requirements. Before each sampling the moulds were sprayed with special oil in order

to make the de-mould procedure more convenient.

Figure 21: Metal Moulds.

3.5.3 Pan Mixer Machine

Due to the big amount of the batch it has been chosen a pan mixer for the mixing

of concrete (Figure 22). The mixer machine covers the British Standards’

requirements, and the size of the batch was always between 50% and 90% of the

mixer’s rated capacity.

Figure 22: Pan mixer machine.

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3.5.4 Table Vibrator

After the mixing of concrete and casting procedure, the vibrator table was used

for the compaction process.

Figure 23: Vibrating table.

3.5.5 Water Tank

The water tank was used for the 28 days curing of samples. The temperature of

water into the tank is 20 ± 2°C. The volume capacity of the tank is 0.8m3

and the

dimensions are: 0.58m depth × 0.87m width × 1.57m length.

Figure 24: Water Tank.

3.5.6 Compressive Test Machine

This machine was used to test the strength of the cube and cylinder samples,

displaying the maximum stress of them.

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Figure 25: Compressive Strength Machine.

3.5.7 Milling Machine

Before the Elastic Young’s Modulus test the cylinders’ surfaces should be quite

flat in order to have proper results. The machine on the picture below flattens concrete

surfaces.

Figure 26: Milling Machine.

It should be highlighted that it was quite hard to flatten concrete containing

chipped rubber as chipped rubber protruded a little bit on the surface (Figure 27).

However, this fact did not affect significantly the Elastic Young’s Modulus Test as

the rubber is quite elastic and during the test procedure the load was applied on the

surface and the rubber reached on the same layer of the other aggregate.

Figure 27: Chipped rubber protrusion.

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3.5.8 Elastic Young’s Modulus and Flexural Strength Test Machine

This machine was used both for Elastic Young’s Modulus and Flexural Test

changing the metal base for each case. This is an old type machine (Figure 28) and the

applied load is given by the user manually rotating the relevant knob.

Figure 28: Elastic Young’s Modulus and Flexural Strength Test Machine.

For the flexural strength beam test, the beam was laid on two supports and two

loads were applied on it. When the beam failed the maximum load was taken from the

display.

For the elastic young’s modulus test, initially the two metal surfaces should be

laid above and below the sample (the load is applied through them) and two metal

rings with a gauge should be installed around the cylinder in order to measure the

strain each time. Giving the appropriate load for each cycle the readings from the

gauge were taken for the calculation of strain.

On this test it was measured both stress and strain of each concrete sample

reaching the ultimate stress of material’s elastic area. The upper limit of the elastic

area is approximate the one third of compressive strength. For this reason before the

test the average compressive strengths (cubes) were calculated divided by three and

this strength is applied to the cylinder. One cycle means the loading of cylinder from

1 MPa to one third of its compressive strength. For each cycle the corresponding

strain value was measured by the gauge where was installed to the sample (Figure 29).

This procedure of loading was repeating till the stress and strain values of the last

cycle will be almost the same with the previous one. Then the strain values from the

last cycle are taken as final strain. The final stress is just the one third of compressive

strength minus 1 MPa. From these two values the elastic young’s modulus was

estimated dividing the stress by strain.

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Figure 29: Elastic Modulus Testing Apparatus.

3.5.9 Ultrasonic Pulse Velocity (UPV Pundit)

The pundit was used for determination of the dynamic elastic modulus and is one

of the most common non-destructive methods for concrete. There is a transmitter and

a receiver that are laid on the two opposite sidewalls of the cube specimen. The

ultrasonic travels through concrete from transmitter to receiver and this device

measures the velocity of ultrasonic pulse. In case that into concrete there are voids or

cracks the velocity appears to be higher so the velocity is an indicator of concrete’s

quality (Barnett & Ali, 2012).

The test procedure is quite simple and the user should move the transmitter and

the receiver over the surface till the lower number to be displayed, and this is recorded

as the final velocity. A green gel has been spread on the surfaces, in order to avoid

any presence of air on this area.

Figure 30: Pundit.

3.5.10 Schmidt hammer

A mass impacted to the concrete surface and the rebounded distance is measured.

The readings strongly depend from the hardness of the surfaces. In other words it is

Methodology

P a g e | 31

quite sensitive to presence of voids or aggregates below the point of impact. This is

the main reason that many rebound numbers are required. The median of all the

rebound numbers is taken and through a chart (Figure 31) given by manufacturer, the

compressive strength can be estimated (Barnett & Ali, 2012).

Figure 31: Rebound hammer chart.

This method is not the most appropriate for laboratory tests because is quite

proximal. However it has been followed in order to have a comparison between the

result of this test and the compressive strength.

This test has been done only for cubes and beams. 7 rebound numbers from cubes

and 12 from beams have been taken.

Figure 32: Schmidt hammer.

Results and Discussion

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Chapter 4: Results and Discussion

4.1 Fresh Concrete

4.1.1 Workability (Slump Test)

All the slump tests for the five mixes have appeared true slumps (Figure 33), so it

could be said that the results on the table below are valid.

Figure 33: Slump forms.

It is obvious from the results that rubber into concrete affects the workability of

it, making the concrete less workable. These results prove that the rubber has a

rougher surface than the other aggregates and gives bigger frictions than the

traditional aggregates.

Table 10: Slump Test Results.

Mix Num Slump (mm)

1 30

2 20

3 17

4 24

5 31

On the chipped rubber substitution (Mix 3) was observed the biggest reduction of

slump (from 30 mm to 17mm). It was expected as the chipped rubber has bigger

volume than the crumb and a bigger surface around it. As a result the friction between

the aggregates’ surface is bigger causing less workability on the concrete.

Results and Discussion

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A remarkable result occurred on the fourth mix where the cement paste increased

the workability from 17mm to 24mm. An assumption that might be made is that the

cement paste on the chipped rubber’s surface made the surface almost the same than

the limestone aggregate decreasing the friction of it.

Finally, 5% of chipped aggregate soaked in cement paste cooperating with 5% of

crumb rubber gives almost the same slump with the control mix.

As a conclusion could be assumed that the cement paste reduces the friction of

rubber surface in small quantities (up to 5%) does not affect the workability of

concrete.

4.2 Hardened Concrete

4.2.1 Water absorption

After the de-mould all the specimens were weighed on the balance before the

curing process of the water tank. The same procedure was followed after 28 days

when they were removed immediately from the water. By this process it can be found

out how much quantity of water each sample has absorbed. When the samples were

removed from the water, their surfaces were wiped slightly and quickly using a towel

(Figure 34).

Figure 34: The samples after the removal from the water.

The formula that expresses the water absorption (%) is:

{Equation 1}

Wa: water absorption (%)

wwet: wet weight

wdry: dry weight

Results and Discussion

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This number expresses how much water has been absorbed (%) in comparison

with its initial (dry) weight. It is important to refer that the water absorption’s values

strongly depend from the shape of each sample, for example the cubes appear higher

values of water absorption than the other samples (beams and cylinders).

On Table 15 and Table 16 the results are shown for cubes, cylinders and beams

respectively. On the chart below are shown the water absorption of cubes.

Figure 35: Cubes’ water absorption.

According to the results 10% containing of rubber into concrete reduces almost

14% the water absorption of it. Observing the figures of Mix 3 and Mix 4 it is

obviously that cement paste around on chipped rubber gives a further reduction.

4.2.2 Compressive Strength

According to the results (Table 17 and Figure 36), they have been done some

observations where they are analysed below.

Results and Discussion

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Figure 36: Compressive Strength Chart.

The compressive strength test shows as it was expected that in general rule the

rubber reduces the compressive strength. However, there is big deference on the

reduction strongly depending on the rubber aggregate size. For 10% of crumb rubber

into concrete there is just a slight reduction on strength of 7% but for the same

percentage of substitution of chipped rubber there is almost double reduction of

around 17%. So as a conclusion it could be carried out that the crumb rubber affects

less the compressive strength than the chipped for the same percentage of substitution.

On the other hand the cement paste around on chipped rubber seems to give

higher strength reaching almost the same level of crumb rubber strength. In a

comparison between the Mix 3 and Mix 4 the cement paste increases the strength by

6.3%. There are two possible reasons for this increase, the higher content of cement

into this mix increases the strength as well as the cement paste around makes stronger

the rubber aggregate.

As far as the fifth mix, its strength seems to be roughly near to the second mix

with an almost negligible difference.

On these results there is something quite remarkable in terms of deviation, it can

be observed that the samples containing chipped rubber seem to have higher deviation

on strength than specimens with crumb rubber. This clearly occurs from the mix

procedure where the small size aggregates can easily represent better their portion on

each specimen in contrast with bigger aggregates that present higher variations into

the concrete mass

Results and Discussion

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In terms of failure behaviour of cubes has been observed (Figure 37) that

concrete with chipped rubber appears smaller cracks than the control mix. However,

the chipped rubber seems to cause almost the same degree of cracks as the ordinary

concrete. These cracks are energy absorption indicators and it is clearly that chipped

rubber could lead to a concrete with higher energy absorption and this could be very

desirable for applications that require this property as it happens usually for seismic

areas constructions.

Figure 37: Cubes’ failure (Mix 1, 2, 3, 4, 5 in row).

On this point it is quite interest comparison of compressive strength with relevant

experiments that have been done from other researches. The chart below illustrates the

reductions on compressive strength from other experiments for the same percentage

and kind of substitution.

Results and Discussion

P a g e | 37

Figure 38: Compressive Strength Comparison.

All these experiments have been done with the same portions of rubber

substitution and generally their mix designs seem to be similar between them.

However, the figures of the results are very different, this lead to the conclusion that

the strength of rubberized concrete depends on many parameters. This fact indicates

that there is a lot of future work that should be done in order to investigate what

exactly makes the compressive strength of rubberised concrete higher or lower.

It should be said that for Mix 5 (5% of crumb rubber and 5% of chipped rubber

with cement paste) does not exist a similar research for this percentage of substitution.

4.2.3 Flexural Strength

There are two ways for flexural strength estimation. One of them is the Brazilian

test where a cylinder is laid on the compressive test machine as it is shown in Figure

39. The load is applied above and below of the cylinder, and the maximum load is

taken for the tensile strength calculation using the equation below:

{Equation 2}

F: is the maximum load

d: is the diameter (100mm)

h: is the cylinder’s height (200mm)

Results and Discussion

P a g e | 38

Figure 39: Brazilian Test.

However, the second method has been chosen to be done where a beam was laid

on two supports and two loads were applied above it (beam under 4 point bending).

The maximum load (KN) was used each time for the flexural strength calculation

through the equation below.

{Equation 3}

F: is the maximum load

L: is the span between the two supports (400mm)

b: width (100mm)

d: thickness (100mm)

All the results from flexural strength test procedure are shown on Table 18. It

should be referred before the result discussion that this test has been done on an old

type testing machine where the load is applied manually by the user so a different

pace on load increment could lead to different result.

According to the chart below the crumb rubber seems almost to not affect the

flexural strength of the beam as it has been observed just a reduction of 2.5% as well

as in mix 5 there is a same level reduction. However, the chipped rubber (Mix 3)

appears 7.5% reduction. In terms of Mix 4 flexural strength seems to be in a very low

level remarkably. This could have happened because of the different pace that the

load has been applied during the test procedure.

Results and Discussion

P a g e | 39

Figure 40: Flexural Strength Chart.

A remarkable observation has been done during the process of testing beams

containing chipped rubber. Although beams from Mix 1 and 2 have been divided

totally on two pieces, did not happen the same with the beams containing chipped

rubber, appearing a big crack but not completely damaged (Figure 41).

Figure 41: Non-totally damaged beam.

This fact proves again that the chipped rubber has higher energy absorption than

the coarse aggregates. Moreover, from this observation another conclusion could be

extracted, the chipped rubber seems to have a remarkable high bond with the

limestone aggregates of concrete.

4.2.4 Elastic Young’s Modulus Test

From the chart below (Figure 42) and from Table 19 it can be observed that the

rubberized concrete presents reductions in elastic young’s modulus results between

Results and Discussion

P a g e | 40

20% - 25%. However, it is significantly observed that Mix 5 has a different tend than

the other mixes presenting almost the same figures with the control mix.

Figure 42: Elastic Young's Modulus Chart.

It is very important on this point to consider the variance on values for Mix 4 and

5. The values of elastic young’s modulus for the first three mixes seem to be quite

close to mean values and it can be said that they are quite representative. However, in

Mix 4 there is a sample that deviates too far than the other two samples. The reason of

this low value is that in loading procedure this sample failed as it can be observed

from the figure below. Considering the two other samples it can be assumed that the

Elastic Young’s Modulus for Mix 4 is approximately 30GPa instead of 26GPa.

Something similar seems to happen for Mix 5 but with the three samples to present

big variance between them without any value to be quite representative.

As a conclusion of this observation it can be said that samples containing rubber

usually does not give as representative values as the ordinary concrete does. It is

recommended for future researches to use more samples than three in order to get

more accurate and representative results.

Results and Discussion

P a g e | 41

Figure 43: Cylinders’ failure in Elastic Young’s Modulus Test Procedure.

4.2.5 Compressive Strength of Cylinders after the Elastic Modulus Test

After the elastic young’s modulus has been conducted the compressive strength

in order to observe how the strength has been affected from the previous procedure.

The chart below present the compressive strength and it is based on Table 21 (see

Appendix) that concentrates all the details (comparison with control mix, standard

deviation etc.).

Figure 44: Cylinders’ Compressive Strength

4.2.6 Ultrasonic Pulse Velocity

Before the ultrasonic pulse velocity test the mass density of each sample should

be known. The density is calculated using the formula below:

Results and Discussion

P a g e | 42

{Equation 4}

ρ: density (g/mL)

m: mass of sample (g)

mw: mass into water (g)

The values of mass (m) are taken from Table 14 (dry weight). In order to

calculate the mass into water, extra equipment is used (Figure 45). Below the balance

there is laid a container full of water. A steel installation assists to weight objects into

water. The cube’s density results are available in the appendix chapter.

Figure 45: Mass into water weighting.

As it has been said before the main purpose of UPV test is to check the quality of

concrete through the results of Dynamic Elastic Modulus Ed. In order to find these

values the equation below is used:

( )( )

( ) {Equation 5}

Ed: Dynamic Elastic Modulus (GPa)

ν: Velocity of ultrasonic pulse (is taken from the pundit) (μs)

u: Dynamic Poisson’s ration 0.15-0.20 (assuming 0.20)

The pundit gives just the time in μs. The velocity (v) is estimated dividing the

distance between transmitter-receiver (mm) with time (μs). For all samples the

distance (d) was the same equal to 100mm (dimensions of cubes).

Results and Discussion

P a g e | 43

The Dynamic Elastic Modulus is the stress-strain ratio of a material under

vibratory conditions.

Figure 46: UPV Chart.

Before every result discussion it should be referred that the ultrasonic pulse

velocity is a method that indicates the quality of concrete and not the strength of it.

Salam in 1992 (p. 88) stated that compressive strength might not be the best way

to represent the quality of concrete, but because a value for design is needed it has

become acceptable to all engineers that the quality of concrete as cast be determined

from the value of its compressive strength.

According to the results, concrete containing rubber aggregate seems to appear

better quality considering the higher velocity of them than the control mix. These

results prove that this method (UPV) is not the appropriate method for all types of

concrete to determine the strength as many researches have conducted in order to find

a correlation between the UPV and compressive strength. It might be acceptable for

other types of concrete but mainly for ordinary concrete.

The rubber in concrete seems to increase the dynamic elastic modulus by 15-20%

according to this method. Furthermore it is remarkable that all values present quite

small deviation, and this means that the method is pretty accurate.

4.2.7 Rebound Hammer Test

It can be noticed that the figures are too close without big variances between

them in a range of 20.7-23. Converting the average values to compressive strength

Results and Discussion

P a g e | 44

from the Schmidt chart on Figure 31 it is observed that the equal compressive

strengths for all mixes are approximately 15MPa. These values do not correspond to

the compressive strength results presenting reductions of 60-65%.

Table 11: Rebound Hammer Test Results.

Mix

Num.

Trial

1

Trial

2

Trial

3

Trial

4

Trial

5

Trial

6

Trial

7 Median Average

1 35 22 18 22 25 22 24 22

21 22 19 19 20 18 20 20 20

21 22 21 18 25 18 18 21

2 20 22 22 23 24 22 22 22

23 24 28 25 22 21 24 24 24

23 24 24 23 19 24 23 23

3 20 19 22 23 22 25 21 22

20.7 20 18 20 24 18 19 19 19

20 21 26 22 22 21 19 21

4 20 19 19 16 24 28 20 20

21 20 25 20 20 26 20 22 20

19 22 25 20 24 23 23 23

5 24 22 21 20 25 24 21 22

21.7 21 19 26 22 28 26 22 22

21 19 20 22 21 24 22 21

It is obvious that this is not an appropriate method for accurate results as well as

the samples that are used in the laboratory are two small for this kind of test. Usually

this test is conducted on bigger samples in the construction site. So after this

conclusion the results are not taking into account for this research.

Conclusion and Recommendations

P a g e | 45

Chapter 5: Conclusion and Recommendations

The general objective of this research was to investigate the fresh and hardened

properties of a concrete produced by replacing part of the natural aggregates with

recycled rubber tires shredded to two different sizes. From the test results of the

samples comparing to the control mix properties, the following conclusions and

recommendations are drawn out.

5.1 Conclusion

The recycled rubber in concrete (10% of substitution) in general rule decreases

approximate 30% the workability. However, this property significantly

improved when the chipped rubber is pre-treated soaking into cement paste.

Concrete containing pre-treatment chipped rubber cooperating with crumb

rubber of 5% replacement of each aggregate could give almost the same

workability with the control mix and even slightly higher than it.

The water absorption seems to present approximate reductions of 14% for all

mixes. The cement paste around the chipped rubber seems to affect more these

figures presenting a higher reduction of 26%.

As far as the compressive strength results the rubber in concrete seems to reduce

this strength from 7% to 9% for all mixes, but this reduction is almost double

(17%) where the untreated chipped rubber replaces the coarse aggregate.

Nevertheless, considering the procedure that should be followed for the pre-

treatment of rubber, it can be said that the best way for a high strength

rubberised concrete is to replace 10% of sand with crumb rubber. Furthermore,

a comparison that has been done with the compressive strength reductions from

relevant experiments shows that this specific mix design gives greatly smaller

reductions.

The flexural strength results showed similar trends with the compressive

strength. It should be highlighted that beams containing chipped rubber did not

appear similar failure (not completely split) comparing with the rest of the

beams. This fact lead to a conclusion that chipped rubber has strong bond with

concrete.

Conclusion and Recommendations

P a g e | 46

The elastic young’s modulus for the rubberised concrete seems to be reduced

almost 20 to 25% in comparison with the control mix. This proves the previous

statement that the rubberised concrete is less brittle than the ordinary. However,

the results of fifth mix are spectacular, presenting exactly the same figures with

the control mix.

From the compressive and flexural strength test procedures it has been observed

from cracks after failure that the rubberised concrete is less brittle than the

control mix, especially the samples containing chipped rubber. Thus it can be

characterised as better concrete for energy absorption.

Ultrasonic pulse velocity and rebound hammer test methods are not

recommended for this type of concrete. The UPV is designed mainly for

ordinary concretes. The rebound hammer test is inappropriate for laboratory

uses and is more recommended for in situ measurements on bigger samples.

Throughout the vibrating procedure it has been noticed that the lower specific

weight of chipped rubber contributes to uneven distribution into the mass of

concrete. The chipped rubber seems to be accumulated on the top of sample and

the rest limestone aggregates on the bottom because of their higher specific

weight. This phenomenon creates the urgent for an extra hand compaction.

Thus, concrete containing chipped rubber needs to be carefully compacted.

One disadvantage of concrete is the brittle behaviour of it. In many applications

people are concerned about this property of concrete. On the other hand

concrete presents satisfactory strengths. The main objective of this research was

to investigate potential ways of rubberised concrete to be used for structural

applications. Considering the results it could be said that rubberised concrete

could be acceptable for such applications. Although it presents reductions of

7%-9% on compressive strengths, rubber contributes to a high elasticity

concrete (20%-25% higher than control mix). So there are many civil

engineering and structural applications that require concrete with higher energy

absorption even if it loses a small percentage of compressive strength. Buildings

in seismic areas require concrete that could absorb the seismic energy as well as

buildings that should be protected by explosions. Pavement applications need

this absorption in order to defend the thermal expansion and contraction.

Conclusion and Recommendations

P a g e | 47

5.2 Recommendations

It has been observed that samples containing chipped rubber present bigger

variance on the results, so it is recommended to future works to test more

samples than three in order to get more accurate results. However, in some cases

the number of three trials is satisfactory.

In terms of compaction procedure it is recommended for future work to

investigate the influence of good compaction on rubberised concrete and how

this affects the strengths of it.

According to the current relevant researches it is noticed that the results depend

on many parameters and usually many differences are noticed comparing these

results. This fact indicates that more future work is required in order to

investigate completely what and how some parameters influences the rubberised

concrete results. This is one of the major reasons that the rubber is not quite

acceptable till today in many applications. Throughout more investigation, this

uncertainty could be eliminated for the near future and it will probably

contribute to a wider consumption of recycled rubber through civil engineering

industry.

References

P a g e | 48

References

[1] Crumb Rubber LTD. (2012, 08 03). Retrieved from Crumb Rubber LTD:

http://www.crumb-rubberuk.com/

[2] Lafarge. (2012, June 17). Retrieved from Lafarge UK web site:

http://www.lafarge.co.uk/CementDatasheet/Snowcrete%20CEM%20l%20Bul

k.pdf

[3] Barnett, S., & Ali, M. (2012, July 6). Notes for Construction Materials

Engineering. Retrieved from University of Portsmouth - Victory:

https://victory.port.ac.uk/webct/urw/lc5116011.tp0/cobaltMainFrame.dowebct

[4] Batayneh, M., Iqbal, M., & Ibrahim, A. (2008). Promoting the use of crumb

rubber concrete in developing countries. Waste Management, 28(11), 2171–

2176. doi:10.1016/j.wasman.2007.09.035

[5] Benazzouk, A., Douzane, O., Langlet, T., Mezreb, K., Roucoult, J., &

Quéneudec, M. (2007). Physico-mechanical properties and water absorption of

cement composite containing shredded rubber wastes. Cement and Concrete

Composites, 29(10), 732-740. doi:10.1016/j.cemconcomp.2007.07.001

[6] Cairns, R., Kew, H., & Kenny, M. (2004). The Use of Recycled Rubber Tires

in Concrete Construction. Proceedings of the International Conference of the

Concrete and Masonry (pp. 135-142). Thomas Telford Ltd.

[7] Desmond, K. (2012). Waste Tires in Concrete Block Pavement. BEng

Dissertation, University of Portsmouth, School of Civil Engineering and

Surveying, Portsmouth.

[8] Eldin, N. N., & Senouci, A. B. (1993). Rubber-Tire Particles as Concrete

Aggregate. Journal of Materials in Civil Engineering, 5(4), 478-496.

doi:10.1061/(ASCE)0899-1561(1993)5:4(478)

[9] Fatuhi, N. I., & Clark, N. A. (1996). Cement-Based Materials Containing

Shredded scrap truck tire rubber. Construction Building Materials, 10(4), 229–

236. doi:10.1016/0950-0618(96)00004-9

[10] Hayat, M. (2011). Use of Waste Materials for Highway Construction. MSc

Dissertation, University of Portsmouth, School of Civil Engineering and

Surveying, Portsmouth.

[11] Khatib, Z. K., & Bayomy, F. M. (1999). Rubberized Portland Cement

Concrete. Journal of Materials in Civil Engineering, 11(3), 206-213.

doi:10.1061/(ASCE)0899-1561(1999)11:3(206)

[12] Konstantinou, K. (2011). Use of Recycled Glass for Construction in Cyprus.

BEng Dissertation, University of Portsmouth, School of Civil Engineering and

Surveying, Portsmouth.

[13] Li, Z., Li, F., & Li, J. (1998). Properties of concrete incorporating rubber tire

particles. Magazine of Concrete Research, 50(4), 297-304.

References

P a g e | 49

[14] Ling, T., Nor, H., & Lim, S. (2010). Using recycled waste tires in concrete

paving blocks. 163(1), 37-45. doi:10.1680/warm.2010.163.1.37

[15] Mavroulidou, M., & Figueiredo, J. (2010). Discarded tire rubber as concrete

aggregate: a possible outlet for used tires. Global NEST Journal, 12(4), 359-

367.

[16] Nehdi, M., & Khan, A. (2001). Cementitious Composites Containing

Recycled Tire Rubber: An Overview of Engineering Properties and Potential

Applications. Cement, Concrete, and Aggregates, CCAGDP, 23(1), 3-10.

[17] Oikonomou, N., & Mavridou, S. (2009). The use of waste tire rubber in civil

engineering works. In J. Khatib, Sustainability of Construction Materials (pp.

213-238). Thessaloniki: CRC Press.

[18] Rafat, S., & Tarun, N. R. (2004). Properties of concrete containing scrap-tire

rubber – an overview. Waste Management, 24(6), 563-569.

doi:10.1016/j.wasman.2004.01.006

[19] Rostami, H., Lepore, J., Silverstraim, T., & Zundi, I. (2000). Use of Recycled

Rubber Tires in Concrete. International Conference on Concrete (pp. 391-

399). Dundee: University of Dundee, UK.

[20] Salam, A. (1992). Ultrasonic Pulse Velocity Versus Strength for Concrete in

Qatar. Engineering Jurnal of Qatar University, 5, 87-93.

[21] Segre, N., & Joekes, I. (2000). Use of tire rubber particles as addition to

cement paste. Cement and Concrete Research, 30(9), 1421-1425.

doi:10.1016/S0008-8846(00)00373-2

[22] Seyfu, K. A. (2010). The use of recycled rubber tires as a partial replacement

for coarse aggregates in concrete construction. MSc Thesis, Addis Ababa

University , Department of Civil Engineering.

[23] Tanatala, M. W., Lepore, J. A., & Zandi, I. (1996). Quasi-Elastic Behaviorof

Rubber Included Concrete Using Waste Rubber Tires. 12th International

Conference on Solid Waste.

[24] Teychenné, D. C., Franklin, R. E., & Erntroy, H. C. (1997). Design of Normal

Concrete Mixes (2nd ed.). Taylor & Francis.

[25] Topçu, B., & Avcular, N. (1997). Analysis of rubberized concrete as a

composite material. Cement and Concrete Research, 27(8), 1135-1139.

doi:10.1016/S0008-8846(97)00115-4

Appendix

P a g e | 50

Appendix

Table 12: Concrete mix design form.

Stage Item Reference of Calculation Values

1 1.1 Characteristic strength Specified 30 N/mm2 at 28 days

Proportion Defective 5 %

1.2 Standard deviation Figure 47 8 N/mm2 or no data__ N/mm2

1.3 Margin C1 or (k=1.64) 1.64 × 8 = 13.12 N/mm2

Specified __ N/mm2

1.4 Target mean strength C2 30 + 13.12 = 43.12 N/mm2

1.5 Cement type Specified OPC/SRPC/RHPC

1.6 Aggregate type: coarse Crushed/Uncrushed

Aggregate type: fine Crushed/Uncrushed

1.7 Free-water/cement ratio Figure 49, Figure 48 0.50

1.8 Maximum free-water/cement ratio Specified __

2 2.1 Slump or Vebe time Specified Slump 60-80 mm or Vebe time__s

2.2 Maximum aggregate size Specified 20 mm

2.3 Free-water content Figure 50 195 Kg/m3

3 3.1 Cement content C3 195 ÷ 0.5 = 390 Kg/m3

3.2 Maximum cement content Specified __ Kg/m3

3.3 Minimum cement content Specified __ Kg/m3

Use 3.1 if ≤ 3.2

Use 3.3 if > 3.1 390 Kg/m3

3.4 Modified free-water/cement ratio __

4 4.1 Relative density of aggregate (SSD) 2.6 known/assumed

4.2 Concrete density Figure 51 2350 Kg/m3

4.3 Total aggregate content C4 2350 – 195 – 390 = 1765 Kg/m3

5 5.1 Grading of fine aggregate Percentage passing 600μm sieve 60 %

5.2 Proportion of fine aggregate Figure 52 33 %

5.3 Fine aggregate content C5

0.33 × 1765 = 582 Kg/m3

5.4 Coarse aggregate content 1765 – 582 = 1183 Kg/m3

Figure 47: Relationship between standard deviation and characteristic strength.

Appendix

P a g e | 51

Figure 48: Relationship between compressive strength and free-water/ cement ratio.

Figure 49: Approximate compressive strength (N/mm2) of concrete mixes made with a free-

water/cement ratio of 0.5.

Appendix

P a g e | 52

Figure 50: Approximate free-water contents (kg/m3) required to give various levels of

workability.

Figure 51: Estimated wet density of fully compacted concrete.

Figure 52: Recommended proportions of fine aggregate according to percentage passing a

600 μm sieve.

Appendix

P a g e | 53

Table 13: Sieve Analysis.

Coarse Aggregate Sand Chipped Rubber Crumb Rubber

20mm 100mm

Sieve size

(mm)

Passing

%

Sieve size

(mm)

Passing

%

Sieve size

(mm)

Passing

%

Sieve size

(mm)

Passing

%

Sieve size

(mm)

Passing

%

31.5 100 20 100 10 100 20 100 2 100

20 90 14 99 5 96 14 90.35 1.18 99.8

14 36 10 87 2.36 77 10 37.1 0.6 18.8

10 8 5 2 1.18 65 6.3 5.7 0.425 9.8

5 1 2.36 0 0.6 58 5 1.7 0.3 2.6

2.36 0 0.3 37 3.35 0.2 0.212 0.9

0.15 4 1.18 0 0.15 0.2

0 0 0.063 0

Table 14: Water Absorption for Cubes.

Mix

Num.

Dry

Weight

(g)

Wet

Weight

(g)

Water

Abs.

(%)

Average

(%)

Comparison

with control

Mix (%)

Standard

Deviation

Average

+/-

Variance

1 2311 2349 1.64

1.69 0.034 1.73

1.66 2265 2304 1.72

2281 2320 1.71

2 2283 2317 1.49

1.46 -13.54 0.020 1.48

1.44 2290 2323 1.44

2263 2296 1.46

3 2238 2270 1.43

1.43 -15.41 0.046 1.48

1.39 2254 2285 1.38

2217 2250 1.49

4 2292 2320 1.22

1.24 -27.00 0.011 1.25

1.22 2244 2272 1.25

2265 2293 1.24

5 2263 2296 1.46

1.45 -14.04 0.026 1.48

1.43 2253 2285 1.42

2290 2324 1.48

Appendix

P a g e | 54

Table 15: Water Absorption for Cylinders.

Mix

Num.

Dry

Weight

(g)

Wet

Weight

(g)

Water

Abs.

(%)

Average

(%)

Comparison with

control Mix (%)

Standard

Deviation

Average +/-

Variance

1 3547 3595 1.35

1.35 0.013 1.36

1.34 3593 3642 1.36

3530 3577 1.33

2 3570 3614 1.23

1.22 -9.82 0.033 1.25

1.18 3528 3572 1.25

3586 3628 1.17

3 3524 3567 1.22

1.23 -8.58 0.013 1.25

1.22 3514 3558 1.25

3499 3542 1.23

4 3537 3573 1.02

1.01 -24.80 0.003 1.02

1.01 3560 3596 1.01

3545 3581 1.02

5 3571 3612 1.15

1.16 -13.95 0.012 1.17

1.15 3569 3611 1.18

3538 3579 1.16

Table 16: Water Absorption for Beams.

Mix

Num.

Dry

Weight

(g)

Wet

Weight

(g)

Water

Abs.

(%)

Average

(%)

Comparison with

control Mix (%)

Standard

Deviation

Average +/-

Variance

1 11773 11944 1.45

1.45 0.019 1.47

1.43 11437 11600 1.43

11694 11866 1.47

2 11806 11950 1.22

1.27 -12.10 0.039 1.31

1.24 11927 12083 1.31

11430 11578 1.29

3 11807 11949 1.20

1.20 -17.08 0.016 1.22

1.19 11216 11353 1.22

11678 11816 1.18

4 11616 11737 1.04

1.07 -26.49 0.023 1.09

1.04 11305 11429 1.10

11341 11461 1.06

5 11796 11932 1.15

1.17 -19.15 0.015 1.19

1.16 11339 11472 1.17

11263 11397 1.19

Appendix

P a g e | 55

Table 17: Cubes’ Compressive Strength.

Mix

Num.

Compressive

Strength (MPa)

Average

(%)

In comparison with

Control Mix (%) Standard

Deviation

Average

+/

Variance

1 43.50

43.56

0.95 44.52

42.61 44.76

42.43

2 41.74

40.53 -6.97 0.97 41.50

39.55 39.36

40.48

3 35.75

37.14 -17.31 2.37 39.50

34.77 40.47

35.19

4 40.03

39.49 -9.36 0.44 39.93

39.05 39.48

38.95

5 40.88

40.14 -7.86 1.64 41.78

38.50 41.68

37.86

Table 18: Flexural Strength Results.

Mix

Num.

Maximum

Load (KN)

Split Tensile

(MPa)

Average

(MPa)

In comparison

with Control

Mix (%)

Standard

Deviation

Average

+/

Variance

1 7.90 3.16

3.25 0.06 3.31

3.18 8.20 3.28

8.25 3.30

2 7.80 3.12

3.16 -2.55 0.03 3.20

3.13 8.00 3.20

7.93 3.17

3 8.00 3.20

3.02 -7.51 0.15 3.17

2.87 7.10 2.84

7.55 3.02

4 5.35 2.14

2.48 -23.61 0.24 2.72

2.24 6.65 2.66

6.60 2.64

5 8.20 3.28

3.15 -2.87 0.13 3.28

3.03 7.45 2.98

8.00 3.20

Appendix

P a g e | 56

Table 19: Results of elastic young’s modulus test.

Mix

Num.

Stress

(MPa) Strain

E Elastic

Young’s

Modulus (GPa)

Average

(GPa)

In comparison

with Control

Mix (%)

Standard

Deviation

Average

+/

Variance

1 13.52 0.000406 33.30

34.04

0.60 34.64

33.44 13.52 0.000397 34.06

13.52 0.000389 34.76

2 12.51 0.000460 27.19

27.03 -20.59 0.70 27.73

26.33 12.51 0.000479 26.11

12.51 0.000450 27.80

3 11.38 0.000456 24.95

25.46 -25.21 0.38 25.84

25.08 11.38 0.000440 25.86

11.38 0.000445 25.57

4 12.16 0.000400 30.41

26.20 -23.03 5.69 31.89

20.50 12.16 0.000405 30.03

12.16 0.000670 18.15

5 12.38 0.000320 38.69

34.07 -0.09 3.58 37.65

30.50 12.38 0.000369 33.55

12.38 0.000413 29.98

Table 20: Density of Cubes.

Mix

Num. Mass (g)

Mass into

water (g)

Density

(g/mL)

1 2311 1337 2.37

2265 1303 2.35

2281 1312 2.35

2 2283 1295 2.31

2290 1306 2.33

2263 1288 2.32

3 2238 1269 2.31

2254 1282 2.32

2217 1253 2.30

4 2292 1310 2.33

2244 1271 2.31

2265 1292 2.33

5 2263 1294 2.34

2253 1286 2.33

2290 1313 2.34

Appendix

P a g e | 57

Table 21: Cylinders’ compressive Strength after elastic young’s modulus test.

Mix

Num.

Compressive

Strength (MPa)

Average

(%)

In comparison with

Control Mix (%) Standard

Deviation

Average

+/

Variance

1 29.32

29.18

0.52 29.70

28.66 29.74

28.49

2 27.90

28.08 -5.62 1.02 29.10

27.05 26.92

29.41

3 27.22

25.83 -13.31 0.98 26.82

24.85 25.25

25.03

4 18.76

17.64 -54.96 4.73 22.36

12.91 22.78

11.37

5 27.40

27.20 -8.82 1.07 28.27

26.14 25.81

28.40

Table 22: UPV Results.

Mix

Num.

Density

(g/mL)

Time

(μs)

Velocity

(km/s)

Dynamic Elastic

Modulus Ed (GPa)

Average

(GPa)

In comparison

with Control Mix

(%)

Standard

Deviation

Average

+/

Variance

1 2.37 24.10 4.15 36.77

38.62 1.49 40.11

37.13 2.35 22.90 4.37 40.41

2.35 23.40 4.27 38.69

2 2.31 22.10 4.52 42.58

44.51 +15.24 1.48 45.98

43.03 2.33 21.30 4.69 46.17

2.32 21.60 4.63 44.77

3 2.31 21.20 4.72 46.25

46.26 +19.77 0.87 47.13

45.39 2.32 21.00 4.76 47.33

2.30 21.40 4.67 45.20

4 2.33 21.00 4.76 47.63

46.66 +20.82 0.68 47.35

45.98 2.31 21.20 4.72 46.18

2.33 21.30 4.69 46.18

5 2.34 21.00 4.76 47.66

47.08 +21.91 0.42 47.51

46.66 2.33 21.20 4.72 46.66

2.34 21.20 4.72 46.94