gichuru r w - use of crumb rubber in concrete

8/9/2019 Gichuru R W - Use of Crumb Rubber in Concrete

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Use of Crumb Rubber in Concrete

i

By Gichuru Rose Hannah Wanja

CIVIL ENGINEERING DEPARTMENT

FIFTH YEAR PROJECT REPORT

USE OF WASTE TYRES AS PARTIAL REPLACEMENT FOR FINE

AGGREGATES IN CONCRETE

By

GICHURU ROSE HANNAH WANJA

Bsc. CIVIL ENGINEERING

FIFTH YEAR

E25-0113/04

PROJECT SUPERVISOR

MR.KARIMI

Submitted in partial fulfillment of the award of Bachelor of Science Degree in Civil Engineering


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DECLARATION

“I Gichuru Rose Hannah Wanja do declare that this report is my original work and to the best of my knowledge, it

has not been submitted for any degree award in any University or Institution.”

Signed……………………… (Author) Date…………………………

CERTIFICATION

“I have read this report and approve it for my examination.”

Signed………………………… (Supervisor) Date …………………………..

MR. KARIMI


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ACKNOWLEDGEMENT

I would like to take this opportunity to thank those who have helped me complete my project successfully by

providing the technical information and ideas and in providing the materials I required. I apologize to anyone not

included and any errors on my part.

I would like to thank my supervisor Mr. Karimi for his guidance throughout the project. His comments and ideas

throughout the project period have helped make the project a success. Particular thanks to Mr. Kamami and

Mr.Karugu, who have selflessly extended help in the laboratory experiments.

I would also like to thank Car and General Retread for providing me with crumb rubber in adequate quantity.

Special thanks to my Mum and Dad (Mr. and Mrs. Gichuru) and friends Marylnn and Nabil for their support and

encouragement throughout the project. I am also grateful to the help extended by my classmates throughout my

course of Civil Engineering here in Jomo Kenyatta University of Agriculture and Technology. They have helped me

be the person I am today.


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TABLE OF CONTENTS

LIST OF TABLES .......................................................................................................................... 3

LIST OF FIGURES ........................................................................................................................ 4

CHAPTER ONE ............................................................................................................................. 5

1.0 INTRODUCTION .................................................................................................................... 5

1.1Background ............................................................................................................................ 5

1.2 Problem Justification ............................................................................................................. 6

1.3 Problem Statement ................................................................................................................ 6

1.4 Objectives. ............................................................................................................................. 6

1.5 Research Hypothesis ............................................................................................................. 6

1.6Limitation of the Study .......................................................................................................... 6

CHAPTER TWO ............................................................................................................................ 7

2.0LITERATURE REVIEW ....................................................................................................... 7

CHAPTER THREE ...................................................................................................................... 11

3.0RESEARCH METHODOLOGY............................................................................................. 11

3.1Collection and sampling of material .................................................................................... 11

3.2 Grading of materials for concrete production ..................................................................... 11

3.3Determination of specific gravity and water absorption of aggregates ................................ 13

3.4 Determination of mix design. .............................................................................................. 14

3.5Slump test ............................................................................................................................. 14

3.6Compressive Strength Test according to BS 1881-116:1983 .............................................. 14

3.7 Indirect Tensile Test according to BS1881-117:1983 ........................................................ 15

3.8Flexural Strength Test according to BS1881 ....................................................................... 16

CHAPTER FOUR ......................................................................................................................... 17


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4.0 DATA RESULTS AND ANALYSIS ................................................................................. 17

CHAPTER FIVE .......................................................................................................................... 35

5.0 DISCUSSION ..................................................................................................................... 35

CHAPTER 6 ................................................................................................................................. 37

6.0 CONCLUSION AND RECOMMENDATIONS ................................................................... 37

6.1 CONCLUSION ................................................................................................................... 37

6.2 RECOMMENDATIONS .................................................................................................... 37

APPENDIX ................................................................................................................................... 38

REFERENCES ............................................................................................................................. 46


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LIST OF TABLES

Table 1: Results on specific gravity of sand and rubber ................................................................................................................ 17

Table 2: Results on specific gravity of coarse aggregates ............................................................................................................... 18

Table 3: Results of coarse aggregate sieve analysis ........................................................................................................................ 19

Table 4: Results on sieve analysis of rubber .................................................................................................................................. 20

Table 5: Results on sieve analysis of fine aggregate ....................................................................................................................... 21

Table 6: Calculations on mix design ............................................................................................................................................... 23

Table 7: Data on compressive strength ........................................................................................................................................... 24

Table 8: Data on 28 day compressive strength ............................................................................................................................... 25

Table 9: Calculations on density of 150mm cubes at 28 days ......................................................................................................... 26

Table 10: Density of 150mm cubes at 28 days ............................................................................................................................... 26

Table 11: Data on Slump test .......................................................................................................................................................... 27

Table 12: Data on Indirect Tensile Strength ................................................................................................................................... 28

Table 13: Data on Indirect Tensile Strength ................................................................................................................................... 28

Table 14: Calculations of Density of 100mm by 200mm cylinders ................................................................................................ 29

Table 15: Density of 100mm by 200mm cylinders ......................................................................................................................... 29

Table 16: Data of Flexural Strength at 28 days ............................................................................................................................... 30

Table 17: Data of Flexural Strength at 28 days ............................................................................................................................... 30

Table 18: Data on water cement ratio ............................................................................................................................................. 31

Table 19: Data on Flexural Strength-Load, Stress, Deflection and Strain ...................................................................................... 32


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LIST OF FIGURES

Figure 1: Sieves during sieve analysis ............................................................................................................................................ 12

Figure 2: Graph of Sieve Analysis of coarse aggregate .................................................................................................................. 19

Figure 3: Graph of sieve analysis of rubber .................................................................................................................................... 20

Figure 4: Graph of sieve analysis of fine aggregate ........................................................................................................................ 21

Figure 5: Bar chart of 7 day compressive strength .......................................................................................................................... 24

Figure 6: Bar chart of 28 day compressive strength ........................................................................................................................ 25

Figure 7: Bar chart of density of 150mm cubes at 28 days ............................................................................................................. 26

Figure 8: Bar chart of slump ........................................................................................................................................................... 27

Figure 9: Bar chart of Indirect Tensile Strength ............................................................................................................................. 28

Figure 10: Bar chart of density of 100 by 100 mm cylinders .......................................................................................................... 29

Figure 11: Bar chart of Flexural Strength at 28 days ...................................................................................................................... 30

Figure 12: Line graph of water cement ratio ................................................................................................................................... 31

Figure 13: Multiple line graph of Deflection against Load ............................................................................................................. 33

Figure 14: Multiple line graph of Stress against Strain ................................................................................................................... 34

Figure 15: 25% Replacement Rubberised concrete ........................................................................................................................ 38

Figure 16: 15% Replacement Rubberized Concrete ....................................................................................................................... 38

Figure 17: Cylinder specimens 15% and 25% replacement ............................................................................................................ 39

Figure 18: Cube specimen 15% replacement under compression ................................................................................................... 39

Figure 19: Cylinder specimen 25% replacement under tension ...................................................................................................... 40

Figure 20: Cylinder specimen failed in tension............................................................................................................................... 40

Figure 21: 25% replacement beam specimen ready for flexural test ............................................................................................... 41

Figure 22: Placing the strain gauges to determine strain and deflection ......................................................................................... 41

Figure 23: Failure of rubberized concrete ....................................................................................................................................... 42

Figure 24: Charts used for calculating mix design .......................................................................................................................... 43

Figure 25: Charts used in calculating mix design ........................................................................................................................... 44

Figure 26: Charts used in calculating mix design ........................................................................................................................... 45


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CHAPTER ONE

1.0 INTRODUCTION

1.1Background

The research will focus on the use of waste tyres as partial replacement for fine aggregates in concrete. It will

investigate engineering properties of concrete containing rubber aggregate and the potential of rubberized concrete

in various civil engineering applications.

The economy of Kenya is continuing to grow and urbanization is on the increase. This means the quantity of waste

tyres will be on the rise. The waste tyres will come from the construction industry and the consumer industry. Hence

significant emphasis will be placed on the use of these recycled products if not already. For Portland cement

concrete, rubber from granulated tires may be used as an elastic aggregate modifying the brittle failure of concrete

and increasing its ability to absorb higher amounts of energy before failure. The use of fine graded rubber as partial

replacement of fine aggregates may produce a ductile behavior with large deformations prior to full disintegration of

concrete and affect to a lesser degree the strength loss.

Research is currently ongoing to evaluate the effects of incorporating crumb rubber, very fine tire rubber particles,

into Portland cement concrete. The objective of the study has been to evaluate the effects of rubber aggregate on

Portland cement concrete (PCC) properties. Initially, the rubber content replacing fine aggregates into the concrete

mix was investigated by examining the concrete failure characteristics and the amount of energy absorbed during

testing. The destructive testing results of the rubber-filled concrete were then coupled with nondestructive testing

(NDT) evaluation. The scope of this effort was first to use a well-accepted NDT method for evaluating this specific

PCC type, and second, to correlate strength and static elastic modulus to parameters evaluated from the dynamic

NDT testing. These relationships may be used for estimating concrete strength and static elastic modulus from NDT

results. Nondestructive testing techniques are relatively simple and quick to perform and provide the advantage of

using the same samples again and again. NDT techniques are also of particular value in quality control testing.

Several advantageous properties can be realized with the rubberized concrete. The inclusion of the rubber into the

concrete mixture provides for a finished concrete composite having a lower density. This decrease in the density of

the concrete is further enhanced by the inclusion of the fly ash component. The resulting concrete composite is thus

lighter and would increase the live load capacity of the rubberized included concrete (RIC). The RIC also provides a

more ductile composite than conventional concrete. The RIC can also be utilized as a composite for noise barrier

applications and also in applications requiring improved heat insulation, vibration dampening, toughness, and

impact resistance.


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1.2 Problem Justification

The study hopes to come up with rubberized concrete that is semi-rigid and less brittle. The study also hopes to

come up with a potential solution to management of waste tyres by using it as an additive to concrete to improve

some of its properties.

1.3 Problem Statement

Concrete as a construction material is rigid and exhibits brittle failure on loading and on exposure to high

temperatures. The use of fine rubber (crumb rubber) as partial replacement for fine aggregate in concrete hope to

come up with concrete that is semi-rigid and is less brittle. Disposal of waste tyres is a problem. Use of fine rubber

in concrete hopes to come up with a solution to management of waste tyres.

1.4 Objectives.

Main objective.

To use waste tyres in the form of crumb rubber as partial replacement for fine aggregates in concrete.

Specific objectives

To study the material (concrete constituents and crumb rubber) characteristics.

To determine the appropriate mix design.

To study the failure characteristics of Rubberized Concrete.

1.5 Research Hypothesis

The use of crumb rubber in concrete seeks to make concrete semi-rigid and solve a waste disposal problem.

1.6Limitation of the Study

Assessment of the long term characteristics of rub-crete (rubberized concrete) because of the short term duration of

the project.


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CHAPTER TWO

2.0LITERATURE REVIEW

One of the major environmental challenges facing municipalities around the world is the disposal of worn

out auto-mobile tyres. To address this global problem, several studies have been conducted to examine various

applications of recycled tyre rubber (fine crumb rubber). Emphasis has been placed on the use of recycled tyre

rubber in Portland cement concrete. Preliminary studies show that workable rubberized Portland cement concrete

(rubcrete) mixtures can be made provided that appropriate percentages of tire rubber are used in such mixtures.

Achievements in this area have been examined with special focus on engineering properties of rubcrete. These

include: workability, compressive strength, split-tensile strength, flexural strength, elastic modulus, Poisson’s ratio,

toughness. The practice of disposing of scrap tyres in landfills is becoming unacceptable because of the rapiddepletion of available sites for waste disposal. Moreover, tyres can even “rise from the grave”— floating upward

through a sea of trash to break through landfill covers — sometimes with explosive force (Tantala et al. 1996).

Not much attention has been given to the use of rubber from scrap tyres in Portland cement concrete (PCC)

mixtures, particularly for highway applications. However, large benefits can result from the use of worn-out tire

rubber in PCC mixtures, especially in circumstances where properties like lower density, increased toughness and

ductility are desired. The use of recycled tyre rubber in PCC mixtures would not only make good use of an

otherwise waste material and help alleviate disposal problems, but can also improve certain properties of concrete

for particular design applications. It would also address the growing public concern about the need to preserve

natural resources (such as aggregates) used in the production of concrete that are depleting rapidly due to excessive

quarrying.

Properties of Fresh Concrete

Slump

Khatib and Bayomy (1999) investigated the workability of rubcrete mixtures. They observed a decrease in slump

with increased rubber content by total aggregate volume. Their results show that at rubber contents of 40% by total

aggregate volume, the slump was near 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 tire chips or a combination of crumb rubber and tire chips.

Unit Weight

Due to the low specific gravity of rubber, the unit weight of rubcrete mixtures decreases as the percentage of rubber

increases. In addition, the increase in rubber content increases the air content, which in turn further reduces the unit

weight (Fedroff 1995). However, the decrease is almost negligible for rubber contents lower than 10 to 20% of the


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total aggregate volume. Unit weight versus rubber addition for rubberized concrete fits a straight-line curve when

fine crumb rubber, is used as fine aggregate replacement in concrete.

Mechanical Strength

The compressive strength of rubberized concretes was studied using different sizes and shapes of specimens.

Cylindrical specimens of 75, 100, or 150 mm in diameter were used by Rostami et

al. (1993), Ali et al. (1993), and Eldin and Senouci (1993), respectively. Topcu (1995) used both 150 mm diameter

cylinders and 150mm cubes. Results of various studies indicate that the mechanical strength of rubcrete mixtures is

greatly affected by the size, proportion, and surface texture of rubber particles and the type of cement used in such

mixtures.

Effect of Rubber Content and Particle Size

Various published results show that coarse grading of rubber granules lowered the compressive strength of rubcrete

mixtures more than fine grading.

Mechanisms of Strength Reduction

Khatib and Bayomy (1999) found that the 28-day compressive strength of rubcrete mixtures was reduced by about

93% when 100% of the coarse aggregate volume was replaced by rubber and by 90% when 100% of the fine

aggregate volume was replaced by rubber. They hypothesized that there are three major causes for this strength

reduction. First, because rubber is much softer than the surrounding cement paste, upon loading, cracks are initiated

quickly around the rubber particles due to this elastic mismatch, which propagate to bring about failure of the

rubber-cement matrix. Second, due to weak bonding between the rubber particles and the cement paste, soft rubber

particles may be viewed as voids in the concrete mix. The assumed increase in the void content would certainly

cause a reduction in strength. The third possible reason for the reduction in strength is that the strength of concrete

depends greatly on the density, size, and hardness of the coarse aggregate (Mehta and Monteiro 1993). Because

aggregates are partially replaced with relatively weaker rubber, a reduction in strength is anticipated. It was also

found (Khatib and Bayomy 1999) that the flexural strength of rubcrete mixtures decreased with an increase in the

rubber content in a fashion similar to that observed for compressive strength, perhaps due to similar mechanisms.

Toughness and Failure Mode

Although the reduction in strength of rubcrete mixtures may limit their use in some structural applications,

one can rather appreciate their future potential in their enhanced toughness and failure mode. Eldin and Senouci

(1993) showed that when loaded in compression, specimens containing rubber did not exhibit brittle failure. The

generated tensile stress concentrations at the top and bottom of the rubber aggregates result in many tensile

microcracks that form along the tested specimen (Fig. 6b). These microcracks will rapidly propagate in the cement

paste until they encounter a rubber aggregate. Because of their ability to withstand large tensile deformations, the

rubber particles will act as springs, delaying the widening of cracks and preventing full disintegration of the concrete

mass. The continuous application of the compressive load will cause generation of more cracks as well as widening


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of existing ones. During this process, the failing specimen is capable of absorbing significant plastic energy and

withstanding large deformations without full disintegration. This process will continue until the stresses overcome

the bond between the cement paste and the rubber aggregates. Biel and Lee (1996) reported that the failure of plain

concrete cylinders resulted in explosive conical separations of cylinders, leaving the specimens in several pieces. As

the amount of rubber in concrete was increased, the severity and explosiveness of the failures decreased. Failure of

concrete specimens with 30, 45, and 60%replacement of fine aggregate with rubber particles occurred as a gradual

shear that resulted in a diagonal failure plane. The cylinders did not separate and continued to sustain load after the

initial failure. Upon release of the load, the cylinders rebounded back to near their original shape. The samples

containing 75 and 90% fine aggregate substitution with rubber failed through a gradual compression that appeared

like a true crushing, resulting in a post failure material that was sponge-like and elastic in nature. In another

experimental study conducted by Goulias and Ali (1997), it was found that the dynamic moduli of elasticity and

rigidity decreased with an increase in the rubber content, indicating that a less stiff and less brittle material was

obtained. Results of Poisson’s ratio measurements indicated that cylinders with 20% rubber had a larger ratio of

lateral strain to the corresponding axial strain than that of 30% rubber concrete cylinders (Goulias and Ali 1997a). Itwas also found (Goulias and Ali1997) that the higher the rubber content, the higher the ratio of the dynamic

modulus of elasticity to the static modulus of elasticity. The dynamic modulus was then related to compressive

strength, providing a high degree of correlation between the two parameters. This suggests that nondestructive

measurements of the dynamic modulus of elasticity may be used for estimating the compressive strength of rubcrete.

A good correlation between compressive strength and the damping coefficient calculated from transverse frequency

was also found, indicating that the damping coefficient of rubcrete may likewise be used for predicting the

compressive strength. Khatib and Bayomy (1999) observed that as the rubber content increased, rubcrete specimens

tended to fail gradually in either a conical or columnar shape failure mode. The samples sustained much higher

deformations than the control mix without rubber. With a rubber content of 60% by total aggregate volume (fine),

the samples exhibited significant elastic deformation, which was retained upon unloading. Thus, flexibility and

ability to deform at peak load were increased significantly by rubber addition. Experimental results of Schimizze et

al. (1994) showed that the elastic modulus of a concrete mixture containing fine rubber granules replacing 100% of

the fine aggregate volume, the elastic modulus was reduced to about 47% of that of the control mixture. The

reduction in the elastic modulus indicates higher flexibility, which may be viewed as a positive gain in rubcrete

mixtures that could be used in stabilized base layers of flexible pavements. Raghavan et al. (1998) conducted an

experimental study on the use of rubber shreds and in mortar. They found that mortar specimens with rubber shreds

were able to withstand additional load after peak load. The specimens did not physically separate into two pieces

under flexural loading because of bridging of cracks by rubber shreds. The post-crack strength seemed to improve

when rubber shreds were used.


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Concluding Remarks

Although a rubcrete mixture generally has a reduced compressive strength that may limit its use in certain structural

applications, it possesses a number of desirable properties, such as lower den-sity, higher toughness, enhanced

ductility, compared to conventional concrete. Such engineering properties are advantageous for various construction

applications. If rubcrete is used to its potential in projects that require these unique attributes, this can con-tribute to

alleviating the exacerbated solid waste disposal problems associated with worn out rubber tires. However, this

requires a paradigm shift from the traditional misconception that the most important property of concrete is its

compressive strength to a design by function approach, which will allow rubcrete to be viewed as a preferred

solution over conventional concrete for particular projects. Structural applications involving rubcrete may still be

possible if appropriate percentages of rubber aggregates are used. Further research is still needed to optimize the

effect of the percentage of rubber and particle size distribution. Rubcrete mixtures usually absorb significant plastic

energy and undergo relatively large deformations without full disintegration. This property can be utilized in various

structural and geotechnical projects in which the deformation at peak load is a primary design concern. Using

rubcrete as a flexible sub-base for pavements, as pipe bedding, for tunnel linings, and other major construction workhas the potential to make good use of the billions of worn-out tire stockpiled worldwide. However, further studies

are needed before one can draw final recommendations and set forth design guidelines for such applications.


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CHAPTER THREE

3.0RESEARCH METHODOLOGY

Assessment of material properties (of cement, of coarse aggregate, of fine aggregate, and of crumb rubber)

by carrying out the following activities: sampling, sieve analysis, specific gravity and water absorption

tests.

Determination of appropriate mix design.

Carrying out laboratory tests

Compressive test using a 150 by 150 by 150mm cube mould as per BS 1881

Flexural test using 150 by 150 by 500mm beam

Indirect tensile test using concrete cylinders of 100mm diameter by 200mm height as per BS 1881

3.1Collection and sampling of material

Rubber was obtained from Car and General in South B. The aggregates were in plentiful supply at the workshop.

The fine and coarse aggregates were in plentiful supply at the workshop. The cement that was used to make the

control cubes was Blue triangle cement purchased from suppliers at Juja.

Coarse aggregates of sizes 20mm were used for the study.

The aggregates were dried to reduce the amount of water contained so as not to affect the mix design.

3.2 Grading of materials for concrete production

The coarse and fine aggregates were graded in accordance with BS5238.


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Figure 1: Sieves during sieve analysis

Objective

Grading was carried out to determine the particle size distribution of aggregates by sieving.

Apparatus

i.

Balance accurate to 0.5% of mass of test sample.

ii. Test sieves

iii.

Oven capable of maintaining constant temperature to within 5%

iv.

Mechanism of shaking sieves.

v. Chart for recording results.

vi. Sieve sizes

Coarse aggregates: 50mm, 37.5mm, 20mm, 14mm, 10mm, 5mm and 2.36mm.

Fine aggregates: 10mm, 5mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm and 0.15mm


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Procedure

The test sample was dried to a constant mass by oven drying at not more than 105±5ºC.The sieves were

checked to ensure that they were clean and dry. The required sample was then weighed. The sieve with the largest

mesh size was made to stand in the tray and the weighed test sample was put in the sieve. Continuous horizontal

shaking of the sieve was carried out for at least 2minutes until no more sample was seen to pass. The retained

material was weighed. Results were tabulated in a table and the cumulative weight passing each sieve as a

percentage of the total sample was calculated. The grading curve for the sample was plotted in the grading chart.

3.3Determination of specific gravity and water absorption of aggregates

a. For fine aggregates.

Objective

This test was carried out to determine the specific gravity and the water absorption values of aggregates..

Apparatus

i. A balance

ii. A drying oven

iii.

A pycometer bottle

iv. Sample containers

v.

Stirring rod

Procedure.

A sample of aggregates less than 5mm was used. The sample was thoroughly washed to remove allmaterial finer than 0.075mm.The washed sample was placed in a tray and water added until the sample was

completely immersed. The sample was left immersed for 24hours. After 24 hours the water was drained by

decantation through a 0.075mm sieve .The sample was then exposed to a gentle current of warm air to evaporate

surface moisture. The saturated and surface dry sample was weighed. Some of the wet sample was placed in a tray

and dried in the oven at temperature of 104-105ºC for 24hours, then cooled and weighed. The empty pycometer was

then weighed. The weight of pycometer+sample was taken. The pycometer containing a sample was filled with

water until no air was entrapped then weighed. The pycometer was then emptied of its contents, filled with water

then weighed.


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b. For coarse aggregates

Apparatus

(i) Double beam balance of capacity 5kg

(ii)

Container of steel or enameled iron with rubber plate.

(iii)

Wire basket of opening 3mm or less, dia 20 cm and height 20 cm.

Procedure

A representative sample was obtained and weighed to the nearest 0.5kg(Ws).The sample was then placed in the wire

basket and immersed in water at room temperature and the weight taken.(Ww).The sample was removed from the

water and dried to constant weight at a temperature of 105ºC then cooled and the weight taken(Wd).

3.4 Determination of mix design.

The class that would be used in the project was chosen. Class 20 was chosen as the design strength of concrete that

would be used in the project. The target mean strength was obtained using standard deviation and margin

parameters. The aggregate was selected as crushed for coarse aggregate and uncrushed for fine aggregate. The free

water/cement ratio was selected from the charts. The data compiled was then used to come up with the appropriate

mix design.

3.5Slump test

Apparatus

(i)

Mould

(ii) Tamping rod

Procedure

The slump test was carried out in accordance with BS1881-102. The mould was filled in three equal layers and each

layer tamped 25 times with a tamping rod before the consecutive layers were placed and the reading taken(initial

reading).Surplus concrete above the top edge of the mould was struck off with the tamping rod. The cone was then

lifted vertically and the reading taken(final reading). The value of the slump was obtained by getting the difference

between the final reading and the initial reading.

3.6Compressive Strength Test according to BS 1881-116:1983

Apparatus

(i) Cubical moulds (150mm by 150mm by150mm)

(ii)

Compression Testing machine

(iii)

Weighing machine


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(iv)

Mixing trough

(v)

Spade

(vi)

Trowel

(vii) Vibrator

Procedure

Using the appropriate proportions of water, cement, sand, coarse aggregate and rubber aggregates from the worked

out mix design the mix was prepared in the mixing trough. The control mix and the rubberized concrete mix were

prepared. The mix was placed in the moulds in layers using the trowel and each layer compacted with the vibrator.

When the moulds had been filled the top layer was struck off to come up with a well finished surface. The

specimens were stored in a moist atmosphere for 24 hours and the removed from the moulds and stored in a curing

sink for 28 days. After 28 days the specimens were removed from their wet storage and tested using the compression

testing machine. The compressive strength was obtained by calculations using the formula

f c=F/Acfc is the compressive strength in N/mm²

F is the maximum load at failure in Newtons

Ac is the cross sectional area of the specimen on which the compressive force acts, calculated from the

designated size of the specimen.

3.7 Indirect Tensile Test according to BS1881-117:1983

Apparatus

(i)

Cylindrical moulds (100mm by 200mm)(ii)

Compression Testing Machine

(iii)

Weighing machine

(iv) Mixing Trough

(v)

Spade

(vi)

Trowel

(vii) Vibrator

Procedure

The appropriate proportions of water, cement, sand, coarse aggregate and fine rubber aggregate according to the

calculated mix design were used to come up with a control and rubberized concrete mix. The mix was then placed inthe moulds using the trowel. This was done in layers and compaction was carried out after each layer using a

vibrator. After filling the moulds the top of the moulds was leveled and finishing done. The moulds were left in a

moist atmosphere for 24 hours. After 24 hours the specimens were removed from the moulds and stored in a curing

sink for 28 days until strength testing. The specimens were removed from the curing sink after 28 days and

subjected to indirect tensile testing using the compression testing machine.

From the maximum applied load at failure the indirect tensile strength was calculated as follows


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б= 2F/п*l*d

б is the indirect tensile strength in N/mm².

F is the maximum applied load in N.

l is the length of cylinder in mm.

d is diameter in mm.

3.8Flexural Strength Test according to BS1881

Apparatus

Beam moulds (150mm by 150mm by 500mm)

Avery Universal Machine

Weighing machine

Mixing TroughSpade

Trowel

Vibrator

Procedure

Using the appropriate proportions of cement, fine aggregate, coarse aggregate and rubber the control mix and the

rubberized concrete mix was prepared in the mixing trough. The mix was placed in the beam moulds in layers and

each layer compacted well using a vibrator before another layer was added. The moulds were filled and the surface

leveled until a smooth surface was obtained. The moulds were stored under moist conditions for 24 hours and then

the specimens were removed from the moulds and placed in a curing sink for 28 days until strength testing. After 28

days the specimens were removed from the curing sink and flexural test was carried out using the Avery Universal

Machine. The load was applied through two rollers at the third points of the span until the specimen broke. Using

standard beam formulae, the failure stress was calculated from the beam dimensions and the failure load.

M= W*l/b*d²

W is the maximum applied load in N/mm²

l is the length of the beam

b is the breadth of the beam

d is the depth of the beam

Strain gauges were placed across the centre of the beam to measure the strain and deflection.


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CHAPTER FOUR

4.0 DATA RESULTS AND ANALYSIS

Specific Gravity and Water Absorption of Ordinary Sand and Rubber

Ordinary Sand Rubber

Sample A Sample B

Weight of jar+sample+water……………………...A 1706 1384

Weight of jar+water……………………………….B 1417 1406

Weight of saturated surface dry sample………..….C 460 64.5

Weight of oven dried sample………………………D 457.5 62.5

Specific gravity on an oven dried basis

……........................... D/C-(A-B)

2.68 0.727

Specific gravity on a saturated and surface dried basis

C/C-(A-B)

2.69 0.746

Apparent specific gravity……………... D/D-(A-B) 2.71 0.74

Water absorption (% dry mass)………. 100(C-D)/D 0.55 3.2

Table 1: Results on specific gravity of sand and rubber


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Specific Gravity and Water Absorption of Granite Coarse Aggregates

Granite Coarse Aggregates

A B

Weight of wire basket………………………………….a 420 417

Weight of wire basket+ aggregate……………………. b 1015 1020

Weight of aggregate in water……………….. (a+b) Ww 595 603

Weight of saturated surface dry sample…………. Ws 983.5 1003

Weight of oven dried sample……………………. Wd 963 984

Specific gravity on saturated surface dry basis…Ws/Ws-Ww 2.53 2.51

Absolute dry specific gravity…………………… Wd/Ws-Ww 2.36 2.46

Water Absorption (% of dry weight)…………… Ws-Wd/Wd 2.1 1.9

Table 2: Results on specific gravity of coarse aggregates


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Coarse Aggregate Sieve Analysis

Sieve sizes(mm)

Wt. retained(g)

Wt. passing(g)

% retained Cumulative %retained

Cumulative % passing

50 0 5399.5 0.00 0.00 100.00

38.1 0 5399.5 0.00 0.00 100.00

20 1184 4215.5 21.93 21.93 78.07

15 984 3231.5 18.22 40.15 59.85

10 1698 1533.5 31.45 71.60 28.40

5 636.5 897.0 11.79 83.39 16.61

2.36 42 855.0 0.78 84.17 15.83


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Sieve Analysis of Rubber

Sieve size(mm) Weight retained(g) Weight passing(g) % retained % passing

9.5 0 767.5 0

4.75 0 767.5 0 100

2.38 132 635.5 17.2 82.8

1.2 198.5 437 31.2 68.8

0.6 172.5 264.5 39.5 60.5

0.3 132.5 132 50.09 49.91

0.149 132 0 0 0

total 767.5

Table 4: Results on sieve analysis of rubber

Figure 3: Graph of sieve analysis of rubber


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Fine Aggregate Sieve Analysis Results

Sieve sizes

(mm)

Wt. retained

(g)

Wt. passing

(g)

% retained Cumulative %

retained

Cumulative %

passing

5.0 40.5 1496.00 2.64 2.64 97.36

2.0 47.0 1449.00 3.06 5.69 94.31

1.2 210.0 1239.00 13.67 19.36 80.64

0.6 419.5 819.50 27.30 46.66 53.34

0.3 537.0 282.50 34.95 81.61 18.39

0.2 215.5 67.00 14.03 95.64 4.36

0.1 67.0 0.00 4.36 100.00 0.00

Table 5: Results on sieve analysis of fine aggregate

Figure 4: Graph of sieve analysis of fine aggregate


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MIX DESIGN.

Target mean strength 20N/mm2 at 28days

Proportion defective 10%

Standard deviation 8 N/mm2

Margin (k=1.96) 1.96*8 16 N/mm2

Specified

Target mean strength 20+16 36N/mm2

Cement type specified OPC

Aggregate: coarse crushed

Aggregate: fine uncrushed

Free water/cement ratio Table 2,Fig 4 0.58

Slump 10-30

Maximum aggregate 20mm

Free water content Table 3 190kg/m3

Cement content C 3 190÷0.58 330kg/m3

Maximum cement content specified …….kg/m3

Minimum cement content specified 290kg/m3

Relative density of aggregate 2.7assumed

Concrete density 2400kg/m3

Total aggregate content 2400-330-190 1880kg/m3

Grading of fine aggregate %passing 600um sieve 54%

Proportion of fine aggregate Fig 6 46%

Fine aggregate content 1880*0.46 860

Coarse aggregate content 1880*860 1020

Quantities Cement(kg) Water Fine aggregate Coarse aggregate

10mm 20mm


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Per m3(2

Nearest 5kg) 330 190 860 340 680

Per trial mix(0.003)m3 1.1 0.64 2.9 1.15 3.0

N/B 1.Allow for 20% shrinkage

2.Allow for 20% waste

Table 6: Calculations on mix design


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7 Day Compressive Strength in N/mm² for 150 by 150 by 150mm cube

7 day compressive strength in N/mm² f c =F/A Percentage replacement

35*10 / 150² = 16 0%

18*10 / 150² = 8 15%

7*104 / 150² = 3 25%

Table 7: Data on compressive strength

Figure 5: Bar chart of 7 day compressive strength


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28 Day Compressive Strength in N/mm² for 150 by 150 by150mm cube

28 Day Compressive Strength in N/mm² f c=F/A Percentage replacement

48.5*10 /150 = 21.56 0%

23*10 / 150² = 10.22 15%

12*104 /150² = 5.33 25%

Table 8: Data on 28 day compressive strength

Figure 6: Bar chart of 28 day compressive strength


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Density of 150 by 150 by 150mm cube at 28 days

Mass Mass in kg Volume Density

8058 8.058 0.15*0.15*0.15=0.00375 8.058/0.00375=2387.56

7876 7.876 0.15*0.15*0.15=0.00375 7.876/0.00375=2333.63

7298 7.298 0.15*0.15*0.15=0.00375 7.298/0.00375=2162.37

Table 9: Calculations on density of 150mm cubes at 28 days

Density (kg/m3) Percentage replacement (%)

2387.56 0%

2333.63 15%

2162.37 25%

Table 10: Density of 150mm cubes at 28 days

Figure 7: Bar chart of density of 150mm cubes at 28 days


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Slump (mm)

Slump Percentage Replacement

13 0%

10 15%

6 25%

Table 11: Data on Slump test

Figure 8: Bar chart of slump


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28 day indirect tensile strength (N/mm2) using 100mm by 200mm cylinder

28 Day Indirect Tensile Str ength б = 2F/ п*l*d Percentage Replacement %

80000/ п*200*100 = 1.273 0%

50000/ п*200*100 = 0.796 15%

4000/ п*200*100 = 0.064 25%

Table 12: Data on Indirect Tensile Strength

28 days Indirect Tensile Strength (N/mm2) Percentage replacement

1.273 0%

0.796 15%

0.064 25%

Table 13: Data on Indirect Tensile Strength

Figure 9: Bar chart of Indirect Tensile Strength


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Density of 100mm by 200 mm cylinder at 28 days

Mass (g) Mass in kg Volume Density

3518 3.518 3.14*(0.05)²*0.2=0.0016 3.518/0.0016= 2198.75

3294.5 3.295 3.14*(0.05)²*0.2=0.0016 3.295/0.0016= 2059.38

2752.0 2.752 3.14*(0.05)²*0.2=0.0016 2.752/0.0016= 1720

Table 14: Calculations of Density of 100mm by 200mm cylinders

Density Percentage Replacement

2198.75 0%

2059.38 15%

1720 25%

Table 15: Density of 100mm by 200mm cylinders

Figure 10: Bar chart of density of 100 by 100 mm cylinders


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Flexural Strength at 28 days of 150mm by 150mm by 500mm beam.

28 Day Flexural Strength in N/mm² M= W*l/ b*d² Percentage replacement

2.08*10 *500/150*150² =3.08 0%

2.7*10 *500/ 150*150² =4.0 15%

2.44*10 *500/ 150*150² =3.61 25%

Table 16: Data of Flexural Strength at 28 days

Flexural Strength (N/mm2) Percentage Replacement

3.08 0%

4.0 15%

3.61 25%

Table 17: Data of Flexural Strength at 28 days

Figure 11: Bar chart of Flexural Strength at 28 days


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WATER CEMENT RATIO PER 0.003M³

Water Cement Ratio Percentage Replacement

0.64 0%

0.74 15%

0.8 25%

Table 18: Data on water cement ratio

Figure 12: Line graph of water cement ratio


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FLEXURAL TEST-STRESS STRAIN CURVES AND LOAD DEFLECTION CURVES

Normal concrete 15% Replacement 25% Replacement

Load in

tonnes

Stressin

N/mm²

Deflection

in mm

Strain

in mm

Load

in

tonnes

Stress

in

N/mm²

Deflection

in mm

Strain

in mm

Load

in

tonnes

Stress

in

N/mm²

Deflection

in mm

Strain

in mm

0.11 0.16 0.04 0.8 0.14 0.21 0.03 0.68 0.22 0.33 0.03 0.6

0.25 0.37 0.04 4 0.33 0.49 0.03 3.4 0.38 0.57 0.03 3

0.34 0.5 0.04 5.6 0.44 0.65 0.03 4.8 0.48 0.71 0.03 4.2

0.48 0.71 0.04 8 0.62 0.92 0.03 6.8 0.54 0.8 0.03 6

0.58 0.86 0.08 9.6 0.75 1.11 0.07 8.2 0.65 0.96 0.06 7.2

0.7 1.04 0.16 12.8 0.91 1.35 0.14 10.9 0.79 1.17 0.12 9.6

0.81 1.2 0.24 18.4 1.05 1.56 0.2 15.6 1.01 1.5 0.18 13.8

0.93 1.38 0.32 22.4 1.21 1.79 0.27 19.04 1.15 1.7 0.24 16.8

1.02 1.51 0.44 28 1.33 1.97 0.37 23.8 1.25 1.85 0.33 21

1.13 1.67 0.52 31.2 1.47 2.18 0.44 26.5 1.37 2.03 0.39 23.4

1.26 1.87 0.64 38.4 1.64 2.43 0.54 32.6 1.52 2.25 0.48 28.8

1.38 2.04 0.68 43.2 1.79 2.65 0.58 36.7 1.65 2.44 0.51 32.4

1.5 2.22 0.8 47.2 1.95 2.89 0.68 40.1 1.79 2.65 0.6 35.4

1.62 2.4 0.84 52 2.11 3.13 0.71 44.2 1.9 2.81 0.63 39

1.85 2.74 0.92 50.4 2.41 3.57 0.78 42.8 2.18 3.23 0.69 37.8

1.94 2.87 1 51.2 2.52 3.73 0.85 43.5 2.28 3.38 0.75 38.4

2.08 3.08 1 51.2 2.7 4 0.85 43.5 2.44 3.61 0.75 38.4

Table 19: Data on Flexural Strength-Load, Stress, Deflection and Strain


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Figure 13: Multiple line graph of Deflection against Load


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Figure 14: Multiple line graph of Stress against Strain


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CHAPTER FIVE

5.0 DISCUSSION

Sieve Analysis

The sieving operation was performed by hand with each sieve in turn being shaken until no more than a trace

continues to pass. The shaking was in all directions so that particles could pass through the sieve.

Fine Aggregates

The fine aggregate (sand) was aggregate passing a 5mm BS 410 sieve.

Coarse Aggregate

This was aggregate of sizes between 5mm to 20mm.

Crumb Rubber

The grading of the crumb rubber was similar to that of fine aggregate. It was aggregate passing a 5mm BS 410 sieve.

Specific Gravity

Ordinary Sand-oven dry- was 2.68

-Surface dry-was 2.69

Rubber-oven dry-was 0.727

-Surface dry-was 0.746

Coarse aggregate-surface dry-was an average of 2.32

-Absolute dry specific gravity was an average of 2.41

Water Absorption (% of dry weight)

Ordinary sand was 0.55

Rubber was 3.2

Coarse aggregate was an average of 2


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Aesthetics

The appearance of the finished surface of rubberized concrete was similar to that of ordinary concrete. The colour of

rubberized concrete did not differ noticeably from that of ordinary concrete however the higher the percentage of

crumb rubber the darker the colour of rubberized concrete.

Workability

There was a decrease in slump with increase in crumb rubber content. The slump of the control mix was 13mm. The

water content increased with increase in percentage substitution.

Concrete Density

There was a decrease in Concrete density when fine aggregates were replaced with crumb rubber. The density of the

control cube at 28 days was approximately 2388 kg/m³. The decrease in density with addition of crumb rubber could

be as a result of the replacement of rigid and bulky aggregate with light weight rubber aggregate.

Compressive Strength and Tensile Strength

The compressive and tensile strength of concrete reduced with increase in percentage replacement of fine aggregate

with crumb rubber. This decrease in strength could be due to the replacement of high strength and stiff aggregate

with low strength and highly elastic crumb rubber. When loaded in compression, specimens of rubberized concrete

did not exhibit brittle failure instead a more gradual failure was observed. It can be argued that because of their

ability to withstand large tensile deformations, the rubber aggregate will act as springs delaying the widening of

cracks and preventing full disintegration of the concrete mass. The rubber aggregate act as fibres.The continuous

application of the compressive load will cause generation of more cracks as widening of existing ones, the failing

specimen during this process is capable of withstanding large deformations without full disintegration. The process

will continue until full disintegration of the specimen.

Flexural strength

At 15% crumb rubber the flexural strength of concrete was higher than that of ordinary concrete. This could be due

to the crumb rubber which acts as a fibre. When a crack appears on the specimen the crumb rubber absorbs the

loading stress and prevents the widening of the crack. This ensures that the specimen takes longer to disintegrate.

However at 25% replacement the flexural strength reduced. Following this trend it can be deduced that

improvements in flexural strength are limited to relatively small rubber aggregate contents.


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CHAPTER 6

6.0 CONCLUSION AND RECOMMENDATIONS

6.1 CONCLUSION

On completion of the project several conclusions were inferred.

The resultant rubberized concrete was workable and produced a well finished surface. There was a notable

decrease in density and reduction in slump with increase in crumb rubber content.

The material constituents conformed to the required standards.

There was an increase in the water content with increase in percentage of crumb rubber.

Load deformation characteristics were determined by carrying out Compressive Strength Tests, Tensile

Strength Tests and Flexural Strength Tests. The compressive strength reduced with addition of crumbrubber. Tensile strength also reduced with addition of crumb rubber. However the flexural strength

increased when 15% of crumb rubber was used but when 25% of crumb rubber was used as a substitute for

fine aggregates the flexural strength reduced. Thus improvement in flexural strength is limited to the

percentage substitution of fine aggregate with crumb rubber.

The reduction in Compressive strength and Tensile strength may limit the use of rubberized concrete in

structural applications that require high strength. However its improved flexibility and reduced brittleness

means it may be used to make pedestrian blocks, roadway medium barriers on roads, in machine rooms as

floors where high strength in concrete may not really be as beneficial as its flexibility and reduced

brittleness.

6.2 RECOMMENDATIONS

From the research it is seen that it is possible to produce concrete using crumb rubber as partial replacement for fine

aggregate. For example it is possible to produce concrete blocks with the desired strength characteristics. However

there is room for more research to investigate the feasibility of producing rubberized concrete blocks on a

commercial basis.

From the research carried out it is evident that with addition of crumb rubber the water content varies thus further

research needs to be carried out to develop a suitable mix design to produce concrete of the desired strength

characteristics.


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APPENDIX

Figure 15: 25% Replacement Rubberized concrete

Figure 16: 15% Replacement Rubberized Concrete


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Figure 17: Cylinder specimens 15% and 25% replacement

Figure 18: Cube specimen 15% replacement under compression


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Figure 19: Cylinder specimen 25% replacement under tension

Figure 20: Cylinder specimen failed in tension


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Figure 21: 25% replacement beam specimen ready for flexural test

Figure 22: Placing the strain gauges to determine strain and deflection


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Figure 23: Failure of rubberized concrete


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Figure 24: Charts used for calculating mix design


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Figure 25: Charts used in calculating mix design


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Figure 26: Charts used in calculating mix design


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REFERENCES

British Standard Institution, BS 1881-116:1983, “Method for Determination of Compressive Strength of

Concrete Cubes, ” London

British Standard Institution, BS1881-117:1983, “Method for Determination of Tensile Splitting Strength, ”

London

British Standard Institution, BS1881-118:1983, “Method for Determination of Flexural Strength “London

A Report by, “The University of Strathclyde in Glasgow” on “The use of recycled rubber tyres in concrete

construction.”

Eldin N. And Senouci, A, B.,Rubber Tyre Particles as Concrete Aggregate, Journal of Material in Civil

Engineering, Vol. 5, No.4 pp. 479-496, 1993.

Piti Sulontaskul and Chalermphol Chaikaew, Paper on Concrete Pedestrian Block Containing CrumbRubber from Recycled Tyres

Use of waste tyres in concrete retrieved on 16 th Jan 2010 from www.google.co.ke

Chaikaew, C., M.Eng Thesis, Study on the Use of Wasted Tyres Particles on Soft Surface Concrete Block,

Department of Civil Engineering King Mongkut Institute of Technology-North Bangkok, 2003.

.
http://www.google.co.ke/http://www.google.co.ke/http://www.google.co.ke/

gichuru r w - use of crumb rubber in concrete

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