technical paper (2)

PROCEDING OF FINAL YEAR PROJECT (I)TECHNICAL REPORT FKAAS, SESSION 2001/2011 (2), April 2011

The Use of Waste Tire Rubber as Partial Replacement for Fine Aggregates in Concrete

Chen Wai Yew1, Noorli Ismail2

Abstract – The waste tires rubber is one of the issues of environment problem. Since the amount of automobile in our country had increased, it contributed to the increase of waste tires disposal. In addition, the waste tire is considered as non decaying materials that can pollute the surrounding environment. Based on the problem statement, researchers had investigated the application of waste tires rubber in construction field by using the rubber particle as partial replacement of fine aggregates or coarse aggregates in concrete. In this research, the aim of the study is to investigate the use of waste tire rubbers as partial replacement for fine aggregates in concrete construction based on the physical properties and mechanical properties. This paper focused on 0%, 15%, 30% and 45% rubber as partial replacement for fine aggregates. Laboratory test will be carried out by using compressive strength test, split tensile test, rebound hammer and ultrasonic pulse velocity test. The expectation outcome results of rubberized concrete in term of physical properties, compressive strength, tensile strength, surface of hardness and concrete quality will be analyzed and discussed compare with ordinary concrete. Copyright © 2011 FKAAS Final Year Project (2). - All rights reserved.

Keywords: Waste tire rubber, Concrete, Compressive strength, Tensile Strength, Physical properties of concrete

PROCEDING OF FINAL YEAR PROJECT (I)TECHNICAL REPORT FKAAS, SESSION 2001/2011 (2), April 2011

I. Introduction

The disposal of waste tires is becoming the major waste management problem. About 60% of the waste tires are disposed through unknown routes [1]. Management of waste tires rubber are very difficult for municipalities because tire rubber considered as non decaying materials that can pollute the surrounding environment. As the waste tires are extremely durable and not naturally decaying, the waste tires will remain at landfill and continuing environment hazard. Besides that, waste tire rubber also able to pose a breeding ground for mosquito since the shape and impermeability of tires which may hold water for long periods and provides shelter for the mosquito development. As the disadvantage of the waste tires had been stated, one of the alternatives to face the problem had been made by the researchers. A positive method is to reuse the waste tires in concrete mixtures.

Moreover, the increase consumption of concrete in building construction raised the problem of impoverishment of natural resources. Cement and aggregate, which are the most important constituents used in concrete production and are the vital materials needed for the construction industry. Therefore, this led to a continuous and increasing demand of natural materials used for their production.

Based on the previous findings, waste tire rubber can be a part of concrete mixture by partial replacing coarse aggregates or fine aggregates. Several studies had been made by researchers that in term of the workable rubberized concrete mixtures can be made with scrap tires. The researchers had investigated on the use of different shapes, sizes, and the percentage of rubber particles based on the partial replacement of natural aggregates in concrete mixture. According to the previous researcher, they reported that use of rubber particles to replace a portion of fine or coarse aggregates result a systematic reduction of strength, less unit weight, but enhance toughness and ductility. Ref. [2] indicates that rubber concrete is not recommended for structural applications, but can be suitable for nonstructural purposes such as lightweight concrete walls, building facades and architectural units. Ref. [3] concluded in their research that rubberized concrete can successfully be used in secondary structural components such as culverts, sidewalk and running tracks.

The authorities shall suggest and encouraging that there is a strong need to use recycled materials in concrete and specifically waste tires should be used within building materials would provide an ideal and environmental friendly disposal method for a large amount of the waste tires.

II. Objectives of the Study

This paper is focus on the crumb rubber as a partial replacement of fine aggregates in concrete mixture. The percentages of crumb rubber will be conducted are 15%, 30% and 45%. The general objective of the studies is to evaluate the fresh and hardened properties of the concrete produced by crumb rubber as a partial replacement of natural fine aggregates. The specific objectives in this study are to determine the ; workability of rubberize concrete; physical properties which is including the specific gravity of material, water absorption and the unit density; and mechanical properties which is including compressive and tensile strength of rubberized concrete compare to conventional concrete.

III. The Scope of Study

This study is focusing on rubberize concrete performance and as comparison to conventional concrete in term of physical properties and mechanical properties. It concentrated on the performance of a single gradation of crumb rubber instead of natural fine aggregates. Waste tires from local sources will be manually cut into pieces below 5 mm to suit the fine aggregates size which 5 mm is the maximum size. In order to rate the characteristic of fresh concrete, the aspect of mix designation and workability of the rubberized concrete and conventional concrete will be considered. Sieve analysis test according to BS 410 will be conducted on the rubber particle and fine aggregates to determine the grading of sizes. DOE method will be used to design the concrete mixture. Slump test in accordance with BS 1881 part 102: 1983 will be conducted.

Testing method on hardened rubberized concrete and conventional concrete in accordance with British Standard are compressive strength test, split tensile strength test, rebound hammer and ultrasonic velocity pulse test.

IV. Problem Statement of the Study

Concrete is one of major material used in construction. Therefore, the demand of natural sources of concrete material is getting high. Researchers had gave a lot of effort to find the alternatives way in order to replace the natural sources as concrete material to improve concrete material and in the same way to practice environment friendly. Since the waste rubber tires are not easily biodegradable even after a long


period of landfill treatment, it can be described as one of the major environmental challenges facing municipalities around the world or even in our country. In addition, tire requires a large amount of space in landfill.

One of the promising solutions is to incorporate rubber particles into the cement material. The previous researchers had stated that the use of rubber particles as partial replacement of fine aggregates or coarse aggregates will result to increase of reduction strength. Although rubberize concrete may not suitable for structural element, there is still a very large market for non primary structural applications.

V. The Significant of the study

To raise awareness in construction field, continuously investigation on rubber particle as replacement of aggregates in concrete mixture is needed. Previous researchers had used different amount of percentage and sizes of rubber particle and in order to determine the concrete properties and meet the specific requirement of concrete.

To promote the use of rubberize concrete and at the same way to reduce the waste tires disposal at landfill, this research will provide more scientific evidence to support the reuse of accumulated waste tires. The outcome of the result based on the physical properties and mechanical properties of rubberize concrete will be specifically discussed compare to the conventional concrete.

Therefore, the use of recycled waste tires as an aggregate can provide the solution for two major problems. One of the problems is the solution environment hazard created by waste tires. Besides that, the depletion of natural resources by aggregate production can be solved.

V. Literature Review

Review of previous findings sources from various authors including different ideas, method and material used results and others. The information is concerning the properties of recycled rubber as partial or fully replacement of aggregates in concrete. It reviewed how the authors analyze and evaluate the physical and mechanical properties of rubberized concrete.

V.1 Rubberize Concrete Material

Base on previous research and investigation, the rubberized concrete material consists of rubber aggregate (crumb rubber and chip rubber), cement, natural aggregates and water content. Over the past few years, researchers had used many of sizes on waste rubber tires as partial or fully replacement in their studies. There are 2 categories of process to produces

the fragments of waste tires. The processes are mechanical grinding and cryogenic process. Base on reference. [4] findings, the mechanical grinding process is the most common method and consists of using variety of grinding techniques to mechanically break down the rubber shred into small sizes. Meanwhile, cryogenic process accomplished by freezing of scrap tires and directly into a cooled closed loop hammer to be crushed into small particles [5]. Mechanical grinding process will be used on my studies to obtain the shredded waste tires. Three broad categories of discarded tire rubber have been considered; chipped tire, crumb tire and ash tire. Various researchers had used different sizes on their investigation. Ref. [8] used the dimension of chipped rubber about 25-30 mm. Meanwhile, reference [9] used chipped rubber aggregates and graded their rubber into 3 groups of 38mm, 25mm, and 19 mm maximum sizes. Meanwhile, the crumb rubber has been reported to have a nominal size between 4.75 mm (No. 4 sieve) and 0.075 mm (No. 200 sieve). (T.C ling 2007) used 1mm to 3mm and 1mm to 5mm crumb rubber as the replacement of fine sand. Meanwhile, reference [8] used 3mm to 10mm as the dimension of the crumb rubber aggregates. For ash rubber, the rubber consists of particles smaller than 1 mm. Ref. [8] reported that it used as filler in concrete due to its size.

Cement is one of the factors which can affect the principle mechanical properties of hardened concrete. According to previous research, mostly the investigator used Ordinary Portland Cement as their material in the experimental material because the cement is the most common type of cement in general use around the world and highly suitable for construction work. Ordinary Portland cement may not suitable to use when there is exposure to high amount sulphates in the soil or groundwater [25].

For the partial replacement base on previous findings, usually course aggregates will be partial replaced by chipped tires; meanwhile fine aggregates will be partial replaced by crumb tires. Various sizes of aggregates were used in the previous investigation. For example, reference [9] used 38mm; reference [11] used 19mm; and reference [10] used 16mm. On the other hand, reference [6] used natural fine aggregate which is

http://en.wikipedia.org/wiki/Cement


specified as natural silica sand, and coarse aggregates taken from crushed limestone.

V.2 Sieve analysis

Sieve analysis is a procedure for the determination of the particle size distribution of aggregates using a series of square or round meshes starting with the largest. The grading of each type of aggregates should be known and controlled. The previous researchers used coarse aggregates sizes retained at sieve size of 5 mm (BS 410) or 4.75 (ASTM 3/16 in). Meanwhile, fine aggregates that passing through the sieve size of 5 mm (BS 410) or 4.75 (ASTM 3/16 in) were used. Different types of fine sand grade had been used by the previous studies. According to reference [7] studies, the grade of the fine sand used was zone 3 according to BS 410 as the percentage of passing sand at 600µm is in the range of 60% to 79. In the other hand, reference [14] used zone 2 of sand fine aggregates in his study. The sieve analysis result of fine aggregates and crumb rubbers from sieve analysis test shown in Fig. 1.

Fig. 1. Sieve analysis of fine aggregates and crumb rubber [14]

V.3 Water Ratio

A lower water-cement ratio leads to higher strength and durability, but may cause to poor workability during mixing with others material. The compressive strength is mainly related to the water/cement ratio. As the water/cement ratio decreases, the compressive strength increases. Ref. [12] used 0.4, 0.5, 0.7 water/cement ratio to prepare the rubber filler concrete and rubberized concrete. Ref. [12] reported the properties slump and workability of concrete is mainly related to the water-cement ratio. When water-cement ratio decreases, the slump and workability of concrete will increases. Fig. 2 show the relationship between the slump and water cement ratio.

Fig. 2. Slump range description for slump test for rubber filler concrete and rubberized concrete [12].

Regarding to the previous investigation, mostly the researcher used the same water ratio and cement content on the mixture to keep constant in all samples.

V.4 Concrete Mixture

Several of investigators had used different percentage in the partial or fully percentage of rubber aggregates in the concrete mixture. Control specimen that means 0 % of rubber aggregates in the concrete mixture is necessary to be prepared for the purpose of comparison between rubberized concrete and concrete without rubberized. Ref [7] used 50 % and 100 % of crumb rubber and 100% of chipped rubber; reference [6] used 20 %, 40 %, 60 %, 80 %, 100% of crumb rubber; reference [23] used 5 %, 10 %, 15 %, and 20 % of crumb rubber in their investigation. On the hand, reference [13] used 10 %, 20 %, 30 % in their mixture, which some specimens included additional of chemical treatment.

The DOE method will be carry out to determine the mixture proportion by using C25 in the study. By using DOE method, improvement can be achieved in one or more of the many characteristics of any given product or process. Base on reference [14] study, a total of 16 mixes consisting of four types of concrete grades (C15, C25, C30 and C40) were produced with partial replacements of the coarse aggregate by 10, 25 and 50 % of the rubber aggregate

V.5 Physical Properties of Concrete

This section is based on previous researcher’s results on the physical properties of rubberized concrete. The physical properties included concrete unit density, workability, specific gravity and air content. It seems that the partial or fully replacement of waste rubber tires on concrete decrease the unit density of a concrete that without rubberized. The increase percentage of rubber either chipped or crumb rubber contributed to the reduction of unit density of the concrete. However, crumb rubber concrete proved to be lighter in weight with its density reduced compared to concrete rubberized by chip tires [10]. It is because the density of the rubber is lower than the natural coarse aggregates or fine aggregates. Ref. [7] reported that reduction of about 30% in the density of concrete casted using chipped rubber replacing 100% of the coarse aggregate when compared to the control specimen.

Consideration the water content and cement mixture shall be given during the mixture to avoid low workability. The increase of the crumb rubber content in the mix resulted in a decrease in slump of the mixtures. The fact was proven by reference [3]. Their results show that the slump was close to zero when the rubber aggregates contents 40% of total aggregates. In addition, reference [6] results show that the value of


slump decrease by the addition percentage of rubber aggregates in the mixture. Table 1 shows the result of slump and unit weight obtained by reference [6].

TABLE ITHE RELATIONSHIP VALUE BETWEEN THE PERCENTAGES OF CRUMB

RUBBER AND WATER CONTENT; SLUMP (MM); UNIT WEIGHT (KG/M³) [6].

Crumb Rubber (%)

Slump (mm) Unit Weight (kg/m3)

0 75.33 2399.0

20 60.7 2217.0

40 35.7 2068.3

60 17.7 1987.0

80 10.3 1830.6

100 4.7 1740.6

Despite the decrease in measured slump, observation during mixing and casting showed that increase of crumb content in the mix still produced a workable mix in comparison with the control mix [6]. The previous studies had noted that the reasons may contributed to the reduction in the workability of the mix is size of rubber aggregates and its shape. Observation shall be done in term of the size and shape which can affect the measurement of slump test [9].

In the other hand, increasing amount of rubber aggregates may contribute the increasing of air content. Entrained air content increased (from 3 % to 3.5 %) in concrete mixtures with addition of tires rubber waste particles [20]. Through out the studies of [8], it shown at Table 2 that fully replacement of chips tire in a mixture sample had resulted to high air content compare to the sample of using crumb tires and ash tires as fully replacement in the mixture sample.

TABLE 2THE RELATIONSHIP VALUE BETWEEN THE PERCENTAGES OF CRUMB RUBBER AND WATER CONTENT; SLUMP (MM); UNIT WEIGHT (KG/M³)

(MALEK K BATAYNEH 2008).

On the other samples, samples which without fine aggregates in the mixture also resulted to high air content. The increasing of air void can contribute to decrease in concrete strength.

Previous investigator had reported that rubber aggregates contain low specific gravity compare to rubber aggregates. Thus, it brings to result the density of concrete with rubber aggregates is lower than concrete with aggregates. Ref. [20] reported that the general density reduction of rubber aggregates is lower than natural aggregates due to the low specific gravity of the rubber aggregates with respect to that of the mineral aggregates.

V.6 Properties of Hardened Rubberized Concrete

The previous researcher had found out that presence of rubber aggregates in concrete is contributed to reduction of compressive strength and split tensile strength.

The compressive strength of concrete is one of the most important properties which needed to be determined. The performance of the concrete is greatly affected by the properties of the rubber content and as well as by cement type and admixture properties. Several of investigator used different shape and sizes of rubber aggregates for the determination of the compressive strength. Base on reference [7] studies, concrete casted using chipped rubber as a full replacement to coarse aggregate shows a significant reduction in the concrete strength compared to the control specimen. Compressive strength was reduced significantly by 90% when using chipped rubber as a full replacement to the coarse aggregate in the concrete mix. According to reference [6], it maintained a linear relationship by increasing the crumb rubber to a limit of 40 % between the increase of crumb rubber and the compressive strength. However, it lost about 50% of the compressive strength at 40% rubber content. They reported that rubber content between 40% and 100% continues to reduce the strength to a maximum loss of strength of up to 90%. The result shown in Fig. 3.

Fig. 3 Comparison between strength reduction and rubber concrete [6].

The rubber aggregates containing up to 20% crumb rubber can be used in light weight structural elements. The second category required compressive strength of 7–17 MPa for moderate concrete. Low density Concrete within 300 kg/m3 to 800 kg/m3 can use for non-structural

Samples Water Fine Coarse Air

content

Ratio Aggregates aggregates %

(kg/m³) (kg/m³)

100% chipped 0.5 258.9 - 25

tires100% crumb 0.5 - 405.3 20

tires


purposes (insulation panel, pavements, blocks, etc. [25]. Ref. [24] investigated the static resistance of the wall samples by containing rubber aggregates. The overall static resistance of the wall samples was reduced as a result of the addition of the rubber to replace coarse aggregates of the concrete. The reduced mass and reduced resistance of the walls with rubber resulted in a reduced blast resistance.

According to reference [2], concrete casted using crumb rubber as a full replacement to sand shows a significant increase in the concrete strength compared to the concrete casted using chipped rubber as a replacement to coarse aggregate.

Using rubber waste in concrete, less concrete module of elasticity is obtained. According to reference [22] investigation, the length and width of rubber chip influenced the value of modulus elasticity. The longer and wider of chip length and the presence of steel wire increased the modulus of elasticity. The dimensions and distribution of tires chips in each batch shown in Table 3.

Ref. [26] stated that tensile stresses in structures are caused by less or more uniform shrinkage or drying and by temperature changes. Base on previous related studies, they had reported that split tensile strength of the rubberized concrete is lower than traditional concrete because bond strength between cement paste and rubber tire particles is poor [23]. Several of researcher reported that increasing the amount of rubber aggregates for the purpose of partial replacement of natural aggregates contributed to the reduction of split tensile reference [6] and the result shown in Table 3

TABLE IIITHE RELATIONSHIP VALUE BETWEEN THE PERCENTAGES OF CRUMB

RUBBER AND TENSILE STRENGTH ; AND COMPRESSIVE STRENGTH [6].

Rubber content Spilt tensile Compressive

% Strength ƒt (Mpa) Strength ƒc (Mpa)

0 2.82 25.33

20 1.84 18

40 1.47 12.27

60 0.94 8.07

80 0.53 4.47

100 0.22 2.5

The previous researcher had reported the similar reasons. They found that the presence of the waste tires acted like voids in the mixture and cause to the weak bond between the waste tire and concrete mixture. With the increase in void content of the concrete, there will be a corresponding decrease in strength. Besides that, waste tires are weak in the hardened cement mass and as a result, it produced high internal stress that is perpendicular to the direction of applied load.

VI. Methodology

This section will be discussed about the detail of mix designation on workability testing of the fresh concrete and the concrete strength of the hardened concrete. The designation is according to BS 1881 as a reference for specification requirement for control mixes which are necessary as a comparison to the rubberize concrete.

VI.1 Research Methodology

In the initial part of the study, review of previous research may need to get some ideas and information through the previous findings in term of mixture, testing method and the analysis of the study. For the concrete mix proportion, application DOE method will be conducted. 4 groups of sample including control specimen, 15%, 30% and 45% crumb rubber for the partial replacement of natural aggregates will be tested by destructive test and non destructive test on compressive strength. Besides that, physical properties of the sample will be determined. Fig. 3 shows the methodology flow chart of the whole study.


Fig. 3 Flow chart of Research Methodology

VI.2 Material used for rubberized

The materials will be conducted for the tests are cement, fine aggregates, course aggregates and rubber aggregates. There is no chemical treatment on the concrete mixture in these studies. Ordinary Portland cement Type 1 will be used because it is most common used by the previous researcher and highly suitable for used in general concrete. Additionally, there is no exposure to sulphate in the concrete mixture.

The aggregates shall be in one of the following conditions; oven-dry as described in accordance with BS 812: Part 2” and air dried at 20 ± 5 ºC in accordance with BS 1881 part 125 1983 before mix in the mixture. Meanwhile, sample of course aggregates within the range 20 mm and 10 mm of sieve size will be used for the mixture. Both of sieves sizes are according to Standard sieve designation BS 410. Sieve analysis test will be conducted ensure the grading of aggregates both course and fine aggregates in accordance with BS 410.

For the rubber aggregates, the wasted or old tire from lightweight vehicle such as mobile car, motorcycle and bicycle will be used. For the production of crumb tires from a waste tire rubber, firstly cut out a section of the tire which is larger than the desired size by using hammer and chisel. Avoid cutting the inside rim of the tire due to the heavy band of steel wire reinforcement there. Then an electric band saw will be used to cut smoothly through the heavy rubber tire. Smaller tooth sizes usually work better. Crumb tires will be prepared for the mixture concrete as partial replacement of total fine aggregates. Sieve analysis will be conducted to ensure the grading of rubber aggregates within the limits of fine aggregates. Sample of rubber aggregates which is passed through the 5 mm of sieve size will be used for the mixture. The ranges of crumb tires sizes are between 5 mm to 1 mm as shown in Figure 4.

Fig. 4 crumb tires

VI.3 Concrete mix proportion

The material of mixture for the control mixes and the control concrete mixes are designed with specified requirement of compressive strength according to BS 1881 part 125: 1983. Concrete without rubber aggregates will be used as the control concrete. Water/Binder ratio (0.58) and cement content (18.1 kg) were kept constant for all mixtures. Designated of crumb rubber contents were selected 15%, 30% and 45% by volume of total fine aggregate. According to the studies of [6], they stated that minimum strength required for light weight concrete is 17 mpa and their sample of 20 % rubber content met the required strength. Ref [7] reported that it is recommended to test concrete with crumb rubber ranging between 10 % until 25 % of rubber content. To prove the studies, 15 % and 30 % of rubber content is chosen as comparison in term of the strength that suitable to meet the required minimum strength. Base on previous studies, rubber content more than 40 % will contribute to reduction of strength to a maximum loss of strength. Therefore, 45 % of rubber content is chosen to examine the maximum loss of strength. All specimen samples size will be used are 150 mm x 150 mm x 150 mm except for split tensile strength test. Cylinder sample 150 mm of diameter size and 300 mm length will be used. Super plasticizer is not included in this study. There are 4 types of testing method including compressive test, split tensile, rebound hammer and ultrasonic pulse velocity which need to be tested on the 7, 14 and 28 days of the concrete. The mixture proportion of the basic ingredient consists of cement, water, course aggregates and fine aggregates. The concrete mix design will be designed is based on DOE method. By using the application of DOE method, the designation volume of concrete material per m3 is shown in Table IV. The outcome of concrete mix proportion design is shown in Table IV.

TABLE IIIDESIGNATION VOLUME OF CONCRETE MATERIAL

Concrete material (kg) per m³

Cement 362

Water 210

Sand/ Fine aggregate 731

Coarse aggregate max size (20 mm) 1097

TABLE IVDESIGNATION VOLUME OF CONCRETE MATERIAL

Per trial Water Cement Fine Course Rubber mix content (kg) aggregate aggregate content

0.05 m³ (kg) (kg) (kg) (kg)

Control 10.5 18.1 36.6 54.9 -

specimens15 %

crumb 10.5 18.1 31.1 58.5 5.5rubber


30% crumb 10.5 18.1 25.6 58.5 11

rubber45%

crumb 10.5 18.1 20.13 58.5 16.47

rubber

VI.4 Mix preparation

For the initial part of the preparation before mix in the concrete mixer, the rubber aggregates will be immersed in water for 24 hours until all particles were fully saturated in both inside and outside of the surface wetted. This process will be done after the sieve analysis for both rubber aggregates and natural aggregates had been conducted. After 24 hours of being immersed, the rubber aggregates will be taken to dry surface and leave it to 24 hours for the drying process. The purpose of the process is to determine the specific gravity of the rubber aggregates compare to the natural aggregates. Larger amount of pores of the material with smaller value specific gravity obtained. There is no chemical admixture for the rubber surface treatment in this study. Same procedure will be conducted to the natural aggregates by immersing the sample aggregates in water for 24 hours and taken to dry surface and leave it to 24 hours. The specific gravity of both rubber aggregates and natural aggregates will be made as comparison. The formula of obtaining the specific gravity is the ratio of the weight in air of a unit volume of aggregate at a stated temperature to the weight in air of an equal volume of gas-free distilled water at the stated temperature.

All the specimens will be fabricated using locally available materials. Type I ordinary Portland cement will be utilized. Mixing will be done in a small rotary drum mixer. For the control specimen sample, the mix is in accordance with BS 1881 part 125: 83. However for the rubberize concrete, prior the addition the rubber aggregates into the mixture, the coarse and fine aggregates and cement will be mixed for 3 minutes or 5 minutes in the mixer. Next, the rubber aggregates will be added gradually to the mix for a period of 2 minutes. The reason for separating the rubber aggregates and natural aggregates is to provide more efficient mix and increase the workability. Water will be added for the following steps in the mix for a period of 2 minutes. Then, 5 minutes mixing process will be done by the drum mixer to produce to uniform mix.

Slump test will be conducted in accordance BS 1881 part 102: 1983 before the concrete mix being casted. The mix will be casted into 150 mm x 150 mm x 150 mm of cube size; and 150 mm diameter with 300 mm length of cylinder size. The concrete mixture shall be casted in 3 separating layers in the cube cast.

After 24 hours later, the specimen of sample will be cured in water at a constant temperature in accordance with BS 1881-111:1983. The duration of the curing process will be conducted is 7, 14 and 28 days and will

be prepared for compressive strength in accordance with BS 1881 part 116 : 1983 and split tensile in accordance with BS 1881 part 117 :1983. Table V shows the amount of specimen samples will be produced for 7 days curing age.

TABLE VAMOUNT OF SPECIMEN SAMPLES FOR 7 DAYS CURING AGE.

Samples Compressive Split Rebound hammer Total

Test Tensile&

Ultrasonic Specimen

for

TestPulse

Velocity 7 days curing

Control 3 2 2 7specimen

15 % crumb 3 2 2 7rubber30%

crumb 3 2 2 7rubber45%

crumb 3 2 2 7rubber

Total : 28 unit

Note: 28 units of samples for 7 days curing. Therefore, 28 unit x 3(7, 14, 28 days) = 84 units of samples. The total Specimen for 7 days curing is 28 unit samples to conduct the testing method. Thus, the total samples for this study are 84 units. The reason of three units are provided for compressive test and split tensile test is to obtain more accurate value by taking the average value of the three samples.

VII. EXPERIMENT

All The testing method is accordance with British Standard (BS) 1881 to determine the physical properties and mechanical properties of rubberized concrete compare to ordinary concrete.

VII.1 Slump test

Some factors may effects the concrete consistency during conducting slump test. The concrete components ratios, maximum nominal size of coarse aggregate, time between finishing mixing and making slump test and high air temperature are the factors which affect the concrete consistency. The main purpose of measuring consistency by slump test is to achieve acceptable fresh concrete workability in accordance with BS 1881 part 102: 1983. The following information shall be included in the test report are date, time of completion, place and method (general or alternative) of sampling and sample identity number; Time and place of test; Time lapse from sampling to commencement of test; Form of slump whether true, shear or collapse; and Measurement true slump.

VII.2 Unit weight


Unit weight measurement between control specimen and rubber concrete will be conducted. All the samples shall be measured before conducting any destructive or non destructive test to avoid inaccurate of value. The samples shall be in dry unit. The unit weight will be recorded and graph unit weight versus percentages of rubber content in concrete will be plotted. Therefore, comparison can be made between the four groups of cube samples. Unit weight calculated as in (1)

Unit weight, kg/m3 = Net weight (1) Volume of Measure

VII.3 Specific Gravity and Water Absorption

Natural aggregates and rubber aggregates both have different specific gravity value. Low specific gravity of aggregates or others concrete mixture material will contribute to low specific gravity of concrete. Therefore, specific gravity of both aggregates shall be determined to compare the relationship between the value of specific gravity to measure the strength or quality of the material.

The equation of specific gravity as in (2); Meanwhile the equation of water absorption as in (3).

Specific gravity = W3 / (W3 – (W1 – W2)) (2) Water Absorption = ((W3 – W4)/ W4) X 100 (3)

VII.4 Compressive Strength Test

The compressive strengths of concrete sample were determined at the ages of 7, 14, and 28 days of standard curing. A 2500KN capacity Avery-Denison compression testing machine will be used for determining the maximum compressive loads carried by various cubes. The load will be applied at a rate of 12 N/mm2 per minutes in accordance with the BS 1881-116: 83 test method. Cube specimen 150 mm x 150 mm x 150 mm will be prepared for the test. The outcome report from the test shall consists of Identification mark; Date of test; Age of specimen; Curing conditions, including date of manufacture of specimen; Appearance of fractured faces of concrete and the type of fracture if they are unusual.

VII.5 Split Tensile strength test

The split tensile of concrete sample were determined at the ages of 7, 14, and 28 days of standard curing. Specimens used are cylindrical shape with 150 mm diameter size and 300 mm length. The split tensile test will be conducted in accordance with (BS 1881 part 117: 83). The load will be applied at a rate of 12 N/mm2 per minutes in accordance with the BS 1881-117: 83 test method. The tensile strength calculated by equation as in (4).

(4)

VII.6 Rebound hammer test

This method is to correlate the surface hardness of the concrete surface to the compressive strength of the concrete. This value is then used to estimate the strength of the concrete using the correlation graph. However, the strength obtained from this test by using correlation graph is only for checking purpose. Besides strength estimation, the uniformity of the concrete surface can be determined. Area that is not well compacted will give lower rebound number, compared to well compacted area. The samples will be conducted at the age of 7, 14 and 28 days of standard curing. Concrete sample 150 mm x 150 mm 150 mm of size will be tested by rebound hammer. The relationship of compressive strength average of rebound number of concrete sample can be referred in Fig. 4. The quality of concrete also can be determined by referred Table VI.

Fig. 4 Relationship between compressive strength and rebound number

TABLE VIRELATIONSHIP BETWEEN AVERAGE REBOUND AND QUALITY OF

CONCRETE

Average Rebound Quality of Concrete

>40 Very good

30 – 40 Good

20 – 30 Fair

<20 Poor and / or delaminated

0 Very poor and/or delaminated

VII.7 Ultrasonic pulse velocity


This test is done to assess the quality of concrete by ultrasonic pulse velocity method in accordance with BS: 203 (Part 2) 1986. The method consists of measuring the time of travel of an ultrasonic pulse passing through the concrete being tested. It can be calculated as in (5).

Pulse velocity (V=L/T)

(5)

Comparatively higher velocity is obtained when concrete quality is good in terms of density, uniformity and homogeneity. It can be referred in Table VII. The samples will be conducted at the age of 7, 14 and 28 days of standard curing.

TABLE VIRELATIONSHIP BETWEEN AVERAGE REBOUND AND QUALITY OF

CONCRETE

PULSE VELOCITY CONCRETE QUALITY

>4.0 km/s Very good to excellent

3.5 – 4.0 km/s Good to very good, slight porosity may exist

3.0 – 3.5 km/s Satisfactory but loss of integrity is suspected

<3.0 km/s Poor and los of integrity exist.

VII. Conclusion

As a conclusion in this study, the review of previous investigation had given enormous of ideas and information in this related research. For the purpose of improving the properties of rubberized concrete, the investigators had conducted the analysis throughout their test on the specimens. Every researcher had used different designated rubber content, water content, aggregates properties and different types of cement in the concrete mixture to obtain the most desirable concrete. To avoid the greater loss in the designated samples, the researcher had found several of solution to treat the rubberize concrete. For example, coated the rubber aggregates by cement, silica fumes additional, pre-treatment on the surface of rubber by saturated NaOH and consideration on the rubber aggregates size and its shape.

Based on their investigation, all their findings had state that additional of rubber content in the concrete mixture results to reduction of compressive strength and split tensile strength. The greater amount of rubber aggregates instead of natural aggregates, the lower value of compressive

and split tensile strength obtained. Besides that, the rubberized concrete contributes to the increasing of reduction in unit weight. Although the rubberized concrete has lower strength compare to ordinary concrete, the rubberized concrete is lighter than ordinary concrete due to the reduction of unit weight. This should be allowing rubberized concrete to be used in non primary structural application. Such like partition wall, sidewalks, pavement, road barrier and etc. which are high demand in construction industry. Rubberized concrete is not recommended in application of structural elements, but small percentage amount within the range from 5 % to 10 % may able to use in structural elements. It depends on the requirement.

The application of waste tire in concrete might be one of the solutions to reduce the disposal of waste tire and the problem of impoverishment of natural resources.

Acknowledgements

First of all, I would like to give a million thanks to my Projek Sarjana Muda supervisor Puan Noorli binti Ismail for providing me a lot of expert guidance, valid comments, suggestions, continuous support and untiring efforts while carrying out this research work. Her dedication and excellence will be always remembered.

I am so delightful to experience this opportunity by conducting the research individually which is never been done through my academic career. I would like to give a special thanks to University Tun Hussein Onn for giving this opportunity and providing an enormous library which contains various revision books and journals. Besides that, I would like to give thanks to my friends who gave me the encouragement and support while carrying out this research. In addition, I would like to thank to everyone who had giving me guidance, supports, and everything that helping me to success my research.

I am greatly indebted to my parents and brothers for their faith in me. Their supports, encouragements and advices were priceless.

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