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INTRODUCTION
1.1 GENERAL
Concrete is a family of binding material, fine aggregate, coarse aggregate and water. Concrete is normally used in the frame structure. Recycling waste solid materials is one of the most challenging problems worldwide with the unprecedented growth of the world population. Solid waste management is one of the major environmental concerns, Over 5 billion tons of non-hazardous solid waste materials are generated in each year. Of these, more than 270 million scrap-tires (approximately 3.6 million tons) are generated each year. In addition to this, about 300 million scrap-tires have been stockpiled. Several studies have been carried out to reuse scrap-tires in a variety of rubber and plastic products, incineration for production of electricity, or as fuel for cement kilns, as well as in asphalt concrete. Studies show that workable rubberized concrete mixtures can be made with scrap-tire rubber.
Ground tyre rubber fibre reinforced concrete (GRFRC) has become a matter of interest in the last few years, due to its good performance. Tyre rubber constitutes a large portion of that solid waste which has turned into a worldwide environmental concern. In several countries, rubber tyre is being burned and used as fuel, which can result in serious hazards unless health considerations are carefully considered. Scrap tires dumped in sanitary landfills are a significant environmental hazard and result in possible contamination. Only small quantities of scrap tires are being used or recycled as construction materials. This new material provides a good mechanical behaviour under static and dynamic actions.
The optimum crumbed rubber fibre content, the compatibility and stability of cement–rubber interface, the dynamic energy dissipation and its better damping capacity and the stiffness reduction. It has been experimentally shown that crumbed tyre rubber additions in structural high strength concrete slabs improved its fire resistance, reducing its spalling damage under fire. This paper presents an overview of some of the research published regarding the use of scrap-tires in Portland cement concrete.
1.2 GROUND TYRE RUBBER FIBRE
(FRC) is concrete containing fibrous material which increases its structural integrity. It contains short discrete fibres that are uniformly distributed and randomly oriented. Fibres include steel fibres, glass fibres, synthetic fibres and natural fibres – each of which lends varying properties to the concrete. In addition, the character of fiber-reinforced concrete changes with varying concretes, fiber materials, geometries, distribution, orientation, and densities. fibres are usually used in concrete to control cracking due to plastic shrinkage and to drying shrinkage. They also reduce the permeability of concrete and thus reduce bleeding of water. Some types of fibers produce greater impact–, abrasion–, and shatter–resistance in concrete. Generally fibers do not increase the flexural strength of concrete, and so cannot replace moment–resisting or structural steel reinforcement. Indeed, some fibers actually reduce the strength of concrete. The amount of fibers added to a concrete mix is expressed as a percentage of the total volume of the composite (concrete and fibers), termed "volume fraction" (Vf). Vf typically ranges from 0.1 to 3%. The aspect ratio (l/d) is calculated by dividing fiber length (l) by its diameter (d). Fibers with a non-circular cross section use an equivalent diameter for the calculation of aspect ratio. If the fibber’s modulus of elasticity is higher than the matrix (concrete or mortar binder), they help to carry the load by increasing the tensile strength of the material. Increasing the aspect ratio of the fiber usually segments the flexural strength and toughness of the matrix. However, fibers that are too long tend to "ball" in the mix and create workability problems.
Most of the research done so far in the ground tyre rubber has been carried out as coarse aggregate or fine aggregate by adding crumbed rubber or strips, but very few researches has been conducted by adding tyre as fibres .It has been proved that fibres outperform chips. The bonding of cement-rubber bond can be increased by addition of NAOH (sodium hydroxide).The principle objective is to develop ways of exploiting inherent properties like toughness, impact strength, resistance to crack propagation, abrasion resistance that ground tyre can bring into the concretes
Addition of rubber as fibre in concrete increases the toughness of concrete but reduces the strength and stiffness. The lower strength and stiffness can be compensated by limiting the rubber content in the concrete. As larger fibres are very easy to produce, it is expected that the strength of larger fibre can be improved.
Ground rubber for commercial application may be nominally sized as large as 19mm to as small as 0.15 mm. it depends upon the type of size reduction equipment and intended applications. The processed used tyre in ground rubber applications are typically subjected to two stages of magnetic separation and to screening.
1.3 OBJECTIVES
To analyze the behavior of ground tyre rubber reinforced slabs subjected to various loading conditions.
To determine the compressive strength, split tensile strength, flexural strength on recycled rubber reinforced slabs.
1.4 SCOPE
To formulate the optimum percentage of fiber and admixture required for M25 grade concrete.
To study the efficiency of recycled rubber fiber obtained from ground tire rubber in enhancing the tensile strength of RCC slabs.
To compare the Recycled rubber fiber reinforced concrete (RRFRC) with conventional slabs.
To conserve the environment resource.
To reduce the environmental pollution.
To reduce disposal cost, construction cost, so it is economical
LITERATURE REVIEW
2.1 GENERAL
This chapter presents the information about the detailed literature survey made on the effect of ground tyres on concrete and the outcomes obtained from the research works carried out already .
2.2 LITERATURES
Gregory Marvin Garric (2005): “ANALYSIS AND TESTING OF WASTE TIRE FIBER MODIFIED CONCRETE”
• Waste tires were used in the form of chips and fibers.
• The fibers were further divided into batches with different lengths to determine the effect of length has on the properties of concrete.
• There was a noticeable decline in the compressive strength of the concrete; however, there was an increase in the toughness of the concrete.
• It was concluded that waste tire fibers were more suitable as additives than waste tire chips since they produced the highest toughness and also this paper studies about the effect of waste tyre rubber as fiber in numerical analysis like finite element analysis and with that analysis the cracks formed in the specimen with waste rubber fibre is very much low when compared with specimens without waste tire fibres.
• This paper also shows that the aspect ratio of the fibres play an vital role in determining the strength and toughness of the concrete.
F. Herna´ndez-Olivares et,al., (2007) : Fatigue behaviour of recycled tire rubber-filled concrete and its implications in the design of rigid pavements. Construction and Building Materials 21 1918–1927
• This paper presents the results of fatigue bending tests on prismatic samples of recycled tyre rubber-filled concrete (RRFC) with different volumetric fractions (VF) of rubber (0%, 3.5% and 5%) after a long term exposition to natural weathering in Madrid (Spain) (one year ageing).
• The results of recycled tyre rubber-filled concrete (RRFC) under fatigue loads and the analytical study presented in this paper show the feasibility of using this cement based composite material as a rigid pavement for roads on elastic subgrade.
Shu Ling Zhang et,al., (2010): “Prediction of mechanical properties of polypropylene/waste ground rubber tire powder treated by bitumen composites via uniform design and artificial neural networks”. Materials and Design 31 1900–1905.
• Recycling of waste ground rubber tire requires special techniques because waste ground rubber tire is a thermoset material, which cannot be reprocessed like thermoplastics.
• A promising way of ‘recycling’ waste ground rubber tire powder (WGRT) is to incorporate it into thermoplastics to obtain thermoplastic elastomers.
• A proprietary software package called Rubber Computer Aided Design (RCAD) was used for this purpose. RCAD utilizes.
the uniform design technique for the design of starting experiments which was selected for reducing the number of preliminary experiments when compared to traditional simultaneous methods.
Asi Ibrahim, Shalabi Faisal, Naji Jamil. Use of Rubber Tyre in asphalt concrete mixes by Department of Civil Engineering, Hashemite University, Jordan, Department of Civil Engineering, Sana’a University, Yemen, Received 25th September 2007, revised 13th October 2007, accepted 24thOctober 2007.
One of the main reasons behind the appearance of early distresses in Jordan roads and the low surface skid resistance is the use of marginal quality limestone aggregate. Large quantities of good quality rubber tyre are available in the Northeastern parts of Jordan.
In this research, the possibility of improving the properties of local asphalt concrete mixes by replacing different portions of the normally used limestone aggregate by basalt was investigated. The replacement included total replacement of the limestone by basalt, replacing the coarse aggregate, and replacing the fine aggregate. Results showed that the optimal mix was the mix that had basalt coarse aggregate and limestone fine aggregate. In order to overcome the stripping potential of the optimal mix, 20% of the filler portion of the aggregate, material smaller than 0.075 mm, was replaced by lime.
The optimal mix showed superiority, over the tested mixes, in all the evaluated properties, which were Marshall Stability, indirect tensile strength, stripping resistance, resilient modulus, dynamic creep, fatigue, and rutting
[Eldin, et al., 1993] Experiments Done with Different Rubber Content
To examine the strength and toughness properties of rubberized concrete mixtures. They used two types of tire rubber with different rubber content. Their results indicate that there is about an 85% reduction in compressive strength, whereas the tensile strength reduced to about 50% 10 when the coarse aggregate was fully replaced by rubber.
A smaller reduction in compressive strength (65%) was observed when sand was fully replaced by fine crumb rubber. Concrete containing rubber did not exhibit brittle failure under compression or split tension. A more in-depth analysis of their results indicates a good potential of using recycled rubber in Portland cement concrete mixtures because it increases fracture toughness. However, an optimized mix design is needed to optimize the tire rubber content in the mixture.
Recycled waste tire rubber was also investigated as an additive to Portland cement concrete [Zaher, et al, 1999]. Two types of waste tire rubber were used, fine crumb rubber and coarse tire chips. The study was divided into three groups. In the first group only crumb rubber was used and only replaced the fine aggregates. In the second group tire chips were used to replace the coarse aggregates. In the third and final group both crumb and chips were used.
In this group the rubber content was equally divided between crumb and chips, and again the crumb replaced fine aggregates while the chips replaced the coarse aggregates.
The rubber content used in the three groups ranged from 5-100%. The aggregates were partially replaced by the rubber. They found that rubberized PCC can be made and are workable (even though greatly reduced) with the rubber content being a much as 57% of the total aggregate volume. Their results showed that the reduction in strength was too great, thus they recommended not replacing more than 20% by volume of the aggregate with waste tires.
Researchers have tried to gain different advantages from the use of waste tire in concrete. High-strength concrete (HSC) with silica fume was modified with different amounts of crumbed truck tires [Hernandez-Oliveres, et al 2003]. They were aiming to reduce the stiffness of HSC to make it compatible with other materials and building elements, unexpected displacement of building foundations and improving the fire performance of the buildings.
Xiang shu et al., (2011) Recycling of waste tire rubber in asphalt and portland cement concrete: The use of crumb rubber in asphalt paving mixture has long been proven successful due to good compatibility and interaction between rubber particles and asphalt binder. Recycling of waste rubber in Portland cement concrete has not been so successful due to two factors. Incompatibility in chemical property between rubber and cement paste and the significant difference in stiffness resulting in stress concentrations. One technical problem that still needs to be addressed is storage stability – how to store crumb rubber modified asphalt at high temperatures for as long as possible without phase separation.
Ivan mangili et al., (2011) Full factorial experimental design to study the devulcanization of ground tire rubber in supercritical carbon dioxide. The aim of the experimental design was to investigate the influence on the process of temperature, pressure, amount of devulcanizing reagent, treatment time and their interactions. The experimental dataset was modeled by multiple linear regressions. The most significant variables were temperature, percentage and their interaction.
F.pacheco torgal et al., (2013) Tyre rubber waste based concrete. An estimated 1000 million tyres reach the end of their useful lives every year and 5000 million more are expected to be discarded in a regular basis by the year 2030. This paper reviews research published on the performance of concrete containing tyre rubber wastes. It discusses the effect of waste treatments, the size of waste particles and the waste replacement volume on the fresh and hardened properties of concrete.
Khatib and Bayomy (1999) investigated the workability of TRAC.
They observed a decrease in slump with increased rubber aggregate content by total aggregate volume. Their results show that for rubber aggregate contents of 40% by total aggregate volume, the slump was close to zero and the concrete was not workable by hand. Such mixtures had to be compacted using a mechanical vibrator. Mixtures containing fine crumb rubber were, however, more workable than mixtures containing either coarse rubber aggregate or a combination of crumb rubber and tyre chips.
S i ddique and Naik (2004) and Senthil Kumaran et al (2008)
presented an overview of some of the research published regarding the use of scrap tyres in the manufacture of concrete. Studies indicate that goodworkable concrete mixtures can be made with scrap-tyre rubber.
Eldin and Senouci (1992) reported that, in general the TRAC
batches showed acceptable performance in terms of ease of handling placement and finishing. However, they found that increasing the size or percentage of rubber aggregate decreased the workability of the mix and subsequently caused a reduction in the slump values obtained. They also observed that the size of the rubber aggregate and its shape (mechanical grinding produces long angular particles) affected the measured slump. The slump values of mixes containing long, angular rubber aggregate were lower than those for mixes containing round rubber aggregate (cryogenic grindings).
Round rubber aggregate has a lower surface/volume ratio. Therefore less
mortar will be needed to coat the aggregates, leaving more to provide workability. They suggested that the angular rubber aggregates form an interlocking structure resisting the normal flow of concrete under its own weight; hence these mixes show less fluidity. It is also possible that the presence of the steel wires protruding from the tyre chips also contributed to the reduction in the workability of the mix.
Eldin and Senouci (1993) reported a reduction in concretedensity of,
up to 25% when ordinary aggregate was replaced by coarse rubber aggregate. Li et al (1998) found that the density of TRAC was reduced by around 10% when sand was replaced by crumb rubber to the amount of 33% by volume.The replacement of natural aggregates with rubber aggregates tends to reduce the density of the concrete. This reduction is attributable to the lower unit weight of rubber aggregate compared to ordinary aggregate. Previous studies have found that the unit weight of TRAC mixtures decreases as the percentage of rubber aggregate increases. Topcu (1995) included low volumes of rubber aggregate during the preparation of the concrete, while Rostami et al (1993) appeared to use larger volumes of rubber aggregate. Their results indicated that concrete densities were reduced to 87% and 77% of their original values, respectively, when the maximum amounts of rubber aggregate were used in the investigations.
Ali et al. (1993) reported that air content
when rubber aggregate was added to the concrete, the air content increased considerably (up to 14%). Fedroff et al (1996) and Khatib and Bayomy (1999) observed that the air content increased in TRAC mixtures with increasing amounts of rubber aggregate. Although no air-entraining agent (AEA) was used in the TRAC mixtures, higher aircontents were measured as compared to control mixtures made with an AEA(Fedroff et al 1996).
The higher air content of TRAC mixtures may be due to the nonpolar nature of rubber aggregates and their ability to entrap air in their jagged surface texture. When non-polar rubber aggregate is added to the concrete mixture, it may attract air as it repels water. This increase in air voids content would certainly produce a reduction in concrete strength, as does the presence of air voids in plain concrete (Benazzouk et al 2007).
Since rubber has a specific gravity of 1.14, it can be expected to sink rather than float in the fresh concrete mix. However, if air gets trapped in the jagged surface of the rubber aggregates, it could cause them to float (Nagdi 1993). This segregation of rubber aggregate particles has been observed in practice.
Goulias et al (1998) conducted an experimental study incorporating
crumb rubber, as fine aggregate with Portland cement.
Several studies had been carried out to describe the use of tyre rubber aggregate in concrete. Results had indicated about the size, proportions and surface texture of rubber particles that noticeably affect the compressive strength of rubber concrete mixtures.
Test results showed modifications in the brittle failure of concrete, which indicates that rubber concrete specimens exhibited higher ductility performance than normal concrete. Results showed large deformation without full disintegration of concrete.
Chou et al (2007) investigated Rubber replaced concrete for various applications and has shown promising results. The addition of rubber particles leads to the degradation of physical properties, particularly, the compressive strength of the concrete. Chung et al (1999) introduced rubber concrete using waste rubber using the dry process. The compressive strength of rubber concrete was about 89 MPa and the Poisson’s ratio, which is the ratio of compressive-to-tensile strength, was 5.5%.
Eldin and Senouci (1993) conducted experiments to examine the strength and toughness of rubberized concrete mixtures. Three sets of experiments were performed, the first set using coarse rubber aggregate (chipped tyres) of 19-38 mm size and the second and third sets using smaller diameter chips of 6 mm and 2 mm respectively. The results found that the specimen containing rubber when loaded in compression exhibits more gradual failure, either of a splitting (for coarse rubber aggregate) or a shear mode (for fine crumb rubber).
Norman (1992) used carbon black as filler in rubber concrete and found the increase in structural flexibility. Test results show significant improvement in the results of elongation, modulus of elasticity, hardness and tensile strength of the rubber concrete. The results shows increase in tensile strength, elongation varies from 440% – 730% for various carbon blacks.
Fairburn and Larson (2001) investigated the use of concrete derived from
shredded rubber from old tyres for resurfacing a cracked pavement. He found that the concrete was more slip resistant, highly elastic, lighter in weight, and could be used for fireproofing and insulation.
Toutanji (1996) conducted experiments to investigate the effect of the replacement of coarse aggregate by rubber aggregate. Four different contents of rubber aggregate with a maximum size of 12.7 mm were used to replace the coarse aggregate at 25, 50, 75 and 100% by volume and discovered that the incorporation of the rubber aggregates in concrete produced a reduction in compressive strength of up to 75% and a significantly smaller reduction in flexural strength of up to 35%. The reduction in both strengths increased with increasing the rubber aggregate content. It is observed that the specimens containing rubber aggregate exhibited a ductile mode of failure as compared to the control specimens.
In Biel and Lee (1996) used recycled tyre rubber in concrete mixes made with magnesium oxychloride cement, where the aggregate was replaced by fine crumb rubber up to 25% by volume. The results of compressive and tensile strength tests indicated that there is better bonding when magnesium oxychloride cement is used. The researchers discovered that structural applications could be possible if the rubber content is limited to 17% by volume of the aggregate.
Schimizze (1994) developed two TRAC mixes using fine rubber granulars in one mix and coarse rubber granulars in the second. While these two mixes were not optimized and their design parameters were selected arbitrarily, their results indicate a reduction in compressive strength of about 50% with respect to the control mixture. The elastic modulus of the mix containing coarse rubber granular was reduced to about 72% of that of the control mixture, whereas the mix containing the fine rubber granular showed a reduction in the elastic modulus to about 47% of that of the control mixture. The reduction in elastic modulus indicates higher flexibility, which may be viewed as a positive gain in rubberized PCC (RPCC) mixtures used as stabilized base layers in flexible pavements.
Topcu (1995) investigated the effect of particle size and content of tyre rubbers on the mechanical properties of concrete. The researcher found that, although the strength was reduced, the plastic capacity was enhanced significantly.
Khatib et al (1999) concluded that RPCC mixtures can be made using ground tyre in partial replacement by volume of CA and FA. Based on the workability, an upper level of 50% of the total aggregate volume may be used. Strength data developed in their investigation (compressive and flexural) indicates the systematic reduction in the strength with the increase of rubber content. From a practical viewpoint, rubber content should not exceed 20% of the aggregate volume due to severe reduction in strength. Once the aggregate matrix contains nontraditional components such as polymer additives, fibers, iron slag, and other waste materials, special provisions would be required to design and produce these modified mixes. At present, there are no such guidelines on how to include scrap tyre particles in PCC mixtures.
Segre and Joekes (2000) worked on the use of tyre rubber particles as addition to cement paste. In their work, the surface of powdered tyre rubber (particles of maximum size 35 mesh, 500 m) was modified to increase its adhesion to cement paste. Low-cost procedures and reagents were used in the surface treatment among that sodium hydroxide (NaOH) solution gave the best result. The particles were surface-treated with NaOH saturated aqueous solutions for 20 minutes before using them in concrete. The test results showed that the NaOH treatment enhances the adhesion of tyre rubber particles to cement paste, and mechanical properties such as flexural strength and fracture energy were improved with the use of tyre rubber particles as addition instead of substitution for aggregate. The reduction in the compressive strength (33%) was observed, which is lower than that reported in the literature
2.3 REVIEW OF LITERATURE
• Waste rubber has been used in the form of aggregates, crumbs, chips and fibres.
• Waste/ground tyre rubber has been used for casting concrete cubes, cylinders, pavements.
• Decrease in compressive strength and split tensile strength has been reported.
• Strength data developed in their investigation (compressive and flexural) indicates the systematic reduction in the strength with the increase of rubber content.
• The concrete was more slip resistant, highly elastic, lighter in weight, and could be used for fireproofing and insulation.
• Also increase in toughness has been reported.
2.4 NEED FOR THE RESEARCH
• There is no proper process for recycling ground tyre rubber hence by using it in concrete we can march towards sustainability.
• It can withstand heavy loads thereby reduces yielding of slabs (gives failure warnings).
• Since most of the regions in India are earthquake prone zones GFRC can perform well under dynamic loads.
• In the past research ground tyre rubber is has been used as aggregate, but we are going to use ground tyre rubber as fibre.
Water
It is the key ingredient, which when mixed with cement, forms a paste that binds the aggregate together. The water causes the hardening of concrete through a process called hydration. Hydration is a chemical reaction in which the major compounds in cement form chemical bonds with water molecules and become hydrates or hydration products. The role of water is important because the water to cement ratio is the most critical factor in the production of “perfect” concrete.
Too Much water reduces concrete strength, while too little will make the concrete unworkable. Potable tap water available in the laboratory with PH
3.1.3 Water Cement Ratio (W/C)
Water reacts with cement chemically and causes setting and hardening of concrete. In lubricate the aggregate facilitating the passage of cement through the voids in the aggregate, makes the concrete workable.
It is found theoretically that the water requires is about 0.50-0.60 time the weight of cement. The ratio of cement by weight is termed as “water-cement ratio” and the strength and quality of concrete primarily depends upon this ratio the important points to observed in connection water-cement ratio are
1. Minimum quality of water should be used to have reasonable degree of workability.
2. Water cement ratio for structures to weathering should be carefully decided. For instance, for structures that are regularly subjected wetting and drying, water cement ratio by weight should be 0.4 & 0.55 for thin selection & mass concrete respectively. For structures which are continuously under water cement ratio by weight should be 0.55 & 0.66 for this section respectively.
3. A thump rule for ordinary concrete given below assuming the materials are non-absorbent and dry may be adopted. Weight of cement = 28% of the weight if cement +4% of the weight of total aggregate.
3.1.4 Fine Aggregate
The sand is used as fine aggregate and it is collected from nearby area. The sand has been sieved in 4.75 mm sieve.
3.1.5 Coarse Aggregate
The coarse aggregate is the strongest and least porous component of concrete. It is also a chemically stable materialAggregates come in various shapes, sizes, and materials ranging from fine particles of sand to large, coarse rocks. Because minimize the amount of cement to use. 70 to 80% of the volume of concrete is aggregate keeping the cost of the concrete low. The selection of an aggregate is determined, in part, by the desired characteristics of the concrete.
Although some variation is aggregate properties is expected, characteristics that are considered when selecting aggregate include:
Grading
Durability
Particle shape and surface texture
Abrasion and skid resistance
Unit weights and voids
Absorption and surface moisture
3.1.6. TYPES OF RUBBER
3.1.6.1 Shredded Tyres
The shreds are basically flat, irregularly shaped tyre chunks with jagged edges that may or may not contain protruding sharp pieces of metal, which are parts of the steel plates or beads. The size of the tyre shreds may range from as large as460 mm to as small as 25 mm, with most particles within the 100 mm to 200 mm range. The average loose density of the tyre shreds varies according to the size of the shreds, but can be expected to be between 390 kg/m3 to 535 kg/m3. The average compacted density ranges from 650 kg/m3 to 840 kg/m3 (Shulman, 2000). They are non-reactive under normal environmental conditions (Humphrey et al,1993).
3.1.6.2 Tyre Chips
Tyre chips are finer and more uniformly sized than tyre shreds, ranging from 76 mm down to approximately 13 mm in size. Although the size of tyre chips, like tyre shreds, varies with the make and condition of the processing equipment, nearly all tyre chip particles can be gravel sized. The loose density of tyre chips can be expected to range from 320kg/m3 to 490 kg/m3. The compacted density of the tyre chips ranges from 570 kg/m3 to 730 kg/m3 (Bosscher et al, 1992). The chips have absorption values that range from 2.0 t3.8 percent and are nonreactive under normal environmental conditions (Humphrey et al, 1993). The shear strength of tyre chips varies according to the size and shape of the chips with friction angles in the range of 19o to 26o, while cohesion values range from4.3 kPa to 11.5 kPa. Tyre chips have permeability co-efficients ranging from 1.5to 15 cm/sec (Humphrey et al, 1993).
3.1.6.3Ground Rubber
Ground rubber particles are intermediate in size between tyre chips and crumb rubber. The particle sizing of ground rubber ranges from 9.5 mm to 0.85 mm.
3.1.6.4 Crumb Rubber
Crumb rubber used in hot mix asphalt normally has 100 percent of the particles finer than 4.75 mm. The majority of the particle sizes range within 1.2 mm to 0.42
3.1.7.1 PROPERTIES OF GROUND TYRE RUBBER
The various properties of ground tyre rubber used in concrete are discussed.
3.1.7.2 Slump
The slump decreases with increase rubber content by total aggregates volume, the results show that at rubber content 40% by total aggregates volume. The slump was zero and the concrete was not workable by hand. Such mixes had to be compacted using a mechanical vibrator.
3.1.7.3 Density
The general density reduction was to be expected due to the low specific gravity of the rubber aggregates with respect to that of the natural aggregates.
The reduction in density can be a desirable feature in a number of applications, including architectural application such as, false facades, and interior construction as well as precast concrete, light weight hollow and solid blocks, slabs etc.
3.1.7.4 Air Content
The air content increases in rubber-concrete mixture with increase amount of ground tyre rubber.
3.1.7.5 Plastic Shrinkage
The addition of rubber shreds to mortar reduced plastic shrinkage cracking compared to a control mortar. Despite their apparently weak bonding to the cement paste, rubber shreds provided sufficient restrain to prevent micro cracks from propagating.
3.1.7.6 Specific Gravity Gs,
The ratio of the density of the solid phase of a material to the density of water at normal conditions. The specific gravity of tire rubber ranges between 1.02 and 1.27, with higher values corresponding to tire rubber containing steel inclusions [Bressette, 1984; Humphrey et al., 1992; Humphrey and Manion, 1992; Ahmed, 1993]. This range corresponds to densities greater than that of water and significantly lower than that of mineral aggregates, which typically range from 2.6 to 2.8. TDA does not float when submerged in water, which is considered a major advantage over other lightweight fills (e.g., some expanded polystyrene [EPS] Geofoam®) in submerged or flooding applications. The specific gravity of steel-belted tires is generally higher than that of glass-belted tires. The specific gravity of TDA can be estimated using methods contained in ASTM C 127 [ASTM, 2008].
3.1.7.7Water Absorption Capacity
Water absorption capacity is related to the amount of water that can be retained on the TDA particle surface after drainage is allowed. Water absorption capacity is the percentage of water retained to the dry weight of the sample. Water absorption capacity of TDA ranges from about 2 to 4% [Humphrey, 2006a]. This range is comparable to that of mineral aggregate, including clean, coarse sand and gravel. Water absorption capacity can be estimated by performing a test in accordance with ASTM C 127 standard “Standard Test Method for Density, Relative Density (Specific Gravity), and Absorption of Coarse Aggregate” [ASTM, 2008].
3.1.7.8 Unit Weight
The unit weight, γ, of compacted TDA with a typical 3-in. maximum size is about 40 pounds per cubic foot (pcf), prior to long-term compression under its own weight. This value is thereby much lower than the typical range of 100 to 130 pcf for mineral aggregate. The unit weight of compacted TDA can be estimated in the laboratory or in the field using techniques similar to those used for soils. In the laboratory, the testing method used for estimating TDA unit weight is similar to the method used for soils (ASTM D 698, Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort [ASTM, 2008]). Standard ASTM D 698 has limitations when used with TDA because TDA particles are much larger than typical soil particles, and TDA particles do not fit well in the standard soil sample mold. In addition, the level of compaction energy used for TDA does not need to be as high as for soils. To circumvent these limitations, the use of a larger mold is recommended to accommodate TDA particles, as suggested in ASTM D 6270. Circular molds for TDA have diameters of 10 to 12 in. and heights of up to 12.5 in. [Ahmed, 1993; Humphrey, et al., 1992; Humphrey and Manion, 1992; Edil and Bosscher.
3.1.7.9 Toughness and Impact Resistance
Tantala, et al. [2] investigated the toughness of a control concrete mixture and rubcrete mixtures with 5 and 10% buff rubber by volume of coarse aggregate. They reported that toughness of both rubcrete mixtures was higher than the control concrete mixture. However, the toughness of rubcrete mixture with 10% buff rubber was lower than that of rubcrete with 5% buff rubber because of the decreasing compressive strength.
3.1.7.10 Freezing and Thawing Resistance
Savas, et al. [27] carried out investigations to study the freezing and thawing (ASTM C 666, Procedure A) durability of rubber concrete. Various mixtures were made by incorporating 10, 15, 20, and 30% ground rubber by weight of cement to the control mixture. Based on their studied they concluded that (i) rubcrete mixtures with 10 and 15% ground rubber exhibited durability factors higher than 60% after 300 freezing and thawing cycles, but mixtures with 20 and 30% ground rubber by weight of cement couldnot meet the ASTM standards, (ii) Air-entrainment did not provide significant improvements in freezing tha thawing durability for concrete mixtures with 10, 20, and30% ground tire rubber, and (iii) increase in scaling (as measured by the reduction in weight) increased with the increase in freezing and thawing cycles.
3.2 SPECIMEN DETAILS
a) Cube Specimens
Cube of size 100 X 100 X 100 mm is used for making both conventional concrete and ground tyre rubber concrete Specimens.
b) Cylinder Specimens
Cylinders of 150mm diameter and 300mm height is used for making both conventional concrete and ground tyre rubber concrete Specimens.
c) Prismatic Beam Specimens
Beam of size 100 X 100 X 500 mm is used for making both conventional concrete and ground tyre rubber concrete Specimens.
d) Slab Specimens
Slabs of 600mm length and 600mm breadth and a depth of 60 mm is casted for both conventional and ground tyre rubber concrete specimens.
CHAPTER 4
EXPERIMENTAL WORK AND TEST RESULTS
4.1 TEST ON MATERIALS
4.1.1 TEST ON FINE AGGREGATE
4.1.1.1 Specific Gravity
Specific gravity of aggregate is the ratio of its weight of an equal volume of water reference temperature -4ºC. Specific gravity of aggregate is useful for calculating void content in aggregate.
Procedure
1. Take a clean dry pycnometer with its cap and weight it (W1g).
2. Take about 200g of aggregate passing through 10mm sieve in the pycnometer and find the weight of pycnometer with aggregate (W2g).
3. Fill the pycnometer with distilled water up to the hole in the conical cap and shake it to remove the air. Then take the weight of pycnometer with aggregate and water (W3g).
4. Empty the pycnometer and clean it thoroughly. Then fill it with distilled water up to the hole of the conical cap and weight it (W4g)
Specific gravity of fine aggregate = Dry weight of fine aggregate
Wt of equal volume of water
4.1.1.2 Sieve analysis of fine, coarse aggregate and the fineness modulus
Apparatus
Set of sieves ranging 40mm, 25mm, 20mm, 16mm, 12.5mm, 10mm, 6.3mm, 4.75mm, weighing balance, heating pan and 2.36mm, 1.18mm, 600μ, 300μ, 150μ stove
Procedure
i. Arrange all the sieves in order of size, with largest sieve size on the top.
ii. Place weighted material on the top most sieves and shake each sieve. Shaking shall be done with a varied motion backward and forward, left to right, circular – clockwise, anti – clockwise with frequent jerking, so that the material is kept moving over the sieve surface. Shaking should be done till all the particles are given a chance to pass through the sieve.
iii. Weigh the material retained on each sieve on a weighing balance. The material retained on each sieve after shaking represents the fraction of aggregate coarser than the sieve size in question and finer than the sieve size above.
iv. Calculate % retained and the cumulative % retained on each sieve. The summation of the % cumulative wt retained on all the sieve sizes up to 150 micron, divided by 100 given the fineness modulus.
Fine Modulus = Cumulative % weight retained (up to 150 microns) / 100
4.1.2 TEST ON COARSE AGGREGATE
4.1.2.1 Water Absorption Test for Aggregates:
Scope
This procedure covers the determination of absorption of coarse aggregate.
Terminology
Absorption – the increase in the mass of aggregate due to water being absorbed into the pores of the material, but not including water adhering to the outside surface of the particles, expressed as a percentage of the dry mass. The aggregate is considered “dry” when it has been maintained at a temperature of 110(+ or -) 5oC (230 +or – 9oF) for sufficient time to remove all uncombined water.
Apparatus
• Balance scale: with a capacity of 10 kg, sensitive to 5kg. meeting the requirements.
• Sample container: a wire basket of 3.35mm or small mesh, with a capacity of 4 to 7L (1 to 2 gal) to contain aggregate with a nominal maximum size of 37.5 mm (1½ in.) or smaller, and/or a larger basket for larger aggregates.
• Water tank: watertight and large enough to completely immerse aggregate and basket, equipped with an overflow valve to keep water level constant.
• Sieves 4.75mm (No. 4) or other sizes as needed.
• Large absorbent towel
Procedure
1. Dry the test sample to constant mass at a temperature of 110±5ºC(230±9ºF) and cool in air at room temperature for 1 to 3 hours.
2. Immerse the aggregate in water at room temperature for a period of 15 to 19 hours.
3. Place the empty basket into the water bath and attach to the balance. Inspect the immersion tank to ensure the water level is at the overflow outlet height. Tare the balance with the empty basket attached in the water bath.
4. Remove the test sample from the water and roll it in a large absorbent cloth until all visible films of water are removed. Wipe the larger particles individually.
5. Remove the sample from the basket. Ensure all material has been removed. Place in a container of known mass.
4.1.2.2 Aggregate Impact Test
Test impact value of the given aggregate is found out by aggregate impact test.
Procedure
1kg of aggregate (W1) is taken. The aggregate is placed and leveled. The aggregate left over if any (W2) hence the weight of will be (W1 - W2)g. The hammer is allowed to 15 blows. Each blow is delivered at an interval of not less than second. The aggregate passing through 12.5mm I.S sieve retain on 10mm is sieve and also over dried for a period of 4 hours at a temp of 100º to 110ºC is taken. The aggregate passing from the cup is removed and sieved I.S.Sno.240. The aggregate passing through I.S.sno.240 (W3g) is weighed. The experiment is repeated once again using the sand weight of (W1 – W2)g and this test repeated for three trails..