Study on Rubberized Concrete

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Study on Rubberized Concrete
If tyres are reused as a construction material instead of being burnt, the unique properties of tyres can once again be exploited in a beneficial manner. In this context, the use of tyre chips in lightweight concrete is considered a potentially significant avenue. Thus, the use of scrap tyres in concrete manufacturing is a necessity than a desire. The use of scrap tyres in concrete is a concept applied extensively over the world.

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The use of scrap tyres rubber in normal strength concrete is a new dimension in concrete mix design and if applied on a large scale would revolutionize the construction industry, by economizing the construction cost and increasing the worn out tyre disposal. It is with this intention, an experimental study is proposed to be conducted by using crumb rubber as sand in cement concrete. The rubberized concrete composite is a new structural material aiming for an enhanced energy dissipation capability and thus improved seismic performance by mixing recycled rubber crumb with concrete. While rubberized concrete is not new, this study represents the first investigation on damping and dynamic (including seismic) behaviors of rubberized concrete for its potential application as structural material. Small-scale column models were fabricated using rubberized concrete with different proportions of rubber crumb to evaluate the structural dynamic performance, including free vibration tests to identify damping ratios and seismic shaking table tests to investigate the structural responses to earthquake ground motion. Meanwhile, rubberized concrete cylinders were tested to evaluate compressive strength and modulus of elasticity. It was observed that the damping coefficient of the rubberized concrete increased by 62% compared with normal concrete and, as a result, the seismic response acceleration of the structure decreased by 27%. However the concrete suffered from reduction in compressive strength as rubber crumb was added. It was found that adding silica fume to rubberized concrete improved the bonding between the rubber and cement and thus the concrete strength. Overall, this study demonstrated the potential of using the environmentally-friendly rubberized concrete as structural material to enhance dynamic performance and reduce seismic response of concrete structures.

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Dynamic and static performance of rubberized concrete specimens was investigated

  1. Adding rubber crumb into concrete mixture increases the damping ratio by 62%
  2. Adding rubber crumb can reduce the seismic force on concrete structures
  3. Silica fume can improve bonding between rubber crumb and cement paste
  4. The study leads to potential applications of rubberized concrete as structural material

Rubberized Concrete Mix Design Approaches

Currently no standardized mixture procedure is documented either for Portland rubberized concrete (PRC) or self-compacting rubberized concrete (SCRC). Research is still ongoing to search for the best mix approaches for structural purposes. It is proposed to apply mixing procedure that commonly used in Japan to achieved rubberized concrete strength more than 40MPa. Seeing that substituting rubber aggregate in the concrete have tendency toward segregation and bleeding, has lead to several unusual adaptations of the conventional mixing procedure in an attempt to avoid this problem, the previous mixing procedure done by other researchers can be used as a guide. Thus, it was decided that preliminary study using mortar was important before concrete mix design stage, in order to understand the behavior on its fresh and hardened properties.

Discussion and conclusion

Workable rubberized concrete mixture can be made with scrap tires. The workability can be similar to normal concrete by using admixtures without any increase in the quantity of water. The literature made it clear that the density of rubberized concrete decreases with increasing amount of rubber . The loss in density would be severe when powdered rubber is used to replace aggregates. The rubber can also produce lightweight concrete for special purposes. The compressive strength of the rubberized concrete would be affected by the use of rubber in concrete. The reduction of compressive strength can be avoided if the replacement of rubber does not exceed 20% of the total aggregate content. Rubber powder reduces the flexural strength but rubber fiber increases the flexural tensile strength. By using any coupling agent, severe loss in compressive strength could be avoided. Most researchers mentioned that the abrasion resistance got improved with the addition of rubber in cement. Only few researchers found that rubberized concrete reduces the abrasion of concrete . Water absorption and water penetration increase with the increase of rubber content in concrete. The addition of rubber increases the damping ratio of the concrete. Rubberized concrete seems to be suitable to be used for concrete bridge deck as there were positive results. As recommendations for future work, a proper study on the application of rubberized concrete could be performed.

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