Effect of compression casting method on the compressive strength, elastic modulus and microstructure of rubber concrete

Abstract

Recycling rubber in the production of structural concrete is not considered a feasible option due to a significant reduction in the strength and elastic modulus of concrete. A novel concrete casting method is developed in this work that can greatly increase the strength and elastic modulus of rubber concrete. The mix design used in the study is the same as that for natural aggregate concrete (NAC), apart from replacing some of the natural coarse aggregate (NCA) by chipped rubber. Concrete specimens were cast with 0–100% chipped rubber in replacement of NCA. The fresh rubber concrete was then condensed in a specially designed mold to compress the volume of wet concrete for a period of time before demolding. Stress-strain behaviour of compressed and uncompressed rubber concrete specimens was evaluated and compared with the NAC specimens. Results show that improved stress-strain behaviour i.e., higher compressive strength and elastic modulus, are observed for compressed rubber concrete specimens as compared with uncompressed specimens, which show the effectiveness of the compression technique in enhancing the performance of rubber concrete. Compressed rubber concrete specimens with a 20% replacement ratio of chipped rubber show 35% and 29% increase in strength and elastic modulus as compared with NAC specimens, respectively. Based on the results, up to 30% of NCA can be replaced by chipped rubber to obtain compressed rubber concrete with the compressive strength and elastic modulus greater or similar to those of NAC. The proposed method encourages the utilization of waste rubber in concrete and can be easily adopted by the precast industry to manufacture precast concrete products leading towards sustainable and environment-friendly construction.