A STEP TOWARD DEVELOPING RUBBERIZED CONCRETE TO BE USED IN RC DEEP BEAMS

Using waste tire rubbers as a partial replacement of natural aggregates in conventional concrete materials can overcome many annoying environmental issues. In the literature, the experimental studies clearly revealed that the new concrete with rubber added have much lower compressive and tensile strength than the normal concrete as well as having a much better ductility and impact resistance. The studies mainly focused on small-scale specimens such as cubes, prisms and cylinders. There is a dearth in knowledge about the behavior of large-scale elements, especially such elements with brittle failure such as deep beams. The present study aimed at developing rubberized concrete with a minimal reduction in compressive, flexural and tensile strengths suitable for RC deep beams. Thirteen concrete mixtures were constructed: the first is a control normal concrete mixture and twelve other concrete mixtures with crumb rubber as a partial replacement of coarse aggregates. The parameters included the rubber replacement ratio (5%, 10%, 20%, and 30%), pre-treatment of rubber with NAOH and the use of silica fume powder as a partial replacement of cement. The results were analyzed considering the fresh and hardened concrete properties. It was shown that adding crumb rubber severely affected the concrete properties, but rubber pre-treatment while using silica fume noticeably controlled the reduction. Within the tested range of the rubber replacement ratio, it was found that the optimum ratio is 10% with an affordable 20% reduction in strength. This reduction is believed to be balanced by the safe disposal of waste tyres, the reduction in concrete density associated with the economic design and the concrete ductility.