Effects of Partial Replacement of Coarse Aggregates with Reclaimed Rubber on the Mechanical Properties of Hardened Concrete

Abstract

The replacement of conventional aggregates with alternate materials like Reclaimed Rubber (RR) results in reduction of self-weight and compressive strength of concrete. This reduction in self-weight further decreases the dead load which contributes towards contraction in size of concrete members and reinforcement requirements. This diminution in compressive strength is compensated by replacing cement with supplementary materials like Silica Fume, Fly Ash or GGBS. This research focuses on the effects of partial replacement of cement and coarse aggregates with Silica Fume (SF) and Reclaimed Rubber (RR) respectively in the concrete mix. Concrete mix was prepared for M20 grade by replacing cement and coarse aggregates with SF and RR respectively for cube and cylinder samples. A base study has been carried out through compression and split tension tests by partially replacing cement with SF in 3 percent increments up to 24 percent. Maximum compressive strength of 19.6N/mm², 24.2N/mm² and 32.5N/mm² was obtained at 12% replacement of cement with SF by weight while testing specimens after 7, 14 and 28 days of curing. Maximum strength of 2.4N/mm², 2.9N/mm² and 3.1N/mm² was obtained during split tension tests conducted after 7, 14 and 28 days of curing period. Further compression and tension tests were conducted replacing cement with 12%SF along with various proportions of RR replacing coarse aggregates after different curing periods. Experiments reveal that a combination of 12%SF and 9%RR replacement produces maximum compressive strength of 19.2N/mm², 23.1N/mm² and 29.4N/mm² after curing the samples for 7, 14 and 28 days respectively. The tensile strength decreases as the rubber content is increased in the concrete mix along with optimum SF when compared with normal mix.