Impact of elevated temperatures on the structural performance of recycled rubber concrete: Experimental and mathematical modeling

Abstract To reduce damage caused by the disposal of non-biodegradable materials such as rubber into the environment, one strategy is to use rubber as a substitute for common materials in concrete. However, there is a great need to investigate the mechanical properties of this new concrete, known as recycled rubber concrete (RRC). Thus, this study attempted to explore the performance of RRC containing recycled rubber aggregate (RRA), replacing fine aggregate by 5, 10, 15, and 20%, under high temperatures of 200, 400, 600, and 800 ℃. For this purpose, the physico-mechanical properties of cylindrical RRCs, namely the tensile and compressive strength, modulus of elasticity, compressive stress-strain behavior, stiffness, peak strain, and weight loss, as well as the appearance, were scrutinized after exposure to heat. The results indicate a notable deterioration of the physico-mechanical characteristics of the concrete specimens as temperature increased. Furthermore, the thermal response of specimens made with RRA was relatively similar to that of the reference concrete (RC). Meanwhile, in the heated specimens, as the residual strength declined with increasing temperature, the linearity of the ascending branch increased, and the descending branch became flatter. Subsequently, a series of empirical models were proposed to capture the mechanical characteristics of concrete, and a juxtaposition was carried out between the results extracted from this study and the predicted ones based on ASCE, ACI 216, CEB-FIP 1990, and EN 1992 codes. In the end, a stress-strain model was developed to obtain an empirical equation capable of predicting the RRC characteristics under heat, which showed a rigorous consistency with the experimental results.