Stress–strain characteristics of fire‐exposed recycled coarse aggregate concrete

Concrete sustainability and performance under extreme conditions are of growing interest in construction engineering. This study delves into the influence of recycled coarse aggregate (RCA) content and elevated temperatures on normal‐strength concrete containing RCA. Five different concrete compositions, featuring varying content of RCA (ranging from 0% to 100%), were examined. The heating and subsequent cooling followed the ISO‐834 temperature–time graph up to 800°C. The primary objective was to evaluate residual properties, including the stress–strain behavior, compressive and tensile strength, secant elastic modulus, peak strain, and bond strength of RCA concrete. The findings reveal a consistent decrease in both strength and stiffness parameters of RCA concrete with rising temperatures, while peak strain exhibits a rapid increase at elevated temperatures. Interestingly, RCA content had a negligible impact on the relative deterioration of high‐temperature exposed RCA concrete compared to that at ambient conditions. Moreover, the bond behavior closely resembled that of natural aggregate concrete when used in moderate proportions. Degradation models based on regression analysis of the data were used to quantify the bond strength reduction for RCA‐based concrete and the slip of rebar concerning various temperatures. Importantly, these models demonstrated consistency with those applicable to conventional concrete.