Effects of elevated temperatures’ exposure on the properties of concrete incorporating recycled concrete aggregates

The concrete and its thermal gradient response must be considered when it is subjected to high temperatures. This study examines the impact of exposure to elevated temperatures (500 °C, 700 °C, and 1000 °C) on concrete's physical and mechanical properties incorporating recycled concrete aggregates (RCA). It emphasizes substituting RCAs for natural coarse aggregate (NCA) at 20%, 40%, 60%, 80%, and 100%. The intended behavior is post-heating; a cold sample serves as a control. The evolution of graduating temperature in the muffle furnace is similar to the ISO curve in a fire. The data analyzed indicate that a temperature rise affects the characteristics of recycled aggregate concrete (RAC). A heating level of 500 °C does not significantly affect the initial resistance, which is not the situation at temperatures of 700 °C and 1000 °C. Regarding residual strength, the concrete with 40% RCAs concrete performs quite well. At 700 °C, its strength loss in compressive strength is 24.4%, whereas the control concrete is 29.8%. Mass loss, capillary water absorption, water-accessible porosity and non-destructive tests reveal that elevated temperature damages RAC. Lastly, XRD, TGA, and SEM microstructural analyses are employed to interpret the fundamental mechanisms of heated RAC due to temperature changes.