Mechanical properties of thermal insulation concrete with recycled coarse aggregates after elevated temperature exposure

Thermal insulation concrete with recycled coarse aggregate (RATIC) provides an excellent alternative to energy saving and the reuse of waste concrete in buildings. In this paper, experiments were conducted to investigate the mechanical properties of the RATIC material after exposure to elevated temperatures, including failure feature and residual strengths. The effects of temperatures and the replacement percentage of recycled coarse aggregate (RCA) on the compressive and tensile strengths of the RATIC were first assessed experimentally. Then, the formulas for both compressive and tensile strengths were developed as a function of temperatures using the regression analysis. The test results show that the RATIC is prone to explosive spalling due to the compact structure of cement paste and low thermal conductivity. The compressive strength of the RATIC increases slightly under the temperature of 400 C and then decreases significantly with an increasing exposed temperature. In contrast, the splitting tensile strength of the RATIC decreases significantly after the material was exposed to a high temperature of 200 to 800 C. With the increasing RCA percentage, the RATIC experiences more strength deterioration in tension than compression, while little difference was observed regarding thermal exposure and failure modes of the RATIC.