Study on the mechanical characteristics and damage evaluation of concrete-rock combination after high temperatures exposure

• The research on the mechanical properties and thermal damage of the CRC structure after high temperature exposure is helpful to guide the engineering design and monitoring in high temperature environment. • A new theoretical model is established to study the thermal damage evolution. • Our new findings contribute to a better experimental and theoretical basis for CRC used a complex environmental engineering. Concrete-rock combination (CRC) plays an important role in ensuring the safety and stability of the engineering (such as geothermal exploration, the production well, and radioactive waste storage) under high-temperature mechanical coupling conditions. In this study, a mechanical testing machine and an acoustic emission system were applied to investigate the mechanical properties of CRC after treatment at different temperatures (25 °C, 100 °C, 300 °C, 500 °C and 700 °C). A new theoretical model was established to study the thermal damage evolution. Meanwhile, the experimental results demonstrate that the peak strength of CRC is 36.6% for rock, and the peak strength of CRC is 129.6% relative to the concrete. When the temperature ranges from 25 °C to 500 °C, the stiffness decreases slowly, but above 500 °C, the stiffness decreases significantly. Additionally, the AE monitoring can well capture the damage location and microcrack process of CRC during the mechanical loading process after exposure to high temperatures. Finally, the theoretical values of the damage constitutive model are consistent with the experimental data, which verifies the validity of the damage model. Our new findings contribute to a better experimental and theoretical basis for CRC using complex environmental engineering.