Assessing Changes in Rock Properties and Tensile Strength due to High Temperature from Laboratory Simulation Studies

The effects of high temperature on the tensile strength and physical properties of rocks were investigated using furnace heating and simulated fire treatments. Four rock types—basalt, granite, limestone, and sandstone—were examined under dry, wet, and saturated conditions (0%, 50–60%, and 100% water content, respectively). Tensile strength was measured before and after heating using the Brazilian test, while changes in porosity, thermal conductivity, mass, and P- and S-wave velocities were also evaluated. Thermal measurements indicate that both heating methods reached maximum temperatures of approximately 600 °C and produced comparable effects on rock properties. Initial water content had a negligible influence on post-treatment tensile strength and physical properties. In contrast, rock lithology strongly controlled the degree of thermal damage. Basalt, characterized by high initial tensile strength, exhibited minor reductions in tensile strength and wave velocities, whereas sandstone showed greater degradation. Granite and limestone exhibited pronounced reductions in P- and S-wave velocities. Rocks with higher thermal conductivity, such as sandstone, experienced larger decreases in thermal conductivity after heating, while basalt showed the smallest change. Conversely, basalt exhibited the greatest increases in porosity and mass loss. Overall, rock lithology and initial mechanical strength are the primary factors governing rock degradation under high-temperature exposure.