Variation of mechanical properties of granite after high-temperature treatment

Variations in the mechanical properties (compressive strength, elastic modulus, tensile strength, and fracture toughness) of granite were analyzed as functions of temperature. It was found that above 200 degrees C, tensile strength and fracture toughness tended to decrease with temperature, while variations in the compressive strength and elastic modulus demonstrated decreasing trends when the heating temperature exceeded 400 degrees C. The temperature ranges of room temperature-200 and above 600 degrees C-corresponded to an undamaged state and strongly/completely damaged state, respectively. It is suggested that 400 degrees C might be a critical threshold of thermal damage to granite. Based on results of statistical tests, a sharp decrease in mechanical properties can be recognized, accompanied by a drastic growth in peaking strain and acoustic emission rate. This phenomenon may be associated with the alpha/beta phase transition of quartz.