Influence of cooling rate on thermal degradation of physical and mechanical properties of granite

Large temperature changes may cause degradation in physical and mechanical properties of rocks. This degradation can be influenced by heating-cooling procedure. In this study, it is proposed to investigate the influence of cooling method after heating to high temperature on the degradation of physical and mechanical properties of granite. For this purpose, two different cooling procedures are considered, the rapid cold water cooling and the slow step-by-step cooling. Two groups of granite samples are first heated to a desired temperature ranging from 25 degrees C to 900 degrees C, and then cooled respectively by using these two methods. The porosity and ultrasonic velocity of the thermally treated samples are measured. Uniaxial and triaxial compression tests are also performed to evaluate the elastic properties and compression strength. It is found that for both groups of samples, the thermal treatment induces the porosity increase, the wave velocity decrease and the modification of elastic modulus and compression strength. But the modification of mechanical properties is clearly influenced by the thermal treatment procedure.