Influence of different thermal cycling treatments on the physical, mechanical and transport properties of granite

Two different types of thermal cycling treatments (slow heating followed by slow cooling or rapid quenching) were carried out on the granite samples in the present research. The responses of physical, mechanical and transport properties of the granite after various thermal cycling treatments were compared and analyzed. Non-destructive tests (mass, volume, longitudinal wave propagation and permeability) and destructive tests (uniaxial compression and Brazilian splitting) were utilized to characterize these properties. Variations of all the properties demonstrate that thermal cycling (heating and cooling) can induce damage in the samples. Mass, density, P-wave velocity, UCS, Young's modulus and tensile strength decrease, whilst volume and permeability increase with rising temperature. Additionally, the results also demonstrate the importance of cooling method. Rapid quenching has a more significant effect on granite samples, showing lower density, P-wave velocity and strength, but greater permeability, which is due to the generation of thermal gradient cracks. Moreover, the difference between P-wave velocity and UCS of slow cooling and those of rapid quenching increases with temperature up to 500 degrees C, which can be attributed to the more significant thermal shock cracking induced by higher temperature-gradient stress in the samples during rapid quenching. The microstructural analyses from thin sections show that microcracking in granite subjected to thermal cycling treatments was induced in different severity depending on peak temperature and cooling method.