Physical and Mechanical Properties of Granite After High-Temperature Treatment

Abstract

As granite is one of the most widely encountered lithologies in studies of high-temperature rock mechanics, the effects of high temperatures on the physical and mechanical properties of granite have attracted considerable attention. In this study, to identify the physical and mechanical properties of granite observed before and after high-temperature treatment from room temperature to 1000\xa0°C and to determine the influence of high temperatures on granite and on its intrinsic connections, appearance, and mineral morphology, longitudinal wave testing and uniaxial and triaxial tests were performed. Our primary conclusions are as follows: (1) effects of high temperatures on microscopic minerals of granite primarily include the oxidation of dark minerals, the recrystallization of feldspar minerals, and the generation and extension of mineral cracks. (2) High temperatures decrease the speed of longitudinal waves in granite and cause longitudinal wave energy to be absorbed. Cracks created by high temperatures cause longitudinal waves to not be detected. (3) Relationships between stress and strain processes at 400\xa0°C in granite first soften and subsequently harden, and mechanical properties change only slightly overall. After a temperature of 400\xa0°C is reached, with increasing temperatures, softening characteristics emerge. At 800\xa0°C, plastic deformation occurs. At 1000\xa0°C, the strength and deformability of rock specimens are largely diminished. We found 600\xa0°C to be the threshold of mechanical properties and the transition temperature of the failure mode. (4) Finally, 400\xa0°C, 600\xa0°C, and 800\xa0°C were found to be characteristic temperatures of three different stages of physical and mechanical properties for granite.