Effects of high temperature on rock bulk density

A deep understanding of the physico-mechanical characteristics of rocks undergoing thermal treatments has gained a great interest in deep rock projects. In this research, the size and mass of cylindrical granite samples were measured before, under and after a temperature up to 1000 degrees C, and their bulk densities at different temperature levels were calculated. Under and after high temperature, the granite density decreased with temperature due to the increase of the granite volume and decrease of the granite mass, with the rock volume increase being the prominent factor driving this behaviour. Additionally, the rate at which density increased under high temperature was always larger than the rate after high temperature. The rock mass loss after thermal treatment was attributed to the evaporation of different types of water, thermal reactions of rock-forming minerals and generation of rock fragments, while the rock volume expansion was mainly caused by thermal expansion and reactions of the rock-forming minerals, which was in accordance with the optical microscope observation results. 400 degrees C is considered as the threshold temperature for the relationship between the decrease rate of rock density and temperature. Two fitting equations were proposed as the two boundaries of the rock density decrease rates.

Automated summary

This research examines the physico-mechanical characteristics of rocks undergoing thermal treatments, revealing that the density of rocks decreases with increasing temperature due to the expansion of rock volume. The loss of rock mass after thermal treatment is attributed to water evaporation, thermal reactions, and generation of rock fragments, while rock volume expansion is mainly caused by thermal expansion and reactions of rock-forming minerals.