Effects of high temperature on rock bulk density

ABSTRACT

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°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°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.

KEYWORDS:

• High temperature
• granite
• bulk density
• thermal expansion
• microstructure

Acknowledgments

This work is jointly supported by National Natural Science Foundation of China (No.41602374 and No.41674180) and the Fundamental Research Funds for the Central Universities-Cradle Plan for 2017 (Grant No. CUG2170207). We are grateful to Professor Ranjith PG and 3Gdeep group (Department of Civil Engineering, Monash University, Australia) for their help to provide valuable suggestions on English polish and manuscript revision.

Disclosure statement

The authors declared that they have no conflicts of interest to this work.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China. [41602374,41674180]; Fundamental Research Funds for the Central Universities[CUG2170207].