Surface properties of grayish-yellow sandstone after thermal shock

A rapid cooling of rocks caused by rainfall from fire-generated atmospheric convection after the conflagration would produce thermal shock. It may affect intensely future decay patterns of the rock, which can then be related to rock weathering and geomorphological change. In this paper, thermal shock experiments at different temperatures and cycles were carried out on grayish-yellow sandstone. Its surface properties, including color, roughness and thermal properties, were systematically studied. The results show that the color of sandstone turned red after thermal shock and the color difference increases with the increase of temperature and cycle; at above 500 °C, the decomposition of kaolinite and the volume expansion of quartz causes damage to the sandstone surface, and the cycle causes the damage to accumulate, which is the reason for the sudden increase in roughness after 6 cycles; the thermal conductivity decreases with the increase of temperature and cycles, which is due to the evaporation of the of water (combined water and structural water) and the increase of roughness. The cycle has a cumulative effect. With the increase of cycle, the color difference and thermal conductivity slightly increase or decrease, while the roughness has a significant increase. Thermal conductivity has an exponentially decreasing relationship with color difference, and they have a reliable correlation.