Cyclic heating of saturated steam changes the surface properties of sandstone

Hydrothermal sandstone geothermal energy extraction is an important part of clean energy mining and use. During the mining process, the high-temperature saturated water vapour produced has a significant effect on the properties of surrounding rocks. To understand the effects of high-temperature saturated water vapour on lithology, this paper researched the effects on sandstone. First, the sandstone was subjected to 0–100 cycles of saturated water vapour heat treatment at 200 °C, during which the dry mass and saturated mass of each sample were recorded; then, data on the chroma, glossiness, roughness, and hardness of the rock samples after different cycle treatments were collected. The results show that as the number of cycles increased, the cement and surface particles peeled off successively, and the mass of the sandstone decreased. Also, the saturated water content increased overall; the chroma, gloss, and hardness decreased overall. The variation in roughness was similar to a cosine curve, reaching the maximum value at the 55th cycle, and the change in hardness and plasticity of sandstone compression also shows a turning point. The change in sandstone surface properties started a new cycle after the 55th cycle, maintaining the previous change law.