Changes in color and roughness of red sandstone at high temperatures

摘要

In this paper, thermal shock experiments at different temperatures and cycles were carried out on red sandstone. Its surface properties, including color and roughness, were systematically studied. The results show that the color change of sandstone is mainly related to two compositions: one is goethite, the other is calcium carbonate (CaCO3). The oxidation of goethite makes the sandstone redder, and the migration of CaCO3 makes it whiter. The sandstone is reddest at 550 degrees C and whitest at 700 degrees C. When the temperature is more than 550 degrees C, a white coat appeared on the surface of the sample. This process can be thought of as the migration of CaCO3 from the inside to the surface. The color parameters changed significantly around 550 degrees C and after 2, 3, and 4 cycles. The roughness variation of sandstone is not obvious due to not enough thermal shock cycles. The white coat can reduce the roughness of the sandstone to a small extent. The temperature of 550 degrees C is the critical threshold in this study which has important implications for red sandstone because it has a severe influence on the surface properties of red sandstone.