Changes in glossiness, electrical properties and hardness of red sandstone after thermal treatment

The physical properties (glossiness, hardness, capacitance and electrical impedance) of red sandstone after thermal treatment at different temperature will be performed differently. The experiments show that the entire process can be divided into three stages. (1) 100-400 degrees C: as the temperature increases, the amount of water that exists as free water inside red sandstone is reduced, and micro-cracks begin to appear at the interior. (2) 400-800 degrees C: dehydroxylation of red sandstone occurs, and the thermal expansion rate of the quartz-based minerals reaches its maximum value at 600 C. As a result, fractures develop in the sandstone and the surface becomes rougher. Meanwhile, changes in the color of red sandstone may be related to changes in iron. (3) 800-1300 degrees C: the quartz, feldspar and other minerals melt. Meanwhile, the hightemperature metamorphism of the red sandstone results in a complete color change. Smooth enamel crystals appear on the surface, which forms rocks similar to metamorphic rocks. The mineral composition and structure change before and after 800 degrees C, and the capacitance and electrical impedance change dramatically at this point. (C) 2020 Elsevier B.V. All rights reserved.