Effect of wet-dry cycling on the pore characteristics of red sandstone after heat treatment

This study investigates the influence of thermal conditions and wet-dry cycling on the pore characteristics of red sandstone, utilizing nuclear magnetic resonance spectrometry for analysis. The red sandstone samples were subjected to elevated temperatures followed by a series of wet-dry cycles. Our findings reveal a significant alteration in the porous architecture of the sandstone samples post-thermal treatment, primarily attributed to water evaporation and mineral expansion. Particularly, after 40 cycles of wetting and drying, the total porosity of the samples increased, most notably when subjected to a temperature of 800 degree celsius, where an 88.9% increase in total porosity was observed. Furthermore, as the number of cycles increased, the internal pore connectivity improved due to water-induced effects. The volume of micropores (r < 0.1 mu m) showed a decreasing trend, while mesopores (0.1 mu m < r < 1 mu m) remained relatively constant, and the volume of macropores (r > 1 mu m) increased under the same thermal conditions. These results have important implications for rock stability monitoring and engineering protection, as they demonstrate that wet-dry cycles can significantly exacerbate the degradation of the material properties of red sandstone by increasing its effective pore volume.