MICROELECTRODE RESPONSE CHARACTERISTICS OF CAPILLARY WATER MIGRATION IN SANDSTONE CULTURAL RELICS

Salt crystallization is one of the most common issues affecting sandstone cultural relics, directly impacting their integrity through the capillary migration of soluble salt solutions. To gain a deeper understanding of capillary water migration in sandstone relics under various influences, we designed independent capillary water absorption and microelectrode resistivity test devices based on the sandstones of Dazu Rock Carvings. We then conducted a quantitative analysis of the influence of pore structures, pore solutions, dry-wet cycles, and relative humidity on capillary water migration and electrical resistivity distribution characteristics. The results demonstrate that a loose microstructure and low relative humidity promote capillary water transport. Capillary migration is notably influenced by the surface tension of the soluble salt solution, with water absorption and migration rates increasing with surface tension. Dry-wet cycles lead to the expansion of internal pores, accelerating the capillary migration rate. Additionally, there is a negative correlation between the saturation of the sample and the resistivity of the sandstone. The presence of soluble salts significantly reduces the resistivity of the sandstone. The apparent resistivity of the wetting front of the sample approximately coincides with the salt crystallization deterioration area on the sample surface, revealing temporal and spatial distribution characteristics of resistivity. Moreover, the wetting front exhibits a concave trend along the depth direction. These results unveil the laws governing capillary water migration in sandstone relics, providing theoretical support for accurately tracking the range of salt damage.