Brine Drying and Salt Precipitation in Sandy Soil and Its Impact on Thermal Conductivity

Saline water evaporation and salt precipitation in porous media are prevalent in many arid and coastal areas, posing significant environmental and engineering challenges while offering the possibility of enhancing the thermal conductivity of granular materials. Evaluating the impact of salt precipitation and developing effective strategies to manage and utilize saline soils in affected regions requires a comprehensive understanding of precipitation dynamics. This study examined the salt precipitation distribution induced by brine drying and evaluated its influence on soil thermal conductivity. The salt content profile along the depth was determined after drying within sandy soils under various brine concentrations, saturation levels, and drying temperatures. X-ray computed tomography was used to characterize precipitation patterns at the pore scale. Each sample's thermal conductivity was measured after drying to assess the impact of salt precipitation. Results show that thermal conductivity enhancement depends on both salt content and pore habit. Salt cementation occurs when precipitation initiates at low brine content with disconnected small brine clusters, enhancing the contacts between particles and linearly increasing thermal conductivity. Conversely, if salt precipitation starts at higher brine content, large brine clusters remain interconnected, and capillary-driven flow brings water and salt to the drying front, leading to pore-filling salt within the sample, which has a limited impact on thermal conductivity.