Pore water freezing characteristic in saline soils based on pore size distribution

Abstract Pore water freezing point and unfrozen water content heavily depend on the properties of ion solutions, ice–liquid interface energy, and pore radius and are essential for analyzing the thermal and mechanical behavior of saline soils in cold regions. This paper focuses on the analyses of pore water freezing characteristics and estimation of the unfrozen water content in saline soils. Based on the thermodynamic principles, a general equation based on the chemical potential was used to describe water freezing in chloride saline soils and derive analytical models for predicting the freezing point and unfrozen water content. Meanwhile, the initial freezing point and unfrozen water content data were obtained by cooling experiments and nuclear magnetic resonance tests, respectively, for validating the proposed analytical models. The results show that the freezing point of saline soils is closely related to water activity, pore size, and unfrozen water content. Specifically, the freezing point decreases with decreasing water activity, pore size, and unfrozen water content. Furthermore, pore water freezing is mainly determined by the solution properties for pores larger than 0.2 μm. For pores smaller than 0.2 μm, however, the effect of pore size on water freezing should be considered. Experimental data provide validation of the analytical models for saline silty clay. Additionally, the proposed models are also shown to provide improved prediction of unfrozen water content for nonsaline silty clay.