Amount of unfrozen water in frozen porous media saturated with solution

In porous media, such as soil, some water do not freeze when cooled below 0 °C. The amount of unfrozen water is dependent on temperature and the characteristics of the porous media and solute in water. In this study, three types each of monosized glass powder, silty soil, and clay were saturated with various concentrations of NaCl, KCl, and MgCl2 solutions and subjected to freezing temperatures. The relationship between the reduction in temperature and the amount of unfrozen water was measured using nuclear magnetic resonance (NMR) technique. The amount of unfrozen water decreased with the lowering of temperature. When a porous medium was saturated with a solution, the amount of unfrozen water increased with increasing solute concentration, in the order NaCl≈KCl<MgCl2. The resulting amount of unfrozen water was considered with respect to van der Waals and Coulombic interactions and the Gibbs–Thomson effect. The amount of unfrozen water in frozen glass powder and silty soil saturated with solution at concentrations lower than 0.1 mol l−1 can be estimated when its Hamaker constant, specific surface area, distribution function, and initial solute concentration are given.