Effect of Salt Concentrations on the Freeze–Thaw Behavior of Soils

The occurrence of freeze–thaw cycles within the soil can result in adverse consequences such as frost heaving and a reduction in stiffness during thawing. The freezing behavior and subsequent thaw-weakening of soils can be influenced by the salt concentration in soils, which is affected due to road deicing operations during the winter. The presence of salt concentrations in soils induces a phenomenon known as freezing point depression, resulting in a decrease in the formation of ice within the soil. Concurrently, an elevated concentration of salt triggers osmotic suction as a result of the expulsion of ions towards the freezing front during the process of ice formation. These two phenomena can potentially result in either a decrease or an increase in the vulnerability of soils to frost action. The present study aims to examine the influence of varying salt concentrations on the freeze–thaw susceptibility of soil. The soil samples were treated with various salt concentrations, including 0.2%, 1%, and 5% NaCl solutions, as well as a control prepared with deionized water. The experiment involved determining the freezing point depression resulting from the presence of salt, and it was observed that the degree of depression increased in proportion to the concentration of salt. The specimens underwent a freeze–thaw test in a one-dimensional manner. During the experiment, measurements were taken for heave, temperature, and water intake. Additionally, the moisture content of the specimen was determined at various depths following the freeze–thaw test. In order to comprehend the distribution of salt within the specimen following a freeze–thaw cycle, the salt concentration of the specimens was assessed at various depths. This was achieved by measuring the electrical conductivity of pore water using a 1:5 soil-to-water extraction method. The findings indicated that the freezing point depression exerted a greater influence compared to osmotic suction, resulting in a decrease in the formation of ice within soils. The specimens treated with salt exhibited a reduction in the heave of up to 31% when compared to the control prepared with deionized water, due to lower ice segregation. Large variations in moisture content and salt concentration were observed between different specimens and along the specimen height after the freeze–thaw test. It can be concluded that freezing point depression has a greater influence over osmotic suction at above salt concentrations during freeze–thaw. Hence, the presence of salt can aid in the mitigation of freeze–thaw damage in soils.