Increased frost-heaving hazard of synthetic water repellent soil

Synthetic water-repellent soil is often used to mitigate frost heave hazards in cold regions due to its ability to reduce water transportation. However, the frost heave deformation characteristics of water-repellent soil itself are still unclear. This study examines the effect of water repellency on the freezing performance of water-repellent soil and reveals its mechanism. Samples with different degrees of water repellency were prepared. Parameters including contact angles, unfrozen water content, pore size distribution, and freezing deformation were measured. There is a positive correlation between the degree of water repellency and unfrozen water content, the growth rate of macropores, the duration of the rapid frost heave stage and the amount of stable frost heave. An increased water repellency caused increased critical nucleation work for the water-ice phase transition and shifted the dominant heat transfer mode from solid-liquid conduction to air-liquid conduction. This led to increased unfrozen water content and an extended duration of rapid frost heave. The increased water repellency also changed the ice crystal growth pattern on soil particle surfaces from attachment to detachment, leading to an increased proportion of large pores and frozen heave deformation. The above mechanisms contributed to the increased frost heave hazards of water-repellent soil.