Evaluation of the freeze-thaw performance of silane treated pavement subgrade soils

Silane can be effective in limiting freeze–thaw impact on pavement systems as it creates water-repellent properties in the substrate and can limit the water ingression to subgrade soil. While primary frost heave stems from the phase change of pore water to ice, secondary frost heave is induced by continuous water flow from the vadose zone towards growing ice lenses. Consequently, limiting the influx of water from the vadose zone could be the most efficient approach to mitigate the detrimental effects of freeze–thaw cycles on subgrade soils. This study aims to minimize the freeze–thaw effects by treating subgrade soils with silanes. Two frost susceptible soils from Iowa (IA-PC and IA-KC) were sprayed with two different dosages (1.6 L/m² and 3.2 L/m²) of silanes, and spraying was employed at multiple depths within the specimens. One-dimensional frost heave tests were conducted, and frost heave potential was measured in terms of water intake, total frost heave, heave rate, and soil water content. The silane treatment resulted in a reduction in frost heave, ranging between 57 % and 80 %. The heave rate for the untreated IA-PC specimen was 4.3 mm/day, which decreased to 0.4 mm/day with a two-layer spray treatment using a silane concentration of 1.6 L/m². Increasing the number of silane-sprayed layers was more effective than increasing the silane concentration to limit water ingress and enhance the freeze–thaw resistance of the subgrade soil.