The Effect of Freeze–Thaw Cycles on the Macro- and Microstructure Properties of Stabilized Clay Soil Using WGP and CCR Geopolymer

Freeze–thaw (F-T) cycles are natural processes that affect the geotechnical properties of seasonally frozen soils. These soils cover about 50% of the Earth’s area. Clayey soils are common in cold regions. They are typically soft and weak. They are also more vulnerable to F-T cycles than coarse-grained soils. Therefore, studying the effects of F-T cycles on clayey soils is essential. This study utilized geopolymer binders composed of waste glass powder (WGP = 0%, 5%, 10%, 15%, and 20% by weight) and calcium carbide residue (CCR = 0%, 3%, 7%, 10%, and 13% by weight) to stabilize natural clay. Unconfined compressive strength (UCS) tests were conducted to find the optimum additive amounts. Direct shear and permeability tests were also performed. Microstructural changes were analyzed using scanning electron microscopy images, energy-dispersive X-ray spectroscopy, and BET tests. Samples were cured for 7 and 28 days. Then, they were subjected to F-T cycles in a closed system (F-T cycles = 0, 3, 6, 9, and 12). The sample with 15% WGP and 7% CCR showed the best performance. After 12 cycles, its UCS decreased by only 15%. Geopolymer formation altered the soil pore distribution in such a way that the total pore volume increased and the average pore diameter decreased. In contrast, F-T cycles had the opposite effect.