Effect of freeze-thaw cycles on the mechanical performance of wheat straw biomass ash modified soil

In cold regions, freeze-thaw cycles (FTCs) can alter the properties of soil used as a foundation filler, leading to failures in foundation engineering. The increase in biomass power plants has resulted in a significant amount of waste biomass ash, causing negative environmental impacts. To address these issues, waste wheat straw biomass ash (WSBA) is harnessed to enhance the properties of silty clays. This study examines how WSBA affects the mechanical properties and microstructure of silty clay after FTCs through FTCs tests, Triaxial tests, and Scanning Electron Microscopy (SEM) tests. The findings reveal that incorporating WSBA significantly enhances the mechanical properties and microstructure of the soil by filling internal pores and strengthening its structure. The mechanical properties of all soil samples exhibit significant deterioration after 1 FTC, with gradual stabilization ensuing after 6 FTCs. Notably, WSBA-modified samples show better resistance to freeze-thaw weathering compared to unmodified samples, particularly at a WSBA content of 10%. Furthermore, the study establishes empirical formulas linking mechanical parameters, freeze-thaw cycles, and WSBA content using binary quadratic equations. The investigation results could serve as a valuable reference for projects involving roadway subgrade backfill materials in regions with seasonal frozen soil.