Abstract: Sulfate saline soils are widely distributed in Xinjiang, where salt expansion often leads to road cracking and damage. This study investigated the effectiveness of a method that combines fly ash, slag, and polyacrylamide (PAM) in treating saline soils. Various tests, including salt expansion, boundary moisture content, pH, total dissolved solids (TDS), electrical conductivity (EC), sulfate ion concentration, unconfined compressive strength, and freeze-thaw cycle tests, were conducted to evaluate the mechanical and physicochemical properties of the solidified soil. Moreover, scanning electron microscopy (SEM) was utilized to explore the enhancement mechanism and microscopic features. The results indicate that the inorganic-organic combination of fly ash, slag, and polyacrylamide effectively suppresses salt expansion in sulfate saline soil, enhancing its mechanical properties, plasticity, and frost resistance. Considering economic feasibility and practicality, the optimal ratio was determined: a mixture of fly ash, slag, and PAM at 15%, with PAM at 2%. Under these conditions, the treatment exhibits the most efficient inhibition of salt expansion and improves structural integrity. The 7-day unconfined compressive strength of the treated soil reaches 993 kPa, three times higher than that of natural soil. Additionally, the soil demonstrates a significant enhancement in freeze-thaw resistance.

Key words: sulphate soil, fly ash, slag, polyacrylamide, stabilized soil