Experimental Study on the Mechanical Properties and Water Stability of Loess Stabilized with Calcium Carbide Residue and Phosphogypsum

Loess is susceptible to disintegration and strength loss upon water exposure, which may compromise the stability of loess subgrades. Conventional stabilization methods using cement or lime are relatively costly and involve substantial carbon emissions. To investigate the potential use of industrial solid wastes for loess stabilization, this study examined the effects of calcium carbide residue (CCR) and phosphogypsum (PG) on the unconfined compressive strength (UCS) and water stability of loess. Sixteen mixtures with different CCR and PG contents were prepared and tested. The results showed that the combined addition of CCR and PG improved both the strength and water stability of loess, indicating a positive combined effect between the two additives. The highest UCS of 520 kPa was obtained with 4% CCR and 18% PG, and the corresponding water stability coefficient was 84.1%. Further X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses suggest that the combined addition of CCR and PG promotes the formation of calcium silicate hydrate (C-S-H), calcium aluminosilicate hydrate (C-A-S-H), and needle-like ettringite (AFt) crystals. These reaction products fill the pores and bind the soil particles together, resulting in a denser and more coherent soil structure. The findings provide a reference for the utilization of industrial solid wastes in loess stabilization.