Feasibility study of stabilizing soft soil in the Jianghan Plain using one-part alkali-activated materials developed by iron and steel slags

The stabilization of soft soil subgrade is essential for infrastructure development in lacustrine regions; however, conventional cement stabilization faces challenges related to limited applicability and high carbon emissions. This study developed a one-part alkali-activated material (OPAAM) using alkali-fused steel slag (AFSS) and granulated blast furnace slag (GBFS) for stabilizing soft soil from the Jianghan Plain, China. Response surface methodology, multi-objective particle swarm optimization, and entropy-weighted TOPSIS were used to optimize strength, workability, CO₂eq, and cost. The optimized OPAAM was prepared with a precursor blend containing 29.0 wt% AFSS and 71.0 wt% GBFS, with sodium silicate and borax externally added at 9.1 wt% and 3.4 wt%, respectively, based on the total precursor mass. At this proportion, OPAAM reduces CO₂eq by 82% compared with cement. Soft soil stabilized with 16 wt% OPAAM achieved a 28 d compressive strength of 3.9 MPa, exceeding that of the 20 wt% cement-stabilized control, while reducing CO₂eq and cost by 85.6% and 17.6%, respectively. Microstructural analyses showed that C-(N-)A-S-H gel and hydrotalcite were the main hydration products of OPAAM, which filled pores and bound soft soil particles and served as the primary source of strength in the stabilized soft soil. Heavy metals leaching concentrations of OPAAM stabilized soft soil remain far below regulatory limits, confirming its environmental safety. This study provides theoretical and practical insights into the production and application of low-carbon soft soil stabilizers.