Development and Field Application of Phosphogypsum-Based Soil Subgrade Stabilizers

A phosphogypsum-based subgrade stabilizer (PBSS) was formulated using industrial by-product phosphogypsum (PG), mixed with slag and calcium-silicon-rich active material (GSR). The active powder (AP) was used to modify PBSS, and PBSS-AP was obtained. PBSS and PBSS-AP were each mixed with 10% silty soil, and cement and lime (CAL: 5% lime + 2% cement) were used as the traditional material for comparative experiments. Samples were cured under standard conditions, and tested for unconfined compressive strength (UCS), water stability, volume expansion, and leachate, to explore the stabilization effect of the three solidified materials on silty soil. The results showed that the comprehensive performance of sility soil mixed with 12% PBSS-AP was the best. The CaO, SiO2 and Al2O3 provided by PG, Slag and GSR will react with water to form a stable C-S-H gel, which is conducive to stabilizing the soil. Field application results showed that the compaction exceeded 95%, the deflection was 144.9 mm, and UCS was 2.5 MPa after 28 days. These findings indicated that PBSS-AP is an effective stabilizer for subgrade soils.