Compensation-deterioration effect of phosphogypsum-red mud-based backfill under chloride salt conditions and wet-dry cycles.

A phosphogypsum-red mud-based backfill system maintains residual strength and meets safety standards after 12 wet-dry cycles in 11% NaCl solution, with a chloride resistance threshold of 4%.

• Why it matters: Understanding long-term performance and heavy metal stability of industrial waste-based backfill under chloride-rich groundwater erosion is crucial for safe, sustainable mining practices.
• What they did: A multisource industrial solid waste system (PRFQ) was prepared from phosphogypsum, red mud, fly ash, and quicklime, and its degradation was studied after 12 wet-dry cycles in NaCl solutions of varying concentrations.
• The result: At 50 wt% PG and specific ratios, the residual strength was 1.82 MPa with 13.12% mass loss, and heavy metal leaching met Class III standards; chloride influences microstructure, with low Cl- promoting bonding and high Cl- causing degradation, while wet-dry cycles both accelerate and mitigate deterioration.