• Mineral-interlocking strategy for the synergistic co-utilization of phosphogypsum and shotcrete waste residue is proposed. • High-pressure compaction constructed a dense interlocking microstructure. • PG-based road materials exhibit strong fluorine and phosphorus environmental safety. This work presents a novel mineral-interlocking strategy for the synergistic co-utilization of phosphogypsum (PG) and shotcrete waste residue (SWR) to develop high-performance, environmentally safe road materials. The optimal mix proportion for the PG-based binder was first determined based on response surface analysis, achieving a 7 days compressive strength exceeding 18 MPa even with a PG content > 82%. Then, PG-based road material was prepared using 5% binder to solidify 95% SWR, which exhibited a 28 days compressive strength of 8 MPa, a softening coefficient of 0.85, and a water absorption rate below 2.5%, meeting the specifications for road performance. Microstructural analysis revealed that low porosity and high binding energy induced by high-pressure compaction constructed a dense three-phase interlocking microstructure among PG crystals, hydration products, and SWR micro-aggregates. This effectively blocked capillary channels, enhancing mechanical strength and water resistance. During curing, water-soluble fluorine and phosphorus impurities in PG were stabilized by transformation into Fe-Mn oxide-bound fractions or incorporation into hydroxyapatite lattices, significantly reducing leachability and ensuring environmental safety. This work not only provides an innovative approach for the high-value, large-volume co-utilization of PG and SWR, but also offers a microstructure-based design concept for developing high-performance solid waste-derived civil engineering materials.
Wang et al. (Sun,) studied this question.