Recycling high volume phosphogypsum in highway subgrade: Harmless, testing, and application

Based on solidification/stabilization theory, a self-made curing agent was used to stabilize the phosphogypsum, and a high-volume phosphogypsum subgrade filler was prepared. The road performance and pollution characteristics of the stabilized phosphogypsum were analyzed, and applied it to the highway subgrade of the Huiqiao Expressway in Yunnan Province. The results show that (1) moisture content is the key factor affecting the compaction degree of phosphogypsum subgrade filler; (2) after stabilization, the strength and water stability of phosphogypsum are greatly improved; (3) the curing agent reacts with fluorine ion and soluble phosphorus in phosphogypsum to form fluoride precipitation, phosphate precipitation and gel products ( C-S-H, C-A-S-H ) formed by hydration of curing agent to further physical adhesion and encapsulation to achieve fluorine and phosphorus removal; (4)through the application verification of the filling test road, the compaction degree, deflection value, rebound modulus value and pollutant leaching amount all meet the requirements of the specification.