Study on Comprehensive Properties of Cement-based Backfill based on Phosphogypsum Modification

This is an article in the field of ceramics and composites. In order to improve the comprehensive utilization of mineral resources and mining technology, mine filling materials are prepared from mineral solid wastes such as phosphogypsum, cement and tailing sands as aggregates, analytical studies of the slurry's comprehensive search performance, mineral composition and microscopic morphology are carried out, and the molecular structure of hydrides is discussed in conjunction with molecular dynamics simulations. The results showed that the addition of phosphogypsum significantly increased the slump of the modified filler, decreased the bleeding rate, and the compressive strength showed a rising trend. The strength value of the modified filler increased significantly with the curing time. The strength of phosphogypsum modified backfill after curing for 28 d is about 1.2 times that of cement backfill. Calcium silicate hydrate and ettringite in phosphogypsum modified filling materials are the main hydration products. SEM image shows that the microstructure of phosphogypsum modified filling materials is relatively compact and there are few micro-cracks. The numerical simulation results show that the elastic modulus of calcium silicate hydrate is higher than that of ettringite. The key to improving the strength of filling material is to promote the formation of calcium silicate hydrate.