Influence of autoclaved pretreatment on the properties of phosphogypsum-based composite binders

Phosphogypsum-based composite binder (PGCB) has been made from autoclaved phosphogypsum (PG), fly ash, lime, Portland cement and a chemical activator. The influence of autoclaved pretreatment on the properties of PG and PGCB has been investigated. It was found that the crystalline phases of original PG could be transformed, the impurities of original PG also could be effectively removed by the autoclaved pretreatment process. Under the optimum autoclaved pretreatment conditions (autoclaving at 180 °C for 6 hours), the dry compressive strength of PGCB mortars after 28 days was 31.8 MPa and the ratio of the compressive strength in wet-saturated state to that in dry state (W/D) was 0.59. PGCB mortars show good properties and water resistance with the suitable autoclaved pretreatment.