Effect of calcination temperature and superplasticizer on the properties of anhydrite II from phosphogypsum

Phosphogypsum (PG) is an industrial waste, and it can be produced anhydrous PG (APG) to utilization. The effects of calcination temperature and superplasticizer dosage on the normal consistency, setting time and compressive strength of APG were studied. With the increase in calcined temperature, the water requirement of APG normal consistency decreased. When the APG (APG6) prepared at 600 ℃ for 1 h, its final setting time was long (9.02 h). When the APG (APG8) prepared at 800 ℃ for 1 h, its had high strength (8.45 MPa) after curing 28 d. When the water-gypsum ratio for normal consistency was 0.3, the superplasticizer dosage decreased with the calcined temperature increase. The superplasticizer dosage could significantly increase the compressive strength of samples. When superplasticizer dosage was 0.09 mass%, the APG6 had the best mechanical properties. The compressive strength of APG6 was 25.45 MPa and 28.85 MPa after curing 3 and 28 d, respectively, which initial and final setting time was 3.80 and 4.83 h, respectively.