Physico-Chemical Properties of Ordinary Portland Cement Pastes after Partial Substitution of Gypsum with Thermally Treatment Phosphogypsum

The present study conducted to investigate the potential use of PG in cement industry. This was accomplished by preparing mortar mixes contain Portland cement clinker (PPC) with thermally treated PG at different temperatures (200, 400, 600, 800 and 1000 °C) instead of raw gypsum (RG) at different proportions. The characteristics of prepared mortars were investigated after curing in water for different periods (3, 7, 28 and 90 days) by determination of setting time, compressive strength, bulk density, and total porosity. The hydration kinetics was evaluated by determination of free lime and chemically combined water contents. FTIR spectroscopic analysis was used to investigate the change in structure of some mortars after curing. The change in morphology and microstructure of hardened pastes was investigated using scanning electron microscopy (SEM). The results approved the possibility for the utilization of treated PG at 800 and 1000 °C instead of raw gypsum in cement industry.