Laboratory Evaluation for Utilization of Phosphogypsum through Carbide Slag Highly-Effective Activating Anhydrous Phosphogypsum

Carbide slag was used as an activator to improve the activity of anhydrous phosphogypsum. Carbide slag could greatly improve the mechanical strength of anhydrous phosphogypsum than K2SO4. The compressive strength of 11 wt% carbide slag and 1 wt% K2SO4 activated anhydrous phosphogypsum increased greatly to 8.6 MPa at 3 d, and 11.9 MPa at 7 d, and 16.0 MPa at 28 d, respectively. The rate of hydration heat was accelerated and the total hydration heat was increased, and more calcium sulfate dihydrate was formed and cross-linked with other parts which improved the compressive strength of anhydrous phosphogypsum under the effects of different activators. It was indicated that carbide slag was a highly effective and cost-efficient activator. The result provides a highly effective and low-cost method which results in a novel and high value-added method for the utilization of phosphogypsum in the future.