Influence of High-Volume Calcined Phosphogypsum on Mechanical Properties and Freeze-Thaw Resistance of Supersulfated Slag Cement Concrete.

This study investigates the effects of high-volume calcined phosphogypsum (CPG) on the workability, mechanical properties, and frost resistance of phosphogypsum slag cement concrete (PSCC). CPG was used as a sulfate activator to prepare PSCC mixtures with CPG contents ranging from 40% to 70%. The slump, flexural and compressive strengths, water absorption, relative dynamic modulus of elasticity, and mass loss rate after freeze-thaw cycles were evaluated. The results show that the slump of fresh concrete decreases from 275 mm to 35 mm as the CPG content increases from 40% to 70%. The compressive strength decreases with increasing CPG content; however, the 90-day compressive strength still ranges from 39.9 MPa to 56.4 MPa. Even at high CPG contents, the concrete maintains moderate to relatively high strength levels. At a CPG content of 40%, the water absorption rate is 5.9%, meeting the requirement of the Chinese standard JC/T 899-2016. Freeze-thaw cycle tests indicate that a higher CPG content results in a higher mass loss rate. Nevertheless, all mixtures comply with the Chinese standard JC/T 899-2016, which limits the mass loss rate to no more than 3.0% after 50 freeze-thaw cycles for curbstones. The relative dynamic modulus of elasticity shows a trend of decreasing, then increasing, with increasing CPG content.