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.
Deng et al. (Mon,) studied this question.