Study of untreated phosphogypsum as a fine aggregate for magnesium oxysulfate cement

Phosphogypsum (PG), an industrial waste containing phosphorus, has resulted in accumulation and environmental pollution because of its shallow utilization rate worldwide. In this paper, unpretreated PG is incorporated into magnesium oxysulfate cement (MOSC) as an insert fine aggregate at different dosing levels. The performance of the resulting mortar is evaluated by testing workability, volume stability, mechanical properties, water resistance, and sustainability. Results show that PG improved the water resistance, the long-term compressive strength, and the microstructure of MOSC. XRD/Rietveld analysis and TG-DSC demonstrated that the incorporation of PG inhibited the crystallization of Mg(OH)2 and promoted the formation of 5 Mg(OH)2·MgSO4·7H2O (5·1·7 phase). Besides, some PG undergoes morphological changes that may disrupt the strength of MOSC. PG-MOSC has the potential for environmental sustainability because of its low carbon emissions and efficient toxic immobilization. The paper provides ideas and a reference for the resource utilization of PG.