Development and property optimization of a sustainable phosphogypsum-based cementitious system with ground-granulated blast furnace slag and carbide slag

beta-hemihydrate phosphogypsum (beta-HPG) is a promising renewable building material with the potential to reduce phosphogypsum (PG) stockpiles significantly. However, its application is hindered by the low mechanical strength, subpar water resistance, and presence of hazardous components. In this study, ground-granulated blast furnace slag (GGBS) and carbide slag (CS) were together with beta-HPG into a high-performance and sustainable phosphogypsum-based cementitious material system (PCMS). Various PCMS specimens were prepared by mixing beta-HPG (60 %-100 %), GGBS (0-40 %), and CS (0-40 %). To optimize the PCMS properties, the mechanical, water resistance, and toxicity stabilization investigations of PCMS specimens were performed. Also, the mineralogical and microstructure characteristics of PCMSs were analyzed. The results highlighted that ternary PCMS presented excellent compressive strength and softening coefficient, with low water absorption and P, F leaching concentrations. The formulation with 60 wt% beta-HPG and a GGBS/CS ratio of 3:1 showed the best overall property. The primary hydration products included ettringite (AFT), C-(A)-S-H gel, and dihydrate gypsum, contributing to strength development, water resistance, and toxicity stabilization of PCMS. Furthermore, The increased proportion of GGBS promoted the formation of hydration products, improving the gypsum crystal structure and thus optimizing the properties of PCMS. This study provides valuable insights for further development of green building materials and environmental protection.