Improving the performance of phosphogypsum-based cementitious materials by controlling water consumption and introducing CaCl2

As a by-product of the phosphate industry, the large-scale stockpiling of phosphogypsum not only causes a waste of resources but also poses a serious threat to the environment. Aiming at the problem of the resource utilization of phosphogypsum, this study explored the performance improvement mechanism of phosphogypsum-based cementitious materials (PCCM) by controlling the water-binder ratio (W/B) and the CaCl2 dosage. Analysis techniques such as hydration heat, scanning electron microscopy-energy dispersive spectrometry, X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were employed to systematically uncover the hydration process, hydration products, and the microstructural evolution of PCCM. Additionally, its environmental benefits were evaluated through pH and ICP analysis. The results show that: by controlling the W/B (not exceeding 0.19) and the CaCl2 dosage (not more than 3%), the fluidity, strength (especially the early-stage strength), water resistance, and frost resistance of PCCM were significantly improved. At the same time, the setting time was effectively shortened and the bleeding rate was reduced. More importantly, the optimized PCCM had a higher pH value, which significantly reduced the leaching of phosphorus and heavy metals and met the environmental safety standards. Compared with cement, PCCM had significant advantages in carbon emissions and energy consumption, showing good environmental and economic benefits. This research provides new insights into the resourceful utilization of phosphogypsum and contributes to the advancement of green building materials.