Modified phosphogypsum-low alkalinity sulfoaluminate cement cementing system and its application in vegetation-growing concrete

To address the comprehensive utilization of phosphogypsum, enhance the overall performance of vegetation-growing concrete, and achieve cost-effective rock slope restoration, this study examines the influence of modified phosphogypsum content on the physical and chemical properties of cementing materials at a low temperature of 10 °C, utilizing low-basicity sulphoaluminate cement. A specialized cementing material for vegetation-growing concrete with favorable mechanical properties and reduced alkalinity was developed, and its overall performance was validated. Isothermal calorimetry, X-ray diffraction (XRD), simultaneous thermal analysis (TG-DTG), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) were employed to compare the early hydration heat, hydration products, and microstructure of the modified phosphogypsum-low alkalinity sulphoaluminate cement system with those of ordinary Portland cement and low alkalinity sulphoaluminate cement. The findings indicate that incorporating 30% modified phosphogypsum into low alkalinity sulphoaluminate cement results in a cementing material with rapid early hydration, a compact matrix, reduced calcium hydroxide content, and superior mechanical properties. These characteristics achieve optimal comprehensive performance and exhibit favorable physical and chemical properties under low-temperature curing, meeting the requirements for vegetation-growing concrete and enhancing its overall performance.