Synergistic Effects of Polyaluminum Sulfate and Phosphogypsum on Sulfoaluminate Cement : Insights into Properties and Hydration Behavior

Phosphogypsum (PG), as a byproduct, holds significant potential for reducing alkali concentration in sulfoaluminate cement systems and stabilizing corrosive ions in seawater. However, its application is hindered by several challenges, including excessive fluidity, accelerated setting time, and reduced strength, which limit its practical dosage. To overcome these challenges, this study proposes a ternary system, wherein phosphogypsum composite cement was evaluated with and without the addition of polyaluminum sulfate (AS). The findings revealed that the rheological properties, such as yield stress and plastic viscosity, exhibit a strong correlation with compressive strength development, where lower values of these properties are associated with improved strength gain. The incorporation of AS not only reduces the alkalinity and extends the setting time but also mitigates the strength degradation typically observed with higher PG content. Microstructural analysis showed that the ternary system demonstrated an enhanced degree of reaction, forming a dense and stable matrix that effectively encapsulated PG. Subsequent hydration processes reduced the formation of Friedel's salt and refined the pore structure. This study highlights that a well designed ternary system provides a viable, environmentally sustainable, and engineered solution for the efficient utilization of PG in cementitious materials.