Influence of Industrial Waste Gypsums in Excess-Sulfated Slag Cement: The Role of Wet Grinding

The rational utilization of industrial solid waste is an effective way to reduce environmental pollution. This study investigated the potential application of fluorogypsum (FG), flue gas desulfurization gypsum (FGD), phosphogypsum (PG), and titanium gypsum (TG) in the production of excess-sulfated slag cement (ESSC). It further investigated the effects of different types of gypsum on the performance and hydration process of ESSC through a wet grinding process. The results showed that as the pH value of the gypsum increased, the setting time of ESSC decreased, and hydration heat release occurred earlier. Phase analysis and microstructural characterization indicated that the type of gypsum affected the hydration rate, microstructure, and quantity of hydration products of ESSC, thereby influencing its compressive strength. To further improve the performance of ESSC, a wet grinding process was employed to enhance particle activity and promote hydration reactions. PG, due to its high solubility, demonstrated a better activation effect; after wet grinding, the 28 d compressive strength reached 40.03 MPa. Meanwhile, ESSC pastes prepared with high-pH FG exhibited not only good early strength (3-day strength of 21.93 MPa) after wet grinding but also excellent water resistance, with a softening coefficient of 0.96. This study clarifies the impact of gypsum type on ESSC performance and provides valuable insights for enhancing its properties.