Re−utilization of Ca−based and Na−based desulfurization by−product as alternative sulfate activator in supersulfated cement system: Mineral transformation and reaction mechanism

Expanding the availability scope of sulfate activators in supersulfated cement (SSC) systems will further the development of low–carbon cementitious materials techniques. The use of industrial solid wastes with comparable properties in SSC systems shows significant potential. However, the types of potential sulfate activators and their impacts on SSC performance remain inadequately defined. To address this gap, this study explored the feasibility of substituting gypsum with desulfurization gypsum (DG) and sodium−based desulfurization ash (SDA) as alternative sulfate activators in SSC. The workability, setting time, thermodynamic processes, dissolution characteristics, and mechanical properties of SSC systems prepared with various sulfate activators were characterized comprehensively, and the phase compositions and reaction mechanisms were elucidated using multiple microscopic techniques. The results indicated that fluidity and consistency were primarily dependent on the physical characteristics of the sulfate activators, while setting time was more strongly influenced by chemical dissolution and hydration processes. DG–SSC exhibited thermodynamic, phase composition, and mechanical properties similar to those of G–SSC. The incorporation of SDA increased the system’s pH value and facilitated the dissolution of slags, shifting the product system from ettringite−driven to gel−driven. The formation of gel products optimized matrix densification and enhanced compressive strength. This study not only provides a scientific basis for the application of desulfurization by−products in SSC systems but also offers additional insights into the resource utilization of desulfurization by−products, contributing to the sustainable development of the construction materials industry.