Effects of Gypsum Type, Content and Slag on the Performance of Sleeve Grouting Materials

• Titanium gypsum increases the yield stress and plastic viscosity of the grout paste, resulting in reduced flowability, yet it effectively promotes the formation of AFt crystals and densifies the microstructure. • Appropriate addition (5%) of both titanium gypsum and dihydrate gypsum enhances the compressive strengths of sleeve grout. • The blended cementitious system of titanium gypsum and ground granulated blast furnace slag exerts a significant synergistic effect in sleeve grouting materials. To explore the potential of solid waste materials in sleeve grouting materials and enhance the comprehensive performance of sleeve grouting materials in prefabricated structures, this study investigates the effects of two types of gypsum (titanium gypsum and dihydrate gypsum) and ground granulated blast furnace slag (GGBS) contents on the workability and mechanical properties of grouts, based on a blended cement system of Portland cement and calcium sulphoaluminate cement. The flowability, rheological behavior, and compressive strength were evaluated, combined with microstructural analysis via SEM and XRD to elucidate the intrinsic mechanisms. Results indicate that appropriate incorporation of titanium gypsum (5%) significantly promotes ettringite (AFt) formation, refines the microstructure, and enhances both mid-term and long-term strength, outperforming dihydrate gypsum. Moreover, the addition of ground granulated blast furnace GGBS exhibits a parabolic influence on grout performance, with an optimal content of 25% yielding improved 28-day compressive strength and densified microstructure. The findings confirm the synergistic effect of titanium gypsum and GGBS in the blended cement system, offering a promising pathway for developing high-performance, eco-friendly grouting materials and achieving value-added utilization of industrial solid wastes.