Synergistic mechanism of desulfurization gypsum and carbide slag in no-clinker supersulfated cement

The synergistic roles of desulfurization gypsum (DG) and carbide slag (CS) in no-clinker supersulfated cement (NC-SSC) were examined in this study. In this system, ground granulated blast furnace slag (GGBS) and fly ash (FA) served as aluminosilicate precursors, while DG and CS acted as the sulfate and alkaline solid activators within the binder system. The influence of DG and CS contents on strength evolution and hydration behavior was evaluated. The mix containing 20 wt% DG and 1 wt% CS exhibited the best overall performance, reaching compressive strengths of 53.8 MPa at 28 days and 63.2 MPa at 90 days. The hydration products were dominated by ettringite and C–(A)–S–H. Increasing DG content retarded early hydration but favored later ettringite formation, matrix densification, and long-term strength development. CS promoted precursor dissolution and early product formation, whereas excessive CS (≥2 wt%) hindered subsequent hydration, coarsened the pore structure, and weakened long-term strength development. A preliminary material-level assessment indicated that NC-SSC had substantially lower energy consumption, CO 2 emissions, and cost than PC and conventional SSC. These results indicate that DG and CS form a synergistic activation system in NC-SSC, jointly governing its hydration behavior and mechanical performance.