Valorization of multi-solid waste for Low-carbon cementitious materials: Unveiling the hydration synergy and phase assemblage

Declining availability and rising cost of ground granulated blast furnace slag (GGBFS) drive its partial replacement with alternative aluminosilicate precursors in supersulfated cement (SSC). This study aimed to develop novel low-carbon cementitious materials (LCCMs) based on the activation mechanism of SSC. The proposed approach involved the activation of GGBFS and lithium slag (LS), utilizing kambara reactor desulfurization ash (KRDA) as alkaline activator and flue gas desulfurization (FGD) gypsum as sulfate activator. The effects of FGD gypsum dosage and the ratio of LS replacing GGBFS on compressive strength, hydration characteristics, phase assemblage and microscopic morphology were systematically investigated. The results showed that the compressive strength of the developed LCCMs was governed by sulfate-dependent balance between ettringite (AFt) crystallization and C–(A)–S–H gels formation. An optimized formulation achieved a 28-day compressive strength of 47.1 MPa, owing to the coordinated formation of AFt and highly polymerized C–(A)–S–H gels. LS contributed additional Al3 + and SO4 2-, but excessive LS disturbed the phase balance by introducing insert phases and excess SO4 2-. Environmental and economic assessment further demonstrated that the optimized LCCMs reduced global warming potential by 93.2% and total cost by 36.5% compared with portland cement. This study provides a feasible strategy for converting multiple industrial by-products into high-performance LCCMs through regulated alkali-sulfate activation and precursor balance.