<jats:p>The urgent need to mitigate the carbon dioxide footprint of cement production has driven the development of innovative blended cements. The focus of this study was a hybrid system integrating sulfoaluminate cement (SAC), ground granulated blast-furnace slag (GGBFS) and fly ash (FA), with desulfurisation gypsum (DG) as a functional addition to balance performance and sustainability. Life cycle assessment revealed that the optimised blended cement formulation achieved a 70% reduction in carbon dioxide emissions compared with conventional ordinary Portland cement, primarily attributed to 50% SAC replacement and reduced clinker dependency. The experimental results demonstrated that 4% DG incorporation enhanced the 28-day compressive strength and reduced the chloride diffusion coefficient, correlated with a refined pore structure and suppressed harmful phase transitions. Microstructural analysis confirmed that the DG modulated the hydration kinetics, which promoted continuous ettringite formation and reduced the pores of size &amp;gt;50 nm by 17.7% at 28 days, thereby enhancing matrix densification. The synergy within the GGBFS–FA binary system under DG modulation established a viable pathway for sustainable cement design, addressing the goals of both reducing carbon dioxide emissions of construction materials and industrial waste valorisation.</jats:p>