This study presents a seawater-resistant low-heat cement (SRLHC) synthesized from industrial byproducts, where blast furnace slag (73.3%) and fly ash (15%) were synergistically activated by a tailored silicate cement clinker-gypsum-sodium sulfate system (1%-4%-6.7%). Through D-optimal mixture design and seawater curing experiments, regression models correlating component ratios with compressive strength were established, yielding optimal 3-day and 28-day strengths of ​​27.3 MPa​​ and ​​53.5 MPa​​, respectively. Microstructural characterization revealed a dual-phase hydration mechanism: 1) Initial hydration: Sodium sulfate reacted with clinker-derived Ca(OH)₂, generating an alkaline environment. This accelerated vitreous phase dissolution and led to the formation of ettringite (Aft) rods and calcium silicate hydrate (C-S-H) gels, which filled pores without expansive stress. 2) ​​Long-term curing​​: Seawater-introduced [SO₄]^2- reacted with residual Ca²⁺ to produce gypsum dihydrate, while continuous slag dissolution enhanced C-S-H gel formation, further densifying the matrix. Compared to conventional P·O 42.5 cement, SRLHC exhibited ​​40-47% higher strength​​ and ​​105.4% seawater corrosion resistance​​, attributed to the synergistic interplay of Aft and C-S-H. This work provides a sustainable strategy for marine infrastructure by valorizing industrial solid wastes while addressing durability challenges in saline environments.

Keywords: Industrial solid waste, Optimal ratio, Heat of hydration, Seawater erosion resistance, Microstructure.