Multiscale Analysis of Chloride Ions Transport in Seawater Geopolymers with Multiple Solid Precursors

The global shortage of freshwater resources has prompted increasing interest in seawater-activated geopolymer binders as sustainable alternatives to conventional cement. This study investigates the multiscale mechanisms of chloride ion transport in seawater-based geopolymers prepared from ground granulated blast furnace slag, fly ash, and silica fume. Experimental tests, including rapid chloride permeability, X-ray diffraction, and scanning electron microscopy, were combined with molecular dynamics simulations to establish the relationship between chloride migration and microstructural evolution. The results reveal that seawater activation promotes synergistic interactions among Ca²⁺, Mg²⁺, and Al(OH)₄⁻ species, facilitating the formation of dense N-A-S-H/C-A-S-H networks and enhancing chloride binding. The optimized mixture achieved a diffusion coefficient of 4.97 × 10⁻¹³ m²/s, indicating a substantial improvement in resistance to chloride ingress compared with ordinary Portland cement. This research provides a multiscale understanding and design basis for developing durable seawater geopolymer materials for marine infrastructure.