Cement-bonded　calcareous　sand　(C-BCS)　demonstrates　promising　potential　for　marine　island　construction　due　to　its　exceptional　mechanical　properties.　However,　challenges　such　as　freshwater　scarcity　and　the　erosive　effects　of　seawater　hinder　the　extensive　utilization　of　C-BCS.　To　address　this,　this　study　comprehensively　examines　the　feasibility　of　incorporating　supplementary　cementitious　materials　(SCMs)　and　seawater　in　C-BCS,　focusing　on　macroscopic　properties,　microscopic　mechanisms,　and　strength　prediction.　Macroscopic　tests　reveal　that　blast　furnace　slag　and　silica　fume　effectively　enhance　the　hydration　process　and　mechanical　properties　of　C-BCS.　Moreover,　the　cemented　specimens　developed　in　this　study　partially　meet　the　strength　standards　for　road　pavement　sub-base　and　airport　runway　upper-base　applications.　Microscopic　analyses　indicate　that　calcareous　sand　serves　as　a　plentiful　source　of　calcium,　facilitating　the　formation　of　calcium　aluminate　silicate　hydrate　(C-AS-H)　and　tobermorite　when　combined　with　Al2O3　and　reactive　SiO2　from　slag　and　silica　fume.　This　enhances　the　mechanical　properties　of　the　samples　and　their　resistance　against　seawater　erosion.　Additionally,　a　back　propagation　(BP)　neural　network　model　accurately　predicts　the　unconfined　compressive　strength　of　the　cemented　specimens.　The　findings　of　this　study　support　the　broader　implementation　of　SCMs　and　seawater　in　practical　island　engineering　projects　involving　C-BCS.