Cement-bonded　calcareous　sand　(C-BCS)　can　effectively　enhance　the　strength　of　calcareous　sand,　which　is　widely　in　infrastructure　construction　on　islands　in　the　South　China　Sea,　and　can　fulfil　the　engineering　requirements　of　island　pavement　subbase.　However,　the　enhancement　mechanisms　and　meso-generalized　structural　character-istics　of　C-BCS　under　different　water　environments　and　cement　dosages　are　unclear.　In　this　study,　we　consider　the　unconfined　compressive　strength　as　an　evaluation　index　to　quantify　the　degree　of　hydration　reaction,　change　of　hydration　products,　and　meso-generalized　structure　of　C-BCS　in　freshwater　and　seawater.　We　performed　analyses　using　electrochemical　impedance　spectroscopy,　X-ray　diffraction,　and　scanning　electron　microscopy.　The　results　demonstrate　that　C-BCS　can　satisfy　the　strength　requirements　of　highway　and　airport　runway　subbases　with　10%　and　15%　cement　admixture,　respectively.　Furthermore,　the　corrosion　deterioration　phenomenon　occurs　and　spreads　in　C-BCS　in　seawater.　The　internal　hydration　process　of　C-BCS　can　be　continuously　monitored　using　the　electrochemical　impedance　spectroscopy　test,　and　a　correlation　between　the　electrochemical　and　mechanical　parameters　at　different　ages　is　proposed.　The　meso-generalized　structure　inside　the　C-BCS　can　be　densified　by　the　bridging　and　pore　filling　effects　of　hydration　products　on　calcareous　sand　particles,　thereby　improving　the　strength　of　calcareous　sand.　Additionally,　we　provide　a　concrete　mechanistic　explanation　underlying　the　forming　strength　of　C-BCS,　and　an　optimized　design　approach　of　C-BCS　considering　several　complex　engineering　properties.