Marine Concrete Using Recycled Aggregates with Surface Coatings Against Saltwater Attack

The durability of marine concrete is critically challenged by chloride-induced corrosion, sulfate attack, and salt crystallization due to continuous exposure to aggressive seawater environments. The depletion of natural aggregates has encouraged the use of recycled concrete aggregates (RCA) as a sustainable alternative in construction. However, RCA’s higher porosity and weaker interfacial transition zones (ITZ) increase vulnerability to saltwater attack. This study investigates the performance of marine concrete produced with recycled aggregates enhanced by surface coatings. Various coatings including epoxy resin, silane-based sealers, and nano-silica slurry were applied on RCA to reduce water absorption and chloride ingress. The experimental program evaluated mechanical strength, water permeability, chloride penetration, and microstructural changes under accelerated saltwater exposure. Results indicated that coated RCA concrete demonstrated significant improvements in compressive strength (up to 12% higher compared to uncoated RCA concrete) and reduced chloride permeability by nearly 40%. Microstructural analysis
through SEM and EDS confirmed reduced salt crystal deposition and denser ITZ. The findings highlight that
surface-coated RCA concrete provides a viable pathway for sustainable marine infrastructure, ensuring durability and reduced maintenance in aggressive coastal environments.