Performance evaluation of recycled aggregate geopolymer concrete for low-carbon breakwater systems

Achieving circularity in the construction through the use of geopolymer concrete requires sustainable alternatives to natural virgin aggregates specially in the case of mass concrete application. However, the application of recycled aggregate (RA) in manufacturing concrete breakwaters for aggressive marine environments remains largely unexplored. A significant gap exists in comprehensive data regarding their long-term durability, leaching behavior, and mechanical performance under real-world coastal conditions. This study investigates the leaching behaviour and durability performance of a fly ash–GGBS-based geopolymer incorporating 100% RA and compared against conventional cement and natural virgin aggregate based concrete, targeting sustainable applications in coastal breakwater structures. Key parameters evaluated include compressive strength, porosity, chloride ion migration, electrical resistivity, and the leachability of metal ions under both freshwater and seawater exposure.