Performance optimization and combined mechanisms of fiber-FRP hybrid reinforcement systems in seawater sea sand concrete: a comprehensive review

This review examines performance optimization and the combined mechanisms of fiber–FRP hybrid reinforcement systems in seawater sea sand concrete (SWSSC) for marine infrastructure, synthesizing a consolidated corpus of 178 peer-reviewed studies published up to 2026 across material fundamentals, system configurations, mechanical performance, bond behavior, marine durability, and optimization methodologies. Properly designed hybrid configurations achieve 15–30% higher compressive strength and 20–45% enhanced flexural performance relative to plain SWSSC; consistent with a conservative, baseline-referenced reading of the evidence, these gains are treated as combined additive effects of triaxial confinement and micro–macro crack bridging rather than as proof of non-linear synergy. Optimal fiber volume fractions typically remain below 0.5%, with micro/macro combinations giving the strongest combined response, while CFRP exhibits the smallest mechanical degradation under seawater exposure relative to GFRP and BFRP—an advantage that remains conditional and bounded by accelerated-laboratory testing. Significant standardization gaps persist in bond models, long-term performance prediction, and physics-informed AI optimization. The review establishes a mechanism-driven framework and traceable design guidance for sustainable marine concrete.