Flexural performance of seawater sea sand concrete beams reinforced with high-corrosion-resistant bars after dry and wet cycles of seawater

To address durability issues in seawater sea-sand concrete (SSC) caused by chloride-induced reinforcement corrosion, this study proposes a composite material system that integrates high-corrosion-resistant bars with modified seawater sea-sand concrete (HCRB MSSC). A series of three-point bending tests were conducted on six reinforced concrete beams fabricated under different conditions to systematically investigate the flexural behavior and degradation mechanisms of HCRB-MSSC beams under wet–dry cycles. Experimental results indicate that the chloride-binding agent in SSC effectively mitigated corrosion, reducing the corrosion ratio of conventional rebar (CR) MSSC beams by 29.6 % compared with conventional reinforced concrete (RC) beams. When combined with HCRB, the corrosion ratio was further reduced to 0.7 % after 120-day wet dry cycles, accompanied by an improvement in ultimate flexural capacity. Specifically, the HCRB MSSC beam exhibited a 13.4 % higher ultimate load capacity than conventional RC before exposure, and this advantage increased to 25.7 % after seawater cycles. A finite element model was subsequently developed to quantify the influence of key parameters, demonstrating that higher reinforcement ratios enhance post-cracking stiffness, whereas increasing the shear span-to-depth ratio reduces ultimate capacity. Finally, code-based predictions from GB, EN, and ACI standards were compared with experimental and numerical results. The findings provide practical guidance for developing resource-efficient and corrosion-resilient marine infrastructure systems.