Structural performance of RC beams damaged by natural corrosion under sustained loading in a chloride environment

• Corrosion process is studied under sustained loading.
• Corrosion results from natural process and then corresponds to in-situ conditions.
• Effect of exposure conditions is highlighted.
• Ductility is highly affected by corrosion.

This paper discusses the effect of corrosion on the load-bearing capacity and ultimate deflection of corroded beams exposed to wetting–drying cycles in a chloride environment under sustained loading without impressed current. The mechanical performance of one control beam and two corroded beams was tested. Corroded bars in the beams were extracted for tensile tests and the cross-sectional losses were measured. The experimental results were compared with those obtained in a previous long-term aging program in a chloride environment.The experimental results confirmed that corrosion of the reinforcements modified the failure mode of reinforced concrete beams. The control beam failed due to crushing of the concrete in the compressive zone, while deteriorated beams failed due to the rupture of one tensile bar. As a result, the maximum cross-sectional loss on tension bars allows the residual yielding and ultimate capacity to be predicted since 1% reduction in cross-section corresponds to 1% reduction in yielding capacity and ultimate capacity.The results also show the importance of the initial ductility of the steel bars. Corrosion leads to more brittle behavior of steel bars in tension but the influence of corrosion on the ductility of RC beams depends on the initial ductility of the steel bar. In consequence, highly ductile steel bars belonging to Class C according to Eurocode 2 could prevent brittle collapse of corroded RC beams because of sufficient residual ductility of the corroded steel bars.