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As service years increase, the corrosion of steel rebar stands out as a major problem for existing reinforced concrete (RC) structures in corrosion-inducing environment. The mechanism of steel corrosion in concrete is an electro chemical process, which is often accelerated by the ingress of aggressive chemicals, for example chloride ion. The accumulation of corrosion products on steel rebar is able to generate circular stress which could result in cover cracking. Corrosion of steel rebar will degrade the physical appearance and reduce its original cross section. Corrosion often appears to be non-uniform and localized. Corrosion damaged RC elements displayed smaller yield strength, ductility, energy dissipation capacity, etc. Corrosion level of stirrup tends to be higher than longitudinal rebar due to smaller diameter and less cover protection. Stirrup corrosion decreased confinement behaviour on concrete, thus exacerbating the degeneration of the deformation capacity and the ductility of the RC structures. The corrosion of reinforcement steel bars (rebar) is a natural electrochemical reaction RC structures have to face with. It is exacerbated by exposure to corrosion-inducing environment factors, including de-icing salt, marine salty water, carbon dioxide, sulfur dioxide, etc. The chloride from salt (NaCl) could make hazardously chemical attack on steel bar by acting as an efficient catalyst in the corrosion process. The corrosion of steel bar in the existing reinforced concrete structure has raised great concern over its safety and seismic performance among practising engineers, researchers and residents, etc., because steel bar is the most essential element in RC. Corrosion reduces the effective cross-section area of longitudinal and transverse rebars.
Due to a small concrete cover of transverse rebars compared with longitudinal rebars, the corrosion of them becomes earlier and more severe, leading to cracks in concrete, a decrease of confinement, an intensification of reduction in deformation capacity and ductility of reinforced concrete structures. For this purpose, an experimental investigation is carried out on reinforced concrete specimens include spiral and stirrup and the variables include the corrosion percentage, rebar diameter, transverse rebar pitch, and confined core diameter. Results demonstrate that the high degree corrosion has a fewer significant effect on the reduction in confinement strength, and smaller-sized transverse reinforcements are less sensitive to corrosion.

Keywords: Chloride Attack, Spiral, Stirrup, Compressive Capacity, Confined Concrete Strength

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