A comprehensive numerical simulation system is proposed for solving the problem of steel corrosion in concrete related to deterioration of reinforced concrete structures in an environment contaminated by chloride ions. The distribution of the corrosion amount and the corrosion rate along the reinforced bar were calculated based on macro-cell circuit models consisting of micro-cell circuits. The models were quantified according to the results of exposure experiments under two environments, one under cyclic wetting and drying in a laboratory and the other in a splash zone located offshore. The comparisons on time-dependent half-cell potential, corrosion location and corrosion amount indicate qualitative coincidence between the experimental and numerical simulation results. In addition, based on the proposed system, numerical simulation of the macro-cell corrosion circuit between patched area and not-yet-patched area is reasonably achieved.

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In this study, a method was developed to estimate accurately the chloride threshold value for corrosion initiation in reinforced concrete. In this method, chlorides are supplied through a part of the specimen surface, and half-cell potential between the rebar and reference electrode embedded in a concrete specimen was measured in every ten minutes. A sudden drop of half-cell potential was observed as the continuation of the measurement. At that time, the specimen was broken and corrosion of rebar on its narrow surface was confirmed. The chloride threshold value can be estimated by determining the chloride concentration at the time of the potential drop. The estimated chloride threshold values for normal Portland cement concrete with cement content between 254 and 446 kg/m 3 are in the range of 1.6 to 3.6 kg/m 3. This paper is an English translation from the authors' previous work [Horiguchi, K., Yamaguchi, T., Maruya, T. and Takewaka, K., (2015). "A study on the method of measuring the chloride threshold value of corrosion and on the estimation of the values."

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