Experimental and Analytical Study on the Influence of Joints and Surface Coating on Macro-cell Corrosion of Reinforcement in Concrete

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As the summery of this study, following concluding remarks were clarified :(1) Oxygen permeability of concrete decreases as the water-cement ratio (W/C) becomes small or the the humidity of the environment becomes large and that the resistance of concerete decreases as the humidity becomes large.(2) The corrosion rate of macro-cell and micro-cell becomes lower as the water-cement ratio (W/C) of concrete becomes low, and the quality of repair materials is very influensive on the mechanisms of macro-cell corrosion.(3) The corrosion rate is largest when the relative humidity is around 80% at which the concrete can be well supplied with oxygen and water. This is because the corrosion rate is depend on oxygen permeability when the humidity is high and by the resistance of concrete when the humidity is low.(4) From the experimental study of macro-cell corrosion mechanisms, it is considered that macro-cell corrosion occures in the old concretenear the joint when the difference of chloride content between old and repair materials is large.(5) The macro-cell corrosion rate which is formed by the difference of chloride content is influenced by the quality of concrete.(6) From the experimental and analytical study about prevention of macro-cell corrosion by coating, it can be said that the macro-cell corrosion rate is very low when chloride contentof old concrete before coating is low.