材齢約30年の7つのドルフィンの鉄筋コンクリート調査に基づく腐食発生限界塩化物イオン濃度に関する考察

抄録

This paper aims to discuss the chloride threshold value for the initiation of steel corrosion and the influence of chloride content at the rebar on corrosion progress in marine RC structures. The site investigation of reinforced concrete of seven existing dolphins was conducted in order to examine the influence of cover thickness and chloride content at the rebar on chloride induced corrosion. These dolphins were constructed in Tokyo bay and have been in service for around 30 years. In addition, the laboratory test was carried out by using reinforced concrete specimens with various chloride content and cover thickness in order to prove the results obtained from the site investigation. As the results, the chloride threshold value for the initiation of steel corrosion has been ranged within 2.0 and 2.4kg/m³. Moreover the speed of corrosion progress of rebars has been increased rapidly when chloride content at the rebar exceeded around 4.0kg/m³. Also, no serious corrosion of rebars with cover thickness over 70mm has been confirmed in around 30 years old concrete of dolphins.