ABSTRACT
In the case of Tokyo metropolitan subway tunnels located near tidal rivers and coastal areas, the deterioration of reinforced concrete due to chloride attacks by leakage water include chloride ions is progressing at a rapid rate. In order to prevent the deterioration of chloride attack in subway tunnels, we have standardized judgement method for repair areas by spraying silver nitrate solution and repair method for using sacrificial anode material and surface impregnation material. In addition, we applied a surface impregnation material that inhibit chloride ion penetration to concrete when chloride attack is detected even if no concrete deformation can be confirmed as preventive maintenance. Tokyo metro conducted chloride attack countermeasure repairing in operating subways since 2014, and have already carried out it over 6,551m. In some of the repaired sections, monitoring has been continuously carried out by visual inspection, chipping survey and measurements of protective current discharge rate and depolarization. As a result, we confirmed these repair works are effective by checking the entire repaired section after more than seven years had passed since repair, with no problematic deformations occurring.
