劣化予測/維持管理(1)

[V-573] Corrosion of reinforcing steel by sea sand in reinforced concrete manholes for communication and its application to maintenance.

〇Hisatoshi Kasahara¹, Yosuke Takeuchi¹, Yosuke Okamura¹ (1.Nippon Telegraph and Telephone Corporation)

Keywords:Communication manhole, Maintenance, Sea sand, Corrosion limit chloride ion concentration

NTT owns about 580,000 reinforced concrete communication manholes (MH). For some MH, there is a report of the existence of salt due to the use of sea sand as aggregate at the time of construction, and corrosion and cracking of reinforcing steel caused by this. In this study, we investigated the chloride concentration and other factors for MH, and sought a method to determine which MH has the internal salt derived from sea sand that causes corrosion using the obtained data. As a result, we found a method to discriminate the use of sea sand to some extent by calculating the longest period of crack generation using the chloride ion concentration at the limit of corrosion occurrence.