Haruki OGAWA

Collection of Comprehensive Data on the External and Internal Condition of Actual Structure and Elucidation of the Chloride Deterioration Process

Fuminori NAKAMURA

In order to elucidate the salt-induced deterioration process of an actual structure, it is important to understand the surface, interior, and exterior values of the structure and to know the relationships among them. However, although many studies have been conducted on actual structures subjected to salt damage, there are no examples of comprehensive investigations of surface and interior deterioration information from the outside on the same bridge. In this study, comprehensive data on exterior damage, steel corrosion, penetrating salinity, and attained salinity were collected for an actual structure that had been in service for about 50 years in a severe salt-affected environment.
The exterior damage was concentrated on the seaward side of the lower flange, with significant steel corrosion and chloride ion penetration at the same location. However, little corrosion of the PC steel was observed, and corrosion of the axial rebar was particularly significant. In terms of the distribution of deterioration across the entire bridge girder, the girders located on the mountain side from the center of the girder tended to deteriorate significantly in all cases. The results of the verification experiment of the salinity reaching each part of the bridge girder showed the same tendency as that of the deterioration distribution found from the investigation.
In conclusion, the comprehensive data from the exterior to the interior confirmed that there is a relationship between the salt-induced deterioration processes in the actual structures. On the other hand, corrosion of the PC steel itself was hardly observed, and the damage that appeared on the exterior was found to be caused by corrosion of the axial reinforcement bars placed on the outside. Furthermore, in the subject bridges, the deterioration progressed at the girders located on the mountain side from the center of the bridge girders, where the flying salts act more frequently.