能登産の安山岩砕石のアルカリシリカ反応性とコンクリート橋脚の膨張性状のモニタリング

A large number of bridge piers in Japan, which were mostly constructed in the 1970s or 1980s, are suffering from serious damages caused by alkali-silica reaction (ASR). The concrete using reactive andesite successively expanded for more than 30years, leading to the serious damage of structural elements of bridge pier. In the case study of Kashima Bridge in Ishikawa Prefecture, the degree of deterioration of bridge pier due to ASR was investigated by both visual inspection of cracking and non-destructive testing. Furthermore, the mechanical properties of concrete and the degree of fracture of steel bars were examined for the purpose of strengthening design of bridge pier. Based on the classification of ASR deterioration level of each element, the steel plate bonding was adopted for the column, after the pillow beam had been totally reconstructed. This paper describes the mineralogical properties of reactive andesite used in concrete and the mechanical properties of concrete cores taken from bridge pier. Furthermore, monitoring and strengthening methods applied for Kashima Bridge pier are introduced together with non-destructive testing by means of ultrasonic wave inspection. In the maintenance of this bridge, a monitoring using crack sensors has been successfully applied in order to ensure the daily safety of bridge. ©2008 The Society of Materials Science, Japan.