Abstract
In the mountainous area of the Hokuriku region, bridges are suffering early deterioration caused by salt damage, alkali-silica reaction (ASR) and frost damage. Under such a regional situation, the load carrying capacity evaluation of these bridges has become an urgent issue. In this study, a statistical method–survival analysis–was carried out by using inspection data for bridges in the Hokuriku region, and the relationship between degradation tendency of bridges and regional characteristics causing salt damage, ASR and frost damage has been studied. In addition, the degradation causes of the reinforced concrete deck of a road bridge which deteriorated early in the mountainous area of the Hokuriku region were investigated. Cylindrical core extraction was carried out to analyze the degradation causes. Polarizing microscopic observation of specimens collected from RC slabs confirmed that cracks developed from the andesite particles and cracks were confirmed to be filled with ASR gels. Therefore, ASR was a cause of the deterioration. Moreover, the degradation in the mechanical properties of concrete due to ASR was also studied and reported. The results show that the reduction in compressive strength and static elastic modulus of both dry and leakage-water parts affected the load bearing capacity of the structure.
Highlights
While the aging of local bridges is progressing, bridge maintenance and management expenses decrease in the fiscal situation of reduction in tax revenue due to the declining birth-rate in Japan
The survival time analysis was conducted for reinforced concrete slabs of steel road bridges in the mountainous area constructed for the dam construction in the 1970s
Cracks propagated from andesite particles to cement paste and the alkali-silica reaction (ASR) gel was filled in those cracks
Summary
While the aging of local bridges is progressing, bridge maintenance and management expenses decrease in the fiscal situation of reduction in tax revenue due to the declining birth-rate in Japan. In the Hokuriku region, salt damage, alkali-silica reaction (ASR), and frost damage caused severe degradation early in bridges in the mountainous area without warning [1]. Under such a regional situation, how to evaluate the load bearing capacity of these bridges has become an urgent issue. The relationship between degradation tendency of bridges and regional characteristics causing salt damage, ASR and frost damage was a problem that needs to be solved. Few studies evaluate the current status of RC slabs in the mountainous area of the Hokuriku district where ASR occurred. The current status of the test bridge was evaluated by the change in the mechanical properties, the observation results of ASR gel under the polarized microscope, and the salt content analysis
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