Instances of reinforcing steel fracture in concrete structures damaged by the alkali-silica reaction (ASR) have been discovered recently in Japan. As long as reinforcing steels are not broken due to ASR-caused expansion, the safety of a structure is considered not to be seriously compromised. However, the safety of a structure becomes questionable when the confinement of concrete becomes degraded due to the fracture of reinforcing steel bars. Therefore, it is important to clarify the mechanism of the fracture of reinforcing steel bars and develop methods for detecting steel bar fractures and strengthening concrete structures damaged by ASR. This paper describes the fracture of reinforcing steels in the case of concrete structures damaged by ASR in the Kansai area in Japan. It then introduces the results of investigation on the fracture mechanism, nondestructive testing methods, and repair and strengthening methods for damaged concrete structures.

Flexural and shear behavior of reinforced concrete beams damaged by alkali-silica reaction (ASR) was investigated under monotonous and reversed cyclic loads, mainly focused on the shear resistant mechanism after flexural yielding. In case under the monotonous loads, shear capacity of the beams damaged by ASR was rather increased by

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In order to establish a safety evaluation technique for ASR-deteriorated structures, crack observation, observation of ASR expansion such as reinforcing bar strain and concrete strain, and loading tests were conducted on RC beam specimens with ASR deterioration to evaluate the effects of ASR deterioration on the RC beam members. In addition, Xray computed tomography (CT) images of core concrete taken from these RC beam specimens were taken to evaluate the cracking conditions in the ASR concrete. The test results showed that the ASR cracks in the specimens without shear reinforcement opened further under loading and cracks were generated, leading to shear failure. In addition, many fine cracks parallel to the loaded cracks were observed in the cores taken from the ASR specimens.