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Various deterioration and damage in reinforced concrete (RC) have been reported. Since salt is one of deterioration causes of RC, monitoring and diagnosis against deterioration are key issues. Thus, development of non-destructive evaluation (NDE) technique is important to assess corrosion process. To identify the onset of corrosion and the nucleation of corrosion-induced cracking in concrete due to expansion of corrosion products, continuous acoustic emission (AE) monitoring is available. In order to clarify these phenomena, cyclic wet and dry tests are performed in a laboratory. The SiGMA (Simplified Green's functions for Moment tensor Analysis) procedure is applied to AE waveforms to identify source kinematics of micro-crack locations, types and orientations. This study shows that the onset of corrosion and the nucleation of corrosion-induced cracking in concrete are visually identified. Then, cracking mechanisms due to the expansion of corrosion products are quantitatively clarified.

Concrete structures suffer from the corrosion of reinforcing steel-bars due to severe environments, in particular, chloride attack. Acoustic Emission (AE) techniques have been extensively applied to concrete and concrete structures. In order to identify the onset of corrosion and the nucleation of concrete cracking due to expansion of corrosion products, continuous AE monitoring is available. These corrosion-induced cracks in concrete are studies in an accelerated corrosion test, where kinematics of micro-cracks is identified by SiGMA (Simplified Green's functions for Moment tensor Analysis). Monitoring the corrosion process of rebar by AE, it is confirmed that the onset of corrosion and the nucleation of corrosion-induced cracks in concrete are successfully identified. Then, generating mechanisms of corrosion-induced cracks are clarified by the SiGMA analysis.