Quantitative AE techniques standardized for concrete structures

Acoustic emission (AE) techniques have been extensively applied to concrete structures. Up-dated results are currently standardized to inspect and evaluate the structures in service. Consequently, test results based on these standards are reviewed and discussed. In order to assess the damage levels of the structures, the recommended practice is proposed by the Japanese Society for Non-Destructive Inspection. Two AE parameters of load ratio and calm ratio are defined for qualification of the damages. It is reported that damages qualified are in good agreement with actual damages of reinforced concrete members under bending. AE behavior of concrete under compression could be analyzed, applying the rate process analysis. By quantifying intact Young's moduli of concrete from the database, relative damages of concrete in existing structures are successfully estimated. The committee on nondestructive inspection of steel-reinforced concrete structures in the Federation of Construction Materials Industries, Japan, has recently published new standards on estimation of concrete properties by elastic-wave methods. One of them is a monitoring method for active cracks in concrete by AE, which is applied to study corrosion cracking in concrete. Moment tensor analysis of AE can identify cracking kinematics of location, crack-type and crack orientation, which is implemented as SiGMA procedure. Nucleation of micro-cracking due to corrosion is identified. It is found that the mechanisms iof corrosion cracking in concrete are nearly equally of mode I, mixed-mode and mode II.