Acoustic emission monitoring for corrosion damage detection and classification

Corrosion of steel reinforcement is a major deterioration mechanism in reinforced concrete structures that has led to highway bridge failures in the recent past. While prestressed and posttensioned concrete structures offer natural protection to the reinforcement by limiting crack development, the high stresses in prestressing strands and their geometry facilitate crevice corrosion that accelerates corrosion deterioration and may increase the risk of sudden failure. Traditional methods for corrosion detection, such as visual inspection and electrochemical measurements, are local, time-consuming, and may not be feasible in posttensioned concrete structures. This chapter summarizes recent efforts that utilize the acoustic emission technique for corrosion detection in passively reinforced, prestressed, and posttensioned concrete structures. Acoustic emission is sensitive to ongoing damage and can detect at both the micro and the macro level. The method is nonintrusive and can enable global assessment of the structural condition. The methodology is reviewed, and the results of accelerated corrosion experiments on specimens with different sizes and configurations are reported. In these studies, acoustic emission results are validated using electrochemical results and micrographs from scanning electron microscopy. A newly developed acoustic emission–based corrosion classification chart is also presented.