Characteristics of acoustic emissions generated during the electrochemical corrosion process of steel reinforcement in reinforced concrete beams

Abstract

This article reports the characteristics of acoustic emissions (AE) generated during the electrochemical corrosion process in reinforced concrete (RC) beam specimens. The RC beam specimens have been subjected to electrochemical corrosion in a NaCl solution container that has been present in the laboratory. The gaussian mixture modeling (GMM) algorithm has been employed to classify the AE generated during both the corrosion of steel rebar and the fracturing of concrete. A sudden increase in the generation of AE signals has been observed with the initiation of steel-rebar corrosion in the RC beam. The AE hits recorded during the initial stages have exhibited short durations of less than approximately 0.5 milliseconds. However, as corrosion has progressed, both the signal strength and the duration of the AE waveforms have increased. The extended monitoring duration has also affected the position of the knee in the cumulative AE signal strength (CSS) curve. The transition from micro-cracks to macro-cracks has been identified through the AE waveform parameter ‘duration’, which, in the later stages of accelerated corrosion, has ranged between 20 to 40 ms. The study reported in this article has been related to very accelerated corrosion, compared to an in-situ case where corrosion is much slower and likely environmental sources have dominated the total AE released. However, the findings of the present study may prove valuable for long-term monitoring of the corrosion process in RC structures.