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

Abstract

This article reports on the characteristics of acoustic emissions (AE) generated during the electrochemical corrosion process in reinforced concrete (RC) beam specimens. The RC beam specimens were subjected to electrochemical corrosion in a NaCl solution container present in the laboratory. The Gaussian mixture modeling (GMM) algorithm was used to classify the AE generated during the corrosion of steel rebar and fracture process in concrete. A sudden increase in the generation of AE signals with the initiation of steel-rebar corrosion in the RC beam was observed. The AE hits recorded during the initial stages have a short duration and less than approximately 0.5 ms. However, with the progression of corrosion, there was an increase in the signal strength and duration of the AE waveform. The increase in monitoring time also influenced the knee in the cumulative AE signal strength (CSS) curve. The transition from micro-cracks to macro cracks was identified from the AE waveform parameter, ‘duration’ recorded in the later stages of accelerated corrosion, which was 20 to 40 ms. The study reported in this article is related to accelerated corrosion, compared to an in-situ case where corrosion is much slower and likely environmental sources will dominate the total AE released. However, the present study may be useful for long-term studies on the monitoring of the corrosion process in RC structures.