Acoustic emission source characterisation of chloride-induced corrosion damage in reinforced concrete

Worldwide, asset managers are struggling with the management of ageing infrastructure in reinforced concrete. Early detection of reinforcement corrosion, which is generally considered as the major problem, can help to perform dedicated maintenance and repair. The acoustic emission technique is promising to reach this goal. However, research on the characterisation of the different damage sources during corrosion in reinforced concrete remains scarce. In this article, the characterisation of damage processes is investigated on small reinforced concrete prisms and upscaled to reinforced concrete beams under accelerated conditions in a laboratory environment. Damage sources are assigned based on careful validation with crack width measurements and dummy samples. Signals originating from different acoustic emission sources are compared in the time and frequency domain. Moreover, the continuous wavelet transform is applied to provide information on time-frequency characteristics. The results show that the moment of concrete macro-cracking can be derived from a sudden increase of the cumulative acoustic emission events and cumulative acoustic emission energy. However, validation with crack measurements is required. The shift in both peak and centre frequency of the acoustic emission signals is found to be a better indicator. Wavelet transform allows to distinguish acoustic emission sources when frequency ranges are overlapping. Possible acoustic emission sources such as the corrosion process and concrete cover cracking, are successfully assigned. The major contributions of this article are the characterisation of acoustic emission sources from corrosion damage in reinforced concrete, validation with crack measurements and dummy samples, as well as a dedicated wavelet analysis.