Localisation and characterisation of corrosion damage in reinforced concrete by means of acoustic emission and X-ray computed tomography

Many existing reinforced concrete (RC) structures are suffering from corrosion damage. The development of reliable tools to characterise and localise such damage is essential to assess the structural capacity. The acoustic emission (AE) technique has proven to be promising for this purpose. However, this technique poses challenges to reliably interpret the results and lacks rigourous validation. In this paper, microfocus X-ray computed tomography (micro-CT) is used to validate the use of AE for the localisation and characterisation of chloride-induced corrosion damage. An experimental protocol is designed, where both techniques are applied on small-scale reinforced mortar samples during accelerated corrosion. In addition to the frequently applied localisation of the AE events, a new signal-based clustering algorithm of the AE events is proposed, which allows to distinguish between different damage processes, such as friction due to the emergence of corrosion products and corrosion-induced mortar cracking. The results obtained from the AE localisation and clustering are confirmed by the micro-CT images and are found to be in line with alternative damage characterisation techniques based on AE parameters, that are found in the literature. Finally, it is shown that the combination of clustered AE events and micro-CT for the considered small-scale samples can help to understand the different damage processes induced by corrosion.