The acoustic emission (AE) technique allows monitoring damage in (reinforced) concrete in a non-destructive way by means of piezoelectric sensors attached to the material surface. This approach has disadvantages such as a decrease of the sensor coupling over time, high attenuation of AE waves in concrete, and difficulties in terms of sensor placement. Embedded AE sensors, so-called ‘smart aggregates’ (SA), can be a valuable addition or alternative to surface-mounted AE sensors. However, the embedment of sensors brings its own challenges. In this paper, the use of SA is investigated to monitor cracking of fiber reinforced concrete during a three-point bending test, and corrosion and related concrete cracking of reinforced concrete during an accelerated corrosion test. The novelty of the paper is the application of SA for passive AE monitoring during concrete degradation processes with a varying cracking behavior and crack orientation. Special emphasis is put on data filtering and localization of AE sources. The results show that, despite a higher level of wide-band noise for the SA sensors, they are able to detect and localize concrete cracking after dedicated filtering. Furthermore, the potential of SA sensors in early-stage detection of corrosion damage is demonstrated, offering enhanced possibilities for predictive maintenance of concrete structures.

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Reinforcement corrosion is the most common and most expensive damage mechanism in existing reinforced concrete (RC) structures. Therefore, the qualitative and sustainable renovation of these structures leads to several important technical challenges. Camilo Torres, a student residence of KU Leuven built in 1968, is an example of a RC building dealing with corrosion problems. Corrosion causes the formation of rust and a reduction of the steel bar’s cross section. The former will eventually cause cracking and spalling of the concrete cover and deterioration of the bond at the reinforcement-concrete interface. An important question that can be asked is to which extent the corrosion process affects the structural capacity of the concrete components and how to deal with this in a renovation process. The focus of this paper is the on-site investigation of the corroded RC components of the Camilo Torres residence to provide input for structural assessment and renovation process. Firstly, the history of the building and used materials are investigated. Secondly, on-site analysis is performed to inventorise global and local damage. Results are compared with findings from previous on-site investigations executed in 2000 and 2014 to examine the damage progress. It was found that the main damage is caused by carbonation-induced corrosion leading to cracking and spalling of the concrete cover. An important part of the rebars have a concrete cover less than 25 mm due to construction errors. Also the presence of honeycombs accelerates the corrosion process. The Acoustic Emission technique is able to detect the damage patterns during tomography and passive acoustic emission sensing, however, more effort is needed to optimise the localisation accuracy.@en