Improving monitoring robustness with embedded AE sensors for damage detection in deteriorated reinforced concrete

Abstract

The acoustic emission (AE) technique has proven successful in detecting various AE sources in reinforced concrete (RC), ranging from crack growth due to mechanical loading to corrosion of the steel reinforcement. Most research, however, has focused on small specimens in laboratory conditions, with monitoring durations rarely exceeding several weeks. Upscaling to long-term monitoring on actual structures remains a challenge. Major concerns in AE sensor deployment on real RC structures are establishing a durable sensor-to-surface coupling over long periods, the high attenuation of AE waves over larger distances, sensor placement in difficult-to-access areas, and the protection of the highly sensitive sensors against environmental factors. Embedded sensors in the bulk material, so‑called ‘smart aggregates', have been proposed as a promising solution to these issues, as they are permanently bonded within the material, match the impedance, and can be placed closer to the emission sources in case of reinforcement corrosion, while being protected by the surrounding concrete. In an effort to improve robustness of AE set-ups for long-term field application, current work assesses the added value of embedded sensors in combination with surface-mounted sensors in two experiments: (1) during rebar corrosion tests in RC prisms and (2) during mechanical loading of a full-scale RC girder.