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Monitoring potential of air-coupled ultrasonic testing for concrete damage and repair

par Lefever, Gerlinde;Jamshaid, Laiba;Snoeck, Didier ;Aggelis, Dimitrios G.
Référence Journal of Building Engineering, 114, page (114487)
Publication Publié, 2025-11-15

Article révisé par les pairs

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Résumé :

Ultrasound has emerged as a promising technique for the evaluation of concrete quality. However, coupled ultrasonic transducers are often utilized, which need physical contact with the element under study. This process may inhibit errors related to manual coupling and does not allow automation. A solution to this is the adoption of air-coupled ultrasound. Nonetheless, the full characterization potential of the air-coupled technique for repair characterization of concrete has yet to be demonstrated. This is mainly due to low signal-to-noise ratio as well as limited frequency bandwidth. In the present study, an “optical microphone” with flat response is utilized to evaluate concrete damage and repair in an air-coupled manner and for a relatively broad band of frequencies. Different repair cases, i.e. the manual application and the injection of polyurethane, were studied using through-the-thickness ultrasonic measurements. The results show that the air-coupled receiver has great potential for structural applications, exhibiting similar results to coupled resonant sensors, while allowing for the possibility of fast scanning. Moreover, the polyurethane showed a restoration of the ultrasonic parameters towards the intact state. Lastly, the calculation of the phase velocity vs. frequency curve allowed to select the most sensitive frequency for damage and repair assessment.