A Time-Domain Method for Ultrasound Concrete Health Monitoring Using In Situ Piezoelectric Transducers.

In this article, a smart time-domain technique is presented for detecting flaws in concrete structures using embedded piezoelectric transducers. The method relies on the time-of-flight of ultrasound (US) waves generated and sensed by piezoelectric transducers which are embedded in a concrete structure before pouring the concrete. A damage index is introduced to quantify the likelihood of defects in the region between the two probes. The index is comprised of a normalization function that is independent of the strength of the captured signal and not sensitive with respect to the amount of coupling between the embedded sensors and the structure. A sliding mode extremum-seeking (SMES) method is utilized for real time calculation of the damage index. The proposed health monitoring system was verified by experimental results. Comparisons are performed when using a conventional approach by a grid search method to demonstrate performance improvement of the proposed system.