Cement/epoxy-based embedded ultrasonic transducers for concrete structure applications

Abstract

Embedded ultrasonic technology has the potential for a wide range of applications in structural health monitoring. In this study, embedded ultrasonic transducers were prepared with cement powder/epoxy resin composites as the matrix of each structural layer. It was found that the incorporation of cement powder has a toughening effect on epoxy resin, which results in the composite material having stronger deformability and higher strength. The packaging layer material was also used for the matching layer, which effectively simplified the transducer fabrication process; the acoustic impedance of the matching layer was close to the acoustic impedance of hardened cement. When the thickness of the backing layer was 5 mm, the transducer had the best sensitivity or resolution. After shielding, the transducer embedded in concrete was effectively protected against external noise and interference. The application of the transducer for monitoring the early hydration and hardening process of concrete showed that the acquired ultrasonic signal had high stability, repeatability, and recognizability. Embedding the transducer in concrete did not decrease the bearing capacity of concrete. The developed transducer can be used as a “smart aggregate” for large-scale, networked, and low-cost active ultrasonic monitoring of concrete buildings.