A combination of PZT and EMAT transducers for interface inspection

A PZT (Lead Zirconate-Titanate) transducer requires a couplant to send and receive mechanical waves. This requirement is a major shortcoming of the PZT technique for use in field applications. In the laboratory environment careful considerations and surface treatments are required to use PZT because the couplant can affect the consistency of experimental results. One alternative to overcome this shortcoming is the use of EMAT (ElectroMagnetic Acoustic Transducer). However, EMAT gives relatively low transmitted ultrasonic energy, with low signal to noise ratio, and the induced energy is critically dependent on the probe proximity to the test object. These are not desirable properties for NDT (nondestructive testing) of civil infrastructures. That is why, in this paper, a combination of PZT and EMAT is introduced for investigating reinforced concrete structures. Interface defects between steel bars and concrete are investigated by this technique. It is shown that the PZT-EMAT combination is very effective for steel bar-concrete interface inspection and the guided waves are useful for nondestructive testing of civil infrastructures.