Non-destructive inspection of corroded steel bars in concrete structures

This paper describes to develop an Ultrasonic Testing method to grasp condition of a round steel bar in concrete and to judge the occurrence of corrosion. Numerical simulation reveals phase of the reflected UT wave from a corroded rebar is reversed from that of the healthy one. Experiments are performed to visualize steel bars in concrete with a signal processing method of Parasitic Discrete Wavelet Transform (P-DWT) filter then, Kirchhoff based Linearized Inverse Scattering Method (K-LISM) reconstructs the image. Akaike Information Criterion (AIC) is effective to select a suitable Base Mother Wavelet (BMW) in the P-DWT process. The P-DWT filter made from a healthy rebar waveform can differentiate the healthy rebar and corroded one, the difference of signal intensity of them is over 32%.