Rebar corrosion has been studied using the impact echo method [1]. Alternatively, the bonding situation was examined using low-frequency ultrasound [2]. Due to the severe attenuation of elastic waves in concrete, it was necessary to drive the piezoelectric transducer at a voltage higher than 500 volts. Current study demonstrated the feasibility of detecting the coating condition of rebar using B scans. Preliminary results showed clear connection existed between acceptable coating and signal attenuation. Further investigation using tone burst signals generated by a high-power gated amplifier was proposed. REFERENCES

1. M-T. Liang and P-J. Su, "Detection of rebar corrosion in concrete using impact echo method", Proceedings of the Eighth Asia-Pacific Conference on Nondestructive Testing, Taipei, December 11-14, 1995
2. C-H. Chiang and C-L. Tsai, "The elastic wave propagation at the interface between coated steel rebar and concrete", Ultrasonics (paper in progress).