A fundamental study on polarimetric gb-sar for non-destructive inspection of internal damages of concrete walls

Damages on the surfaces of concrete buildings can easily be detected by visual inspection and can be repaired. However, damages inside walls need non-destructive inspection techniques to be detected, located, and identified. There has been a great demand for such techniques particularly after the 3.11 Great East Japan Earthquake. Ground-based synthetic aperture radar (GB-SAR) is a technique that can potentially inspect concrete walls in a non-destructive and non-contacting manner. The paper reports a fundamental experiment with a polarimetric GB-SAR system to detect internal damages of a concrete specimen, which was caused by horizontal loading simulating earthquakes. The results shows that the system does not have enough resolution to visualize individual defects, and the effect of steel rebars installed inside the concrete is so strong that masks week responses. However, polarimetric analysis showed the capability to minimize the effect of rebars by re-arranging polarization basis and to extract week responses. In particular, internal damages could be detected by observing volume scattering component in this experiment.