Successive Estimation Technique in Microwave Tomography for Concrete Diagnosis

Abstract

Techniques for concrete diagnosis are needed in construction industry because degradation could occur unseen in concrete. Microwave tomography is one of hopeful techniques for concrete diagnosis. Because usually a target of concrete diagnosis cannot be separated from the concrete structure and taken into a radio wave darkroom for measuring, the time of observing wave scattering has to be limited to eliminate the influence of obstacles outside the computational domain in getting tomography. As a result, a part of the concrete target in the computational domain is un-reconstructable. However, in a concrete diagnosis, the reconstructable zone cannot be recognized in advance, because the velocity of wave propagating through the concrete body is unknown. It is one of the key problems of microwave tomography in concrete diagnosis. This paper proposes a “Successive Estimation Technique” to solve the problem. Successive estimation technique is an iteration method to reconstruct the target part by part, by using “time-divided” information of scattering waves. It is suitable for microwave tomography in concrete diagnosis because the reconstructable and un-reconstructable zones can be distinguished automatically, and good reconstructed images are obtained efficiently, even in a noise contamination case.