Flaw detection in concrete using wheel-shape transducers

A method for flaw detection in concrete using wheel-shape transducers has been described. Wheel-shape transducers take advantage of better handling and better fitting with rough surfaces. The Bi-cross-section technique, however, has the problem that it receives Rayleigh waves. Furthermore, attenuation of concrete forces operation at low frequency, which makes flaw detection coarser in resolution and complicates the technology. Experimental equipment has been designed to move two transducers independently, in which some signal processing methods such as synthetic aperture would be available. We have developed “extending aperture” to reduce Rayleigh waves and migration to measure the velocity of bulk waves and to construct the tomography. Good results have been obtained in an experiment of the testing block in which the thickness changes locally. Cracks in the lower concrete layer in a double layered road have been detected