Location of a defect in a concrete block by a non-destructive technique.

Abstract

This paper describes a method to estimate the position of a crack in a concrete block using several vibration pick-ups. An array of vibration pick-ups is attached on the concrete block, and a vibration pulse is forced by using a small hammer. If there is a crack, a reflection wave is generated from the position of the crack. Therefore, conventional methods to estimate the position of vibration source seems to be useful for this purpose. However, since the concrete block is elastic, there are three wave propagation modes; the surface wave mode, the primary wave mode and the secondary wave mode. Since the necessary primary wave mode is not significant in magnitude, we cannot estimate the position by the conventional methods. To increase the S/N, we had already proposed a method to eliminate the first-coming surface wave. However, the method was insufficient to achieve a higher S/N. Therefore, this paper proposes a new method to achieve a better location of a crack. Some experiments were carried out, and good results were obtained.