Automated ultrasonic scattering energy method for evaluation of small-sized cracking damage in concrete

The aim of this study was to develop an automatic ultrasonic scattering energy method (USEM) to evaluate smallscale damage to concrete. The automated system measured Leaky Rayleigh waves from the specimens. Herein, the energy of the scattering portion of waves caused by cracks was extracted using a 2D Fourier transform. USEM has the advantage of detecting cracking damage smaller than the applied ultrasonic wavelength, which is problematic when conventional ultrasonic methods are applied to concrete. The proposed methodology was evaluated using laboratory-scale specimens and a concrete bridge exposed to freeze-thaw cycles in the field. The results of the extracted scattering energy demonstrated that the USEM is sufficiently sensitive to detect and localize subwavelength damages of 0.05 mm in concrete. Furthermore, the proposed USEM was compared with conventional ultrasonic pulse velocity with respect to the accuracy of damage detection.