Delamination is a common defect that affects the durability and performance of reinforced concrete structures. Major causes of delamination in concrete are rebar corrosion, moisture ingression, damage due to reversal of loading etc. Impact echo is a relatively simple non-destructive method that works based on propagation of stress waves at the impact point of specimen surface to other locations. The recorded signals represented as a waveform in voltage and its corresponding fast Fourier transform in amplitude spectrum essentially carries qualitative and quantitative information about the flaw. This paper investigates the ability of impact echo to image and quantify predefined flaws of different acoustic impedance and estimate their physical dimensions. Impact response were recorded for six apertures intersecting the defect locations at a fine interval of 10 mm. The echogram or B-scan images of signal waveform showed the relative acoustic impedance of the flaws based on the intensity of wave reverberations exhibited during the scans. Furthermore, B-scan images of the fast Fourier transform provided the quantification of the flaws viz. dimensions or depth. Steel rebars could not be detected in any of the B-scan images. The findings reported in this study can be implemented in qualitative and quantitative investigation of delamination in concrete structures.
- Impact echo
- Acoustic impedance