Automated Acoustic Scanning System for Delamination Detection in Concrete Bridge Decks

In this study, an automated acoustic scanning system was developed for rapid delamination detection on concrete bridge decks. A new ball-chain impact source was designed by combining the advantages of chain-drag (rapid testing speed) and impact-echo tests (analysis in the frequency domain). Conventional steel link chains and the new ball chains were investigated as acoustic excitation sources. Acoustic signals were processed by short-time Fourier transform (STFT) in the frequency range 0.5-5 kHz. Compared with the conventional chain-drag test, the ball-chain results show better signal-to-noise ratio (S/N), higher sensitivity, and repeatability to delamination identification. The automated scanning system includes excitation sources (ball chains), acoustic sensors (microphones), a geographic positioning system (GPS), data acquisition (oscilloscope), and a signal-processing algorithm. Acoustic scanning results are integrated with positioning data to generate an image of the scanned area in a map view. The system was validated in the field on a concrete bridge deck and was found to show satisfactory accuracy, efficiency, and repeatability.