Acoustic testing of concrete bridge decks for detection of delamination

Impact Echo (IE), Ultrasonic (US) Echo (two measurement systems: a single probe and a linear array system) were used to detect shallow and deep delaminations in a concrete specimen. The test specimen is a section of a deteriorated bridge deck preserved from the demolition of a 45-year old prestressed box girder bridge in Berlin, Germany. The IE and US (single probe) data collection was done automatically utilizing a scanner system, while the testing with US linear array system was conducted manually. A number of cores were extracted to provide ground-truth information and the basis to assess the effectiveness of each test method in detecting and characterizing delaminations. In this study, IE yielded an overall satisfactory assessment however, individual spectra at single measurement points were often difficult to interpret. US (single probe) could detect deep delaminations but not the shallow ones. The shallow delaminations could be only indirectly suspected, where the back-wall reflections were weakened or vanished. US Linear Array could detect the location and extent of deep delimitations and provided indications of shallow ones.