The premature deterioration of concrete bridges is one of the most serious problems currently facing several highway authorities. The detection of subsurface fracture planes, or delaminations, is necessary when prioritizing bridges for repair. Delaminations are commonly detected by manual methods, such as a sounding rod or a chain drag, which are subjective, tedious and require expensive lane closures. Infrared thermography (IRT) is a recognized non-destructive testing and remote sensing technique for evaluating concrete bridge elements, such as bridge decks and piers and has proven to be capable of detecting subsurface anomalies owing to temperature differentials between sound and unsound concrete. In the present study, IRT was employed to inspect a deteriorated concrete bridge located in the province of Quebec, Canada. The survey was conducted on the bridge deck as well as within the bridge soffit, which is critical for traditional inspection methods due to the traffic passing under the bridge. The collected IR images of the bridge deck were enhanced using image processing algorithms to reduce noise and improve thermal contrasts. The images were subsequently stitched to produce a mosaic view of the entire bridge deck using several Matlab codes. The delaminated areas were identified based on thresholding classification and mapped using a commercial mapping software. The results demonstrate that IRT can yield both quantitative and qualitative indications of subsurface delamination defects, thus assisting transportation agencies to identify critical deficiencies and focus limited funding on the most deserving bridge decks. In addition, the ability to inspect difficult access areas can assist in adding this invaluable thermal technique to the bridge inspector’s tool box.
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