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Thermal imaging can be used to image subsurface damage resulting from the corrosion of embedded reinforcing steel, which typically manifests as delaminations at or near the level of the reinforcing steel. Delaminations interrupt the heat transfer through the concrete, resulting in surface temperature variations that can be assessed using thermal cameras. This type of damage occurs in bridge decks, soffits, parapets, abutments and other concrete bridge components. This paper will discuss advances in the application of thermal imaging for the condition assessment of concrete bridge components, focusing on applications to the areas of the bridge not exposed to the radiant heating of the sun. Research results describing ambient temperature variations and inspection timing requirements for conducting thermal inspections are presented. Research exploring the effects of environmental parameters on the ability to image subsurface defects (delaminations) at different depths in concrete is also discussed.