Deterioration of concrete bridge elements due to the effects of corrosion presents a significant challenge for the maintenance and management of highway bridges. The corrosion of reinforcing steel in the concrete leads to the development of delaminations that eventually manifest as spalls in the concrete. Infrared thermography has the potential to detect subsurface delamination before spalling develops, and could be used as an effective tool to enhance the visual inspection of bridges. The technology has traditionally been applied to bridge decks, which are exposed to radiant heating from the sun that helps develop thermal gradients in the concrete. These thermal gradients are required for detection of delaminations, which modify the heat transfer in the concrete such that the delaminations develop greater temperatures at the surface than areas of concrete that are intact. However, thermal gradients can also be developed from the normal diurnal temperature variations that occur. This paper will discuss results of a study to develop thermal imaging for detection of subsurface deterioration in the soffit areas of bridges, which are not exposed to radiant heating from the sun. Experimental studies and field testing were conducted are discussed. The ability to image deterioration on the soffit areas of the bridge is significant to ensuring highway safety, as this deterioration has the potential to result in concrete falling into traffic below overpass bridges. This paper also references guidelines developed for application of the technology in the field.
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