The Applicability of Infrared Thermography in the Detection of Delamination in Bridge Decks

About the report:

The use of infrared thermography to very accurately define variations in surface temperatures was evaluated as a means of identifying delaminated areas caused by corrosion of reinforcing steel in concrete bridge decks. It was found that because of the vast differences in the volumetric heats of the solid concrete and the air in the cracks around a delaminated area, the separated concrete was warmer when exposed to solar heating than was the adjacent sound material. Differences in the temperatures of the deck surface, shown in various shades or colors on a cathode-ray tube, were photographed to provide a permanent graphic record of the location of the warmer, distressed areas. In a comparative study of infrared thermography and conventional deck evaluation techniques, including the sounding of the surface with a hammer and chain drag and the use of a rolling delamination detector, all methods were found generally satisfactory in locating severe to medium delaminations. However, the infrared thermography procedure had an important advantage in disclosing incipient delaminations, those in which the cracking is confined to the close vicinity of the reinforcing steel. In every case the thermographic technique seemed to provide better detailed records of the delaminated areas, which were confirmed by coring of the concrete. The rationale behind the use of thermography for detecting delaminations, a brief description of the technique, and a discussion of some experimental results are provided.

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