This project developed a method based on the technique of active heating infrared thermography for detecting delamination and deterioration in bridge decks. The method involves briefly heating the deck with high-intensity pavement heaters, and then detecting the temperature differentials at delaminations using infrared thermography. Analytical studies employing a thermal/mechanical model showed that detectable differentials can be produced using the output of a standard pavement heater with 5-10 seconds of heating application. Laboratory studies on slabs with simulated delaminations incorporated at different locations and depths with 10-second heating confirmed detectable temperature differentials at the delaminated locations (Figure 1).
A cost analysis estimate shows that for a standard overpass bridge, the infrared method is less than half the cost of the conventional chain dragging method and occupies the structure for one tenth of the time. For a four-lane bridge, 180 ft long and with a surface area of about 8600 sq. ft., the chain drag method cost over $7200, required 42 hours of field technician’s time and 21 hours of lane closure. The infrared heating method cost about $3600, requiring only 4 hours of the technician’s time and 2 hours of moving lane closure. Further field testing and demonstration is needed to implement this technology for highway application. The final report is available from the National Technical Information Service (NTIS # PB2005-100681).