Use of Infrared Thermography to Detect Thermal Segregation in Asphalt Overlay and Reflective Cracking Potential

The objectives of this study were to assess whether temperature differentials measured using infrared thermography (IRT) occur in an overlay built on top of discontinuities such as joints and cracks and to study the horizontal and vertical thermal profiles in the asphalt overlay using a validated finite element (FE) modeling approach. To achieve this objective, an infrared camera was used to monitor the temperature profiles in the asphalt mat in a number of field projects from the time it was placed to after completion of the compaction process. The temperature profiles were monitored on top and away from severe discontinuities and joints in the existing pavement. Based on IRT measurements, cracks in the existing pavement did not influence the thermal profiles in a hot-mix asphalt overlay. However, thermal measurements on top of a joint were consistently lower than away from it as observed in thermal images, which may indicate that temperature loss may occur at the joints. Based on FE simulations, the model predicted a slightly higher rate of thermal decrease at the bottom of the overlay above the joint than away from it attributable to convection losses at the joint. While this difference may not be large enough to be identified as thermal segregation, it can influence the bulk properties of the overlay at the joints and promote early cracking. Results also show that thermal differences occur in the vertical direction as well as in the horizontal direction in the asphalt mat. (c) 2015 American Society of Civil Engineers.