Thermal Imaging of Hot-Mix Asphalt Paving Projects in Connecticut

Abstract

Results of a study on thermal segregation of hot-mix asphalt (HMA) during pavement construction are presented. The significance of thermal segregation to pavement performance should not be overvalued, because it is not only possible but probable that other factors play more significant roles. For example, the idea is presented that density achieved is more dependent on HMA temperature (T) than temperature differentials (ΔT). It is surmised that thermal segregation has a negligible effect until cold-area temperatures drop below certain threshold values. This reasoning is based on results of a 5-year pavement condition survey that demonstrated little, if any, relationship between temperature differentials located with an infrared camera during HMA construction and subsequent damage to a pavement's surface. Although 5 years may be too short a period for some distresses to develop, extensive reflective cracking was observed at some locations; this demonstrates reflective cracking played a more prominent role than ΔT. Comparisons of asphalt contents and grain-size distributions between cold areas and their surrounding normal-temperature pavements demonstrated no significant differences, suggesting that temperature differentials in HMA during construction are not necessarily indicative of particle segregation. Finally, definitions for the terminology associated with HMA construction and infrared thermography are presented.