Thermal Segregation: Causes and Effects on In-Place Density and Fatigue Performance of Asphalt Mixtures
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Previous research has demonstrated that an excessive loss of mix temperature during hauling and paving operations can cause significant reductions in the mix consistency and therefore, in its ability to be compacted appropriately. This construction-related problem has been called thermal segregation. Twenty-eight asphalt paving projects were evaluated in the state of Alabama. Thermal profiles of the mat prior to its compaction were obtained by using the MOBA Pave-IR infrared bar. Based on the results, it was found that remixing operations were a key factor in the reduction of high temperature differentials. Field cores were taken from each ALDOT Division in order to evaluate the effect of thermal segregation on in-place densities. The results indicated a negative effect of thermal segregation on mat in-place densities. Additionally, samples were collected in order to compare the laboratory fatigue performance between cold and hot spots in terms of fatigue cycles, initial stiffness and fracture energy. Based on the results of this study, the mix initial stiffness was determined to be the unique parameter affected by excessive air voids leading to the conclusion that cold spots can be more susceptible to fatigue cracking than hot spots.