temperature differential [47]. These cold spots can be seen in Figure 19 where they identified areas of temperature segregation at 212°F (100°C) where the surrounding areas were 285°F (140°C).
Figure 19: Temperature segregation identified with thermal imaging [47]
Temperature segregation has numerous causes but generally it is a result of differential cooling within the asphalt. There are many typical construction activities that can result in temperature differentials [48]: •
Asphalt mix cooling during transport
•
Lack of remixing before paving
•
Night paving with an ambient temperature lower than 70°F
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Haul times of greater than 70 minutes
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Accidental asphalt mix discharge on the base that is later paved over
•
Incidents that lead to paver stoppage Temperature segregation can occur in transport through loss of heat through the truck
sides and insulating cover [46,48,49]. The combination of improper insulation, long haul time, and low ambient temperature can cause significant temperature differences in transport [49]. Generally, any exposure to different environments for portions of the asphalt mix can cause 26