Segregation in asphalt pavements is one of the most common and costly problems in the paving industry. This paper deals with the thermal segregation of hot mix asphalt (HMA) pavement.
HMA is produced and placed at high temperatures (e.g. 155 – 163°C and 140 – 155°C, respectively) and is therefore subject to thermal segregation due to differential cooling, which typically occurs during transport of HMA material and construction of pavement. If the temperature of the asphalt material is not consistent, pavement will eventually show signs of temperature differential damage (TDD ) in the locations of the cold spots. Construction–related temperature differentials are large material temperature differences resulting from placement of a significantly cooler portion of HMA material into the new pavement. Placement of this cooler material can create areas near or below cessation temperature (commonly taken as 80°C) which tend to resist adequate compaction. These isolated cooler areas do not fulfil asphalt layer density requirements.
The objective of this study was to utilize an infrared camera to identify thermal segregation in asphalt pavements during construction and possible causes of the temperature differentials which affect compaction and lead to premature distress of the pavement. Temperature data was obtained using an infrared camera (thermal sensitivity 60 mK, geometric resolution 640x480 pixels, FOV 24°) at the paving site. Infrared camera was able to clearly discern cool areas of uncompacted and compacted asphalt material, as well as to determine the temperatures of loose mix in trucks and pavers.

thermal segregation, temperature differentials, pavement distress, cessation temperature, infrared camera