Applying the multilayer level set approach to explore the thermal surface characteristics of hot mix asphalt

• The regional boundaries of hot mix asphalt can be identified and located.
• The convergence speed of employing the multilayer level set approach is fast.
• The cool-down phenomena during HMA pavement installation can be monitored.

The surface temperature of hot mix asphalt (HMA) in the field is an important indicator of whether it is under the appropriate conditions for installation and satisfies the installation specifications. Traditionally, field engineers examine the temperature of HMA by employing a metal thermometer, penetrating the HMA at random locations to measure the temperature. However, a non-contact thermal infrared camera effectively provides a reasonable correlation between the surface temperature readings and the internal mat temperature. In this paper, an image segmentation method is proposed and employed to analyze collected thermal images of HMA in order to extract the surface temperature information without contacting the HMA. Based on the minimization of energy, the multilayer level set approach implicitly presents the regional boundaries as several nested level lines. The segmented results can be used to extract the temperature information in order to establish the relationships between the recorded temperature and time. These relationships can be utilized to monitor the cool-down phenomena of HMA to control the quality of HMA installation.