A Study of Thermal Properties and the Heating Process in Asphaltic Concrete.

Abstract

Abstract : The objectives of this study were to model the surface heating of asphaltic concrete pavements and to investigate the thermal properties (conductivity, specific heat, and diffusivity) of asphaltic concrete. The thermal properties of six laboratory prepared asphaltic concrete mixes at three asphalt contents were determined. As a result of testing four or five replicate samples of each of the eighteen mix combinations, it was concluded that average values of specific heat and diffusivity, independent of asphalt content but dependent aggregate gradation and mineralogy, could be used. Conductivity varied with asphalt content as well as aggregate type and gradation. A parameter study using the transient heat transfer model which employed radiant and convection heating of the pavement surface and conduction through the asphaltic concrete indicated that: without exceeding the flash point of asphaltic concrete, it typically takes a field heater 25-35 minutes to heat the pavement at a depth of 25 mm to a temperature sufficient for easy removal (this was verified by field test); combined convection-thermal radiation heating is more efficient that radiant heating, and; the best surface heating strategy is to operate the heater at a temperature such that the pavement reaches its maximum allowable temperature just as the desired temperature is reached at the prescribed removal depth without using insulation periods (soaking) between heat applications.