Integration of Thermal Fracture in the HMA Fracture Model

Field observations indicate that both traffic and thermal stresses affect top-down cracking performance of flexible pavements. Further evaluation of these observations will require the development and use of cracking models that can consider the effect of temperature. A rigorous analytical model was developed to assess the effect of thermal loading conditions and mixture properties on dissipated creep strain energy (DCSE) and cracking. Accumulation of DCSE in a mixture subjected to thermal stresses is much less straightforward than for load-induced stresses, and performance may be affected by the theological aspects of the mixture other than creep. Appropriate equations were developed to calculate thermal stress development and DCSE accumulation for an asphalt mixture subjected to thermal loading cycles. Calculations performed with the resulting model showed that although top-down cracking performance in Florida was most strongly affected by traffic loading, thermal effects also affected performance. A combined system that incorporates the effect of both load- and temperature-induced damages on top-down cracking was developed and resulted in better correlation between predicted and observed top-down cracking performances.