Towards a mechanistic model for reflective cracking in asphalt concrete overlays

For highway rehabilitation and resurfacing projects, asphalt concrete (AC) overlay is the most common structure type for both old AC pavements and old Portland cement concrete (PCC) pavements. Yet despite the fact that reflective cracking is the dominant failure mode for AC overlays, current design guides either do not account for it or they treat it in a purely empirical manner. A mechanistic model for reflective cracking in AC overlays would not only help develop better design guides, but it would also help identify working solutions for retarding reflective cracking. This paper describes research that takes a two-level approach to reach such a mechanistic model. At the material level, the research identified a constitutive model to describe cracking in AC mixes. At the structural level, the research used Finite Element Method to account for the effects of boundary conditions that define the forces driving crack development in the overlay. The paper first reviews existing models and identifies non-local continuum damage mechanics (CDM) as the most suitable framework for developing constitutive models for cracking in AC mixes. The non-local CDM was then customized to account for the special material behaviors of AC mixes. The paper then discusses the FEM implementation, the model parameter calibration, and field verification of the proposed mechanistic model. The research demonstrates that the implicit gradient non-local CDM.