Civil Engineering Association

Top-Down Cracking of Hot-Mix Asphalt Layers: Models for Initiation and Propagation

The research focused on: 1) Finalizing the two primary model components [i.e., a viscoelastic continuum damage (VECD) model for crack initiation and a hot mix asphalt fracture mechanics (HMA-FM) model for crack propagation], involving development and integration of sub-models that are relevant to dominant top-down cracking mechanisms into each model component; 2) Verifying the reasonableness of the two enhanced primary model components (i.e., the VECD-based model and the HMA-FM-based model); and 3) Developing for and integrating with the HMA-FM-based crack propagation model a simplified fracture energy-based crack initiation model to illustrate the potential of a completed system and to help formulate a plan for integrating, calibrating, and validating the two enhanced primary model components. In summary, the work performed clearly indicates that the VECD-based model and the HMA-FM-based model developed and evaluated in this project can form the basis for a top-down cracking model suitable for use in the Mechanistic-Empirical Pavement Design Guide (MEPDG). Furthermore, the component models can form the basis for an improved performance model to predict multiple cracking distresses simultaneously, including top-down cracking, bottom-up cracking, and thermal cracking. The project also identified and recommended research efforts to develop calibrated/validated top-down cracking performance models for use in the MEPDG.