Resumen de Top-Down Cracking: Enhanced Performance Model and Improved Understanding of Mechanisms
An enhanced model for predicting top-down cracking based on the HMA fracture mechanics (HMA-FM) model developed at the University of Florida (UF) was presented in this study. The enhanced model maintained the fundamental elements of the HMA-FM system, including its associated threshold concept that is suitable for developing rules for both crack initiation and propagation, and its ability to model the presence of macro cracks and their effect on response. Major enhancements included the development and introduction of sub-models that account for aging and healing effects on cracking performance. In addition, a sub-model was developed and introduced into the enhanced model to predict transverse thermal stresses, which are more relevant to top-down cracking than longitudinal thermal stresses. The enhanced performance model was used to better understand cracking mechanisms through an extensive parametric study in which the effect of various factors (including load, temperature, aging and healing) on cracking performance was investigated. It was found that the most important aspect to accurately predict top-down cracking performance is the accurate prediction of changes in mixture fracture, damage and healing properties caused by aging.
Temperature was found to have only a small influence on top-down cracking because its effect on thermally-induced damage and load-induced damage cancel each other within the range of in-service temperature conditions typically encountered in North America. In addition, the study also showed that pavement structure has a strong influence on top-down cracking performance for thinner pavements where the bending mechanism is dominant. However, the pavement structural effect is not critical for thicker pavements where the near-tire mechanism, for which individual tire effects may be more important, takes control.
Key Words: HMA Fracture Mechanics, Aging, Healing, Fracture Energy ____________________________________________________ 1Post Doctoral Associate, Department of Civil and Coastal Engineering, University of Florida, Gainesville, Florida 2Professor, Department of Civil and Coastal Engineering, University of Florida, Gainesville, Florida The oral presentation was made by Dr. Zou
