Mechanistic modeling of permanent deformation in asphalt mixes with the effect of aggregate characteristics
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Aggregate characteristics play a major role in the resistance of hot mix asphalt (HMA) to permanent deformation. Aggregate texture and angularity influence the frictional properties of the aggregate structure. In addition, the aggregate's non-spherical shape dictates the level of inherent anisotropy that develops due to the preferred orientation of aggregate particles under compaction forces. The majority of previous studies on the influence of aggregate characteristics have focused on relating the mechanical response of HMA, measured using laboratory tests, to aggregate physical characteristics. A different approach is adopted in this study in which a mechanistic elasto-visco-plastic model is developed and implemented in finite element (FE) formulation to predict permanent deformation of HMA. The model's parameters are then related to aggregate shape characteristics. The main advantage of this approach is marked by its ability to identify aggregate characteristics that are required in order to optimize the mixture's resistance to permanent deformation. The efficacy of the model is demonstrated by analyzing the permanent deformation response of three mixes that include aggregates with distinct characteristics. Aggregate characteristics are measured using the Aggregate Imaging System (AIMS). The model's parameters are obtained from compressive and extension triaxial tests conducted at different confining pressures and strain rates. Finite element analyses of pavement sections with these three mixes are conducted under uniform and non-uniform tire pressure distributions. The relationships among the model's parameters, FE simulations of permanent deformation, and aggregate characteristics clearly illustrate the advantages of using the approach presented in this study to directly link aggregate characteristics to asphalt pavement performance.