Effect of Asphalt Mortar Viscoelasticity on Microstructural Fracture Behavior of Asphalt Mixture Based on Cohesive Zone Model

Racking in asphalt pavements has always been the leading cause of pavement damage. This study aims at investigating the effects of mesostructure characteristics of asphalt mixture on the fracture behavior of semicircular bending (SCB) samples. To fulfill this objective, a two-dimensional (2D) finite-element model (FEM) of an asphalt mixture considering viscoelastic properties was established by using digital image processing (DIP) technology and a cohesive zone model (CZM). The FEM method was validated based on experimental results. On this basis, the whole process of crack initiation and propagation, the damage distribution of cohesive elements, and the effects of mesostructure characteristics (such as voids, interface strength between aggregate and asphalt mortar, and initial crack length) on damage and fracture behavior of SCB samples were analyzed. It was observed that with increasing porosity, the ultimate bearing capacity of the specimen decreased, and the cracks propagated towards the path with more air voids. The air voids far away from the crack propagation path had minimal effect on the ultimate bearing capacity of the specimen but could induce new damaged cohesive elements. With the decrease of the interface strength of aggregate-asphalt mortar, the maximum bearing capacity of the samples decreased, and the proportion of the cohesive elements with more significant damage at the interface increased accordingly. The resulting bearing capacity, fracture energy, and creep dissipation energy of the specimens reduced gradually with increasing initial crack length.

Automated summary

This study investigates the effects of mesostructure characteristics of asphalt mixture on the fracture behavior of semicircular bending samples. It establishes a two-dimensional finite-element model considering viscoelastic properties and uses digital image processing technology and a cohesive zone model to validate the model. The study examines the crack initiation and propagation process, the damage distribution of cohesive elements, and the effects of mesostructure characteristics on damage and fracture behavior. It finds that increasing porosity leads to a decrease in ultimate bearing capacity and a propagation of cracks towards air voids. Weaker interface strength between aggregate and asphalt mortar decreases maximum bearing capacity and increases damage at the interface. Additionally, increasing initial crack length reduces bearing capacity, fracture energy, and creep dissipation energy.