Phase field approach to damage and fracture in asphalt concrete using multiscale finite element modeling of an instrumented pavement section

This study presents a Multiscale Finite Element Model (MsFEM) and Phase Field Fracture (PFF) based approach to study the responses and damage behavior of the viscoelastic Asphalt Concrete (AC) based on the actual traffic loadings. AC is a multiphase heterogeneous material. Understanding the mechanical responses and damage accumulation in different phases of AC has been a challenge for the pavement research community. This study proposes a methodology to overcome this challenge by combining a two-way linked multiscale finite element model with phase-field fracture. A modified PFF degradation function is formulated to quantify the damage and fracture in the AC microstructure. Combining MsFEM with PFF, it is possible to take the material heterogeneity, anisotropic and viscoelastic damage accumulation in the AC microstructure into consideration to identify the overall performance of the macroscale pavement. The developed MsFEM with PFF is validated based on the responses from an instrumented pavement section under Falling Weight Deflectometer (FWD) test load. Model responses are in agreement with field sensor responses, demonstrating that MsFEM with PFF can be used to accurately and efficiently predict AC microstructure performances. The model is also used to perform parametric studies to determine the extent of damage in the microscale AC due to the movement of Super Heavy Loads (SHLs) which is computationally very expensive in a traditional single scale model. The results from the parametric study show that weaker and thinner unbound layers have the highest potential of initiating fatigue damage in the AC microstructure.