Multiphysics Simulation and Validation of Field Ageing of Asphalt Pavements

Long-term field ageing of asphalt pavement plays a vital role in limiting the pavements’ service life. Models have been established to represent the multiple physics that contribute to the ageing of asphalt pavement, including: (1) heat transfer to determine pavement temperature profile, (2) diffusion of oxygen from the air into the connected air voids of the asphalt pavement, (3) diffusion of oxygen from the air void channels to the inside of the asphalt mastic coating films, and (4) the growth of oxidation products in the asphalt binders. These four ageing-related physics were mathematically modelled individually in the literature; however, they were not effectively integrated and coupled into a comprehensive computational model. The challenge lies in that the ageing-related physics are circularly dependent and time-dependent. Another challenge results from the complexity in numerical modelling of the high nonlinearity caused by the circular dependency between the four physics. This study uses weak-form partial differential equation (PDE)-based finite element (FE) program to efficiently couple the physics into one integrated model. The model inputs include the available site-specific hourly weather data, binder oxidation kinetics, mixture design properties, and thermal characteristics of pavement materials. The model was validated using the field measurements of the oxidation products (carbonyl) from The Federal Highway Administration (FHWA) reports. Results show that the model can effectively address the circular dependency between the ageing-related multiphysics and reliably predict the oxidation products along pavement depth for asphalt pavement road section.