Parametric analysis and field validations of oxidative ageing in asphalt pavements using multiphysics modelling approaches

Oxidative ageing in field asphalt pavements is a complex process with coupled multiple physics. This parametric study uses Multiphysics modelling approaches to evaluate the effects of material thermal properties, air voids content and distribution, mastic coating thickness, oxygen accessibility and binder oxidative kinetics on the spatial and temporal evolution of the oxidative ageing in the asphalt pavements. Results suggest that increasing the thermal conductivity of asphalt layers leads to a lower ageing gradient. The variations of base and subgrade layers’ thermal properties cause little to no effects on the oxidative ageing. A high activation energy of the asphalt binder (e.g. by adding anti-ageing additives) reduces the oxidative ageing significantly. Asphalt layers built on unbound granular base will experience greater overall ageing with a C-shaped ageing gradient compared to that built on treated base. Air voids content of <5% yields limited oxidative ageing. Five to nine percent air voids generate a gradually increased oxidative ageing with an obvious gradient across pavement depth. Air voids content beyond 9% leads to a consistently high oxidative ageing due to a full access to the oxygen. Finally, the findings were validated using available literature results and field data from 14 European road sections.