Characterisation and modelling of vapour-conditioned asphalt binders using nanoindentation

Nanoindentation tests were conducted on unconditioned and vapour-conditioned asphalt binder samples to determine damage processes by characterising contact creep data and using viscoelastic mechanical models. For vapour-conditioned asphalt binders, a thin film of asphalt binder was prepared on a glass slide and subjected to relative humidity (RH) of 25%, 49% and 71% inside enclosed desiccators using three aqueous solutions: potassium acetate, potassium carbonate and sodium chloride, respectively. Based on the nanoindentation contact creep test data, it was observed that vapour-conditioned asphalt binders showed larger indentation viscous depth than the unconditioned binders. Indentation test data were modelled using viscoelastic mechanical models such as Burgers and Maxwell models. The models showed that elasticity increased and viscosity decreased in the vapour-conditioned asphalt binders. In 71% RH-conditioned binders, elastic components of Burgers model, E-1 and E-2 increased about 10% and 15%, respectively, compared to the unconditioned binder. The relaxation time decreased about 35% and retardation time increased about 69% in 71% RH-conditioned binders compared to unconditioned binders.