Multi-scaled properties of asphalt binders extracted from weathered asphalt mixtures

The objective of this study was to examine the relationship between the multi-scaled mechanical properties of an unmodified asphalt binder and a styrene–butadiene-styrene (SBS) modified asphalt binder, both of which were recovered from weathered open-graded friction course mixtures using an Abson method. The aging of asphalt binders in asphalt pavements was simulated in the lab using an accelerated weathering machine, which produces more authentic results than conventional techniques. The samples were then subjected to Atomic Force Microscopy to investigate their nano-properties. Three indices commonly used for measuring nano-adhesion, were determined for each sample. The results revealed that the roughness of the nano-adhesion increased with the degree of weathering, a clear demonstration of how asphalt surfaces stiffen with age. The behaviours of the three phases (para, peri and catana) shown in the nano-adhesion images of the weathered binders changed as the degree of weathering increased. The para phase expanded size and became more widely dispersed across the domains, eventually becoming the dominant phase by annexing the peri phase as the weathering process proceeded. There was a linear relationship between the nano-adhesion indices and the macroscopic rheological properties. The presence of the SBS modifier consistently affected the areas and shapes of all three phases.