Effect of recycling agents in recycled asphalt binders observed with microstructural and rheological tests

- Performance of rejuvenated binders was investigated by AFM and DSR.
- AFM provided indications about molecular mobility and degree of association.
- Surface roughness, phase contrast and dispersed domain appearance were considered.
- Improved flow properties due to recycling agents were observed with DSR and AFM.
- Aging of rejuvenated blends caused lower molecular mobility and higher brittleness.

In this study, the effect of recycling agents on recycled blends obtained from base and recycled asphalt binders and the performance of the rejuvenated binders with aging was investigated by means of Atomic Force Microscopy (AFM) and Dynamic Shear Rheometer (DSR). This study arises as the amount of recycled materials in asphalt pavements continues to increase. Recycled binders are significantly stiffer than base binders; however, the performance grade can be restored by inclusion of recycling agents. Nevertheless, intermediate temperature cracking performance evaluated by the Glover-Rowe (G-R) parameter indicated that the effect of the recycling agents is not sustained with subsequent aging, which could jeopardize its effectiveness in service. The AFM images provided microstructural information, which offer indications about changes in molecular mobility and degree of association with aging, presence of agglomerations, and the dispersive effect of recycling agents.