Evaluation of Rheological and Failure-Based Recycling Agent Optimization Methods

Abstract

This study examined rheological and failure-based approaches for the optimization of two bio-based and two petroleum-based recycling agents (RAs). The results showed that optimizing the RAs based on the performance grade (PG) approach did not fully achieve the rheological and failure characteristics of the target asphalt binder. This was observed for both a bio-based and a petroleum-based RA. The asphalt binder quality test (ABQT) and Glover–Rowe (G-R) approaches showed potential as surrogate methods for estimating the optimum dosage of RAs, whereas the double-edge notched tension (DENT) approach provided a more cost-effective dosage. This needs to be further evaluated through future mixture-level testing and in situ experiments. The selected dosage of each RA, based on the high-end PG, was then applied to a mixture containing 40% reclaimed asphalt pavement (RAP) to achieve the target performance, which was a mixture with 20% RAP. The mixture characteristics were evaluated using the Hamburg wheel tracking test (HWTT) for rutting and moisture damage characterization and the indirect tensile asphalt cracking test (IDEAL-CT) for cracking characterization. The results showed that the addition of RAs improved the cracking resistance of the 40% RAP mixtures without significantly affecting their rutting resistance. The RAs used in this study did not negatively affect the moisture damage resistance of the mixtures. After long-term aging conditions, all mixtures exhibited diminished cracking resistance. The comparison between the aging protocols highlights varied performance among these mixtures, underscoring the necessity for further research in the selection of appropriate aging protocols. Overall, the results revealed that bio-oil-based RAs compare favorably with petroleum-based ones.