Raj Dongre

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.

A study was conducted on epoxy-modified asphalt (EMA) diluted with two binders of a different chemical structure, to understand the effect of curing rates and long-term postcuring characteristics. Dynamic shear rheometer test results did not show a clear trend of curing time and dosage percentage impact for the two base binders; parallel-plate geometry may not be well-suited to study EMA because of the thermosetting properties of curing. The asphalt binder test (ABT) method was used to assess the effect on rheology of short-term and long-term curing. Analysis of the ABT data to date suggests that the binder source has a notable effect on the composite properties. The impact of long-term storage was also found to be dependent on the asphalt binder used. Findings from this study were also applied to two field binders; one was modified using styrene-butadiene-styrene polymer, and the other contained epoxy. Curing times were determined using the ABT test. The Dongre Workability Test (DWT) was also conducted on open-graded friction course mixes and the mix curing times were found to be significantly higher than those determined on the binders. A method based on DWT data to determine a “workability window” was also explored. The Strategic Highway Research Program (SHRP) sol-type binder AAG-2 was found to exhibit little to no reactivity with the epoxy modifier used in this study. The SHRP gel-type binder AAD-2, however, was found to be highly reactive. The short-term curing temperature was found to affect the rate of curing for base binder AAD-2. The curing rate was found to be highest at 165°C followed by 120°C, and the rate was at its slowest at 25°C. AAG-2 did not show any onset of curing at either temperature.