Evaluation of Plus Grades of Performance Grade (PC) Asphalt Binder

This research documented current knowledge and practice related to evaluation of plus grades of performance graded (PG) asphalt binder, with a focus on the scenarios of interest to NMDOT. The synthesis in the final report mainly includes a discussion of the following issues: history of polymer modified binders (PMBs) for asphalt pavement, selection of polymer for asphalt modification, evaluation of PMB properties, binder specifications for PMBs, cost analysis, recommendations, and future work. Recent years have seen the introduction of PG Plus Binders, the success of which hinges on the use of elastomer and/or rubber for binder modification. The primary recommendation for NMDOT is to apply elastomer modification right now while optimizing the formulation and adopt MSCR into the binder specification and implement plus grades of PG asphalt binder, in light of very small cost increase (less than 5%) and significant performance improvements (over 20% life extension) in plus-grade asphalt pavement.

The objective of this project is to evaluate best practices for the use of Plus Grades of Performance Graded (PG) Asphalt Binders and the effect of these binders on long-term performance.

WTI researched information and guidance for a comprehensive report to summarize the current knowledge and best practices to determine correlations between Performance Grade Plus asphalt binders and the long-term performance of pavement properties, such as creep compliance, ductility, and viscoelastic properties.  The study evaluated modified binders to determine if there is any benefit to requiring their use in HMA/WMA mixes and to develop a specification draft for their use.  The approach consisted of 1) a literature review to study and identify state Departments of Transportation that have been active in developing specifications for using modified asphalt binders, and 2) an in-depth investigation to correlate lab tests and properties with long-term performance of polymer modified binders.