1. Evaluation of Plus Grades of Performance Graded Asphalt 2016 High Value Research Project New Mexico Department of Transportation PI: Western Transportation Institute Montana State University

2. Abstract Excerpt: WTI conducted research for the New Mexico Department of Transportation (NMDOT) to document current knowledge and practice related to asphalt pavement Research on the issue included history, selection, evaluation, specifications, cost analysis, recommendations, and future work Research Result: “NMDOT is strongly recommended to apply elastomer modification right now while optimizing the formulation in light of very small cost increase (less than 5%) and significant performance improvements (over 20% life extension) in plus-grade asphalt pavement.”

3. What is an “Elastomer”? Elastomer is simply a contraction of the words “elastic polymer” Elastomers act like rubber bands in asphalt, giving it tension reinforcement like steel does in concrete Added to asphalt to make it more stiff at high temps and more crack resistant at low temps An older polymer, a plastic polymer -- or “plastomer” -- does relatively well in laboratory tests but not as well on the road

4. Relative Cost of Asphalt and Polymer Polymers used to cost about fifteen times more than asphalt Rise in asphalt prices significantly changed the economic equation With asphalt prices higher, elastic polymers are now roughly only five times as expensive than asphalt Now it makes economic sense to put more polymer in the asphalt -- it’s less expensive than it used to be, and the more polymer we put in a road the stronger and more durable it is, so the asphalt doesn’t need to be as thick and it lasts longer

5. Increased Technical Understanding Data was limited and values were assigned with antiquated tests and economics as to what temperature range was cost effective for a given location After several decades of research, we have a better understanding of how much polymer should be combined with asphalt, and with warm mix and other additives we don’t have the concerns about workability with higher amounts of polymer that we used to have Example: we know elastic polymer is more effective and less expensive than plastic polymer given a specific location on the road

6. Key Research Results Elastic polymers are less expensive than plastic polymers for a given performance gain – more bang for the buck Data and information from new tests on polymers will allow DOTs to better understand how much we should include in asphalt – and allow them to optimize the combination of saving more money up front by reducing thickness, and in the long run by increasing longevity Substantial spillover benefits related to traffic disruptions, inspection costs, energy use, and economic opportunity