PFI-TT: Storage stable, biopolymer-modified, recycled tire rubber asphalt additives for resilient and sustainable asphalt pavements

The broader impact/commercial potential of this Partnerships for Innovation - Technology Translation (PFI-TT) project is to develop a pelletized biopolymer-modified product suitable for replacing the synthetic rubbers used in polymer modified asphalt pavements. Each year, about 80 million tons of asphalt pavement is constructed in the U. S.

Hight traffic volume requires the resiliency provided by polymer modification. Approximately 400,000,000 pounds of synthetic rubbers are used for this purpose. At the same time, 250,000,000 end-of-life tires are generated each year, rich in both natural and synthetic rubbers.

This project will develop an engineered, recycled tire product that replaces polymers in asphalt, reducing energy consumption and greenhouse gas emissions. This technology will be achieved by solving a long-standing storage stability challenge in tire rubber-modified asphalts by compounding with biopolymers to match the density of the rubber with the asphalt.

The commercial opportunity is estimated to be $0.3 - 1 billion across the construction, automotive, and consumer markets. The project will broaden participation of underrepresented groups and provide valuable practical training in applied research, technology transfer, and entrepreneurship to the students assigned to the project.

The project will develop a pelletized ground tire rubber product engineered to maintain storage stability in molten asphalt under quiescent conditions while enhancing the asphalt binder properties to meet polymer modified asphalt specifications. The primary challenge in state-of-the-art ground tire rubber asphalt modification is the settling of rubber particles over time due to the density mismatch.

The intellectual merit of this project is to generate foundational knowledge connecting thermoset rubbers to their density modification though the use of polymer additives and processing represents. The key innovation of this project is the recognition that both tires and asphalt are heterogeneous materials that contain both polar and non-polar domains.

Accordingly, a ground tire rubber (GTR)-modification framework based upon both polar and non-polar polymer modifiers may enable polymer compounding technology to function with any GTR/asphalt binder combination by adjusting the polymer formulation. Storage stability of prototype modified GTRs will be evaluated in asphalt through both legacy ring-and-ball testing as well as new scanning methods.

This technology will establish the framework of how the polymer additive characteristics impact the GTR properties with respect to their use as asphalt modifiers.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.