Polymer Additives Improve Storage Stability of Asphalt Rubber

Currently, about half of U.S. states use ground tire rubber in asphalt mixes, citing better performance, cost-effectiveness and environmental benefits. However, the rubber asphalt material has two major challenges that limit wider use: its high viscosity and tendency to separate into rubber and bitumen layers during storage. Iowa State University researchers Christopher Williams, Eric Cochran and colleagues wanted to identify polymer additives that might mitigate these problems.

The researchers studied the stability of rubber asphalt made by blending and extruding different amounts of the polymers cis-isoprene, trans-isoprene, polybutadiene or polyisobutylene with ground tire rubber.

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Their findings were recently published by the American Chemical Society in a paper titled “Ground Tire Modification for Improved Storage Stability”.

The research team found that, when mixed with asphalt, blends of ground tire rubber with trans-isoprene or polybutadiene in a 3:1 ratio performed the best. These mixtures reduced the density of ground tire rubber so that it was similar to asphalt and did not settle during storage, the researchers said.

The polymers helped reduce the viscosity of the rubber asphalt making the material easier to work with and they are cost-effective, saving 7 to 10 percent compared with regular asphalt, researchers said.

© Scrap Tire News, March 2019