WASHINGTON—Blends of ground tire rubber with trans-isoprene or polybutadiene in a 3:1 ratio in asphalt offer the best storage performance of rubber-modified asphalt blends, according to a paper published in the American Chemical Society publication Energy & Fuels.
"Ground Tire Rubber Modification for Improved Asphalt Storage Stability" is the title of the paper written by Iowa State University researchers Brittany L. Hallmark-Haack, Nacu B. Hernandez, R. Christopher Williams and Eric W. Cochran, according to an ACS news release.
"Currently, about half of U.S. states use ground tire rubber as a component of asphalt mixes, citing better performance than regular asphalt, cost-effectiveness and environmental benefits," the release said. "However, the material has two major challenges that limit wider use: its high viscosity and tendency to separate into rubber and bitumen layers during storage."
The researchers studied the stability of rubberized asphalt made by blending and extruding different amounts of the polymers cis-isoprene, trans-isoprene, polybutadiene and polyisobutylene with ground tire rubber, the ACS said.
They discovered the 3:1 blend of ground tire rubber with trans-isoprene or polybutadiene reduced the density of ground tire rubber so that it was similar to asphalt and did not settle during storage, according to the press release. The polymers also helped reduce the viscosity of the rubberized asphalt, making it easier to work with.
"According to the researchers, the polymer additives are cost-effective, resulting in savings of about 7 to 10 percent compared with regular asphalt," the ACS said.