Iowa Department of Transportation
Iowa Highway Research Board
Chris Williamsrwilliam@iastate.edu email >
Eric Cochranecochran@iastate.edu email >
About the research
Iowa State University (ISU) has assembled a team of experts in Civil, Chemical, and Industrial and Manufacturing Systems Engineering to address the challenges of integrating scrap and end-of-life rubbers to supplant the use of up to 140,000 tons/year of virgin polymer used in asphalt pavements. The team proposes the use off-specification polybutadiene to modify ground tire rubber (GTR) particles, from recycled tires, and use them as an asphalt modifier to replace widely used SBS elastomers. GTR is currently being used as a modifier, which offers comparable improvements with respect to SBS polymers such as rutting resistance and elastic recovery, with advantages such as improved traction and reduced noise. However, because of the difference in density with asphalt it suffers from inadequate storage stability, rendering it an unpreferred material in asphalt modification. ISU has developed a technology that density matches GTR with asphalt with simple compounding techniques, producing a GTR product that meets storage stability specifications and would be accepted by the market. If 100% of virgin polymer were replaced with recycled GTR, up to 140,000 tons/year could be reclaimed nationwide. Moreover, asphalt pavements are 100% recyclable, including as a major component of new roadways, which means that GTR used in pavements will continue to be reused.