Researchers in Missouri are deploying an additive derived from plastic straws, bags and bottles into a test road in hopes of increasing asphalt pavement life and environmental benefits.
The University of Missouri’s Mizzou Asphalt Pavement and Innovation Lab (MAPIL) is working with funding from Dow Inc. and the Missouri Dept. of Transportation (MoDOT). According to a university press release, asphalt and plastic both come from crude oil; this makes them chemically similar enough to be mixed together. The plastic additive is expected to add three to five years to existing roads, and five years or more when added to new pavement.
The mixture is currently being tested along a nearly two-mile stretch of Stadium Boulevard in Columbia near U.S. Highway 63 that carries an estimated 36,000 daily vehicles. The boulevard will be observed for at least a year, to capture the effects of a summer and a winter. So far no changes have been observed ever since the road was fully paved at the end of summer. MAPIL used more than 15 tons of plastic in four miles of asphalt overlay that was an inch thick. This is the equivalent of 1.26 million water bottles or 2.37 million plastic bags.
Bill Buttlar, who leads the MAPIL team, kept in mind the supply and demand required for a widespread application of the plastic mixture.
“There would be enough waste plastic available to be used in virtually every ton of asphalt in the United States. The missing piece of this puzzle is the recycling infrastructure you’d need in place, but where you have people you need roads, and where you have people you have waste plastic,” he says. “All types of regional recycling plants are out there, but if there were more applications like this one, we’d be able to provide an avenue for the plastic to be used.”
Buttlar explained the process further: “To make the process efficient and affordable, the plastic additive is mixed into the asphalt at the plant level. MAPIL’s additive is fed in a dry plastic similar to the process of injection modeling, and then pneumatically inserted into the asphalt.Only a simple modification to the pneumatic insert process is required for the plastic additive to blend with the asphalt. No changes in paving processes are required for the new asphalt.”
The test sections on Stadium Boulevard will also include a control sectionconsisting of a pavement mixture commonly used and approved by MoDOT, according to the release. An additional test section uses a pavement mixture including a chemically modified, recycled ground scrap tire rubber. The ground tire rubber test is being conducted in collaboration with Asphalt Plus, LLC.
Jennifer Harper, the research director of MoDOT, says, “If we find a way to make this work, we have roads everywhere in this country, so this could be a huge game changer. If done right, this mixture can solve a lot of problems. We see that as we make the mixture going into higher production, this additive can really make a difference.”
by Megan Guttieri