By Kathleen Berger, Executive Producer for Science and Technology
As miles of roads and bridges continue to age, the Missouri Department of Transportation is looking for innovative ways to solve the problem of crumbing highways. This is a problem in every state. Another problem is an environmental one. Each year in the United States, millions of tons of plastic waste are discarded and not recycled.
Both problems inspired the work being done in a University of Missouri laboratory. Mizzou Engineers are collaborating with MoDOT and Dow, a materials science company, to develop a new, sustainable asphalt pavement mixture using recycled plastic waste.
“Waste plastic recycling into asphalt has been done internationally, but it hasn’t made its way into any great extent into the US market until recent years,” said Bill Buttlar, the Glen Barton Chair in Flexible Pavements in the Department of Civil and Environmental Engineering.
Buttlar and his team of engineers and student are investigating ways to use various types of single-use, polyethylene-based plastic waste for asphalt, including drinking bottles, grocery bags and drinking straws.
The Mizzou Asphalt Pavement and Innovation Lab developed the new mixture that’s now being tested along a nearly two-mile stretch of the highly traveled Stadium Boulevard in Columbia. This is the first demonstration site in the state of Missouri for waste plastic recycling.
Buttlar said the new recycled overlay asphalt mixture is high performance and will wear down slower than the regular mixtures previously applied to the road surface.
“There was some kind of strange looking cracks on Stadium Boulevard that went off on different angles,” Buttlar explained. “We expect that to be greatly mitigated.”
The test sections will also include a control section, using the MoDOT’s regular pavement. And there’s a third section for testing. It’s a pavement mixture that uses a chemically modified, recycled ground scrap tire rubber. That mixture is expected to extend road life, reduce road construction costs, and could prevent the disposal of millions of scrap tires.
“These are high energy products,” Buttlar said. “It’s a real shame to put tires in the landfill. It’s a real shame to put plastic in a landfill. You could burn both of those for energy. But in the modern circular economy, we’re wondering what’s the best use of recycled materials and we think putting them under the tire on the road is a really great use.”
The plastic and tire rubber materials are expected to extend pavement life by increasing both its strength and toughness. For study results, the team will observe the test area for at least one year, including one summer and one winter season. Buttlar said the new pavement overlay should last for at least a decade, possibly 12 to 15 years.