Minnesota's weather — extreme summer heat and brutal winter cold — can do a number on asphalt roads, causing stiff and brittle surfaces to crack and break apart.
Minnetonka-based Cargill and Hennepin County are teaming up on project that may keep roads smoother longer. They are repaving a 1-mile segment of Excelsior Boulevard in Hopkins with recycled asphalt injected with bio-based additives produced by the agriculture giant that are designed to create pavement that will withstand the state's punishing conditions.
This week, crews began putting down traditional asphalt mix, largely composed of stone, sand, gravel and asphalt cement, on the eastbound lanes of Excelsior between 11th Avenue and Church Lane.
In the westbound lanes, crews will strip off the current layer of asphalt, inject it with a rejuvenator additive composed of renewable vegetable sources and modified vegetable oils and immediately reuse it. In this case, 125 tons of asphalt normally destined for the scrap yard will be put right back on the road, said Susan Listberger, a Cargill product manager.
The rejuvenator helps restore old asphalt to near its original properties and creates pavement that is long lasting and less susceptible to cracking or rutting, said Hassan Tabatabaee, a senior scientist at Cargill Industrial Specialties.
"It brings a highly durable performance," he said.
Cargill has tried its recycled asphalt mix in parking lots of commercial customers for a few years, but this is the first time it will be applied on a city street in Minnesota, Listberger said.
The state Department of Transportation had been looking for innovative projects to test rejuvenators with a goal of creating longer-lasting pavement, Listberger said. MnDOT talked with Cargill, and the two took their ideas to Hennepin County. Excelsior Boulevard, which is under county jurisdiction, runs directly in front of Cargill's campus at Hwy. 169. And it happened to be on Hennepin County's list of 2018 roads that needed repair, she said.
"It's was really a happy accident that it is next to one of our campuses," Listberger said.
The United States has more than 2.7 million miles of paved roads, and 94 percent of those are surfaced with asphalt, according to the National Asphalt Pavement Association. On average, asphalt surfaces can last 20 to 30 years.
But as blacktop ages and is exposed to sunlight, air, wide swings in temperatures and high traffic volumes, the asphalt cement, or adhesive agent, loses its binding properties. The rejuvenator helps keep it together longer, said Colin Cox, a spokesman with the Hennepin County Transportation Department.
When the Excelsior Boulevard section is complete, the county will have a test zone to monitor the long-term impacts of a standard asphalt mix against Cargill's mix with a renewable, bio-based additive.
"We will be looking at how well it keeps a smooth surface and if cracks in the base layer show through," Cox said. "And we'll see how long it lasts."
If deemed successful, Cox said the county would not have to make repairs as frequently and could try it on other roads in the future.
Tim Harlow • 612-673-7768
