When the top two football teams in the country take the field this weekend in Minneapolis, Koch Industries will literally be with them every step of the way.
That’s because the asphalt that lies underneath the artificial turf at Minnesota’s new U.S. Bank Stadium – home to this year’s big game – came from Flint Hills Resources’ Pine Bend refinery, located in nearby Rosemount, Minnesota. (Flint Hills Resources is a wholly owned subsidiary of Koch.)
“We were the asphalt supplier for the stadium floor back in 2016,” said Charles Boan, marketing manager for Flint Hills Resources’ asphalt division. “Our polymer-modified asphalt was mixed with aggregate to create the hot-mix asphalt used to lay the support foundation for the field. Then it was laid in a process called 3D paving to extremely rigorous specifications over a day or two.”
To meet the necessary surface flatness, the asphalt has no more than a 1/8-inch deviation every 10 feet by 10 feet for the entire surface area of the field.
Covering that much surface area required a lot of hot-mix asphalt - about 8,000 tons in fact, or about 650 filled dump trucks. And making that hot-mix took roughly 375 liquid tons of polymer-modified asphalt supplied straight from Pine Bend.
To create hot-mix asphalt, polymers are added to liquid asphalt in a process called polymerization. Polymerization helps make a product that’s more durable than most roadway asphalts, yet still flexible.
Beyond the foundation of the football field, asphalt is a cornerstone of our American infrastructure. It covers 96 percent of our roadways, and the Flint Hills facility at Pine Bend is one of the largest suppliers of high-quality asphalt, producing more than 10 percent of all U.S. asphalt. But why use it as the base layer for an artificial field? The answer lies in its versatility.
“You have to have a subsurface underneath the turf, because there are going to be monster truck shows and football games and concerts at the stadium,” said Boan. “So you need some type of hard surface underneath that can handle it all. People don’t realize it, but it’s not uncommon for stadium floors to be asphalt.”
If the idea of landing on turf-covered asphalt hurts just thinking about it, bear in mind that modern artificial turf has come a long way from the synthetic grass fields of yesterday.
The type of turf the football pros play on consists of several inches of material, including nylon grass fibers, rubber and sand infill, and a urethane base. So, it’s engineered to help absorb the impact of a 300-pound lineman crashing down on a 220-pound running back.
With an asphalt base underneath it that can take the weight of a monster truck, Minnesota’s field might not just be the biggest stage in the world on Sunday, but also the toughest.