Asphalt has two main components: rocks and glue, called the “binder.” Now, the Utah Department of Transportation said it has a better binder: HiMod.
“Not only is it a better glue, but we're using more of that better glue,” UDOT asphalt engineer Howard Anderson said. “We can compact to higher densities that are much stronger and keep the water out.”
That’s important in a state like Utah, which has extreme freeze-thaw cycles, when temperatures melt and refreeze water on the same day.
Freeze-thaw cycles create interesting geology in places like Bryce Canyon, where park rangers report them upwards of 200 days per year. On the road, they create potholes.
Water gets into cracks, freezes, expands, melts and then the surface collapses. And nobody wants to feel like they’re driving on hoodoos.
The pothole-resistant mix was laid locally at the bottom of Parleys Canyon this summer. Motorists can tell if the asphalt has the HiMod binder by its deep black color and because it’s smoother than the rest of the interstate.
Anderson said HiMod has passed all of UDOT’s skid tests, and it was piloted at the port of entry in Wendover, Utah, where there’s big swings in temperature and even bigger traffic.
“We have all the trucks coming in from the California ports,” Anderson said, “And Lonnie Marchant, our Region Two engineer, put it there, and he said, ‘If it works here, it'll work anywhere.’”
He learned about HiMod binders in Federal Transit Administration meetings a decade ago, but UDOT’s binder suppliers were the first to get the chemistry right.
“Even while suppliers back East were struggling with it, the folks out here in the West figured it out,” Anderson said.
To Reed Ryan, executive director of the national trade organization Asphalt Pavement Alliance, it’s a watershed moment in watertight paving.
“Howard and the great folks at UDOT, some of the regional engineers, like Lonnie Marchant and others, our binder suppliers in the state of Utah—they have taken about 40, 50 years of traditional mix design, and really kind of turned it on its head,” Ryan said.
The state expects to save on maintenance and pothole repair down the road. And it is already seeing savings now. Anderson said HiMod isn’t as affordable as UDOT’s budget pavement option but it is less expensive—and performs better—than its previous top-of-the-line asphalt.
And because it’s denser, UDOT can pave one layer rather than two, expediting road work.
DOTs from Montana, Colorado, Idaho and Arizona have reached out to learn about the new formula. And because HiMod was developed using federal dollars, Anderson said UDOT is eager to share.
