UDOT

The long-lasting asphalt HiMod blend will reduce time, costs, and repairs

The Utah Department of Transportation (UDOT) has developed a weather-resistant, durable asphalt mix that is transforming the way Utah is repaving roads and reducing paving costs, time, and repairs.

In asphalt mixes, crushed rock is mixed with binders that act as a glue. UDOT’s new asphalt blend, called HiMod high density asphalt, uses a significantly higher ratio of polymer in the asphalt binder than traditional asphalt mixes. The thicker, stickier result is much stronger than previously possible, meaning less wear and tear on the roads.

“At UDOT we’re always looking at ways to extend the life of our roads and save taxpayer money,” said Howard Anderson, the UDOT asphalt engineer who headed the development team. “Changing something as simple as the materials used in our asphalt mix can have a tremendous impact, with fewer potholes and longer-lasting roads.”

UDOT tested the new HiMod asphalt blend on I-80 in Wendover at the Port of Entry on the border of Utah and Nevada in June 2021. The test site was selected for its extremities: temperatures regularly reach the triple digits in the summer and the single digits in the winter, and the port of entry experiences heavy truck traffic regularly decelerating and accelerating, adding to pavement distress.

In the past, the area has required regular pavement maintenance. Over three years after laying down the HiMod mix, the test site is still holding strong.

“This new mixture defies everything I studied about asphalt in school,” Anderson said. “But what I was taught in school was based on binders of the past, before we had polymers. With stronger glue, it didn’t make sense to keep doing the same things we’ve always done with asphalt. I wanted to do something better.”

In addition to being durable, UDOT’s blend cuts the paving process in half. With traditional asphalt mixes, crews often lay down the pavement in two thin layers, called “lifts.” This allows them to roll the pavement evenly throughout, compacting the asphalt and removing air pockets to make it more durable. This two-layer application means that crews must place one layer down, compact it, wait for it to set, test it, and add an adhesive coating before repeating the process with another layer.

UDOT’s HiMod high density mix allows crews to do up to a single, six-inch lift without compromising compaction. Samples from the test site showed even compaction throughout, with much higher compaction rates than traditional asphalt mixes. This translates to stronger, more durable roads, with half the labor.

Anderson is not done testing his team’s mix. He wants to analyze it in even thicker lifts, as high as eight inches, and believes that that may be the key to creating “perpetual pavement.” And he isn’t limiting his plans to highways.

“This mix sets up faster than concrete and is more durable than traditional asphalt, and we can use it on sidewalks, trails, you name it,” Anderson said. “Asphalt has stayed in its lane, so to speak, for decades, but it’s time for us to step it up and move beyond that. This mix opens so many opportunities for the asphalt industry as a whole.”

UDOT is using this new asphalt on several construction projects this summer, including the I-80 ramps near the Salt Lake City International Airport, on I-80 going up Parleys Canyon, and repaving the I-215 eastbound off ramp to State Street. Other state departments of transportation have reached out to UDOT about adopting the mix, and UDOT officials expect to see it spread past Utah’s borders over the next few years.