ForConstructionPros.com

As warm mix continues to develop as a viable option for asphalt paving projects, Knife River, an MDU Resources Company, spearheaded three test projects in 2007 to gain a better understanding of the technology and prove to road agency customers that it meets the same performance specifications of hot mix in a more environmentally-friendly manner.

One project in particular, Nebraska Department of Roads' Highway 12 between Verdel and Monowi in Knox County, also demonstrated that a long haul from plant to paver posed no challenge in achieving density compaction.

In early summer of last year, Knife River Midwest and Jebro Inc., another MDU Resources Company which supplies liquid asphalt binder, proposed a research project using the warm mix technology.

The asphalt producer/paving contractor proposed using one of three additives — Evotherm, Evotherm DAT or Sasobit — to produce the warm mix, with the Nebraska DOR finally specifying the Sasol wax brand, which Jebro blended into two different percentages — 1.5 percent and 2.5 percent — for test purposes that would allow Knife River to evaluate the benefits of using an extra 1 percent of the additive.

"We've been interested in exploring warm mix and we thought this would be a good project for our tests. We wanted to evaluate the fuel savings, increased workability, rolling patterns, increased haul distance, emissions (blue smoke), decreased aging of the binder, and the properties of the binder when Sasobit is added," notes Mike Collins, Knife River Midwest AMA Manager.