Knife River – Central Texas completes Warm Mix Asphalt paving project

In mid-May, Knife River – Central Texas Division completed an asphalt paving pilot project using a new technology called Warm Mix Asphalt.

Warm Mix Asphalt is made about 100 degrees cooler than traditional Hot Mix Asphalt through the addition of emulsion and chemical additives. It has been used in Europe for about seven years, but has had limited application in the United States during the past three year.

Because it is such a new technology, Knife River Corporation used the project as a training tool. Nearly a dozen members from Knife River's operating companies took part in a day-long training and product demonstration in which Knife River – Central Texas placed 400 tons of Warm Mix on a residential street in Bryan, Texas.

"I see Warm Mix as the future of asphalt technology," said Bill Thomas, vice president – operations, Knife River – Central Texas. "We wanted to be on the forefront of this product so we can learn as much about it as possible. This pilot project allowed us to increase our knowledge in an environment where we weren't bidding a job, not really knowing how this product worked and what all is involved with it."

There are a number of reasons why Warm Mix Asphalt might be the wave of the future – a majority of them are because of its environmental qualities.

"Warm Mix is produced at a lower temperature – up to 100 degrees less than traditional Hot Mix," said Valerie Miller, asphalt supply manager of Jebro Incorporated, "and because of that there are a number of benefits. The biggest may be reduced fuel costs because the material is not being heated as much as well as lower emissions and fumes. In addition, it provides greater compaction, longer haul distances and increases the amount of RAP (recycled asphalt pavement) that can be added into the mix."

Early results show that Warm Mix Asphalt is very comparable to Hot Mix and in some applications may be able to out perform it. However, more research is needed to determine how the product will stand up long-term and can it be made at a comparable cost to traditional Hot Mix.

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