One of the hottest topics in the asphalt industry today has to do with a cooling trend for mix temperatures. Warm mix asphalt has generated much buzz among associations, government agencies, equipment manufacturers and asphalt producers since being introduced in the United States approximately five years ago.

Advancements made in the technology and positive field test results for warm mix asphalt projects were a primary focus at the January 2008 National Asphalt Pavement Association Conference in Phoenix.

And why not? Many key industry officials have long been promoting the potential benefits for producers using the new mixing processes to lower temperatures by 50 to 75 degrees F.

These probable advantages include: the opportunity to save on fuel costs; burning fewer volatiles at lower temperatures to increase mix quality; the chance to expand the paving season for the northern two-thirds of the country; and lower emissions and no blue smoke offering the promise of being able to make mix in large metropolitan districts previously designated as non-attainment areas.

The greatest benefit of them all, however, may be the fact that warm mix asphalt can be used for virtually any mix design - base, intermediate or surface.

Producers are partnering with industry associations and government agencies to expand field evaluations of a variety of warm mix asphalt technologies available in the market. However, one of the primary road blocks keeping some producers from moving forward with warm mix asphalt is cost.

Some industry estimates put as much as a $4 per-ton premium for some of the additives on the market … not a welcomed expense on the heals of historic price increases for liquid asphalt.

“As a producer, we have avoided warm mix asphalt additives because the higher costs are less desirable for us and our customers,” explains Patrick Nelson, director of information technology and special projects for Lehman-Roberts Company, Memphis, TN.

This is not to say that Lehman-Roberts is not interested in warm mix asphalt. On the contrary, Nelson explains that the company has been following and studying the technology since it was first introduced to the United States.

“We have spoken with several producers who have run warm mixes,” he adds. “We feel there is a spot for it in the Memphis market.”

Seizing the opportunity

Lehman-Roberts’ opportunity to evaluate warm mix asphalt came just before the end of 2007. Company officials were approached by Terex Roadbuilding to test its new foamed asphalt approach. “Foamed asphalt just makes sense, and the nice thing about the Terex system is that it’s easily adapted to our plants and control systems,” Nelson mentions.

Once the decision was made to move forward with a field evaluation, Lehman-Roberts had to select which of the four Terex plants it owns would be retrofitted with the new system.

The warm mix asphalt field kit was installed on a 1992 Cedarapids/Standard Havens (now Terex) Magnum (inside-the-drum) counterflow asphalt plant.

“We were very excited about running the tests, since this was our first time working with warm mix asphalt,” Nelson says. “We wanted to educate ourselves on the foamed asphalt process and see if this would be a viable alternative to additives.”

Testing this new technology mirrors Lehman-Roberts’ progressive business philosophy and strategy. With its roots tracing back to Memphis in 1939, the innovative producer has grown to be a dominant player in western Tennessee and northern Mississippi.

Today, it owns nine asphalt plants to make mix for its county and state projects as well as for its city and private contracting customers. Nelson mentions that Lehman-Roberts is not afraid to take on new technologies to maintain its competitive advantage and build upon its reputation for delivering a quality product.

Proven technology