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The crews paved the Lehman-Roberts’ office parking lot and the land surrounding the asphalt plant.

In an effort to obtain quantifiable test results, a Tennessee Type E surface mix with virgin aggregate and a PG 64-22 binder was selected. This same mix was successfully used in the fall of 2007 at the Memphis International Airport. In its hot mix form, the Type E asphalt is typically produced at temperatures ranging from 300 to 310 degrees F.

The warm mix asphalt experiments of this mix began at 300-degree F mix temperatures, which were methodically lowered throughout the evaluation. According to Nelson, Lehman-Roberts was “shooting for 270 degrees F,” and this target, as well as lower temperatures, was achieved.

Paving conditions were less than ideal. Ambient temperatures ranged from 34 to 37 degrees F, and the subbase was slightly wet. However, the mix went down well for the paving crews. “I was amazed at how long the mix remained workable for shoveling and luting,” says Nelson.

He also noticed that the only visible steam was coming from the drums of the double drum vibratory roller, not from the silo, truck or paver. The breakdown roller immediately compacted the asphalt mat - laid in a 2-inch-thick lift - behind the paver. The roller initially operated in static mode and the operator gradually added vibration to the pattern. A second double drum compactor provided the finish rolling.