Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/85927
HighwayContractor WARM I County Road F gets an 'A' t can get warm in Wisconsin in June. This past June, Calumet County became ready to lay the surface course of as- phalt on a 4.7-mile stretch of County Road F in Wisconsin. The county hired Northeast Asphalt of Greenville, Wis. Says Craig Van Beek, project man- ager for Northeast Asphalt: "We would pave part of the project with warm mix and the remainder with hot mix," says Van Beek. "The county was excited about the idea, so we proceeded. The total overall tonnage on the project was 9,320 tons, and of that, we used a warm-mix additive for 2,320 tons. It worked out well." Last year, the county hired Northeast Asphalt to pulverize the existing asphalt pavement on County Road F and mix it into the subgrade. The county reshaped the road, and Northeast Asphalt laid down a binder course of asphalt. For the project, the contractor used a 400-ton-per-hour Gencor parallel- fl ow plant located about 20 miles from the paver. It took the trucks about a half-hour to make the trip one-way. The mix design called for Superpave 12.5 mm with 5.15 per- cent of PG 58-28 asphalt cement. The warm-mix additive was Akzo-Nobel Rediset LQ-1106, added at the rate of 0.5 percent of the liquid binder. Northeast Asphalt added 15 percent recycled-asphalt pavement to the mix. The average production rate of hot mix or warm mix was 320 tons per hour, says Van Beek. Hot mix was produced at 305 degrees F, and warm mix was produced at 275 degrees F. Working 15 feet wide, a Blaw- Knox PF-3200 paver equipped with a Carlson Easy IV screed placed the asphalt. The contractor used a Blaw- Knox contact ski on the centerline and a contact-on-mat reference ski. The breakdown roller was a Sakai Notice the absence of blue smoke with warm mix. SW-800 roller working 66 inches wide and making three passes. The average warm mix temperature at the breakdown roller ran about 30 degrees cooler than the hot mix temperature – 245 de- grees F vs. 275 degrees F, respectively. A 54-inch-wide Bomag BW 138AD roller handled fi nish rolling work. The fi nish roller made fi ve passes, and warm mix tem- perature there averaged 130 degrees F compared to 135 degrees F for the hot mix. Northeast Asphalt released an offi cial report of results on the project and reported several advan- tages for warm mix using the Akzo Nobel Rediset additive: • The average burner fuel savings reached 10 to 12 percent, operat- ing at an average of 275 degrees F. • The asphalt cement mixture is workable with the additive and RAP incorporated into the asphalt cement mixture. • The asphalt could be compacted at lower temperatures • The additive offers the potential to extend haul distances beyond what is possible with hot mix. "There were no clear disadvantages found in regards to using the Akzo- Nobel Rediset LQ-1106 warm-mix additive," the report states. "Warm mix widens the tempera- ture window at which you can com- pact the asphalt," says Van Beek. "The asphalt is more workable, and easy to construct. We changed up our roll- ing pattern somewhat with the warm mix. With warm mix we backed off the breakdown roller because the temperatures were quite a bit lower. Then on the hot mix we worked up closer to the paver. "We experimented with putting a rubber-tired roller between the hot roller and the cold roller," says Van Beek. "But then we found that we actually got a better ride by putting the rubber tired roller behind the cold roller." Van Beek reported an absence of smoke and fumes with warm mix. Better Roads August 2012 15