Hot Mix Asphalt Technology - January/February 2008 - (Page 30)

Warm Mix: The Lights are Green continued working conditions at the paving site. The crew’s first reaction was to say, ‘There’s no smoke!’” At the eastern entrance to the park and the road to Sylvan Pass, the demo used 9,000 metric tons of asphalt on each of three sections – a control section, a Sasobit section, and a section of Advera WMA. Because of the remoteness of the park, the mixes had to be hauled about 90 minutes from a portable plant in Cody, Wyo. Still, paving crews achieved good densities: Advera WMA average—93.9 percent of maximum theoretical density; Sasobit average—93.4 percent; and the control—93.2 percent. “Density was not difficult to achieve, even at much lower mixture temperatures,” said Neitzke. He said it did seem somewhat difficult to maintain lower mix temperatures; production temperatures had a tendency to jump from 250 to 260o F. Tests showed that aggregates were adequately dried, even at the lower temperatures. Moisture contents ran below the maximum of 0.5 percent for both the warm mixes and control mix. The FHWA posted its mobile asphalt testing lab at the Yellowstone demonstration, and ran a full suite of tests including dynamic modulus and flow number, said Matthew Corrigan, an FHWA asphalt paving engineer. Results were not available at this writing. “We want performance from warm mix that is equal to hot mix, and based on the information we have, the performance is there,” said Neitzke. “Warm mix has done well in Europe for 10 years.” Franklin, Tenn. Country music stars living on a section of Hillsboro Pike near Nashville received a demonstration of warm-mix asphalt, courtesy of the Tennessee DOT and LoJac Enterprises. Between 700 and 1,200 tons each of four different warm mixes – using Astec Double Barrel Green System and the additives Sasobit, Evotherm DAT, and Advera WMA – were applied to the road last October. The Astec System employs two banks of nozzles to inject a small quantity of water (approximately 0.1 percent by weight of the total mix) and air on opposite sides of the stream of liquid asphalt as it enters the mixing drum. The water is converted to steam by the heat of the liquid asphalt, and foamed asphalt is created as it is introduced into the outer drum of the asphalt plant. The foam collapses around the aggregate and the water evaporates during the production and construction process. “On non-attainment days, when the air quality is bad, we often get shut down and are unable to pave,” said Brian Egan, assistant director of construction for TDOT. “But with warm mix, because the emissions are reduced, we might be able to pave even on days when the air quality is not the best.” 30 281488_Systems.indd 1 Technology – JANUARY/FEBRUARY 2008 • Hot Mix Asphalt 7/7/06 9:59:33 AM http://www.systemsequipment.com

Table of Contents Feed for the Digital Edition of Hot Mix Asphalt Technology - January/February 2008

Hot Mix Asphalt Technology - January/February 2008 Contents Chairman's Commentary President's Perspective A Conversation with the New NCAT Director NCAT Test Track: Real-Time Testing for Real-World Results Warm Mix: The Lights are Green Illinois Tollway Tests RAP in Fast Forwarded Research Big Creek Teams with TxDOT to Pave Using Innovative Asphalt Mix Diamond Achievement Commendation Issues a Call for Quality Calendar of Events CONEXPO-CON/AGG Product Review Index of Advertisers Advertisers.com

Hot Mix Asphalt Technology - January/February 2008

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