Technical report; Sept. 2006-Aug. 2009.

Texas Transportation Institute

NTL-HIGHWAY/ROAD TRANSPORTATION-Materials ; NTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and Performance ;

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During the first half of this research study, TxDOT had only placed 1000 tons of warm mix asphalt

(WMA) as part of a demonstration project. By the end of this three year study, TxDOT had placed more

than 1,000,000 tons of WMA and allowed its use in all dense-graded mixtures through the implementation

of a special provision 341---020. This research project was focused on evaluating all aspects of WMA and

identifying the effects of WMA technologies on mixture design, lab performance characteristics, and field

performance. An ongoing implementation study is underway to continue to monitor performance of WMA

field sections.

Researchers found that WMA technologies improve the compactability of mixtures which can lead to a

reduction in design asphalt content if incorporated in the mixture design process. Laboratory tests indicate

that warm mix asphalt is initially less stiff than hot mix but stiffens considerably during the first year of

service and with increases in laboratory oven curing time/temperature. Field performance of warm mix

projects has, thus far, been comparable to hot mix projects. X-ray CT and ground penetrating radar testing

indicate the uniformity of WMA construction may be better than that for hot mix construction.

US Transportation Collection

0-5597