Field and Laboratory Investigation of Warm Mix Asphalt in Texas (0-5597-2)

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.