Laboratory Evaluation of a Warm Asphalt Technology for Use in Virginia

About the report:

Rising energy costs and increased environmental awareness have brought attention to the potential benefits of warm asphalt in the United States. Warm-mix asphalt (WMA) is produced by incorporating additives into asphalt mixtures to allow production and placement of the mix when heated to temperatures well below the 300°F+ temperatures of conventional hot-mix asphalt (HMA). Potential benefits such as reduced plant emissions, workability at lower temperatures, extension of the paving season into colder weather, and reduced energy consumption at the plant may be realized with different applications. Trial installations of WMA, including two sections using the Sasobit WMA additive, have been investigated in Virginia. This study presents the results of laboratory testing to evaluate the performance of the mixtures used in the two Sasobit trial sections. The evaluation included comparisons of compactibility, volumetric properties, moisture susceptibility, rutting resistance, and fatigue performance between the HMA and WMA mixtures used in each section. Mixtures produced in the laboratory under conditions of varying temperatures and aging periods were tested, and the effects of temperature and aging were evaluated. The long-term performance of the two test sections was also modeled using the Mechanistic-Empirical Pavement Design Guide.Few differences were found between the HMA and WMA mixtures evaluated. The performance of WMA and HMA was similar when evaluated for moisture susceptibility, rutting potential, and fatigue resistance. The MEPDG-predicted distresses supported these conclusions; the predicted long-term performance of WMA and HMA was comparable. From these results, the recommendation was made that the Virginia Department of Transportation develop a special provision for the use of WMA. Despite its benefits, direct cost savings from the use of WMA are unlikely to be seen by VDOT. Currently, one concern with the use of WMA is the initial cost, which varies depending on the technology used. The use of WMA technology requires either additives, a recurrent cost, or asphalt plant modifications, requiring capital investment. Over the long term, the use of WMA could save VDOT considerable dollars if the reduced aging of the mix translates into longer life; however, this has yet to be proven as WMA has not been employed for a sufficient time period to allow an evaluation of this benefit.

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