Resumen de Impacts of WMA Production Temperatures on Binder Aging and Mixture Flow Number
ANDREW HANZ, ENAD MAHMOUD, HUSSAIN BAHIA
Implementation of Warm Mix Asphalt (WMA) has generated interest at state and national levels due to the potential to realize environmental benefits related to lower production temperatures. However, from the aspect of sustainability, WMA must meet or exceed the performance of conventional HMA. Therefore, successful implementation requires mix design procedures that consider the impacts of reduced production temperatures on material properties and the overall performance of the mixture. In this study the effects of reduced aging temperatures were evaluated through characterization of asphalt binder properties after short-term aging at standard and lowered RTFO temperatures and long-term aging under standard PAV conditions. Materials tested included two asphalt binder sources and three WMA additive types. It was found that reduced aging temperatures have a significant influence on the high temperature performance of binders, but a negligible effect on intermediate and low temperature rheological properties evaluated after PAV aging. Results were modeled based on the procedures provided in NCHRP 9- 43 to define the maximum allowable reductions in production temperature for the materials tested in this study. Preliminary findings indicate that the predicted temperature reductions for the FHWA aging model and the laboratory generated data set differed by 9 C, indicating that refinement of the model through evaluation of additional binder sources, grades, and WMA additives is needed. Similar sensitivity to aging temperature was observed in mixture performance testing, emphasizing the need for establishing minimum production temperatures for WMA to ensure adequate field performance.
Keywords: Warm Mix Asphalt, Aging Susceptibility, Flow Number, Performance __________________________ 1Research Engineer, University of Wisconsin, Madison, WI 2Assistant Professor, Bradley University, Peoria, IL 3Professor, University of Wisconsin, Madison, WI The oral presentation was made by Mr. Hanz.
