Book Description

Several processes have been developed to reduce the mixing and compaction temperatures of hot mix asphalt (HMA) without sacrificing the quality of the resulting pavement. The purpose of this study was to evaluate the installation of warm mix asphalt (WMA) to compile experiences and offer recommendations for future use. Three trial sections were installed using warm mix technologies between August and November of 2006. Two used the Sasobit technology, and the third employed the Evotherm technology. This report discusses the material makeup of these technologies and documents the production and placement of the three trial sections. The results of this study and further studies can serve as a basis for decision making by the Virginia Department of Transportation (VDOT) regarding the use of WMA technology. Trial sections were initiated through cooperative efforts by the Virginia Transportation Research Council; VDOT districts, residencies, and area headquarters; and participating contractors. Construction used typical mixture designs and practices so that performance under typical construction conditions could be evaluated. General experiences and processes used during construction were documented, and samples were taken for laboratory characterization. Density measurements and cores were taken at each site to determine the initial pavement properties. At the Evotherm installation, asphalt fume sampling was conducted by VDOT's Employee Safety & Health Division to evaluate differences in worker exposure between HMA and WMA pavement laydown operations. The study showed that WMA can be successfully placed using conventional HMA paving practices and procedures with only minor modifications to account for the reduction in temperature. The evaluated technologies affected mixture properties in slightly different ways such as changes in tensile strength ratios and variability in air voids. Additional monitoring of constructed sections was recommended to evaluate long-term performance. Inclusion of WMA technology as an option for paving operations provides potential benefits to VDOT and the contracting community. Theoretically, these technologies could extend the asphalt paving season into cooler weather, allowing for better optimization of paving resources. The technologies also allow the construction of asphalt pavements at lower temperatures, resulting in reduced cooling time before the pavement is opened to traffic. Lower production temperatures may also increase mixture durability by reducing production aging of the mix. Benefits to contractors may include the ability to increase hauling distances between the plant and project, reduced plant emissions resulting in improved air quality, and cost savings because of reduced energy costs. Because of the experimental nature of this study, no cost savings data are yet available to justify or refute the use of WMA technologies.