Evaluation of Evotherm® for use in Warm Mix Asphalt

Several new processes have been developed with the goal of reducing the mixing and compaction temperatures of hot mix asphalt without sacrificing the quality of the resulting pavement. One of these processes utilizes Evotherm®, an asphalt emulsion produced by MeadWestvaco’s Asphalt Innovations division. A laboratory study was conducted to determine the applicability of Evotherm® to typical paving operations and environmental conditions commonly found in the United States, including the performance of the mixes in quick traffic turn-over situations and high temperature conditions. Superpave gyratory compactor (SGC) results indicated that Evotherm® may lower the optimum asphalt content; however, it is currently recommended to determine the optimum asphalt content with a typical PG graded binder, and then substitute the Evotherm® emulsion. Evotherm® was shown to improve the compactability of mixtures in both the SGC and vibratory compactor. Statistics indicated an overall reduction in air voids. Improved compaction was noted at temperatures as low as 190°F (88°C). The addition of Evotherm® does not statistically affect the resilient modulus of an asphalt mix nor does it increase the rutting potential of an asphalt mix as measured by the Asphalt Pavement Analyzer. The rutting potential did increase with decreasing mixing and compaction temperatures, which may be related to the decreased aging of the binder resulting from the lower mixing and compaction temperatures. There was no evidence of a difference in indirect tensile strength gain with time for the mixes containing Evotherm® as compared to the control mixes, indicating that a Warm Mix Asphalt (WMA) containing Evotherm® can be quickly opened to traffic. The lower compaction temperature used when producing Warm Mix Asphalt with Evotherm® or any WMA additive may increase the potential for moisture damage. Overall, Evotherm® appears to be a viable tool for reducing mixing and compaction temperatures that can be readily added to hot mix asphalt. Reductions in mixing and compaction temperatures are expected to reduce fuel costs, reduce emissions, and widen the winter paving window.