Sensitivity of Warm Mix Asphalt to Temperature, Binder Content, and Laboratory Stripping Performance

Warm mix asphalt is a new technology in which additives are used to enable asphalt to be produced at reduced temperatures. This reduction in temperature saves the producer money while lessening the impact on the environment by using less energy. In addition, fewer toxic emissions are emitted by warm mix than hot mix. However, for this new technology to be practical for implementation, a better understanding of how the warm mix additives affect the properties of the asphalt is necessary. The purpose of this research was to examine the effects of warm mix additives on the sensitivity of asphalt to changes in temperature, changes in binder content, and resistance to rutting and stripping.;For this project, Evotherm, Advera, and Sasobit were investigated because they encompass the three main categories of warm mix additives and are some of the most commonly used additives. This study showed that warm mix asphalt is very complex; the properties and performance of these mixtures did not always follow intuitive thought. This complex behavior arose due to the interaction of a number of factors such as nominal maximum aggregate size, binder grade, aggregate type, and additive. In spite of the complex behavior of these warm mixes, a few conclusions could be drawn. First, properties of warm mixes were not vastly different from their hot mix counterparts when produced at an appropriate temperature. For Evotherm, production temperatures should not be reduced more than 60--80°F. For Advera, the temperature should not be reduced more than 40°F, and for Sasobit, the temperature should not be reduced more than 60°F. Second, the sensitivity of warm mix to changes in binder content was similar to that of hot mix. Finally, warm mix asphalt produced in industry will likely require the use of an anti-stripping agent because these mixes showed susceptibility to rutting and stripping.