Characterization of warm mix asphalt through resonant column testing

As the usage of warm mix asphalt (WMA) has gained popularity in recent years, the need has arisen for more characterization techniques and performance prediction through accelerated laboratory testing. This paper presents an experimental study on the shear modulus and damping ratio of asphalt specimens prepared using three WMA technologies: Evotherm, Sasobit, and water foaming, as well as conventional hot mix asphalt (HMA) technology through resonant column (RC) testing. To enable RC testing of asphalt concrete specimens, minor modifications to a traditional RC apparatus were made, which included rigidly attaching additional mass to the driving system to lower the resonant frequency and using epoxy to fix asphalt concrete specimens to the loading plates of the apparatus. The effect of temperature and WMA technology on the dynamic properties was investigated. It is concluded that for the range of temperature tested, specimens prepared using Sasobit technology exhibited the highest shear modulus. Evotherm did not alter the shear modulus of asphalt concrete in a significant manner; while specimens prepared using water foaming technology exhibited slightly softer behavior as compared to those prepared using the conventional HMA technology. It was observed that damping ratio was not significantly altered as a result of using WMA technologies. The four technologies investigated in this study have different temperature sensitivities at different temperature ranges. Hence, it is suggested that shear modulus at a given temperature and its temperature sensitivity at different temperature ranges must be taken into account for evaluating different WMA technologies.