Workability and mechanical property characterization of asphalt rubber mixtures modified with various warm mix asphalt additives

Warm mix asphalt (WMA) technology offers a promising solution to address the workability concern of asphalt rubber (AR) mixture. Warm asphalt rubber (WAR), the combination of AR and WMA, is expected to be a sustainable paving technology that integrates energy conservation, waste management, noise reduction, and performance optimization. This study aims to characterize and compare the engineering properties of WAR mixture prepared with various WMA additives. To achieve this goal, WAR mixtures were prepared with 40-mesh crumb rubber and five different WMA additives, including Evotherm-DAT, Evotherm-3G, Sasobit, 56# paraffin wax and Aspha-min. Comprehensive laboratory tests were conducted to characterize their workabilities and engineering properties, including moisture susceptibility, stiffness modulus, dynamic modulus, and rutting and fatigue resistance. According to the experimental results, by using WMA additives, a 16 °C reduction in construction temperature can be achieved without significantly deteriorating the mixtures' compactability. WMA additives influenced both the stiffness modulus and dynamic modulus of AR mixture. All WMA additives compromised the rutting resistance of AR mixture except for Sasobit, and the influence of WMA additives on the moisture susceptibility was insignificant. In terms of the fatigue performance, only Evotherm-DAT provided a positive effect. Finally, effects of WMA additives on AR binders and mixtures' properties followed the similar tendency, except for the fatigue performance.