Effect of warm mix asphalt additive on the workability of asphalt mixture: From particle perspective

Warm mix asphalt (WMA) technologies, in recent decades, have gained much popularity given their proven benefits of improved workability, reduced energy consumption, and improved sustainability. However, how to select a WMA technology and determine its effectiveness at a required condition is still a question. Most current works focus on the binder's rheological properties. Very few have investigated the particles’ behaviors during compaction, which should have a direct correlation with the mixture's workability. With the development of a particle-size Microelectromechanical System (MEMS) sensor, SmartRock, this paper aims to analyze the particle's kinematic behavior during compaction and explore its relationship with the mixture's workability. With this motivation, 5 asphalt mixtures varying in the production temperature and the dose rate of the chemical additive are prepared and compacted in this study. To focus on the methodology, only one chemical additive with several dosage levels is utilized. It is found that particle rotation is a crucial property for compaction and can be used to evaluate the workability of asphalt mixtures. Relative rotation capacity (RRC) and average residual rotation (ARR) are then proposed and used to evaluate the mixture's workability. It is verified that the higher production temperature and dosage rate of chemical additives can both improve the particle rotation and the mixture's workability. The effect of temperature and WMA additive on workability improvement is different for the base conditions (i.e., base production temperature and usage of the WMA additive). Overall, the method proposed in this study is promising for evaluating the workability of asphalt mixtures in compaction.