Comparison of Rheological Characteristics of Asphalt Rubber and Warm-Mix Asphalt Rubber before and after the Separation of Insoluble Particles

Warm-mix rubber asphalt (WAR) technology combines the advantages of asphalt rubber (AR) and warm-mix asphalt (WMA) additives, which can ensure the mechanical properties and reduce the traffic noise of the pavement but also lower production and construction temperatures. Current research mainly focused on the performance evaluation of WAR after rubber modification without examining the respective roles of the liquid phases and insoluble particles from the perspective of each component. In this paper, a solid-liquid phase separation method is used to separate the liquid phases (L-AR/L-WAR) and insoluble particles in AR and WAR. A series of rheological tests are carried out on the liquid phases, and the results are compared with those of the base asphalt, AR, and WAR to analyze the influence of rubber powder on the rheological properties and modification mechanism from the perspective of the polymer modification and particle effects. The results show that the insoluble particles enhance the rheological properties of base asphalt at high, moderate, and low temperatures, and the removal of insoluble particles improves the Jnr value of the liquid phase by a factor of 13 but negatively affect workability in AR and WAR, whereas liquid phases have a modest positive impact. Moreover, Evotherm-DAT hindered finer rubber powder modification on AR, whereas Sasobit widened the reduced frequency range of the complex modulus (|G*|).