Effect of Filler-to-Binder Ratio on the Rheological and Fatigue Performance of Emulsified Asphalt Mastics

The filler-to-binder ratio plays a critical role in determining the rheological performance and fatigue behavior of emulsified asphalt mastics; however, its influence on viscoelastic response and failure characteristics remains insufficiently understood. In this study, emulsified asphalt mastics with different filler-to-binder ratios were prepared using conventional emulsified asphalt and SBS-modified emulsified asphalt. Their rheological and mechanical behaviors were evaluated using dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), linear amplitude sweep (LAS), and bending beam rheometer (BBR) tests. The results showed that increasing the filler-to-binder ratio enhanced the stiffness and high-temperature deformation resistance of emulsified asphalt mastics, as reflected by increases in complex modulus, rutting factor, and yield stress. However, excessive filler content reduced fatigue tolerance and low-temperature flexibility, as indicated by decreases in yield strain, failure strain, and m-value, together with an increase in low-temperature creep stiffness. The MSCR results further showed that higher filler contents changed the nonrecoverable creep response of the mastics, and negative Jnr-diff values at high filler-to-binder ratios suggested a transition in the rheological response of the highly filled mastic system. For SBS-modified emulsified asphalt mastics, a distinct phase angle inflection point was observed during fatigue loading, which may serve as a rheological indicator for characterizing the transition of fatigue damage behavior. These findings clarify the effect of filler-to-binder ratio on the rheological evolution, deformation resistance, fatigue behavior, and low-temperature performance of emulsified asphalt mastics. The results provide practical guidance for optimizing filler-to-binder ratio design in pavement engineering applications.