Key Factors and Optimal Conditions for Self-Healing of Bituminous Binder

To identify the key influencing factors and optimal healing conditions for the self-healing ability of bituminous binders, a fatigue-healing-fatigue test was performed under different conditions by the time-sweep mode of a dynamic shear rheometer (DSR). The influence and significance of five factors on healing index were analyzed through a gray correlation analysis. The healing temperature had the most significant correlation with the healing index. In addition, bitumen type, strain size, and degree of damage exhibit significant correlation with the healing index. The effect of healing time is insignificant. This study investigates the flow characteristics of bitumen binder using the viscosity frequency sweep mode of DSR to determine the potential optimal healing temperature. Then, 1stOpt software was used to establish a healing index prediction model to determine the optimal healing time. The optimum healing temperature of #70 matrix bitumen is 47.6 degrees C, slightly higher than the softening point, and the optimum healing time is 48.1 min. The optimum healing temperature of styrene-butadiene-styrene (SBS)-modified bitumen is 76.7 degrees C, slightly lower than the softening point, and the optimum healing time is 30.8 min.