Effect of Modifiers on Self-Healing and Rheological Properties of Asphalt Binder

The effects of four modifiers were studied to compare their roles in the self-healing ability of asphalt binder: elemental sulfur, with a known plasticizing effect; wax, containing long alkane chains (>C50) with a known crystallizing capability; a plastic oil, with short alkane chains (<C20); and a combination of the wax and plastic oil. The results indicated that the self-healing performance of asphalt binder was increased by each of the four modifiers at 25 °C. Sulfur provided the greatest improvement in self-healing capacity, followed by plastic oil, wax combined with plastic oil, and then wax. This was attributed to sulfur’s plasticizing effect, which is conducive to the self-diffusion of asphalt binder molecules. But at 40 °C, the wax, plastic oil, and wax + plastic oil modifiers weakened the self-healing capacity of asphalt binder, especially the wax modifier. In terms of percent recoverable strain, the asphalt binder modified by wax (long alkane chains) showed the highest percent recovery. The wax-modified asphalt binder also had the highest complex shear modulus compared to the other three modified binders and control binder. And its phase angle was lower than that of plastic oil-, sulfur-modified asphalt binder, and control binder.