Effects of Elemental Sulfur on the Aging Trajectory and Adhesion Characteristics of Rubber-Modified Bitumen

This study examines the role of sulfur in rubber-modified bitumen and its response to ultraviolet (UV) exposure in terms of its viscoelasticity, creep recovery, healing behavior, surface chemical oxidation, and surface adhesion. Infrared spectroscopy showed a pronounced enrichment of oxidized sulfur and carbon compounds at the surface of sulfur-modified bitumen after mild heating and especially after UV irradiation. 3% added sulfur increased bitumen plasticity by all measures. UV aging marginally decreased bulk metrics of self-healing, but it severely diminished surface adhesion values, indicating that bulk metrics may not be able to accurately reflect crack-healing behavior if bitumen surfaces are prone to oxidative degradation.