Microstructure and rheological properties of aged and unaged polymer-modified asphalt binders

The effects of ageing on the microstructure and dynamic rheological properties of three modified asphalt binders are investigated. The asphalt modifiers used comprise crumb rubber (CR), styrene–butadiene–styrene (SBS) block copolymer and a blend or combination of CR and SBS (CCR). To investigate the modified asphalts microstructure, scanning electron microscopy is applied, while for assessing rheological properties at a wide range of temperature, Bending Beam Rheometry and Dynamic Shear Rheometry are employed. Ageing of asphalt during construction and under service conditions is simulated using the rolling thin film oven test and the Pressurised Ageing Vessel procedures. It is observed that ageing makes all three modified asphalts harder, increases their resistance to deformation under high temperatures, and decreases their fatigue and cracking resistance at low temperatures. Comparatively, the CR maintains its bond with the asphalt better than the SBS and the CR-modified asphalt exhibits lower stiffness and lower degree of ageing under cold temperature, while it shows the highest resistance to high-temperature deformation and fatigue. On the contrary, the SBS-modified asphalt exhibits the worst performance in practically every respect compared to the CR- and CCR-modified asphalts.