Accelerated short-term ageing effects on the rheological properties of modified bitumens with similar high PG grades

Abstract

The main purpose of the study was to evaluate the effects of rolling thin-film oven (RTFO) ageing on some rheological properties of modified bitumens. They are graded as PG 76-xx and were obtained from a 50/70 bitumen graded as PG 64-xx. Three types of polymers – polyethylene (PE), styrene–butadiene–styrene (SBS) copolymer and ethylene butylacrylate glycidylmethacrylate (Elvaloy®) terpolymer – and polyphosphoric acid (PPA) were selected. Ageing mainly increased the complex modulus (G*) and decreased the phase angle (δ) of the bitumens, thereby increasing their stiffness and elasticity. The existence of plateau regions in the master curves of δ for the bitumen+Elvaloy+PPA and the bitumen+SBS can be explained by the distinctive characteristics of the modifiers, since these plateaus were not observed for the other bitumens. The bitumen+SBS and the bitumen+PE showed very high sensitivity to ageing from the point of view of G* and δ, and the opposite is observed for the conventional properties.