Oscillatory shear rheometry of hybrid polymer-modified bitumen using multiple stress creep and recovery and linear amplitude sweep tests

Abstract

Modifying bitumen by combining elastomers and plastomers has been reported to result in improved overall performance. However, the assessment of the rheological properties is commonly done in the linear visco-elastic region at low strain levels. In this paper, the rutting and fatigue resistance of modified bitumen was evaluated using multiple stress creep and recovery (MSCR) and linear amplitude sweep (LAS) tests. A base bitumen was modified with styrene butadiene styrene (SBS), crumb rubber (CR), ethylene–vinyl acetate (EVA) and various polyethylene to study the effects of these modifiers on the rheological behaviour of hybrid polymer-modified bitumen (PMB). These effects were measured using the non-recoverable creep compliance (Jnr) and percentage recovery (R%) in MSCR tests and by evaluating the fatigue damage using Viscoelastic Continuum Damage (VECD) analysis in LAS tests. Results showed that combining SBS, recycled polyethylene and sulphur resulted in the highest percentage recovery value, whereas using CR with SBS did not significantly affect the rheological results. Sulphur played an important role as a cross-linking agent. Concerning Jnr, the addition of sulphur help lowers the MSCR characteristic values, hence indicating better rutting performance. From the VECD analysis, the utilization of hybrid polymers improved the fatigue performance when compared with unmodified bitumen. Based on the overall MSCR and LAS results, the utilization of waste polymers such as recycled polyethylene and CR has resulted in highly satisfactory performance for both rutting and fatigue resistance. Hence, the usage of waste polymers can be considered a suitable alternative to replace virgin polymers.