Investigation of physical properties of base and SBS modified bitumens by rheological test methods

Abstract

Bitumen is modified with various modifiers to diminish the deformation occurred in flexible pavements due to traffic loads and the effects of climate. Polymer modification and more specifically Styrene-Butadiene-Styrene (SBS) copolymer modification is one of the most common methods to enhance the physical properties of bitumen. However, the polymer modified bitumens could exhibit different rheological properties compared to original bitumen. In this work, it is aimed to investigate the effects of SBS copolymer on thermorheological properties of bitumen by means of state of art test methods. To this end, a rheological program including small amplitude oscillation shear test (SAOS), construction of master curves by using time-temperature superposition (TTS) principle, determination of zero shear viscosity (ZSV) and multiple shear creep recovery tests (MSCR) were employed along with other fundamental tests. SAOS test result signifies a positive effect of SBS on the viscoelastic deformation nature of bitumen. The master curves of the complex viscosity of binders reveal that SBS modifier reduced the Newtonian flow properties of bitumen. The decrements in non-recoverable creep compliance and the increment in percent recovery signify that SBS modifier has dramatically enhanced the applicability of bitumen as a binder in flexible pavement at mid to high-temperature ranges.