Abstract
Polymer additives are widely used to improve the performances of road bitumen and mixtures including their oxidative resistance. However, their effect on the oxidative mechanism remains unclear. This study includes the investigation of the changes in the rheological response of Polymer Modified Bitumen (PMBs) prepared with the Styrene Butadiene Styrene (SBS) copolymer and Sulphur as cross-linker. The bitumen samples were aged in the Rolling Thin Film Oven (RTFO) and in multiple cycles of Pressure Aging Vessel (PAV). The rheological properties were measured by means of the Multiple Stress Creep and Recovery (MSCR) test. Results show that in the case of cross-linked SBS modified bitumen the polymer phase mitigates the effect of hardening of the bitumen phase on the rheological response as a function of the polymer concentration. Adversely, in the SBS modified bitumen without cross-linker, the effect of the polymer vanishes after the RTFO.
Highlights
Polymer additives are widely used to enhance the properties of road bitumen and mixtures [1,2,3,4,5]
This paper aims at investigating the effects of artificial ageing on different SBS modified bitumen prepared by varying the presence of Sulphur as a crosslinking agent
In the case of the unmodified bitumen (Figure 1), the accumulated final strain at the end of the loading cycles decreases with ageing with the highest value of final strain at the unaged condition and the lowest after four cycles of Pressure Aging Vessel (PAV)
Summary
Polymer additives are widely used to enhance the properties of road bitumen and mixtures [1,2,3,4,5]. In the case of unmodified bitumen, the oxygen uptake causes an increase in the polar fractions (i.e., asphaltenes) characterized by stronger molecular interactions and a reduced molecular mobility. This mechanism results macroscopically in a reduced strain tolerance of the bitumen with the mixture being more prone to crack at intermediate and low temperatures [810]. The polymer degradation appears to mitigate the hardening of the bitumen inducing a more viscous effect on the mechanical response [7, 11,12,13,14,15,16,17,18,19]
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