On the existence of wax-induced phase separation in bitumen

Abstract

In previous research efforts, it has been shown that at elevated temperatures, the wax content in bitumen does not have a significant impact on the rutting behaviour of asphaltic mixes. However, the presence of wax in bitumen does cause a physical hardening effect at lower temperatures, which encourages the propagation of cracks. Using waxy bitumen, asphalt mixtures tended to exhibit a higher fracture temperature. The study implied that the effect of wax on bitumen quality and asphalt mixture performance depended on many factors, such as precise chemical composition of the bitumen and particularly the nature of the wax. In the current paper, the discussion of the effect of wax on bitumen is continued. In this paper, atomic force microscopy and neutron scattering techniques are utilised to confirm the appearance of wax-induced phase separation and a new hypothesis is developed for its effect on the cracking and healing potential of the bitumen.

Keywords:

• bitumen
• wax
• phase separation
• atomic force microscopy
• small-angle neutron scattering
• quasi-elastic neutron scattering

Acknowledgements

The research described in this paper has been performed in the context of the ‘Delft Healing Consortium’. In this context, the authors gratefully acknowledge the financial support of Shell Global Solutions, Nynas AB, the Dutch Ministry of Public Works, Ooms Nederland Holding BV and the Delft Centre for Materials (DCMat). Additionally, the authors are grateful for the support and expertise provided by the Western Research Institute and the US Federal Highway Administration. Wim Bouwman and Chris Duif from the reactor Institute Delft are also thanked for their help with the small-angle scattering experiments, and Ewout Kemner and Margarita Russina for their collaboration at the Neat spectrometer at HMI. Finally, the second author would like to acknowledge The Netherlands Organization for Scientific Research (NWO) and the Dutch Technology Foundation (STW) for the VENI postdoctoral scholarship.