Bitumen fractionation: contribution of the individual fractions to the mechanical behavior of road binders
Résumé
Anticipation of alternative road binder to replace petroleum derived bitumen requires a deep understanding of the relations between the chemical composition of bitumen and the physical properties, especially rheological properties. The exact molecular structure of the vast number of different molecules constituting bitumen is too complicated to unravel, thus in this paper we propose to fractionate bitumen into four fractions and study their different physico-chemical properties. The melting temperature and the glass transiion of each fractions was determined by DSC while their molecular weight distribution was determined by HS-SEC. Finally, their rheological properties were investigated by DSR. This study highlighted the importance of all bitumen phases: the less polar liquid phase driving the viscous behavior up to-50 °C, the more polar solid phase responsible of the thermal stability and the stiffness, and finally the 2 intermediate viscous oily phases allowing the molecular weight distribution continuity and by consequence allowing to have, on a large temperature range, a viscous liquid behavior at high temperature or low frequency, and an elastic stiff behavior at low temperature. Crystallizable fractions and asphaltene aggregates seemed to act as key molecular structures in the continuous phase.
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