Molecular weight distribution of asphaltic paving binders from phase-angle measurements

Based on previous works on polymers and regular bitumens, a new method for determining the molecular weight distribution (MWD) of asphaltic paving binders, using the phase angle (´) of the complex modulus measured in the linear viscoelastic domain, has been developed in this paper. MWDs of pure petroleum bitumens, natural bitumens, modified bitumens and arti-ficially aged bitumens are calculated by this method and compared with MWDs obtained by gel permeation chromatography. The two methods give comparable results, but the ´-method developed here is more sensitive to the molecular weight of species. This method is very simple to implement, and seems a powerful tool in the determination of MWD of bitumens, in the visualisation and repartition of modifiers in the bitumen matrix and in the ageing monitoring and quantification.