Molecular weight distribution of asphalt binders from Laser Desorption Mass Spectroscopy (LDMS) technique and its relationship to linear viscoelastic relaxation spectra

Asphalt binder is a complex viscoelastic hydrocarbon, whose performance depends upon interaction between its physical and chemical properties, both of which are equally important to the successful understanding of the material. In this research effort, a physico-chemical relationship is developed by utilizing the technique of Laser Desorption Mass Spectroscopy (LDMS) to relate the molecular structure of asphalt binders to its viscoelastic properties. The molecular weight distribution (MWD) data obtained from the LDMS technique is used to develop a relationship between number average molecular weight and width of relaxation spectrum of asphalt binders obtained from linear viscoelastic characterization using dynamic shear rheometer. The relationship shows that as the molecular weight of asphalt binders increase, they require more time to relax the developed stresses. Also, the shape descriptors of the molecular weight distribution suggest that asphalt binders possessing greater asymmetry and kurtosis require more time to relax the developed stresses.