Linear Viscoelastic Analysis of Asphalt Mastics

Abstract

The dynamic shear rheometer (DSR) is used to characterize linear viscoelastic properties of asphalt cement and asphalt mastic (asphalt cement with a filler that is smaller than 75 μm in size). The study focuses on using micromechanical and rheology-based models to assess the effect of two fillers, limestone and hydrated lime, on the performance of the asphalt mastic. Two distinctly, compositionally different asphalt cements were selected to assess the filler effect. Micromechanical models were reviewed, and the most appropriate of these models were used to characterize the viscoelastic behavior of the asphalt mastic (composite). Since the micromechanical models are developed for elastic materials, it was necessary to use the elastic–viscoelastic correspondence principle in order to apply these models. The literature was also reviewed for the most appropriate rheology-based models to account for the effect of fillers in the mastic. The Nielsen model was selected since it employs two rheological parameters to explain the filler effect: the generalized Einstein coefficient and the maximum filler packing fraction. The micromechanical models show good agreement with testing data at low particle volume concentration. The rheological model can successfully predict the stiffening effect of limestone filler when added up to 25% by volume. However the effect of hydrated lime requires a more specific understanding of the substantial surface interactions, which are highly binder specific.