Rheological Indexes

Abstract

An investigation was conducted into several commonly used rheological indexes and their influence on oxidation studies. The evaluation considered the low shear viscosity; the dynamic shear rheometer function, or Glover–Rowe parameter; the dynamic shear crossover modulus (G^*_c) value; and parameters from the Williams–Landel–Ferry and Kaelble shift functions as the rheological indexes in a comparative oxidation characterization between two example asphalt binders. In general, each respective methodology was found to correlate with increasing levels of oxidation but resulted in differing outcomes with respect to oxidation, which depended on the evaluation methodology used. Although each method presented its own merit and respective limitations, a single preferential method was not readily identified. However, the critical need for reliable and sound rheological measures and data processing procedures was clearly demonstrated. This evaluation supported the need for a clear and logical evaluation of the rheological parameters used to characterize asphalt binders. It has been documented that certain rheological indexes have strong correlations to specific distress types or mechanical behaviors and thus may prove beneficial to a particular analysis. However, evaluations must also acknowledge the limitations of selected techniques. When possible, complete characterization through means of the development of full master curves should be beneficial. With sound rheological data and comprehensive measures, several indexes can be determined and provide a more comprehensive view of the investigated material responses.