Use of flow properties for rheological modeling of bitumen

The flow properties in steady-shear and dynamic domain are investigated to model the rheological properties of bitumen. The concept of rheogram is used to produce a temperature independent master curve, which is modeled using a simple Carreau–Yasuda (C–Y) equation. It is found that the variation of zero shear viscosity (ZSV) with temperature can be modeled using a simple power law equation. The results showed that the traditional equiviscous method, using a Brookfield viscometer is inappropriate for predicting the mixing and compaction temperatures for bitumen. The applicability of the Cox–Merz rule is found to be valid in the ZSV region. The C–Y equation gave an excellent fit for modeling the variation of complex viscosity/modulus with frequency. Higher dependence of modified bitumen to shear rate indicated that, modified binders can be mixed even at lower temperatures as compared to conventional binders. Accurate determination of ZSV is found to be crucial for successive application of the proposed mathematical model. The modeling technique is also extended for phase angle master curves, using the rheological relationship between loss and complex modulus. Phase angle master curves are found to be more sensitive to the type and chemistry of bitumen.