Study of flow behavior for predicting mixing temperature of bitumen

• Modified binders behaves as a shear thinning fluid even at higher temperatures.
• Carreau–Yasuda model can be used to model the viscosity master curves of bitumen.
• Zero shear viscosity can be modeled using a simple exponential law.
• A new method has been presented to predict the viscosity of bitumen.
• The study suggests lower mixing temperatures for modified binders.

Study of flow behavior is necessary for selection of proper grade and viscoelastic characterization of different asphalt binders. Shear thinning behavior of modified binders demands a critical study of viscosity at a wide range of temperatures and shear rates. Such analysis also leads to practical calculation of more appropriate mixing temperatures for asphalt concrete. This study focusses on evaluating the flow properties of different binders for a wide range of shear rates and temperatures using steady shear methods. Carreau–Yasuda (C–Y) and exponential model are combined with the concept of Rheogram to predict the viscosity of bitumen at any desired temperature and shear rate. It was found that C–Y model could be successfully applied to viscosity–shear rate master curves for all types of binders. Exponential model yielded good fit for zero shear viscosity and the model parameters were found to be binder specific. Lower mixing and compaction temperatures were obtained for modified binders, which decreased with increase in shear rate. A more practical method of obtaining mixing temperatures for bitumen is presented and discussed.