Influence of Viscosities of PDA Pitch and Flux on Blended Bitumen Viscosity

The production of bitumen in Indian refineries is carried out by air blowing and component blending. In the component blending process, a highly viscous propane deasphalted (PDA) pitch is blended with a less viscous flux. The choice of the proportion of these two components is normally arrived at to meet the required technical specification such as penetration at 25°C and viscosity at 60 and 135°C. However, it is not clear at this point in time, the influence of constituent materials on the rheological response of the binder. In this investigation, two ratios of PDA pitch and Flux (75:25, 80:20) were blended in the laboratory. The rheological characterization of constituents and the final blend were carried out using a rotational viscometer at temperatures of 120, 140 and 160°C. Four viscosity mixing 'rules' were used to estimate the final blend viscosity from the individual constituent viscosities. The predictions varied with a wide range of errors.