Characterization of colloidal stability of blended bitumen

Abstract

Air blowing and propane deasphalting (PDA) blending are the two processes used by the refineries in India to produce paving grade bitumen. In the PDA blending process, the proportion of the constituents (PDA pitch and flux) used in producing bitumen is decided based on the grade of bitumen to be processed. One main issue in the production of bitumen through the blending process is the compatibility of the two constituents used. If the constituents do not exhibit blend stability and compatibility at the microstructural level, it is expected that the binder may not exhibit the required performance even if it meets the appropriate binder specifications such as penetration at 25 °C or viscosity at 60 °C. This study reports one such attempt to check for the compatibility of the blended material using automated flocculation titrimeter. The current investigation primarily focuses on characterizing the influence of proportion of PDA pitch and type of crude source on the colloidal stability of bitumen. The refinery streams processed from a crude oil mixture of Basrah Light (66%) and Murban (34%) was identified as the first crude source and a crude oil mixture of AXL (80%), Basrah (10%) and Iran Mix (10%) was identified as the second crude source. Two different blend proportions of PDA pitch and flux from both the crude sources were made, and these were 75:25 and 80:20. These blend proportions were manufactured in a high shear rate blending facility. All the blends and the components were subjected to titrimetry at the unaged condition. It was seen that the compatibility of the material strongly depended on the proportion of the pitch as quantified by the asphalt state of peptization (P) value. The rheological properties of the blends were quantified by performance grading and frequency sweep tests. It was observed that blend samples with better compatibility also exhibited excellent rheological properties.