Analysis of vacuum tower asphalt extender and effect on bitumen and asphalt properties

Interest has increased related to the impact on asphalt performance of bitumen containing vacuum tower asphalt extender (VTAE), the non-distillable fraction from re-refining used engine oil. This laboratory study provides information on bitumen and asphalt characteristics with and without VTAE. VTAE was blended with PG 64-22 to achieve bitumen grade of PG 58-28. To serve as control a second PG 58-28 was formulated using PG 52-28 with the same PG 64-22. The bitumens were analysed for Superpave PG grade, X-ray fluorescence and polycyclic aromatic compound content, and also using gel permeation chromatography and thermogravimetric analysis. Grade results showed no appreciable difference in ageing between the two PG 58-28 bitumens after Rolling Thin-Film Oven and Pressure Ageing Vessel ageing. The second portion of the study compares asphalt prepared with the two PG 58-28 bitumens including volumetric properties, resistance to moisture damage and rutting, stiffness and fatigue resistance. Fatigue specimens were subjected to short-term and long-term ageing. Asphalt with the VTAE bitumen had equal or increased fatigue resistance in both the short-term and long-term aged conditions. Bitumen was recovered from each ageing condition and tested for binder grade. Comparing the two PG 58-28 bitumens showed no significant difference in stiffness or low temperature properties.