The Impact of Asphalt Blended with Re-refined Vacuum Tower Bottoms (RVTB) and Its Effect on HMA Mixture Performance

In the past few years, there has been increased interest in the properties of asphalt binders containing Re-refined Vacuum Tower Bottoms (RVTB), the non-distillable fraction from the re-refining of used engine oils, on Hot Mix Asphalt (HMA) performance. Recently published research has provided conflicting results. This study will provide additional information regarding the viability, compatibility and integrity of RVTB in asphalt binders and mixtures. One source of RVTB was blended with PG 64-22 to achieve binder grade of 58-28. A second PG 58-28 was formulated without RVTB for comparison. The asphalt binders were analysed for Superpave PG binder testing, X-Ray Fluorescence (XRF), Polycyclic Aromatic Compound (PAC) content, Gel Permeation Chromatography (GPC) and Therm-Gravimetric Analysis (TGA). The binder testing provides a comparison of the effects of blending RVTB on binder grading, chemical composition, environmental impact, and compatibility of RVTB and asphalt. The second portion of the study compares mixture performance of HMA prepared with neat PG 58-28 and PG 58-28 containing RVTB. Analysis includes volumetric analysis, resistance to moisture damage, resistance to rutting, mixture stiffness and leachate testing on the mixtures according to Environmental Protection Agency (EPA) methods.