Abstract
Re-refined Engine Oil Bottoms (REOB) are one of several products obtained in the refining of recovered engine oil and have been used since the 1980’s in the asphalt industry. Generally, REOB is used to help soften the base asphalt binder and is commonly used from three to ten percent by weight in order to achieve desired low temperature asphalt binder properties. Recently, poor cracking performance in a number of Canadian and northern United States pavement sections have been blamed on the use of REOB to modify the asphalt binder. This has prompted many state agencies in the northeast United States to ban its use. This paper summarizes the laboratory performance of asphalt binders modified with REOB. Two different sources of REOB were blended with different base grades at varying dosage rates in the study. Performance grading, master stiffness curves, double edged notch tension test, and Black Space analysis were conducted on the asphalt binders at different levels of laboratory aging. The research study showed that while being able to achieve softer asphalt binder grades, the addition of REOB accelerates the aging of the asphalt binder with higher levels of age hardening occurring at higher REOB dosage rates. The study also indicated that while the stiffness properties at low temperatures are not impacted by the REOB, the relaxation properties, as measured using m-slope of the Bending Beam Rheometer (BBR), are highly affected. Both the Black Space analysis, using the Glover-Rowe approach, and the DENT test show promise at identifying the age hardening affects.