Evaluation of the implications on performance for Re-refined Engine Oil Bottoms (REOB) modified bitumen

Abstract

Re-refined Engine Oil Bottoms (REOB) are a waste product from the re-refining process of waste engine oil. There is a large incentive in the world to produce recycled engine oil and the production of REOB in this process is increasing. On the other hand refineries are going through transitions due to economic and regulatory reasons (i.e. IMO 2020) which has an impact on bitumen production process and its properties. As a result, harder grades bitumen are more readily available compared to the softer grades. Moreover, suppliers that are non-refiners are also part of the bitumen supply chain which has led to more variation in bitumen composition and properties. REOB, among other options of blending components, has posed a solution for this problem; making it possible to reach softer grade bitumen by blending the two. The pavement industry is however facing premature failures of pavements, less workable mixtures, earlier deterioration etc. and the question arises whether the diverse sources of blending components like REOB modification of the bitumen could be the cause of them. There exists no unique identification number (for example the CAS number used in the USA) for REOB as a material in Europe, which makes it untraceable when used in bitumen. While one is not obliged to notify contractors of the use of REOB, there also do not exist any guidelines for its use in asphalt mixtures; thus both the identification of REOB in bitumen as well as a clear evaluation of the bitumen properties and performance is wished for.
By using an extensive amount of chemical experimental tools like: Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy (ATR-FTIR), X-Ray Fluorescence (XRF), elemental analysis (CHNO+S), iatroscan chromatography (SARA fractioning), Gel Permeation Chromatography (GPC) and Differential Scanning Calorimetry (DSC) the characteristic properties of bitumen modified with REOB are mapped and identification and quantification of REOB in the bitumen is made possible. This is followed up by performing rheological experiments to map viscoelastic properties of the bitumen, using the Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR). Mechanical performance of the bitumen and asphalt mixtures modified with REOB is evaluated by doing Dynamic Mechanical Analyser (DMA) tests on both cohesive/adhesive behaviour of stone-bitumen film and mastic column tests. Lastly, REOB modified asphalt mixtures are tested with Indirect Tensile (IDT) tests at dry and wet conditions and Cantabro Abrasion tests are done to evaluate impact resistance of the mixtures to simulate ravelling susceptibility.
Using the described approach, this study was able to present a methodology on how to analyse REOB modified bitumen to identify and quantify the presence of REOB and how to evaluate properties and performance of REOB modified bitumen and asphalt mixtures.