Methods for the Quantification of Recycled Engine Oil Bottoms in Performance-Graded Asphalt Cement

Abstract

Recycled engine oil bottoms (REOB) are commonly used in asphalt cements to enhance their grade span and/or lower cost. REOB has been linked to premature road failures, resulting in bans and limits set on its use. This study aims to examine different methods of quantifying REOB in asphalt cement to determine if samples are within allowed limits, as well as measuring their feasibility and accuracy. A total of 17 REOB samples, over 30 mixed REOB in asphalt samples, and over 100 contract samples were examined. X-ray fluorescence (XRF), nuclear magnetic resonance (NMR), and infrared (IR) spectroscopy were all successfully calibrated to quantify the REOB content of a binder. Error is added to the quantification because the type of base asphalt will affect results obtained for each analytical method. Errors from different types of asphalt can be minimized using strategies such as weighted averages of results from different indicators, but error from the variability of REOB composition remains significant.