Waste engine oil influences on chemical and rheological properties of different asphalt binders

•The chemical compounds, molecular weights and rheological properties of asphalt with waste engine oil were studied.•The percentage of large molecular size and carbonyl functional groups were reduced by the addition of WEO.•The addition of WEO decreases the mixing and compaction temperatures of the asphalt mixtures.•WEO compromised the rutting resistance but improved the fatigue behavior of asphalt. The objective of this research is to explore the influence of waste engine oil (WEO) on asphalt binders in terms of chemical compounds, molecular weights, and rheological properties. Three sources of asphalt were modified with WEO at 4 wt% and 8 wt% concentrations. Gas chromatography-mass spectrometry (GC–MS) was used to reveal the main chemical components of WEO. Gel permeation chromatography (GPC) and Fourier transform infrared (FTIR) spectroscopy were used to investigate the changes in the molecular weight and functional groups of WEO-modified asphalt. Rotational viscosity (RV) and dynamic shear rheometry (DSR) tests were used to characterize the rheological properties of WEO-modified asphalt. Results indicate that WEO mainly consists of aromatic solvents, paraffin oil, and polyolefin oil and has similar functional groups as asphalt. The addition of WEO to asphalt reduces the percentage of large-sized molecules in asphalt and decreases the presence of carbonyl functional groups. Meanwhile, WEO significantly decreases the viscosity of binders and reduces construction temperatures. The complex modulus values decrease and phase angle values increase at any given frequency with the incorporation of WEO in asphalt. Moreover, WEO has a negative effect on the rutting resistance performance of asphalt and a positive effect on the fatigue behavior.