Rheological and ageing properties of asphalt bio-binders containing lignin and waste engine oil

• Lignin improves resistance to permanent deformation at high temperatures. • Waste engine oil acts as a lubricant and performs well at low temperatures. • Using lignin and WEO in asphalt binder neutralizes each other's negative effects. • Lignin and WEO can delay the ageing of the binder. • Using Lignin and WEO can improve bitumen rheological and ageing properties. The environmental issues caused by the application of bitumen in pavement construction and its high cost have motivated researchers to seek suitable alternatives. The present study aims to propose lignin as a bio-additive and waste engine oil (WEO) as a waste industrial product as partial substitutes for bitumen and to investigate their rheological and ageing characteristics. The samples tested included PG64-22 as the virgin binder, samples containing 5% and 10% lignin, samples containing 4% WEO, as well as samples with both additives. Rotational viscometer (RV), dynamic shear rheometer (DSR), bending beam rheometer (BBR), and multiple stress creep recovery (MSCR) tests were conducted to evaluate the rheological characteristics of the samples. Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) were performed to investigate the effects of these additives on binder chemistry. The viscosity, rheological and chemical ageing indices were also measured. The results indicated that lignin increased viscosity and improved the resistance of asphalt binder to permanent deformation at high temperatures. However, due to the increase in the stiffening of the binder, lignin had a negative effect on binder performance at low temperatures. Adding WEO, on the other hand, reduced the viscosity of the binder and enhanced its performance at low temperatures, but negatively affected high-temperature rutting performance. Binders containing both additives slightly had better performance at both high and low temperatures. WEO reduces the stiffening of aged binders due to their lubricating properties whereas lignin can prevent binder oxidation to some extent. Therefore, using these two additives may be a suitable solution to reduce bitumen consumption and improves its rheological and ageing properties based on the results in this study.