Source dependency of rheological and surface characteristics of bio-modified asphalts

Asphalt industry has been looking to reduce their dependence on petroleum-based binders and apply non-petroleum binders as partial or full replacement for asphalt binders. This motivated several attempts by researchers to produce bio-modified asphalts from various materials including woody biomass, waste cooking oil, and bio-oil from animal manure. Accordingly, attempts have been made to incorporate bio-oils/bio-binders (BBs) made from these feedstocks mainly as partial replacements for petroleum-based asphalt. However, this effort has been found to be challenging mainly due to the high variations, in both the feedstock sources and the resulting bioproducts. Accordingly, aforementioned bio-modified asphalts behave differently in terms of their physicochemical and morphological properties, making them to be highly different in terms of their performance as well as their susceptibility to thermal and oxidative ageing. While there have been several studies on the application of various biomass-derived alternative binders, their effects on the physicochemical characteristics of asphalt before and after oxidative ageing have not been studied thoroughly. Therefore, this paper investigates the effects of introduction of four different BBs made from Swine Manure, Miscanthus Pellet, Corn Stover, and Wood Pellet on the rheological and chemical properties of a selected asphalt binder (PG64-22) before and after oxidative ageing. To study the effect of oxidative ageing on the chemical structure of bio-modified asphalt binder, Infrared Attenuated Total Reflectance Spectroscopy (Fourier transform infrared) was utilised. In addition, a Drop Shape Analyser, Rotational Viscometer, and Dynamic Shear Rheometer were used to evaluate the surface properties and rheological behaviour of each bio-modified asphalt binder. Overall, bio-modifiers (bio-oil/BBs) were found to be significantly different in terms of their ageing characteristics. Accordingly, their surface and rheological properties were found to be ranked differently before and after ageing when compared to that of control asphalt binder. The results showed that the BB from swine manure is less susceptible to ageing compared to plant-based bio-oils. This can be further attributed to the chemical structure and the high lipid contents of the BB from swine manure, making it less affected by oxidative ageing.