REVIEW ON RHEOLOGICAL CHARACTERIZATION OF BIO-OILS/BIOBINDERS AND THEIR APPLICABILITY IN THE FLEXIBLE PAVEMENT INDUSTRY

This paper mainly presents a qualitative review on to what extent the bio-oil has the potential to replace asphalt binder for a sustainable, flexible pavement industry. The current research comprises reviews on the rheological characterization of pure bio-oils and bio-oil modified binders (bio-binders) investigated in the literature. The literature showed that several sources of bio-oils have the potential to contribute to the flexible pavement industry. This research mainly discusses the high-temperature properties, especially viscosity for the construction process (mixing and compaction) and viscoelasticity for the elevated temperature of in-service roads. This review paper encourages orientation towards these kinds of renewable sources of binders in the flexible pavement industry regarding economics, sustainability, and environmental aspects. All reviewed bio-oils in this work, which are waste wood, switchgrass, and waste cooking oil (WCO), could provide a partial or entire substitute binder as they have excellent compatibility with conventional asphalt. Like asphalt, several bio-oils are thermo-plastic viscoelastic and are very susceptible to temperature change. Additionally, they have relatively lower viscosity at mixing and compaction temperatures, which could be reflected by saving energy in the construction process.