A comprehensive review of bio-oil, bio-binder and bio-asphalt materials: Their source, composition, preparation and performance

To promote the application of bio-materials and provide a direction for their further researches, this paper comprehensively summarizes the research progress of biomaterials in recent years. The review results show that bio-oil is a mixture obtained from different biomasses through pyrolysis, alcoholysis, acidolysis, high liquefaction, etc., and those biomasses mainly include wood fiber type, waste oil type and animal manure type. Bio-binder refers to the product of bio-oil processed by distillation, extraction oxidation and polymer modification, and it can be served as a modifier, diluent or substitute material of asphalt; the main chemical components of bio-oil include ethers, esters, aldehydes, ketones, phenols, organic acids, alcohols and sugars. Bio-asphalt is obtained by adding bio-binder into the petroleum asphalt for modification or blending, and the shear temperature and shear rate of bio-asphalt derived from wood fiber type and waste oil type are usually higher than that of bio-asphalt derived from swine manure. Compared with petroleum asphalt, bio-asphalt binder usually shows lower high-temperature performance as well as higher low-temperature performance and aging resistance. Also, bio-asphalt mixture generally exhibits lower high-temperature stability, higher low-temperature crack resistance and water stability than petroleum asphalt mixture. Future studies should be conducted combining with the source, composition, preparation, properties and oil production rate of bio-oil. First, how to raise the bio-binder content in bio-asphalt as much as possible while ensuring the sufficient performance becomes the focus of future researches. Second, the micro reaction mechanism between bio-binder and petroleum asphalt should be illustrated in depth. Moreover, developing a complete and unifying technical standard and application specification of bio-asphalt technology is necessary for future researches. Furthermore, determining the optimum bio-binder potentially used as the substitute of petroleum asphalt is also an interesting topic.