Productions and applications of bio-asphalts – A review

Bio-binder can be partially substituted for petroleum bituminous binder in highway engineering, providing with economic, social and environmental benefits. Biomass commonly used as a renewable energy source is a typically raw material for producing bio-binder, including soybean oil, palm oil, vegetable oil, microalgae, engine oil residue, grape residues, swine waste, and so forth. In this review, the production methods of different bio-oils and bio-binders from various biomasses were introduced firstly. And then, the physical and chemical characteristics of biomass heavy oils were summarized. Meanwhile, the rheological properties and fatigue performances of bio-binders were compared and analyzed. Moreover, conventional engineering characteristics of bio-asphalt mixtures as well as their practical applications were provided and discussed. Current review concluded that the most efficient method to obtain bio-oil from biomass is pyrolysis technology at optimized reaction conditions. The moisture content of bio-oil is found to have significant influences on the performances of bio-asphalt. Overall, various types of bio-binders have their own positive and negative properties. Most of bio-binders can improve the low temperature performance, but unfortunately depress the high temperature performance of bio-modified binders. Future research is recommended to focus on the interaction mechanism of biomass heavy oil and matrix asphalt on microscale. The development of innovative technologies to use more bio-asphalt without prejudice to the performances of asphalt mixtures is also an interesting topic.