Rheological evaluation of paving asphalt binder containing bio-oil from rice straw pyrolysis

The conversion of rice straw to bio-oil for substituting asphalt paving materials not only contributes to sustainable development in construction industry, but is also beneficial for resource recovery in agriculture. In this study, rice straw was pyrolyzed to produce bio-oil by using fluidized bed, and the influences of key pyrolysis conditions on product distribution were investigated. Bio-asphalt was prepared by high-speed mixing of pyrolysis bio-oil and petroleum asphalt, and comprehensively evaluated through rheological tests and continuous grading of performance grade (PG). Moreover, microscopic characterization was conducted to further explore the mechanism of bio-oil modification of asphalt. The test results indicate that the yield of bio-oil first rises and then drops with the increase of pyrolysis temperature. As the gas flow rate increases and the biomass particle size decreases, the bio-oil yield shows an increasing trend. The bio-asphalt containing bio-oil from lower pyrolysis temperatures has stronger rutting resistance and lower temperature susceptibility. As the pyrolysis temperature rises, the resistances of bio-asphalt to fatigue and thermal cracking are enhanced. According to continuous PG grading, the widest safe working temperature range is obtained at 450 ℃. Compared to base asphalt, bio-asphalt has superior fatigue and low-temperature performances at high pyrolysis temperatures. Additionally, it can be known from Fourier transform infrared spectroscopy that the modification of petroleum asphalt by bio-oil is a physical fusion process.