Rheological and microscopic characteristics of bio-oil recycled asphalt

At present, the general interest of pavement materials in road engineering is to find a substitute for petroleum asphalt. Bio-oil and recycled asphalt are effective ways to solve this problem. Recycled asphalt is obtained by adding appropriate materials or taking specific measures to restore the waste asphalt properties. Since bio-oil has a comprehensive source, low price, and is mainly composed of light asphalt, bio-oil can be used in recycled asphalt. In this study, six aging asphalt, with various aging degrees, were prepared by laboratory aging tests. The rheological behaviors of the aging asphalt were carried out. On this basis, the asphalt with six aging degrees was regenerated by adding related content of bio-oil, and the recycled asphalt?s rheological characteristics were performed. Meanwhile, the optimum bio-oil content range corresponding to various aging degrees of neat asphalt was obtained and compared with the optimal content of a recycling agent. Finally, the mechanism and effect of bio-oil regeneration of aging asphalt were revealed in a microscopic concept. The results demonstrate that the various indexes of neat asphalt have changed with the aging degree, including the increasing of rutting index, strain recovery rate, and stiffness modulus; the decreasing of creep rate and non-recoverable creep compliance. If the bio-oil content is high, the strain recovery rate and stiffness modulus of neat asphalt are signifi-cantly reduced; instead, the creep rate and non-recoverable creep compliance are increased. The addition of bio-oil has an outstanding recovery influence on aging asphalt?s high-and low-temperature behaviors. Microscopic tests manifest that bio-oil and aging asphalt are physical reactions, and the microscopic appearance of the recycled asphalt is similar to the original asphalt. Overall, this work determines the reasonable bio-oil content range in aging asphalt with the various aging degree, which effectively provides a theoretical foundation for bio-oil regeneration of asphalt and promotes its utilization in road construction. ? 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study investigates the use of bio-oil and recycled asphalt as substitutes for petroleum asphalt in road engineering. Laboratory aging tests were conducted on six aging asphalt samples to determine their rheological behaviors. Results showed that bio-oil had a significant impact on the high-and low-temperature behaviors of aging asphalt. Microscopic tests revealed that the addition of bio-oil to aging asphalt led to physical reactions, and the recycled asphalt had similar microscopic characteristics to the original asphalt. Overall, this study provides a theoretical foundation for bio-oil regeneration of asphalt and promotes its utilization in road construction.