## 4 Results and Discussion  
### Conventional Tests  
The results of conventional performance indicators of bio-asphalt binders with 5%, 10%, and 30% bio-oil, and 5%-S, 10%-S, were analyzed. The penetration ratio and residual penetration ratio of unaged and RTFO-aged bio-asphalt are shown in Figure 3. For the unaged bio-asphalt, with an increase of bio-oil content, the penetration of bio-asphalt increases. This showed that, with the incorporation of bio-oil, asphalt became soft; its high temperature performance was reduced to some extent. Meanwhile, the penetration of 5%-S and 10%-S were decreased by 5% and 10% respectively, due to the incorporation of SBS. Compared with the matrix asphalt 50#, the penetration increments of unaged bio-asphalt with 5%, 10%, and 30% bio-oil were 5%, 12.3%, and 79.2%, respectively. This indicated that a higher bio-oil content produces a greater change in penetration. After short-term aging, the bio-asphalt became harder, and resistance to rutting increased for the RTFO-aged bio-asphalt. The change in the residual penetration ratio also illustrated this point. Compared with RTFO aged bio-asphalt with 5% and 10% content bio-oil, the penetration of RTFO-aged bio-asphalt with 30% bio-oil was much smaller, and the residual penetration ratio was 36.73%. This was due to the effects of the volatility of the light components of bio-oil during RTFO aging. An increase in bio-oil content would lead to an increase in the aging and variability of bio-asphalt. The residual penetration ratio of bio-asphalt with 5% content bio-oil and 5%-S, 10%-S could meet the requirements of 50# asphalt binder, as outlined in Technical Specifications for Construction of Highway Asphalt Pavements (JTG F40-2004). However, the residual penetration ratio of bio-asphalts with 10% and 30% content bio-oil would not meet the requirements. The softening points of unaged and RTFO-aged bio-asphalt are shown in Figure 4. The softening point of unaged bio-asphalt decreased with an increase of bio-oil content. This showed that, with the incorporation of bio-oil, the high temperature performance of bio-asphalt was reduced to some extent. Meanwhile, the addition of SBS could increase the softening point of bio-asphalt with 5% and 10% bio-oil. The softening point of RTFO-aged bio-asphalt increased with an increase of bio-oil content. This illustrated that, with the incorporation of bio-oil, the asphalt became harder, and the resistance to rutting is increased. The softening point of unaged and RTFO-aged 10%-S increased more than that of 5% bio-oil. The incorporation of SBS could improve the high temperature performance of bio-asphalt. Compared with the original asphalt, the difference of the softening point of unaged and RTFO-aged bio-asphalts with 5%, 10%, and 30% bio-oil content were 9.6 \({}^{\circ}\)C, 16.5 \({}^{\circ}\)C, and 20.6 \({}^{\circ}\)C, respectively. With an increase of bio-oil content, the softening point increased. This was caused by the aging of bio-asphalt, and indicated that with a greater amount of bio-oil, the aging degree of bio-asphalt increases. Figure 3: Penetration ratio and residual penetration ratio of unaged and RTFO (Rolling Thin Film Over) aged bio-asphalt. (**a**) Penetration ratio; (**b**) Residual penetration ratio. As seen in Figure 5, with the increase of bio-oil content, the ductility of unaged bio-asphalt increased. As compared with the base asphalt binder, the ductility of bio-asphalts with 5%, 10%, and 30% bio-oil content increased by 2.6%, 8.7%, and 52.8%, respectively. This showed that the addition of bio-oil could improve the low temperature performance of bio-asphalt, and improve the low temperature, anti-cracking ability of asphalt before RTFO-aging. Meanwhile, the ductilities of 5%-S and 10%-S were increased by 16.5% and 13.2%, respectively, indicating that the incorporation of SBS would improve the low temperature properties of the bio-asphalt binder.