## 1 Introduction  
Nowadays, the binding agent for road materials is mainly petroleum asphalt extracted from the fossil fuel. With the gradual reduction of oil reserves, oil prices are rising, which results in a higher cost of bitumen. With the growing demand for asphalt, the construction and maintenance costs of highways have also escalated. Therefore, the performance of traditional asphalt must be improved, and the need for alternatives is great [1; 2; 3]. Biomass energy has a wide range of sources, large yields, and low prices. In recent years, a significant number of researchers have turned their attention to bio-oil extracted from biomasses by high-temperature pyrolysis [4; 5; 6]. Many researchers mainly use bio-oil as an additive to modify the base binder. However, most were only focused on the performance of bio-asphal containing a mixture of base binder and bio-oil. [PERSON] et al. [7; 8; 9; 10; 11] modified petroleum asphalt with 2%, 5%, and 10% bio-oil by mass of the asphalt binder. Bio-oil was extracted from pig manure through a process of pyrolysis. Bio-oil modified binders were tested for high-temperature viscosity, and the low and high temperature rheological behavior was examined using a rotational viscometer (RV), a dynamic shear rheometer (DSR), and a bending beam rheometer (BBR). [PERSON] et al. [12] tested 5% bio-oil extracted from pig manure to modify petroleum asphalt PG 64-22; performance was tested by RV, DSR, and BBR, before and after short-term aging. [PERSON] et al. [13; 14] obtained bio-oil from oak wood, and pretreated it for 2 h, then mixed 2% and 4% dosages of polyethylene to modify it. They then determined the viscosity within a temperature range of 40\(\sim\)160 \({}^{\circ}\)C, and analyzed the effect of temperatures on viscosity. [PERSON] et al. [15] applied three types of bio-oil extracted from corn stalks, oak trees, and shredded grass, to modify base asphalt and SBS modified asphalt. The dosages of each bio-oil were 3%, 6%, and 9%, based on binder mass. The high temperature performances of bio-asphalt before and after short-term aging were then tested, and the anti-aging properties were analyzed. [PERSON] et al. [16] tested high-temperature viscosity, density, and the rheological properties of bio-asphalt with different contents of bio-oil extracted from cedar sawdust. The 25% and 50% bio-oils were utilized to replace part of the AC-20 base binder, while the 2% and 8% bio-oil were used for the modification of a similar binder. [PERSON], [PERSON] et al. [17; 18; 19] summarized and compared the bio-oil production procedure and fabrication process of bio-asphalt. They then analyzed the performance and characterization of different bio-binders. They also studied variations in viscosity at different temperatures and with different contents of bio-oil. The results showed that the viscosity of the bio-binder decreased with an increase in the content of bio-oil when the test temperature was under 135 \({}^{\circ}\)C. [PERSON] et al. [20] investigated the conventional performances of bio-asphalt by penetration, softening point, and ductility. The test results indicated that, using a mixture of bio-oil and modified asphalt, the penetration declined with an increase in the proportion of modified asphalt, and ductility improved greatly, which corrected with the disadvantages of hard and brittle bio-asphalts at low temperatures. At present, the research of bio-asphalt mainly focuses on the binder materials, and tests mainly focus on the conventional indexes of the binder materials; such studies lack systematic analysis. The study of bio-asphalts at different frequencies is also rarely reported. In this study, bio-oil was extracted from wood chips, and a bio-asphalt binder was prepared with petroleum asphalt with different contents of bio-oil. The conventional performance indexes of the bio-asphalt binder were tested. The temperature and frequency sweep tests of bio-asphalt with different bio-oil contents were carried out by DSR.