This paper presents the findings of a study conducted to evaluate the potential effect of bio-asphalt from corn and wood waste on the rheological properties of styrene–butadiene–styrene/rubber composite-polymer modified asphalt. Results showed that bio-asphalt from corn contained significantly high amount of oxygen (62%), whereas petroleum-based asphalt only contained trace amounts of oxygen (0.91%). The average molecular weight, total rings per average molecule, naphthenic carbon rate, and aromaticity of bio-asphalt from corn were smaller than that of petroleum-based asphalt. Meanwhile the characteristics of bio-asphalt from wood waste were similar to that of petroleum-based asphalt, yet the molecular size and polarity of bio-asphalt were slightly lower. For workability, the addition of bio-asphalt decreases the viscosities of composite-polymer modified asphalt. Samples with bio-asphalt from wood waste presented higher viscosity than that with bio-asphalt from corn at the same added amount. A suitable amount (15%) of bio-asphalt showed the best anti-rutting properties under all conditions owing to bio-asphalt can function as light oil to swell polymer or act as a lubricant to limit the intermolecular interactions. Moreover, the addition of bio-asphalt from corn increased the anti-cracking property, whereas the increasing degree of adding bio-asphalt from wood waste were not obvious. The m-values of samples with bio-asphalt from wood waste were also smaller than that of samples added with bio-asphalt from corn. The stiffness of modified asphalt with bio-asphalt from wood waste decreased with an added amount of less than 15% and increased when the bio-asphalt amount exceeded 15%. Samples with bio-asphalt from wood waste also provided better durability and storage stability than that with bio-asphalt from corn. Therefore, bio-asphalt from wood waste was more suitable to represent petroleum-based asphalt partly than bio-asphalt from corn.

To evaluate the long-term service performance of subgrade with high-liquid-limit soil improved by lignin, a drying-wetting cycle test was carried out for the improved soil with 3% lignin content, and comparison was made with quicklime-improved soil with the same properties in terms of pH, unconfined compressive strength (UCS), appearance, and volume stability. Using a scanning electron microscope (SEM), the microscopic characteristics of the lignin-improved soil were analyzed qualitatively and quantitatively. By analyzing the evolution law of the soil microstructure and pores under the action of drying-wetting cycles, the strength degradation mechanism of the improved soil was discussed at the microscopic level. The test results showed that the soil pH value of the lignin-improved soil was more beneficial to the ecological environment compared with that of the quicklime-improved soil. Furthermore, the stability of the lignin-improved soil was better than that of the quicklime-improved soil due to strength loss and increased volume expansion rate caused by the drying-wetting cycles. In terms of the microstructure, the cementing materials enhanced the agglomeration of the soil by wrapping grains and filling pores. Under the action of drying and wetting, the number of pores inside the soil increased, and the soil structure loosened. Under drying and wetting conditions, the strength degradation of the lignin-improved soil was the result of the interaction of pore development and cementing materials dissolution.

In order to produce a high-viscosity asphalt and mixtures that can be used for ultra-thin overlays, high contents of Styrene–butadiene–styrene (SBS, 5%, 6%, 7%), styrene butadiene rubber (SBR, 1%, 2%, 3%) and micro carbon fiber (MCF, 0.8%) were used to modify conventional asphalt to prepare high-viscosity modified asphalt suitable for this purpose. The performance of the modified asphalts was evaluated by conventional index, kinematic viscosity, dynamic shear rheological test (DSR), multiple stress creep recovery test (MSCR), and bending beam rheometer test (BBR). The road performance of the modified asphalt mixtures was evaluated by high-temperature rutting, low-temperature bending, freeze-thaw splitting, fatigue, speckle, anti-skid, and water seepage tests. The results show that increasing the content of SBS can improve the high-temperature deformation resistance, low-temperature failure strain, kinematic viscosity, and viscosity toughness of modified asphalt, and the optimum content of SBS was 6%. SBR can improve the high-temperature performance, kinematic viscosity, and water damage resistance of modified asphalt, and the optimum dosage was 2%. Compared with 5% SBS-modified asphalt mixture, the dynamic stability, low-temperature failure strain, and freeze-thaw splitting strength ratio of 6% SBS + 0.8% MCF composite-modified asphalt mixture were increased by 48.7%, 24.7%, and 5.2% respectively. Compared with the 5% SBS-modified asphalt, the same characteristics of the 2% SBR + 5% SBS + 0.8% MCF composite-modified asphalt increased by 127.1%, 13.5%, and 5.5%, respectively. Compared with 5% SBS-modified asphalt, the fatigue performance of 6% SBS + 0.8% MCF-modified asphalt was improved by 32.2%. The kinematic viscosity of 6% SBS + 0.8% MCF and 5% SBS + 0.8% MCF + 2% SBR modified asphalt met the performance requirements of high-viscosity asphalt and had excellent road performance. It can be applied to ultra-thin overlays to optimize its adhesion with the original pavement.

It is very important for pavement engineers to know which factors are the main reasons for the damage of the paving around manholes. Based on the investigation on the damage of paving around manholes, a vibration model with multidegree of freedom for the vehicle‐manhole cover was established and analyzed. After that, the Matlab software was used to obtain the variation law of impact load over time, and the 95% fourth power of the aggregate force was used as the index to evaluate the pavement damage. Finally, many influencing factors on pavement damage were analyzed by the method of grey correlation entropy. The results indicated that the impact load reached the maximum for the first time when the vehicle reached the top of the manhole cover, which was 1.29 times that of the static load, and the pavement damage coefficient was 2.12 times that of the static load. The influencing factors had different degrees of influence on the pavement damage; from large to small, they were change of road longitudinal slope > driving speed > damping of tire > stiffness of tire > height difference from the pavement damage > height difference from the manhole settlement > stiffness of the manhole cover.