Asphalt aging often leads to rapid degradation of road performance, which seriously affects the service life of asphalt pavement. Exploring the influence of asphalt oil sources, asphalt grades, and filler types on asphalt microcharacteristics in the asphalt aging process can provide an essential reference to guide asphalt pavement maintenance. In this study, we selected seven kinds of asphalt and three fillers commonly used in China for research. The pressurized aging vessel (PAV) and homemade ultraviolet (UV) aging equipment were used to perform thermo-oxidative aging and UV aging tests, respectively, of asphalt. The microcharacteristics of asphalt before and after aging were analyzed via attenuated total reflectance fourier transformation infrared spectroscopy and nuclear magnetic resonance 1H spectroscopy. The results show that the oil source of asphalt exerted the most significant influence on the microcharacteristics of the aged asphalt, while the effect of the asphalt grade was relatively limited. The addition of fillers did not affect the aging mechanism of asphalt. UV and PAV aging generated apparent differences in the changes in the aged asphalt microstructure.@en

The chemical and rheological properties of polymer modified bitumen incorporating bio-oil derived from waste cooking oil (WCO) were investigated in this paper. At first, the chemical composition and mixing mechanism of the experimental materials were analysed from the perspective of functional group, and the influence of bio-oil on the activation energy was also researched. Then, the effect of bio-oil on the rotational viscosities of polymer modified bitumen and construction temperatures of corresponding mixtures was studied. Finally, the shear and bending rheological properties of polymer modified bitumen containing bio-oil were investigated. The results show that the bio-oil and styrene–butadiene–styrene (SBS) modified bitumen is mainly physically mixed, the addition of bio-oil decreases the activation energy of SBS modified bitumen. Additionally, the SBS modified bitumen containing bio-oil has lower viscosity values, and corresponding mixtures also have lower construction temperatures. Furthermore, the addition of bio-oil in SBS modified bitumen reduces the shear modulus and increases the bending creep compliance, which means bio-oil has positive effect on the low-temperature thermal cracking resistance performance while sacrificing the high-temperature rutting resistance performance to some extent. Therefore, the incorporation of WCO-based bio-oil in polymer modified bitumen is a promising technique to be used in cold regions where the low-temperature problems are more crucial.@en

Bio-oil produced during the production of biodiesel is a burden to the environment. Recycling and utilization of bio-oil as a substitute for pavement bitumen can help to build an environmentally-friendly and clean infrastructure. In this study, the bio-bitumen was prepared by bio-oil based on free radical polymerization. Different kinds of bio-bitumen products were produced by reacting bio-oil with an initiator and an accelerator solution at different reaction conditions. The orthogonal experimental method was employed to determine the optimal bio-bitumen production process by evaluating the indices of viscosity, rutting factors and fatigue factors. The test results show that the optimal mass proportions of bio-oil:initiator:accelerator solution is 100:1:2. Materials with these mass proportions should react at 100 °C for 2 h to yield the best bio-bitumen product. This kind of bio-bitumen product can be considered as a promising substitute for traditional petroleum bitumen.@en

Subgrade and foundation soils undergo freeze and thaw cycles in seasonally frozen regions that leads to changes in its mechanical properties, causing the degradation of its service performance. This study aims to investigate the effects of freeze-thaw cycles on the dynamic mechanical properties of compacted silty clay. Specifically, the effects of number of freeze-thaw cycle, confining pressure, initial compaction degree, and initial water content on the dynamic shear modulus and damping ratio were studied by using resonant column tests. The test results showed that both maximum dynamic shear modulus and maximum damping ratio of the compacted silty clay sample had a decreasing trend with the increasing number of freeze-thaw cycles. In addition, the maximum dynamic shear modulus was significantly increased with the initial compaction degree and it was decreased with the initial water content, while the maximum damping ratio was decreased with the initial compaction degree and it was increased with the initial water content. Finally, the empirical models of maximum dynamic shear modulus and maximum damping ratio were proposed to consider the varied parameters.@en