Recently, researchers in the road field are focusing on the development of green asphalt materials with lower emission of volatile organic compounds (VOCs). The characterization methodology of asphalt VOCs and the influencing factors on VOCs release have always been the basic issue of asphalt VOCs emission reduction research. Researchers have proposed a variety of asphalt VOCs characterization methodologies, which also have mutually irreplaceable characteristics. Asphalt VOCs volatilization is affected by many factors. In this study, asphalt VOCs characterization methodologies were summarized, including their advantages, disadvantages, characteristics and applicable requirements. Subsequently, the influencing factors of VOCs release, such as asphalt types and environment conditions, are summarized to provide theoretical support for the emission reduction research. The classification and mechanism of newly-development asphalt VOCs emission reduction materials are reviewed. The reduction efficiencies are also compared to select better materials and put forward the improvement objective of new materials and new processes. In addition, the prospects about development of VOCs release mechanism of asphalt materials during the full life cycle and feasibility research of high-efficiency composite emission reduction materials in the future were put forward.@en

Asphalt material is an irreplaceable material in road construction. However, it releases VOCs (Volatile Organic Compounds), which do cause pollution to the surrounding environment, during its full life cycle, especially in high-temperature paving stage and summer service time. Asphalt VOCs release mechanism and effective emission reduction technologies are therefore urgently needed. The chemical analysis of VOCs from asphalt binder always invariably excludes a vast number of compounds of unknown relevance, making the quantitative analysis lower data accuracy. In order to address this problem, fingerprint database was developed and introduced in this study, with the detected VOCs data from 104 kinds of asphalt binders. The analysis parameters, including fingerprint components and calibration curves were optimized through quantitative study. With the help of a self-developed fingerprint database, the calculation formulas of single VOC and total released VOCs were established for quantitative analysis of VOCs from asphalt binder. In addition, the influencing mechanism of heating temperature and asphalt types on VOCs volatilization characteristic were explored to achieve emission reduction in asphalt industry.

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Polycyclic Aromatic Hydrocarbons (PAHs) in asphalt materials is a type of serious environmental hazard, and the main pollution resource in road engineering. Aiming at the requirement of PAHs rapid detection method in asphalt pavement construction for low environmental hazard, this research concentrated in experiments about PAHs content, fluorescence characteristics, solvent environment impact mechanism and correlation between fluorescence intensity and concentration in different asphalt materials, based on the fluorescence effect of PAHs from condensed ring structure. It is found that coal tar asphalt has a typical aggregation-caused quenching phenomenon and higher fluorescence quantum efficiency. Taking the three solvent environment parameters polarity, viscosity and pH value as the research objects, the optimal solvent environment for the fluorescence phenomenon of PAHs in asphalt materials was explored and established as dimethyl sulfoxide: tetrahydrofuran: deionized water: glycerol = 1 : 1 : 1 : 2. Under the optimal solvent environment, fluorescence intensity and concentration of the three asphalt materials all showed obvious linear relationship. Under the same concentration condition, fluorescence intensity of asphalt material showed positive correlation with the PAHs content. This study proves that the asphalt material has the linear relationship between fluorescence intensity and PAHs concentration, which will provide theoretical basis for the detection of PAHs content in asphalt materials, and support the development of low environmental hazard in construction technology for road engineering.

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To further explore the long-term aging behaviors of bitumen from the multiscale perspectives, the experimental characterization and molecular dynamics (MD) simulation methods were performed. Series of chemical properties for the virgin and various aged bitumen were evaluated using the TCL-FID, ATR-FTIR, Elemental analysis and GPC tests. The molecular models of virgin and aged bitumen were established firstly, and the influence of long-term aging on the thermodynamics properties was predicted from the MD simulation results. The experimental results revealed that with the aging degree deepened, the resin and asphaltene fractions both increased dramatically, which resulted in the increment of average molecular weight and the more uneven molecular weight distribution in aged bitumen. Moreover, the aging of bitumen led to the increase of the oxidized functional groups (C=O and S=O) index, oxygen content, aromaticity and polarity, while the carbon, hydrogen element contents and the H/C ratio reduced. The density values from MD simulation agreed well with the experimental results, which significantly validated the reliability of molecular models for the virgin and different aged bitumen binders. The MD simulation results demonstrated that the long-term aging remarkably improved the cohesive energy density, solubility parameter and activation energy, however it deteriorated the surface free energy, work of cohesion and self-diffusion coefficient of the bitumen molecular system. This study develops the molecular models of virgin and aged bitumen with different long-term aging degrees, and provides a fundamental understanding regarding the influence of long-term aging influence on the chemo-physical and thermodynamic properties of bitumen.@en

Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges. In the past 10 years, the pavement infrastructure strongly supports the rapid development of the global social economy. New theories, new methods, new technologies and new materials related to pavement engineering are emerging. Deterioration of pavement infrastructure is a typical multi-physics problem. Because of actual coupled behaviors of traffic and environmental conditions, predictions of pavement service life become more and more complicated and require a deep knowledge of pavement material analysis. In order to summarize the current and determine the future research of pavement engineering, Journal of Traffic and Transportation Engineering (English Edition) has launched a review paper on the topic of “New innovations in pavement materials and engineering: A review on pavement engineering research 2021”. Based on the joint-effort of 43 scholars from 24 well-known universities in highway engineering, this review paper systematically analyzes the research status and future development direction of 5 major fields of pavement engineering in the world. The content includes asphalt binder performance and modeling, mixture performance and modeling of pavement materials, multi-scale mechanics, green and sustainable pavement, and intelligent pavement. Overall, this review paper is able to provide references and insights for researchers and engineers in the field of pavement engineering.

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