Journal of Traffic and Transportation Engineering-English Edition最新文献

This review examines the potential of hydrogen, ammonia, and biodiesel as alternative fuels, focusing on spray dynamics, droplet evaporation, combustion, and emissions. Hydrogen offers superior combustion characteristics but faces challenges in NO_x emissions. Strategies like non-premixed direct injection, increased intake boost pressure, and low-pressure EGR are suggested for robust hydrogen combustion in compression-ignition engines. Control of hydrogen start of injection (SOI) and water injection (WI) are identified as effective techniques for reducing NO_x emissions. Ammonia shows inferior combustion and higher NO_x and unburned NH₃ emissions in the same conditions as conventional fuels with conventional engines. Understanding ammonia spray and evaporation conditions is significant for optimizing an ammonia-air mixture and minimizing wall impingement and ammonia trap in the crevice, thereby improving combustion and emission reduction. Increasing intake pressure, injection pressure, and EGR rate, employing a turbulent jet, and preheating ammonia improve efficiency and reduce NO_x emissions. Utilizing ammonia combustion requires the implementation of after-treatment systems such as NH₃ adsorber and DeNO_x catalysts to mitigate unburned NH₃ and NO_x emissions. Biodiesel affects the fuel supply system, combustion, and emission characteristics according to its viscosity and density. Increasing injection pressure and blending with volatile fuels enhance spray and combustion. Optimum biodiesel preheating temperatures for the injection pump and injector are crucial for achieving the best pump capacity and spray formation. By utilizing biodiesel-PODE blends and investigating low-temperature biodiesel combustions, there is potential to improve thermal efficiency and PM-NO_x trade-off. Therefore, carbon-neutral fuel adoption should be accelerated to mitigate CO₂ emissions, highlighting the importance of combustion techniques and emissions reduction strategies.

This study proposes an approach of leveraging information gathered from multiple traffic data sources at different resolutions to obtain approximate inference on the traffic distribution of Chicago's O'Hare Airport area. Specifically, it proposes the ingestion of traffic datasets at different resolutions to build spatiotemporal models for predicting the distribution of traffic volume on the road network. Due to its good adaptability and flexibility for spatiotemporal data, the Gaussian process (GP) regression was employed to provide short-term forecasts using data collected by loop detectors (sensors) and supplemented by telematics data. The GP regression is used to make predictions of the distribution of the proportion of sensor data traffic volume represented by the telematics data for each location of the sensors. Consequently, the fitted GP model can be used to determine the approximate traffic distribution for a testing location outside of the training points. Policymakers in the transportation sector can find the results of this work helpful for making informed decisions relating to current and future transportation conditions in the area.

The increasing impact of the greenhouse effect on ecosystems is prompting transportation agencies to seek methods for reducing CO₂ emissions during pavement construction and maintenance. Additionally, the laboratory mix design process, which involves selecting aggregate gradation and binder content, is time-consuming and labor-intensive. To accelerate the traditional mix design procedure, this study presented a mix design procedure that can automatically determine gradation and binder content based on machine learning (ML) and a meta-heuristic algorithm. Specifically, ML approaches were employed to model the relationship between volumetric properties (mixture bulk specific gravity (G_mb) and air void (VV)) and both mixture component properties and mixture proportion, based on a dataset collected from literature with 660 mixture designs. Integrated with the prediction of ML models and the modified multi-objective grey wolf optimization (MOGWO) algorithm, an automatic asphalt mix design was proposed to pursue three goals, including VV, cost, and CO₂ emission. The results indicated that least squares support vector regression (LSSVR) and eXtreme gradient boosting (XGBoost) achieved the highest prediction accuracies (correlation coefficient: 0.92 for VV and 0.96 for G_mb). The MOGWO algorithm successfully found the 26 optimal mix designs for the case of VV vs. cost vs. CO₂ emission. Compared to the traditional laboratory design, the optimal mixture with VV of 4% achieves a cost saving of 2.46% and a reduction of 4.03% in carbon emission. The volumetric properties of the mixtures output by the approach also align closely with values measured in a laboratory.

In recent years, the temperature-adjusted asphalt pavement has been an extensive concern by scholars in various countries, and this pavement can reduce temperature-related diseases. In this study, the shaped composite phase change materials (CPCMs) were successfully synthesized by two processes, which are vacuum impregnation and epoxy curing. Firstly, the applicability of CPCMs in asphalt mixtures was evaluated by microscopic characterization, chemical compatibility, thermal properties, durability, and leakage stability. Secondly, CPCMs were applied to the asphalt mixture to evaluate its temperature-adjusted characteristics and pavement performance. Finally, the performance of the temperature-adjusted asphalt mixture was analyzed by integrating all factors. The research shows that the prepared CPCMs have excellent thermal properties and durability, the phase transition temperature is 48.93 °C, and the phase transition enthalpy is 106.5 J/g, which fully meets the requirements for use in pavement. The temperature-adjusted asphalt mixture could alleviate the occurrence of extreme temperature, which was 4.9 °C lower than the conventional mixture. The pavement performance of the temperature-adjusted asphalt mixture can meet the specified standards for humid areas. Considering the factors, the recommended amount of CPCMs is 1.5%. The research results provide a basis for the promotion of temperature-adjusted asphalt pavement and effectively support the development of pavement engineering technology.

The temperature and moisture of the pavement structure can be greatly influenced by the wind speed above pavement surface. The wind speed above pavement surface not only is dominated by the wind speed of atmosphere, but also it is highly related to the landform and buildings around road. However, currently there are no studies about the wind field above pavement surface in consideration of the effect of the landform and buildings. A simulation method, which is combined with geographic information system (GIS), wind data from meteorological observatory and computational fluid dynamics (CFD) software, is employed to study the effect of the landform and the wind speed of atmosphere on the wind field above pavement surface. Three cases are studied, including an urban road, a coastal road and a mountainous road. Furthermore, the wind field distribution above road surface in different wind directions was studied in our work. Results indicate that the wind field above pavement surface can be greatly affected by the landforms, buildings and wind direction. This simulation method can provide reliable results for the wind field above pavement surface. The maximum relative errors between simulated and measured wind speed can be less than 20% in the analysis of the three cases. It is recommended that the CFD simulation method is a good tool to accurately know the wind field above pavement surface.

Chip seal is widely used for preventive maintenance to mitigate pavement deterioration, but it is prone to aggregate loss during pavement service. To further promote the development and application of chip seals in road engineering in China, the research progress of the adhesion behavior of aggregate and binder in chip seals was reviewed in this paper, focusing on the adhesion mechanism of emulsified asphalt and alkaline aggregate. The Influencing factors and evaluation methodology of chip seals' aggregate adhesion behavior were also discussed. The results demonstrate that the adhesion process between emulsified asphalt and alkaline aggregate is divided into three processes including infiltration, demulsification, and cluster, which is more complicated when compared to hot asphalt. When designing a chip seal, not only the characteristics of single material should be paid attention to, but also the combination of binder and aggregate matters a lot. To form good adhesion between aggregate and asphalt binder, various influencing factors such as material selection, design method, and construction technical index should be considered comprehensively in the whole design, construction, and operation process. Three methods for evaluating adhesion behavior are summarized, including macroscopic adhesion performance tests, image analysis technology, and model prediction. It is not objective to evaluate the aggregate adhesion behavior of chip seal only by a single evaluation method. A comprehensive evaluation based on the micro-macro multi-scale method should be considered in the future.

The Portland cement concrete pavement (PCCP) often suffers from different environmental distresses and vehicle load failure, resulting in slab corner fractures, potholes, and other diseases. Rapid repair has become one of the effective ways to open traffic rapidly. In this study, a novel type of rapid repair material, basalt fiber reinforced polymer modified magnesium phosphate cement (BFPMPC), is used to rapidly repair PCCP. Notably, the mechanical properties and characteristics of the repair interfaces which are named interfacial transition zones (ITZs) formed by BFPMPC and cement concrete are focused on as a decisive factor for the performance of the rapid repair. The changing trend of the elastic moduli was studied by nanoindentation experiments in the ITZs with the deconvolution analysis that the elastic moduli of certain kinds of substances can be determined. The experimental results show that the elastic modulus of ITZ-1 with a width of about 20 μm can be regarded as 0.098 times of the aggregate, and 0.51 times of the ordinary Portland cement (OPC) mortar. The BFPMPC-OPC mortar ITZ has roughly the same mechanical properties as the ITZ between aggregate and BFPMPC. A multi-scale representative two-dimensional model was established by random aggregate and a two-dimensional extended finite element method (XFEM) to study the mechanical properties of the repair interface. The simulation results show that the ITZ formed by the interface of BFPMPC and OPC mortar and basalt aggregate is the most vulnerable to failure, which is consistent with the nano-indentation experimental results.

Microwave heating, which is used for pre-treatment of concrete before it is comminuted, stands as a strong candidate for selective liberation of multiphase materials like concrete. This paper is concerned with the selective liberation of concrete's raw constituents (particularly aggregate) for recycling by considering the water content of concrete as a parameter of microwave heating for the first time. The deterioration law of the concrete's performance was characterized by the variation in the splitting tensile strength and relative dynamic modulus after heating by microwave at different water contents. Besides, tests were conducted to evaluate the performance of the interface transition zone (ITZ) between aggregate and mortar as well as to investigate the reasons for the stripping behavior of aggregate-mortar, which included the interface tensile strength test, temperature measurement, and porosity test. The deterioration law of splitting tensile strength and relative dynamic modulus revealed that the performance of concrete was subject to different degrees of damage depending on the water content. Furthermore, experimental results showed that interface bonding strength between aggregate and mortar was dramatically impaired, and a large temperature difference was generated between the aggregate and mortar during microwave heating. Meanwhile, the permeable pores increased considerably even when the specimens were dried. In the presence of water, the intactness of ITZ between aggregate and mortar was destroyed by microwave heating, and its performance was significantly lowered, which led to the occurrence of stripping behavior between aggregate and mortar. This was reaffirmed by the microstructure presented by scanning electron microscopy. Thus, the newly developed microwave pre-treatment improved by providing appropriate water contents for concrete corresponding to different strength grades is a promising method for recycling aggregate from waste concrete.

The road construction industry aims to contribute to the protection of already compromised environment. Cold mix asphalt (CMA) is a measure initiated by the road industry to protect the environment and preserve energy. Despite having additional benefits, CMA has attracted little attention due to its inferior performance. CMA's performance is enhanced using a sustainable binder bio-modifier, natural cup lump rubber (CLR) is one of them. This study evaluated the tensile properties, rutting, moisture susceptibility, and adhesion properties of CLR-modified CMA (CMA-CR). The tensile property was enhanced by 26% due to CLR modification. CMA-CR had excellent rutting resistance of less than 2 mm rut depth at 10,000 load cycles, showing 70% improvement compared with conventional CMA. Moisture susceptibility evaluation indicated that CMA-CR had tensile strength ratio (TSR) value of 104%, satisfying the minimum 80% requirement of AASHTO T283. It also retained more than 96% bitumen coating. The moisture damage resistance was improved by 12% and 10% in terms of TSR and stripping, respectively. The durability results revealed that the CMA-CR mixture prevented higher mass loss, representing 14% improvement compared with conventional CMA.

The creep damage evolution of asphalt binder plays a significant role in investigating the formation mechanism of rutting. The rutting is the common distress at high temperatures for asphalt pavements. However, the reliability of existing creep damage parameters is under questioned, and these parameters cannot accurately illustrate the change of intrinsic microstructure for asphalt binder. In this paper, a new test protocol was given access to study the evolution of viscoelastic parameters during creep damage. It was completed by inserting the frequency sweep during creep test. The frequency sweep curve clusters were fitted by the generalized Kelvin-Voigt model for obtaining the change law of model parameters. Based on the change law and sensitivity analysis of model parameters, (E₂ + E₃)/2 was proposed as the creep damage variable. According to the curve of (E₂ + E₃)/2 versus loading time, two stages during the creep test could be identified: an approximate constant value in phase Ⅰ and a linear decrease in phase Ⅱ. Intrinsic differences about creep property of binders could be determined by this new proposed parameter. Above results not only ensure better understanding of the creep damage mechanism of binders, but also lay the theoretical foundation on predicting the anti-rutting performance of binders.