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

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.

This review evaluated research results on polyvinyl alcohol fiber cement-stabilized macadam (PVA-FCSM) to further improve the long-term durability of road structures and promote its in-depth study and high-quality application. The suitable PVA fiber technical indexes for ordinary cement-stabilized macadam (CSM) were recommended. The difference in the mechanical properties between CSM and PVA-FCSM was described. The extent to which PVA fibers enhance the durability of CSM were clarified. Additionally, the mechanism of enhancement of CSM by PVA fibers was revealed. Finally, the performance of each type of fiber cement-stabilized macadam (FCSM) was compared and evaluated. The results indicated that the suggested PVA fiber length and content for CSM were 12–30 mm and 0.6–1.2 kg/m³, respectively. At different ages, the mean degree of improvement in the unconfined compressive strength was 14%, 20%, and 14%, that in the compressive resilience modulus was 8%, 11%, and 6%, and that in the splitting strength was 29%, 15%, and 22%, respectively. At different ages, the mean degree of decreased in the dry shrinkage coefficient was 21%, 16%, and 15% and that in the temperature shrinkage coefficient (20 °C–30 °C) was 23%, 23%, and 18%, respectively. The coefficients increased with extended curing age. Moreover, at the same stress level, PVA-FCSM has a higher fatigue life compared to CSM. The bridging effect, high strength, and high modulus of PVA fiber enhance the strength and anti-cracking of CSM. The recommended fiber type for CSM is PVA fiber.

The exact evaluation of the fusion rate of virgin and aged asphalt is essential to optimize the performance of the recycled asphalt mixture. The fusion rate index was developed by tracing the distribution of tracer asphalt, which contains nano-ferrous ferric oxide (nano-Fe₃O₄) tracer. Laboratory fusion simulation tests were performed on three types of asphalt to obtain different fusion states, and fatigue tests were performed to evaluate the influence of the fusion rate on the fatigue life of the recycled asphalt. It was found that the tracer asphalt containing 4% nano-Fe₃O₄ shows the optimal trace effect, and the developed fusion rate index can quantitatively characterize the influence of different factors on the fusion state of the recycled asphalt. The fusion state is closely related to the fatigue performance of recycled asphalt, and the fusion rate index can fairly evaluate its fatigue performance. The relationship between the fusion rate and the fatigue life of recycled asphalt depends on the factors that cause the fusion rate variation. Under the influence of the amount of rejuvenator, the fatigue life of recycled asphalt grows exponentially with increasing fusion rate due to enhancement of molecular motion as well as a supplement of lightweight components. Under the influence of heat preservation treatment, fatigue life increases linearly with increasing fusion rate. The proposed fusion rate index can be utilized to quantitatively characterize the fusion state of virgin and aged asphalt, thus providing a simple way to guide the practical application of recycled asphalt.

Pervious concrete is a special type of concrete that is of high porosity and contains no or a small amount of fine aggregate, and it is an important basic material for sponge city construction. The presence of a large number of connected pores inside pervious concrete leads to a marked difference in durability failure mechanism compared with that of ordinary concrete.

In this study, the frost resistance and anti-clogging of pervious concrete were introduced in detail, and the methods to improve their performance were summarized systematically. The cracking pattern of pervious concrete is influenced by geometric characteristics and three-dimensional morphological features of pores, resulting in its crack generation, development, and geometry being significantly different from those of ordinary concrete, thus leading to different freeze-thaw cycle mechanisms. In addition, due to its different pore structure compared to ordinary concrete, three types of clogging mechanisms, affecting the long-term permeability of pervious concrete were elaborated systematically (i.e., physical clogging, biological clogging, and chemical clogging). And the ways to improve the anti-clogging of pervious concrete are systematically presented from multiple perspectives. Finally, in order to broaden the engineering applications of pervious concrete, some research proposals are presented in this study.

The autonomous vehicle (AV) technology has the potential to significantly improve safety and efficiency of the transportation and logistics industry. Full-scale AV testing is limited by time, space, and cost, while simulation-based testing often lacks the necessary accuracy of AV and environmental modeling. In recent years, several initiatives have emerged to test autonomous software and hardware on scaled vehicles. This systematic literature review provides an overview of the literature surrounding small-scale self-driving cars, summarizing the current autonomous platforms deployed and focusing on the software and hardware developments in this field. The studies published in English-language journals or conference papers that present small-scale testing of self-driving cars were included. Web of Science, Scopus, Springer Link, Wiley, ACM Digital Library, and TRID databases were used for the literature search. The systematic literature search found 38 eligible studies. Research gaps in the reviewed papers were identified to provide guidance for future research. Some key takeaway emerging from this manuscript are: (i) there is a need to improve the models and neural network architectures used in autonomous driving systems, as most papers present only preliminary results; (ii) increasing datasets and sharing databases can help in developing more reliable control policies and reducing bias and variance in the training process; (iii) small-scaled vehicles to ensure safety is a major benefit, and incorporating data about unsafe driving behaviors and infrastructure problems can improve the accuracy of predictive models.