Journal of Road Engineering最新文献

Latex is one of the natural rubbers that is used to enhance the performance of asphalt pavement for the last few decades. The presence of latex, which is categorized as an elastomer, helps to improve pavement performance and durability. Conversely, higher viscosity of latex modified asphalt binder increases the production-temperatures of asphalt mixture, thus consuming higher energy during asphalt mixture’s production stage. In this study, the effectiveness of methanol as an energy-efficient foaming agent was assessed to reduce the viscosity and enhance the workability of the modified asphalt binder. The basic and rheological properties of the asphalt binders were determined through multiple laboratory tests including expansion ratio and half-life, rotational viscosity, softening point, torsional recovery, and dynamic shear rheometer. The properties of asphalt mixtures were assessed through the service characteristics, mechanical performance, and moisture resistance criteria. It was found that the presence of latex results in an approximately twofold higher expansion ratio and a lower half-life of the asphalt binder at about the same ratio. Through the rotational viscosity test, the application of methanol into asphalt binder decreased the viscosity and led to better workability, despite the addition of latex as an asphalt modifier. The application of methanol into asphalt binder improved the workability of mixture samples and lowered the compaction energy of the compaction process, which are the crucial criteria for a better mixing and compaction process. Methanol foamed asphalt mixtures with latex show much higher resistance to moisture damage and stiffness than control sample even though they were prepared at a lower temperature.

Despite almost a century of studies dealing with traffic noise, researchers and practitioners still face old and new issues when designing a low-noise pavement. Given that, this manuscript aims at focusing on a number of unsolved questions, namely theoretical or technological. 1) Is it viable to balance diverse road-related needs (i.e., noise, expected life, texture levels, and friction)? 2) How much does the pavement material affect its acoustic performance (the remaining factors being constant)? 3) How much reliable is the relationship between road texture and mixture aggregate gradation? Based on the analysis of these issues, it emerges that: 1) optimal pavement design involves complex mix optimization and there are theoretical and practical bases to set up a balanced approach to address the complexity of pavement design; 2) high percentages of crumb rubber could optimise road acoustic response but this latter has a relationship with the tyre/road noise (expressed, for example, in terms of close proximity index) that calls for further investigation; 3) aggregate gradation appears to be a reliable basis to predict surface texture and therefore, under given boundary conditions, tyre/road noise; and 4) further studies and investigations are needed in terms of local calibration of deterioration curves and setting up of a sound method to assess the frequency response of asphalt concretes and to govern on-site noise indicators based on mixture properties.

Road material constitutive model is the essential condition of pavement structure design, calculation, and maintenance decision. Experts have conducted in-depth studies on the problems and proposed many meaningful constitutive models. However, these constitutive models have not been summarized and no uniform conclusion on the applicability of them is reported in the academic circle. The linear elastic model based on Hooke's law is still used in pavement structure design. This paper systematically reviewed the existing constitutive models that reflect the materials' mechanical properties and used for pavement structure calculation. These constitutive models were divided into three categories: linear, nonlinear, and damage models under repeated loads. The applicable conditions, parameter determination methods, advantages, and disadvantages of each model were introduced. Moreover, the model's feasibility in structural design and calculation was analyzed. Follow-up studies should focus on the parameter determination standard of viscoelastic constitutive models, the extension of the 1D constitutive model to 3D state, and the nonlinear constitutive models related to stress-strain state to drive the application of the constitutive models in pavement structure calculation and design. Furthermore, to evaluate the life cycle service performance of road materials and structures, establishing the pavement damage model from the structure perspective will be the future direction.

Highway constructions on the Qinghai-Tibet Plateau (QTP) face great challenges induced by the unique local environmental, geological, and engineering conditions. The large area of permafrost, great temperature variability, strong UV rays, and complex geological conditions are the major factors that adversely influence the long-term performance of pavement systems. Since 1960s, Chinese engineers and researchers have started conducting research on the QTP to enhance the performance and durability of pavement systems. The present paper provide a comprehensive review of challenge, research and practice of highway constructions on the QTP including the special environmental and geological conditions, history of highway constructions on the QTP, major challenges and the state-of-the-art technology of subgrade constructions on permafrost, developments of the pavement structures and materials, performance prediction and maintenance methods of pavement surfaces, and applications of the research achievements on the first expressway on the QTP (i.e., Gongyu Expressway). Based on the comprehensive literature review, it can be found that (1) frost heave and thaw weakening induced subgrade disease and longitudinal cracks on the pavement surface are complex coupled water-thermal-load problems. Engineering solutions are focusing on active cooling and thermal insulation methods, which can help to reduce temperature variations in the subgrade and thus improving its stability, (2) the harsh environmental and construction conditions may reduce the early strength and induce premature damage of cement-treated base materials. Some field validations showed that geocell-reinforced or asphalt-treated flexible base materials can provide better long-term performance, (3) the large temperature variability and strong UV rays can significantly accelerate aging of asphalt binders and greatly reduce the service life of asphalt mixtures. Various binder modification methods were developed for improving their viscoelasticity and enhance the low-temperature cracking resistance of pavement surface materials but are still lack of field validation data and comparisons of their life cycle costs. Therefore, it is recommended that a demonstration research project build test sections to examine a range of pavement structures and materials, and compare their long-term performance and life cycle costs, which can serve as important reference for future highway constructions on the QTP.

Hard grade paving asphalts, i.e., having a penetration at 25 ​°C lower than 25 ​mm/10, have experienced, in France, a significant development over the last forty years, linked to the development of high modulus asphalt concrete for rehabilitation then for new construction of road pavements. In the first part, this paper provides a review of the evolution of asphalts in France over the past sixty years towards the use of harder penetration grades and a limitation of the evolution of the asphalt in the mixing plant to avoid early cracking of the pavement. Current recommendations in relation to climatic conditions are mentioned. Rheological characteristics of different hard asphalts produced in France are presented including data on the effect of ageing tests rolling thin film oven test (RTFOT) and pressure ageing vessel (PAV). Hardening of hard asphalt after RTFOT+PAV is comparable to that of softer asphalts. The performance related to low temperature cracking is less which limits the use of plain hard asphalt in pavements subjected to severe winter conditions and requires polymer modification. The specifications for hard grade paving asphalts based on traditional empirical tests included in the European standard developed in the mid 2000s and the choices made in France are presented. A comparison of the specifications for hard grade paving asphalts in the European standards and of those proposed for China shows that the European specifications are more stringent as regards consistency and evolution after ageing tests.

The major contemporary in road pavement engineering is related to the creation of green and sustainable infrastructures, e.g., reduction of environmental impacts, increase in traffic safety, and transportation efficiency, etc. This review presents the recent trends in research and the technical solutions developed so far to address these challenges. After the analysis of research status in the past decades, a novel technology system of eco-friendly pavements is proposed considering two solutions, materials modification and structure improvement. The construction of an eco-friendly pavement can be achieved thanks to several different technologies ensuring permeable, noise-reducing, self-luminous, and exhaust-decomposing properties as well as apporting lower heat absorbing and enhanced anti-/de-icing characteristics. A systematic review of these technologies is presented pivoting on four main aspects: technical principle, material and structural composition, performance evaluation, and engineering application. The current trend in road engineering is combining the pavement infrastructure with various eco-friendly functions, e.g., water permeability, noise reduction, low heat absorption, exhaust gas decomposition, and anti-/de-icing. Finally, the review lists the drawbacks of the existing technologies, including high cost, single function, etc., and depicts the future developing direction and architecture of the next generation of eco-friendly pavements in which the road infrastructure should have more environmentally friendly functions than the existing technology.

To improve the quality of the Hong Kong–Zhuhai–Macao Bridge paving project, a new paving layer material, Guss-mastic asphalt (GMA), was proposed in this paper by combining the advantages of two types of cast asphalt mixtures: mastic asphalt (MA) and Guss asphalt (GA). Based on the characteristics of GMA, to simulate its actual production process, this study developed a small-simulated cooker mixing equipment. Moreover, the flow degree, 60 ​°C dynamic stability, and impact toughness were proposed to be used to evaluate the construction and ease, high temperature stability, and fatigue resistance of GMA cast asphalt mixtures, respectively. Moreover, the quality control standards for GMA paving materials by indoor tests, field trial mix GMA material performance tests, and accelerated loading tests were finalized. The study showed that the developed simulated cooker yielded consistent mixing results in the same working environment as the engineering cooker device. Increasing the coarse aggregate incorporation rate, coarsening the mastic epure (ME) gradation composition, and using a smaller oil to stone ratio can reduce the flowability of the GMA materials to varying degrees. The four-point bending fatigue life and impact toughness of the different GMA materials are correlated well. A mobility of <20 ​s, 60 ​°C dynamic stability of 400–800 ​times/mm, 15 ​°C impact toughness of ≥400 ​N·mm, and cooker car mixing temperature control standard of 210 ​°C–230 ​°C form an appropriate control index system for the design and production of GMA cast asphalt mixtures. Simultaneously, accelerated loading tests verified the accuracy and reliability of the quality control index system that has been used in the GMA paving project of the Hong Kong–Zhuhai–Macao Bridge deck and has achieved good application results.

Adequate pavement skid resistance is a key requirement for safe road operations. Unfortunately, the measurement and prediction of the skid resistance property of an in-service road pavement, or pavement mixture specimens in the laboratory, is a highly challenging process from both theoretical and practical points of view. For more than 60 years, owing to the lack of theoretical solutions to the complex tire-fluid-pavement interaction problem, the practice of pavement skid resistance determination and prediction has essentially been derived from experimental and field observed data. The rapid development of efficient numerical computational techniques and high-power computing facilities in the last two decades made it possible for researchers to numerically solve the tire-fluid-pavement interaction problem. It enables the numerical evaluation and prediction of high-speed wet skid resistance, and the determination of the tire-pavement kinetic friction coefficient in the evaluation of low-speed skid resistance. This paper presents a state-of-the-art review of the research development of theoretical mechanistic approaches in the determination and prediction of pavement skid resistance. It covers the following main aspects of the subject matter: (i) mechanisms of skid resistance generation in dry, wetted (i.e., damp), wet and flooded pavements; (ii) theoretical evaluation of pavement skid resistance in dry, wetted, wet and flooded states; (iii) theoretical approaches in pavement skid resistance prediction; and (iv) concepts of representing the skid resistance state of pavement. The capability of finite element simulation approach for wet skid resistance evaluation with good accuracy is explained. Also highlighted is the practical significance of the Concept of Skid Resistance State. Areas of practical applications of the concept, coupled with the simulation model, are introduced. They include applications in driving safety analysis, road safety design and control, design of paving mixtures, safety maintenance and management of pavements, and harmonization of skid resistance measurements and predictions.