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This article investigates the application of high-modulus asphalt mixtures (HMM-13) in the intermediate layer of pavement, addressing rutting issues in asphalt pavements subjected to heavy traffic and high temperatures. The study utilized a 1% dosage of high-modulus modifier, and initially, the mix design of HMM-13 was determined using the gyratory compaction method. Subsequently, this study evaluated the road performance of HMM-13 through tests, including the −10 °C beam bending test, rutting tests at 60 and 70 °C, the freeze–thaw splitting test, and the single-axis compression dynamic modulus test. To ensure the effectiveness of the mixture's on-site application, this study validated the raw material specifications at the construction site and adjusted the mix design accordingly. Water stability tests were also conducted. Finally, a survey of the mixing plant at the construction site was carried out, establishing the relationship between each bin's flow rate and speed ratio. The suitable speed for the production of HMM-13 was calculated. The research results indicate that the optimal asphalt-to-aggregate ratio for HMM-13 is 4.2% (with a comprehensive asphalt-to-aggregate ratio of 5.2%), and the freeze–thaw splitting strength ratio can reach 84.2%. The dynamic stability is 11,217 cycles/mm at 60 °C and 6167 cycles/mm at 70 °C. The stiffness modulus at −10 °C is 5438 MPa, with a failure strain of 2049 με. At 10 Hz and 15 °C, the dynamic modulus is 15,488 MPa, and at 45 °C, it is 3872 MPa. All these indicators meet the requirements for construction technology and pavement performance. [ABSTRACT FROM AUTHOR]

The existing research on pavement mechanics was rarely conducted from the perspective of the spatial stress state. In this research, by utilizing analytical solutions, a three-dimensional space calculation program for asphalt pavement was developed to study the spatial distributions of the stress state and damage risk of the pavement structure. First, this study selected various types of pavement structures to analyze the spatial distribution of the stress state. The results indicated that the important influence factors are the order and quantity of asphalt-bound material, chemically stabilized material, and granular material in the structure. In contrast, the thicknesses of these materials have a limited effect. Then, the stress states of the asphalt pavements in winter and summer were compared. The results demonstrated that the tensile region bulges upward at low temperatures, and the structure is more inclined to experience tension and compression simultaneously. In addition, the failure criterion suitable for asphalt mixture materials was applied, and a strength conversion coefficient between different temperatures was proposed to calculate the damage situations of asphalt mixture layers. Three-dimensional images were generated to display the differences in the dangerous positions and damage forms for different structural types and temperature conditions. [ABSTRACT FROM AUTHOR]

Most countries adopt the mechanical theory of a layered elastic system under vertical load as the design method for asphalt pavement. This calculation theory does not consider the influence of the horizontal force of the vehicle load, and it is also unable to calculate the creep, relaxation, and other behaviors of the pavement material under repeated loads. To overcome these limitations, this research derived the analytical solution of the layered viscoelastic system under horizontal and vertical loads and developed a numerical calculation program for viscoelastic half-space and multilayer system. The accuracy, efficiency, and stability of the calculation program were tested to meet the requirements. The viscoelastic mechanical responses of the checkpoints in structural design under different horizontal load factors were calculated through the program. The results showed that the horizontal load significantly affects the distribution of stress and displacement of the pavement structure and the extent of the horizontal load impact varies in different positions. The horizontal load should be considered in pavement mechanics analysis and structural design. [ABSTRACT FROM AUTHOR]

The economy and rationality of the typical structural scheme for asphalt pavement are directly related to the formation of its service target. Based on the original highway asphalt pavement structure in Jilin Province, the evaluation index system was established by the research of the literature, investigation and Delphi method, and the results of expert consultation were tested by indicators such as enthusiasm, authority and coordination. The Kendall coordination coefficient was 0.803, indicating a strong degree of evaluation consistency. Then, using the finite element method and pavement economic analysis method, the key parameters of pavement structure asphalt, pavement design performance and economy are calculated. Finally, the key indicators in the pavement design process are quantified by using analytic hierarchy process (AHP) and gray relational theory, the weight of each key indicator and the correlation degree of the pavement structure are calculated, and pavement structure 1 is determined to be the best solution. The results show that a decision model for typical structural types of asphalt pavement can be established by using an improved gray relational analytic hierarchy process. In this study, the decision-making model can quickly and conveniently determine the most suitable typical pavement structure, the selected structures are checked, and the calculation results meet the requirements of the specification. However, given the limited reference cases, the proposed pavement structure decision-making method needs to be verified and improved through more practical applications. [ABSTRACT FROM AUTHOR]

Epoxy asphalt is a construction material for pavement structures and has been widely used due to excellent durability and longevity characteristics. Although the asphalt phase could be compensated after epoxy asphalt aging, the epoxy resin phase cannot be regenerated at high value due to irreversible covalent cross‐links, resulting in reclaimed epoxy asphalt pavement (epoxy RAP) being employed as aggregate. In this paper, with consideration toward its nonrenewable characteristic, a recyclable epoxy asphalt is designed preliminarily based on the reversible principle of dynamic covalent bonds, thus focusing on the principle of circular economy and reducing environmental impact. The molecular design of recyclable epoxy asphalt was conducted to justify it theoretically. An environmental impacts assessment is used to analyze energy consumption and carbon footprint caused by using reclaimed recyclable epoxy asphalt pavement (recyclable epoxy RAP) in asphalt mixture manufacturing. The analysis of molecular design showed the feasibility of recyclable epoxy asphalt regeneration. And the mixture containing recyclable epoxy RAP could reduce the emission of GHGs by 34% compared with the epoxy RAP, although the consumption of energy is approximate. Based on molecular design and environmental impacts evaluation, the sustainability of recyclable epoxy asphalt is verified. [ABSTRACT FROM AUTHOR]

This paper studies the influence of geometric structure cutting on transverse crack treatment with the discrete elements method (DEM). Suitable strategies for geometrical structure cutting are put forward. The two-dimensional DEM model of asphalt mixture was established firstly. The asphalt mixture was simplified into a combination of voids, coarse aggregates, and asphalt mortar. The microscopic parameters of asphalt mixture were obtained by laboratory tests of asphalt mortar and mixture. The reliability of the modelling method and the microscopic parameters was verified by the DEM simulation of the laboratory tests of the asphalt mixture. Then, the mechanical response of transverse cracks treatment in different geometrical structures under wheel load and temperature load was analysed based on the orthogonal design method. This work concludes that a quadrangular groove with a depth of no less than 6 cm and a width of 60 cm is recommended for treatment of severe transverse cracks. The depth and width of the groove should be increased proportionally in zones where the traffic is higher or the temperature range is larger, but the breadth to width ratio should be less than 15. [ABSTRACT FROM AUTHOR]

Serious environmental pollution will occur if corn stalk materials are discarded randomly or burned in open air. This study presents a possible method for using corn stalk materials to make fibers used in stone matrix asphalt (SMA) mixtures to address this problem. To obtain an in-depth understanding of the application of corn stalk fibers in SMA mixtures, basic properties such as high-temperature, low-temperature, moisture susceptibility, and fatigue performance, and the dynamic modulus were researched. The performances of SMA mixtures with lignin fibers and basalt fibers were studied as comparative research. Corn stalk fibers and basalt fibers, used as composite fibers, were incorporated jointly into the SMA mixtures, and the performance was evaluated. The test results showed that the high-temperature, low-temperature, and moisture susceptibility performance of SMA mixtures with corn stalk fibers can meet the specification requirements. The addition of corn stalk fibers and basalt fibers in SMA mixtures improved the high-temperature, low-temperature, and fatigue performance of SMA mixtures and had comparable dynamic moduli. A content of 0.6% corn stalk fibers is recommended for SMA mixtures. For the application of composite fibers, contents of 0.4% corn stalk fibers and 0.2% basalt fibers currently are recommended for SMA mixtures. In general, corn stalk fibers can be used in asphalt pavement, and the application of corn stalk fibers can reduce construction costs and environmental pollution. [ABSTRACT FROM AUTHOR]

Foamed asphalt cold-recycled mixtures have been increasingly used in China. However, the interlayer shear performance between the foamed asphalt cold-recycled layer and its top and bottom layers is still not clear. In this study, we explored factors affecting the interlayer shear performance of foamed asphalt cold-recycled layers (FACRL). Regarding the interlayer performance between the foamed asphalt cold-recycled layer and cement-treated base (CTB), the optimal content of the prime coat asphalt was 0.8 kg/m2 , and the prime coat asphalt was recommended to be applied on the surface of the base as soon as the base was paved. Styrene-butadiene-styrene (SBS)-rubber modified asphalt with a content of 2.3 kg/m2 and aggregates with a size range of 4.74–9.5 mm was recommended for use in the seal coats. The aggregates used in the seal coat were recommended to be premixed with a 0.3% asphalt binder to improve the adhesion and to be paved with a spreading area of 65%. Regarding the interlayer performance between the foamed asphalt cold-recycled layer and top hot-mix asphalt (HMA), the interlayer shear strength and fracture energy increased and then decreased with the added tack coat asphalt. The shear strength and fracture energy of the interlayer at 50°C was only 20% and 8% of that at 25°C, respectively. The optimum usage percent of the tack coat binder is 0.4 kg/m2. [ABSTRACT FROM AUTHOR]

To improve the availability of reclaimed asphalt pavement (RAP) in recycled hot mix asphalt (HMA), this study is focused on the mechanical performance of recycled HMA, which is beneficial for environmental conservation and consistent with the concept of sustainability. To alleviate the heterogeneity of the material composition of recycled HMA and enhance the usability and applicability of research means, micromechanical modeling is used to examine the modulus of recycled HMA, which is a critical parameter for asphalt pavement analysis. In this investigation, a four-layer built-in micromechanical model was constructed and derived to characterize recycled HMA. The micromechanical model indicated that the modulus of recycled asphalt was the main factor influencing the modulus of recycled HMA. Thus, the following study took the modulus of recycled asphalt as the main study subject. The frequency sweep test and three-point flexure beam test for recycled asphalt were designed and conducted to clarify the change trend of influence factors and further verify the reasonability and feasibility of the micromechanical model. Considering the diffusion behavior of the rejuvenator, the change trends of the factors are explored. The curing time apparently influences the modulus of recycled asphalt, followed by the curing temperature and the rejuvenator proportion. Finally, analytical results from micromechanical model matched well with the experimental results. The results of this study may be valuable for predicting the dynamic moduli of recycled HMA. • A four-layer built-in micromechanical model for recycled HMA is derived and validated. • The modulus of recycled asphalt prominently affects the modulus of recycled HMA. • The diffusion behavior of rejuvenators is considered in modulus research. [ABSTRACT FROM AUTHOR]

During the design of pavement structures, determining a reasonable thickness for pavement layers is critical. When an expressway is to be built in an area with a poor soil foundation, a reasonable subgrade treatment will make the pavement more durable. However, determining the optimal thickness of subgrade treatment is a difficult task for designers. A thicker treatment means a huge cost increase for the project, whereas a thinner treatment cannot achieve significant improvement in the mechanical behavior of pavement structures. This study used the finite-element method to analyze the mechanical response of real field pavement with subgrade treatments at certain depths. The study used an orthogonal design and gray relational theory to analyze the design indicators and make a better design for the pavement structure of a field expressway. The numerical calculation index and theoretical analysis results show that the treatment depth of subgrade soil has a significant influence on the stresses in an asphalt pavement structure and the bottom tensile strains of the asphalt layers. Therefore, designing a pavement structure with equal structural strength, using a reasonable depth for the cement-treated subgrade, instead of increasing the asphalt layer's thickness, is a more cost-effective solution. [ABSTRACT FROM AUTHOR]

Determining the influential factors of noise characteristics in dense-graded asphalt mixtures and field asphalt pavement is important in constructing highways that are both low noise and environmentally friendly. In this study, the effects of nominal maximum aggregate size, asphalt binder type, air void percentage, and the service life of pavement on the noise absorption characteristics of asphalt mixtures were first investigated in laboratory. Thereafter, tire/pavement noise measurements were conducted on different types of dense-graded asphalt pavements. The effects of the service lives of the pavements, the types of the pavements, driving speeds, and test temperatures on the noise levels of the pavements were also studied. The Zwicker method is used to calculate psychoacoustic parameters on the tire/pavement noise spectrum. The laboratory results indicate that reducing the nominal maximum aggregate size, using rubber asphalt, and increasing air void percentage as well as surface texture depth improve the sound absorption performance of asphalt mixtures. The field measurements show that laying down asphalt pavements with a shorter service life or larger texture depth, using rubber asphalt, reducing traffic speed, and increasing air temperature can reduce noise. [ABSTRACT FROM AUTHOR]

Industry waste materials are commonly used in road engineering. In this study, crushed ceramic waste aggregates (CWAs) were utilized and added into asphalt mixtures to investigate their potential usage. A finite-element method (FEM) was employed first to examine the effect of material thermal conductivity on the temperature gradient of pavement structure. A significant effect of the surface layer's conductivity in asphalt pavement on the temperatures (at the top and bottom positions of the middle layer) was found in model simulation. Next, the mix design for asphalt mixtures with different percentages of CWAs was developed, and their thermal properties were tested. It is concluded that asphalt mixtures with a reasonable substitution percentage of CWA can satisfy pavement performance requirements. The addition of CWAs can reduce the thermal conductivity of asphalt mixtures, which is proven helpful in reducing the temperature gradient of pavement. Finally, it is recommended that less than 40% CWA be added into asphalt mixtures to replace natural coarse aggregates considering its effect on the performance of mixtures. [ABSTRACT FROM AUTHOR]

Recently, electrically heated cable has been used to melt snow and ice from roads around the world. To increase the heat transfer efficiency of asphalt pavement and improve its snow and ice removal ability, but decrease summer solar heating, which could cause rutting, a new asphalt pavement system with various thermal conductivity for layered structures was proposed. This pavement system includes a bottom high-conductivity layer and a top low-conductivity layer. The heat transfer of this pavement system was simulated with the finite element method and tested in a real environment. The results show that a structural combination of a top low-conductivity layer and a bottom high-conductivity layer could be helpful in increasing the surface temperature of pavement during the bottom heating at winter, but decreasing the inner temperature of pavement subjected to summer solar radiation, therefore reducing its rutting potential at summer. • A new asphalt pavement system with various thermal conductivity was proposed. • Graphite and diatomite were selected as the high and low thermal conductivity materials. • The heat transfer of this pavement system was simulated with the finite element method. • A structural combination with high and low-conductivity layer can help to increase the surface temperature. [ABSTRACT FROM AUTHOR]

• The molecular model of foamed asphalt cold-recycled mixture was presented. • Moisture reduce the bonding strength among the components of mixtures. • Bonding between RAP and new asphalt is greater than that between RAP and cement. The recycling and reuse of asphalt pavement have become requirements for environmental protection. Foamed asphalt cold-recycling technology is drawing extensive attention and being widely applied. Foamed asphalt cold recycled mixture has advantages such as energy savings, reduced asphalt content, and low transportation costs, and it has the characteristics of both rigid and flexible pavement. However, foamed asphalt mixtures are complex in composition, as it includes recycled asphalt pavement (RAP), water, new asphalt, aggregate, and cement. Therefore, the interaction mechanisms between recycled asphalt pavement and cement or foamed asphalt within the presence of water in the mixing, curing and service procedures will play a key role in determining the development and deterioration of strength of foamed asphalt cold recycled mixture, which was however not well clarified. This study firstly specified the decrease of strength of foamed asphalt cold recycled mixture when considering the effect of water in field project. It was found that the strength of foamed asphalt cold recycled mixture increased along with the decrease of water content during the curing procedure, and decreased by 15–20% through the winter frost. Then the interaction between RAP and cement or foamed asphalt within and without the presence of water had been analyzed with molecular simulation method. The mechanisms of strength development and deterioration of foamed asphalt cold recycled mixture were clarified from the point of view of molecular interaction. The simulation results indicate that the adhesion strength between RAP and cement is greater than that between RAP and new asphalt. The presence of water simultaneously weakens the adhesive bond strengths between RAP and cement and RAP and asphalt. [ABSTRACT FROM AUTHOR]

• A asphalt mixture with 100% utilization of RAP for the surface layer of RAP was prepared using epoxy asphalt. • The difference between the dynamic modulus of FREAM and normal asphalt mixtures was investigated. • The effect of different aging methods on the performance of FREAM was investigated and recommendations were given for its application. With the continuous development of concepts such as "environmental protection" and "sustainable development", it is difficult for the existing technology of asphalt pavement recycling to meet the needs of efficient utilization of Recycled Asphalt Pavement(RAP). The purpose of this research is to explore the application potential of the fully recycled epoxy asphalt mixture(FREAM), which achieves 100% utilization of RAP, in asphalt pavement. By testing the dynamic modulus, the difference between FREAM and conventional asphalt mixture was explored, and the problems that need to be paid attention to when FREAM is used as the surface course were analyzed. Through two aging methods with different mechanisms, the pavement performance of FREAM before and after aging was studied, including high-temperature performance, low-temperature performance, moisture sensitivity, and fatigue performance. Through this research, it is found that the dynamic modulus of FREAM is higher than that of conventional asphalt mixture, and it has better deformation resistance. However, the influence of the difference in modulus between layers needs to be paid attention to when used as a surface course structure. The FREAM has strong resistance to long-term thermal oxidation aging, and the road performance before and after aging meets the application requirements of the surface course. However, the anti-ultraviolet aging ability of the FREAM is weak, and it is not suitable for the surface of the surface course and more suitable for the middle course and lower layer. [ABSTRACT FROM AUTHOR]