Search

Traditional design methods seldom consider accumulation properties, which influence the structure of asphalt mixtures. Therefore, this study is the first to put forward a modified compressible packing model. The filling characteristics of coarse aggregate were studied. Different matrix compaction indexes η and compaction indexes K were selected to study the influence of the modified compressible model on pavement performance. Design methods based on a 4% air void and minimum voids in mineral aggregate were compared through the volumetric parameters and pavement performance based on the modified compressible packing model. The asphalt mixture performances with three gradations were analyzed. The test results showed that as the matrix compaction index η decreased, the optimum asphalt content of both methods increased, while the VMA decreased. Finally, an optimized asphalt mixture design method based on the compressible packing model was proposed, which showed good prospects for application.

The fatigue performance of hard asphalt is an important factor that affects the service life of asphalt pavement. In order to comprehensively explore the influence of chemical components on the fatigue performance of hard asphalt, and to eliminate the chemical instability between the microstructure of asphalt from different oil sources, seven kinds of hard asphalt were designed and prepared with saturates, aromatics, resins, and asphaltenes (SARA) extracted from the same hard asphalt. Rheological, time sweep and linear amplitude sweep (LAS) tests were carried out to evaluate the fatigue properties. The results show that the complex modulus of asphalt binds increased rapidly with an increase of asphaltene and resins and that the colloidal structure was strengthened, which would increase the fatigue factor. In the time sweep test, the strength of the colloidal structure significantly affected the fatigue life, and the fatigue life was different under different test stresses. In the viscoelastic continuum damage (VECD) model, the cumulative damage was related to the modulus, while with the increase of asphaltene and resins, the fatigue life showed a trend of first increasing and then decreasing. The linear regression analysis showed that the fatigue life of hard asphalt had a good correlation with strain sensitivity. This study investigated the applicability of different fatigue evaluation methods and revealed the influence of four components on the fatigue properties of hard asphalt. The results provide significant insights in the improvement of the fatigue performance of both hard asphalt and corresponding mixtures. [ABSTRACT FROM AUTHOR]

Hub airports typically have multiple parallel runways, requiring aircraft to transfer between them. This increases the risk of runway incursions. End-around taxiways (EATs) mitigate such risk by enabling bypassing without runway crossings. This review summarizes 15 EAT layouts worldwide and presents two classification methods: by configuration (N-type, M-type, Large N-type) and by operational relationship with runways (back-around, runway end-around, start-around). The key benefits of EATs were manifold, including the reduction of runway incursions, controller workload, and delays while improving communication safety, capacity, and efficiency. However, drawbacks such as increased land use, construction costs, and potentially longer taxi times and distances should be considered. Therefore, the optimization of the EAT layout is essential. In pursuit of optimal design, considerations should encompass limiting obstacle surfaces, flight procedures, navigation/lighting facilities, jet blast, and visual obstructions from end-around aircraft to departing aircraft. Notably, challenges arise in reducing distances between EATs and thresholds/ends. The given solutions include displacing thresholds, creating "sunken" lowered elevation EATs, and utilizing terrain shielding instead of metallic visual screens. A case study was introduced to demonstrate the successful improvement of the EAT via sunken EATs and terrain shielding at Guiyang Airport. The conclusion encourages further optimization of EAT layouts that balance safety and efficiency. [ABSTRACT FROM AUTHOR]

In order to study the effects of molding process on the macroscopic performances of cement stabilized gravel, based on two kinds of gradation of skeleton compaction and suspension compaction, eight kinds of cement stabilized gravel were prepared by four kinds of processes: static compaction molding with forced mixing, vibratory compaction with forced mixing, static compaction molding with vibratory mixing, and vibratory compaction with vibratory mixing. Furthermore, the macro-performances of cement stabilized gravel were investigated by adopting the 7 d unconfined compression test, the 28 d single-axis penetration test, the 7 d warming shrinkage test, and the 7 d drying shrinkage test. The underlying microscopic mechanism of the macroscopic property variation of the cement stabilized gravel was analyzed by combining with the microscopic means of scanning electron microscope. The results show that the mechanical properties of cement stabilized gravel with skeleton dense grading under vibration mixing and vibration compaction process are optimal, and its 7 d unconfined compressive strength and 28 d uniaxial compression modulus are improved by 169. 5% and 97. 2%, respectively, compared with that of forced mixing and static compression molding. The vibration mixing vibration compaction techniques can improve the macro performance of cement stabilized crushed stone in terms of promoted the cement hydration product generation, perfect structure, and elevated overall uniformity. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Resources & Ecology is the property of Journal of Resources & Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To adapt to the high temperatures in the summer and resist the shrinkage effect caused by high-temperature differences, this study developed an asphalt material with excellent high-temperature stability and applied it to ultrathin asphalt layer technology to extend the service life of asphalt pavement. The base bitumen was modified using a polyurethane (PU) polymer, which had a significant influence on the high-temperature performance of the bitumen. To achieve the best modification effect, four response indicators (softening point, rutting factor, 135°C rotational viscosity, and dispersion coefficient) were used to evaluate the high-temperature stability, compatibility, and hot-storage stability of the PU-modified bitumen (PMB). Using grey relational analysis and principal component analysis, the four response indicators were transformed into a single-objective parameter (grey correlation degree) to optimize the best combination of parameters for the PMB preparation process. The test results showed that the comprehensive effects of the PMB on the preparation process parameters, from greatest to lowest, followed the order of PU content, shearing time, shearing temperature, and shearing speed, and the optimal process parameters were a PU content of 20%, shearing time of 60 min, shearing temperature of 155°C, and shearing speed of 2,500 rpm. The performance was as follows: a softening point of 90.2°C, rutting factor of 21.21 kPa, rotational viscosity of 2.24 Pa·s, and dispersion coefficient of 0.924. The PMB had good high-temperature stability and hot-storage stability, which allowed it to be effectively applied to ultrathin asphalt layer technology. The preparation process of the PMB provides a technical reference for the development of novel modified bitumen suitable for ultrathin asphalt layers. [ABSTRACT FROM AUTHOR]

Encapsulation is a promising approach to enhance the self-healing ability of asphalt materials. In this study, microcapsules encapsulated waste engine oil was synthesised to improve the self-healing ability of asphalt. The factors affecting the synthesis of microcapsules, especially emulsification and core shell ratio, were investigated through a micro-observation. Dynamic mechanical properties of microcapsule-based asphalts were analysed. Fatigue and healing properties of asphalt binder were evaluated using the entropy and TOPSIS method. Results showed that a combination of sodium dodecyl sulphate and Span-60 showed better emulsification and the optimised dosage of emulsifier was 1.5 wt%. Increasing emulsifying speed, or decreasing core shell ratio, improved encapsulation efficiency. Addition of microcapsules decreased the asphalt stiffness at low frequency and the fatigue resistance of microcapsule-based asphalt went through relatively large decay when microcapsule addition exceeded 4 wt%. Three healing indexes increased with the addition of microcapsules. By entropy weight and the Technique for Order Preference by Similarity to an Ideal Solution analysis, healing index relating to fatigue life shows a larger entropy weight than others and asphalt with 2 wt% microcapsules perform better with respect to fatigue and healing properties. [ABSTRACT FROM AUTHOR]