Finding an alternative or supplementary test method to evaluating the low temperature performance of asphalt is an area of considerable interest. This paper tries to explore the possibility of using the dynamic shear rheometer (DSR) method for assessing the low temperature properties of styrenebutadienestyrene (SBS) modified asphalt. In the study, 60/80 and 80/100 pen grade asphalt binders, named binder A-70, binder B-70 and binder C-90, are used to produce the SBS modified asphalt samples. After that, the low temperature performance of the asphalt binders is characterized by using bending beam rheometer (BBR) test. The results indicate that the low temperature performance of the different binders is related to the source of the binder. The low temperature performance of asphalt could be improved with the addition of the SBS. The DSR test is used to develop the complex modulus master curves for binders. Based on the principle of time–temperature conversion, the glass transition temperature of asphalt is calculated by the Williams–Landel–Ferry (WLF) equation. The glass transition temperatures (T_g) of base asphalt and the SBS modified asphalt are determined by the viscoelastic parameters of the master curve and the WLF equation coefficients based on the time–temperature superposition principle. By establishing the relationship between the critical temperature and the T_g of the asphalt binder, the effectiveness of the method established in this paper is verified. The advantage of this method is the ability to use the DSR test for the rapid evaluation of the low temperature performance of asphalt, which is able to reduce testing materials and save testing time as well. The glass transition temperature of the SBS modified asphalt is closely associated with aging degree, asphalt source and the SBS content.

Compaction is a critical step in asphalt pavement construction. The objective of this study is to analyze the mesoscale mechanical behaviors of coarse aggregates in asphalt mixtures during gyratory compaction through experiments and numerical simulation using the Discrete Element Method (DEM). A novel granular sensor (SmartRock) was embedded in an asphalt mixture specimen to collect compaction response data, including acceleration, stress, rotation angle and temperature. Moreover, the irregularly shaped coarse aggregates were regenerated in the DEM model, and numerical simulations were conducted to analyze the evolution of aggregate interaction characteristics. The findings are as follows: (1) the measured contact stress between particles changes periodically during gyratory compaction, and the amplitude of stress tends to be stable with the increase of compaction cycles; (2) the contact stress of particles is influenced by the shape of aggregates: flat-shaped particles are subjected to greater stress than angular, fractured or elongated particles; (3) the proportion of strong contacts among particles is high in the initial gyratory compaction stage, then decreases as the number of gyratory compactions grows, the contacts among particles tending to homogenize; (4) during initial gyratory compactions, the normal contact forces form a vertical distribution due to the aggregates’ gravity accumulation. The isotropic distribution of contact forces increases locally in the loading direction along the axis with a calibrated internal angle orientation (1.25°) in the earlier cyclic loading stage, then the local strong contacts decrease in the later stage, while the strength of the force chains in other directions increase. The anisotropy of aggregate contact force networks tends to weaken. In other words, kneading and shearing action during gyratory compaction have a positive impact on the homogenization and isotropy of asphalt mixture contact forces.

This article provides a comprehensive review of the research progress on porous asphalt mixtures, focusing on their durability, permeability, low-temperature performance, and functionality. The study examines factors influencing the anti-raveling performance of porous asphalt, including modified asphalt binders, fibers, aggregates, traffic loads, and environmental conditions. It also discusses the impact of porosity, pore structure, and temperature variations on the low-temperature cracking resistance of porous asphalt. Furthermore, the article explores the permeability of porous asphalt mixtures, emphasizing the influence of pore characteristics, water flow directions, clogging processes, and pavement designs. The sound absorption and skid resistance properties of porous asphalt are also analyzed, highlighting the importance of porosity, texture depth, material properties, and water film thickness. The study concludes by proposing improvement measures and optimization suggestions for porous asphalt mixtures, providing valuable references for future research and applications. Finally, several future research topics for porous asphalt mixture are proposed. Further studies on porous asphalt pavement involves seeking performance balance, ensuring improvement without detriment. Researching factor interactions, building a model, exploring industrial waste use to cut costs, reduce pollution and promote its environmental application for diverse traffic and environment needs.

For gyratory compaction, the concept of the locking point was initially developed to identify the compactability of asphalt mixes and to alleviate potential aggregate crushing in the mold. Most previous studies on the locking point were based on specimens’ height change. Recent studies have indicated that the gyratory locking point of cold mix asphalt mixtures could be determined by the rotation angle range indicator using SmartRock. However, height or rotation angle change ultimately reflects a change in volume. Additionally, there is no clear physical and mechanical connection between the volume change and the gyratory locking point. In this paper, a stone mastic asphalt mixture (SMA 13) was selected for gyratory compaction applying various compaction temperatures. The compaction data were recorded by a SmartRock embedded in different positions. Collected data included stress, rotation angle, and acceleration. The major findings are as follows: (1) the specimen’s locking point could be determined based on a representative stress value when the SmartRock was embedded in the specimen’s center, and the results are close to the traditional evaluation results (LP3 or LP2-2-3); (2) the representative rotation angle value reached a plateau earlier than the representative stress value; (3) the representative acceleration value is not suitable for characterizing the interlocking process during gyratory compaction.

With the rapid development of urban rail transit, the impact of the construction of large-scale deep and circular foundation pits (LDCFPs) on the surrounding environment has become increasingly prominent; however, there is no definite standard for the design theory and construction method of the retaining structure of LDCFPs; therefore, the such standard needs further research and exploration. The paper is based on the LDCFP engineering of a subway station in Wuhan, China. Two partitioned excavation methods (step-by-step and synchronous excavation) of LDCFP were discussed by numerical simulation; the deformation characteristics of the soil around the foundation pit, the lateral deformation of the retaining structure in each partitioned district, and the distribution of the supporting axial force were analyzed; the deformation law of LDCFP was revealed; and the safe and economic excavation method was determined. The field monitoring test was carried out to reveal the deformation characteristics and stress evolution behavior for the supporting structure of the LDCFP in the subway station. It was concluded that the construction method of synchronous partitioned excavation in the same layer is more conducive to controlling the overall deformation, with the deformation of the circular retaining structure being uniform and the “vault effect” of the circular retaining structure having a certain constraint on the deformation of the foundation pit. The research results can provide guidance for the design and construction of supporting engineering and similar engineering.