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An ultrathin seal serves as a preventive maintenance technology. The design method predominantly relies on engineering experience and lacks a theoretical foundation. In order to investigate the impact of aggregate size, spreading mass, and original pavement texture depth on the formation of an ultrathin seal, a compaction model was developed using the discrete element method (DEM). Different aggregate sizes and spreading masses were analyzed to examine the particle structure and thickness. The three-dimensional (3D) Weierstrass–Mandelbrot (WM) function was used to reconstruct random rough surfaces to assess the effect of the original pavement texture depth (1, 2, 3, and 4 mm) on voids and dosage of filling asphalt. Results showed that the dynamic compaction led to a rapid increase in collision velocity and then declined sharply by 0.02 s, eventually reaching zero by 0.3 s. Particle contacts steadily increased to 365 by 0.3 s and kept stable after the plateau, indicating the formation of an interlocking structure. Coordination numbers and contact vectors varied with particle size and spreading mass, which were more pronounced for small particles. However, the smaller particles (<4.5 mm) had negligible compaction effects, suggesting that the optimal aggregate size should be 3–5 mm. Excessive spreading mass resulted in a multilayered structure incompatible with the single thickness requirement and the recommended range was 9–12 kg/m2. Furthermore, greater texture depth led to higher void content at the bottom of the seal, requiring more filling asphalt. Therefore, when designing asphalt dosage, both the compaction and the variation in voids due to the original pavement texture depth should be considered to ensure sufficient contacts. [ABSTRACT FROM AUTHOR]

Large stone porous asphalt mixes (LSPMs) have the characteristics of large gaps, large content of coarse aggregate, and large particle size of coarse aggregate. Compared with the traditional asphalt-treated base (ATB), LSPM forms a more obvious skeleton structure in the process of bearing load. In this study, the discrete element method (DEM) model of LSPM is established, and an evaluation method for studying the bearing capacity and high-temperature performance of LSPM through an internal skeleton network is proposed. Firstly, the DEM model of asphalt mixture with different gradations is established, and the virtual uniaxial penetration test is carried out. Then, the performance of the skeleton network inside the asphalt mixture is analyzed, and the contribution of each group of aggregates to the skeleton network is further studied. The experimental results show that the bearing capacity of an asphalt mixture is closely related to the performance of internal skeleton network. The skeleton network inside the asphalt mixture is extracted by the value of the contact force, the angle between the contacts, and the contact continuity. When the skeleton network has better bearing capacity and load-transfer capacity, the asphalt mixture can bear more external load in the virtual penetration test. The contribution of different coarse aggregates to the skeleton network is analyzed from four perspectives: total contact force, vertical work, contact number, and effective coordination number. The aggregates of 19–26.5 and 4.75–9.5 mm constitute the main body of the load-transfer path and play a major role in bearing and transmitting the load in the skeleton network. [ABSTRACT FROM AUTHOR]

The heating temperature field of asphalt pavement is a key factor affecting the quality of pavement heat-in-place recycling (HIR). Using the heat transfer characteristics of HIR, a three-dimensional heat transfer model was simplified into a one-dimensional heat transfer model along the depth direction. A temperature sensor was installed on the site to monitor the temperature change of the asphalt pavement at different depths under different heating powers, and the actual temperature and heat transfer model were highly compatible. Through this model, the influence of heater running speed and heater heat flux density on the temperature field of the asphalt pavement heated by infrared radiation (IR) was calculated by the finite differential method, and an optimal combination of heating is proposed. In accordance with construction continuity and minimum energy consumption principles, at the 3.0–3.5 m/min recommended running speed of the heating machine, the asphalt at a depth of 4 cm satisfied the temperature demand, but the asphalt on the road surface was prone to heat aging. The heating effect of the constant temperature variable power heating (CTVP) is ideal, but the continuous change in heating power increases the difficulty of construction. Constant temperature discrete power heating (CTDP) divides the ideal heat flux density curve into several stages according to the length of the heating plate in the heater, increasing the feasibility of constant temperature heating in engineering and reducing energy consumption. The mileage of roads in some countries has basically satisfied the needs of national development, and the research focus of road workers has gradually shifted from building new roads to the renovation and maintenance of existing roads. In order to meet the purposes of convenient transportation and environmental protection at the same time, construction optimization must be carried out in the process of road renovation and maintenance to ensure that energy is not wasted during the construction process, and the relevant requirements of construction specifications are met. At present, high proportion of paved roads throughout the world have asphalt pavement. HIR has gradually become a popular maintenance method in order to save resources. In this method, the heating temperature field of the original asphalt pavement plays a key role in the construction quality, and the temperature field is affected by many factors, such as the running speed of the heater and the heat flux density of the heater during the heating process. This study mainly considers the foregoing two factors, combined with the actual situation of the project, in order to find a heating method with excellent heating effects and simple construction. The heating effect of the pavement is further optimized, improving the quality of the project, while saving energy and reducing the project cost. [ABSTRACT FROM AUTHOR]