In order to investigate the self-healing behavior of asphalt binder at the molecule scale, the self-healing models of neat and aged asphalt binder with different damage degrees were established by introducing a vacuum pad between two layers filled with asphalt molecules. With this model, the self-healing process was simulated at various healing conditions to reveal the effects of oxidative aging, damage degree and healing temperature on the self-healing property. In addition, self-healing efficiency was evaluated using the indexes representative of the characteristics of different self-healing stages. Our results show that the oxidative aging weakened the stacked structure of the asphalt binder and increased the healing activation energy barrier. The increasing damage degree extended the distance for particles to travel, thus prolonging the time required for the crack interfaces contacting with each other. The elevated temperature improved the molecular mobility by supplying more energy to the molecular system. Furthermore, the self-healing process was evaluated quantitatively by the density variation at the crack closing stage and the diffusion coefficient at the intrinsic healing stage. The duration of each stage was influenced by the oxidative aging, damage degree and healing temperature. The findings in this paper are helpful to reveal and evaluate the self-healing property of asphalt binder.

Full-depth reclamation with Portland cement (FDR-PC) represents an innovative cold recycling technology for pavements, holding significant promise due to its capacity to reuse deteriorated pavement base layers. This paper investigates the key factors influencing the strength properties of FDR-PC. The results indicate that, compared to the static compaction method, the vibratory compaction method yields cold-recycled mixtures with higher maximum dry density and unconfined compressive strength (UCS). Increasing the cement content and base-to-surface ratio, extending the curing time, and raising the curing temperature all contribute to enhancing UCS. Furthermore, increasing the base-to-surface ratio and cement content enhances both indirect tensile strength and flexural strength. An approximate linear correlation exists between indirect tensile strength and UCS, as well as between flexural strength and UCS. The strength characteristics of FDR-PC were comprehensively characterized in this study, providing effective verification of its applicability.

Geosynthetic interlayer systems are effective techniques to control reflective cracking and have better waterproof performance in damaged asphalt pavements. The interlayer bonding performance is critical to its function. This research investigated the interfacial adhesive property and road performance of asphalt overlay with geotextile interlayer. First, shear damage energy characteristics of geotextile interlayer have been investigated by varying tack coat types (SBS-modified asphalt, virgin asphalt, and emulsified asphalt), application rates (0.3kg/m²1.2kg/m²), spraying times (12), upper mixture paving temperature (140°C180°C), service temperature (5°C45°C), and soaking time (0h96h). In addition, bending fatigue tests, rutting tests, and semicircular bending tests were carried out to evaluate the comprehensive road performance of the asphalt overlay. The results showed that the interface adhesive property of asphalt overlay with geotextile interlayer using SBS-modified asphalt is best when the application rate is 0.8kg/m². The higher paving temperature is beneficial for the geotextile interlayer adhesion performance when the SBS-modified asphalt is sprayed at one time, while the paving temperature has almost no effect when the SBS-modified asphalt is sprayed at two times. The geotextile interlayer adhesion performance is less affected by temperature and more affected by water immersion. Compared with the common asphalt overlay types, the asphalt overlay with geotextile interlayer using SBS-modified asphalt shows better overall performance.

The technology of SBS-modified asphalt has advanced significantly and is now widely used in pavement materials. However, compared to the current research that mainly focuses on the investigation of SBS and asphalt materials themselves, the influence of compatibilizers is often overlooked due to their minor composition. Particularly, the impact and mechanisms of compatibilizers’ curing processes and curing time on the performance of modified asphalt are still not well understood. This paper investigates the effects of curing time on the high-temperature, low-temperature, and aging properties of SBS-modified asphalt, using an SK-90A base asphalt and a Maleic Anhydride (MAH)-based compatibilizer, with curing times of 1 h, 3 h, 5 h, and 7 h. The results showed that extending the curing time from 1 to 7 h improved the high-temperature PG. The low-temperature PG improved after 3 h and stabilized, while the Softening Point increased continuously. Optimal overall performance, particularly for ductility and aging performance, was achieved at 5 h. Additionally, the molecular dynamics (MD) simulation was used to verify this process and explain the inherent mechanisms of the curing process. The results showed that when mixed with SBS-modified asphalt, compatibilizers reduced non-bond energy through non-covalent interactions, stabilizing, grafting, and dispersing the polymer molecules in the structure. As curing time increased, high-temperature performance improved, but the modified asphalt became harder, reducing internal adhesion and potentially suppressing low-temperature performance. The contribution of this paper is to propose an evaluation method combining experimental and MD simulation approaches to investigate the impact of compatibilizers and curing processes on the performance of modified asphalt. This study enhances the understanding of compatibilizers and curing mechanisms, providing a foundation for designing and evaluating new products in the future.

Recently calcium alginate has been successfully applied to encapsulate asphalt rejuvenator, which can protect asphalt rejuvenator from early leakage and release asphalt rejuvenator when triggered by specific factors such as cracks. The interfacial adhesion property of asphalt binder with calcium alginate carrier is of great importance to its actual performance. In this paper, the molecular model of the interface region between asphalt binder and calcium alginate was established, and molecular dynamics simulations were performed on it to investigate the molecular interaction at the interface region. By extracting and processing the data during the simulation process, the interfacial adhesion behavior was expounded using the spreading coefficient (S), permeation depth and permeation degree. Furthermore, the interfacial adhesion strength was evaluated by adopting the interfacial adhesion work. Results showed that the value of S was greater than 0, implying that asphalt binder could wet the surface of calcium alginate. Saturate had the highest value of permeation degree, followed by resin, aromatic and asphaltene. However, asphalt binder could not infiltrate into the interior of TiO₂, only accumulating and spreading on the surface of TiO₂. The interfacial adhesion work of unaged and aged asphalt binder to calcium alginate was −114.18 mJ/m² and −186.37 mJ/m², respectively, similar to that of asphalt–aggregate interface. The van der Waals interactions contributed the most to the formation of the interfacial adhesion strength. In addition, a certain degree aging of asphalt binder and addition of titanium dioxide in the calcium alginate carrier were helpful to enhance the interfacial adhesion strength.