With the rapid increase in traffic volume and heavy-duty vehicles, rutting has become one of the most serious problems threatening the service quality and life of asphalt pavement. High-modulus asphalt concrete is a promising method to overcome this problem, contributing to the sustainable development of asphalt pavement. In this study, a new composite high-modulus agent (CHMA)-modified asphalt binder and mixture were prepared, and their dynamic mechanical characteristics were investigated by the dynamic shear rheometer, dynamic modulus test, wheel tracking test, frequency sweep test at a constant height (FSCH), and repeated shear test at a constant height (RSCH) to comprehensively evaluate its high-temperature stability. Test results showed that the rheological property of the CHMA-modified asphalt binder was similar to that of low-graded asphalt binder, implying that it had a strong potential in resisting deformation. The dynamic modulus of AC-20(CHMA) was 19,568 MPa at 15 °C and 10 Hz condition, meeting the requirement for the high-modulus asphalt mixture (higher than 14,000 MPa). The dynamic stability of AC-20(CHMA) was 8094 times/mm, lower than that of AC-20(20#), but remarkably higher than that of AC-20(SBS). AC-20(20#) and AC-20(CHMA) both showed strong shear resistance according to the FSCH test results. Under the repeated shear loadings, the growth rate of the shear strain increased rapidly in the primary stage, and then slowed down gradually, finally reaching a constant growth rate. The shear slope of AC-20(CHMA) was between that of AC-20(20#) and AC-20(SBS), demonstrating that its resistance to repeated shear loadings was superior to AC-20(SBS), although slightly weaker than AC-20(20#). The findings in this study provide references for alleviating rutting problems and improving the lifespan of asphalt pavement.

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.

Improving the high-temperature stability and water damage resistance of asphalt pavements has always been a priority. This study proposed a composite high modulus modifier with rock asphalt and nanopolymer as main materials (HRMA) to prepare the high modulus asphalt mixture for their excellent rutting resistance. Moreover, its modification effect and modification mechanism were studied. The effect of HRMA content on the rheological performance of asphalt was investigated using Brookfield rotational viscosity, dynamic shear rheometers (DSR), and bending beam rheometers (BBR). Their modification mechanisms were revealed by Fourier Transformation Infrared Spectroscopy (FTIR). Besides, the properties of the mixtures were studied in various laboratory tests and compared with the 90# asphalt mixture and SBS asphalt mixture. Some of these included the rutting test, the bending test, the Marshall immersion test, and the freeze-thaw indirect tension test. The results indicated that with the increase of HRMA content, the deformation resistance of the asphalt mixture under high-temperature conditions was significantly improved, and the temperature sensitivity was changed. However, the crack resistance of its asphalt mixtures under low temperature was reduced due to the lower ductility of HRMA-modified asphalt. The recommended HRMA content was 21.8% of the asphalt, combining performance and construction cost.

Full-depth reclamation with Portland cement (FDR-PC) is a pavement rehabilitation technology that has garnered significant attention and research interest due to its ability to fully utilize existing pavement materials in situ and address deep structural issues within the pavement. This paper evaluates the advantages of FDR-PC in terms of carbon emission compared to traditional asphalt pavement rehabilitation technologies. Firstly, under the same service life conditions, the structural configurations of asphalt pavements were designed using 3D-Move Analysis for three different technologies: removal and reconstruction, cold central plant recycling, and FDR-PC. Subsequently, carbon emission models were established based on the life cycle assessment (LCA) method and the construction processes, allowing for a comparison of carbon emissions and energy consumption among the three technologies. Finally, a sensitivity analysis was conducted to assess the impact of various factors on carbon emissions during the FDR-PC construction process. The results indicate that in terms of carbon emissions from the pavement base layer, FDR-PC accounts for 92% and 90% of those produced by removal and reconstruction and cold central plant recycling, respectively, while its energy consumption is 60% and 70% of the latter two technologies. Notably, during the transportation phase, FDR-PC demonstrates carbon emissions and energy consumption levels at merely 4% each compared to conventional removal and reconstruction, and 6% each relative to cold central plant recycling. The sensitivity analysis further reveals that the cement content is the most influential factor affecting the carbon emissions of FDR-PC.

Full-depth reclamation with Portland cement (FDR-PC) is a promising technology in modern pavement engineering due to its capability of achieving deep-level treatment of pavement base layer distresses. This study aimed to optimize the material performance of FDR-PC materials while considering their environmental impact, developing a multi-objective optimization model to comprehensively evaluate and optimize these aspects. Laboratory tests were first conducted to investigate the effects of reclaimed asphalt pavement (RAP) content and cement content on 7-day unconfined compressive strength (UCS), indirect tensile strength (ITS), and relative compressive strength (RCS) after freeze-thaw cycles. A comprehensive performance evaluation function was established based on these key indicators. Subsequently, carbon emission and energy consumption models for FDR-PC were developed using life cycle assessment (LCA), which together formed an environmental impact function. The non-dominated sorting genetic algorithm II (NSGA-II) was employed to perform multi-objective optimization of the FDR-PC mix design and obtain the Pareto front. The technique for order of preference by similarity to ideal solution (TOPSIS) was then used to identify optimal parameter combinations under various objective weighting scenarios. Results revealed a significant negative correlation between material performance and environmental impact. The parameter combinations corresponding to the non-dominated solutions were mainly concentrated in cement content ranging from 4.8% to 6.0% and RAP content from 20% to 34%. Parameter combinations corresponding to high material performance were found in regions with RAP content below 20%, which also corresponded to high environmental impact. According to the TOPSIS analysis, the optimal mix under a performance-priority strategy consists of 6.0% cement and 5% RAP; the environmentally preferred mix recommends 4.6% cement and 32% RAP; and a balanced compromise suggests 5.2% cement and 27% RAP.