In actual service, asphalt pavement is subjected to freeze–thaw cycles and ultraviolet radiation (UV) over the long term, which can easily lead to mixture aging, enhanced brittleness, and structural damage, thereby reducing pavement durability. This study focuses on the influence of freeze–thaw cycles and ultraviolet aging on the performance of recycled asphalt mixtures. Systematic indoor road performance tests were carried out, and a fatigue prediction model was established to explore the comprehensive effects of recycled asphalt pavement (RAP) content, environmental action (ultraviolet radiation + freeze–thaw cycle), and other factors on the performance of recycled asphalt mixtures. The results show that the high-temperature stability of recycled asphalt mixtures decreases with the increase in environmental action days, while higher RAP content contributes to better high-temperature stability. The higher the proportion of old materials, the more significant the environmental impact on the mixture; both the flexural tensile strain and flexural tensile strength decrease with the increase in environmental action time. When the RAP content increased from 30% to 50%, the bending strain continued to decline. With the extension of environmental action days, the decrease in the immersion Marshall residual stability and the freeze–thaw splitting strength became more pronounced. Although the increase in RAP content can improve the forming stability, the residual stability decreases, and the freeze–thaw splitting strength is lower than that before the freeze–thaw. Based on the fatigue test results, a fatigue life prediction model with RAP content and freeze–thaw cycles as independent variables was constructed using the multiple nonlinear regression method. Verification shows that the established prediction model is basically consistent with the change trend of the test data. The research results provide a theoretical basis and optimization strategy for the performance improvement and engineering application of recycled asphalt materials.

To improve the aging resistance and prolong the service life of asphalt pavement, this study utilized modified multi-walled carbon nanotubes (MWCNTs) functionalized with carboxyl (MWCNTs-COOH), hydroxyl (MWCNTs-OH), and amino (MWCNTs-NH2) groups. These nanotubes were incorporated into SBS-modified asphalt at a concentration of 1%. The study sought to examine the impact of MWCNTs and their functional groups on asphalt’s rheological and anti-aging characteristics, alongside exploring their modification mechanisms. The findings indicated that rheological tests showed that MWCNTs/SBS composite-modified asphalt, particularly MWCNTs-OH/SBS, exhibited remarkable resistance to hightemperature deformation, a crucial characteristic for asphalt performance in hot climates. Nevertheless, it is important to note that the addition of MWCNTs led to an increase in asphalt’s creep strength and creep rate, which could potentially reduce its resistance to low-temperature cracking. However, the covalent functionalization of MWCNTs mitigated these adverse effects on low-temperature performance. Moreover, the inclusion of MWCNTs in asphalt served as a barrier, impeding the penetration of oxygen molecules and ultraviolet radiation into the asphalt matrix. This proved to be an effective means of inhibiting the aging process, a critical factor in extending the service life of asphalt pavement. Among the different formulations of MWCNTs modified asphalt, the MWCNTs-OH/SBS composite-modified asphalt exhibited notably effective anti-aging properties. Both rheological and anti-aging evaluations demonstrated that hydroxyl functional groups played a pivotal role in enhancing performance, chiefly by fostering interactions with asphalt molecules.

To reveal the long-term anti-aging mechanisms of rubber–plastic elastomer-modified asphalt in complex service environments and overcome the inherent defects of single polymer modifiers—namely their susceptibility to degradation or phase separation—this study prepared styrene-butadiene-styrene (SBS), low Mooney rubber (LMMR), and low-density polyethylene (LDPE)-modified asphalts. Simultaneously, an LMMR-LDPE rubber–plastic thermoplastic elastomer (TPE) was fabricated utilizing twin-screw extrusion technology and subsequently used to prepare a composite-modified asphalt. Three aging protocols were simulated: short-term thermo-oxidative aging (RTFOT), long-term pressure aging (PAV), and ultraviolet light aging (UV). A multi-scale quantitative characterization was conducted using a dynamic shear rheometer, Fourier transform infrared spectroscopy, and atomic force microscopy to evaluate the rutting factor, carbonyl index, and surface microroughness of each system before and after aging. The experimental results indicate that the coupled effect of long-term stress and thermal oxidation causes the most severe damage to the colloidal structure of modified asphalt. Conventional SBS-modified asphalt, due to its abundance of unsaturated double bonds, exhibits a sharp increase in the carbonyl index and aging index of the rutting factor after aging, making it highly susceptible to oxidative chain scission. Although LDPE-modified asphalt possesses chemical inertness, it is prone to crystalline phase separation under aging conditions, resulting in a microroughness distortion rate of up to 86.36%. In contrast, the LMMR-LDPE composite system, leveraging the high chemical stability of the saturated aliphatic carbon chain and the flexibility-enhancing and crystallization-inhibiting effects of LMMR, effectively reduces active oxidation sites and improves interfacial compatibility. This composite system exhibits the lowest carbonyl increment and rheological attenuation under all aging conditions, while effectively inhibiting the free migration and agglomeration of macromolecular components. The LMMR-LDPE composite modification technology effectively overcomes the inherent drawbacks of single polymers, such as susceptibility to degradation or segregation, demonstrating excellent long-term macroscopic rheological stability and microscopic phase morphology anti-aging capability. The present findings provide laboratory-scale mechanistic support for the design of durable rubber–plastic-modified asphalt systems, while further pilot-scale, economic, and field validation is still required before practical engineering application can be fully assessed.

Low-activity copper tailings (CTs) were mechanochemically activated and used to develop a copper tailings–slag–metakaolin grouting material (CSM). Mechanical grinding and Na₂SO₄ addition were first optimized, after which single-factor experiments and response surface methodology were used to evaluate the effects of the water-to-solid ratio, alkali activator dosage, and MCCT content on slurry properties and compressive strength. Grinding for 40 min with 3 wt% Na₂SO₄ relative to the dry CT mass produced the highest activity index of 84.5%. The optimized CSM mixture had a water-to-solid ratio of 0.69, an alkali activator dosage of 6.7 wt%, and an MCCT content of 35.5 wt% of the dry solid precursor. Validation experiments yielded a fluidity of 235 mm, a bleeding rate of 2.8%, a setting time of 165 min, and a 28 d compressive strength of 8.62 MPa, with prediction errors below 5%. Microstructural characterization indicated that mechanochemical activation refined the CT particles, increased their structural disorder, and contributed to the formation of Ca–Si–Al–O-rich binding phases and AFt-like crystals in the hardened matrix. Within the defined preliminary material-level system boundary, the embodied energy, greenhouse gas emissions, and material cost of CSM were estimated to be 67.86%, 82.87%, and 27.28% lower, respectively, than those of the 1 kg ordinary Portland cement (OPC) binder benchmark. These results indicate the potential of CSM as a filling and consolidation grout with reduced material-level environmental burdens and cost within the adopted assessment boundary.

Conventional rubber–plastic modified asphalt often suffers from poor compatibility and thermal storage stability, which limits its engineering application. To address this issue, this study proposes a prefabricated nano-reinforced rubber–plastic thermoplastic elastomer (TPE) modification strategy. The specific objective was to comparatively investigate how different waste plastic matrices (HDPE, LDPE, and PP) and two representative nano-oxides (ZnO and TiO₂) affect the interfacial evolution, storage stability, rutting resistance, fatigue durability, and low-temperature cracking resistance of modified asphalt. The prefabricated nano-reinforced TPE modifier was incorporated into the base asphalt, and its storage stability, interface evolution and multi-scale rheological properties were evaluated. The results show that all modified binders exhibited good thermal storage stability, with softening point differences below 2.5 °C. The enhancement mechanism was mainly governed by physical blending, swelling adsorption, and interfacial synergistic interactions rather than the formation of new chemical functional groups. A clear synergistic matching relationship between plastic type and nanoparticle type was identified. LDPE-based systems showed better phase compatibility and fatigue/low-temperature performance, whereas HDPE-based systems were more favorable with respect to improvement of high-temperature rutting resistance. In addition, ZnO contributed more significantly to storage stability, rutting resistance, and fatigue resistance, while TiO₂ was more beneficial for low-temperature crack resistance. These findings provide new insight into the interfacial design of nano-reinforced rubber–plastic modified asphalt and offer guidance for performance-oriented and sustainable pavement materials.