Transition zones in high-speed railways suffer from abrupt stiffness variations that induce irregular dynamic responses and accelerate infrastructure deterioration. This study presents a surrogate-assisted multi-objective optimization framework that combines finite element (FE) simulations, a neural network-based surrogate model, and the NSGA-II algorithm to address this challenge. A validated 3D FE model of prefabricated epoxy asphalt cured track beds (PEACT) was used to generate 341 layout scenarios covering 13 response parameters. These data were used to train a neural network, which served as a static surrogate predictor for evaluating layout performance during the optimization process. The results show that module layout has a limited effect on peak responses but significantly improves smoothness, with three categories of optimal configurations identified. Compared with direct FE-based optimization, the proposed framework achieves substantial computational efficiency and provides data-driven design guidance for PEACT transition zones. This framework exemplifies the potential of hybrid data-simulation approaches to enhance adaptive and efficient railway infrastructure design.

Adequate runway friction capacity during aircraft landing is crucial for flight safety. Accurately evaluating skid resistance under realistic service conditions remains a key challenge for maintaining flight safety. This study proposes a comprehensive skid resistance evaluation method that integrates laboratory testing with finite element simulation. A refined tire-pavement-fluid coupled model was developed, incorporating measured and series-generated worn texture data as key geometric boundary conditions in numerical analysis. The coupled effects of runway texture state, tire kinematics, and water film thickness on skid resistance were systematically investigated. Results suggest that runway macrotexture plays a vital role in maintaining skid resistance, with Stone Mastic Asphalt (SMA) mixtures providing superior skid resistance compared to Asphalt Concrete (AC) mixtures. As runway wear progresses, the combined influence of high speed and thick water films significantly increases the risk of hydroplaning and extends braking distance. This study highlights the significant effects of speed, water film thickness, and texture evolution on runway friction, offering theoretical guidance for material selection and safety evaluation of airport pavements.

Bitumen aging leads to increased brittleness and reduced flexibility, which significantly compromises the durability and long-term performance of pavements. This study investigates the potential of metal-organic frameworks (MOFs) as antiaging additives for bitumen, with an emphasis on their porous structures and selective adsorption behavior. Three representative MOFs, namely Metal-Organic Framework-5 (MOF-5), Zeolitic Imidazolate Framework-67 (ZIF-67), and Universitetet i Oslo-66 (UiO-66), were synthesized and characterized by scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. Their performance was compared with that of carbon nanotubes, which served as a conventional nanomaterial benchmark. The influence of these materials on the physical and chemical properties of bitumen was evaluated through viscosity measurements, Fourier-transform infrared analysis, and standardized aging tests. The results demonstrate that MOF-modified bitumen exhibits improved high-temperature flowability and substantial suppression of carbonyl and sulfoxide formation during oxidative aging. Among the tested materials, ZIF-67 provided the most pronounced antiaging effect, whereas carbon nanotubes primarily increased viscosity but were less effective in mitigating oxidative degradation. Three potential inhibition pathways, including inert gas oxidation blocking, reductive gas-induced reverse aging, and targeted adsorption combined with catalytic degradation, are proposed to explain the observed antiaging behavior. These findings indicate that metal-organic frameworks, particularly ZIF-67, are promising and sustainable modifiers for extending the service life of asphalt pavements. Future work will include long-term field validation and further elucidation of the molecular mechanisms underlying MOF-induced antiaging effects.

The antioxidant qualities of phenolic chemicals found in asphalt have drawn a lot of attention. By comparing theoretical calculations with experimental results, we evaluate the applicability of various antioxidant indices for assessing the efficacy of phenolic antiaging compounds in asphalt and unveil the antiaging mechanism of phenolic antioxidants in asphalt. By analyzing the correlation between oxygen radical absorbance capacity values and asphalt experimental results as well as the correlation between bond dissociation energy (BDE) and asphalt experimental results, it can be observed that the antioxidant mechanism of phenolic compounds in asphalt aligns with the hydrogen atom transfer (HAT) mechanism. In contrast, ferric reducing antioxidant power values, vertical ionization potential, electronegativity (chi), chemical hardness (eta), and electrophilicity index (omega) show no correlation with any asphalt experimental results, indicating that the antioxidant mechanism of phenolic compounds in asphalt is not based on the single electron transfer (SET) mechanism. This suggests that the antioxidant mechanism of phenolic antioxidants for asphalt is not the HAT mechanism but rather the SET mechanism, related to the phenolic hydroxyl content, the arrangement of hydroxyls in the ortho-dihydroxy conformation and BDE values of the phenolic O & horbar; H bond. These results indicate that enhancing the antioxidant activity of phenolic antioxidants may be achieved by reducing the BDE of the phenolic O & horbar; H bond, modifying the arrangement of hydroxyls, and increasing the phenolic hydroxyl group content.

This study employs the probability density function of the Weibull distribution to model the fracture energy damage density derived from force-displacement curves in semi-circular bending (SCB) tests of epoxy asphalt mixtures containing crumb rubber (CR). Key Weibull parameters-beta and eta-along with derived indices (IBS, CBS, Entropy, and Weibull(CRI)), were analyzed to evaluate crack resistance across varying CR contents, temperatures, and loading rates. The results indicate that increased CR content enhances ductility and fracture energy but reduces stiffness, while higher temperatures promote viscoelasticity and decrease failure load. The shape parameter beta reflects failure mechanisms, with higher values indicating brittleness. Whereas, the scale parameter eta correlates with damage propagation and toughness. A critical transition in mechanical behavior occurs at 4 % CR, characterized by a shift from an aggregate-dominated to a rubber-dominated response. Compared to conventional indicators, the Weibull-based fracture indices are more sensitive to variations in material composition and loading conditions. Correlation analysis shows that eta and Weibull(CRI) exhibit strong positive correlations (r > 0.94) with toughness indices (TI, CRI, CRIpre), confirming their reliability as indicators of crack resistance. In contrast, beta and IBS correlate strongly with stiffness-related parameters but negatively with flexibility metrics. Entropy moderately relates to toughness variability, while CBS shows weak predictive utility. This study establishes eta and Weibull(CRI) as robust indicators for evaluating fracture performance, providing a quantitative framework for optimizing rubber-modified asphalt mixtures under diverse service conditions.

Conventional asphalt binder undergoes rapid thermal oxidative aging during construction, which accelerates performance deterioration and reduces the environmental resistance of asphalt binders. To address this challenge, this study investigates five types of lignin, including alkali lignin, dealkalized lignin, sodium lignosulfonate, calcium lignosulfonate and enzymatic lignin (EL), as bio-based modifiers to enhance the aging resistance of asphalt binders. The relationships between the physicochemical characteristics of lignin and the performance of modified binders were thoroughly examined using dynamic shear rheometer (DSR), bending beam rheometer (BBR), gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR). The results show that EL exhibits the most effective anti-aging performance due to its low molecular weight, high phenolic hydroxyl content and superior dispersibility. FTIR and GPC analyses confirm that EL suppresses carbonyl and sulfoxide formation and limits molecular weight growth through radical scavenging and sacrificial degradation mechanisms. Moreover, 1H NMR results reveal that EL helps preserve molecular integrity by reducing chain scission and oxidation. This study clarifies the anti-aging mechanism of lignin-modified asphalt and provides a theoretical foundation for developing high-performance and sustainable bio-based binders.

The increasing number of heavy aircraft operations continually challenges the skid-resistance performance of airport pavements. Epoxy-asphalt mixtures, renowned for their superior mechanical and durability characteristics, have therefore been adopted widely in runway surfacing. Grounded in the theory of abrasion difference, basalt was combined with steel-slag and limestone aggregates to fabricate six Stone Matrix Asphalt (SMA) at graduated blending ratios. Phase composition was elucidated by X-ray diffraction (XRD), whereas microtopography and polymer functional groups were examined via scanning-electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR), respectively. The accelerated pavement testing (APT) device (60 degrees C, 2.0 MPa) applied accelerated loading to replicate in-service deterioration. Macroscopic and microscopic skid-resistance indicators-including British Pendulum Number (BPN), Estimated Texture Depth (ETD), Mean Profile Depth (MPD), and profilometric roughness parameters Ra and Rq-were monitored throughout conditioning. When using aggregate proportions with different abrasion resistance, wear is minimized and high surface roughness is maintained by continuously creating new surface textures; however, the addition of more than 50 % limestone reduces the long-term skid resistance of the surface. The investigation shows that the pronounced hardness gradient among basalt, steel slag, and limestone perpetually regenerates micro-/macro-texture, mitigating wear and sustaining high roughness indices over prolonged trafficking; abrasion difference design of steel slag, limestone, and basalt can satisfy the long-term skid resistance of mixed surfaces at high tire pressures.

Polyphosphoric acid (PPA)-modified asphalt provides cost-effectiveness and performance advantages, making it well-suited for stone mastic asphalt (SMA) mixtures. However, the performance and interactions of the modified asphalt mastic in the mixture require further investigation. This study investigates the wide-temperature rheological properties and interactions of PPA-modified asphalt mastics with a high filler-to-binder ratio, considering asphalt source (Shell 70# and DH 70#), fiber type (lignin fibers (LF) and basalt fibers (BF)). The rheological characteristics were examined using a dynamic shear rheometer, and the interactions in the PPA-asphalt-fillerfiber system were analyzed using Cole-Cole, Han, and Van Gurp-Palmen (vGP) plots. Mechanisms of PPA and fiber interaction were explored through microscopy and infrared spectroscopy. The results showed that PPA forms a strongly modified mastic system with DH 70# (asphaltene content 20.7%). The Jnr3.2 decreases by 43.6%, indicating improvement in high-temperature performance. In contrast, Shell 70# exhibits only weak modification; its Jnr3.2 even increases by 2.7%. PPA improves the fatigue life of asphalt mastic, particularly at low-strain. BF further enhances the fatigue life across the entire-strain. However, LF exhibits a positive effect only in the strongly modified system. Meanwhile, fibers (particularly BF) reduce the low-temperature stress relaxation capacity. In addition, PPA improves the compatibility of the asphalt-filler system. However, the fibers fail to provide further benefits and instead intensify high-temperature heterogeneity in weakly modified system. Esterification reactions may occur between PPA and LF. However, PPA has reacted with the asphalt binder. As a result, system interactions are dominated by physical adsorption, ultimately leading to heterogeneous structure.

This study investigates the effects of polyester fiber length and binder type (70-penetration, SBS-modified, and epoxy-modified asphalt) on the fracture behavior of asphalt concrete. Semicircular bending (SCB) tests integrated with acoustic emission (AE) monitoring, Weibull fitting, and K-means clustering were used to evaluate cracking mechanisms. Results indicated that 6 mm fibers optimized AC-13 mixture performance. In SBS-modified mixtures, fibers enhanced toughness, increasing the post-peak fracture energy ratio from 48.52% to 58.34%. Conversely, in epoxy-modified mixtures, fibers improved pre-peak crack resistance, raising pre-peak fracture energy and tensile strength by 64.59% and 20.26%, respectively. Weibull and cluster analyses confirmed that fiber bridging and pull-out delayed crack propagation by promoting cohesive failure. The proposed SCB-AE framework provides quantitative guidance for optimizing fiber parameters to enhance pavement durability.

Long term service of cement concrete pavement panels in civil airports often leads in surface degradation and other diseases caused by freeze-thaw cycles. However, conventional overlay repair materials typically exhibit insufficient low-temperature toughness. To address this issue, this study proposes a cold-mixed multi-component reactive asphalt material. Mercury intrusion porosimetry (MIP) was employed to characterize the pore structure of two cold-mixed multi-component reactive asphalt mixtures with varying polyester fiber contents. The results reveal a significant increase in pores ranging from 5000 to 30,000 nm after freeze-thaw cycling. The incorporation of polyester fibers enhances the water stability of the mixture. Furthermore, macroscopic freeze-thaw splitting tests confirm the superior freeze-thaw resistance of polyester fiber-modified cold-mixed multi-component reactive asphalt mixtures.

Behaviors of aggregate skeletons are of critical importance on the performance of asphalt mixture. This study utilizes discrete element modeling (DEM) to assess the influence of crumb rubber (CR) content on the mesoscopic mechanical properties of aggregate skeletons in rubberized epoxy asphalt mixtures. Four virtual specimens with varying CR content were subjected to DEM-based indirect tensile tests to evaluate force chain patterns, contact force properties, and fabric anisotropy. DEM simulations revealed that vertical force chains are primarily pressure-driven, contrasting with the tensile forces in the horizontal direction, which induce central cracking. The presence of CR particles mitigates contact forces between aggregates, impacting the variability of contact forces within the skeleton structure. Notably, a 4% CR content significantly alters these contact characteristics. Additionally, CR particles were observed to regulate the spatial distribution and fabric anisotropy of contact properties, promoting a more uniform contact distribution across the rigid-flexible hybrid skeleton structure with increased CR content. After loading, the principal axis direction of strong contacts aligns near 90 degrees. In conclusion, this research delineates the pivotal role of rubber particles in modulating the mesoscopic mechanical contact properties of epoxy asphalt mixtures, presenting a novel framework for optimizing CR content to enhance the mechanical performance of asphalt mixtures.

Polyphosphoric acid (PPA), a chemical modifier widely used in petroleum asphalt, results in significant performance improvements. However, its effectiveness for modified emulsified asphalt has not yet been thoroughly verified. This study aims to investigate the emulsification properties, rheological characteristics, compatibility, and modification mechanisms of PPA-modified emulsified asphalt and validate the feasibility of applying PPA for modification. Initially, PPA-modified emulsified asphalt was prepared at different dosages (0%, 0.5%, 1.0%, 1.5%, and 2.0%), and its emulsification characteristics, including evaporation residue properties and storage stability, were evaluated. Subsequently, the rheological performance and compatibility of PPA-modified emulsified asphalt at various temperatures were evaluated using a dynamic shear rheometer. Finally, Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM) were utilized to investigate the effects of PPA modification on the chemical composition and microscopic characteristics of emulsified asphalt. The results indicated that, with increasing PPA dosage, the softening point of modified emulsified asphalt initially decreased and then increased, while penetration and ductility first increased and then decreased, accompanied by reduced storage stability. Furthermore, PPA modification can enhance the high-temperature stability, fatigue properties, and low-temperature performance of emulsified asphalt, but the effectiveness depended on the dosage of PPA. Specifically, optimal compatibility of modified emulsified asphalt was achieved at a PPA dosage of 1.0%. Notably, PPA underwent hydrolysis within the emulsified asphalt system, leading to modification mechanisms distinct from those observed in base asphalt modification. At a PPA dosage of 1.0%, asphalt particles within the emulsified asphalt exhibited the most uniform distribution. Conversely, excessive PPA dosage (e.g., 2.0%) caused significant particle aggregation, consequently weakening the modification effect.

The application of epoxy asphalt presents a promising solution for improving the durability and sustainability of recycled asphalt mixtures with high reclaimed asphalt pavement (RAP) content. The degree of blending (DOB) between virgin and aged asphalt binders serves as a critical indicator of epoxy recycled asphalt mixtures (ERAM) and directly affects their mechanical performance. This study aims to investigate the influence of DOB on the fatigue performance of ERAM and to optimize the mixing process for enhanced fatigue resistance. An orthogonal experimental design was adopted to evaluate the effects of preheating temperature, mixing temperature, and mixing time on the macroscopic properties. Semi-circular bending (SCB) and repeated SCB (R-SCB) tests were conducted to assess cracking and fatigue resistance, respectively. Additionally, DOB was quantitatively analyzed at the microscale using energy-dispersive spectroscopy (EDS) with nano-TiO2 powder and nano-clay tracers. Results showed that the mixture achieves optimal overall performance at a mixing temperature of 170 degrees C and a mixing time of 120 s. EDS results and regression analysis revealed that increasing mixing temperature and time effectively improved DOB, peaking at 81 %, while a significant negative linear correlation was observed between DOB and fatigue performance. This is attributed to the reduction in effective epoxy content within the mixture as DOB increases, thereby compromising fatigue resistance, which highlights the necessity of optimizing mixing parameters to balance the strength and durability of ERAM. This study contributes to the advancement of sustainable pavement materials.

Using epoxy resins to recover the properties of aged binders offers an effective way to realise high-content recycling of reclaimed asphalt pavement (RAP), while its performance is expected to be further enhanced. When combining epoxy recycling technology with styrene-butadiene-styrene (SBS)/crumb rubber (CR) composite modified asphalt, the simultaneous recycling of both waste tires and aged binders can be achieved. This study aims to characterise the performance of epoxy-recycled asphalt (ERA) modified by SBS/CR with different aged binder contents, including tensile properties, low-temperature performance, thermal stability, fatigue resistance, and microscopic morphology. Additionally, its viscoelastic behaviours were analysed by constructing master curves using a novel Generalized Logistic Sigmoidal (GLS) model. The results indicate that the tensile properties and thermal stability of SBS/CR ERA with 80% aged binders, as well as the low-temperature performance and fatigue resistance of those with 60% aged binders, are superior to unmodified virgin epoxy asphalt. SBS/CR ERA displays great elastic deformability and reduced temperature susceptibility, with all phase angles below 45 degrees, attributed to the strong network structures. Overall, SBS/CR modification provides a feasible solution for recycling high percentages of aged binders with enhanced mechanical and rheological properties. It will contribute to 'epoxy recycling' systems and sustainable pavements.

The aging phenomenon of asphalt binder is a critical factor that observably affects pavement durability. Utilizing the desulfurization process to develop desulfurized rubber-modified asphalt (DRMA) has emerged as an effective method for improving the aging resistance of asphalt. This study systematically evaluated the rheological properties of rubber-modified asphalt (RMA) and DRMA, before and after both thermo-oxidative and pressure aging. The swelling behavior of crumb rubber (CR) and alterations in the chemical structure of asphalt binder were also detected to elucidate the aging mechanism. Both the deformation resistance and fatigue performance of RMA and DRMA were enhanced after thermo-oxidative aging, which is attributed to the swelling of undissolved rubber particles, reinforcing the internal network structure in asphalt binder. Conversely, pressure aging was characterized by rubber degradation, leading predominantly to the breakdown of the network structure, which in turn resulted in deteriorated rheological properties. When subjected to equivalent aging conditions, DRMA consistently demonstrated superior rheological performance compared to RMA. This superiority was primarily due to the improved compatibility of desulfurized rubber with asphalt, which facilitated the formation of a more uniform and robust internal network structure. Furthermore, the greater integration of carbon black and aging inhibitors into the asphalt from the desulfurized rubber further enhanced the resistance to aging.

The use of epoxy resin(EP)to prepare epoxy recycled asphalt mixture can achieve the reuse of 100%reclaimed asphalt pavement(RAP).However,the high stiffness and brittleness of epoxy resin result in insufficient crack resistance of mixture.To address the issue,dry-method styrene-butadiene-styrene(DSBS)and epoxy resin were mixed with aged asphalt to prepare SBS-modified epoxy reclaimed asphalt(SERA).The micro fusion characteristics and mechanical properties of SERA were evaluated,and the optimal DSBS dosage was determined based on various tests.The results show that adding DSBS can enable the tensile toughness and low-temperature performance of SERA with less EP content to reach or exceed the performance level of epoxy reclaimed asphalt(ERA)with higher EP content.At 30%EP content,the recommended dry-method SBS content is 9%;At 40%EP content,the recommended dry-method SBS content is 5%;When the EP content is 50%,the recommended dry-method SBS content is 7%.

The combination of epoxy asphalt and reclaimed asphalt pavement (RAP) provides a promising solution for realizing high-percentage RAP recycling. However, the epoxy-recycled mixture needs to be toughened to enhance its cracking resistance and its fracture behavior after toughening is not clear. This study aims to investigate the fracture characteristics of epoxy-recycled mixtures toughened by styrene-butadiene-styrene/ crumb rubber and core shell rubber (SBS/CR-CSR). Four mixtures with RAP contents of 30%, 45%, 60%, and 80% were designed, and their mechanical and fracture properties were evaluated through dynamic modulus tests and semi-circular bending (SCB) tests. Mesoscopic fracture behaviors were revealed though fracture surface analysis using image processing techniques. Results show that the SBS/CR-CSR toughening approach significantly improves the cracking resistance of recycled mixtures and delays crack propagation by enhancing postpeak energy absorption. The flexibility indexes (FI) of toughened epoxy-recycled mixtures with 30%, 45%, and 60% RAP are 14.28, 5.51, 4.49 times of the control group. Finally, the fracture surface recognition analysis provides a mesoscopic explanation for the brittle and ductile fracture mechanisms at various temperatures and RAP contents. These findings provide guidance for fracture mechanism interpretation and material design of epoxy-recycled mixtures, promoting the application of durable and sustainable asphalt pavements.

Carbon nanotubes (CNTs) modified epoxy mixture (CEMix) holds the potential to serve as piezoresistive materials for traffic load sensing, thereby contributing to the digitalization of road systems. This study aims to investigate the electrical (conductive and piezoresistive) and mechanical performance of CEMix from both experimental and modeling perspectives. A three-step micromechanics model was developed to describe the conductivity and piezoresistivity of CEMix, which was validated against experimental values obtained from compression tests at 0.7 MPa and 1.0 MPa. The stress compatibility of CEMix with the asphalt surface layer was evaluated using finite element modeling (FEM). Experimental results reveal that the gauge factor (GF) of CEMix exceeds 140 at CNTs volume fractions of 0.16 % and 0.26 %, while the modeled results present a relative error below 20.6 %. At a CNTs volume fraction of 0.21 %, the experimental GF surpasses 430; however, the model error increases to 44 %. The modeled conductivity of CEMix shows a relative error ranging from-0.8 % to 36.4 %. Moreover, CNTs significantly enhance the modulus of the epoxy mixture in the low-frequency (high- temperature) domain. The maximum tensile and shear stresses induced in the asphalt surface layer by embedded sensors made of CEMix are 7 % and 40 % higher compared to pavements without sensors, as determined by FEM. This study is anticipated to provide valuable insights for the design of piezoresistive materials intended for sensitive surface layers in the digital twin of road system.

To better understand the evolution of skid resistance on airport asphalt runways, this study investigates the longterm skid resistance durability of epoxy asphalt mixtures containing steel slag under high-temperature conditions. An indoor abrasion device was modified to simulate wear, applying a contact pressure of 1.5 MPa. The surface texture evolution and skid resistance degradation patterns under different steel slag contents were explored using indicators such as Mean Profile Depth (MPD), Bearing Area Ratio (Smr ), and British Pendulum Number (BPN). Additionally, the mechanisms of differential polishing were analyzed by examining the microstructure and mineral composition of the aggregates. The results indicate that the differences in mineral composition between steel slag and basalt lead to differential polishing during use, which enhances the long-term wear resistance of the asphalt mixture for airport runways. Under high temperature and pressure conditions, the epoxy asphalt mixture effectively maintains its structural integrity without significant rutting, making it suitable for airport runways. A steel slag content of 25-50 % performs well in terms of long-term skid resistance durability. This provides useful guidance for the skid resistance safety assessment of epoxy asphalt mixtures used in airport runways.