Styrene–butadiene–styrene modified asphalt (SA) is widely used in pavement engineering, but its long-term durability is limited by thermo-oxidative and ultraviolet (UV) aging. Herein, lauric acid-intercalated layered double hydroxides (LA-LDHs) were prepared via a calcination–reconstruction strategy and optimized by response surface methodology to integrate phase-change thermal buffering with UV-reflective protection. The optimized LA-LDHs were incorporated into SA to obtain LA-LDHs modified SA (LLSA), and its aging resistance was evaluated through physical, rheological, thermo-optical, FTIR, and GPC analyses. The results showed that 6 wt% LLSA exhibited much lower aging sensitivity than SA after PAV aging. The softening-point change was reduced from 1.5 °C for SA to 1.0 °C for LLSA, and the rutting factor aging index was reduced from 1.61 to 1.25. Meanwhile, MSCR results showed that the elastic recovery at 3.2 kPa increased from 20.91% to 22.95%, while the non-recoverable creep compliance was limited to 3.56 kPa-¹ , indicating improved viscoelastic recovery and deformation resistance. Under simulated solar irradiation, LLSA exhibited an approximately 20% higher UV reflectance and a 3.4–4.5 °C lower peak surface temperature than SA, demonstrating the coupled UV-reflective and thermal-buffering effects of LA-LDHs. In addition, FTIR and GPC analyses confirmed that LLSA exhibited lower oxidative aging and molecular degradation than SA, as evidenced by reduced carbonyl and sulfoxide indices and a lower polydispersity index of 2.54 compared with 3.19 for aged SA. These results indicate that LA-LDHs enhance the aging resistance of SBS-modified asphalt through coupled thermal buffering, UV reflection, and suppression of molecular structural degradation.

Asphalt pavement maintenance faces challenges from crack propagation and material aging, prompting the exploration of innovative self-healing technologies. Traditional maintenance methods such as grouting and patching, are reactive and short-term. This study investigates the practical application of self-healing calcium alginate capsules in asphalt pavements to address performance degradation caused by traffic loads and environmental factors. The research team have developed an integrated production device for large-scale manufacturing of calcium alginate capsules. These capsules containing low-viscosity asphalt rejuvenator are incorporated into AC-13 asphalt mixtures and applied to test road section in Yongtai S213 Line, Fujian Province. Field tests demonstrate that the capsule-modified pavement met construction specifications, with compaction (97.8%), texture depth (0.80mm), and permeability (242ml/min) within acceptable ranges. Although the capsules slightly reduced mixture density, marshal stability and dynamic stability compared to conventional asphalt, all parameters complied with Chinese standards. The study validates the feasibility of calcium alginate capsules for self-healing asphalt pavements, highlighting their potential to extend service life through crack repair and aged asphalt regeneration. Challenges remain in optimizing production scalability and long-term durability for broader engineering applications.

Steel slag has the potential to be used as a high-quality aggregate, but its insufficient volume stability limits its large-scale application. Carbonation has been demonstrated to be an effective technology for removing f-CaO, but its influence on skid resistance remains insufficiently understood. The purpose of this study was to explore the mechanism by which carbonation affected the surface structure and skid resistance of steel slag. First, XRD, DTG, SEM, CT, LCSM and AIMS were used to investigate the effects of carbonation on the physicochemical properties and microtexture of steel slag aggregates. Subsequently, the skid resistance and selected engineering properties of carbonated steel slag asphalt mixtures were evaluated using TD, BPN, pavement-performance tests and a simplified carbon-balance analysis. The results showed that early carbonation promoted the conversion of f-CaO into aragonite, accompanied by the accumulation of aragonite-rich products on the aggregate surface and the formation of a rough interface. However, these aragonite-rich products were susceptible to fracture and detachment under abrasion, resulting in rapid attenuation of the skid-resistance response of the mixtures. By contrast, prolonged carbonation promoted the transformation of aragonite into stable calcite. This transformation reduced the average number of open pores by 89.8% and the aggregate expansion ratio by 75.5%. At the same time, the higher phase stability and improved physical retention of the blocky calcite-rich products enhanced microtexture durability. The improved durability increased the initial skid-resistance response by 17.9%, reduced its attenuation rate by 39.9%, and generated net carbon benefits within the defined simplified carbon-balance boundary. This study revealed the mechanism by which carbonation regulated the performance evolution of steel slag. The surface morphology and stability of steel slag were regulated by carbonation, enabling its conversion into a low-carbon, durable, skid-resistant, and wear-resistant road material.

As a fundamental component of the global transportation network, asphalt pavements inevitably release complex volatile organic compounds (VOCs) throughout their entire life cycle, posing persistent threat to ecosystems and human health while hindering cleaner production in sector. Owing to the extreme compositional complexity of asphalt VOC emissions, existing studies have largely focused on total emission control, often overlooking the dominant contribution of a small number of highly toxic components to overall risk. To address this limitation, this study proposes a risk-oriented selective suppression strategy. A multidimensional evaluation framework was established to identify key hazardous components, prioritizing isoprene, p-xylene, dimethyl disulfide, and methyl vinyl ketone as primary control targets. Subsequently, a low-emission asphalt material was developed using the high-surface-area metal–organic framework MIL-101 as a modifier to enable targeted adsorption of these characteristic pollutants. Multiscale molecular simulations reveal that the abundant unsaturated metal sites and unique pore environment of MIL-101 generate deep free-energy wells and pronounced diffusion barriers, endowing the material with higher adsorption affinity and stronger intracrystalline retention for selective capture of the target pollutants. Gas chromatography–mass spectrometry (GC–MS) experiments further validate the simulation predictions, demonstrating that MIL-101 significantly reduces emissions of the risk-dominant pollutants, Overall, this work integrates risk-oriented screening with mechanism-guided material design, providing an effective pathway for cleaner production of low-emission asphalt materials and the development of more sustainable transportation infrastructure.

The emergence of a novel crumb rubber (CR)/SBS-polymerized pellet has simplified the complex preparation process of composite-modified asphalt. However, the effectiveness of CR/SBS-polymerized pellets in improving asphalt performance has not been confirmed. This study mainly investigated the performance and reinforcement mechanism of polymerized pellet-modified asphalt. First, polymerized pellet-modified asphalt samples with different contents (10%, 20%, 30% and 40% of the asphalt mass) were prepared. Then, the physical properties, rheological behavior, thermal stability, and aging resistance of the pellet-modified asphalt samples were systematically evaluated, using both base asphalt and a commercially available styrene-butadiene-styrene triblock copolymer (SBS)-modified asphalt as control groups for comparison. Finally, the modification mechanism was explored through Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM). The findings demonstrated that the incorporation of polymerized pellets could effectively decrease the penetration, elevate the softening point, and enhance the viscosity of asphalt. In addition, the high- and low-temperature performance, as well as the aging resistance of the modified asphalt, were significantly improved. These enhancing effects became more pronounced with increasing modifier content. The performance of SBS-modified asphalt is between 20% pellets MA and 30% pellets MA. The pyrolysis temperature range of all asphalt samples is 220 °C~500 °C, and infrared spectroscopy indicated that CR/SBS pellet-modified asphalt is mainly a physical mixing process. This work provides a scientific basis for further engineering applications of CR/SBS pellets.

Steel slag, especially in its powder form, was regarded as a highly promising material for carbon sequestration. However, the carbonation characteristics and environmental benefits of steel slag aggregates remained unclear, primarily due to the complexity of their surface pore structure. This study investigated how carbonation altered the pore structure of steel slag aggregates and analyzed the resulting effects on the expansion behavior, interfacial adhesion, overall durability, and environmental performance of steel slag asphalt concrete. First, the carbonation process was evaluated by monitoring pH changes and Ca2+ precipitation under three distinct moisture conditions: water-deficient (10%), water-adequate (100%), and water-excess (1000%). Next, X-ray diffraction (XRD) and computed tomography (CT) were employed to quantitatively characterize the depth-dependent evolution of pore structure during carbonation. Subsequently, aggregate stability and pavement performance were assessed, and a predictive model for pore-induced expansion was developed. Finally, the environmental benefits of carbonated steel slag aggregates were quantified based on net CO2 emissions. Results demonstrated that a water-adequate environment promoted calcium precipitation via the HCO₃-/OH- balance, thereby enhancing carbonation efficiency. This yielded two key innovations: (1) a pore sealing rate exceeding 90%, which effectively stabilized the aggregate framework; and (2) the production of carbonized steel slag aggregates that achieved net carbon sequestration. The refined pore structure improved aggregate stability, reducing the expansion rate by 71.9% and enhancing pavement performance. In contrast, water-deficient and water-excess conditions disrupted the HCO₃-/OH-balance, impeded carbonation, and induced pore coarsening from sub-25 μm to over 85 μm, leading to significantly higher expansion and net CO2 emissions. Overall, the coupled evolution of pore architecture and functional performance elucidated the fundamental carbonation reaction mechanism of steel slag aggregates, providing a theoretical foundation for the optimized pre-treatment of high-quality steel slag aggregates in low-carbon pavement.

Induction heating-based functional ultra-thin friction layer (FUFL) for removing snow and ice was found severe aggregate spalling due to repeated induction heating. This study tried to reveal how induction heating affects FUFL's resistance to particle spalling through an originally developed assessment through computer image processing. Firstly, AC-5 asphalt mixtures incorporating steel slag and steel fibers were designed. Secondly, an abrasion-spalling accelerating device and an evaluation method based on image processing of MATLAB were proposed to assess the spalling level, reflecting changes of spalling level by measuring the change rate of the black pixel percentage. Finally, a quantitative analysis of how induction heating determines particle spalling degree by ice melting time dependence was performed. Results illustrated that steel slag can enhance the splitting strength, stability, interlayer shear strength, improve the induction heating rate and ice melting effect, but also exacerbate the particle spalling. The developed evaluation method was adequate in assessing aggregate spalling. Aggregate spalling degree of FUFL was positively correlated to the number of freeze-thaw cycles. It was found that the comprehensive road performance, induction heating performance, and spalling performance of FUFL could be optimally enhanced by adding 1% steel fibers.

Calcium alginate capsules encapsulating bitumen rejuvenator represent an extrinsic asphalt self-healing system characterized by high encapsulation efficiency and the capability for multiple, time-dependent releases of rejuvenator. The core rejuvenator content within these capsules is a critical determinant of their self-healing performance. This study determined and compared the rejuvenator content in calcium alginate capsules using three analytical techniques: solvent extraction, thermogravimetric analysis (TGA), and X-ray computed tomography (X-CT). Capsules were fabricated with various rejuvenator types and shell compositions. The efficiency and accuracy of these methods were systematically evaluated, and an improved TGA-based protocol was developed to address systematic errors present in conventional approaches. Results indicated that both the type of rejuvenator and the shell material density significantly influence core content. The solvent extraction method measured rejuvenator contents of 52.24 % in oil capsules, 27.34 % in aromatic rejuvenator capsules, and 47.61 % in oil capsules with nano-Fe3O4. The improved TGA method demonstrated superior accuracy and minimal error, whereas the X-CT method showed substantial discrepancies. Importantly, our findings establish that the improved TGA method is not only more user-friendly and less material-intensive than the extraction method, but also offers a more reliable and practical approach for quantitative assessment of capsule core content, outperforming the other techniques evaluated.

Reclaimed asphalt pavement (RAP) is widely incorporated into recycled asphalt mixtures to improve resource utilization and reduce environmental impacts. However, the aged binder introduced at high RAP contents significantly compromises cracking resistance. This study investigates the macro-meso fracture behavior of high-RAP asphalt mixtures by coupling fracture mechanics parameters with crack-path characterization. Semi-circular bending (SCB) tests were conducted on AC-13, AC-16, and SMA-13 mixtures containing 30%, 40%, and 50% RAP at temperatures of -15 degrees C, 0 degrees C, and 25 degrees C. Fracture energy, fracture toughness, cracking resistance index, and flexibility index were evaluated. An image segmentation approach was employed to identify crack propagation paths and quantify crack tortuosity and fractal dimension. The results indicate that increasing RAP content from 30% to 50% reduced fracture energy by up to 42% at -15 degrees C and caused a pronounced decline in crack tortuosity and fractal dimension. Temperature significantly influenced fracture behavior, with mixtures exhibiting brittle fracture at -15 degrees C and ductile fracture at 25 degrees C. Among all gradation types, SMA-13 demonstrated the highest cracking resistance, maintaining a flexibility index of 6.92 at 50% RAP, which remained comparable to that of AC-16 mixtures at 30% RAP. Furthermore, crack tortuosity and fractal dimension decreased by approximately 12-15% and 6-9%, respectively, indicating progressively simplified crack propagation paths and reduced energy dissipation capacity. The results reveal a strong consistency between macroscopic fracture performance and mesoscale crack-path characteristics. Aggregate skeleton interlock promotes crack deflection and energy dissipation, thereby alleviating RAP-induced embrittlement and improving the fracture resistance of recycled asphalt mixtures.

Using the layered double hydroxides (LDHs) as modifiers can enhance the UV aging resistance of bitumen. However, the poor compatibility between LDHs and bitumen limits the significant improvement of the UV aging resistance. To improve the compatibility and UV aging resistance of bitumen effectively, this study applied sodium 2,3-dihydroxynaphthalene-6-sulfonate (DSAS) to intercalate LDHs, synthesizing an efficient UV-blocking agent (DSAS-L). The results of the crystal structure, functional groups, microstructure, and UV-visible spectroscopy indicate that the DSAS has successfully intercalated into the LDHs layers. When DSAS and LDHs are mixed at a ratio of 1:1, DSAS-L has the highest mean UV absorbance (87 %) and the greatest UV-shielding performance. Zeta potential analysis revealed that DSAS-L significantly improved the micro-compatibility with bitumen, and that zeta potential was correlated with storage stability of bitumen. Rheological analysis revealed that DSAS-L mitigates the temperature and frequency sensitivities of bitumen after UV aging, thereby enhancing fatigue resistance and indicating suitability for pavements subjected to very heavy traffic loads. Analysis of the aromaticity, carbonyl and sulfoxide indices for DSAS-LB revealed that DSAS-L significantly inhibits the formation of oxygen-containing polar functional groups and suppresses the aromatization of bitumen molecules. Furthermore, all of aging index change rates indicated that the addition of DSAS-L provides at least a 9.18 % greater improvement in UV aging resistance of bitumen than LDHs. Based on the results the storage stability, rheology, aging index, and chemical structure and chemical components, a 3 % DSAS-L content in bitumen achieves the optimal UV aging resistance. These findings provide new insights for extending the service life of bitumen pavements in regions with severe UV exposure.

The sustainable transition of the steel industry is constrained by the limited utilization of metallurgical solid waste (MSW); however, its potential cementitious activity enables its application as anti-stripping agent in asphalt pavement, thereby significantly promoting its utilization. This study investigates the feasibility of employing multiple-MSW including steel slag (SS), flue gas desulfurization ash (FGDA) and granulated blast furnace slag (GBFS) as anti-stripping agent in asphalt concrete. The physicochemical properties of FGDA, SS and GBFS were first characterized, and then the MSWs were mixed to produce the solid-waste-based anti-stripping agent (SWA). Then, simulated water-vapor erosion was conducted on the SWA modified asphalt mortar. Rheological properties, surface free energy, and chemical functional groups of the asphalt mortar were evaluated respectively. Finally, the water-damage resistance of asphalt concrete with SWA was further assessed. The results indicate that SWA contains abundant alkaline minerals and exhibits potential hydration activity; the finer particle size of which enhances compatibility with asphalt. The addition of SWA within asphalt increases the compactness and mechanical performance of asphalt mortar. Compared with limestone powder (LP) asphalt mortar, SWA asphalt mortar exhibits superior rheological properties at high temperature, demonstrating better rutting resistance. SWA enhanced the adhesion work between asphalt and aggregate, also decreased the peeling rate, which confirms the interfacial reinforcement effect of SWA. The water-resistance performance of SWA-modified asphalt concrete has been markedly improved. After replacing LP with SWA in the asphalt-mastic mixture, RSM and TSR increase by 14.2% and 9.0%, respectively, while Cantabro mass loss decreases by 5.0%. Based on the performance comparisons, SWA can be used as an anti-stripping agent to enhance the water-resistance of asphalt concrete and thereby extend the service life of the road.

The hydration of free calcium oxide (f-CaO) leads to poor volume stability of steel slag, which cause cracking and performance degradation in pavement. This study explores innovative method by chelating Ca2* to achieve volume stability of steel slag. The effects of chelating agents on the volume expansion, performance and its mechanisms for volume inhibition were investigated. The results show that the four chelating agents exhibit distinct efficiencies in chelating Ca2*. As polymeric chelators, polyacrylic acid (PAA) and polyepoxysuccinic acid (PESA) demonstrate superior chelation capacity compared to phosphate-based agents such as sodium hexametaphosphate (SHMP) and sodium pyrophosphate (TSPP) due to their multidentate structure. This enhanced chelation thereby significantly reduces the f-CaO content in steel slag. Analysis of microstructure and properties revealed that the precipitates formed by the reaction of chelating agents with Ca2* fill the pores of steel slag, reducing its water absorption and porosity, and enhancing the steel slag's resistance to crushing and abrasion. Among them, steel slag modified with PAA and PESA exhibits more excellent volume stability and mechanical properties, with water absorption rates reduced to 1.073% and 1.055% respectively. The water immersion expansion rate of the asphalt mixtures prepared from it is less than 1%, which fully meets the requirements of road engineering. It is found that chelating agents undergo ion exchange with Ca2* liberated from f-CaO hydration, efficiently forming stable precipitates or amorphous chelates instead of crystalized Ca(OH)2. This process promotes f-CaO dissolution and diffusion, thereby effectively inhibiting volumetric expansion in steel slag induced by delayed hydration of residual f-CaO.

Developing low-carbon geopolymer cementitious materials using recycled concrete powder (RCP) represents a promising pathway for the high-volume, high-value utilization of construction solid waste. However, the low reactivity and high water absorption of RCP lead to severe drawbacks in high-volume RCP geopolymers, particularly insufficient mechanical strength and excessive drying shrinkage, which significantly restrict their widespread engineering application. To address these issues, an alkali-activated RCP–metakaolin (MK) geopolymer was prepared by replacing 60 wt.% MK with RCP. Layered double hydroxides (LDHs) intercalated with sodium lignosulfonate (SLS) and surface-modified with polyethylene glycol (PEG), designated as LP-LDH, were incorporated into the matrix. The effects of LP-LDH on the fresh properties, mechanical performance, and durability of the geopolymers were systematically investigated, and the micro-morphology and pore structure were characterized using XRD, FT-IR, XPS, SEM, and CT. The results demonstrate that the successful intercalation of SLS expands the interlayer spacing of LDHs from 0.75 nm to 1.33 nm, with PEG coating the LDH nanosheets via hydrogen bonding. The incorporation of LP-LDH significantly enhances the fluidity of the geopolymer mortar, with the fluidity increasing progressively at higher dosages, showing a 27.2% improvement over the control group at a 2% dosage. With increasing LP-LDH dosage, the setting times exhibit a trend of initially decreasing and subsequently increasing. The 1% LP-LDH dosage yields the optimal mechanical performance, increasing the 28-day compressive and flexural strengths by 11% and 33.3%, respectively, compared to the control group. Furthermore, LP-LDH substantially mitigates the drying shrinkage of the geopolymer mortar through pore structure refinement and the inhibition of moisture loss, achieving approximately a 50% reduction in the 90-day drying shrinkage strain at a 1.5% dosage. Microstructural analyses reveal that LP-LDH promotes geopolymer gel formation, effectively improving the overall performance of the geopolymer through the synergistic mechanisms of nano-filling, heterogeneous nucleation, and matrix bridging.

Pyrolysis carbon black (PCB)-based composite modified asphalt is a new type of environmentally friendly material, yet the complex interactions between its components remain challenging to characterize. To elucidate the performance regulation mechanism of multi-component and multi-phase modifiers in asphalt, this study investigated the interfacial evolution of polyethylene (PE)/synthetic plant ester (SPE) modified asphalt (PE/SPE-A) on the PCB surface using molecular dynamics. Guided by the concept that macroscopic performance emerges from cumulative molecular diffusion and interfacial interactions at the microscale, a grey relational analysis was employed to establish a cross-scale connection. This approach identified highly correlated indicators, providing an experimental basis for precise macroscopic property prediction. Results show that the adhesion energy between PE/SPE-A and the PCB surface reaches 116.3% of the base asphalt, and the diffusion coefficient at construction temperature reaches 155.1% of the base asphalt. Additionally, the PCB surface exhibits strong selective adsorption toward asphaltenes. Correlation analysis reveals a significant correlation between the nanoscale behavior of the asphalt binder, naphthene aromatic components, and the conventional physical properties. These findings enable prediction and evaluation of the macroscopic properties of composite modified asphalt.

To explore the different effects of various anti-aging agents on the asphalt aging resistance at different depths, the layered double hydroxides (LDHs), antioxidant, antioxidant-LDHs composite, and antioxidant intercalated hydrotalcite (OLDHs) on the aging performance across different depths in asphalt and mixture were investigated by dynamic shear rheometer test and fourier transform infrared spectrometer. MD simulations were employed to study the inhibition mechanisms of various anti-aging agents on oxygen diffusion within the asphalt. The results indicated that antioxidant was successfully intercalated into LDHs, with the free radical scavenging capacity reached by 88.3%. Different modifiers - increased the complex modulus (G*) of asphalt to varying degrees. The order of increase in asphalt G* is: LDHs > LDHs+Antioxidant > OLDHs > Antioxidant. As for anti-aging performance, whether in the short-term aging of asphalt or asphalt mixtures, all anti-aging agents showed different anti-aging enhancement effects of asphalt. The rheological aging factors and functional group aging factors of different asphalt layers of the aged asphalt mixtures show that oxygen molecules can diffuse into the asphalt from both the surface layer of the asphalt film and the asphalt-aggregate interface. OLDHs exerted anti-aging effects across the entire asphalt film, and the effect of antioxidants is worse than that of OLDHs. LDHs had the worst anti-aging effect in all layers. Simulation results confirmed that the oxygen diffusion coefficients were the lowest in both the OLDHs-modified asphalt (1.07 & times; 10(-2) m(2)/s) and its asphalt mixture (1.58 & times; 10(-2) m(2)/s). The excellent dispersibility of OLDHs can make it more effective in reducing oxygen penetration.

Asphalt pavement wearing courses are directly exposed to hydrodynamic scouring, fuel erosion, freeze-thaw action, and traffic abrasion, leading to accelerated surface deterioration, skid-resistance loss, frequent maintenance, and increased life-cycle carbon emissions. To address these challenges, this study developed an organosilicon-based erosion- and skid-resistant asphalt wearing course (OES-AWC) through a stepwise material design strategy. An organosilicon-treated asphalt concrete matrix was first prepared to improve resistance to moisture damage, fuel erosion, and ice adhesion, and its curing behavior and optimal dosage were determined. A skid-resistant surface layer was then designed by optimizing the anti-skid aggregate type, organosilicon-to-aggregate ratio, and surface texture. Finally, waterborne epoxy resin was introduced to enhance aggregate anchorage, and the integrated OES-AWC was evaluated in terms of abrasion durability, rutting resistance, long-term skid resistance, and life-cycle impacts. The results show that organosilicon treatment forms a hydrophobic siloxane network, which improves the moisture damage, fuel erosion, and anti-icing resistance of asphalt concrete by 22.0-41.1%. Emery aggregates and the optimized surface structure enhance friction stability, while waterborne epoxy resin significantly suppresses aggregate stripping under repeated wheel loading. Compared with conventional asphalt wearing courses, the optimized OES-AWC increased wear durability by 148.1% while maintaining stable skid resistance under prolonged abrasion. Life-cycle assessment further demonstrates that OES-AWC can reduce carbon emissions by 47.2% and overall costs by 25.0%, with a probability exceeding 90% according to the uncertainty analysis. These findings indicate that OES-AWC provides a durable, low-carbon, and cost-effective maintenance strategy for asphalt pavements exposed to complex service environments.

The high-quality recycling of aged SBS-modified asphalt mixtures remains a challenge in pavement engineering due to the futility of conventional rejuvenating agents in restoring the structure of aged SBS within the asphalt binder. In this study, Polyurethane prepolymer (PUP)-modified asphalt was prepared and utilized with varying PUP dosages to restore the maltene fractions and the degraded SBS structure in aged SBS-modified asphalt mixture. The pavement performance of the regenerated mixtures was evaluated through Marshall stability, rutting, and low-temperature three-point bending tests, etc. The results demonstrated that the incorporation of PPUMA greatly enhanced the low-temperature crack resistance, and water stability of the PmAM. Specifically, the regenerated PmAM with 4% PUP modified asphalt demonstrated significant recovery across multiple performance metrics. The Flexural tensile strength (RB), Maximum flexural tensile strain (epsilon B), Residual immersion Marshall stability (MS0), and Freeze-thaw splitting strength ratio (TSR) reached 103.71%, 109.6%, 99.41%, and 99.76% of the fresh mixture level, respectively. Gel Permeation Chromatography on the extracted asphalt from the regenerated PmAM showed that weight-average (Mw) molecular weight decreased from 4777 g/mol to 4262 g/mol, indicating that the fresh asphalt in the PUP modified asphalt supplemented the low molecular weight components of the aged binder. Fourier Transform Infrared Spectroscopy and Fluorescence microscope analysis revealed that the broken network structure of the SBS modified binder was repaired due to the reactions between the isocyanate groups of PUP and the aged SBS. This study confirms that PUP modified asphalt enables the high-quality recycling of aged SBS-modified asphalt mixture.

Although conventional organic deodorants can inhibit the emissions of volatile organic compounds (VOCs) in asphalt, their practical application is limited by high volatility, poor storage stability and difficulty in transporting them over long distances. To address these issues, the deodorant was encapsulated in urea-formaldehyde resin through in-situ polymerization, forming microcapsules that can maintain the stability of the deodorant and release them at the mixing temperature of asphalt. The deodorant-microcapsules were first characterized in terms of their microscopic morphology, particle size, rupture temperature and deodorant-loading capacity. The deodorant-microcapsules were then incorporated into the 70# base asphalt to study their impact on the fundamental properties, storage stability, high, medium and low-temperature rheological behaviors of the modified asphalt. Furthermore, the inhibitory effects of the deodorant-microcapsules on VOCs and H2S emissions from asphalt were explored. Results demonstrated that the microcapsules produced in this study were structurally intact, with uniform size distribution and up to 73.8% deodorant-loading capacity. Deodorant-microcapsules strengthened the intermediate/low-temperature properties of asphalt while slightly weakening its high-temperature properties. Furthermore, the microcapsules effectively reduced both concentration and variety of VOCs released from asphalt, with enhanced inhibitory effects as dosage increased. The optimal dosage of microcapsules was 0.13%. Compared to base asphalt, the deodorized asphalt containing 0.13% microcapsules showed 82.86% and 90.00% reductions in number of chain hydrocarbons and aromatic hydrocarbons, respectively, with total VOCs concentration and average H2S concentrations decreasing by 61.84% and 70.06%. This research can provide a novel approach for producing deodorant-asphalt.

Under long-term heavy load and complex service environments, polyurethane-modified asphalt (PUMA) struggles to simultaneously satisfy the requirements of rutting and cracking resistance of asphalt pavements, as cyclic stress loading reduces the elastic recovery and low-temperature toughness of polyurethane (PU). To address this issue, this study employed hydroxylated crumb rubber (HCR), which is obtained by activating the surface of crumb rubber (CR) and can chemically crosslink with PU in asphalt to form a crosslinked network structure. The aim was to enhance the rutting and cracking resistance of PUMA by utilizing the elasticity and low-temperature toughness of CR. An orthogonal design was employed to systematically design a modified asphalt formulation with PU and HCR (PU/HCRMA) by controlling the isocyanate index and the contents of PU and HCR. The basic properties, rheological properties, and viscoelastic properties of PU/HCRMA were systematically investigated. The results demonstrate that the rutting and cracking resistance of PU/HCRMA are substantially enhanced, with an improvement of 28.91% in the rutting factor at 64 °C compared to PUMA and a reduction of 49.93 MPa in the stiffness modulus at -24 °C. Simultaneously, incorporating HCR in PUMA enhances its viscosity and flow resistance while reducing temperature susceptibility. Furthermore, by providing load-bearing sites, HCR endows PU/HCRMA with exceptional elastic recovery and deformation resistance. Results from FTIR and FM confirm the reaction between isocyanate groups in the PU prepolymer and the hydroxyl groups on the surface of HCR and the formation of HCR-PU crosslinked networks. Finally, PU/HCRMA asphalt mixtures demonstrate significant improvements in both rutting and cracking resistance. This research outcome provides a new direction for the development of high-performance road asphalt materials.

Dynamic covalent bond-based polyurethane offers a promising route to enhance asphalt crack self-healing, yet its healing efficiency often relies on external heating or prolonged resting, limiting its effectiveness under pavement service temperatures. Herein, a novel CO2-based polyurethane-modified asphalt is synthesized to achieve efficient room-temperature self-healing through synergistic dynamic disulfide and hydrogen bonding networks. The modifier was synthesized using CO2-based poly(propylene carbonate) diol and castor oil. Chain extension with 4,4 '-dithiodianiline introduced dynamic disulfide bonds alongside highly polar urea groups, establishing a dense hydrogen bonding network governed by both urethane and urea linkages. Comprehensive spectroscopic analyses (FT-IR, Raman, XPS) confirmed a dual-network architecture wherein disulfide bonds are embedded in hydrogenbond-rich microdomains, which enhances their dynamic exchange capability. Rheological tests demonstrated superior high-temperature deformation resistance and improved low-temperature crack relaxation. In tensile recovery tests, the modified asphalt achieved healing efficiencies of 94.1% after 3 h and 115% after 6 h at room temperature, with the latter exceeding 100% due to the secondary cross-linking of hydrogen bonds at the interface, which shifted the fracture point. This work establishes a green, low-carbon modification strategy that integrates carbon utilization with self-healing, offering a promising pathway toward durable, low-maintenance pavement materials.