Search Results (659)

Capsaicin is an amphiphilic organic molecule containing both a hydrophobic hydrocarbon chain and polar functional groups, giving it the potential to regulate the surface wettability and interfacial interactions of organic materials. To evaluate capsaicin as an interfacial modifier for improving the anti-icing performance of asphalt binder, capsaicin-modified binders with different dosages were prepared and systematically characterized in terms of conventional properties, high- and low-temperature rheological performance, chemical structure, surface wettability, and water-droplet freezing and melting-induced shedding behavior. Capsaicin was incorporated into the asphalt matrix mainly through physical blending and moderately increased the high-temperature stiffness. At an appropriate dosage, the low-temperature creep and stress-relaxation properties were also improved. The addition of capsaicin increased the water contact angle and reduced the total surface free energy, thereby weakening water spreading and water-asphalt interfacial interactions. At temperatures from −5 to −20 °C, all modified binders exhibited delayed complete freezing and facilitated the gravity-driven shedding of frozen droplets during melting at room temperature. Pearson correlation analysis further showed that longer freezing times and shorter ice-shedding times were closely associated with a larger water contact angle and lower surface free energy. Additional validation after long-term aging confirmed that the surface-regulation and freezing-shedding effects of capsaicin remained effective after aging. Considering both binder performance and freezing-shedding behavior, a capsaicin dosage of 12% provided the best overall balance. These findings identify capsaicin as a promising interfacial modifier for the design of anti-icing asphalt materials. Full article

The application of two-dimensional molybdenum disulfide (MoS₂) in asphalt binder modification is limited by its inherent chemical inertness and severe agglomeration. In this study, four surface-functionalization strategies, including (3-aminopropyl)triethoxysilane (APTES) silanization, polydopamine (PDA) coating, tannic acid (TA)–APTES co-deposition, and PDA–APTES hybrid modification, were used to improve the dispersion and compatibility of MoS₂ nanosheets in styrene–butadiene–styrene (SBS)-modified asphalt binders. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) results indicated that surface functionalization introduced organic functional groups, reduced nanosheet restacking, and preserved the intrinsic 2H-MoS₂ crystal structure. Binder-level rheological tests and thermogravimetry–differential scanning calorimetry (TG–DSC) analysis showed that surface-functionalized MoS₂ improved the high-temperature deformation resistance, creep recovery, fatigue resistance, low-temperature relaxation capacity, and thermal stability of SBS-modified asphalt. Among the investigated binders, PDA–APTES-functionalized MoS₂/SBS-modified asphalt exhibited the most balanced performance. At 3.2 kPa, its recovery rate reached 79.5%, while its non-recoverable creep compliance decreased to 0.105 kPa⁻¹. Its fatigue life at 15% strain increased by 76.8% compared with SBS-modified asphalt, and its creep stiffness at −24 °C decreased to 222 MPa. Mechanistic interpretation suggests that the PDA–APTES hybrid layer may act as an organic–inorganic interfacial transition region, improving MoS₂ dispersion and compatibility with the SBS–asphalt phase and facilitating more effective integration of the nanosheets into the composite structure. These results indicate that PDA–APTES-functionalized MoS₂ nanosheets are promising interfacial modifiers for improving the rheological and thermal performance of SBS-modified asphalt binders. Full article

High reclaimed asphalt pavement (RAP) contents are often limited by insufficient restoration of field-aged SBS-modified asphalt and the lack of a comprehensive method for rejuvenator dosage selection. This study aimed to develop a multi-performance-based approach for determining the dosage of an epoxy-based reactive rejuvenator under high-RAP conditions. Rejuvenated binders with different dosages were evaluated using conventional tests, DSR, MSCR, BBR, and LAS tests. Continuous low-temperature grading temperature, dissipated energy ratio, and entropy-weight TOPSIS were used for comprehensive evaluation, while GPC was employed to characterize molecular-weight distribution. The rejuvenator improved low-temperature relaxation, fatigue resistance, energy dissipation, and workability, whereas excessive dosages reduced rutting resistance and elastic recovery. Entropy-weight TOPSIS ranked RA-6 highest, with a relative closeness coefficient of 0.66504, and this ranking was consistent with the overall trends obtained from individual performance tests, supporting the feasibility of the proposed evaluation method. GPC results showed systematic changes in molecular-weight distribution after rejuvenation. For the investigated material system, 6% is recommended among the tested dosages. The proposed framework provides a practical basis for dosage determination when material characteristics and performance requirements vary. Full article

This study developed a composite rejuvenator comprising recycled polyethylene wax (PREW), waste cooking oil (WCO), and epoxidized soybean oil (ESO) activated by the tertiary amine catalyst BDMA to improve the intermediate-temperature rejuvenation of aged SBS-modified asphalt binder. The binder was subjected to combined rolling thin-film oven and pressure aging vessel aging. Conventional tests, rotational viscosity, bending beam rheometer, multiple stress creep recovery, fluorescence microscopy, and Fourier transform infrared spectroscopy were used to evaluate macroscopic, rheological, and microstructural properties. Aging hardened and embrittled the binder, increased softening point and viscosity, reduced penetration and ductility, and disrupted the polymer-rich phase. PREW reduced flow resistance and retained relatively high-temperature structural stability, whereas WCO improved flexibility and flowability, although excessive softening impaired high-temperature stability. ESO/BDMA treatment was accompanied by changes in oxygen-containing functional group-related absorption regions and improved apparent connectivity of the SBS-rich phase. Among the tested temperatures, 120 °C provided the best overall balance among the evaluated properties, satisfying low-temperature stress-relaxation requirements while limiting high-temperature creep deformation. These results identify 120 °C as the preferred treatment temperature for the PREW/WCO/ESO-BDMA rejuvenation system. Full article

Polymer modifiers and carbon-based materials have been widely proposed as potential asphalt additives to improve performance. However, limited studies have systematically compared micro- and nanocoke from different sources in combination with SBS and Elvaloy polymers or linked binder rheology with mixture performance. To address this gap, this study investigated the effects of micro- and nanodispersed petroleum and coal coke combined with SBS and Elvaloy polymers on the rheological behavior of asphalt binders and the performance of asphalt concrete mixtures. Rheological properties were evaluated by dynamic shear rheometer (DSR) testing, and asphalt concrete mixtures were tested for compressive strength and crack resistance. The modified systems were successfully used to obtain commercial polymer-modified bitumen grades: BMP 70/100, BMP 50/70 and BMP 35/50. With 1 wt.% micro coal coke and 0.1 wt.% SBS modification, a softening point of 73.7 °C and a penetration of 22.3 × 0.1 mm was observed. Micro coal coke–SBS system showed the highest compressive strength at 20 °C (3.29 MPa), while the largest crack resistance (4.39 MPa) and the best high-temperature mixture strength (0.90 MPa at 50 °C) were obtained when 0.5 wt.% nanocoke and 0.5 wt.% Elvaloy are used. These findings demonstrate that hybrid coke/polymer modification is an effective approach for enhancing asphalt performance, with micro coal coke–SBS systems providing the highest stiffness and rutting resistance, while nanocoke–Elvaloy systems delivered superior crack resistance and overall performance balance. Full article

Asphalt serves as the core binder for heavy-load high-modulus pavements, and its viscoelasticity across a wide temperature range directly governs pavement-rutting resistance, low-temperature crack resistance and service life. Virgin asphalt contains abundant light fractions and exhibits insufficient stiffness at high temperatures. Modification with single styrene–butadiene–styrene block copolymer (SBS) fails to meet the anti-deformation requirements under heavy loads, while separate incorporation of nano-silica (nano-SiO₂) aggravates low-temperature brittleness. Existing studies lack comprehensive investigations into the rheological evolution laws and synergistic microscopic mechanisms of asphalt modified by combined SBS and nano-SiO₂. In this paper, virgin asphalt was adopted as raw material to prepare composite modified asphalt with gradient dosages. Integrated macroscopic performance tests and multi-scale microscopic characterizations were conducted for systematic analysis. High-temperature, low-temperature and fatigue performances were evaluated via conventional physical property tests, temperature sweep tests, multiple stress creep recovery (MSCR), linear amplitude sweep (LAS) and bending beam rheometer (BBR) tests. Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC) and thin-layer chromatography–flame ionization detection (TLC-FID) were utilized to analyze variations in functional groups, molecular weight and four fractions, to elaborate the two-phase synergistic modification mechanism. The results demonstrate that the combined incorporation of SBS and nano-SiO₂ synchronously optimizes the comprehensive performances of asphalt. Compared with single-SBS-modified asphalt, the sample with optimal dosages achieves elevated high-temperature modulus and rutting factor, reduced permanent deformation, improved low-temperature stress relaxation capacity and remarkably decelerated fatigue damage accumulation rate. Microscopic characterizations verify that only physical interactions occur during modification without generating new substances. The nano-filler facilitates the aggregation of small molecules and increases the proportion of macromolecules; meanwhile, it physically adsorbs light fractions and induces apparent redistribution of asphalt components, raising the relative proportion of resins and asphaltenes in the organic asphalt phase, realizing moderate heavy-fraction enrichment of the asphalt system. This study clarifies the internal correlation between molecular fraction evolution characteristics and macroscopic rheological performances of asphalt co-modified by nano-SiO₂ and SBS, which can provide theoretical references for formula design and engineering application of modified asphalt materials. Full article

To explore the high-value utilization of liquid recovery products from waste wind turbine blades in road binders, a liquid-rich fraction obtained from subcritical acetic acid degradation and subsequent vacuum distillation of waste wind turbine blade epoxy composites was introduced into styrene–butadiene–styrene (SBS)-modified asphalt to prepare composite-modified asphalt. Conventional property tests, dynamic shear rheological tests, bending beam rheological tests, steady shear tests, master curve analysis, Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC) were conducted to systematically evaluate the influence of the liquid-rich fraction on the properties and structural characteristics of the composite-modified asphalt. The results showed that, with increasing liquid-rich fraction content, the softening point increased, while penetration and ductility decreased, and the rotational viscosity at 135 °C increased, indicating enhanced overall stiffness and high-temperature flow resistance. High-temperature rheological results showed that the liquid-rich fraction increased the storage modulus, loss modulus, and rutting factor, while decreasing the phase angle improved the high-temperature deformation resistance of the composite-modified asphalt. Low-temperature rheological results indicated that the creep stiffness S increased, the m-value decreased, and the S/m ratio increased, suggesting weakened stress relaxation capacity and reduced cracking resistance at low temperature. Fatigue factor and steady shear results revealed that the liquid-rich fraction enhanced structural stability and flow resistance but also increased fatigue damage sensitivity at intermediate temperature. Master curves, Black diagram, and Cole–Cole plots further demonstrated that the liquid-rich fraction increased the modulus level over a wide frequency domain and strengthened the structural stability of the asphalt system. FTIR and GPC results indicated that the introduction of the liquid-rich fraction increased the relative contents of aromatic structures and polar oxygen-containing groups and promoted molecular association and increased the apparent molecular weight level of the system. Overall, the liquid-rich fraction acted as a structure-enhancing modifier in SBS-modified asphalt, improving its high-temperature performance while causing a certain trade-off in low-temperature and fatigue properties. Therefore, the dosage should be selected by balancing high-temperature stability, low-temperature cracking resistance, and fatigue durability, and the practical sustainability of this recycling route still requires dedicated economic and environmental evaluation. Full article

This study evaluates waste-derived used motor oil (UMO) as a softening and viscoelastic rebalancing agent for a sustainable asphalt binder incorporating guayule resin and crumb rubber modifier (CRM). ARG75(20):25 contained 75% asphalt rubber (20% CRM by asphalt weight) and 25% guayule resin, replacing 37.5% of asphalt (PG 64-22). CRM reinforced high-temperature performance, whereas the guayule-containing ARG system exhibited intermediate- and low-temperature stiffness, preventing PG 64-22 compliance. UMO at 1%, 3%, and 5% by total binder weight was evaluated using rotational viscosity, dynamic shear rheometer, bending beam rheometer, multiple stress creep and recovery (MSCR), black space analysis, and Fourier transform infrared (FTIR) spectroscopy under original, RTFO, and PAV aging. UMO reduced stiffness while maintaining Superpave rutting thresholds. MSCR showed lower J_nr,3.2 at 1% and 3% UMO, and higher R_3.2 across dosages than base asphalt, despite increased stress sensitivity. Viscosity decreased, indicating improved flow. Continuous grades shifted from PG 73-16 to PG 70-19, PG 66-21.6, and PG 65-23 at 1%, 3%, and 5% UMO, respectively. FTIR showed attenuated PAV carbonyl development with 5% UMO; sulfoxide development remained comparable. The 3% dosage showed the best balance, whereas 5% UMO alone met standard PG 64-22 criteria, establishing binder-level feasibility for mixture- and pavement-level validation. Full article

Fischer–Tropsch (FT) wax is widely used as an organic warm-mix asphalt (WMA) additive, lowering binder viscosity during construction while improving high-temperature deformation resistance in service; however, the comparative responses of SBS-modified asphalt to different FT wax grades remain insufficiently understood. Sasobit and three FT waxes with different carbon-chain ranges (FT 80, FT 90, FT 100) were incorporated into SBS-modified asphalt at about 7.0 wt%, and their effects on macroscopic performance, rheology, molecular packing, and diffusion were evaluated using physical-property tests, rotational viscosity, dynamic shear rheometer (DSR) testing, and molecular dynamics (MD) simulation. In the MD analysis, the wax additives were represented by linear alkane molecules with different chain lengths, and the systems were subjected to structural optimization, annealing, and NPT equilibration using the COMPASS III force field before the molecular descriptors were evaluated. The experimental results showed that all four additives produced a trade-off between increased high-temperature stiffness and reduced low-temperature ductility. Sasobit gave the strongest viscosity reduction (>70% above 165 °C), while FT 90 and FT 100 showed more stable, predictable viscosity–temperature behavior favorable for a wider construction window. DSR results showed higher complex modulus and lower phase angle for all modified binders at low frequencies, suggesting an increased elastic contribution and greater resistance to deformation under the tested rheological conditions; FT 80 produced the greatest stiffening but also the largest free volume and loosest molecular packing, whereas FT 100 increased cohesive energy density and reduced free volume, reflecting denser packing and stronger intermolecular cohesion. MD simulations revealed that FT wax enhanced short-time local molecular mobility and segment diffusion in its molten state (explaining the warm-mix viscosity reduction), whereas macroscopic stiffening and ductility loss at ambient temperatures were dictated by wax microcrystallization and physical network constraints that restricted long-range chain relaxation. By comparing three FT wax grades and Sasobit under the same experimental dosage and testing framework, this study provides a controlled assessment of the relationships among wax-grade characteristics, binder-scale rheological responses, and MD-derived molecular descriptors. Full article

This study examines how reclaimed asphalt pavement (RAP) dosage, virgin-binder grade, and virgin-binder content govern the cracking response of Marshall-designed mixtures. The experimental matrix comprised four RAP levels (30%, 40%, 50%, and 60%), two modified virgin binders (PG 76-22 and PG 88-34) evaluated at their respective optimum asphalt contents (OACs), and two binder-rich PG 76-22 variants (OAC + 0.3 and OAC + 0.5 percentage points); virgin mixtures served as controls. Cracking behavior was characterized by low-temperature semi-circular bending (SCB), the Illinois Flexibility Index Test (I-FIT), and direct-tension cyclic fatigue (DTCF). Fracture and fatigue indicators were subsequently integrated into cracking balance design diagrams, and k-means clustering was used to derive provisional, dataset-specific performance boundaries for long-term oven-aged mixtures. The results show that the higher-performance binder improved long-term cracking resistance at moderate RAP contents. By contrast, mixtures with 50% or 60% RAP and PG 76-22 displayed a distinctly brittle response. Increasing the PG 76-22 content above OAC produced only limited gains. These findings demonstrate that binder quality, rather than a small increase in binder dosage, is the more effective lever for balancing fracture and fatigue resistance in mixtures with substantial RAP contents. Full article

Increasing plastic waste and limited recycling rates underscore the need for value-added recycling applications. Polymers commonly present in plastic waste streams, including packaging films, bottles, caps, and rigid containers, may provide a practical pathway for developing plastic-modified asphalt binder (PMAB) systems. In this study, virgin high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP) were selected as reference modifiers to evaluate their intrinsic effects on performance grade (PG) 58-28 and PG 67-22 base binders. Conventional high-, intermediate-, and low-temperature gradings were complemented by $\Delta T_c$, the Christensen–Anderson R-value (R-value), the Glover–Rowe (G-R) parameter, Linear Amplitude Sweep (LAS) fatigue analysis modeled via Viscoelastic Continuum Damage (VECD), rheological master curves, and extended Bending Beam Rheometer (BBR) testing. Modification improved high-temperature grading and LAS-based fatigue response while increasing master-curve stiffness. However, $\Delta T_c$, G-R parameter, and extended BBR results indicated increased low-temperature cracking susceptibility. High-temperature grades increased by 3.4 °C, 2.8 °C, and 2.3 °C per percent HDPE, LDPE, and PP, respectively, whereas low-temperature grade losses reached 7.8 °C; HDPE produced the highest high-temperature grade improvement, while LDPE showed the greatest extended BBR grade loss, and PP exhibited the fastest physical hardening rate. These results provide a controlled binder-level baseline for evaluating HDPE, LDPE, and PP as modifiers for future PMAB development. Full article

Improving the flame-retardant performance of asphalt is particularly important for tunnel pavements, where confined environments can intensify fire hazards and smoke accumulation. This study prepared different modified asphalt binders to investigate their flame-retardant performance and rheological properties. The limiting oxygen index and smoke density rating were first used to evaluate the flame-retardant and smoke-suppression performance. Frequency sweep tests were then conducted to analyze the rheological behavior, aging characteristics, and low-temperature cracking resistance of the binders. Finally, microscopic tests were performed to reveal the thermal decomposition behavior and modification mechanism. Results showed that the incorporation of FR02 increased the limiting oxygen index of the warm-mix modified binders by more than 47%. Among the investigated binders, 13% fast-melting warm-mix flame-retardant composite modifier (SBS-WZ) exhibited the highest limiting oxygen index of 30.95% and the lowest smoke density rating of 57.73, indicating the best experimentally measured flame-retardant and smoke-suppression performance. At a reduced frequency of approximately 10⁻² rad/s, the unaged 13%SBS-WZ binder exhibited a complex modulus of approximately 2.0 × 10⁵ Pa, nearly one order of magnitude higher than those of the conventional 4%SBS- and 4%fast-melting SBS modifier (SBS-T), while its phase angle was approximately 6–10° lower. At −24 °C, the creep stiffness and creep rate of the unaged 13%SBS-WZ binder were approximately 654 MPa and 0.246, respectively. After Pressure Aging Vessel (PAV) ageing, these values changed to approximately 720 MPa and 0.237. Moreover, the onset decomposition temperature of 13%SBS-WZ was 392.1 °C, which was 17.2 °C higher than that of 4%SBS-T. Together with its higher residual mass, this result suggests enhanced thermal stability and residue-forming potential, which may partly explain the measured improvements in flame-retardant and smoke-suppression performance. However, the increased complex modulus and reduced creep rate indicate a concurrent loss of low-temperature flexibility. The findings can provide theoretical guidance and technical support for the application of this material in tunnel asphalt pavements. Full article

The modification of bitumen with recycled rubber materials has gained significant attention due to its potential to enhance pavement performance and support sustainable waste management. In this study, the rheological properties of bitumen modified with crumb rubber (CR) and devulcanized crumb rubber (DCR) were investigated. Rubber modifiers were added at concentrations of 5–25% by weight, and the rheological behavior was evaluated using a Dynamic Shear Rheometer at 1.59 Hz over a temperature range of 46–96 °C. Key parameters, including storage modulus (G′), loss modulus (G″), and complex viscosity (η*), were analyzed. The results indicate that increasing rubber content significantly enhances stiffness and viscosity, improving resistance to deformation at elevated temperatures. Moreover, DCR-modified binders exhibit higher rheological performance compared to CR systems, indicating better compatibility with the bitumen matrix. Overall, devulcanized rubber demonstrates superior efficiency as a modifier and shows strong potential for improving the durability and high-temperature performance of asphalt binders. Full article

This study investigates the low-temperature relaxation behavior of asphalt binders and asphalt mastics using a ductilometer-based uniaxial tensile relaxation test under a constant displacement rate. Although the low-temperature performance of SBS-modified asphalt binders has been widely studied, the relaxation mechanisms of asphalt mastics containing SBS-modified binders, particularly considering the effects of the SBS content and short-term aging, remain insufficiently understood. Polymer-modified binders were prepared from 50/70 penetration-grade bitumen blended with an industrially produced SBS copolymer concentrate containing 9% SBS. Three binders with SBS contents of 3%, 5%, and 7% were manufactured and used to prepare asphalt mastics with mineral filler. Tensile relaxation tests were performed at −12 °C on unaged and RTFOT-aged specimens. The relaxation behavior was evaluated using a modified generalized Maxwell model to describe the viscoelastic response of the materials. The novelty of this study lies in the systematic comparison of SBS-modified binders and corresponding asphalt mastics using a unified experimental and modeling approach. Unlike previous studies focused mainly on polymer-modified binders, this research extends the analysis to binder–filler systems and provides new insight into the influence of the SBS content and aging on stress relaxation mechanisms. The results demonstrate that increasing the SBS content improves the relaxation capacity of both the binders and mastics, enhancing their ability to dissipate thermally induced stresses. Moreover, a higher SBS content reduces the sensitivity of materials to short-term aging, indicating improved resistance to low-temperature cracking. Full article

Foamed asphalt mixtures (FAMs) are considered to be among the most environmentally friendly. They are produced at temperatures ranging from 100 °C to 120 °C. In order to produce asphalt mixtures at such a low temperature, it is necessary to produce foamed asphalt binder with high foaming parameters, i.e., maximum expansion (ER) and a half-life (HLa) of the asphalt foam. Consequently, the asphalt binders were modified with a surfactant at a concentration of 0.6% by weight of the binder, prior to its foaming with water. Subsequently, an AC 8 S asphalt mixture was designed using traditional hot-mix asphalt (HMA) technology and with modified foamed asphalt binders in quantities ranging from 5.6% to 6.5% by weight, in increments of 0.3%. To ensure optimal properties of the FAM, hydrated lime was added at levels of 0%, 15%, 30% and 45% by weight as a substitute for filler. The influence of modified foamed asphalt binders and hydrated lime on the void content (Va), resistance to moisture and frost (TSR) and resistance to permanent deformation (WTS_AIR and PRD_AIR) of the FAM was assessed. A key element of the research was the determination of the complex modulus of stiffness E* and resistance to low-temperature cracking R₋₂, σ_cry, T_failure and crack propagation using the SCB methodology. Analysis of the test results using desirability functions enabled the determination of the optimum proportions of foamed asphalt binders and hydrated lime—5.9% and 30% respectively—in the FAM, ensuring that its properties meet all the requirements of the relevant standards and guaranteeing resistance to low-temperature cracking. Full article