Search Results (225)

This study investigates the rheological, thermal, and microstructural performance of three novel high-elasticity polymer modifiers (HEMs) incorporated into asphalt binders. The modifiers were evaluated at their recommended dosages using a multi-scale framework combining rotational viscosity, dynamic shear rheometry (frequency sweeps, Cole-Cole plots, Black diagrams, and master curves), bending beam rheometry, differential scanning calorimetry (DSC), fluorescence microscopy (FM), atomic force microscopy (AFM), and Fourier transform infrared spectroscopy (FTIR). Results show that HEM-B achieved the highest values of the superpave rutting parameter (G*/sinδ = 5.07 kPa unaged, 6.73 kPa aged), reflecting increased high-temperature stiffness but also higher viscosity, which may affect workability. HEM-C exhibited the lowest total enthalpy (1.18 W·g⁻¹) and a glass transition temperature of −7.7 °C, indicating improved thermal stability relative to other binders. HEM-A showed the greatest increase in fluorescent area (+85%) and the largest reduction in fluorescent number (−60%) compared with base asphalt, demonstrating more homogeneous phase dispersion despite higher enthalpy. Comparison with SBS confirmed that the novel HEMs not only meet but exceed conventional performance thresholds while revealing distinct modification mechanisms, dense cross-linking (HEM-B), functionalized thermoplastic compatibility (HEM-C), and epoxy-tackified network formation (HEM-A). These findings establish quantitative correlations between rheology, thermal stability, and microstructure, underscoring the importance of dosage, compatibility, and polymer network architecture. The study provides a mechanistic foundation for optimizing high-elasticity modifiers in asphalt binders and highlights future needs for dosage normalization and long-term aging evaluation. Full article

To overcome the limitations of conventional high-viscosity high-elasticity modified asphalt, including high production costs, phase separation, and thermal degradation, this study introduces a novel fast melting Styrene-Butadiene-Styrene modifier (SBS-T) for asphalt modification. The primary novelty of SBS-T lies in its ability to mitigate phase separation and thermal degradation while simplifying the production process, thereby offering a more robust and cost-effective alternative. The viscoelastic properties of SBS-T-modified asphalt were characterized through frequency sweep tests under varying loading conditions, while its fatigue behavior was quantitatively assessed using the Simplified Viscoelastic Continuum Damage (S-VECD) model. The results indicate that the SBS-T-modified asphalt exhibits outstanding viscoelastic performance across a broad range of temperatures and loading frequencies, and can better adapt to the temperature and load changes in complex pavement environments. Among them, the influence of long-term aging on the linear viscoelastic characteristics of SBS-T-modified asphalt is greater than that of ultraviolet aging. The SBS-T-modified asphalt also shows better stiffness and resistance to shear deformation. The fatigue life of asphalt gradually decreases with the deepening of the aging degree, among which the impact of long-term aging on fatigue life is greater than that of ultraviolet aging. Under different aging conditions, SBS-T-modified asphalt has shown good fatigue performance and is suitable for practical engineering applications. Full article

High-permeability emulsified asphalt has emerged as a promising prime coat for enhancing interlayer bonding in semi-rigid pavement structures. However, its widespread adoption remains limited by insufficient permeability and inconsistent mechanical properties. This study systematically investigated the effects of emulsifier ionic type (cationic or anionic), kerosene dosage (0–20%), and diluted asphalt content (corresponding to oil-water ratios of 5:5 and 4:6) on the comprehensive performance of high-permeability emulsified asphalt. Fundamental physical tests (sieve residue, evaporation residue, penetration, softening point, ductility), permeability evaluation, rotational viscosity measurements, and adhesion performance tests were conducted. Grey relational analysis (GRA) was employed to quantify the influence of each factor and their interactions on key performance metrics. The results reveal that anionic emulsifiers significantly improved low-temperature ductility and permeability. A low kerosene dosage (<10%) enhanced permeability and viscosity but compromised thermal stability at higher levels. Reducing the diluted asphalt content partially offset these adverse effects. GRA identified kerosene dosage as the dominant factor influencing permeability, softening point, and adhesion performance while emulsifier ionic type primarily affected ductility, and oil-water ratio strongly governed emulsification quality and viscosity. These findings provide quantitative insights for optimizing the composition of high-permeability emulsified asphalt and serve as a theoretical foundation for its engineering application in durable prime coats. Full article

Asphalt is widely used as a binder in pavement engineering. The temperature-dependent phase transition behavior of asphalt binders critically influences pavement performance. This study comprehensively evaluates phase transition characteristics to establish robust performance indicators. Dynamic mechanical analysis (DMA) was employed to characterize 30 neat asphalt binders across a broad temperature range. Phase transition temperatures and moduli were derived from complex and loss modulus curves. Correlations with saturate, aromatic, resin, and asphaltene (SARA) fractions and conventional properties (penetration, viscosity, ductility) were statistically analyzed. The results revealed significant performance variations among binders of identical penetration grades. T_g effectively differentiated low-temperature behavior, overcoming empirical limitations. High-temperature indicators (T₂, E₂₀) strongly correlated with viscosity (R² > 0.96). SARA analysis showed that saturates reduced T_g (r = −0.566) while asphaltenes increased E₂₀ (r = 0.804). Multiple regression models confirm synergistic interactions among SARA fractions, although low-temperature indices exhibit a weaker dependence on composition. DMA-derived phase transition parameters provide physically meaningful performance indicators, superior to conventional metrics. Incorporating T_g and T₂/E₂₀ into grading systems can enhance asphalt selection for thermal susceptibility, advancing pavement durability design. Full article

Aging of asphalt is a major cause of pavement distress. While regenerators restore aged asphalt, their mechanisms and efficacy differences remain unclear. This study quantified the repair effects of waste bio-oil (WBO) and mineral oil (MO) rejuvenators on aged asphalt binder using a comprehensive characterization approach. Conventional properties (penetration, softening point, ductility), functional groups (FT-IR), thermal stability (TG), differential scanning calorimetry (DSC), and dynamic shear rheology (DSR) were analyzed. Results reveal distinct mechanisms: WBO acts chemically via polar molecules, selectively reducing oxygen-containing groups and significantly improving ductility, while MO acts physically through light components that dilute viscosity, exhibiting weaker chemical repair. WBO-regenerated asphalt showed a lower thermal-oxidative peak temperature, superior low-temperature ductility, and enhanced high-temperature rheological performance (higher rutting factor, optimized viscoelasticity). These mechanistic differences—chemical restoration (WBO) versus physical replenishment (MO)—determine performance outcomes at the binder level. The findings provide a theoretical basis for regenerator selection in pavement engineering, highlighting WBO’s advantages for functional group restoration and balanced thermal rheological properties, supporting sustainable road development. Full article

Waste animal fat (WAF) can be converted to distillate fractions similar to petroleum solvents and used as solvents via pyrolysis and fractional distillation. Pyrolysis oil from triglyceride materials presents adequate viscosity and volatility, compared to petroleum fuels, but shows acid values between 60–140 mg KOH/g, impeding its direct use as biofuels without considerable purification of its distillates. Fractional distillation can be applied for the purification of bio-oil, but only a few studies accurately describe the process. The purpose of this study was to evaluate the effect of temperature in the conversion of waste animal fat into fuel-like fractions by pyrolysis and fractional distillation in a semi-batch stirred bed reactor (2 L) according to reaction time. Waste animal fat was extracted (rendering) from disposed meat cuts obtained from butcher shops and pyrolyzed in a stainless-steel stirred bed reactor operating in semi-batch mode at 400–500 °C. The obtained liquid fraction was separated according to reaction time. The pyrolysis bio-oil at 400 °C was separated into four distinct fractions (gasoline, kerosene, diesel, and heavy phase) by fractional distillation with reflux. The bio-oil and distillate fractions were analyzed by density, kinematic viscosity, acid value, and chemical composition by gas chromatography coupled to mass spectra (GC-MS). The results show that, for semi-batch reactors with no inert gas flow, higher temperature is associated with low residence time, reducing the conversion of fatty acids to hydrocarbons. The distillate fractions were tested in a common application not sensible to the fatty acid concentration as a diluent in the preparation of diluted asphalt cutback for the priming of base pavements in road construction. Kerosene and diesel fractions can be successfully applied in the preparation of asphalt cutbacks, even with a high acid value. Full article

This study presents a method to more reasonably control the quality performance of activated rubber asphalt by microwave activation. Different activated rubber asphalt preparation process parameters (reaction temperature, stirring rate, and reaction time) were selected to explore the influence of different process parameters on the macroscopic properties of rubber asphalt, and a multi-indicator evaluation model was set up using the theoretical method of the RSR model to determine the optimal production process parameters. The results showed that reaction temperature had the strongest influence (gray correlation > 0.85) among production parameters, followed by stirring rate and reaction time. The optimal parameters identified were a reaction temperature of 220 °C, a stirring rate of 1000 rpm, and a reaction time of 120 min, under which the viscosity–temperature sensitivity decreased by approximately 18%, and the rutting factor (G*/sinδ) increased by over 20%, indicating significant improvements in rheological stability and high-temperature performance. The integrated evaluation approach provided reliable and practical guidance for producing high-performance activated rubber asphalt. Full article

To study the mechanical properties and modification mechanism of thermosetting polyurethane (PU)-modified asphalt, the effects of polyurethane dosage on the workability of polyurethane-modified asphalt were analyzed by means of rotational viscosity tests. The mechanical properties of polyurethane-modified asphalt with different polyurethane dosages were explored using tensile tests and dynamic mechanical analysis (DMA). In addition, the thermodynamic behavior and micromorphology of polyurethane-modified asphalt were also thoroughly investigated using the test results of differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results showed that PU obtained the optimum workability when the polyurethane dose was 50%: at 120 min, its rotational viscosity was 1005 cp, which was lower than 2800 cp (40% PU) and 760 cp (60% PU). Additionally, the results of fracture elongation and fracture strength indicated that the PU-modified asphalt had good flexibility and strength. Compared with base asphalt, the tensile strength of 50% PU-modified asphalt increased by 509%, which was significantly higher than 157% (40% PU) and more balanced than 897% (60% PU) in terms of strength and flexibility. Added PU can significantly improve the elasticity of asphalt at high temperatures, while increasing the proportion of asphalt adhesive components, enhancing the deformation ability and temperature stability of asphalt. As the dose of PU increases, the interface between asphalt and PU blended more fully, and the surface became smoother. When the dose of PU was 50% or more, the interface between asphalt and PU was well integrated with a smooth and flat surface, forming a more uniform and stable cross-linked network structure. Full article

Bio-based polyurethane asphalt binder (PUAB) derived from castor oil (CO) is environmentally friendly and exhibits extended allowable construction time. However, CO imparts inherently poor mechanical performance to bio-based PUAB. To address this limitation, attapulgite (ATT) with fibrous nanostructures was incorporated. The effects of ATT on bio-based PUAB were systematically investigated, including cure kinetics, rotational viscosity (RV) evolution, phase-separation microstructures, dynamic mechanical properties, thermal stability, and mechanical performance. Experimental characterization employed Fourier transform infrared spectroscopy, Brookfield viscometry, laser scanning confocal microscopy, dynamic mechanical analysis, thermogravimetry, and tensile testing. ATT incorporation accelerated the polyaddition reaction conversion between isocyanate groups in polyurethane (PU) and hydroxyl groups in ATT. Paradoxically, it reduced RV during curing, prolonging allowable construction time proportionally with clay content. Additionally, ATT’s compatibilizing effect decreased bitumen particle size in PUAB, with scaling proportionally with clay loading. While enhancing thermal stability, ATT lowered the glass transition temperature and damping properties. Crucially, 1 wt% ATT increased tensile strength by 71% and toughness by 62%, while maintaining high elongation at break (>400%). The cost-effectiveness and significant reinforcement capability of ATT make it a promising candidate for producing high-performance bio-based PUAB composites. Full article

This study investigates the performance improvement of asphalt binders through the incorporation of two polymers, polyvinyl chloride (PVC) and styrene–butadiene–styrene (SBS), with asphalt grade (60–70), to address the growing demand for durable and climate-resilient pavement materials, particularly in areas exposed to high temperatures like Iraq. The main objective is to improve the mechanical characteristics, thermal stability, and workability of typical asphalt mixtures to extend pavement lifespan and lessen maintenance costs. A thorough set of rheological, physical, morphological, and workability tests was performed on asphalt binders modified with varying content of PVC (3%, 5%, 7%, and 9%) and SBS (3%, 4%, and 5%). The significance of this research lies in optimizing binder formulations to enhance resistance to deformation and failure modes such as rutting and thermal cracking, which are common in extreme climates. The results indicate that PVC enhances performance grade (PG), softening point, and viscosity, although higher contents (7% and 9%) exceeded penetration grade specifications. SBS-modified binders demonstrated marked improvements in softening point, viscosity, and rutting resistance, with PG values increasing from PG64-x (unmodified) to PG82-x at 5% SBS. Fluorescence microscopy confirmed optimal polymer dispersion at 5% concentration for both SBS and PVC, ensuring compatibility with the base asphalt. Workability testing revealed that SBS-modified mixtures exhibited higher torque requirements, indicating reduced workability compared to both PVC-modified and unmodified binders. These findings offer valuable insights for the design of high-performance asphalt mixtures suitable for hot-climate applications and contribute to the development of more durable and cost-effective road infrastructure. Full article

The research on nano titanium dioxide (nano-TiO₂)-modified asphalt has received increasing attention. However, further studies are required in order to ascertain the influence of the phenomenon under discussion on the rheological characteristics and ability to resist deformation of bitumen. In the present study, modified bitumen was formulated by adding nano titanium dioxide. Physical property tests, temperature scanning tests, frequency scanning tests, repeated creep recovery tests, bending creep stiffness tests, and long-term aging performance experiments were carried out on the specimen of asphalt that had undergone the process of modification in order to assess the rheological characteristics and ability to resist unrecoverable deformation of the modified bitumen at different temperatures, both high and low. The outcomes of the repeated creep recovery experiment were analyzed using Burgers and fractional derivative models. The microstructure of nano-TiO₂ high-viscosity modified asphalt was observed by Scanning Electron Microscope(SEM). In order to ascertain the manner in which base bitumen and nano-TiO₂ interact, Fourier transform infrared spectroscopy (FTIR) was utilized in the study. The results show that the thermal stability and prolonged aging resistant properties of the modified bitumen binder improved, but nano-TiO₂ made the asphalt binder weaker and more likely to crack at lower temperatures. Taking into account the variation in the road performance of the bitumen binder, 6% is recommended as the optimal amount of nano-TiO₂. Nano-TiO₂ was mainly uniformly distributed in asphalt and nano-TiO₂ was physically mixed with asphalt. In comparison with the Burgers model, the present fractional derivative empirical creep model can fit the creep test data of the asphalt binder well with the advantages of high accuracy and few parameters. The research results provide a reference for promoting the implementation of modified bitumen incorporating nano-TiO₂. Full article

An asphalt modifier dry-process direct-cast oil-rich high-viscosity high-elasticity (OR-HV-HE) was developed to address the climatic characteristics of seasonal freezing zones. The chemical composition of the OR-HV-HE modifier was optimized through orthogonal testing. Advanced characterization techniques, including thermogravimetric analysis (TG), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR), were employed to systematically analyze the comprehensive thermal properties, microstructure, and chemical characteristics of the OR-HV-HE asphalt. Test results revealed a linear inverse relationship between the melt index and the OR-HV-HE asphalt grafting rate. The addition of the OR-HV-HE modifier led to the generation of new chemical bonds, and microscopic mechanism analysis illustrated the formation of a cross-linking network structure between the OR-HV-HE and asphalt, in which the cross-linking network structure could enhance the high and low-temperature performance of asphalt. Road performance verification results demonstrated that when compared with the traditional SBS-modified asphalt mixture, the OR-HV-HE modified asphalt mixture exhibited significantly superior road performance indices: the high-temperature dynamic stability was increased by 468% and the low-temperature damage strain was increased by 47.5%, and the residual stability reached 99%. Full article

Most modified asphalts require high-temperature shearing and prolonged mixing to achieve a uniform structure, often resulting in substantial exhaust gas pollution. This study explores the utilization of polyurethane (PU) as a warm mix asphalt modifier, leveraging its favorable compatibility with asphalt at lower temperatures to mitigate emissions. To address the inherent limitations of PU-modified asphalt mixtures, namely, poor low-temperature performance and susceptibility to water damage, silane coupling agents (SCAs) are introduced to reinforce the asphalt–aggregate interfacial strength. At the microscopic level, the optimal PU content (20.8%) was determined through analysis of micro-viscosity and radial distribution functions (RDFs). SCA effects on interfacial properties were assessed using adhesion work, adhesion depth, and interfacial thermal stability. At the macroscopic level, performance metrics—including strength, high-temperature resistance, low-temperature resistance, and water stability—were evaluated against a benchmark hot mix SBS-modified asphalt mixture. The results indicate that PU-modified asphalts exhibit superior high-temperature performance and strength but slightly lower low-temperature performance and insufficient water stability. The addition of SCAs improved both low-temperature and water stability attributes, enabling the mixtures to meet specification requirements. The simulation results suggest that KH-550, which chemically reacts with isocyanate groups (-OCN) in PU, exhibits a better interfacial reinforcement effect than KH-570. Therefore, KH-550 is recommended as the preferred SCA for PU-modified asphalt mixtures in practical applications. Full article

Polyurethane asphalt (PUA) has attracted considerable attention in the field of pavement engineering. However, traditional PUA systems typically exhibit low concentrations of polyurethane (PU), leading to a continuous bitumen-dominated phase that adversely affects mechanical properties. Furthermore, the non-renewable nature of raw materials raises environmental concerns. To address these limitations, this study developed an eco-friendly and cost-efficient bio-based PUA binder (PUAB) featuring a continuous high-biomass PU matrix (over 70% biomass) and a high bitumen content (60 wt%). The effects of the isocyanate index (NCO/OH ratio) on the cure kinetics, rheological behavior (rotational viscosity over time), viscoelasticity, damping capacity, phase morphology, thermal stability, and mechanical performance were systematically investigated using Fourier-transform infrared spectroscopy, dynamic mechanical analysis, laser-scanning confocal microscopy, and tensile testing. Key findings revealed that while the rotational viscosity of PUABs increased with a higher isocyanate index, all formulations maintained a longer allowable construction time. Specifically, the time to reach 1 Pa·s for all PUABs at 120 °C exceeded 60 min. During curing, higher isocyanate indices reduced final conversions but enhanced the storage modulus and glass transition temperatures, indicating improved rigidity and thermal resistance. Phase structure analysis demonstrated that increasing NCO/OH ratios reduced bitumen domain size while improving dispersion uniformity. Notably, the PUAB with the NCO/OH ratio of 1.3 achieved a tensile strength of 1.27 MPa and an elongation at break of 238%, representing a 49% improvement in toughness compared to the counterpart with an NCO/OH ratio = 1.1. These results demonstrate the viability of bio-based PUAB as a sustainable pavement material, offering a promising solution for environmentally friendly infrastructure development. Full article

Rubber powder asphalt has been widely studied due to its favorable temperature sensitivity and fatigue resistance. However, because rubber powder does not easily swell in asphalt, it leads to poor storage stability and high viscosity, limiting its large-scale application. In this study, modified asphalt was prepared using desulfurized rubber powder (DRP) and styrene-butadiene-styrene (SBS) modifiers, aiming to identify the optimal formulation for enhanced performance. It was hypothesized that the combined use of DRP and SBS would produce synergistic effects, improving the overall mechanical and rheological properties of the asphalt. To test this, the effects of this composite modification were evaluated using Marshall tests (penetration, softening point, ductility, elastic recovery, and Brookfield viscosity) and Superpave tests (shear modulus, high-performance grade, rutting factor, fatigue factor, and creep and recovery). Additionally, moisture susceptibility, high-temperature stability, low-temperature cracking resistance, and fatigue resistance at the mixture level were assessed. Performance was evaluated according to the Chinese standard JT/T 798-2019 for rubberized asphalt using reclaimed tire rubber. Results show that DRP-modified asphalt demonstrates excellent temperature sensitivity, rutting resistance, deformation resistance, and fatigue performance. However, an excessive amount of DRP increases Brookfield viscosity, which negatively affects the workability of the asphalt binder. The addition of SBS further improves the softening point, ductility, and deformation recovery of the binder. Considering cost-effectiveness and overall performance, the optimal formulation was determined to be 25% DRP and 1% SBS. At this dosage, all performance indicators met the required standards. The rotational viscosity at 180 °C was approximately 35% lower than that of conventional rubber powder–modified asphalt, while the high-temperature rutting factor and fatigue resistance at medium-to-low temperatures outperformed those of SBS-modified asphalt. The mixture test results reveal that the gradation has an impact on the performance of the obtained mixture, but overall, the DRP-SBS composite-modified asphalt mixture has significant advantages in terms of performance and cost-effectiveness. Full article