Search Results (48)

In order to solve various problems in traditional roads and extend their service life, new road materials have become a research hotspot. Polyurethane prepolymers (PUPs) and ceramic fibers (CFs), as materials with unique properties, were chosen due to their synergistic effect: PUPs provide elasticity and gel-like behavior, while CFs contribute to structural stability and high-temperature resistance, making them ideal for enhancing asphalt performance. PUPs, a thermoplastic and elastic polyurethane gel material, not only enhance the flexibility and adhesion properties of asphalt but also significantly improve the structural stability of composite materials when synergistically combined with CF. Using response surface methodology, an optimized preparation scheme for PUP/CF composite-modified asphalt was investigated. Through aging tests, dynamic shear rate (DSR) testing, bending rate (BBR) testing, microstructure scanning (MSCR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and infrared spectroscopy (IR), the aging performance, rheological properties, permanent deformation resistance, microstructure, and modification mechanism of PUP/CF composite-modified asphalt were investigated. The results indicate that the optimal preparation scheme is a PUP content of 7.4%, a CF content of 2.1%, and a shear time of 40 min. The addition of the PUP and CF significantly enhances the asphalt’s aging resistance, and compared with single-CF-modified asphalt and base asphalt, the PUP/CF composite-modified asphalt exhibits superior high- and low-temperature rheological properties, demonstrating stronger strain recovery capability. The PUP forms a gel network structure in the material, effectively filling the gaps between CF and asphalt, enhancing interfacial bonding strength, and making the overall performance more stable. AFM microscopic morphology shows that PUP/CF composite-modified asphalt has more “honeycomb structures” than matrix asphalt and CF-modified asphalt, forming more structural asphalt and enhancing overall structural stability. This study indicates that the synergistic effect of PUP gel and CF significantly improves the macro and micro properties of asphalt. The PUP forms a three-dimensional elastic gel network in asphalt, improving adhesion and deformation resistance. Using response surface methodology, the optimal formulation (7.4% PUP, 2.1% CF) improves penetration (↓41.5%), softening point (↑6.7 °C), and ductility (↑9%), demonstrating the relevance of gel-based composites for asphalt modification. Full article

To elucidate the modification mechanism of waterborne polyurethane (WPU) on emulsified asphalt, anionic and cationic WPUs are utilized as modifiers. As well, their effects on physical properties, microstructure, and compatibility are characterized using basic performance tests, Fourier transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM). The results show that WPU-modified emulsified asphalt exhibited a higher softening point, reduced penetration, and decreased ductility, suggesting enhanced high-temperature stability but diminished low-temperature flexibility. Among all samples, the combination of cationic WPU with cationic emulsified asphalt shows the highest softening point (54.1 °C), whereas cationic emulsified asphalt alone exhibits the lowest one (52.9 °C). Anionic emulsified asphalt demonstrates the highest penetration (79 mm), while non-ionic WPU combined with cationic emulsified asphalt shows the lowest one (59.3 mm). The ductility decreases from 90.3 cm to 28.7 cm. The storage stability varies with WPU ion type. Cationic WPU-modified samples showed the poorest storage stability (0.7% residue), while anionic-modified samples exhibit the best one (0.4% residue). FTIR analysis confirms the presence of characteristic WPU absorption peaks, indicating that physical blending occurs, and chemical interaction is limited. AFM observations reveal that anionic WPUs provide superior compatibility, forming fine, uniformly distributed particles with the lowest surface roughness (5.655 nm). In contrast, cationic WPUs form chain-like structures that cure effectively but exhibit poor dispersion. This study provides a basis for the development of high-performance WPU-modified emulsified asphalt. 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

In this study, an investigation on using polyurethane/graphene oxide (PU/GO) containing disulfide bonds as a modifier to improve the self-healing ability of asphalt was conducted. PU/GO with different GO contents were synthesized and modified asphalt with different PU/GO dosages (2%, 4%, 6%, 8%) were also prepared. The effect of GO contents on the mechanical and self-healing properties of PU/GO was explored and the impacts of PU/GO contents on the basic properties and self-healing properties of asphalt were also investigated. The results indicated that GO could significantly improve the mechanical properties of PU, as the tensile strength of PU/GO with 1.6% GO increased by more than 100% compared with pure PU. Moreover, GO also had a positive impact on the early-stage self-healing properties of PU/GO. PU/GO could be well dispersed in asphalt and clearly improve the low-temperature performance of base asphalt. When the PU/GO content is 8%, the ductility of modified asphalt was almost 6 times that of base asphalt. The results of both ductility and BBR self-healing tests revealed that the addition of PU/GO improved the self-healing properties of asphalt under room temperature and infrared light conditions. Especially under infrared light conditions, the ductility self-healing coefficient of 8% PU/GO-modified asphalt could reach 100% after healing for 15 min. Full article

Polyurethane (PU) materials, with their excellent mechanical properties, durability, and fatigue resistance, hold promise for addressing the challenges of aging, environmental pollution, and segregation during the storage of modified asphalt mixtures, thereby extending the lifespan of pavements and enhancing the level of service. Although studies have been conducted on the road performance of PU mixtures that compared them with asphalt mixtures, there is relatively less research on how the air void of PU mixtures affects their performance. This study systematically investigates the dynamic characteristics and road performance of dense-graded PU mixtures at three air void ranges—1%–3%, 3%–5%, and 5%–7%—and verifies the effectiveness through statistical methods. The research results show that air voids have a significant impact on road performance. Compared to low air voids, high air voids can increase high-temperature performance by 12%–33%. However, higher air voids also lead to a significant decrease in resistance to water damage, with a reduction of about 9%–24%. When the air void is in the range of 3%–5%, the mixture has better dynamic stability. Therefore, when designing PU mixtures, a reasonable air void should be selected based on engineering conditions to achieve the optimal pavement structure combination and save investment. This study provides a scientific basis for the design and application of PU mixtures and lays the foundation for further understanding of their performance mechanisms. Full article

The superior mechanical qualities of polyurethane have garnered increasing attention for its application in modifying asphalt mixtures. However, polyurethane needs to use polyols to cure, and polyols need to be produced by petroleum refining. As we all know, petroleum is a non-renewable energy source. In order to reduce oil consumption and conform to the trend of a green economy, lignin and chitin were used instead of polyols as curing agents. In this paper, a biological polyurethane-modified asphalt mixture (BPA-16) was designed and compared with a polyurethane-modified asphalt mixture (PA-16) and a matrix asphalt mixture (MA-16). The viscoelastic characteristics of the three asphalt mixtures were evaluated using dynamic modulus, static modulus, and creep tests. The interplay between dynamic and static modulus and frequency is examined, along with the variations in the correlation between dynamic and static modulus. The creep behavior of the mixture was ultimately examined by a uniaxial static load creep test. The findings indicate that the dynamic modulus of BPA-16 exceeds those of PA-16 and MA-16 by 8.7% and 30.4% at 25 Hz and −20 °C, respectively. At 25 Hz and 50 °C, the phase angle of BPA-16 decreases by 26.3% relative to that of MA-16. Lignin and chitin, when utilized as curing agents in place of polyol, can enhance the mechanical stability of asphalt mixtures at low temperatures and diminish their temperature sensitivity. A bio-based polyurethane-modified asphalt mixture can also maintain better elastic properties in a wider temperature range. At −20–20 °C, the dynamic and static moduli of BPA-16, PA-16 and MA-16 are linear, and they can be converted by formula at different frequencies. The failure stages of BPA-16, PA-16, and MA-16 are not observed during the 3600 s creep duration, with BPA-16 exhibiting the least creep strain, indicating that lignin and chitin enhance the resistance to permanent deformation in PU-modified asphalt mixes. Full article

Firstly, thermoplastic polyurethane recycled material (TPRM) particles were used to prepare modified asphalt. Then, the modified asphalt’s physical properties were investigated. The results show that the TPRM particles improved its high-temperature performance, low-temperature crack resistance, and shear behavior due to its increased cohesion and low-temperature fracture energy levels. Thermal susceptibility was affected by the degree of swelling and dissolution of the TPRM particles, the composition of the asphalt, and the interface effect between the asphalt molecules and both the regular and slender–irregular TPRM particles. The TPRM particles swelled and dissolved after absorbing the light components of asphalt. Changes in the shearing temperature and time made the TPRM particles swell and dissolve more than changes in the activation temperature and time. An increase in the shearing/activation temperature and time increased the hydrogen bond content in the modified asphalt due to the rearrangement of the polyurethane’s molecular structure and the hydrogen bonds formed by the asphaltene and polyurethane molecules. Slender–irregular TPRM and “sea–island” and hilly and gulley structures were found in the modified asphalt matrix. Full article

To explore the influence of the polyurethane blending ratio on the micro-characteristics of polyurethane-modified asphalt, three samples of the modified asphalt with different blending ratios (40%, 50%, and 60%) were prepared. Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and scanning electron microscopy (SEM) were employed to elucidate the modification mechanism of polyurethane-modified asphalt. To investigate how the preparation method affects the performance of polyurethane-modified asphalt mixtures, two different preparation methods, namely internal blending and external blending, were adopted. The road performance of the polyurethane-modified asphalt mixtures was evaluated through the utilization of rutting tests, low-temperature trabecular bending tests, and freeze–thaw splitting tests. The FTIR test results indicate that during the modification of polyurethane, there is a change in both the intensity and position of the absorption peak, which affects the local arrangement of the molecular structure. Upon reaching a polyurethane blending ratio of 50%, a cross-linked network structure that is similar to polyurethane is formed. The results of the AFM test demonstrate that an increase in polyurethane content results in a corresponding increase in surface roughness. At a polyurethane content of 50%, the curing reaction is most effective, which is beneficial for enhancing the bonding performance between the asphalt and the aggregate, thereby enhancing the overall water stability of the mixture. The results of the scanning electron microscopy (SEM) tests indicate that the microstructure is more stable when the polyurethane content is 50%. The results of the performance test of the polyurethane-modified asphalt mixture indicate that the dynamic stability of the polyurethane-modified asphalt mixture is approximately four times that of the SBS-modified asphalt mixture. The flexural tensile strength and maximum flexural strain of the polyurethane-modified asphalt mixture are, respectively, 1.5 and 3.2 times those of the SBS-modified asphalt mixture, indicating that its anti-deformation ability is stronger in a low-temperature environment, and it is found that the low-temperature performance of the mixture prepared with the internal blending method is better than that with the external blending method. The splitting strength of the polyurethane asphalt mixture before and after freezing and thawing is greater than that of an SBS asphalt mixture: before freezing and thawing, by about 3.8 times; after freezing and thawing, by about 3 times. Although the freezing and thawing of the polyurethane mixture has damage, it still meets the requirements of the use of pavement materials. It can be observed that the incorporation of polyurethane alters the internal structure of the asphalt, which markedly enhances the properties of the asphalt mixture and offers a novel perspective on the development of modified asphalt materials. Full article

In research aimed at improving the brittleness of WER (waterborne epoxy)-modified emulsified asphalt, commonly encountered issues are that the low-temperature performance of this type of asphalt becomes insufficient and the long curing time leads to low early strength. Matrix-emulsified asphalt was modified with WPU (waterborne polyurethane), WER, and DMP-30 (accelerator). Firstly, the performance changes of modified emulsified asphalt at different single-factor dosages were explored through conventional performance tests and assessments of its adhesion, tensile properties, and curing time. Secondly, based on a response surface methodology test design, the material composition of the composite-modified emulsified asphalt was optimized, and its rheological properties were analyzed by a DSR test and a force–ductility test. Finally, the modification mechanism was explored by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results show that WER can improve the adhesion strength of modified emulsified asphalt and greatly reduce elongation at break. WPU can effectively improve the elongation at break of composite-modified emulsified asphalt, but it has a negative impact on adhesion strength. DMP-30 mainly affects the curing time of modified emulsified asphalt; EPD (composite modification) can effectively improve the high-temperature rutting resistance of matrix-emulsified asphalt, and its low-temperature performance is significantly improved compared with WER-modified emulsified asphalt. The EPD modification process mainly consists of physical blending. In the case of increasing the curing rate, it is recommended that the contents of WER and WPU be lower than 10% and 6%, respectively, to achieve excellent comprehensive performance of the composite modification. Full article

Fatigue performance and self-repairing activity of asphalt binders are two properties that highly influence the fatigue cracking response of asphalt pavement. There are still numerous gaps in knowledge to fill linked with these two characteristics. For instance, current parameters fail to accommodate these two bitumen phenomena fully. This study aims to propose a new procedure to address this issue utilizing the linear amplitude sweep (LAS) test, LAS with rest period (RP) (LASH) test, and simplified viscoelastic continuum damage (S-VECD) model. This research work used four different types of asphalt binders: neat asphalt (NA), self-healing thermoplastic polyurethane (STPU)-modified bitumen (STPB), self-healing poly (dimethyl siloxane) crosslinked with urea bond (IPA1w)-modified bitumen (IPAB), and styrene–butadiene–styrene (SBS)-modified bitumen (SBSB). Before the testing process, all the materials were subjected to short-term and long-term aging. The new procedure showed a superior capacity to analyze and accommodate all bitumen fatigue performances and self-repairing activities compared to the current method. Another finding proved that asphalt binders with a higher self-restoration behavior failed to show a better fatigue performance. Moreover, the higher fatigue performance increments produced by STPU and IPA1w in NA concerning the control bitumen were 123.7% and 143.7%, respectively. Those values were obtained with 1.0% STPU and 0.5% IPA1w in NA. A breakthrough finding demonstrated that asphalt binder fatigue response is augmented when the RP was applied at a higher damage intensity (S) value. STPB and IPAB reached their highest increments of fatigue response, containing 1.0% of STPU and 0.5% of IPA1w, respectively. Those augmentations were 207.54% and 232.64%, respectively. Full article

To enhance the service life of traditional asphalt pavement and mitigate issues such as high-temperature rutting and low-temperature cracking, this study investigates the composite modification of matrix asphalt using thermoplastic polyurethane (TPU) and styrene-butadiene rubber (SBR). Initially, the study examines the conventional properties of the composite-modified asphalt from a macro perspective, analyzing the performance variations of asphalt before and after TPU and SBR modification. Subsequently, microscopic analysis is conducted to explore the microstructure, phase structure, and modification mechanisms of the composite-modified asphalt, with a focus on understanding the underlying reasons for performance changes. The influence of TPU and SBR on asphalt performance is evaluated comprehensively. It is found that TPU-modified asphalt demonstrates superior high-temperature performance, storage stability, and elastic recovery. Conversely, SBR-modified asphalt excels in ductility at low temperatures, though its storage stability decreases with increasing dosage. Based on a thorough analysis of the conventional properties of the two types of modified asphalt, the optimal dosages of TPU and SBR are determined to be 15% and 3.5%, respectively. In the composite-modified asphalt, TPU facilitates the even distribution of chemical components, creating a more stable cross-linked network structure. The compatibility of TPU, SBR, and asphalt contributes to the good storage stability of the composite-modified asphalt. While SBR effects physical modification, TPU induces chemical modification of asphalt. Consequently, the composite modification system benefits from both physical and chemical enhancements, resulting in excellent overall performance. Full article

To address the issue of insufficient durability of traditional modified emulsified asphalt in the application of cold mix and cold paving anti-skid wear layers, this study utilizes cationic waterborne polyurethane (PU+) for composite modification to enhance adhesion and performance across a range of temperatures. Initially, composite-modified emulsified asphalt samples were prepared with varying dosages of PU+ according to a gradient method. Routine performance tests were conducted on the evaporated residues for analysis. Advanced rheological tests, including temperature sweep (TS), frequency sweep (FS), linear amplitude sweep (LAS), and multi-stress creep recovery (MSCR) tests, were performed using a dynamic shear rheometer (DSR). Surface free energy (SFE) tests were conducted with a fully automated surface tension meter (STM). A comprehensive evaluation of the high-temperature rheological properties, fatigue properties, adhesion properties, and water damage resistance of the modified emulsified asphalt residues was carried out. Chemical changes before and after modification were characterized using Fourier transform infrared spectroscopy (FTIR), and the distribution of polymers in the evaporated residue was observed using fluorescence microscopy (FM). The results demonstrated that cationic waterborne polyurethane significantly enhanced the fatigue and adhesion properties of SBS-modified emulsified asphalt, but it also weakened the water damage resistance of asphalt. MSCR tests revealed that the addition of cationic waterborne polyurethane might reduce the elastic recovery performance of modified asphalt, thereby weakening its resistance to rutting. Among the samples, the modified asphalt with a PU+ content of 6% exhibited good high-temperature shear resistance and elastic recovery performance, demonstrating the best anti-rutting performance. Full article

Microbial corrosion of waterproof coatings causes structural damage to buildings and renovation materials and severely threatens human health. In practical applications, coatings with different base materials show different durabilities to external environmental influences. There is little literature on the antimicrobial durability performance of waterproof coatings. Therefore, this paper selected four standard waterproofing coatings, including polyurethane coatings, cement-based coatings, asphalt-modified polymer coatings, and polymer emulsion coatings, as the main body of this study. Their antimicrobial abilities against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus, Candida albicans, and mold were tested after experiencing three kinds of harsh environments: Ultraviolet ray (UV), water immersion, and low temperature. The results show that the extreme climates significantly reduced the ability of the four coatings to resist mold, and the highest growth rate of bacteria was 54.64%. Under UV conditions, the polymer emulsion coatings were significantly more resistant to Candida albicans, and the optical density of the bacterial liquid showed a negative growth trend. The microstructural integrity of the polymer emulsion coatings was found to be damaged by Scanning Electron Microscope (SEM) observation. This work improves the durability application research on these coatings and provides a valuable reference for developing new environmentally friendly, antibacterial, and anticorrosive waterproof coatings. Full article

The high-performance, cleaner rejuvenation of aged SBS-modified asphalt mixtures (ASBSMAMs) has been a hotspot in asphalt research. Currently, the most popular rejuvenation method still involves hot-mix asphalt with a commonly used oil as the rejuvenator for recycling. However, high-quality, cleaner warm-mix rejuvenation technology for ASBSMAMs is still needed to enrich this field. This study considered adopting a polyurethane (PU) prepolymer and 1,4-butanediol diglycidyl ether (BUDGE) as reactive rejuvenators to achieve warm-mix reaction–rejuvenation to enhance the properties of ASBSMAMs with the use of a wax-based additive, Sasobit. A series of tests were conducted to realize this, including the viscosity–temperature correlation of the rejuvenated binders, as well as tests of the moisture-induced damage, high-temperature stability, low-temperature cracking resistance, and fatigue resistance of the rejuvenated mixtures. The results showed the following: through reaction–rejuvenation, Sasobit could reduce the viscosity of the rejuvenated SBSMA (RSBSMA) below 150 °C for warm mixing and slightly decrease the viscosity–temperature susceptibility; warm-mix reaction–rejuvenation helped to improve the resistance to water-immersion-induced damage and freeze–thaw damage in ASBSMAMs; the addition of Sasobit showed benefits in improving their resistance to permanent deformation, with the dynamic stability values exceeding 5700 pass/mm as more than 1% Sasobit was added; the flexural damage resistance of ASBSMAMs at low temperatures could be enhanced after warm-mix reaction–rejuvenation; and, under reaction–rejuvenation conditions, Sasobit did not reduce the fatigue resistance of the RSBSMAM and, conversely, at limited higher dosages, it worked more effectively. Overall, the studied warm-mix reaction–rejuvenation technology has been proven to be effective for the environmental recycling and reuse of ASBSMAMs at high quality. Full article

A full understanding of bitumen fatigue cracking behavior is extremely important as this phenomenon has a considerable influence on bituminous pavement performance. The current framework for assessing this asphalt binder property is inconsistent in ranking bitumen fatigue performance in terms of the failure definition and damage characteristic curve (DCC) analysis. This study used four different types of asphalt binders: neat asphalt (NA), self-healing thermoplastic polyurethane (STP)-modified bitumen, self-healing poly (dimethyl siloxane) crosslinked with urea bond (IPA1w)-modified bitumen, and styrene–butadiene–styrene (SBS)-modified bitumen (SBSB). All the bitumens were subjected to short-term and long-term aging, and they were also tested by utilizing the linear amplitude sweep (LAS) test and the simplified viscoelastic continuum damage (S-VECD) model. LAS and S-VECD procedures were used to apply the newly proposed and current frameworks in order to analyze bitumen performance. The current framework showed that the bitumens that used a higher number of loading cycles (N) to reach their failure points ($N_f$) failed to exhibit greater fatigue performances in terms of DCC analysis. The developed framework (mainly based on the damage intensity [S] instead of N) was used to solve the inconsistency between the failure definition and DCC assessment in ranking bitumen performance. Additionally, the current framework (failure criterion) presented two R² values below 0.1, but the developed framework (failure criterion) showed that all R² values were greater than 0.9. The developed framework represents a turning point because, for the first time, this type of procedure is mainly being based on S instead of N. Although further tests are needed to confirm its efficiency, it eliminates the inconsistency between the failure definition and DCC assessment. Full article