Search Results (116)

With the rapid increase in plastic consumption, waste polypropylene (WPP) has become one of the major components of municipal solid waste, posing significant environmental and resource challenges. According to statistics, polypropylene accounts for approximately 19.1% of the total global plastic waste, posing significant environmental challenges. In recent years, the recycling and reuse of WPP in asphalt pavement materials have received increasing attention due to its excellent mechanical properties, thermal stability, and low cost. This review systematically summarizes the physicochemical properties and recycling technologies of WPP, including mechanical, chemical, and energy recovery routes. Furthermore, the modification mechanisms, preparation methods, and performance characteristics of WPP-modified asphalt binders and mixtures are comprehensively discussed, focusing on their high-temperature stability, compatibility, low-temperature cracking resistance, and anti-moisture damage. Research indicates that WPP modification significantly enhances high-temperature rutting resistance, and thermo-chemical modifiers have successfully enabled the application of WPP in warm-mix asphalt. This review uniquely integrates recent advances in thermo-mechanochemical upcycling with mixture-level performance, bridging molecular design and field application. However, critical challenges, including poor compatibility, insufficient storage stability, and the lack of a unified assessment for the high variability of WPP raw materials, still need to be addressed. Finally, this review primarily focuses on the recycling technologies of WPP, its modification mechanisms in asphalt binders, and the resulting impact on the pavement performance of WPP-modified mixtures. Full article

The complex nonlinear interplay between preparation parameters and macroscopic properties poses challenges for predicting the performance of anti-aging rubber asphalt. To address this, two bio-inspired algorithms—Crested Porcupine Optimizer (CPO) and Dung Beetle Optimizer (DBO)—were integrated with a backpropagation (BP) neural network, forming CPO-BP and DBO-BP hybrid models for multi-target prediction. The CPO-BP model demonstrated superior predictive accuracy, significantly outperforming both the standard BP and DBO-BP models, which is attributed to its adaptive global-local optimization mechanism. Shapley additive explanations (SHAP) analysis identified mixing temperature as the most influential factor, with elevated values enhancing rutting resistance but compromising ductility, while moderate temperatures improved aging resistance. Feature interactions indicated synergistic effects between mixing temperature and shear time, and a strong coupling effect between rubber content and temperature on low-temperature performance. Parameter optimization via Non-dominated Sorting Genetic Algorithm II (NSGA-II) further enhanced high–low temperature stability and aging resistance, confirmed by Atomic Force Microscopy (AFM)-based microstructural characterization. The proposed approach provides a robust framework that integrates data-driven prediction and multi-objective optimization for the rational design of high-performance anti-aging rubber asphalt. Full article

Conventional rubber-modified asphalt typically suffers from low rubber content and requires high construction temperatures. This study developed a warm-mix high-content crumb-rubber-modified asphalt (CRMA) with an increased rubber particle content of over 20%; moreover, the optimization of the warm-mixing agent was determined. Its rutting and cracking resistance performances were investigated using a dynamic shear rheometer (DSR) and a bending beam rheometer (BBR). Fourier Transform Infrared (FTIR) and Atomic Force Microscopy (AFM) were used to characterize the aging resistance and microstructural characteristics. The key findings revealed that the optimal dosage of the SDYK-type warm-mix additive (SDYK; a surfactant used to improve the high-temperature stability, low-temperature crack resistance, and anti-aging performance of asphalt) was 0.6% for high-rubber-content CRMA. The combination of warm-mix additives and rubber granules enhanced the aging resistance and elasticity of the asphalt while also contributing to an increase in chemical functional group indicators. The decrease in both the aliphatic chain index and branched alkane index of CRMA indicates that the warm-mix agent and the rubber additive enhanced the aging resistance of the asphalt. The warm-mix agent reduced the roughness of the asphalt, counteracting the roughness-enhancing effect of crumb rubber. This was attributed to the lubrication effect induced by the water film during the mixing process, which promotes a more uniform distribution of the rubber crumb network. This research established a theoretical and experimental basis for the application of high-rubber-content CRMA in large-temperature-difference regions. Full article

Asphalt is a widely used polymeric material in pavement engineering. However, it is easily affected by heat and ultraviolet rays, which accelerate its molecular degradation and physicochemical aging, thereby limiting its service life. To improve the anti-aging properties of asphalt, three types of nano-zinc oxide (ZnO)-modified asphalt were prepared. The chemo-rheological behavior, structural evolution of polymeric components, molecular weight distribution, and nanoscale morphology of nano-ZnO-modified asphalt were studied via dynamic shear rheometry (DSR), Fourier transform infrared spectrometry (FTIR), gel permeation chromatography (GPC) and atomic force microscopy (AFM), and the aging resistance of nano-ZnO-modified asphalt was quantitatively analyzed using the rutting factor index, functional group index, molecular size ratio, and nanoscale parameters. The findings indicate that nano-ZnO enhances the high-temperature rheological properties of asphalt and delays the increase in the rutting factor of aged asphalt. Nano-ZnO is dispersed in the asphalt matrix in the form of a physical mixture without inducing new chemical bonds, and can reduce the nanoscale roughness of asphalt. After aging, the nanoscale roughness and the aspect ratio of the bee structure decreased, and the bee structure area increased. According to the changes in the functional group index and the proportions of molecular sizes in the asphalt, it was found that nano-ZnO can significantly improve asphalt’s aging resistance. The results of this study provide insights into the nanoscale modification and structure–property relationships of polymeric asphalt binders, providing a reference for the design and application of functional polymer nanocomposite systems with improved durability. Full article

In order to accurately characterize the temperature dependence of the high-temperature performance of asphalt pavement surface layer materials, this paper studies the effects of temperature, load, and number of actions on the high-temperature anti-rutting performance of asphalt pavement surface layer materials (AC-13 and AC-16 mixtures), based on indoor rutting tests, and constructs a high-temperature performance temperature-dependent model and rutting prediction model for surface layer materials. The results show that as the temperature increases, the dynamic stability of the mixture decreases in an S-shaped curve, and the rut depth increases exponentially. The temperature-dependent model transition temperatures for the dynamic stability of 70#, 50#, 30#, SBS, and HMB asphalt mixtures are 39 °C, 44 °C, 46 °C, 56 °C, and 56 °C, respectively. The dynamic stability of modified asphalt mixtures is significantly higher than that of base asphalt mixtures. The depth of wheel ruts is affected by temperature, load, and the number of actions. The variation ranges of the load index k_P, the temperature index k_T, and the number of actions index k_N are 0.727–1.222, 1.926–2.177, and 0.133–0.295, respectively. The correlation coefficients of the wheel rut prediction model are all above 0.95, and the depth of wheel ruts can be predicted by the model. Full article

This paper presents a comprehensive review of the environmentally friendly management and reutilization of electronic waste (e-waste) plastics in flexible pavement construction. The discussion begins with an overview of e-waste management challenges and outlines key recycling approaches for converting plastic waste into asphalt-compatible materials. This review then discusses the types of e-waste plastics used for asphalt modification, their incorporation methods, and compatibility challenges. Physical and chemical treatment techniques, including the use of free radical initiators, are then explored for improving dispersion and performance. Additionally, in situations where advanced pretreatment methods are not applicable due to cost, safety, or technical constraints, the application of alternative approaches, such as the use of low-cost complementary additives, is discussed as a practical solution to enhance compatibility and performance. Finally, the influence of e-waste plastics on the conventional and rheological properties of asphalt binders, as well as the performance of asphalt mixtures, is also evaluated. Findings indicate that e-waste plastics, when combined with appropriate pretreatment methods and complementary additives, can enhance workability, cold-weather cracking resistance, high-temperature anti-rutting performance, and resistance against moisture-induced damage while also offering environmental and economic benefits. This review highlights the potential of e-waste plastics as sustainable asphalt modifiers and provides insights across the full utilization pathway, from recovery to in-field performance. Full article

As the global demand for electronic equipment continues to grow, many devices are being replaced more frequently, resulting in a rapid rise in electronic waste (e-waste), now the fastest growing waste stream worldwide. Motivated by this, the objective of this study is to present an environmentally friendly method to recycle acrylonitrile–butadiene–styrene (ABS), one of the most common e-waste plastics, by using it for asphalt production. In contrast to earlier methods of plastic-modified asphalt production involving complex pretreatments or complimentary additives unsuitable for plant-scale use, this study aims to demonstrate a practical, low-cost solution through the use of carbon black. This approach included physically pretreating ABS plastics for size reduction and incorporating waste tire-derived carbon black to promote effective dispersion in asphalt during wet modification. The rheological properties of the e-waste-modified asphalt were subsequently assessed. The test results indicated that recycling ABS plastics with a blending content of 5% alongside 5% carbon black can enhance cold-weather cracking resistance and high-temperature anti-rutting performance of asphalt. The enhancement can be attributed to the proper preparation procedures of ABS plastics and the addition of carbon black, which can further improve the performance by promoting the proper dispersion of plastic particles in asphalt. The outcome of this study indicates that recycling e-waste plastics through asphalt production can lead to more green and sustainable asphalt construction, reduce total construction costs, and most importantly enhance performance. Full article

Prolonged ultraviolet (UV) exposure accelerates aging and degradation, while conventional constant-intensity UV simulations do not reflect the variable nature of outdoor radiation. Aging duration and film thickness are both key factors affecting Rubber-Modified Asphalt (RMA), but how their combination influences RMA remains unclear. To address this limitation, this research employed accelerated aging experiments under variable-intensity UV radiation to investigate the performance and aging mechanism of RMA across different aging durations and asphalt film thicknesses. Rheological properties were analyzed through rheological tests, and the UV aging mechanisms of RMA were revealed using FTIR and SEM. The results revealed that crumb rubber improved RMA’s UV aging resistance, including high-temperature performance, fatigue life, and low-temperature cracking resistance. Aging effects were more influenced in RMA with thinner films under prolonged UV exposure. After nine cycles of ultraviolet aging, the rutting resistance, elastic recovery, fatigue life, and low-temperature cracking resistance of RMA with a 1 mm film thickness were 1.33, 1.11, 0.54, and 0.67 times, respectively, those of RMA with a 2 mm film thickness subjected to three UV aging cycles. RMA demonstrated comparable high-temperature performance and elastic recovery under UV aging conditions corresponding to a 1.5 mm film thickness aged for three cycles and a 2.0 mm film thickness aged for six cycles, as well as a 1.0 mm film thickness aged for six cycles and a 1.5 mm film thickness aged for nine cycles. FTIR showed that the increased activity of C=C and C-H under photo-oxidative aging caused a greater impact on the carbonyl groups than the sulfoxide groups. Under high-intensity UV radiation, RMA with thinner films exhibited greater rubber powder detachment, increased surface oxidation, and a substantial widening of cracks. The rubber powder absorbed UV radiation, enhancing the stability of RMA. The maximum crack width of the 1 mm NA was twice that of RMA. These provided insight into the microstructural pattern of cracking resistance degradation caused by aging. This research provides theoretical support for the optimization of the anti-aging performance of RMA. Full article

This paper aims to explore the influences of the content and gradation of mineral powder on the rheological properties of styrene-butadiene-styrene (SBS) modified asphalt mastic at different aging stages and temperatures. In the experiment, SBS modified asphalt mastic samples with different powder-to-binder ratios (0.6, 0.8, and 1.0) and different mineral powder gradations (500 mesh passing rates of 76.89% and 100%) were prepared. Following aging periods of 5, 25, and 45 h in the pressure aging vessel (PAV), the asphalt underwent comprehensive rheological characterization using a dynamic shear rheometer (DSR). The research shows that mineral powder can boost mastic’s deformation resistance and elastic effect. When aged by PAV for 45 h, the powder-to-binder ratio increased from 0.6 to 1.0, and its complex modulus increased by nearly 2.5 times at 58 °C. For SBS modified asphalt mastic of PAV 0 h, the powder-to-binder ratio increased from 0.6 to 1.0 and its phase angle was reduced from 59.6 to 53.2, which indicated that the elasticity of mastic was improved. However, this accelerated the degradation rate of SBS, making the aging process more complex. Fine-grained mineral powder is more effective in enhancing mastic’s deformation resistance than coarse-grained mineral powder. The fine-graded mastic had better rutting resistance after 45 h of aging than after 25 h of aging because the mineral powder compensated for the SBS loss-induced elasticity reduction. Smaller mineral powder particles lead to better a mastic anti-aging effect. After 45 h of aging, fine-grained mineral powder offered a better elastic effect. But the ways in which mineral powder and SBS boost mastic elasticity differ greatly. The results of this study provide a reference for optimizing the design of asphalt mixtures. Full article

The objective of this study is to explore the high-temperature rheological properties and microscopic interaction mechanisms of styrene–butadiene–styrene (SBS) composite-modified asphalt with hydroxylated multi-walled carbon nanotubes (MWCNT-OH). SBS-modified asphalt, MWCNT-modified asphalt and MWCNT/SBS composite-modified asphalt were prepared with high-speed shearing apparatus and machine mixer. Physical property tests, dynamic shear rheological (DSR) tests, multiple stress creep recovery (MSCR) tests, X-ray diffraction (XRD) and Raman spectroscopy analyses were carried out to systematically compare the differences in macroscopic performance and changes in microscopic structure of different types of asphalts. According to the results of physical property tests, DSR tests and MSCR tests, the composite-modified asphalt was superior to the single-component-modified asphalt in terms of complex modulus (G*) and rutting factor (G*/sin δ). Its creep recovery rate (R) and unrecoverable compliance (Jnr) exhibited better anti-deformation ability under high temperatures, verifying the synergistic effect of SBS and MWCNTs-OH. XRD analysis showed that composite modification reduced the disorder degree of the crystalline phase of asphalt. Raman spectroscopy confirmed that there were changes in the vibration of chemical bonds between the modifier and asphalt, indicating that the modifier and asphalt acted on the asphalt system through physical dispersion and chemical cross-linking. Full article

Endothelial cells play a crucial role in cardiovascular health by maintaining vascular homeostasis, regulating blood flow and vascular wall permeability, and protecting against external stressors. Oxidative stress, particularly excessive reactive oxygen species (ROS), disrupts cellular homeostasis and contributes to endothelial cell dysfunction. Rutaecarpine (RUT), an indolopyridoquinazolinone alkaloid isolated from Evodia rutaecarpa, has cytoprotective potential. However, the molecular mechanism underlying its cytoprotective activity in endothelial cells remains unclear. In this study, we investigated the protective effects of RUT against H₂O₂-induced apoptosis in human EA.hy926 endothelial cells and explored its underlying mechanism of action. RUT enhanced nuclear factor erythroid 2-related factor 2 (Nrf2) activation by increasing its expression and phosphorylation, resulting in the upregulation of antioxidant enzymes (GCLC, NQO1, and HO-1). RUT increased the level of the anti-apoptotic marker (Bcl-2) while inhibiting apoptotic markers (cleaved caspase-3 and Bax) in H₂O₂-induced apoptotic cells. Mechanistic analysis revealed that RUT activates Nrf2 through two pathways: TRPV1-mediated PKCδ/Akt phosphorylation and aryl hydrocarbon receptor (AhR)-dependent Nrf2 expression. These findings suggest that RUT exerts protective effects against oxidative-stress-induced apoptosis by controlling the Nrf2 signaling pathway in endothelial cells. Full article

To investigate the influence of pavement texture on tire hydroplaning, this study utilized laser scanning to capture the surface characteristics of three asphalt mixtures—AC-13, SMA-13, and OGFC-13—across fifteen rutting plate specimens. Three-dimensional (3D) pavement models were reconstructed to incorporate realistic texture data. Finite element simulations, employing fluid-structure interaction and explicit dynamics in Abaqus, were conducted to model tire-water-pavement interactions. The results indicate that the anti-skid performance ranks as OGFC > SMA > AC. However, despite OGFC and SMA exhibiting comparable anti-skid metrics (e.g., pendulum friction value and mean texture depth), OGFC’s superior texture uniformity results in significantly better hydroplaning resistance. Additionally, tire tread depth critically influences hydroplaning speed. A novel Anti-Slip Comprehensive Texture Index (ACTI) was proposed to evaluate pavement texture uniformity, providing a more comprehensive assessment of anti-skid performance. These findings underscore the importance of texture uniformity in enhancing pavement safety under wet conditions. Full article

Semi-flexible pavement (SFP) mixture consists of porous matrix asphalt mixture and cement-based grouting material. This composite material gains advantages from both the rigid cementitious material and flexible asphalt mixture. It exhibits excellent anti-rutting capability while no joints are needed. However, SFP is prone to cracks in the field. This study employs water-based epoxy resin and emulsified asphalt as polymer additives to modify the grouting material. A response surface methodology (RSM) model was employed for multi-factor and multi-response optimization design. The ratio of water-based epoxy resin to emulsified asphalt (w/e ratio), polymer content, defoamer content, and mixing speed were considered in the model. Fluidity, compressive strength, and fracture energy were selected as response indicators. It was found that a low mixing speed was not able to produce grouting slurry with acceptable fluidity. The addition of higher polymer contents would lower the compressive strength of the grouting material due to the low stiffness of the polymer and entrained air produced during mixing. The addition of defoamer eliminated the bubbles and, therefore, increased the strength and fracture energy of the samples. By solving for the optimal model solution, the values of optimized parameters were determined to be a w/e ratio of 0.64, polymer content of 3.3%, defoamer content of 0.2%, and mixing speed of 2000 rpm. Microstructural analysis further confirmed that the synergistic effect of water-based epoxy resin and emulsified asphalt can effectively make the microstructure of the hardened samples denser. The anti-cracking ability of the SFP mixture can be increased by 22% using optimally designed grouting material. The findings in this study shed light on the design of toughness-reinforced SFP materials. Full article

A new type of reclaiming agent was prepared by adding a plasticizer and an anti-aging agent to waste palm oil. A dynamic shear rheological test, bending beam rheological test, dynamic modulus test, static creep test, and road performance test were used to compare and analyze the viscoelastic characteristics of vegetable oil (WPO) and a traditional petrochemical reclaiming agent (PCO). The results showed that the WPO has better low-temperature crack resistance compared with the PCO, and the optimal dosage is about 12% of the mass fraction of aged asphalt. The addition of a regenerator reduces the dynamic modulus of the reclaimed asphalt mixture (RAP) under study and increases the phase angle. The improved CAM model showed good fit with the dynamic modulus and phase angle of recycled asphalt mixtures with the development of frequency. When the loading frequency was higher than 10 Hz, the dynamic modulus of the waste palm oil recycled asphalt mixture was lower, and the phase angle was higher. Conversely, when the loading frequency was lower than 0.01 Hz, the waste palm oil regenerant showed better temperature sensitivity. The waste palm oil recycled asphalt mixture demonstrated a higher steady creep rate and strain magnitude, lower stress relaxation time, and higher dissipation energy ratio under low-temperature conditions, thus improving the low-temperature crack resistance. Furthermore, the road performance test results of the asphalt mixtures indicated that the waste palm oil reclaimed asphalt mixture has excellent high-temperature rutting resistance, low-temperature cracking resistance, and water damage resistance, which confirms the reliability of the above analysis results. Therefore, the waste palm oil regenerant has great potential application prospects with wide source availability, low price, and outstanding mechanical properties. Full article

Crumb rubber modification of bituminous binders for asphalt concrete mixture production has been shown to provide significant environmental benefits, in terms of reduced embodied carbon, as well as improvement in the mechanical performance properties of asphalt mixtures. Furthermore, even at low dosages of crumb rubber, significant anti-ageing benefits have been reported, in terms of oxidation and ultra-violet light exposure. However, the effect of low dosage crumb rubber modification on the mechanical properties of asphalt mixtures must be understood. This research compared otherwise nominally identical dense-graded asphalt mixtures produced with crumb rubber modified binder at 5%, 10%, and 15% (by weight of the bitumen) and, using short digestion (reflecting field blending) and long digestion (reflecting terminal blending), to two control asphalt mixtures across a range of mechanical properties indicative of stiffness, rutting resistance, fatigue cracking resistance, cold fracture resistance, and moisture damage resistance. It was concluded that 10% was the optimum crumb rubber content and that crumb rubber modification generally improved the mechanical properties of asphalt mixtures, particularly the deformation resistance and the fatigue cracking resistance, which were both improved significantly. However, the effect of crumb rubber content and digestion times was variable. Consequently, the decision to field blend (short duration) or terminal blend (long duration) should be based on logistics, and not on asphalt mechanical properties and the associated mixture performance. Full article