Search Results (3,682)

Seed dispersal by humans plays an important role in determining vegetation structure. The seeds of Asian plantain (Plantago asiatica L.) form adhesive mucilage upon hydration, facilitating their attachment to shoes and subsequent dispersal via epizoochory. We investigated the efficacy of this mechanism under various urban environmental conditions. After trampling wild P. asiatica stands, the number of seeds attached to shoe soles was counted. The remaining seeds were then counted after walking at designated distances (1, 2, 5, 10, 20, 50, 100, 200, 500, and 1000 m). The following results were obtained: (1) The retention rate after walking 1000 m varied by shoe type (slip-on (kakkusu) work shoes, 15.4%; leather shoes, 3.4%; rubber boots, 2.7%; running shoes, 13.5%; and sandals, 12.4%). (2) Within the first 50 m of walking, on average more than half of the attached seeds fell off under all investigated conditions. Significantly fewer seeds remained after walking 50 m on asphalt (30.9% of the initial seeds) than on grass (48.2%), whereas after walking 1000 m, similar proportions (15.4% on asphalt and 15.7% on grass) remained on the work shoes. These results indicate that human-mediated short- and long-distance dispersal of mucilaginous seeds of this species is effective in diverse urban environments. Full article

The reuse of milled pavement material, known as RAP (Reclaimed Asphalt Pavement), represents one of the major current challenges in highway engineering worldwide. There is no doubt that the most valuable application of this residue is its use in the production of new hot asphalt mixtures, incorporating the highest possible RAP content, a process that requires adaptations in residue processing at asphalt plants. In Brazil, the RAP content added to these mixtures is limited to a maximum of 25%. Consequently, alternative applications have gained prominence in the country to increase RAP utilization in pavement engineering, such as its use in cold premixed asphalt mixtures. This study aimed to evaluate the performance of cold asphalt mixtures containing different RAP contents through mechanistic-empirical analyses of a reference pavement structure, using the modelling framework adopted in the Brazilian Asphalt Pavement Design Method (MeDiNa). After Marshall mix design and volumetric and mechanical characterization of mixtures containing 0%, 10%, 20%, 30%, and 40% RAP, stiffness and fatigue parameters were used to estimate the evolution of cracked area in the reference pavement, with each mixture applied as the surface layer under different traffic levels. The results demonstrated that pavement performance improved for all RAP contents evaluated compared to the mixture without RAP, with the mixture containing 30% RAP showing the best overall performance. Full article

Earthfill dams located in seismic regions are highly vulnerable to earthquake-induced deformations, particularly when founded on soft alluvial soils. This study presents a comparative numerical investigation of earthfill dams with asphalt and clay cores subjected to seismic loading. A 20 m-high zoned embankment dam founded on soft alluvial deposits was modeled in PLAXIS2D and subjected to four earthquake records. The dynamic responses at the crest and downstream slope were evaluated in terms of acceleration, settlement, and lateral displacement. The results indicate that while lateral displacements are nearly identical for both core types, dams with clay cores experience significantly higher seismic settlements, reaching up to 35% more than those with asphalt cores under strong earthquake loading. Overall, the asphalt core demonstrated enhanced resilience, exhibiting reduced settlement due to its higher stiffness, viscoelastic behavior, and inherent capacity for self-healing following seismic loading. Full article

To evaluate the runoff pollution characteristics of roofs in an arid region, this study focused on Yinchuan City, China. It analyzed the runoff properties of various roof materials, including tile, asphalt, and color steel plate. Five rainfall events were monitored during 2024, with samples collected manually at roof pipe outlets and analyzed for suspended solids (SS), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH₃-N). The results indicated that the concentration of pollutants in runoff from these roofs decreased as rainfall duration increased. The event mean concentration (EMC) of TN and COD in runoff from all three roof materials exceeded the Class V surface water quality standards in China. The first flush of pollutants in roof runoff followed a descending order: SS > COD > TP > TN > NH₃-N. Cluster analysis of three rainfall parameters—dry period, precipitation, and rainfall intensity—revealed that dry period exerted the strongest influence on runoff quality, indicating that the overall quality of roof runoff was primarily influenced by the cumulative effects of atmospheric deposition, with rainwater scouring being the secondary factor. These findings provide critical insights for designing stormwater management strategies and rainwater harvesting systems in arid and semi-arid cities, emphasizing the need to prioritize first-flush control and consider local climatic conditions. Full article

Stone Matrix Asphalt (SMA) has emerged as a premier high-performance paving solution for critical infrastructure applications. Its distinctive skeleton structure, composed of coarse aggregates bound by a fiber-stabilized bituminous mastic, delivers exceptional mechanical performance, including superior resistance to rutting (≤3 mm after 10⁶ load cycles) and fatigue cracking (>500,000 cycles to failure). While proven in demanding service environments, research has increasingly focused on enhancing the sustainability of SMA through key innovations: (1) the incorporation of recycled materials, such as 30–40% Reclaimed Asphalt Pavement (RAP) and 0.3–0.5% waste tire textile fibers (WTTF); (2) the development of bio-based binders derived from renewable sources; and (3) the adoption of Warm-Mix Asphalt (WMA) technologies that reduce production temperatures by 20–30 °C. These advancements yield significant environmental benefits, including approximately 25% lower CO₂ emissions and 15–20% reduced energy consumption compared to conventional SMA production. It is important to distinguish between these quantitatively demonstrated benefits, primarily from Life Cycle Assessment (LCA) studies of technologies like WMA and RAP, and the more qualitative sustainability claims associated with emerging materials like nanomaterials or novel bio-additives, which often lack comprehensive lifecycle inventories. Nevertheless, challenges persist, notably moisture susceptibility (manifesting as a 10–15% strength reduction after saturation) and uncertainties regarding the long-term performance of modified mixes. This review consequently identifies critical research priorities: optimizing mix designs with locally available materials to minimize transport emissions, employing nano-scale modifiers to enhance moisture resistance, and developing standardized lifecycle assessment protocols. Addressing these challenges is paramount to establishing SMA as a model sustainable pavement technology that robustly meets both structural performance benchmarks and ecological sustainability goals. Full article

Winter cities face the dual pressures of climate change and population aging, urgently requiring a shift from a singular focus on winter protection toward a development model adaptable to both winter and summer conditions. This shift is essential to enhance social resilience and safeguard the health of all age groups. This case study investigates how the thermal environment of life-sustaining streets in winter cities correlates with older adults’ daily activities. Employing Spearman correlation analysis, a heat exposure–pedestrian flow coupling matrix, and a comprehensive risk diagnostic model, the research analyzes the spatiotemporal variation patterns and underlying drivers of the street thermal environment. The key findings are: (1) All 15 surveyed streets exhibited Wet Bulb Globe Temperatures (WBGT) exceeding 28 °C during peak activity hours, with afternoon values (17:00–19:00) up to 2.7 °C higher than morning values. (2) On East Chaoyang Road, despite building shade and a high Visible Green Index (39.68%), the WBGT ranked second highest. This condition is attributed to a critically low average wind speed of 0.69 m/s (significantly below the city’s summer average of 2.67 m/s) and the widespread use of low-albedo asphalt, which collectively trap heat and negate the benefits of shading. (3) Using a dual-dimensional diagnostic framework, four streets were identified as dual-pressure streets with their combination of high elderly pedestrian flow (exceeding 126 persons/h) and high thermal risk (WBGT > 29 °C), marking them as priority intervention units. Based on these findings, the study proposes categorized street retrofit strategies that synergistically integrate climate adaptation and aging-friendliness. This provides an actionable, evidence-based foundation for planning decisions to support the sustainable renewal of winter cities amid climate change and population aging. Full article

This study investigates the synergistic use of Fischer–Tropsch wax (FTW) and recycled rubber powder (RP) as dual modifiers in stone mastic asphalt (SMA11) to improve its mechanical and functional performance. Rheological analysis demonstrated that an FTW content of 4% achieves the optimal balance of high-temperature rutting resistance, aging resistance, and workability, with a binder viscosity of 1.6 Pa·s at 135 °C. When incorporated into SMA11 mixtures at 15%, RP yielded the best overall mechanical performance, including a reduction in rut depth to 1.22 mm and a 25% decrease in wheel tracking slope (WTS). The 15% RP mixtures also exhibited superior long-term skid resistance (μ_m = 0.329 after 180,000 polishing cycles, corresponding to a 13% reduction in braking distance) and enhanced thermal cracking resistance (failure temperature improved by 8.0 °C to −32.7 °C). An RP content of 5% maximized moisture resistance (ITSR = 100%), while 10% RP produced the highest mid-frequency sound absorption coefficient (α = 0.050). The hybrid modification system enables a 20 °C reduction in production temperature, consistent with published data on wax-based warm-mix technologies, and is associated with reduced energy consumption and lower emissions. The approach simultaneously supports sustainable pavement design through the high-value reuse of waste tire rubber. Full article

Against the backdrop of the continuous advancement of high-quality development in road infrastructure and the growing demand for waste asphalt recycling, the application limitations of traditional petroleum-based asphalt rejuvenators have become increasingly prominent due to their high resource dependence, poor compatibility with aged asphalt, and high volatility. By contrast, bio-oil, characterized by wide feedstock availability, outstanding renewability, and the inherent potential to modulate the colloidal structure and properties of aged asphalt, has gradually emerged as a critical research direction in the field of asphalt rejuvenator development. This paper provides a comprehensive review on the research, development and engineering application of bio-based rejuvenators. Firstly, the main feedstock systems, including vegetable oils, lignin derivatives and algal oils, are introduced, and the core preparation technologies (e.g., pyrolysis and alkali-catalyzed transesterification) are discussed, along with the impacts of their key process parameters on the chemical composition and storage stability of the end products. Subsequently, the performance of various bio-based rejuvenators in optimizing the rheological properties, high- and low-temperature performance, as well as fatigue and cracking resistance of aged asphalt is summarized, and the underlying rejuvenation mechanisms are generalized. Finally, the prevailing technical bottlenecks, such as inconsistent quality of as-prepared products and insufficient understanding of the long-term aging mechanism, are analyzed. Future research directions including oriented molecular modification, interfacial regulation, and full life cycle assessment (LCA) are proposed, to provide a systematic reference for their large-scale engineering application. Full article

The current gradation design of asphalt mixtures relies solely on sieve passing rates of single-sized aggregates. The quantitative evaluation of aggregate gradation is a challenge, considering the combined action of the geometric characteristics, size and passing rates of the aggregates. Analyzing the multi-dimensional geometric synergistic characteristics of graded aggregate can help to quantify the gradation. The AIMS II system was used to systematically and quantitatively evaluate the shape, angularity and texture of parameter distribution of single-sized aggregates. The synergistic effect of composite geometric characteristics on the mesoscopic interface behaviors was analyzed, and then a calculation model of aggregate gradation characteristic was established based on the gray relational analysis method. The results show that the lithology and source of aggregates govern the geometric characteristics indices of single-sized aggregates, whereas particle size controls the extent to which these geometric characteristics contribute to skeleton stability and interface interactions. A higher proportion of large-sized coarse aggregates results in a greater composite angularity index and a more stable skeleton structure within the asphalt mixture. Texture characteristics and particle size distribution are integrated into a unified composite texture index. As this index increases, the lubrication effect of asphalt on the aggregate skeleton becomes more pronounced. The aggregate gradation characteristic index demonstrates strong discriminative capability for different gradations and exhibits a robust linear correlation with aggregate–asphalt interfacial interaction indices. This index demonstrates strong capability to quantitatively describe the synergistic mechanism of multi-dimensional geometric characteristics and gradation types of asphalt mixtures. Full article

Although extensive research has been conducted on the regenerants for unmodified and SBS-modified asphalt, in-depth studies on the activation of regenerants to restore the SBS cross-linked network while preserving their diffusion performance have not yet been reported. This study quantitatively evaluated the activation effect of self-healing regenerants on SBS cross-linked networks by testing the activation degree of 6%, 8%, and 10% cross-linked networks with self-healing regenerants; the phase structure of SBS-modified asphalt before and after regeneration was examined using fluorescence microscopy (FM); the underlying mechanism of the reactive regenerant was elucidated by Fourier Transform Infrared Spectroscopy (FTIR) and Gel Permeation Chromatography (GPC); furthermore, the rheological response characteristics of the reactive regenerant and conventional regenerant were comparatively analyzed. The findings indicated that the SBS cross-linked network self-healing regenerant exhibited a more pronounced activation effect on aged asphalt. Specifically, when the dosage of the regenerant reaches 8%, its repairing effect on the cross-linked network becomes particularly significant. Reconstructing the cross-linked network structure of SBS-modified asphalt enabled the recovery of the viscoelastic properties of the recycled asphalt. Nevertheless, an excessive dosage of the regenerant failed to further enhance the cross-linked structure in a meaningful way and might even exert an adverse impact on the high-temperature performance of the recycled asphalt. Full article

Thermal conductivity and specific heat capacity are key parameters controlling heat transfer and temperature distribution in road pavement structures. Although transient methods are increasingly used in laboratory testing, the thermal properties of asphalt mixtures have not been sufficiently studied using these methods, and no dedicated standards exist for road materials. This creates uncertainty in test procedures, specimen geometry, surface preparation, measurement location, and data interpretation, which may lead to significant errors, especially for massive and heterogeneous mixtures. The objective of this study is to systematically quantify the edge zone effect and assess its influence on the determined thermal parameters of a selected heterogeneous asphalt mixture. The study focuses on the quantitative determination of the edge zone effect, practical identification of its width in slab-shaped specimen, and the identification of scientific and practical methodological consequences, as well as the risks and limitations of applying the Modified Transient Plane Source (MTPS) method in the absence of standards. Laboratory measurements demonstrate a clear edge zone effect, with thermal conductivity and thermal diffusivity differing by up to 17% and 18%, respectively, near the specimen edges. These findings highlight the importance of methodological guidelines for slab-shaped asphalt mixture specimens and provide both scientific insight and practical guidance for the reliable application of transient method. They may also support the development of standardized testing procedures for asphalt mixtures. Full article

Thermosetting polyurethane (PU) has recently been introduced as an asphalt modifier to improve the mechanical strength and durability of pavements. However, the permanent crosslinked network of thermosetting PU makes the material difficult to repair once damage accumulates. In contrast, self-healing asphalt technologies rely on either extrinsic healing agents or intrinsic dynamic bonds to restore stiffness and delay cracking. Dynamic disulfide bonds are a promising class of reversible covalent bonds that can rearrange at moderate temperatures and have been widely used to build self-healing polyurethane networks. This study investigates a disulfide-crosslinked polyurethane-modified asphalt binder (DP10) and compares its fatigue and healing performance with base asphalt (BA), thermosetting PU-modified asphalt (P10), and styrene–butadiene–styrene (SBS)-modified asphalts (S3 and S10). A dynamic shear rheometer (DSR) was used to conduct time sweep fatigue tests, linear amplitude sweep (LAS) tests, and fatigue–healing–fatigue protocols. Fourier transform infrared spectroscopy (FTIR) was employed to confirm the formation of polyurethane and disulfide structures. Results show that DP10 significantly increases fatigue life at small to medium strain levels compared with BA and P10 and performs competitively with SBS-modified binders. More importantly, DP10 exhibits a much higher healing index than P10 and maintains strong healing capability over repeated fatigue–healing cycles, approaching the intrinsic healing level of base asphalt. These findings demonstrate that incorporating dynamic disulfide bonds into thermosetting PU networks provides a practical route to binders that combine high strength with recoverability, which is attractive for long-life, self-healing pavement design. Full article

High-quality pavement materials at reasonable prices are crucial for managing many heavy truck loads and hot weather conditions that present significant challenges for researchers, managers, and engineers. One effective strategy is to incorporate polymers into modified asphalt or asphalt mixtures. However, there are several notable challenges when using polymers in asphalt concrete, particularly related to mixing procedures and methods. Worldwide, two primary mixing methods are commonly used, including traditional dry and modified dry techniques. The dry method is usually preferred for using polyethylene terephthalate (PET) due to its various advantages. The indirect tensile strength, static resilient modulus, dynamic modulus, and fatigue tests were examined for all asphalt mixtures with PET using both dry methods. The findings from this research suggest that the modified dry mixing method is more effective, particularly regarding fatigue resistance, based on a systematic analysis of the results. In addition to these experimental investigations, an analysis of flexible pavement design for a typical pavement section has been conducted. This analysis utilized the experimental resilient modulus of all mixtures to predict fatigue life based on the Asphalt Institute model. Full article

As core materials in pavement structures, asphalt mixtures are characterized by intensive energy consumption and significant carbon footprints throughout their construction cycle, making their construction a typical high-carbon process in road engineering. Warm-mix technology, leveraging its key advantages of reducing mixing temperatures and cutting energy consumption and emissions, has emerged as a green alternative to hot-mix mixtures. However, existing studies have lacked systematic environmental impact assessments of combinations of asphalt from different oil sources and warm-mix technologies. This study focuses on the additive type warm-mix technology (Evotherm M1) and uses three typical oil sources of 70# road petroleum asphalt. Using headspace gas chromatography–mass spectrometry (HS–GC–MS) and Life Cycle Assessment (LCA) methods, a systematic analysis was conducted across three dimensions: multi-component pollutant emissions, full life cycle stages, and multi-type warm-mix technologies. The analysis focused on the influence of warm-mix treatment on Volatile Organic Compound (VOC) emissions, as well as energy consumption and carbon emission characteristics throughout the full life cycle of the construction phase. Results indicate that warm-mix treatment significantly inhibits VOC emissions from all three oil source asphalts. The largest reduction was observed in Asp-A (74.66%), followed by Asp-C (69.27%), and the smallest in Asp-B (46.47%). The VOC compositions shifted from being dominated by oxygenates to a coexistence of multi-components such as alkanes and aromatic hydrocarbons. In the life cycle of the construction phase, compared with hot-mix mixtures, warm-mix technology reduced total energy consumption by 5.50%–5.56% and carbon emissions by 4.47%–4.52%. Raw material production and mixture mixing stages were identified as the core links for energy consumption and carbon emissions, accounting for over 80% of the totals. Differences among oil sources mainly stemmed from refinery power structure and the temperature–viscosity properties of asphalt. The research results provide theoretical support for material selection and process optimization of green construction of asphalt pavement using additive-based warm-mix technology. Full article

To prepare a modified asphalt with excellent road performance, thermoplastic polyurethane/graphene oxide (TPU/GO) incorporating dynamic disulfide bonds was developed as an additive and the synergistic effect of TPU and GO on asphalt was evaluated. Modified asphalts with different TPU/GO contents (2%, 4%, 6%, 8%) were prepared and TPU-modified asphalts were also prepared as control groups. The compatibility between TPU/GO and asphalt was evaluated by fluorescence microscopy (FM) and the dispersion of GO in TPU and asphalt was observed by emission scanning electron microscope (SEM). The road performance of modified asphalts was also assessed in this study. The FM results show that TPU/GO has good compatibility with asphalt, and the SEM results reveal that GO can be uniformly dispersed in TPU matrix, so that GO can also be evenly dispersed in asphalt and avoid the problem of GO aggregation in asphalt. The results also demonstrate that TPU/GO-modified asphalt comprehensively utilizes the respective advantages of TPU and GO. TPU/GO-modified asphalt has excellent low-temperature performance compared with base asphalt. The 5 °C ductility of 8%TPU/GO-modified asphalt is 440% higher than that of base asphalt and the BBR test also showed that the stress relaxation capacity of TPU/GO-modified asphalt is also significantly stronger than that of base asphalt. Moreover, the introduction of GO in asphalt can improve the creep recovery rate and complex modulus compared with TPU-modified asphalt, indicating better high-temperature rutting resistance. Comprehensive performance evaluation indicates that 8% TPU/GO-modified asphalt is the optimal dosage for engineering applications, balancing high-temperature rutting resistance, storage stability, anti-aging performance, and low-temperature behavior. Full article