Search Results (1,931)

Electrospinning (ES) can produce nonwoven fibrous mats with high surface area and interconnected porosity, making them attractive for biomedical and functional material applications. However, conventional ES often relies on volatile organic solvents, raising safety, environmental, and translational concerns. Fully aqueous (“green”) ES offers an appealing alternative, although many water-soluble polymers remain difficult to spin and may show limited stability under hydrated conditions. In this study, two fully aqueous binary systems, poly(vinylpyrrolidone)–sodium alginate (PVP–SA) and poly(vinylpyrrolidone)–riboflavin (PVP–RF), were investigated to decouple the roles of sodium alginate (SA) and riboflavin (RF) on solution behaviour, fibre formation, morphology, dry-state mechanical properties, and surface chemistry. Aqueous PVP solutions (20% w/v; molecular weight 1.3 MDa) were blended with SA (1–5 wt% relative to PVP) or RF (1–10 wt% relative to PVP). Electrical conductivity and rheological properties were evaluated prior to ES under controlled conditions, with simultaneous ultraviolet (UV) exposure at 344 nm during fibre collection. RF did not significantly alter conductivity (~0.74–0.75 µS·cm⁻¹), whereas SA increased conductivity up to 2.75 ± 0.03 µS·cm⁻¹ at 5 wt%. All formulations exhibited shear-thinning behaviour, while 10 wt% RF increased the zero-shear viscosity relative to neat PVP. Morphological analysis showed that low SA contents produced uniform fibres, whereas higher SA levels (4–5 wt%) led to bead defects and reduced fibre diameter (down to 85 ± 25 nm). Dry-state mechanical performance decreased with increasing SA content, while 10 wt% RF improved tensile strength and toughness, reaching an ultimate tensile strength of 5.21 ± 0.15 MPa and toughness of 40.51 ± 1.53 MJ·m⁻³. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) indicated subtle UV-driven redistribution of surface chemical states, consistent with mild photo-oxidative microstructural modification rather than extensive covalent network formation. Because the UV irradiance was not directly measured and wet-state stability was not assessed, the UV-related findings are interpreted as preliminary chemical evidence rather than confirmation of stabilized fibre mats. Overall, this work establishes a solvent-free aqueous ES platform in which ionic and photoactive additives can be used to tailor fibre morphology, dry-state mechanical behaviour, and surface characteristics without toxic reagents. Full article

Green fair-faced concrete (GFFC) is characterized by low surface porosity and small pore sizes and is widely used in architectural concrete engineering. It remains challenging to meet the appearance quality requirements of GFFC with conventional mix ratios and additives. This paper introduces double-mix defoamers and air-entraining agents into GFFC slurry to further refine the internal bubble size of GFFC slurry, optimize the surface pore structure, and thereby improve the apparent morphology of cured GFFC. The effects of double-agent doping on the slump, mechanical strength, shrinkage performance and impermeability durability of GFFC were also investigated. The results show that, compared with the baseline, after binary doping of the defoamer and air-entraining agent, the slump loss over time of GFFC slurry has been significantly reduced; the average porosity of GFFC is 0.132%, and the maximum average pore diameter is only 1.01 mm, which is decreased by 57.35% and 67.68%, respectively; the 45 day shrinkage of the GFFC doped with 3‱ defoamer and 4‱ air-entraining agent is 338 × 10⁻⁶ with a decrease of 33.98%, and the resistance to 84d chlorine ionization migration coefficient is 1.3 × 10⁻¹² m²/s with a decrease of 38.09%. These outcomes can effectively contribute to the pore refinement and apparent morphology improvement of GFFC doped with a binary defoamer and air-entraining agent. Full article

Frozen sand molds are the key material in digital frozen sand mold green casting technology, and their mechanical properties directly affect casting quality. Currently, these molds are primarily prepared by mechanical stirring, mixing, and compaction, which tend to cause imbalanced moisture adsorption and localized wet–dry differences, ultimately impairing the performance and quality of the castings. In this study, an ultrasonic vibration-assisted platform was established to prepare chromite sand frozen sand molds. By introducing ultrasonic vibration into the preparation process, a superior “sand grain–ice crystal” microstructure was constructed, leading to significantly enhanced mechanical properties. The tensile and compressive strengths were increased by approximately 10%, and the optimal process window for achieving the best mechanical performance of chromite sand was obtained. Full article

As the global population continues to age, mental health issues such as depression, anxiety, stress, loneliness, and social isolation among older adults are receiving increasing attention. The built environment is closely associated with older adults’ daily mobility, environmental perception, social participation, and mental health and well-being, but the evidence remains heterogeneous across spatial contexts, environmental indicators, and study designs. Previous umbrella reviews have summarized broad links between the built environment and healthy aging, but less attention has been paid to recent original empirical studies published after the COVID-19 pandemic, the distinction between objective environmental exposure and subjective environmental perception, and the role of social participation as a pathway linking environmental conditions to mental health and well-being. This study employs a systematic literature review approach, searching and screening peer-reviewed empirical studies published between 2015 and January 2026 that focus on the associations between the built environment and older adults’ mental health and well-being. PubMed, Scopus, and Web of Science databases were used for searching, supplemented by manual searching. After title and abstract screening and full-text evaluation, a total of 60 studies were included. Subsequently, a comprehensive analysis was conducted on aspects such as research design, spatial scale, environmental indicators, types of mental health outcomes, and potential pathways of action. In this review, core mental health and well-being outcomes included negative outcomes, such as depression, anxiety, stress, psychological distress, loneliness, and social isolation, and positive outcomes, such as life satisfaction, subjective well-being, psychological well-being, and mental well-being. Social participation was examined as a behavioral and psychosocial pathway rather than as a core outcome. Emerging methods, including street-view image analysis, FCN-based semantic segmentation, and XGBoost-SHAP, were examined because they can refine environmental exposure measurement and support variable-importance interpretation, rather than because they provide causal evidence. The main synthesis suggests that several built environment factors are associated with older adults’ mental health and well-being, although the strength and consistency of evidence vary across outcome types, spatial contexts, and study designs. (1) Exposure to green and blue spaces, quality of public open spaces, walkability and accessibility, accessibility of neighborhood facilities and services, housing and living conditions, and positive environmental perception are mostly associated with lower levels of depression, anxiety, stress, and loneliness, as well as higher levels of life satisfaction, subjective well-being, and psychological well-being. (2) Conversely, adverse environmental exposures such as proximity to roads, pollution, non-vegetated spaces, and high-intensity urbanization are more likely to exacerbate negative psychological outcomes. Existing evidence also suggests that social participation is one of the important behavioral pathways through which the built environment is linked to the mental health of older adults, but it is not the only mechanism. (3) In addition, the direction and intensity of environmental associations remain heterogeneous under different spatial scales, indicator types, and research methods. Overall, this review contributes by organizing recent empirical evidence into a built environment–social participation–mental health and well-being framework, while emphasizing that most findings should be interpreted primarily as evidence of association rather than as stable or uniform causal effects. Full article

Silicon carbide–aluminum (SiC–Al) composites offer high hardness, wear resistance, thermal stability, and strength-to-weight ratio, making them suitable for advanced engineering applications. Fabricating these composites via powder metallurgy and infiltration methods has been reported. However, there is no reported study on fabricating SiC–Al composites using binder jetting additive manufacturing (BJAM) followed by sintering without infiltration. The present study aims to fill this gap. In this study, samples were printed by BJAM using SiC–Al mixed powders with two volumetric ratios (SiC:Al) of 60:40 and 80:20, respectively. These printed samples were then sintered at different temperatures (950 °C, 1200 °C, and 1400 °C). The results show that, using this new approach, the printed green samples retained structural integrity after sintering and that interparticle bonding was achieved. To the authors’ knowledge, this is the first study to fabricate a SiC–Al composite via binder jetting additive manufacturing using a mixed powder, followed by sintering without infiltration. Full article

The successful application of extrusion-based 3D-printed geopolymer mortars largely depends on precursor chemistry, activator composition, mixture proportions, and fresh-state behavior, which is highly sensitive to time-dependent structural build-up. This review examines the relationships among mix design, geopolymerization chemistry, rheological properties, and printability requirements for 3D-printed geopolymer mortars. Particular emphasis is placed on the effects of precursor type, alkaline activator characteristics, liquid-to-solid ratio, additives, and fibers on flowability, yield stress, viscosity, extrudability, buildability, shape retention, and interlayer bonding. The review further discusses how geopolymerization kinetics influence the evolution of fresh-state properties, the printable time window, and the transition from extrusion to structural stability. In addition, early-age performance is evaluated in terms of setting behavior, green strength development, and layer-interface integrity. Current challenges, including the lack of standardized test methods, limited comparability among published studies, and the complex coupling between material design and process parameters, are also highlighted. Finally, the review identifies key research gaps and proposes future directions for developing robust, printable, and sustainable geopolymer mortar systems for additive manufacturing in construction. Full article

The study investigated the tensile strength and elongation properties of abaca fiber-reinforced polymer (AFRP) composites after varying durations of seawater soaking, with a focus on their potential for reinforcing fiber-optic cables. It aims to bridge industrial technology education, experiential learning, and green technology by evaluating abaca fiber as a sustainable alternative to synthetic aramid yarn. Conducted at Caraga State University, Cabadbaran Campus (CSUCC), the research utilized a quasi-experimental product development design involving industrial technology students and instructors. Tensile strength testing and comparative analysis were performed on abaca fiber samples (A, B, and C) subjected to different seawater soaking durations. Results show that soaking time significantly affects the fiber strength, with Sample A achieving the highest tensile strength (5631.5 MPa) and Sample C the lowest (1679.8 MPa). Findings indicate that prolonged exposure to seawater weakens abaca fiber, emphasizing the need for controlled treatment to optimize its industrial applications. This study emphasizes the importance of hands-on learning in industrial technology education, promoting critical thinking and technical skills while underscoring sustainability. The research advocates for eco-friendly materials in industrial applications and highlights the potential of abaca fiber composites. Future studies should investigate pre-treatment methods to enhance fiber durability, assess the long-term environmental performance, and conduct large-scale pilot testing to evaluate commercial viability. By integrating sustainable innovations into industrial technology education, this study contributes to advancing natural fiber composites for manufacturing and telecommunications infrastructure. Full article

To address the environmental issues arising from the large-scale stockpiling of steel slag and to explore its efficient utilisation in road sub-bases, this study investigated the effects of cement dosage and steel slag content on the mechanical properties of cement-stabilised steel slag mixtures. Through unconfined compressive strength tests, compressive modulus of elasticity tests and splitting tensile strength tests, the study revealed the mechanisms by which cement dosage and steel slag content influence microstructure. The results indicate that as the cement content increases, the unconfined compressive strength, compressive modulus of elasticity and splitting tensile strength all show an upward trend, although the rate of increase gradually decreases. With increasing steel slag content, the unconfined compressive strength and splitting tensile strength first increase and then decrease slightly, whilst the compressive modulus of elasticity continues to rise. When 60% steel slag was incorporated, the 28-day unconfined compressive strength and splitting tensile strength reached their peak values, representing increases of 22.17% and 72.7% respectively compared to the control group. Further examination of the microstructure revealed that increasing the cement content and steel slag content enhances structural density and reduces surface porosity; however, excessive cement content and steel slag content have an adverse effect on mechanical properties. Consequently, the synergistic effect of an appropriate amount of steel slag and cement can significantly improve the mechanical properties and microstructure of the mixture. These findings are of great significance in promoting the green utilisation of solid waste materials, such as steel slag, in road engineering. Full article

Packaging systems play an important role in maintaining the storage stability of fermented specialty green coffee beans, thereby contributing to the preservation of attributes associated with coffee quality. This study advances the understanding of how multilayer oxygen-barrier packaging influences the storage stability of fermented and non-fermented green Arabica coffee beans. Samples were analyzed after 3, 6, and 9 months for moisture sorption behavior and content, instrumental color, texture, and packaging mechanical resistance. Moisture content remained within the recommended range for green coffee (8.5–11%) in all systems, while rupture force values ranged from 480 to 570 N. Fermented samples showed limited moisture variation, whereas non-fermented coffees exhibited greater variability, particularly in thinner and more permeable packaging. The GAB model showed superior fitting performance for moisture sorption data, with R² values up to 0.99, indicating better predictive accuracy than the BET model. Color analysis showed progressive changes during storage, with non-fermented coffee exhibiting greater color variation than fermented coffee under similar conditions. Among the evaluated systems, the thickest multilayer packaging (Packaging 2) showed superior mechanical strength (56.63 MPa), and barrier performance, approximately three times higher than the other systems. Overall, high-barrier multilayer packaging combined with fermentation effectively preserved green coffee physicochemical quality during long-term storage. Full article

This study addresses the early-age brittleness and performance limitations of sustainable cement soil. While prior works optimized the baseline compressive strength using recycled sand and nanoclay, the multi-scale synergistic effects of fibers and nanomaterials on the post-peak deformation remain underexplored. To address this gap, a composite modification system incorporating recycled sand, nanoclay, polypropylene fibers, and graphene derivatives was developed. The experimental program comprised standard specimen fabrication, early-age curing, and unconfined compressive strength (UCS) testing, supplemented by RBF neural network curve fitting and quantitative ArcGIS digital image processing of scanning electron microscopy (SEM) micrographs. The results demonstrate that optimizing the fiber parameters (0.6% content with 6 mm length) successfully increases the early UCS to 2263.2 kPa, which is further elevated to a peak of 2755.0 kPa upon co-incorporation with 0.05% small-sized graphene oxide. Correspondingly, a newly introduced ductility index quantitatively confirms that the single-fiber reinforcement yields an index of 1.93, which is further enhanced to 2.02 by the graphene composite system. Microstructure tracking and digital image extraction revealed that the SEM-derived surface porosity decreased significantly, exhibiting a clear inverse relationship with the macroscopic mechanical strength. These quantitative microstructural shifts confirm that graphene effectively filled micropores and reinforced the fiber–matrix interface, establishing a dense matrix network with enhanced interfacial bonding. This multi-scale approach offers a sustainable strategy for green geotechnical applications. Full article

Using solid wastes to fabricate sustainable backfill materials for mining engineering is crucial for environmental sustainability worldwide. In this study, the use of coal gangue aggregates as a sustainable alternative to natural aggregates in geopolymer gel backfill materials was explored, which contributes to green mining development. Through uniaxial compression tests, the effects of fine gangue content, mass concentration, and the binder content of geopolymer backfill materials on the compressive behavior of coal gangue geopolymer gel backfill–rock combinations (CGBRC) were systematically evaluated. Digital Image Correlation (DIC) and acoustic emission (AE) techniques were employed to reveal the strain field evolution and damage progression of CGBRC. Results show that as the content of fine coal gangue increases, the compressive strength first increases and then decreases. Compared with the compressive strength at a 20% content, the compressive strength at a 40% content increased by 33.2%, while the elastic modulus increased by 11.2%. Meanwhile, with the increase in mass concentration and binder content, the compressive strength and elastic modulus of coal gangue geopolymer filling materials show an increasing trend, reaching peak values at 86% mass concentration and 32% binder content, respectively. The strain concentration zones mainly form near the backfill interface, with propagation paths governed by backfill strength. Damage evolution undergoes three stages including rapid accumulation during compaction, gradual development in the elastic-plastic stage, and abrupt acceleration at failure. The interfacial debonding behavior is primarily influenced by the strength difference between the backfill and surrounding rock. Specimen failure is dominated by brittle shear fracture, categorized into three modes based on crack paths relative to the backfill, which include penetrating backfill failure, axisymmetric interface failure, and centrally symmetric interface failure. These findings offer theoretical and technical support for coal gangue resource utilization and green mining practices, advancing sustainable solid waste management. Full article

This study aims to explore the preparation process and properties of unburned lightweight aggregate using red mud synergistically with fly ash, granulated blast-furnace slag, and other multi-source solid wastes. Curing regimes and alkali-activated systems were controlled. Their effects on physical properties and environmental safety of lightweight aggregate were systematically evaluated. Results show that curing temperature and alkali activator exert significant synergistic effects on physical properties of lightweight aggregates. Steam curing performs better than standard curing. Performance improves with increasing steam temperature. Sodium silicate solution with a modulus of 1.0 is determined as the optimal activator. Under 90 °C steam curing, Sample D2 achieves the best overall performance. Its cylinder compressive strength reaches 6.92 MPa. 1 h water absorption is 14.8%. Softening coefficient is 0.93. Porosity is as low as 31.07%. Microscopic analysis reveals that higher curing temperature significantly accelerates the hydration reaction of the RMLWA system. It promotes the formation of abundant cementitious products such as C-S-H gel. These products fully fill internal pores and microcracks of the aggregate. A dense three-dimensional network skeleton structure is finally formed. For environmental safety, heavy metal leaching concentrations of steam-cured samples are generally lower than those of standard-cured samples. This study realizes high-value resource utilization of industrial solid wastes. It also provides a new technical route for the development of green building lightweight aggregate. Full article

Concrete contributes significantly to global CO₂ emissions due to high energy demand for cement production. This research integrates multiple advanced ensemble ML-based prediction models by combining experimental evaluation, explainable framework, and life cycle sustainability analysis for SCM (supplementary cementitious materials)-incorporated concrete mixtures. A comprehensive experimental program was conducted to evaluate the compressive and tensile strength of concrete revealing that the hybrid mix of GF4 with a 40% replacement level of cement with fly ash (FA) and ground granulated blast furnace slag (GGBFS) exhibited optimum synergistic performance due to balanced hydration kinetics and improved microstructure characteristics. For computational model development, a k-fold cross validation technique was deployed to evaluate robustness across multiple data partitions and to control overfitting in models. Model performance was assessed through multiple metrics including R², RMSE, and MAE with particular emphasis on the gap between training and testing performance. The best performing model was optimized using Particle Swarm Optimization (PSO) and Bayesian Optimization (BO) techniques providing an additional safeguard against overfitting. Shapley Additive Explanation (SHAP) interpretation revealed w/b ratio and curing age as key parameters for compressive strength, while fine aggregate content and curing age influenced tensile strength. For compressive strength, XGBoost model performed well with an R² value of 0.879 which was increased to 0.918 with the PSO optimization technique. For tensile strength, the Gradient Boosting model was selected with an R² value of 0.840 which was optimized to 0.879 after the PSO optimization technique. Moreover, life cycle assessment was performed to evaluate the environmental impacts in terms of embodied carbon and energy associated with concrete mixes. The hybrid GF4 mix demonstrated a 36% reduction in embodied carbon compared to the control mix, indicating strong potential for low carbon concrete applications. This integrated research contributes to the advancement of green construction practices and supports global efforts to reduce atmospheric impacts through the circular use of industrial byproducts. Full article

Carbon fiber-reinforced polymer (CFRP) composites are in urgent demand in the aerospace, new energy vehicle, and wind power sectors owing to their superior specific strength, specific modulus, and lightweight potential. However, molding defects, such as voids, dry spots, and delamination, arising from their anisotropy and weak interlaminar bonding, severely constrain their service performance. Advanced molding technologies represent the key to overcoming this bottleneck. This paper systematically reviews typical advanced molding technologies in the field of CFRP composites, including resin transfer molding (RTM) and vacuum-assisted resin transfer molding (VARTM) in liquid composite molding, autoclave molding and compression molding (CM) in prepreg molding, and automated fiber placement (AFP) and material extrusion (ME) in automated molding. From an integrated perspective of “technological evolution–process characteristics–defect mechanisms–optimization strategies,” this review summarizes the technical principles, development trajectories, and core advantages of each process, analyzes the formation mechanisms of typical defects, including voids, dry spots, delamination, wrinkles, warpage, and melt instability, and summarizes multidimensional optimization advances in process parameter regulation, numerical simulation, resin modification, equipment upgrading, path planning, and thermal management. Furthermore, the differences and complementarities among these processes in terms of molding precision, efficiency, cost, and applicable scope are compared. Finally, future development directions, including digital twins, green low-carbon manufacturing, ultra-large integrated structures, multi-process integration, standardized defect characterization, and low-cost collaborative design, are discussed. This paper aims to provide systematic theoretical references and technical support for the optimization and upgrading, process integration, and industrial application of advanced CFRP molding technologies. Full article

To investigate the mechanism by which a combination of desert sand (DS) and recycled coarse aggregate (RA) affects the sustainability of recycled concrete, multiple mix proportions with varying replacement ratios were designed in this study. Macroscopic performance tests and microscopic analyses were performed using nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and X-ray diffraction (XRD), and the results were combined with grey relational analysis to reveal the intrinsic relationships between pore parameters and macroscopic properties. Additionally, technical and economic evaluations were conducted. The results indicate that incorporating either type of aggregate individually has a nonlinear effect on the compressive strength and impermeability of concrete. The optimal compressive strength is achieved when both aggregates are used at 20% replacement, whereas the best impermeability occurs at 10% replacement for each. The proportions of transitional pores and capillary pores, along with T₂ relaxation parameters, serve as key microstructural indicators for controlling performance. Economically, the use of both aggregates together significantly reduces material costs—reaching a cost savings rate of 3.51% with a recycled aggregate replacement level of 30%. Further substitution of 30% desert sand for river sand under the same replacement ratio can reduce costs by an additional 1.56%. This mix proportion achieves optimal synergy among mechanical performance, cost control, and low-carbon benefits. The findings provide theoretical guidance and practical support for mix design, durability enhancement, and the promotion of such green, low-cost concrete in engineering applications. Full article