Search Results (1,700)

This study presents a multi-index performance system that is systematically used to assess the binder synergy and fly ash reactivity of eco-sustainable cementitious composite (ESCC) using the Strength Activity Index (SAI) as a reference in line with ASTM C618. The partial replacements of fly ash with high and low calcium fly ash (HCFA and LCFA) were added to the fly-ash-to-sand (FA/S) ratios of 0, 10, 20, and 30% with a constant mix parameter, such as a 50% ratio of water to slag and a 20% ratio of activator to slag. The Initial Flow Index (IFI) and Flow Retention Index (FRI) were used to measure fresh-state performance, and compressive-, tensile-, and flexural-based indices, i.e., the SAI, Tensile Strength Index (TSI), and Flexural Strength Index (FSI), were used to measure mechanical performance. The results indicate that flowability and workability retention decrease with an increase in the FA/S ratio, with LCFA-based mixtures having better flow retention than HCFA systems. The optimum mechanical performance at a replacement level of 20% FA/S produced the maximum SAI values of about 112% HCFA and 110% LCFA with a consistent increase in TSI and FSI values at 28 days. When the replacement levels were increased (30% FA/S), all strength indices decreased with the effect of dilution and decreased the packing efficiency of the binder. Comparisons of the SAI with the respective TSI and FSI values through correlation analysis showed that the quantitative relationship between compressive, tensile, and flexural behavior was definite and showed that compressive strength alone is not enough to extrapolate mechanical performance. Collectively, the proposed framework provides a reasonable performance-based basis for the manner in which fly ash could be utilized in the most effective way in eco-sustainable cementitious compositions. Full article

Large quantities of agricultural waste, particularly rice husk ash (RHA), are generated worldwide each year, and the lack of rational, value-added disposal pathways poses both environmental and resource-utilization challenges. To address this practical problem while improving the freeze–thaw (F–T) durability of cement-based materials in cold regions, this study investigates the effects of replacing silica fume (SF) with finely milled RHA on the hydration behavior, mechanical performance, and durability of cement mortar. From a scientific perspective, the freeze–thaw behavior of RHA-modified cementitious materials and the underlying relationships among hydration kinetics, microstructural evolution, and durability remain insufficiently understood. Mortars with different RHA–SF blending ratios were prepared at a constant water-to-binder ratio. Compressive strength was measured before and after F–T cycling, and the underlying mechanisms were investigated using isothermal calorimetry, water absorption tests, and scanning electron microscopy. Results show that SF significantly enhances pre-F–T compressive strength, with the SF-only mixture reaching 56.8 MPa at 28 d, approximately 28.7% higher than the control. With increasing RHA replacement, pre-F–T strength decreased with a non-monotonic variation (40.1–51.5 MPa). F–T cycling caused severe degradation in the reference mortar, with a strength loss rate of 31.75%, whereas RHA- or SF-modified mortars exhibited substantially lower loss rates (6.30–21.54%). Notably, high-RHA mixtures retained residual strengths of 36.0–38.3 MPa after F–T cycling. Although RHA delayed early hydration and increased water absorption, freeze–thaw resistance was not proportionally reduced. These results demonstrate that freeze–thaw durability is governed primarily by long-term microstructural stability rather than early-age strength, and they provide mechanistic evidence supporting the rational utilization of finely milled RHA as a low-carbon supplementary cementitious material for cold-region applications. Full article

The valorization of dredged sediments represents a major environmental and logistical challenge, particularly in the context of forthcoming regulations restricting their marine disposal. This study investigates the potential of untreated dredged sediments as sustainable raw materials for geopolymer binder development, with the dual objective of sustainable sediment management and reduction in cement-related environmental impact. Dredged sediments from the Grand Port Maritime de Bordeaux (GPMB) were activated with sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃), both alone and in combination, with supplementary aluminosilicate and calcium-rich co-products, to assess their reactivity and effect on binder performance. A multi-scale experimental approach combining mechanical testing, calorimetry, porosity analysis, Scanning Electron Microscopy and Energy-Dispersive Spectroscopy (SEM–EDS), X-ray diffraction (XRD), Thermogravimetric Analysis (TGA), and solid-state Nuclear Magnetic Resonance (NMR) was employed to challenge the commonly assumed inert behavior of sediments within geopolymer matrices, to elucidate gel formation mechanisms, and to optimize binder formulation. The results show that untreated sediments actively participate in alkali activation, reaching compressive strengths of up to 5.16 MPa at 90 days without thermal pre-treatment. Calcium-poor systems exhibited progressive long-term strength development associated with the formation of homogeneous aluminosilicate gels and refined microporosity, whereas calcium-rich systems showed higher early age strength but more limited long-term performance, linked to heterogeneous gel coexistence and increased total porosity. These findings provide direct evidence of the intrinsic reactivity of untreated dredged sediments and highlight the critical role of gel chemistry and calcium content in controlling long-term performance. The proposed approach offers a viable pathway for low-impact, on-site sediment valorization in civil engineering applications. Full article

Biomass liquefaction is a thermochemical process that converts lignocellulosic materials into reactive liquid intermediates, enabling the production of bio-based polyols as a sustainable alternative to petroleum-derived chemicals. This study investigates the liquefaction of two lignocellulosic biomasses, Red Angico (Anadenanthera colubrina) and Mahogany (Swietenia macrophylla), using a glycerol–ethylene glycol polyalcohol system, chosen for its renewable origin and high solvating efficiency. The resulting polyols were used to produce polyurethane (PU) foams, and their properties were evaluated in relation to biomass composition. The chemical composition of each biomass significantly influenced its liquefaction behavior and polyol characteristics. Mahogany achieved higher liquefaction efficiency, whereas Red Angico polyols generated PU foams with superior mechanical performance, highlighting the influence of species-specific chemistry. Water content and isocyanate index were found to modulate foam structure and compressive strength. This work demonstrates how tailored liquefaction strategies using polyalcohol systems can optimize bio-based PU foam properties, providing a sustainable route for high-performance polymer materials. Full article

Objectives: The purpose of the present study was to investigate the acute effects of cold-water immersion (CWI), cryotherapy (CRT), and intermittent pneumatic compression (IPC) on lower-body neuromuscular performance in female basketball players. Methods: Eighteen athletes volunteered to participate (body mass = 63.0 ± 7.2 kg; height = 171.4 ± 6.5 cm; age = 16.4 ± 1.2 years), completing testing at three time points: (i) pre-practice, (ii) post-practice, and (iii) 45–60 min following a randomly assigned recovery intervention. At each time point, athletes performed three countermovement vertical jumps on a dual force plate system sampling at 1000 Hz (VALD Performance). To standardize external load across groups, all players wore inertial measurement units (Kinexon). Results: The two-way repeated measures ANOVA showed no statistically significant interaction (p > 0.05) between the three testing time points and recovery modalities for any of the analyzed variables. However, a significant main effect of time was observed, with 13 of 20 force-time metrics (65%), including jump height, reactive strength index-modified, contraction time, and concentric peak and mean force, declining post-recovery compared with pre-practice values, regardless of the recovery intervention applied. External load measures (e.g., total distance, number of jumps) remained consistent across groups. Conclusions: Overall, these findings suggest that CWI, CRT, and IPC were no more effective than passive recovery (i.e., control group) in mitigating post-practice declines in lower-body force and power-producing capacities. Full article

The construction sector faces the dual challenge of reducing energy consumption and mitigating the environmental burden of construction and demolition waste (CDW). Geopolymers offer a low-carbon alternative to Portland cement, yet their performance depends strongly on precursor composition. This study presents an extensive investigation of precursor chemistry, mechanical performance and phase composition, focusing on the partial substitution of ground granulated blast furnace slag (GGBFS) with mechanically activated CDW powder (15% and 30% by weight) alongside fly ash (FA). The oxide composition, amorphous content and particle size distribution were analyzed, using XRF, XRD and laser diffraction to evaluate the reactivity. Mortar samples were subsequently synthesized and tested for compressive and flexural strength, ultrasonic pulse velocity, density and porosity. The results demonstrate that while mechanically activated CDW incorporation decreases early strength compared with GGBFS-rich systems, compressive strengths above 45 MPa were attained at 28 days, with continuous improvement to >69 MPa for aged composites. The relationship between precursor chemistry, precursor sizes and mechanical performance highlights the feasibility of CDW valorization in geopolymer binders, contributing to energy efficiency, circular economy strategies and sustainable construction materials. Full article

This study investigates the use of fly ash to mitigate the long-term performance degradation of Portland cement-based sealing materials in high-salinity environments, such as those found in gas storage reservoirs. We systematically evaluated the evolution of material properties under different temperatures and curing periods. Our integrated methodology combining mechanical tests, microstructural analysis, and chloride migration assessment, reveals a multi-faceted mechanism by which fly ash enhances chloride resistance. The key findings demonstrate that reactive Al₂O₃ in fly ash promotes the formation of Friedel’s salt, increasing chemical chloride binding and reducing the chloride ingress rate in the Portland cement–Fly ash system (PFS) to only 26.6% of that in the Portland Cement system (PCS). Concurrently, the pozzolanic reaction consumes portlandite (Ca(OH)₂), forming stable C-A-S-H gel and refining the pore structure by filling interconnected channels. This nanoscale pore refinement decreased permeability by nearly an order of magnitude. After 90 days of curing in 90 °C saline solution, PFS achieved a compressive strength of 28.2 MPa and maintained an exceptionally low internal chloride content of 0.08 wt.%, demonstrating superior long-term durability. This work clarifies the synergistic mechanisms of fly ash modification and temperature effects, providing a theoretical basis for optimizing sealing materials for deep geological reservoirs and experimental support for the application of fly ash in high-temperature, high-salinity engineering environments. Full article

Skin photoaging, marked by structural and functional changes, is mainly caused by long-term ultraviolet (UV) exposure. This study sought to create hydroxytyrosol (HT)-loaded soluble microneedles (HT MNs) and thoroughly assess their anti-photoaging effects and underlying mechanisms in vitro and in vivo. The optimized HT MNs, featuring tips with 10% HT + 5% hyaluronic acid (HA) and a backing layer of 10% polyvinyl pyrrolidone (PVP), demonstrated robust mechanical strength (withstanding an axial force of 10 N without fracture), adequate penetration depth (>200 μm), and efficient skin self-recovery post-removal. In vitro, HT MNs notably boosted cell viability, reduced reactive oxygen species (ROS) levels, and suppressed senescence-associated β-galactosidase (A-β-Gal) expression in UVA-exposed human skin fibroblasts (HSF). In vivo, in a UVA + UVB-irradiated mouse model, HT MNs significantly enhanced skin hydration and elasticity, increased collagen density (confirmed by Masson staining), decreased malondialdehyde (MDA) content, and elevated the activities of glutathione (GSH), catalase (CAT), and glutathione peroxidase (GSH-Px). Western blot analysis further revealed that HT MNs upregulated the expression of collagen type I alpha 1 (COL1A1), elastin (ELN), hyaluronan synthase 2 (HAS2), and filaggrin (FLG), while downregulating matrix metalloproteinase 1. Overall, these findings suggest that HT MNs effectively mitigate UV-induced photoaging through antioxidant, anti-senescence, and extracellular matrix (ECM)-regulating mechanisms, underscoring their potential as a novel transdermal anti-photoaging therapy. Full article

This study systematically investigated the influence of approach kinematics on the subsequent kinetics and power production strategies during the approach to running jumps with a single leg (ARJSL). Twenty-five physically active male university students performed ARJSL trials under two prescribed approach speeds (fast and slow) and three approach distances (3, 6, and 9 m) in a 2 × 3 within-subjects design. Three-dimensional motion capture synchronized with force platform data was used to quantify jump height (JH), vertical touchdown velocity (TDv), reactive strength index (RSI), peak joint power (hip, knee, and ankle), and joint stiffness. Significant approach speed × distance interactions were observed for JH (p = 0.006), TDv (p < 0.001), RSI (p = 0.014), ankle stiffness (p = 0.006), and peak power generation at all lower-limb joints (all p < 0.034). The results demonstrate that changes in approach strategy systematically alter the distribution of mechanical power among the hip, knee, and ankle joints, thereby influencing the effectiveness of horizontal-to-vertical momentum conversion during take-off. Notably, RSI and ankle stiffness were particularly sensitive to combined manipulations of speed and distance, highlighting their value as neuromechanical indicators of stretch–shortening cycle intensity and joint loading demands. In conclusion, ARJSL performance depends on finely tuned, speed- and distance-specific biomechanical adaptations within the lower extremity. These findings provide a constrained, joint-level mechanical characterization of how approach speed and distance interact to influence power redistribution and stiffness behavior during ARJSL, without implying optimal or performance-maximizing strategies. Full article

The properties of chemically bonded core sands strongly depend on the reactivity of phenol-formaldehyde resole binders and on the granulometry of the sand matrix. This study presents an evaluation of the mechanical, technological, thermomechanical, and thermophysical properties of core sands prepared using two resole binders with different reactivity levels (Resin 1—lower reactivity; Resin 2—higher reactivity) and two fractions of quartz sand (BK 40 and BK 45). The investigations included the kinetics of strength development (1–48 h), friability, permeability, thermal deformation (DMA), and the determination of thermophysical coefficients (λ₂, a₂, b₂) based on temperature field registration during the solidification of a copper plate. The results indicate that sands containing the higher-reactivity binder exhibit a faster early strength increase (≈0.42–0.45 MPa after 1–3 h), whereas sands bonded with the lower-reactivity resin reach higher tensile strength after 24–48 h (≈0.58–0.62 MPa). Specimens based on BK 45 quartz sand achieved higher tensile strength; however, the finer grain fraction resulted in increased friability (up to ≈3.97%) and a reduction in permeability by 30–40%. DMA analysis confirmed that sands based on BK 40 exhibit delayed and more stable thermal deformation. Thermophysical parameters revealed that BK 45 provides significantly higher thermal insulation, extending the solidification time of the Cu plate from 71–73 s to 89–92 s compared with BK 40. Overall, the results indicate that the combination of BK 40 quartz sand and a lower-reactivity resin offers an optimal balance between thermal conductivity and thermal stability, promoting improved technological performance in casting processes. The determined thermophysical coefficients can be directly applied as input data for foundry process simulations. Full article

This study addresses the critical need for advanced biomedical materials that possess both potent antimicrobial properties and high biocompatibility to prevent device-related infections and promote healing. To this end, we demonstrate the successful development and comprehensive characterization of functional composite materials based on a photopolymerizable acrylate resin modified with laser-ablated copper nanoparticles (Cu NPs). The synthesized Cu NPs exhibited a monomodal size distribution with a peak at 47 nm, a high zeta potential of −33 mV, and a spherical morphology. Incorporation of Cu NPs into the polymer matrix via Masked Stereolithography (MSLA) enabled the fabrication of complex structures that maintained high surface quality and optical transparency after polishing. Modification of photopolymer resin with Cu NPs significantly increased the strength of the resulting products and caused dose-dependent formation of reactive oxygen species (ROS). The resulting composite materials exhibited strong antibacterial activity against E. coli. Crucially, despite their potent antimicrobial efficacy, the materials showed no cytotoxicity towards human fibroblast cultures. These results highlight the potential of these composites for a new generation of biomedical applications, such as implantable devices and wound coatings, which combine programmable antimicrobial activity with high biocompatibility. Full article

Red mud (RM), an industrial byproduct generated during bauxite refining, has accumulated to more than 5 billion tons worldwide, posing serious environmental challenges. In response, substantial research over recent decades has focused on the sustainable utilization of RM, particularly in the field of construction materials. This review first summarizes the generation process and chemical composition of RM, and then systematically examines its potential applications in the production of artificial aggregates, partial replacement of cementitious materials, and synthesis of geopolymers. Existing studies demonstrate that RM exhibits considerable potential in construction applications: when used as an aggregate, it can reduce concrete porosity, enhance compressive strength, and improve overall mechanical performance. Moreover, RM can partially substitute cement or serve as a geopolymer precursor, contributing to the immobilization of toxic elements such as Pb and Cr while simultaneously improving the mechanical properties of both cementitious systems and geopolymers. The reactivity and performance of RM-based materials can be further enhanced through carbonation curing and other modification techniques. Finally, this review highlights the significant sustainability and economic benefits of RM-based concrete, supported by life-cycle assessment and cost–benefit analyses. Full article

Petroleum-based plastics are non-renewable and degrade poorly, persisting in the environment and causing serious ecological pollution, so urgent development of alternatives is needed. In this study, all-bamboo fiber thermosetting plastics (BTPs) were successfully prepared through selective sodium periodate oxidation of bamboo fibers followed by hot-pressing. The results demonstrate that the oxidation treatment effectively enhanced fiber reactivity and facilitated the formation of dense composite materials during hot-pressing. Compared with petroleum-based plastics (e.g., PVC), BTPs exhibit outstanding mechanical properties: flexural strength reaches 100.73 MPa, tensile strength reaches 83.31 MPa, while the 72 h water absorption and thickness swelling rates are as low as 5.36% and 4.59%, respectively. This study also reveals the mechanism by which residual lignin affects material microstructure formation through competitive oxidation reactions. Although it imparts initial hydrophobicity, it hinders complete fiber activation, leading to the formation of micro-defects. Furthermore, BTPs can completely degrade in 1% NaOH solution within 24 h, demonstrating excellent degradability. This research provides a new strategy for developing high-performance, degradable all-bamboo-based materials and promotes the value-added utilization of bamboo resources. Full article

This article analyzes the properties of concrete in which up to 25% of natural fine aggregate (sand 0/4 mm fraction) was partly replaced by the crushed tempered glass waste. The granulometric composition of crushed glass waste and 0/4 mm fraction sand was unified to ensure comparable particle size distributions between the natural aggregate and the crushed tempered glass waste. The alkali silica reactivity of crushed tempered glass waste particles was evaluated. The influence of crushed tempered glass waste on the properties of fresh concrete mixture and hardened concrete was determined experimentally. Results have shown that crushed tempered glass waste is non-reactive and can be used in concrete as a partial replacement of natural fine aggregate. Partial replacement of natural fine aggregate with crushed tempered glass waste caused only an insignificant decrease in the density of the concrete mixture, while the entrained air content increased, and the slump decreased more noticeably. The addition of crushed tempered glass waste decreased the density, compressive strength, and depth of water penetration under pressure of all modified concretes. On the other hand, all modified concretes had increased water absorption and closed or total porosities, which improved their durability in terms of the number of freeze and thaw cycles. Full article

As a natural flavonoid compound, quercetin possesses excellent antioxidant, anti-inflammatory and anti-atherosclerotic activities. However, the poor water solubility and sensitivity to the environment severely limit the application of quercetin. Initially, quercetin-loaded zein/carboxymethyl chitosan nanoparticles (ZCQ NPs) were prepared using an anti-solvent precipitation method. The fabricated ZCQ NPs exhibited a small particle size and polydispersity index (PDI). The ZCQ NPs had a negative zeta potential with an absolute value of 41.50 ± 1.76 mV. ZCQ NPs could remain highly stable against light, heat and ion strength. In addition, ZCQ NPs maintained good monodispersity and displayed minimal changes in particle size under long-term storage conditions. Additionally, a superior antioxidant capacity of ZCQ NPs was also observed in the free radical and reactive oxygen species (ROS) scavenging study compared to that of free quercetin. All these results of this study suggest that ZCQ NPs could serve as an effective drug delivery system for encapsulating and delivering quercetin. Full article