Search Results (516)

To investigate the impact resistance of hybrid fiber-reinforced recycled aggregate concrete (RAC) under dry–wet cycles and sulfate attack, hybrid fiber-reinforced recycled aggregate concrete (RAC) was prepared. Dynamic impact compression experiments were conducted using an SHPB test device with a 50 mm diameter. The microstructure of recycled aggregate concrete (RAC) within dry–wet cycles and sulfate attack was examined using SEM. The results indicate that the dynamic compressive strength first rises and then declines with the rise in dry–wet cycles, and increases with the increase in the average strain rate. When the number of dry–wet cycles reaches 16, the dynamic compressive strength reaches its peak, with the B4S6 group achieving a maximum dynamic compressive strength of 59.02 MPa. The dynamic elastic modulus follows a good quadratic parabolic function distribution with respect to the number of dry–wet cycles. Both the incident energy and dissipated energy density initially rise and then reduce with increasing dry–wet cycles. The energy values of RAC with different fiber types follow the order: B4S6 > S6 > B4 > RAC. Under impact loading, the strain rate–strain time history curve of recycled aggregate concrete (RAC) exhibits the change of “increase–decrease–stable–decrease”. With increasing dry–wet cycles, the degree of fragmentation of recycled aggregate concrete (RAC) first increases and then decreases, the fractal dimension first decreases and then increases, and the average particle size first increases and then decreases. SEM results and microscopic reaction mechanisms reveal that in the early stage of dry–wet cycles, sulfate ions generate ettringite and gypsum within the recycled aggregate concrete (RAC), which fill internal cracks and pores, making the concrete denser and enhancing its mechanical properties. Towards the end of the dry–wet cycle, the amount of expansive ettringite and gypsum inside the recycled aggregate concrete (RAC) increases, leading to a sharp increase in pore wall stress, which induces new microcracks in the specimens, manifesting as a decline in mechanical properties at the macroscopic level. 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

Background: Interest in advanced wound dressings for clinical applications is increasing, with biopolymer-based formulations emerging as an effective strategy for wound management. Objectives: This study aimed to develop and characterize sponge-like biopolymeric matrices for the topical delivery of indomethacin as a model anti-inflammatory drug. Methods: Matrices were prepared by combining collagen and methylcellulose (MC) gels in varying ratios, followed by lyophilization. Physicochemical characterization included FT-IR, SEM, contact angle, and water absorption analysis. Biological evaluation involved enzymatic degradation, while biopharmaceutical and pharmacological assessments included in vitro drug release and in vivo testing in Wistar rats with experimentally induced burns. Results: FT-IR analysis confirmed that collagen’s triple-helical structure was preserved in the presence of MC and indomethacin for the samples with maximum 25% methylcellulose. SEM analysis revealed a microporous network with integrated cellulose fibers, where pore size decreased with higher MC content. Compressive strength measurements demonstrated enhanced mechanical resistance with increasing MC content, indicating improved structural stability of the matrices. Moreover, increased MC content led to higher contact angle values but maintained hydrophilicity, while formulations with up to 25% MC exhibited good absorption capacity and structural integrity. Enzymatic degradation studies confirmed that matrices with at least 75% collagen content maintained their structural integrity over time, favoring prolonged application and sustained drug delivery. In vitro drug release followed a biphasic profile, supporting rapid initial anti-inflammatory action followed by gradual release of the drug. In vivo animal studies demonstrated accelerated wound healing in treated rats for all tested matrices. Conclusions: Overall, the developed indomethacin-loaded biopolymeric matrices showed promising structural, functional, and therapeutic properties for effective wound treatment. Full article

High-production wells of deep coalbed methane have been widely reported during the last decade. The Qinshui Basin in China is rich in deep coalbed methane resources, but the pore size distribution characteristics of coal under high-temperature and high-stress conditions remain unclear, affecting the formulation of coalbed methane development strategies. In this study, nuclear magnetic resonance simulations were conducted on anthracite samples from the Zhaozhuang and Sihe mines in the Qinshui Basin under varying temperatures and confining pressures, and the difference in stress and temperature sensitivity of pores with varying sizes was determined. The results show that the pores exhibit strong stress sensitivity but weak temperature dependence. Total porosity decreases with increasing confining pressure, with a maximum damage rate of 6.55%. Pore-size heterogeneity governs differential responses: micropores and macropore fractures show reduced porosity, whereas mesopores exhibit minor increases. Temperature-driven porosity changes occur in distinct phases: at lower temperatures (20–35 °C), damage rates escalate with heating, while at elevated temperatures (35–50 °C), sensitivity diverges due to the variations in native fracture structures. Furthermore, stress and temperature responses correlate with the developmental state of pre-existing pores/fractures and mineral infill. These findings provide critical insights for optimizing coalbed methane exploitation in deep anthracite reservoirs. Full article

To reveal the overtopping dam-break mechanism under extreme rainfall conditions and assess downstream flood risk, a series of dam-break flume tests, flood routing simulations and inundation risk assessments were conducted. Using the Hubuling Reservoir in Rizhao City, Shandong Province as a case study, a circulating extreme rainfall dam-break flume system with a controllable reservoir water level was constructed at a geometric similarity scale of 1:70. Four test conditions were designed: no rainfall and 50-year, 100-year and 2000-year rainfall return periods. Pore water pressure, earth pressure and water content sensors were embedded in critical dam sections to monitor real-time internal dynamic responses. The results show that, due to the combined effect of the highest rainfall intensity, rapid reservoir water-level rise, progressive infiltration-induced weakening and concentrated surface erosion, a dam-break occurs only under the 2000-year rainfall return period. The failure process is divided into four stages: initial infiltration, slope surface scour, overtopping initiation and rapid breach development. Based on dam-break parameters obtained by physical model tests, a two-dimensional numerical using HEC-RAS was conducted. The results show that, under the 2000-year rainfall return period, the flood reaches the downstream area at 80 min after dam failure. The maximum inundation area reaches 15.20 km² at 200 min, with a maximum inundation depth of 11.80 m and a maximum inundation duration of 144 h. By integrating the maximum inundation depth, inundation duration and land use conditions, the expected economic loss is estimated to be 690 million yuan. The results provide important support for dam-break early warnings, emergency management and disaster mitigation of similar small- and medium-sized reservoirs. Full article

This study investigates the effect of mineral additives of different natures, namely blast-furnace slag, fly ash, and bentonite, on structure formation, phase composition, microstructure, and physicomechanical properties of cement matrices. The analysis included measurements of mass change and linear shrinkage during hardening, determination of density and microhardness, X-ray phase analysis, and microstructural examination by scanning electron microscopy. It was found that the introduction of mineral additives reduced linear shrinkage from 6.06 mm for the control composition to 0.25 mm for the composition with blast-furnace slag, 2.31 mm for the composition with fly ash, and 1.01 mm for the composition with bentonite. The maximum density and microhardness values were obtained for the matrix with blast-furnace slag and amounted to 1.99 ± 0.03 g/cm³ and 39.95 ± 1.12 HV1, respectively, whereas the overall range of values for the investigated compositions was 1.52–1.99 g/cm³ and 30.2–39.95 HV1. X-ray phase analysis showed that the amorphous component varied from 61 to 78%, reaching its maximum value in the composition with blast-furnace slag, which is associated with the formation of poorly crystalline C–S–H and aluminosilicate phases. According to the SEM data, the average size of visible pore-like defects was 2.4 μm for the control composition, 1.4 μm for the composition with blast-furnace slag, 1.3 μm for the composition with fly ash, and 1.7 μm for the composition with bentonite. The most favorable combination of high density, microhardness, developed amorphous component, and homogeneous microstructure was established for the composition with blast-furnace slag. The obtained results can be used as a materials-science basis for the development of cement matrices intended for further studies on the immobilization of solid radioactive waste. Full article

Permeability acts as a core parameter governing the efficient and cost-effective development of deep coalbed methane (CBM) reservoirs. The evolution of permeability in deep CBM formations is predominantly driven by the coupled deformation of pore and fracture systems under in-situ stress, yet the intrinsic mechanisms behind this process have not been fully elucidated. In this work, permeability tests were carried out on cataclastic coal specimens in three orientations under both loading and unloading conditions with confining pressures. Experimental results reveal that coal permeability decreases exponentially with increasing effective stress (R² is about 0.99; reduction is about 86%), exhibiting strong anisotropy and displays significant hysteresis during unloading. To interpret these phenomena, we establish a dual-pore fractal series model that uniquely integrates serial flow coupling between matrix pores and fractures and quantifies stress-driven changes in fractal dimension, tortuosity, and maximum pore size. The model successfully reproduces experimental results (mean relative error ≤ 4.2%) and provides mechanistic insights into stress-induced permeability evolution. Stress increases fractal dimension and tortuosity while reducing maximum pore size, rendering pore structures more complex and less conductive. Incomplete recovery of fractal parameters during unloading explains the observed hysteresis. This mechanistic framework, combining the experiment and theory, offers quantitative support for optimizing CBM extraction strategies. Full article

The variation law and mechanism of the permeability characteristics of coal gangue ceramsite lightweight aggregate concrete (CLAC) remain unclear. Therefore, in this study, the effect of the ceramsite size and replacement ratio on the pore structure characteristics of the CLAC was analyzed by mercury pressure test. Moreover, based on a fractal approach, the relationship between permeability characteristics and pore structure of the CLAC was established. The results indicate that incorporating coal gangue ceramsite effectively decreases the maximum pore size. The fractal dimension increases as the replacement ratio of 20–30 mm and 10–20 mm ceramsite rises, whereas an opposite trend is observed when the content of 5–10 mm ceramsite increases. At moderate replacement levels, the introduction of ceramsite aggregates can reduce the fraction of detrimental pores and promote the formation of harmless and slightly harmful pores; however, at high replacement levels, the fraction of harmful and macropores may increase. Moreover, the fractal dimension is negatively correlated with the permeability grade and residual strength, but positively correlated with the strength degradation rate. Full article

Airborne particulate matter pollution has posed severe threats to public health, while conventional air filtration materials suffer from non-biodegradability and poor structural stability. Herein, a series of eco-friendly konjac glucomannan/sodium alginate (KGM/SA) composite aerogels reinforced by silk microfibers (SFs) were fabricated via freeze-drying. The extracted SF had a concentrated diameter distribution of 500 nm, with a well-preserved crystalline structure and the β-sheet secondary structure of natural silk. Results demonstrated that SF incorporation effectively regulated the pore structure, with reduced pore sizes, and an optimized uniform and compact cobweb-like porous network was achieved at 70% SF addition (KSSF₇₀), with a maximum compressive stress of 78.89 kPa at 60% strain, a PM₁₀ filtration efficiency of 99.8%, and a PM_2.5 efficiency of 71.2%. Also, the removal efficiency of particles < 0.3 μm was boosted from 26% to 47% compared with the KGM/SA aerogel. Furthermore, the calculated quality factor met mainstream commercial standards. These findings guided SF use in improving the pore structure of biomass aerogels for enhanced air filtration performance. Full article

Sustainable management of industrial solid waste is critical for a circular economy. This study presents a novel approach for valorizing blast furnace slag (BFS) into NaA zeolite through selective acetic acid leaching followed by hydrothermal crystallization. The leaching step selectively extracts Ca²⁺ and Mg²⁺ while efficiently retaining silicon and aluminum in the solid residue, producing a reactive aluminosilicate precursor that facilitates zeolite nucleation and growth. The effects of the silicon-to-aluminum molar ratio (n(Si)/n(Al)), crystallization temperature, and duration on the phase evolution and morphology were systematically investigated. The results demonstrate that phase-pure NaA zeolite with high crystallinity and a uniform cubic morphology can be obtained from precursor gels with n(Si)/n(Al) ratios of 0.5–1.25. Optimal synthesis conditions were identified as n(Na):n(Si):n(Al):n(H₂O) = 6:1:1:240 at 373 K for 8 h. The resulting zeolites exhibit a BET specific surface area of 52.1 m²/g, a micropore volume of 0.016 cm³/g, an average adsorption pore size of 4.7 nm, and an external specific surface area of 12.8 m²/g. It achieved near-complete removal of Cu²⁺ and high adsorption efficiencies for Pb²⁺ (77.78%) and Ni²⁺ (71.79%) from 250 mg/L solutions at 298 K with a dosage of 4.0 g/L, following the affinity sequence Cu²⁺ > Pb²⁺ > Ni²⁺, with all pairwise differences statistically significant at p < 0.001, using one-way ANOVA and Tukey’s HSD tests. The adsorption of three metal ions was most accurately described by the Freundlich isotherm and pseudo-second-order kinetic models, indicating heterogeneous multilayer chemisorption. The theoretical maximum monolayer adsorption capacities (q_max) were 307.67 mg/g for Cu²⁺, 246.09 mg/g for Pb²⁺, and 173.79 mg/g for Ni²⁺, whereas the kinetic equilibrium adsorption capacities (q_e) reached 62.69, 48.85 and 41.69 mg/g, respectively. This study demonstrates a value-added strategy for valorizing BFS into a micro-mesoporous adsorbent, advancing both circular resource utilization and environmental remediation. Full article

The atypical proliferation of Sargassum (Sargassum spp.) in the tropical Atlantic and the Caribbean Sea over the past decade has triggered an unprecedented environmental and socioeconomic crisis along the Mexican coastline. Continuous beaching events of this macroalga on the Riviera Maya have caused coastal ecosystem degradation, severe impacts on the tourism sector, toxic gas emissions during decomposition, and high cleanup costs. To address this challenge, the valorization of Sargassum as a raw material for synthesizing functional materials represents a sustainable management strategy. In this study, a superabsorbent hydrogel was developed from Sargassum biomass (collected in Cancún, Quintana Roo, in 2025) using an innovative process that bypasses the conventional cellulose isolation step. The biomass was subjected to high-energy milling (15 and 30 min) to prepare Sargassum powder, which was subsequently carboxymethylated using monochloroacetic acid. This modified biomass was then crosslinked with citric acid, a process evaluated at three different citric acid/carboxymethylated Sargassum mass ratios. The hydrogel synthesized with the lowest crosslinking agent ratio achieved a maximum water absorption capacity of 1160 wt%, a value that exceeds the typical absorption capacities of 700–900% for biopolymer hydrogels. Successful material formation was confirmed by Fourier transform infrared spectroscopy (FTIR), which revealed the characteristic functional groups of CMC and the ester bonds formed during crosslinking. Additionally, scanning electron microscopy (SEM) analysis showed a well-defined porous structure with pore sizes ranging from 8.5 to 19.5 µm, which is essential for its high absorption performance. This study demonstrates the feasibility of producing high performance hydrogels from Sargassum through a simplified, cost-effective, and environmentally friendly process. These findings open a promising avenue for the integrated management of this problematic biomass, transforming it into value-added materials with potential applications in agriculture, hygiene, and environmental remediation. Full article

Soils in cold seasonally frozen regions undergo repeated freeze–thaw (F–T) cycles, during which soil moisture content, pore structure, and permeability can change substantially. Previous studies have mainly focused on the mechanical behavior of such soils, whereas few have clarified how moisture content fluctuation regulates pore-structure evolution and permeability response during F–T cycling. In this study, black soil specimens were prepared with initial moisture contents of 15%, 20%, 25%, and 30% on a dry-weight basis and were denoted as 15%-MC, 20%-MC, 25%-MC, and 30%-MC, respectively. The specimens were subjected to 0, 1, 3, 6, 9, and 12 F–T cycles. Mercury intrusion porosimetry, scanning electron microscopy image analysis, and variable-head permeability tests were used to characterize pore-structure parameters and hydraulic responses. The results showed that porosity and mean pore diameter generally increased with increasing F–T cycle number, and the magnitude of these increases depended on the initial moisture content. The 15%-MC group exhibited limited pore expansion, mainly characterized by a transition from micropores to small pores, whereas the 25%-MC and 30%-MC groups developed more mesopores and macropores. In the 30%-MC group, porosity reached its maximum after 9 F–T cycles and then decreased slightly after 12 cycles, indicating particle rearrangement or partial filling of larger pores. The permeability coefficient and cumulative infiltration also increased with increasing F–T cycle number, with more pronounced increases observed in the high-moisture groups. Tukey’s post hoc test showed that the permeability coefficients in the later F–T stages were higher than those in the early stages, particularly in the 25%-MC and 30%-MC groups. Correlation analysis and principal component regression indicated that the permeability coefficient and cumulative infiltration were positively correlated with porosity, mean pore diameter, mesopores, and macropores, but negatively correlated with micropores. Overall, the initial moisture content regulated pore-size redistribution and seepage-channel development, thereby shaping the hydraulic response of black soil under repeated F–T cycling. Full article

The surface functionalization of mesoporous bioactive glasses (MBGs) is of critical importance for the development of advanced hybrid biomaterials with controlled interfacial and adsorption properties. Composite systems based on MBGs modified with cucurbit[n]urils (CB[6], CB[7], and CB[8]) were synthesized and systematically investigated to elucidate size-dependent interaction mechanisms and their influence on textural and physicochemical characteristics. Functionalization was achieved via aqueous deposition followed by controlled thermal treatment. Nitrogen sorption analysis revealed distinct pore modification behaviors: CB[6] reduced the specific surface area by 64% with partial pore occupation; CB[7] induced extensive mesopore occlusion (92.4% surface area reduction); whereas CB[8] produced a balanced decrease (71.2%) while largely preserving microporosity. Thermogravimetric analysis demonstrated comparable loading for CB[7] and CB[8], yet MBGs@CB[8] exhibited enhanced thermal stability, with the DTG maximum shifted to ~395 °C. Molecular modeling supported these findings, indicating the lowest adsorption energy for CB[8]. This combination of structural preservation and enhanced stability provides the most favorable balance between pore accessibility and structural modification, demonstrating strong potential as a versatile modifier for subsequent functionalization, including drug loading applications in bone-regenerative systems. Full article

Achieving the coexistence of high energy density and fast-charging capability remains a fundamental challenge for lithium-ion batteries. Increasing electrode thickness and compaction density enhances energy density but simultaneously alters the pore structure and restricts lithium-ion transport, leading to concentration polarization, increased resistance, and lithium plating. In this work, we employ X-ray computed tomography (X-CT) and 3D reconstruction to establish quantitative relationships between particle size, compaction density, and key structural parameters (porosity, tortuosity, effective proportion of lithium-ion flux (f_eff)). Then, an electrochemical model is used to link the liquid-phase kinetic parameters (ionic conductivity (k₀) and liquid-phase diffusion coefficient), as corrected by the effective proportion of lithium-ion flux f_eff, to polarization and lithium-plating behavior, and the maximum current density without lithium plating under various fabrication conditions is finally determined. Results show that small-particle electrodes exhibit superior rate capability at moderate compaction levels, but suffer from rapidly increasing tortuosity and reduced transport efficiency under high compaction and large thickness. Moreover, a double-layer gradient electrode design effectively integrates the advantages of both large- and small-particle architectures, enabling high-rate operation without lithium plating. The double-layer gradient electrode (ρ = 1.6 g/cm³) exhibited ~50% higher performance at 1.5 C compared to the small-particle anode and enabled 2 C charging without lithium plating. This study offers a robust structural design strategy for optimizing thick-electrode architectures toward high-energy, fast-charging LIBs. Full article

Red mud, as a by-product of alkaline regeneration of alumina, has limited application due to its strong alkalinity, fine particle size, and complex composition. In this work, red mud porous ceramics with uniform pore size distribution and high mechanical strength were prepared using a foam-gel casting method. The effects of solid loading and sintering temperature on the microstructure of porous ceramics were systematically investigated. The porosity of red mud-based porousceramics sintered at 1150 °C with a solid content of 60.4% was 33.7%, and the maximum compressive strength was 54.70 MPa, while the porousceramics prepared with a solid loading of 34.1% and sintered at 1050 °C achieved a maximum porosity of 79.7% and a compressive strength of 2.36 MPa. Increasing the solid loading reduced porosity and enhanced compressive strength, allowing for the tailoring of mechanical properties to meet specific application requirements. Higher sintering temperature promoted the formation of the liquid phase, enhanced particle bonding, and further improved the compressive strength. Additionally, toxicity leaching tests confirmed that the ceramics are environmentally safe, with leachate levels well within regulated limits. These results demonstrate the potential of foam-gel casting as an effective route for transforming red mud into value-added porous ceramics, thereby contributing to sustainable waste utilization and broadening the application prospects of red mud-based materials. Full article