Search Results (1,569)

This research addresses the critical challenge of “strength regression” observed in alkali-activated binders synthesized from glass wool wastes. In our preliminary studies, while sodium-based activation provided impressive initial strength, the specimens suffered a systematic and significant decline in mechanical performance at 3, 7 and 28 days, exhibiting a 74.3% strength reduction down to 24.61 MPa. Investigative analysis revealed that this instability is closely correlated with the physical degradation and micro-cracking observed in SEM micrographs, which is consistent with the literature regarding high silica-to-alumina network imbalances. To resolve these structural flaws, the precursor blend was modified by incorporating Class F fly ash and metakaolin to rebalance the Si/Al ratio. The addition of these aluminosilicate sources facilitated the consumption of excess sodium ions through enhanced geopolymerization and provided a micro-filling effect that refined the pore structure. Our findings demonstrate that this optimization not only prevents the subsequent loss of strength but also ensures stable compressive strength development up to 28 days without subsequent regression, reaching an ultimate average strength of 110.81 MPa. This approach provides a viable pathway for transforming insulation glass wool waste into high-performance, durable construction materials. Full article

Flexible pressure sensors serve as core sensing components for wearable health monitoring systems, electronic skins for soft robots, and flexible human–machine interaction devices. Benefiting from the interfacial electric double-layer polarization effect, iontronic sensing delivers far higher pressure response sensitivity than conventional parallel-plate capacitive sensors, endowing it with distinctive advantages in the detection of weak physiological signals. Nevertheless, current dense ionic thin-film dielectric layers suffer from limited deformation space under compression and poor low-pressure sensing capability. Mainstream high-precision micropillar arrays are fabricated via photolithography, 3D printing, and metal etching molds, which require costly equipment and complicated fabrication procedures, making large-area mass production unfeasible. Random frosted concave-convex microstructures feature disordered dimensions, leading to severe device hysteresis and narrow linear ranges, which fail to achieve ultrahigh sensitivity alongside a wide pressure detection range simultaneously. To address the aforementioned multiple bottlenecks, this paper proposes a low-cost resin template replication process to fabricate TPU-based ionic thin-film dielectric layers with ordered micropillar array microstructures. Combined with inkjet-printed silver conductive PI flexible electrodes, an iontronic flexible pressure sensor with a sandwich layered structure is constructed. Multi-dimensional investigations including microscopic morphology characterization, electromechanical sensing performance calibration, and human wearable application tests are systematically implemented to thoroughly elucidate the synergistic enhancement mechanism of the arrayed micropillars. Test results demonstrate that the effective pressure detection range of the sensor spans 0–1038 kPa, accommodating ultra-low pressures such as pulse signals as well as medium-to-high-pressure loads including joint bending. The sensitivity reaches 23.27 kPa⁻¹ within the low-pressure range of 0–200 kPa and remains stable at 3.52 kPa⁻¹ in the high-pressure range of 200–1038 kPa, with piecewise linear fitting correlation coefficients of 0.93 and 0.96 respectively. Both the response time and recovery time of the device are 40 ms, and the hysteresis error throughout the loading-unloading cycle is merely 2.62%. After 20,000 consecutive cyclic loading-unloading tests, the peak capacitance output only decays by 5.1%, verifying outstanding mechanical fatigue resistance and electrical stability. Validations in multi-scenario applications prove that the sensor can accurately capture human physiological and motion signals including radial artery pulses, laryngeal deformation induced by multi-syllable vocalization, and multi-angle bending of fingers and elbow joints, suitable for home-based health monitoring, quantitative rehabilitation training, flexible tactile interaction and other scenarios. The entire fabrication process eliminates high-precision micro-nano processing equipment such as photolithography systems, plasma etchers and 3D printers; only general chemical raw materials and conventional laboratory instruments are adopted. The reusable templates enable low manufacturing costs and large-area coating forming, offering a novel low-cost technical solution for the engineering implementation and industrialization of high-performance iontronic flexible pressure sensors. Full article

To investigate the elevated-temperature performance of Ultra-High-Performance Concrete (UHPC) and Ultra-High-Performance Geopolymer Concrete (UHPGC), a systematic comparative study was conducted at 800 °C. This study examined the effects of the steel fibre geometry (micro and hooked-end) and dosage (1.5% and 2.0%) on mass loss, crack propagation, residual compressive, flexural, and tensile strengths, and chemical evolution following a 24 h pre-drying protocol to mitigate explosive spalling. The results demonstrate that UHPGC exhibits superior thermal stability and residual mechanical performance compared with UHPC after high-temperature exposure. Among all mixtures, the UHPGC mixture reinforced with 2% micro steel fibres (UHPGC-M2) achieved the highest residual compressive strength (30 ± 0.4 MPa, corresponding to 25% strength retention compared with 21% for the equivalent UHPC mixture), the lowest post-exposure crack width (0.08 mm), and the highest tensile strength retention (17.9%). Micro steel fibres were more effective in controlling crack propagation and preserving peak load capacity, whereas hooked-end fibres contributed more significantly to post-peak ductility. Chemical analysis revealed substantial chemical changes in both systems after exposure to 800 °C. However, UHPGC exhibited lower mass loss (4.8%) and greater residual performance. These findings establish micro steel fibre-reinforced UHPGC as a sustainable and high-performance material for fire-resistant structural applications. Full article

One-part geopolymer mortars provide an alternative to cementitious materials by using dry activators and industrial by-products. This study evaluated a multi-precursor matrix containing slag, fly ash, ceramic powder, red mud, and 5% MgO, reinforced with polyvinyl alcohol (PVA), basalt, or micro-steel fibers at 0.4% and 0.8% by volume. Specimens were cured at 20 ± 2 °C or at 80 °C for 24 h and assessed for flowability, mechanical properties, ultrasonic pulse velocity (UPV), Böhme abrasion, 24 h water absorption, and sorptivity. XRD, FTIR, and SEM/EDS were used only to compare by heat-cured mixtures. The results showed that at 28-day, heat curing increased compressive strength by 39.5–71.8%, flexural strength by 29.2–134.4%, and UPV by 20.5–36.4%, while reducing sorptivity by 12.2–35.7% relative to ambient curing. PVA reduced flowability likely because of its hydrophilic surface and high surface area. For 0.8PVA, the flow diameter was 23.6% below the reference, whereas the 28-day heat-cured flexural strength reached 7.5 MPa, with the lowest abrasion thickness loss of 0.63 mm. Micro-steel mixtures maintained compressive strength comparable to the reference, reaching 72–73 MPa at 28-day. Heat curing reduced water absorption in PVA and basalt mixtures, whereas the reference and micro-steel mixtures showed insignificant change. Microstructural analyses suggested the formation of a more compact and reacted aluminosilicate matrix under heat-cured conditions. A screening life-cycle assessment, limited to the non-fiber-reinforced reference matrix, showed that heat-curing increased global warming potential by 7.6%, while the two solid activators contributed approximately 45% of the ambient-cured reference GWP. The findings indicate that heat curing significantly enhances the performance of one-part geopolymers, while fiber selection provides additional mechanical and durability improvements. Full article

Screen content images (SCIs) exhibit complex structural heterogeneity, rendering traditional statistics-based natural scene image quality assessment (NR-IQA) metrics ineffective. Although deep learning models achieve high prediction accuracy, their prohibitive computational demands preclude deployment in latency-sensitive industrial scenarios. While existing handcrafted lightweight SCI-IQA metrics reduce computational overhead, most rely on unsegmented global feature pooling or holistic edge statistics (e.g., edge histograms or Fisher vector coding), thereby diluting locally critical text-edge distortions in vast homogeneous backgrounds. To address this limitation, we propose an ultra-lightweight, deep-learning-free NR-IQA framework centered on human visual masking. Unlike existing lightweight methods, our approach explicitly employs dual-scale Canny edge operators to partition SCIs into edge-sensitive and flat background regions. Guided by this visual prior, structural degradations and micro-compression textures are extracted region-wise using Sobel gradients and uniform local binary patterns (LBPs) and aggregated with global Commission Internationale de I’Eclairage L*a*b*(CIELAB) color statistics into a compact 60-dimensional descriptor. A grid-search-optimized Support Vector Regression (SVR) maps these features to subjective quality scores. Extensive cross-validation on the SIQAD and SCID datasets demonstrates that our metric outperforms existing handcrafted lightweight SCI metrics and traditional NSS models, while achieving accuracy competitive with representative full-reference metrics. Consuming only 79.3 ms per image on a standard CPU, it offers a practical accuracy–efficiency trade-off for resource-constrained periodic quality monitoring. Full article

Concrete structures are prone to cracking during service, and epoxy grouting is a widely adopted technique for structural intervention. However, the inherent brittleness and poor durability of neat epoxy under complex loading and environmental exposure remain critical challenges. This study systematically evaluates the mechanical performance of epoxy-grouted concrete interlayer systems modified by carbon fiber (CF), glass fiber (GF), and polyethylene microspheres (PE). A comprehensive experimental program was conducted, including compression, three-point bending, and Brazilian splitting tests at three loading angles, combined with digital image correlation for surface strain monitoring. The effects of grout thickness and wet–dry cycles were systematically investigated. Results demonstrate that reinforcement modification helps to improve the performance of grouted concrete, with optimal behavior highly dependent on loading mode. CF-reinforced specimens with strong interfacial bonding exhibit the highest compressive strength, which is 150% higher than the bearing capacity of intact concrete, but are prone to brittle fracture under loading involving tension-shear interaction. GF reinforced specimens with moderate interfacial bonding exhibit better load-bearing capacity under tensile-shear stress interaction, reaching a normalized splitting peak load of 0.95 at a grouting thickness of 5 mm. PE-reinforced specimens with weak interfacial bonding provide relatively extensive energy dissipation. A 3 mm grouting layer shows favorable performance among the tested thicknesses, balancing load transfer enhancement and defect control. A single wet–dry cycle temporarily improves performance, possibly due to epoxy post-curing and pore filling, whereas repeated cycling generates cumulative micro-damage. GF- and CF-reinforced systems demonstrate the most stable resistance to short-term wet–dry conditioning. These findings provide guidance for loading-mode-dependent reinforcement selection in epoxy grouting applications. Full article

Polymer modifiers and carbon-based materials have been widely proposed as potential asphalt additives to improve performance. However, limited studies have systematically compared micro- and nanocoke from different sources in combination with SBS and Elvaloy polymers or linked binder rheology with mixture performance. To address this gap, this study investigated the effects of micro- and nanodispersed petroleum and coal coke combined with SBS and Elvaloy polymers on the rheological behavior of asphalt binders and the performance of asphalt concrete mixtures. Rheological properties were evaluated by dynamic shear rheometer (DSR) testing, and asphalt concrete mixtures were tested for compressive strength and crack resistance. The modified systems were successfully used to obtain commercial polymer-modified bitumen grades: BMP 70/100, BMP 50/70 and BMP 35/50. With 1 wt.% micro coal coke and 0.1 wt.% SBS modification, a softening point of 73.7 °C and a penetration of 22.3 × 0.1 mm was observed. Micro coal coke–SBS system showed the highest compressive strength at 20 °C (3.29 MPa), while the largest crack resistance (4.39 MPa) and the best high-temperature mixture strength (0.90 MPa at 50 °C) were obtained when 0.5 wt.% nanocoke and 0.5 wt.% Elvaloy are used. These findings demonstrate that hybrid coke/polymer modification is an effective approach for enhancing asphalt performance, with micro coal coke–SBS systems providing the highest stiffness and rutting resistance, while nanocoke–Elvaloy systems delivered superior crack resistance and overall performance balance. Full article

Carbon black (CB) nanoparticles (~20 nm) offer high specific surface area and conductivity for self-sensing cementitious composites, but strong interparticle van der Waals forces drive agglomeration in alkaline pore solutions, limiting sensing reliability. This study introduces a nanoscale interfacial engineering strategy in which CB nanoparticles are adsorbed onto polypropylene (PP) fiber surfaces as spatially organized conductive elements, with EDS evidence of enhanced hydrate coverage at the fiber–matrix interface. Three CB dosages (0.5%, 1.0%, and 1.5% by binder mass) with 0.5% PP fiber were investigated. Nanoparticle coating and interfacial micro-structure were characterized by SEM-EDS, while FTIR was used to verify that the fiber backbone remained chemically unmodified; piezoresistive response and durability were assessed via cyclic compression, DIC, and hygrothermal cycling. The 1.0% CB nanocomposite lies within the effective percolation window (~0.9–1.2%), showing high linearity, a stable gauge factor (~100), and distinct FCR acceleration for early-warning sensing. The 1.5% CB composite yields higher sensitivity but scattered responses due to nanoparticle clustering; 0.5% CB remains below the percolation threshold with a discontinuous network. After 60 hygrothermal cycles, the 1.0% nanocomposite retains >93% of its gauge factor with minimal resistance drift. The nano-engineered CB–PP fiber architecture offers a scalable route integrating crack bridging, percolation networking, and durable self-sensing in cementitious nanocomposites for structural health monitoring. Full article

A Nomex aramid paper honeycomb sandwich structure is the core material of the main load-bearing structures in aviation. Macroscopic full-scale refined modeling faces the problems of large mesh quantity and high calculation cost. Homogenization equivalence is the core path to achieve its efficient simulation design. Most of the existing mature equivalent models are based on the ideal assumption that the honeycomb always remains macroscopically straight, without considering the equivalent performance changes caused by the morphological distortion of micro-cells under bending conditions. Therefore, it is difficult to support a high-precision simulation of large-curvature special-shaped honeycomb sandwich structures. This paper takes the over-stretched rectangular lattice aramid honeycomb as the research object. The mechanical parameters of the matrix are calibrated through experiments, and the reliability of the fine shell finite element model is verified (the maximum error of the end-face strain characteristics between simulation and the DIC test is less than 10%). A customized finite element sample matrix for compression bending is designed, and the angle distribution laws of honeycomb cells under different thicknesses and different bending curvatures are extracted. It is found that the cell angle shows a linear change trend along the wall-thickness direction, which is only strongly correlated with the initial geometric parameters and the bending radius. Finally, a semi-empirical model that can quickly predict the morphology of bent honeycomb cells is obtained through fitting. Verified by the glass compression-molding visualization experiment, the maximum relative error of the predicted cell angle is only 5.05%. This research establishes a rapid characterization method for the deformation of honeycomb cells under bending deformation, providing theoretical support for the microscopic homogenization equivalent modeling of curved honeycomb sandwich structures. Full article

The development of sustainable, high-performance friction composites is critical for the automotive industry, given the environmental and health concerns associated with conventional brake pad materials such as asbestos and copper. This study investigates the effect of incorporating micro- and nano-sized Al₂O₃, SiC, and carbon nanotubes (CNTs) into a novel, eco-friendly, asbestos-free, and copper-free brake pad formulation. Six composite samples were fabricated via a cold-pressing and hot-molding process: five formulations containing a single, size-controlled micro-/nano-sized reinforcement (Al₂O₃, SiC, and CNTs), and one reference formulation (CBP# Reference) containing an unrefined, commercial-grade combination of Al₂O₃ and SiC in place of the size-controlled additive. All formulations were rigorously characterized for their physical, mechanical, and tribological properties. The nano-Al₂O₃ formulation exhibited the highest density (2.197 g/cm³) and compressive strength (249.7 MPa), while the micro-SiC formulation achieved superior wear resistance, recording the lowest weight loss (0.0053 g) and the highest hardness (90 HV). The nano-SiC formulation offered the most balanced overall performance, combining high hardness (86.2 HV) with the highest average friction force (33.65 N) and the most stable friction-time response among all samples. The CNT-reinforced formulation produced the highest maximum friction force (42.07 N) but showed only moderate improvement in density, hardness, and compressive strength relative to the ceramic-reinforced samples. Compared with the CBP# reference, all five developed formulations exhibited higher hardness and coefficient of friction alongside lower weight loss, confirming their potential as durable, sustainable alternatives for automotive brake friction applications. Full article

The severe early-age shrinkage of alkali-activated slag is a primary bottleneck restricting its engineering application. In this work, a novel shrinkage control strategy is proposed, dominated by the physical control of vacuum dehydration and assisted by the chemical compensation of MgO. The synergistic mechanism of this strategy in the AAS system was revealed by multi-scale characterization methods (XRD, FTIR, TG, NMR, BSE, and pore solution analysis). Firstly, vacuum dehydration greatly advances the development window of capillary pressure to the early stage (<6 h) of the material in the significant viscoelastic stage by forcibly removing free water between the interlayer and capillary pores. Most of the shrinkage strain energy can be dissipated through the early creep behavior of the slurry, and the strong negative pressure induces the conversion of mesopores to macropores, thereby effectively reducing the equilibrium capillary cracking driving force. Secondly, the late hydration of an appropriate amount of MgO generates magnesium silicate and hydrotalcite phases, which provide a continuous chemical micro-expansion for the matrix to compensate for residual shrinkage and moderately optimize the local pore defects induced by dehydration. The results show that in the sodium silicate solution and sodium hydroxide activating system, the synergistic effect reduces the total shrinkage rate of 28 days by 37.86% and 29.26%, respectively. Additionally, the compressive strength of hardened samples increases by about 20%. This study provides a new theoretical basis for the design of low-shrinkage and high-performance alkali-activated materials based on the physical–chemical coupling mechanism. Full article

Online detection of micro-leakage in complex high-pressure gas pipeline networks is difficult to achieve using conventional methods. A high-pressure pipeline micro-leakage detection method based on background-oriented schlieren measurement and feature matching was proposed in this study to address this issue. Through the BOS measurement, the density distribution of the leakage fields was reconstructed through cross-correlation calculation and Poisson equation solving, which was further compared with numerical simulation results under specific operating conditions. The morphological characteristics of the jet field at different leakage pressures were revealed by comparing the density fields from different experimental conditions. Subsequently, the displacement field data were compressed into one-dimensional feature representations for structure-oriented matching of leakage-field characteristics, with temporal smoothing and a dual-threshold hysteresis strategy incorporated to improve matching robustness. The results show that the error in the peak density remains below 10%, which indicates good consistency between the background-oriented schlieren measurements and the numerical simulations. Meanwhile, the one-dimensional feature curve accelerates computation while retaining the dominant characteristics of the leakage field. The proposed framework achieves an area under the ROC curve of 0.992 and an average precision of 0.998. At the selected threshold of 0.650, the overall evaluation metric reaches 0.972, reflecting a favorable balance between sensitivity and reliability. Furthermore, the temporal stabilization strategy improves alarm continuity and suppresses chattering during detection. Full article

Fiber-reinforced plastics (FRPs) exhibit significantly lower compressive strength than tensile strength, mainly because of fiber micro-buckling. During compressive failure, fiber micro-buckling leads to the formation of a kink band, in which fractured fibers are reoriented at a constant angle. Previous studies have shown that compressive strength and the fiber collapse direction are affected by initial fiber misalignment and remote shear stress, and that kink-band formation can induce subsequent damage, such as delamination. In this study, a three-dimensional mesoscale constitutive model is developed to represent these compressive failure mechanisms by introducing a coupling term between longitudinal normal stress and shear strain. The formulation is implemented in a numerical framework using a user subroutine in a commercial finite element solver. Numerical examples demonstrate that the proposed model reproduces the dependence of compressive failure behavior on both initial fiber misalignment and remote shear stress. Comparisons with experimental observations indicate the potential of the proposed model to predict compressive strength, while qualitatively capturing the interaction between compressive damage and delamination. Full article

Acoustic emission (AE) measurements are commonly used in studies of cementitious composites subjected to various types of loading. Recording macrocracks that result in a decrease in stress is not relatively difficult. This paper focuses on the possibility of identifying micro-events and microcracks during the compression of concrete with dispersed reinforcement. Most AE studies on cement composites correspond to a reduction in stress exceeding the elastic range defined by Hooke’s law, typically associated with the formation of the first crack and detected in the medium- and high-frequency ranges. However, identifying micro-events which do not reduce stress beyond the elastic range is difficult. This study demonstrates that such micro-events can be detected using low-frequency sound and infrasound. In many papers, medium- and high-frequency acoustic signals are effective for recording macrocracks or reinforcement damage. In this work, a 3D acoustic spectrum was used to analyze recorded data in the infrasound range in a concrete compressive test. This approach proved to be the most effective method for determining the critical point f_cr (the end of the elastic range) regarding low-intensity micro-events and microcracks. This type of micro-damage has no significant influence on the linear stress–strain correlation at f_cr. The results indicate that identifying micro-events and low-intensity microcracks using medium- and high-frequency acoustic signals is not possible and that infrasound should be considered for the detection. Significant differences in stress and displacement corresponding to f_cr and f_max were confirmed in concrete compressive tests. The results indicate that accurately determining f_cr is required for correctly assessing the durability of cementitious composites. Full article

Low-cost and effective F⁻ removal technology and operational parameters were provided. A novel bimetallic fluoride-removing coagulant (BFrC) was synthesized. Simultaneous removal of fluoride (F⁻) and turbidity were studied using a new integrated coagulation–adsorption technology based on BFrC (BFrC-“Coagulation-driven adsorption” system (BCS)) in treating low-temperature and low-turbidity waters, in which a “Coagulation-driven adsorption” was the key point. Optimal conditions of the BCS were determined, and Zeta potential and meso- and micro-scopic morphologies were characterized. The results showed BFrC was hydrolyzed and hydroxylated to form positively charged flocs, and BCS reduced residual F⁻ concentration to <1 mg/L. The in situ flocs formed in the BCS (BCS-flocs) gave a very large surface area, providing abundant adsorption sites and channels for F⁻. Neutral water environment (7.5–8) was conducive to remove F⁻, while neutral and alkaline conditions are beneficial for turbidity removal. The BCS exhibited strong adaptability to varying water temperatures and turbidity levels. Higher initial turbidity in test waters improved F⁻ removal, while elevated initial F⁻ levels linearly reduced F⁻ removal. Divalent anions (SO₄²⁻) inhibited defluoridation more significantly than monovalent anions (Cl⁻ or HCO₃⁻). The BCS-flocs effectively removed F⁻ and turbidity simultaneously, in which F- removal was achieved through adsorption on the flocs, maybe including a combination among initial chemical adsorption, subsequent physical adsorption, and complex composite adsorption, and turbidity removal mainly relied on a multi-mechanism process, including double-layer compression, charge neutralization, and sweep flocculation. Full article