Search Results (15,529)

This study provides computational insights into the flexural strengthening of reinforced concrete (RC) T-beams in the negative moment region using steel-reinforced polymer cement mortar (PCM) overlays. A validated three-dimensional nonlinear finite element (FE) model was developed using the Advanced Tool for Engineering Nonlinear Analysis (ATENA) software (version 2023.0.0.22492) to simulate the behavior of beams retrofitted with 40 mm thick PCM layers embedded with 13 mm and 16 mm deformed bars. Model validation was performed against previously published experimental results reported by the authors, demonstrating excellent agreement, with normalized mean square error (NMSE) values expressed as fractions between 0.0001 and 0.0022, and experimental-to-numerical ultimate load ratios ranging from 0.99 to 1.01. Parametric analyses were then conducted to investigate the influence of key variables, concrete compressive strength, PCM overlay thickness, and longitudinal reinforcement ratio on the global flexural performance. The results revealed that increasing the overlay thickness raised the ultimate load capacity by up to 15.4% and improved energy absorption by 43%. Enhancing concrete strength led to gains of up to 12.5% in load capacity and 15.8% in stiffness. Variations in reinforcement ratio had the most significant impact, increasing peak load by up to a factor of 2.02 and improving energy absorption by up to a factor of 1.49. Despite these improvements, reductions in ductility were observed across all strengthening configurations, underscoring a strength–deformability trade-off critical for seismic applications. These findings affirm the efficacy of steel-reinforced PCM overlays and provide design-oriented insights for optimizing negative moment retrofitting strategies in RC bridge girders and continuous beam systems. Full article

Wood used in construction varies in density, leading to differences in strength and rigidity. Wood densification has recently emerged as a promising technique to address these limitations and enhance material performance. This study explores the potential of two abundant and low-cost invasive hardwood species in South Africa—Prosopis glandulosa (Honey Mesquite) and Acacia mearnsii (Black Wattle)—as sources for producing densified wood. A range of strengthening methods, including chemical, pressure, and heat treatments, were applied and compared. After partial delignification and hot pressing, sample thicknesses were reduced by 40% for Prosopis and 50% for Acacia, yielding substantial increases in flexural strength of 216% (22.61 MPa) for Prosopis and 334% (24.65 MPa) for Acacia. In addition to SEM anatomical imaging, analyses of lignosulphonate content, and thermogravimetric profiling, the study also evaluated several practical, carpentry-relevant mechanical properties. These included comparative tests for flexural and compressive strength, nailing and sanding performance, as well as assessments of water absorption, electrical resistivity, and flame-holding capacity. Full article

Adiabatic shear banding (ASB) is a critical failure mechanism in titanium alloys subjected to high-strain-rate deformation, and its initiation is strongly influenced by the initial crystallographic texture. The dynamic response and ASB sensitivity of extruded and annealed Ti-6Al-4V (TC4) alloy rods were investigated under dynamic compression of cubic specimens along the extrusion direction (ED) and the transverse direction (TD) at a strain rate of 2500 s⁻¹. Split Hopkinson pressure bar (SHPB) tests combined with digital image correlation (DIC) were employed to obtain the stress–strain response and the evolution of strain localization. A dislocation density-based crystal plasticity finite element model (CPFEM), incorporating the measured texture, was established to elucidate the correlation between texture and ASB behavior. The experimental results show that TD specimens exhibit a yield strength approximately 100 MPa higher than that of ED specimens, while both orientations display comparable post-yield hardening behavior. ASB initiation occurs earlier in TD (compressive strain ~0.13) than in ED (~0.23), indicating greater ASB sensitivity in the TD orientation. The CPFEM successfully reproduces the directional stress–strain responses and the observed localization morphology, enabling mechanistic interpretation in terms of slip activity and thermomechanical coupling. The simulations indicate that ED loading is dominated by prismatic ⟨a⟩ slip, resulting in lower flow stress and more dispersed strain localization. In contrast, TD loading is governed primarily by pyramidal ⟨c + a⟩ slip, leading to elevated flow stress and intensified localization. The higher ASB sensitivity in the TD orientation is therefore attributed to texture-controlled slip-mode partitioning, enhanced thermomechanical coupling, and a more concentrated crystallographic orientation distribution that facilitates intergranular slip transfer. These findings provide guidance for tailoring microtexture to mitigate dynamic failure in titanium alloys subjected to high-strain-rate loading. Full article

Standard maturity methods for concrete monitoring rely primarily on temperature history, often neglecting the influence of internal relative humidity (RH) on hydration kinetics and self-desiccation risks. Continuous in situ monitoring of internal RH remains a challenge due to the high cost, proprietary nature, and lack of reproducibility of existing solutions. This study evaluates a low-cost, open-source embedded sensor array designed to characterize early-age curing behavior through trend-based monitoring—defined here as the evaluation of ensemble consistency and repeatability rather than absolute metrological traceability. The prototype system, based on SHT31 sensors controlled by an ESP32 microcontroller, was embedded in high-performance concrete cylinders (f′c = 45 MPa) to capture the exothermic hydration peak and the equilibration of internal humidity. Results demonstrate that while the sensor encapsulation introduced a geometric disturbance that reduced compressive strength by approximately 25%—a limitation requiring mitigation in structural applications—the system successfully captured reproducible curing transitions. The proposed framework provides an accessible tool for experimental research into internal curing conditions, offering a digital complement to traditional surface-based quality control. Full article

Ultrasonic Impact Treatment (UIT), a prevalent surface-strengthening technology for welded structures, combines mechanical shock and ultrasonic vibration to induce plastic deformation and beneficial residual compressive stress at weld toes, effectively enhancing welded joint fatigue performance. This study adopts a full-process numerical simulation approach, integrating the finite element software ABAQUS and FE-SAFE fatigue-life prediction platform to investigate QSTE700TM high-strength automotive steel butt joints. Considering welding-induced initial residual stress, ABAQUS simulates the welding and subsequent UIT processes; explicit dynamic analysis reveals residual stress evolution, with pre- and post-UIT stress-distribution comparisons. The post-UIT residual stress field is input into a static tensile model to obtain load-stress distributions, which are then imported into FE-SAFE with S-N curves for fatigue-life prediction. Simulation results align well with experimental data: UIT improves the fatigue limit of welded specimens by 31.3% and unwelded ones by 42.9%. Additionally, optical and scanning electron microscopes observe fatigue fracture morphologies to further clarify UIT’s fatigue-enhancement mechanism. Full article

Nickel-titanium (NiTi) alloys are attractive for functional and biomedical applications due to their shape memory effect, superelasticity, and favorable corrosion resistance and biocompatibility. In this work, the influence of strut size on the compressive response of laser-based powder bed fusion (PBF-LB/M) fabricated NiTi ortho-octahedral porous scaffolds was systematically investigated using combined experiments and finite element simulations. Four scaffold designs with identical unit-cell size (2 mm) but different strut sizes (280, 320, 360, and 400 μm) were fabricated, and their forming quality and deformation behaviors were examined. The as-built scaffolds exhibited high geometric fidelity to the CAD models and stable manufacturability across the investigated parameter range. Quasi-static compression tests revealed a typical three-stage response (linear-elastic regime, plateau/collapse regime, and densification), with both elastic modulus and compressive strength increasing markedly with strut size. Specifically, the modulus increased from 1.17 to 4.28 GPa and the compressive strength increased from 155 to 564 MPa as the strut size increased from 280 to 400 μm. A pronounced oscillatory plateau was observed for the 280 μm scaffolds, indicating progressive layer-by-layer collapse, whereas larger struts promoted a shear-band-dominated failure mode characterized by an approximately 45° fracture zone. Explicit quasi-static simulations reproduced the experimentally observed collapse sequence and demonstrated that stress preferentially concentrates at nodal junctions, with load transfer dominated by struts aligned with the loading direction. The agreement between experiments and simulations confirms the predictive capability of the proposed modeling framework and provides mechanistic insights into geometry-controlled failure. These findings establish a structure-property-failure relationship for PBF-LB/M-fabricated NiTi octahedral scaffolds and offer practical guidance for tailoring stiffness, strength, and collapse mode through strut-size design. Full article

To investigate the mechanical properties of steel fiber-reinforced concrete under freeze-thaw cycles and the accuracy of its finite element simulation, a constitutive model and its functional expressions for steel fiber-reinforced concrete under tension and compression before and after freeze-thaw cycles were developed. This was based on the stress-strain curve characteristics obtained from experiments, combined with the Hognestad model, the Guo Zhenhai model, and the tensile-compressive model. Finite element simulations were conducted using ABAQUS to model the evolution of the mechanical properties of the lining structure during freeze-thaw processes, revealing the damage characteristics and failure modes of the lining mechanical properties induced by freeze-thaw cycles. The results indicated that after experiencing freeze-thaw cycles, the peak strength of the specimens decreased from 43.3 GPa to 35.3 GPa. Validation through scaled model tests confirmed that the established constitutive model and the corresponding finite element method accurately reflect the cumulative process of freeze-thaw damage, with the numerical simulation results showing good agreement with the experimental data. This study verifies the feasibility of accurately simulating the structural performance of steel fiber-reinforced concrete by developing a freeze-thaw constitutive model, thereby providing a theoretical basis and analytical method for the design and durability assessment of tunnel linings in cold regions. Full article

Novel porous geopolymer (IGP&SS), possessing mesoporous structure and a compressive strength of 9.40 MPa, was synthesized through alkali activation of double solid wastes such as iron tailings and steel slag. To overcome the high activation energy barrier of oxidants for refractory pollutant treatment, the IGP&SS was designed to efficiently activate peroxymonosulfate (PMS) under visible-light irradiation, generating reactive radicals for the rapid degradation of methylene blue (MB). The system achieved nearly complete removal within 30 min. To enhance MB removal, the effects of key factors including IGP&SS dosage, PMS dosage, initial MB concentration, temperature, and pH on the degradation process were systematically investigated. Quenching experiments revealed that several reactive oxygen species contributed to MB degradation, with the order of contribution being •OH > ¹O₂ > SO₄•⁻ > •O₂⁻. Mechanistic studies indicated that the efficient MB degradation was primarily attributed to the flexible Fe(II)/Fe(III) redox cycling in IGP&SS, which accelerated PMS activation and radical generation. X-ray photoelectron spectroscopy (XPS) analysis of the post-reaction catalyst confirmed its structural robustness, revealing a characteristic binding energy shift in the O 1s peak to 530.8 eV and a quantitative redistribution of iron species (Fe(III) content increasing from 40.4% to 57.0%). Given its outstanding performance, demonstrated stability, and eco-friendly preparation, IGP&SS holds great promise for PMS-based advanced oxidation processes in dye wastewater treatment, offering a sustainable approach for high-value utilization of iron tailings and steel slag while alleviating resource scarcity. Full article

This study aimed to develop sustainable supersulfated cement (SSC) comprising ferronickel slag (FNS), desulfurized gypsum, carbide slag, and a small amount of Portland cement (PC). A two-stage optimization approach considering mechanical strength, volume stability, durability, and sustainability was employed to screen the mixture proportions of low-clinker FNS-based SSC. Orthogonal experiments were firstly conducted to investigate the effects of PC, carbide slag, and desulfurized gypsum contents on the mechanical properties of SSC mortar. Range analysis revealed that carbide slag exerted the most significant impact on early-age mechanical strength, while desulfurized gypsum plays an increasingly important role in late-age strength development. Subsequently, a single-factor test was applied to determine the optimal carbide slag content in FNS-based SSC. The results demonstrated that with the incorporation of 4% carbide slag, the SSC mortar achieved the 3-day and 28-day compressive strengths of 15.88 and 42.5 MPa, with relatively low volumetric expansion. The screened mixture proportions also satisfied the requirements for strength class 42.5 SSC according to both Chinese and British standards. A life cycle assessment further indicated that its carbon emission was approximately 46.91% lower than that of conventional PC. This research provided key technical and data support for the synergistic utilization of multi-source solid wastes in producing low-carbon cementless binder. Full article

Premature deterioration of reinforced concrete is driven largely by moisture and chloride ingress, which accelerate steel corrosion and shorten service life. This study investigates a dual strategy to enhance durability while supporting circular-economy goals: (i) incorporating coal-fired biomass ash (CBA) as a fine-aggregate replacement (0%, 20%, and 50%) and (ii) applying bio-inspired surface treatments to reduce transport pathways. To capture variability in CBA performance across different environmental and material contexts, two concrete systems—produced in India and the UK—were evaluated, each subjected to a distinct coating approach: a bacterial self-healing treatment or a cinnamaldehyde (CNM) organic barrier. Mechanical, transport, and multi-scale characterization was performed, including compressive strength, capillary absorption, chloride migration (NT Build 492), SEM/EDS, XRF, and XRD. The 20% CBA mixes maintained or slightly improved strength, while higher CBA contents increased porosity but reduced chloride transport in the UK mix. The bacterial coating reduced long-term water absorption by over 80% through CaCO₃ mineralization, offering strong moisture resistance. The CNM coating decreased chloride migration by up to 68% via hydrophobic and ionic-blocking effects. Overall, moderate CBA with self-healing treatment enhances moisture control, whereas higher CBA with CNM provides effective chloride protection, extending the service life of CBA-based concrete. Full article

Chloride-induced deterioration is a major threat to the durability of marine concrete structures, especially in tidal and submerged zones. This study simulated these environments by immersing C45 concrete specimens in NaCl solutions (5%, 10%, 15%) under both constant immersion and wet–dry cycles. Compressive strength tests, low-field NMR for pore structure, chloride ion profiling, and SEM-EDS analyses were conducted. A modified chloride diffusion model was developed based on Fick’s second law, incorporating time- and concentration-dependent parameters. The results showed that higher NaCl concentrations and tidal zone exposure significantly accelerated concrete degradation. In the tidal zone, wet–dry cycles led to larger macropore formation, higher chloride penetration, and more severe microstructural damage compared to the submerged zone. Compressive strength initially increased and then declined in high-salinity environments, with strength losses reaching up to 25% under 15% NaCl after 120 days. NMR data confirmed the transformation of micropores and mesopores into macropores, especially in the tidal zone. SEM-EDS analysis revealed decalcification, gypsum formation, and Friedel’s salt accumulation on eroded surfaces. It was determined that chloride ion diffusion behavior in concrete is significantly influenced by the chloride content and diffusion concentration, as well as the exposure zone. The developed model indicates that depth increased over time and with concentration. The proposed diffusion model achieved high fitting accuracy (R² > 0.97), effectively capturing the effects of erosion age and salt; this makes it a reliable tool for predicting chloride ion ingress in marine concrete, and for supporting service life evaluation and durability design. Full article

The complex coupling relationships among the thermal, mechanical, and electrical physical parameters of TiZrHf—based medium—entropy alloys represent a key factor restricting their practical applications under complex extreme environments. In this study, the thermo—mechanical—electrical coupling characteristics of TiZrHf and TiZrHfCu_0.8 medium—entropy alloys were systematically investigated using a self—developed experimental platform. The results demonstrate that TiZrHf and TiZrHfCu_0.8 alloys exhibit elastoplastic and superelastic—plastic compressive deformation behaviors, respectively, with both elastic modulus and ultimate strength decreasing monotonically with increasing temperature T. Electrical property measurements reveal that the electrical resistivities ρ of the two alloys range from 3 to 35 × 10⁻⁶ Ω·m. Notably, TiZrHfCu_0.8 possesses a lower resistivity that is independent of the test frequency f. Moreover, ρ increases with T but decreases with applied stress σ. At a frequency of 1 kHz, the real part of the relative dielectric constants ε_r of the alloys varies between −3.5 × 10⁸ and −0.5 × 10⁸ and increases with rising f, whereas the effects of T and σ on ε_r are opposite to those on ρ. Thermal property tests indicate that the thermal conductivities α of both alloys increase with T and eventually stabilize at 28.23 and 53.51 W·m⁻¹·K⁻¹, respectively, while the thermoelectric coefficients S are positively correlated with the heating rate, on the basis of comprehensive data analysis, multi—physical parameter (T, σ) dependent mathematical expressions for elastic modulus, strength, ρ, ε_r, α, and S were established, respectively. This work provides valuable insights into the material response mechanisms under complex service conditions, which are conducive to the optimization of alloy composition design and the promotion of their practical engineering applications. Full article

Red mud, a major solid waste from the alumina industry, suffers from an extremely low utilization rate due to its high alkalinity, complex chemistry, and particularly low cementitious activity, which drives the need for novel activation strategies. This study presents a new method for red mud activation through electrochemical treatment, which simultaneously enables iron recovery as a valuable by-product. The electrochemical activation was systematically investigated by performing experiments in alkaline, neutral, and acidic electrolytes. The alkaline system showed a pronounced enhancing effect on the electrochemical process. Under alkaline conditions, the average Faradaic efficiency exceeded 80%. The electrochemical treatment modified the microstructure of red mud particles and transformed iron oxides into magnetic species, which could be effectively separated via magnetic separation. More importantly, this activation process significantly enhanced the cementitious activity of the treated red mud by removing iron oxide that encapsulates reactive aluminosilicate phases and increasing surface reactivity. When used as a supplementary cementitious material with ordinary Portland cement and gypsum, the electrochemically activated red mud demonstrated remarkably improved mechanical properties, with 28-day compressive strength reaching up to 69 MPa. Characterization analysis revealed that the electrochemical activation promoted the formation of key hydration products, including C-S-H gel (formed through both OPC hydration and pozzolanic reactions between activated red mud and portlandite), ettringite, and portlandite. This work provides a green and low-carbon pathway for the stepwise utilization of red mud through activation and resource recovery. Full article

Hydrogel-based products are used in many areas of biomedicine and healthcare. Recently, the incorporation of cellulose nanocrystals (CNC), a renewable and functional nanomaterial, into hydrogels has enhanced their functionality, particularly by imparting mechanical strength and structural integrity. This scoping review aims to appraise the types of biomedical models and assays that have been utilised to investigate the effects of CNC incorporation into hydrogels in tissue engineering, wound healing, medical implantation and drug delivery applications, and reports on the rationale for including these models and assays. A structured literature search was undertaken in major scientific databases (PubMed Central, PubMed, BioMed Central, ScienceDirect, Wiley and EBSCOhost), focusing on identifying primary research published between 2016 and 2024. From this process, fifteen studies providing biomedical analyses met the inclusion criteria. Most of these investigations employed in vitro cell-line models (n = 12), with a smaller number utilising in vivo experimental systems (n = 5). Across the included studies, CNC incorporation typically yielded measurable performance gains: reported compressive or storage modulus improvements of 20–40% over hydrogel-only controls, consistently high cell viability (>85%) across multiple human and murine cell types for up to 21 days, and sustained drug release profiles (days–weeks) in stent and antitumour contexts. Where quantified, functional outcomes in vivo included preserved graft volume (autologous fat grafts) and reduced intimal hyperplasia signals in vascular graft models. Critical gaps included heterogeneous CNC sources and surface chemistries, inconsistent reporting of CNC concentration and hydrogel formulation parameters, the limited duration and scope of biocompatibility testing, and minimal alignment with standard evaluation protocols, constraining reproducibility and cross-study comparability. To date, there are no human clinical trials of CNC-hydrogels. Translational readiness will require standardised ISO-compliant biocompatibility evaluations. Large-animal studies under relevant mechanical and physiological conditions, and rigorous long-term degradation and immunogenicity assessments to de-risk progression to human trials. We recommend standardised CNC sources and surface functionalisation reporting, concentration (wt%) ranges, hydrogel rheological characterisation (G′, G″, swelling), and consistent biological endpoints (viability, differentiation, inflammation panels) to enable robust meta-analyses and translational benchmarking. Distinct from prior nanocellulose reviews that emphasise material synthesis and properties, this analysis centres on the biomedical models and assays applied to CNC-incorporated hydrogels, identifying the methodological convergence and divergence that directly impact translational pathways. Full article

The low activity and expansion risk of steel slag limit its large-scale utilization in cementitious systems. This study developed an alkali-sulfate synergistic activation method to prepare binder with steel slag content exceeding 50 wt%. The effects of alkali activator dosage, modulus, steel slag and flue gas desulfurization gypsum content on the mechanical properties and workability were systematically investigated. With a mix of 60% steel slag, 30% fly ash, 10% desulfurization gypsum and activated by additional 20% alkali activator with modulus 1.0, the 28-day compressive strength reached 12.85 MPa, along with excellent volume stability. Microstructural characterization revealed that the main hydration products are C-A-S-H and ettringite, which jointly form a dense microstructure. When used to solidify lead–zinc tailings for backfill, the binder yielded satisfactory strength and effectively immobilized heavy metals (Pb, As, Cd, Zn), with leaching concentrations meeting environmental standards and immobilization efficiencies > 80%. Heavy metals were primarily immobilized through physical encapsulation, ion exchange, and co-precipitation. This study elucidates the hydration and mechanisms of high-content steel slag systems under alkali-sulfate synergistic activation, providing a sustainable technical framework for large-scale utilization of steel slag and tailings management. Full article