Search Results (34,590)

The research undertaken examines the impact of recycled tire steel fiber (RTSF) and waste aluminum (WAL) on the mechanical properties and freeze–thaw durability of sustainable fiber-reinforced concrete (FRC). RTSF (0.5%, 1.25%, and 2%) and WAL (10%) were added on their own and as hybrids. Findings revealed that 1.25% RTSF was the optimum content to use, as it enhanced compressive strength by 12.8% with high durability. Tensile and flexural strengths also increased for higher fiber contents with the help of good crack bridging and increased post-crack ductility; maximal gains of 52.6% and 11.8% were obtained at 2% RTSF. In contrast, the increase in porosity and the decrease in strength were demonstrated with WAL, whereas hybrid mixes delivered a balanced performance. Microstructural analysis ensured that there was an enhanced bonding between the fibers and the matrix, coupled with a refinement in the pore at the optimal fiber content. This study establishes the structural viability, durability improvement, and sustainability prospect of hybrid recycled material concrete as a construction material with eco-efficient and resilient applications. Full article

This study investigates how historical variability in construction materials influences the seismic fragility of reinforced concrete (RC) buildings in Bucharest. Mechanical properties of reinforcing steels (OB37, TOR47, and PC52) and concretes used between 1950 and 2000 are statistically characterized using archival records and experimental data. The analysis highlights significant discrepancies between prescribed and in situ concrete strengths, as well as substantial differences in ductility, overstrength, and strength variability among historical steel types. To evaluate structural implications, a representative 11-storey pre-1970 RC building is modeled using nonlinear static and incremental dynamic analysis. The results show markedly lower capacity and higher fragility in the transversal direction. Time-dependent deterioration is examined by incorporating carbonation-induced reinforcement corrosion using FIB-based formulations. Even moderate corrosion leads to measurable reductions in stiffness, ductility, and lateral capacity, producing higher fragility across all considered damage states. Seismic loss estimations further demonstrate an increase in expected annual losses for both principal directions when corrosion is considered. The findings underscore the need for era-specific material models and deterioration mechanisms to achieve accurate seismic vulnerability assessments of Bucharest’s aging RC building stock. Full article

To enhance the early-age properties of steel slag cement mortar and promote the resource utilization of metallurgical solid waste, in this study, nano-SiO₂ (KH-NS) was modified using a KH550 silane coupling agent. The hydration kinetics and microstructure evolution were systematically analyzed by means of a macroscopic performance test (setting time and compressive strength) and multi-scale microscopic characterization (characterized by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, X-ray Diffraction, Thermogravimetry-Differential Thermal Analysis, and isothermal calorimetry). The influence mechanism of its content on the early performance of the steel slag cement system was systematically studied. Research findings indicate that at a given dosage, increasing the proportion of KH-NS results in a shorter setting time for steel slag mortar. When the KH-NS dosage reaches 1.5%, the initial and final setting times of steel slag mortar decrease by 24.21% and 21.20%, respectively. The addition of KH-NS effectively enhances the compressive strength of mortar, with a particularly pronounced effect on early strength prior to 14 h of curing. At a KH-NS dosage of 1.5%, the onset of the accelerated phase of hydration heat release in steel slag cement mortar is advanced by 2.5 h. Mechanistic studies indicate that KH-NS accelerates cement hydration by promoting C₃S dissolution and C-S-H gel nucleation through interactions between surface silanol groups (Si-OH) and amino groups (-NH₂). Furthermore, KH-NS refines the pore structure via a micro-aggregate filling effect, reducing the number of harmful pores and improving the pore size distribution. KH-NS continuously consumes Ca(OH)₂ through pozzolanic reactions to generate C-S-H, with its reactivity increasing with higher dosage. Research confirms that KH-NS significantly enhances the early strength and density of steel slag mortar, providing both theoretical justification and technical support for developing low-carbon building materials based on solid waste with high dosage. Full article

The corrosion of prestressed tendons in concrete structures remains a major durability concern, especially for post-tensioned members exposed to aggressive environments. High-strength aluminum alloy (AA) bars exhibit favorable characteristics such as corrosion resistance, low density, and high ductility and may therefore provide an alternative or supplementary prestressing material in durability-oriented structural design. In this study, a bonded post-tensioned T-shaped concrete beam with hybrid prestressing combining prestressed steel (PS) strands and 7075 AA bars was investigated. A refined finite element model was developed by considering the bond-slip relationship between the AA tendons and grout inside corrugated tubes. The flexural behavior of the beam was analyzed through a combination of finite element simulation and sectional theoretical analysis. In addition, a fatigue-life assessment framework was established based on vehicle fatigue loads and material fatigue constitutive models, and the fatigue performance of the proposed hybrid beams was compared with that of conventional prestressed concrete beams. The theoretical predictions agreed reasonably well with the numerical results. Results indicated that partial replacement of PS strands with corrosion-resistant AA bars could alter the governing fatigue failure mode and improve the fatigue durability of prestressed beams under corrosive conditions. These findings highlight the potential of hybrid AA–PS prestressing as a durability-oriented strategy for concrete beams in corrosive environments. Full article

The growing global demand for critical raw materials (CRMs) essential to renewable energy, electromobility, and digital technologies has accelerated the need for advanced exploration methods capable of operating in increasingly challenging geological environments. Traditional drilling systems, designed primarily for shallow mineral and hydrocarbon exploration, face limitations in heterogeneous and consolidated formations where rock heterogeneity, variable mechanical strength, and borehole instability restrict operational efficiency. This review bridges geological science and robotic engineering by analyzing the evolution of next-generation autonomous drilling technologies integrating sensor systems, artificial intelligence (AI), and real-time geotechnical feedback. The current work explores how robotic drilling systems can autonomously adapt to variable lithologies, optimize penetration rates, and ensure borehole stability through intelligent sensing and control. The paper reviews the geological, geomechanical and ore deposit characteristics of CRMs, discusses state-of-the-art drilling optimization strategies, and highlights advances in measurement while drilling (MWD), logging while drilling (LWD), and geochemical analysis techniques. It also suggests a list of sensor techniques for possible future integration in autonomous subsurface robotic systems. It concludes by emphasizing the need for integration between subsurface geological modeling and intelligent drilling robotics as a pathway toward sustainable and efficient CRM exploration. Full article

This study investigates the dual mechanisms by which SiO₂ deteriorates magnesium phosphate cement (MPC) performance. MgO-SiO₂ clinkers were prepared using lightly calcined magnesia (MgO) with SiO₂ additions ranging from 1% to 9%, followed by calcination at temperatures between 1100 °C and 1500 °C. Through XRD–Rietveld refinement, workability, compressive strength, and hydration heat analyses, the damaging effects of SiO₂ were systematically evaluated. Results reveal that SiO₂ degrades MPC through two concurrent mechanisms: chemical consumption and physical deactivation of reactive MgO. Chemically, SiO₂ reacts with MgO during calcination to form inert forsterite (Mg₂SiO₄), irreversibly reducing reactive MgO content. Physically, SiO₂ and its reaction products lower the crystallinity and reactivity of remaining MgO while diluting reactive components. A calcination temperature of 1200 °C was optimal, yielding the highest compressive strength (3 d strength > 30 MPa). Increasing SiO₂ dosage monotonically reduced strength; at 1200 °C, 9% SiO₂ reduced 3 d strength by ~40% compared to 1%. Hydration heat analysis showed that both heat flow rate and cumulative heat release increased with SiO₂ content due to enhanced heterogeneous nucleation from Mg₂SiO₄. Critically, this increased heat output did not translate into higher strength, indicating that microstructural quality—not reaction extent—governs mechanical performance. Rietveld quantification confirmed that Mg₂SiO₄ formation increased linearly with SiO₂ dosage and temperature (reaching 72.24% at 1500 °C with 9% SiO₂), providing the material basis for dual damage. This work offers mechanistic insights and experimental support for utilizing low-grade magnesite and optimizing MPC performance. Full article

This study investigated the failure mechanism and load-bearing capacity of ultra-high-performance concrete (UHPC) columns confined with high-strength spiral stirrups under axial compression. Based on tests of 75 specimens, a structural stability analysis method was employed to convert multi-point strain measurements into the normalized generalized strain energy density (E_j,norm). The mutation point (Point U) on the E_j,norm-F_j curve, identified via the Mann–Kendall criterion, was proposed as a novel indicator for structural instability and the practical failure load. Parametric analysis showed that increasing the UHPC compressive strength from 100 MPa to 180 MPa raised the failure load by 63%, while increasing the stirrup volumetric ratio from 0.9% to 2.0% yields a further 7.5% increase in the failure load. In contrast, the yield strength of stirrups exerts a negligible influence on the failure load, as the stirrups do not reach their yield strength at the failure load of the concrete columns. A new predictive model for the failure load was developed, which exhibited excellent agreement with test results (mean ratio = 1.000, standard deviation = 0.046, errors within ±13%). The proposed method provided a reliable and stable approach for evaluating the failure load-bearing capacity of confined UHPC columns. The validated predictive model enabled engineers to determine the failure load of confined UHPC columns through simple calculation rather than expensive experimental testing, reducing project costs by 5–10% through optimized material selection and accelerating design timelines by weeks, thereby making UHPC columns more economically competitive for mainstream infrastructure applications. Full article

Lodging is a major constraint to rice productivity and grain quality. The mechanical strength of basal internodes, particularly bending resistance (BDR), is a critical determinant of lodging resistance. In this study, we evaluated the BDR of the third and fourth basal internodes (BDR3 and BDR4) in a diverse panel of 340 rice accessions. A genome-wide association study (GWAS) identified three QTLs significantly associated with BDR3, which were defined and designated as qBDR1, qBDR4, and qBDR5. Further analysis revealed that OsWRKY102 on qBDR1 was identified as a key candidate gene. Haplotype analysis revealed distinct allelic variations between subspecies, with the elite haplotypes (Hap.1 and Hap.4) contributing to superior lodging resistance, while Hap.2 was predominantly found in lodging-susceptible Japonica accessions. CRISPR/Cas9-mediated knockout of OsWRKY102 in the ZH11 background resulted in a significant reduction of more than 50% in both BDR3 and BDR4 compared to the wild type. Detailed phenotypic characterization of the oswrky102 mutants revealed a substantial decrease in cellulose content and culm diameter, accompanied by an increase in culm wall thickness. These findings demonstrate that OsWRKY102 maintains culm mechanical strength by promoting radial expansion and cellulose accumulation. Biomechanical analysis further suggests that culm diameter and cellulose content are more critical for bending strength than wall thickness. Our results elucidate the regulatory role of OsWRKY102 in coordinating culm morphology and cell wall composition, providing a valuable genetic target for molecular breeding of high-yielding, lodging-resistant rice varieties. Full article

Dental tissue regeneration, particularly alveolar bone and gingival repair, remains a major challenge in regenerative medicine. 3D bioprinting offers patient-specific and anatomically precise constructs, representing an advanced alternative to conventional grafting. In this study, nanohydroxyapatite (nHA), chitosan (CS), and collagen (CoL) were combined to fabricate and characterize 3D bioprinted dental grafts. SEM revealed a highly porous, interconnected architecture favorable for cell infiltration and nutrient exchange. EDS confirmed Ca/P ratios of 2.06 for nHA/CoL and 1.83 for nHA/CS/CoL, both of which are above the stoichiometric 1.67, indicating the presence of additional mineral phases and ion substitutions. FTIR and XRD verified characteristic functional groups and crystalline phases, including B-type HA with carbonate substitution. Mechanical testing showed that pure nHA exhibited the lowest compressive strength, whereas CoL incorporation improved stiffness. The nHA/CS/CoL composite achieved the highest compressive strength, elastic modulus, and toughness, demonstrating superior mechanical resilience. DSC analysis indicated endothermic peaks at 106.49 °C and 351.91 °C, with enthalpy values (264.91 J/g and 15.09 J/g) surpassing those of nHA alone. TGA revealed ~28.8% weight loss across three degradation stages, confirming enhanced thermal stability. In vitro cytocompatibility testing using L929 fibroblasts validated the biocompatibility of the composites. Collectively, the synergy between bioceramics and biopolymers markedly improved both mechanical and thermal performance. These findings position the nHA/CS/CoL scaffold as a promising candidate for clinical applications in dental tissue regeneration. Unlike conventional grafting materials, this study introduces a synergistically optimized nHA/CS/CoL bio-ink formulation specifically designed for extrusion-based 3D bioprinting of patient-specific dental constructs. The core innovation lies in the precise integration of nHA within a dual-polymer matrix (CS/CoL), which bridges the gap between mechanical resilience and biological signaling, achieving a compressive strength that mimics native alveolar bone while maintaining high cytocompatibility. Full article

Glass fiber-reinforced epoxy composites were modified with carbon nanotubes (CNTs), Al₂O₃, and TiO₂ nanoparticles to comparatively evaluate their influence on tensile, flexural, and low-velocity impact performance within an integrated experimental–numerical framework. Nanoparticles were incorporated at controlled weight fractions to identify dispersion-controlled reinforcement regimes and the onset of heterogeneity-driven mechanical transitions. Among all formulations, 0.5 wt% CNTs provided the most pronounced static mechanical enhancement, increasing tensile strength to 419.50 MPa (≈21% improvement over the reference GF laminate) and flexural strength to 230.23 MPa (≈26% increase). In contrast, impact performance exhibited a non-monotonic evolution; the highest absorbed energy (9.64 J) was observed at 2 wt% CNTs, indicating that dynamic energy dissipation mechanisms do not necessarily scale proportionally with static strength gains. Oxide-filled systems demonstrated stiffness-dominated behavior, where increasing filler content amplified elastic mismatch and progressively reduced strength despite modulus enhancement. Finite element simulations conducted in ANSYS LS-DYNA (MAT_022) reproduced global stiffness trends within the dispersion-controlled regime. Tensile strength predictions agreed within 0–9% at optimal CNT loading, whereas larger deviations (up to ~33%) emerged under bending-dominated loading in oxide-rich systems, reflecting amplified sensitivity to microstructural heterogeneity. The coupled evolution of stiffness–strength decoupling (SSDI) and FEM deviation (η) enabled identification of a Composite Heterogeneity Threshold (CHT), defined as the nanoparticle concentration beyond which stiffness enhancement no longer translates into proportional strength or toughness improvement. Beyond this threshold, dispersion-induced heterogeneity not only reduces mechanical efficiency but also marks the boundary of homogenized continuum model adequacy across static and dynamic loading conditions. Full article

To mitigate the issue of brittleness and cracking in epoxy resin (EP) anti-skid systems, this study investigates four key aspects tailored to application scenarios: toughening, low shrinkage, strong adhesion, and rapid curing at ambient temperature. 1,4-Butanediol diglycidyl ether (BDDE) was used to extend the chain of triethylenetetramine (TETA), followed by a Mannich reaction with formaldehyde (F) and cardanol to prepare a flexible aliphatic amine Mannich base curing agent containing flexible segments (Curing Agent B). The influence of composition ratios on the mechanical properties of the cured product was studied. The curing performance of the epoxy system under various temperature conditions and its adhesion to asphalt substrates were characterized. The thermal shrinkage behavior of the epoxy system under temperature-variable environments was also investigated. The results indicated that the elongation at break of the epoxy curing system, after chain extension and toughening, increased from 28.7% to 40.4%, representing a 28.9% increase. When n (Cardanol):n (TETA):n (F):n (BDDE) = 1:1.4:0.8:0.7 (molar ratio of reactants), m (EP):m (Curing Agent B) = 1:1 (mass ratio), and epoxy-terminated polyurethane (EPU) prepolymer constituted 10% of the epoxy resin mass; the epoxy curing system exhibited an elongation at break of 44.3%, a tensile strength of 7.0 MPa, a bond strength of 6.9 MPa, and an impact toughness of 1.77 J/cm². Furthermore, it exhibited rapid curing at a low temperature (0~5 °C) and at room temperature (25 °C). Additionally, when bisphenol F epoxy resin was used, the system demonstrated optimal thermal expansion properties. Full article

To investigate the deterioration law of the mechanical properties of PVA-fiber-reinforced rubber concrete under the combined action of high-temperature and salt erosion, physical index tests, dynamic mechanical property experiments, and microstructural morphology observations were carried out on specimens subjected to different temperatures (ambient temperature, 100 °C, 300 °C) and various solution attacks (water, 5% NaCl, 5% Na₂SO₄, and 5% NaCl + 5% Na₂SO₄ mixture). The results show that, after exposure to 300 °C, the PVA fibers melt and the rubber pyrolyzes, since this temperature exceeds their melting points. A residual pore network is formed inside the matrix, and the damage degree of ultrasonic pulse velocity is about 2.3 times that of the 100 °C group. Although salt solution and its crystallization products can physically fill the pores and cause a partial recovery of pulse velocity, this change is mainly due to the alteration of the pore medium and does not represent a substantial restoration of the microstructure. The effects of different salt solutions on dynamic mechanical properties vary significantly: Sulfate erosion improves the dynamic performance significantly at ambient temperature by forming gypsum and ettringite to fill pores, but this strengthening effect disappears after 300 °C. Sodium chloride attack generates Friedel’s salt and consumes C₃A, leading to general strength deterioration. In composite salt erosion, the competitive and synergistic effects of Cl⁻ and SO₄²⁻ destabilize erosion products and weaken interfacial bonding, resulting in consistent decreases in dynamic compressive strength and elastic modulus under all temperatures and impact pressures. The strength reduction reaches 66.2% after 300 °C. Microscopic analysis confirms that composite salt erosion leads to the dissolution of ettringite and loose structure, which verifies the synergistic deterioration law of macroscopic properties. This study systematically reveals the damage evolution mechanism of PVA-fiber-reinforced rubber concrete under the coupled action of high-temperature and salt erosion, and provides a theoretical basis for the dynamic bearing capacity evaluation and durability design of concrete structures in such coupled environments. Full article

Background: Sarcopenia is an age-related syndrome characterized by progressive loss of skeletal muscle mass and strength, representing a major contributor to disability and increased mortality in older adults. Current diagnostic frameworks increasingly emphasize muscle quality alongside quantity, creating a clinical need for bedside tools that can objectively assess muscle mechanical properties. Shear-wave elastography (SWE), an ultrasound-based technique that quantifies muscle stiffness, has emerged as a promising biomechanical biomarker of muscle quality. Aim: This narrative review evaluates the evidence supporting SWE for assessing muscle quality and its association with aging, sarcopenia, and functional outcomes. Methods: We searched PubMed, Embase, and Web of Science (from January 2010 to December 2025) using terms related to elastography and sarcopenia. Based on relevance and methodological quality, approximately 50 key studies were selected for in-depth discussion and synthesis. Synthesis: Observational studies consistently demonstrate that SWE detects age-related reductions in muscle stiffness, which correlate significantly with declines in muscle strength and physical performance. Unlike conventional B-mode ultrasound, which primarily provides morphological parameters, SWE directly reflects intrinsic tissue mechanics, enabling more direct assessment of muscle quality. In high-risk populations such as patients with type 2 diabetes, reduced muscle stiffness is also associated with sarcopenia and poor functional outcomes. However, reported stiffness trends with aging remain heterogeneous, and validated diagnostic thresholds are lacking. Stiffness changes vary by muscle group, acquisition protocol, and loading state. Clinical implementation is currently limited by inter-device variability, operator dependence, and sensitivity to muscle loading conditions. Conclusions: Current evidence suggests that SWE holds promise as an adjunctive research tool for assessing muscle quality and risk stratification, but it is not yet ready for standalone clinical diagnosis due to methodological heterogeneity, lack of validated cutoffs, and limited longitudinal data. Future large-scale, longitudinal, multicenter studies with standardized protocols are needed to establish its definitive diagnostic utility. Full article

To address the limitation of insufficient mechanical strength and short service life in biodegradable bamboo fiber mulch film (BFM) replacing plastic film in agriculture, this study applied a biochemical method to make bamboo fiber and used bacterial cellulose (BC) as a natural nanoscale reinforcing agent to fabricate high-performance bacterial cellulose bamboo fiber mulch film (BC-BFM). The physical and mechanical properties, chemical structure, seed germination and degradation behavior performance of BC-BFM were characterized. Results demonstrated the structural compactness and homogeneity of the BC-BFM were improved markedly with the increase in BC addition and BC formed a 3D nanofibrillar network that effectively bridged inter-fiber voids. The tensile, burst and tear indexes of BC-BFM all significantly rose with BC addition. Notably, compared to plastic film and BFM, BC-BFM exhibited a good effect on mung bean seed germination and the best growth speed was at 5% BC addition. Furthermore, the degradation test showed that the degradation rate of BC-BFM within 90 d was three times less than that of BFM and service life was similar to plastic film. This showed that it was a promising method to prepare biodegradable high-quality BFM through biochemical preparation of bamboo fiber and BC nanocellulose reinforcement. This method markedly enhanced the mechanical performance and durability of BC-BFM, providing a feasible technical path for the development of biodegradable high-performance green agricultural covering materials with long service life. Full article

This study investigated the enhancement mechanisms and optimal mix proportion of basalt fiber (BF) in concrete for ship lock galleries. It focused on improving crack resistance, freeze–thaw resistance, impermeability, and abrasion–erosion resistance under complex hydraulic environments. Single-factor tests first determined the reasonable parameter ranges, which were subsequently used in a three-factor, four-level orthogonal experiment to analyze the effects of the water-to-binder ratio, fiber content, and fiber length on concrete’s mechanical properties. Range analysis of the orthogonal experiment indicated that the water-to-binder ratio was the most dominant factor (R = 57.4), followed by fiber content. Based on this, further durability tests were conducted, including ring restraint cracking, impermeability, freeze–thaw resistance, and abrasion–erosion resistance. Multi-objective optimization was performed using full factorial experiments and a comprehensive performance evaluation system. The final optimal mix proportion was determined as: a water-to-binder ratio of 0.35, a fiber content of 0.2%, and a fiber length of 12 mm. With this mix, the concrete’s ring cracking time was extended by 69.9%, the relative dynamic elastic modulus retention reached 73.0% after 100 freeze–thaw cycles, the relative permeability coefficient was 1.04 × 10⁻⁶ cm/h, and the abrasion–erosion resistance strength increased to 7.05 h·m²/kg, which achieved an optimal synergy among the mechanical properties, key durability indicators, and their workability. Mechanism analysis revealed that BF formed a three-dimensional, randomly distributed fiber network that comprehensively enhanced concrete performance through multi-scale mechanisms, including bridging, pore refinement, and energy dissipation. This research has provided systematic experimental evidence and mix proportion support for the durability design and engineering application of BF concrete in ship lock galleries. Full article