Search Results (9,525)

Staggered-floor steel-reinforced concrete beam–column joints are extensively applied in turbine buildings of nuclear power plants to meet the requirements of spatial layout and pipeline arrangement. Such joints feature distinct geometric discontinuity and suffer additional torsion effects as well as asymmetric stress distribution when the middle column is lost, which greatly impairs the structural progressive collapse resistance. In this study, three 1/5-scale joint specimens, consisting of two staggered-floor steel-reinforced concrete joints and one reinforced concrete joint, were tested under vertical monotonic static loading. The failure pattern, deformation property, torsional performance, strain development and load-bearing mechanism were comprehensively analyzed. Finite element models considering the coupling effect of torsion, bending and shear were established and validated via ABAQUS. The test results show that the peak load-bearing capacities of the SRC-1, SRC-2, and RC specimens were 148.2 kN, 149.7 kN, and 69.3 kN, respectively. Compared with the RC specimen, the peak load-bearing capacity of the SRC specimens more than doubled, indicating that the embedded H-section steel can significantly improve the load-bearing capacity of staggered beam–column joints. However, when the staggered height distance was increased from 140 mm to 280 mm, the ultimate collapse displacement of the specimens decreased from 340 mm to 310 mm, indicating a reduction in deformation capacity. The finite element model reasonably reproduced the specimens’ primary load–displacement response and damage characteristics, with a peak load error of 8.93% for SRC-1. Finally, corresponding design recommendations are put forward for staggered-floor steel-reinforced concrete joints in nuclear power plant structures. Full article

Aging and deterioration of urban underground drainage pipelines frequently trigger road collapses, urban waterlogging and groundwater contamination, posing critical challenges to the operation, maintenance and disaster prevention of urban underground infrastructure. Conventional rehabilitation solutions, including cement-based linings and traditional polymer liners, suffer from inherent limitations such as reduced effective flow cross-sections caused by excessive lining thickness, unsatisfactory corrosion resistance and durability, and high construction disturbance. In this study, a modified polyurea (MPU) material was applied to the trenchless rehabilitation of drainage pipelines via spray-applied pipe lining technology. The mechanical properties and interfacial bonding performance of MPU were systematically characterized at the material scale; full-scale external pressure tests were conducted to investigate the effects of 3–8 mm thick MPU linings on the bearing capacity and failure characteristics of structurally damaged concrete pipes; and the anti-seepage repair performance for local perforation defects was evaluated through void-crossing testing. The results demonstrate that MPU lining can meet the engineering performance requirements for pipeline rehabilitation when applied with matched interfacial primer following standard construction procedures. Even the baseline bond strength tested without primer remains sufficient to ensure stable cooperative load bearing between the lining and the host concrete pipe. The 3–8 mm thick linings increase the cracking load of damaged pipes by 61.7–145.7% and the ultimate load by up to 162.2%, while transforming the failure mode from brittle fracture to ductile failure. For local perforation repair, the 3 mm thick MPU lining achieves a critical hydrostatic failure pressure of 1.23 MPa, maintaining favorable structural integrity and interfacial bonding stability under the test conditions. With a well-balanced combination of thin lining thickness, rapid curing and high structural strengthening efficiency, as well as favorable inherent corrosion resistance, the MPU lining provides novel material alternatives and fundamental experimental evidence for the green trenchless rehabilitation of aged underground pipelines and offers technical support for the safe operation and maintenance of urban underground infrastructure. Full article

Decarbonising the building sector requires addressing both embodied carbon in materials and operational energy for indoor conditioning. This article critically reviews the potential of mycelium, hygromorphic wood and hemp as emerging natural materials for low-carbon construction, comparing them with conventional materials only within function-specific applications such as envelopes, insulation, non-load-bearing components and passive systems. Recent comparative literature shows that mycelium composites can reach thermal conductivities of 0.026–0.12 W/m·K and densities of 51–280 kg/m³; in wood–mycelium formulations, an average density of 167.5 kg/m³ and climate impact of 2.13 kg CO₂-eq/kg with a conventional electricity mix, reduced to 0.66 kg CO₂-eq/kg with renewable energy, have been reported. Hemp shows typical densities of 140–540 kg/m³, conductivities of 0.061–0.12 W/m·K, compressive strengths of 0.3–3.5 MPa and potentially negative climate performance of about −40 to −80 kg CO₂-eq/m³, compared with +300 to +400 kg CO₂-eq/m³ for conventional concrete. Hygromorphic wood is relevant not as insulation or a primary structural replacement, but as a passive actuation material for adaptive envelopes. Hemp is currently the most mature option, mycelium is promising for circular non-structural panels and insulation, and hygromorphic wood is an operational-modification strategy whose building-level energy benefits still require direct quantification. Cross-study comparisons should be interpreted as bounded ranges because composition, fabrication, testing and LCA (Life Cycle Assessment) system boundaries vary substantially across the literature. Full article

This review covers literature published up to June 2026. Detecting various water pollutants quickly and reliably remains a challenge. Boron-doped diamond (BDD) electrodes, particularly when fabricated as nanostructured thin films such as nanocones or nanowalls, offer a wide electrochemical window, low background current, and excellent chemical stability, making them promising tools for electrochemical sensing. However, unmodified BDD electrodes face an inherent trade-off among conductivity, active site density, and interfacial stability, a phenomenon termed herein the “sensitivity-selectivity-stability triangle bottleneck”, which severely limits practical performance. In this review, we demonstrate how multi-scale structural regulation can circumvent this bottleneck. Specifically, a triple strategy comprising boron doping, surface modification, and post-annealing treatment is proposed and evaluated. First, the effect of boron doping level on conductivity and active site density is discussed. Second, two common surface modification approaches are examined: carbon nanomaterials (which increase surface area and form conductive networks) and metal nanoparticles (which enhance catalytic activity and interfacial charge transfer). Third, post-annealing is highlighted as a key synergistic step that locks the modified layer and stabilizes the interface. Together, these three components form an integrated framework. To provide concrete guidance, the performance of each strategy is compared for representative water pollutants, including heavy metal ions, phenolic compounds, and emerging contaminants such as antibiotics and pesticides, with emphasis on sensitivity, selectivity, and stability. Representative detection limits achieved include 0.01 μg/L for Pb²⁺, 5 nM for acetaminophen, and 0.32 fM for PCB-77, demonstrating the effectiveness of the triple structural regulation strategy. Finally, in line with the theme of this Nanomaterials Special Issue on nanostructured thin films, current challenges in structural regulation are summarized, and future directions, including multi-parameter optimization, AI-assisted high-throughput screening, and real-world testing, are outlined. The goal is to offer practical structure-performance guidelines for designing BDD-based electrochemical sensors that are both high-performing and durable. Full article

Prefabricated steel–concrete composite bridge decks are widely used in the construction of long-span bridges due to their excellent mechanical performance and rapid construction speed. However, the joints in these decks are prone to tensile failure under negative bending moments, which limits the overall mechanical behavior of the structure. To improve the flexural–tensile performance of joints in prefabricated steel–concrete composite bridge decks under negative bending moments, a novel prefabricated steel grid–hybrid fiber concrete (PSG-HFC) composite bridge deck with closed-loop steel bar joints is proposed. Basic unit specimens of the composite bridge deck with closed-loop steel bar joints were designed and fabricated. Both physical and numerical experiments, including finite element modeling and model refinement, were conducted to clarify the mechanical response and failure mode of closed-loop steel bar joints under negative bending moments and to identify their rational structural parameters. Theoretical formula for calculating the flexural capacity of the closed-loop steel bar joints based on the strut-and-tie model theory was derived and verified. The results indicate that the failure mode of the novel PSG-HFC composite bridge deck under negative bending moments is typical plastic failure, with the ultimate failure mode being flexural–tensile failure at the joint section. The loading process includes elastic, elastoplastic, and plastic stages. From the perspectives of improving flexural capacity and fully utilizing high-strength materials, the rational structural parameters for the closed-loop steel bar joints are as follows: lap length of closed-loop steel bars of 230~250 mm, spacing of closed-loop steel bars of 130~150 mm, and bending radius of closed-loop steel bars of 70~90 mm. The maximum deviation between the theoretical formula results and the experimental and finite element numerical simulation results is 8.21%, indicating that the proposed formula is suitable for calculating and analyzing the flexural capacity of the joints in this novel composite bridge deck. This study reveals that the proposed closed-loop steel bar joint enables a ductile flexural–tensile failure mode in PSG-HFC composite deck under negative bending moments, and provides a validated theoretical formula for advancing the understanding of joint design in fiber-reinforced concrete structures. Full article

Significant amounts of smelting slag are generated during the production of steel, refined copper, and refined magnesium. These slags contain abundant valuable metallic elements, such as Fe, Cu, Zn, Co, and Mg, that have not been fully utilized in the past. This study proposes a method for modifying copper slag by mixing it with steel slag and magnesium slag, followed by roasting with additions of Fe₂O₃ and MgO. The samples were roasted at 1400 °C for 30 min, cooled to 1000 °C at 1.5 °C/min, and then water-quenched to room temperature. Phase transformations during modification were analyzed using FactSage 8.0, DSC–TG, and XRD. The effects of factors such as the content of Fe₂O₃ and MgO on the modification efficiency were investigated. The results indicate that, under the condition of maintaining a steel slag: copper slag: magnesium slag ratio of 37:37:26 and adjusting the basicity (CaO/SiO₂ ratio) with CaO to 2.0, the addition of Fe₂O₃ and MgO promotes the formation of spinel. However, excessively high contents of Fe₂O₃ and MgO lead to refinement of the spinel grains and reduce the iron grade of the concentrate. Within the investigated composition range, the samples with total Fe₂O₃ and MgO contents of 27.66 wt% and 7.56 wt%, respectively, showed the best magnetic separation performance among the tested compositions. Through magnetic separation, the concentrate has good economic and industrial application value in industries such as steelmaking and powder metallurgy, while the tailings can be utilized as raw materials for manufacturing ceramics, glass–ceramics, cement, and concrete. Full article

Aiming at the reduction in penetration depth caused by the deformation and fracture of conventional 90W-Ni-Fe rod penetrators during ultra-high-velocity penetration, a lightweight tungsten-based ceramic alloy was fabricated in this study. Ballistics tests were conducted to verify the penetration performance of the novel lightweight alloy against concrete targets, and the existing theoretical penetration model was modified accordingly. The results indicate that, within the impact velocity range of 1400~1750 m/s, the penetration depth of both rod penetrators presents an initial increasing and subsequent decreasing trend, with an extreme value near 1625 m/s and a dimensionless penetration depth X_p/L close to 4. Compared with the traditional 90W-Ni-Fe alloy, the lightweight tungsten-based ceramic alloy penetrator achieves a mass reduction of 5.7%. In the impact velocity range from 1408.0 m/s to 1743.5 m/s, its penetration depth increases by 6.22%~10.58%, and the improvement becomes more significant with the increase in impact velocity. For the modified theoretical model, the predicted ultimate penetration depth of the lightweight alloy rod penetrator increases by 8.85%, while the average mass loss rate and average erosion rate decrease by 12.09% and 17.65%, respectively. The error between theoretical calculations and experimental data is within 5%. Full article

Reinforced concrete beams with a fiber-reinforced polymer (FRP) plate bonded to their soffit, known as FRP-plated RC beams, commonly fail due to premature debonding of the FRP plate, limiting the utilization of the FRP strength. Inclined U-jacketing has been demonstrated to be effective as the end anchorage for mitigating debonding failures. The mechanism by which the inclined U-jacketing mitigates debonding failure remains unclear, and no design approach has been developed. Therefore, the present study has been conducted to investigate the mitigating effects of the key parameters of the inclined U-jacket through a series of four-point bending tests and systematic modeling. The test results indicate that both the inclination angle and the chamfer radius significantly affected the bond behavior of inclined U-jacket-to-concrete joints. Compared with the 45° configuration, reducing the inclination angle to 30° increased the peak load and peak displacement by 85.4% and 81.6%, respectively. In contrast, the effect of U-jacket side height became negligible once an effective bonded height had been reached, as increasing the side height from 75 mm to 120 mm changed the peak load by only 2.17%. In addition, a pre-peak parameter identification framework based on a power-function-type cohesive element constitutive relationship was proposed and validated. By analyzing the power-function parameters, namely the coefficient a and exponent b, the influences of U-jacket geometric variables on interfacial mechanical behavior were quantitatively characterized. The proposed approach provides experimentally verifiable parameterization to support the optimized design of inclined U-jacket anchorage systems. Full article

Reinforced concrete frame structures (RCFSs) subjected to strong seismic excitation may enter a metastable semi-ruin state before global collapse, characterized by severe local damage, degraded stability, and high secondary collapse risk. However, systematic experimental investigations and quantitative identification techniques for this critical transitional state are still lacking in existing seismic engineering literature, forming a notable research gap for post-earthquake safety evaluation. To investigate this critical transition, a Digital Image Correlation (DIC)-assisted shaking table test was conducted on a 1/25-scale RCFS specimen derived from an earthquake-damaged exterior-corridor teaching building, using the Wolong ground motion recorded during the 2008 Wenchuan earthquake as input. DIC was employed to track the full-field evolution of cracking, through-crack development, and concrete cover spalling under incremental seismic loading. Four local damage indices—crack line density (CLD), crack propagation rate (CPR), through-crack ratio (TCR), and concrete spalling ratio (CSR)—were extracted and evaluated with the inter-story drift ratio (IDR) to quantify local-to-global degradation. The results show that visible cracks initiated at PGA = 0.3 g, while accelerated crack propagation occurred at 0.7–0.8 g, with CPR peaks of 1187.5 and 1140 mm/g, respectively. At 0.5–1.0 g, the crack number increased from 13 to 26, total crack length reached 0.443 m, CLD increased to 3.9 × 10⁻⁴, and TCR reached 37.04%. At 1.1–1.5 g, crack development approached saturation, with total crack length of 0.552 m, maximum TCR of 63.6%, and CLD of 4.8 × 10⁻⁴. Under ultimate excitation of 1.6–1.8 g, the crack number stabilized at 33–34, TCR remained around 63%, cumulative spalling area reached 1026 mm², CSR reached 0.015, and the third-floor IDR approached the 1/50 elastoplastic limit. Severe through-cracking, reinforcement exposure, concrete spalling, and residual inclination indicated the onset of the semi-ruin state. The proposed multi-index framework provides quantitative support for semi-ruin-state identification and post-earthquake secondary collapse risk assessment of RCFSs. Full article

Aging of Styrene–butadiene–styrene (SBS)-modified asphalt accelerates the degradation of both the SBS polymer network and asphalt components, resulting in deterioration of the durability of asphalt concrete. This study investigates the use of zinc diethyldithiocarbamate (ZDC), a multifunctional antioxidant, in SBS-modified asphalt to improve its aging resistance. Physical property tests, dynamic rheological analysis, multiple stress creep recovery (MSCR) and Fourier transform infrared spectroscopy (FTIR) assays were conducted to evaluate the rheological and chemical properties of asphalt binders before and after thermo-oxidative and UV aging. The results indicate that the incorporation of ZDC improved the deformation resistance and elastic recovery of SBS-modified asphalt. After aging, the ZDC/SBS composite-modified asphalt exhibited lower performance change rate than conventional SBS-modified asphalt, indicating enhanced resistance to permanent deformation and aging-induced damage. FTIR analysis demonstrated that ZDC effectively inhibited the formation of oxygen-containing functional groups during aging, suggesting suppressed oxidative reactions within the asphalt binder. The 5% ZDC dosage reduces the carbonyl index of SBS-modified asphalt by 36.48% after thermo-oxidative aging, and by 21.89% after UV aging, showing a stronger chemical inhibition effect on thermo-oxidative reactions. From the perspective of rheological performance stability, ZDC lowers the variation amplitude of non-recoverable creep compliance by 35.32% before and after thermo-oxidative aging and 41.46% before and after UV aging, and delivers a more prominent mitigating effect on property fluctuations triggered by UV aging. This indicates that ZDC exerts differentiated anti-aging mechanisms on thermo-oxidative and UV aging, with considerable potential to improve the comprehensive aging resistance of polymer-modified asphalt binders. Full article

The inherent brittleness of cementitious materials presents a fundamental limitation for advanced structural applications. While bio-inspired Bouligand architectures have demonstrated remarkable damage tolerance in natural composites, their systematic translation to brittle inorganic binders via 3D concrete printing (3DCP)—and the development of high-fidelity meso-scale models to quantitatively map the resulting strength–toughness design space—remains underexplored. This study aims to decouple the intrinsic topological toughening potential of helicoidal Bouligand architectures from the stochastic defects inherent to additive manufacturing, through a meso-scale finite element (FE) framework. To physically validate the model, a nano-clay-assisted rheological strategy was utilized to enable the support-free fabrication of these helicoidal prototypes. Computationally, a meso-scale FE framework integrating the concrete damaged plasticity (CDP) model with three-dimensional cohesive zone elements was developed to explicitly resolve inter- and intra-layer interfacial crack kinematics. Coupled physical compression tests and numerical simulations indicate that the 15° Bouligand architecture achieves a computationally predicted 16.3-fold increase in volumetric energy absorption (experimentally: 13.7-fold) compared to the 0° unidirectional baseline, with a modest ~11% reduction in compressive strength (from ~33.0 MPa to ~29.5 MPa in simulations; ~12% experimentally). Furthermore, numerical parametric studies across the complete pitch-angle design space reveal an optimal topological window at 15–30°, wherein the competing effects of crack deflection and structural integrity are balanced. Imperfection sensitivity analysis demonstrates that the topological toughening mechanism is relatively robust: even with a 30% reduction in inter-filament bonding strength, the work of fracture remains 12.4 times higher than that of the 0° control. These findings suggest that spatial toolpath programming offers a viable, geometry-driven strategy for developing damage-tolerant cementitious composites, complementing conventional material-level reinforcement approaches. Full article

Whether corporate digital spending can produce sustainability-related outcomes is still not well understood. Much of the existing discussion treats digital transformation as a broad strategic process, but firms make sustainability decisions through more concrete resource allocations, including investment in information systems, data infrastructure, and IT-based management tools. This study therefore focuses on IT investment and examines its relationship with corporate environmental, social, and governance (ESG) performance. Based on panel data for Chinese A-share listed firms from 2009 to 2024, we estimate fixed-effects models and further test the roles of technological spillovers, market competition, and ownership structure. The evidence indicates that firms with higher IT investment tend to report better ESG performance. This association remains significant when lagged IT investment is used, suggesting that the result is not merely driven by same-period correlation. Technological spillovers explain part of the relationship: IT investment appears to support ESG performance partly by improving technological learning, innovation diffusion, and knowledge accumulation. By contrast, market competition does not significantly change the IT investment–ESG relationship. Additional analysis shows that the positive effect is stronger in state-owned enterprises than in non-state-owned enterprises. The findings imply that IT investment can be viewed not only as a source of operational efficiency, but also as a digital resource that may strengthen firms’ capacity for sustainable governance. Full article

Load-bearing prefabricated concrete sandwich wall panels (LBPCSW) offer potential for rapid construction and energy efficiency, yet their seismic performance requires systematic evaluation. In this study, quasi-static tests and finite element analysis were conducted on LBPCSW specimens with varying height-to-width ratios and embedded column configurations. The results indicate that the LBPCSW specimens exhibit satisfactory structural integrity, with all specimens achieving ductility coefficients greater than 3.0. Specifically, specimen W1 with a height-to-width ratio of 1:1 failed in shear, whereas specimens with a height-to-width ratio of 2:1 exhibited flexural failure. Compared with W1, specimen W2 with embedded columns at the wall ends demonstrated significantly enhanced load-bearing capacity and ductility. Parametric analysis revealed that concrete layer thickness is the dominant factor influencing load-bearing capacity: taking W1 as an example, as the single-side concrete layer thickness increased from 30 mm to 50 mm, the ultimate load-bearing capacity increased from 182 kN to 246 kN, representing a 35% improvement. In contrast, the effect of concrete strength was relatively minor: increasing the strength grade from C25 to C35 raised the ultimate load-bearing capacity from only 223 kN to 255 kN, an increase of merely 14%. It is concluded that the proposed LBPCSW combine favorable seismic performance with energy efficiency, representing a promising solution for shear wall systems in low-rise rural housing in earthquake-prone regions. Full article

The applied design of recycled aggregate concrete (RAC) with supplementary cementitious materials (SCMs) requires reliable estimation of 28-day flexural strength (FS28) before trial batching. This is challenging because RAC–SCM mixtures involve nonlinear interactions among binder chemistry, aggregate replacement, water-to-binder ratio, and admixture dosage. However, most predictive models focus on compressive strength or sustainability optimization, while fewer address FS28 using chemically informed descriptors and independent validation. This study developed and externally validated an XGBoost framework for FS28 prediction. The methodology combined binder characterization by XRF, XRD, SEM, and particle-size analysis; reactivity descriptors; database development; modeling; and experimental validation. A database of 397 mixtures from 22 sources was refined to 382 observations for training and testing, and the model was validated with 58 RAC–SCM mixtures and 174 prismatic specimens tested according to ASTM C78/C78M-22. XGBoost achieved R² values of 91.61%, 80.75%, and 77.62% for training, testing, and validation, with RMSE values of 0.559, 0.835, and 0.364 MPa. Compared with the best alternative models, XGBoost reduced RMSE by 8.6% in testing and 9.5% in validation. Interpretability analysis identified binder reactivity, water-to-binder ratio, aggregate composition, cement content, SCM replacement, and superplasticizer dosage as key factors. Full article

A fly ash-based artificial aggregate with a compressive strength of >60 MPa was prepared via cement activation and alkali activation using >75% fly ash as the principal raw material. The mechanical properties of concrete prepared using this aggregate and the characteristics of the interfacial transition zone (ITZ) were compared with those of concrete containing natural aggregate. The results indicated that the compressive strength of concrete prepared using artificial aggregate was lower than that of concrete prepared using natural aggregate by about 19.0–27.6%. Scanning electron microscopy (SEM) revealed that the cement paste bonded tightly to the surface of the natural aggregate; the width of ITZ was 20–30 µm. The ITZ between the cement paste and the fly ash-based artificial aggregate exhibited a relatively loose structure at 28 d, with a width of 30–40 µm; however, the ITZ became narrower and denser at 90 d. EDS indicated that the principal hydration products were calcite crystals and C-S-H gel in the ITZ of natural aggregate concrete and artificial aggregate concrete. According to nanoindentation tests, for both cement pastes with natural and artificial aggregates, the elastic modulus of the ITZ at 28 d was >10 GPa, and it increased slightly at 90 d. The ITZ between the alkali-activated paste and limestone exhibited a relatively dense structure, with a width of 20–30 µm. The ITZ between the alkali-activated paste and the fly ash-based artificial aggregate exhibited a relatively loose structure with numerous pores at 28 d and had a width of 30–40 µm; however, the ITZ became narrower and denser at 90 d. The principal hydration products were N-A-S-H and C-A-S-H in the two kinds of aggregate concrete. Whether the alkali-activated paste contained natural aggregate or artificial aggregate, the elastic modulus of the ITZ at 28 d was 5–6 GPa, and it increased rapidly to >10 GPa by 90 d. The performance of ITZ is primarily influenced by the matrix materials, while also being influenced by aggregates and curing conditions. Qualitative and quantitative analyses revealed the formation mechanisms of artificial and natural aggregates in different matrices. Through continuous hydration and polymerization reactions, artificial aggregates gradually form narrower and denser interfacial transition zones with different matrices, especially in alkali-activated matrices. The continuously improved performance of the ITZ makes it less prone to forming cracks between the ITZ and the artificial aggregate. This study provides an important theoretical basis for the application of fly ash-based artificial aggregates, which can also be used to produce high-strength concrete. Full article