Search Results (580)

With intensifying mineral resource extraction, groundwater ingress in large cross-sectional intersection roadways near aquifers is becoming increasingly common. Disturbances from roadway excavation and mining may induce fractures connecting to aquifers and a series of related adverse hydrogeological effects, posing severe challenges to surrounding rock stability control of such excavations. Large-span roadway intersections in water-bearing sandstone–mudstone interbedded weak strata are frequently subjected to severe instability, bringing great challenges to the design of roadway supports. A typical large-section intersection roadway from a mine in Xinjiang is taken as the research object. Systematic research is carried out via field investigation, numerical modeling and field testing. Results show that the original aquiclude structure of sandstone–mudstone interbeds is destroyed by excavation disturbance. Mudstone strength degradation induced by sandstone pore water migration is confirmed as the core cause of surrounding rock instability. Surrounding rock deformation increases rapidly with the rise in mudstone moisture content, and obvious sudden change characteristics are presented when the water content approaches saturation. A collaborative support strategy with waterproofing as the core is proposed. Targeted drainage, high-reliability zoned support and anti-corrosion measures for support components are set as supporting measures. The proposed strategy is verified to perform well in field industrial tests. Waterproof measures, waterproof anchoring agents, anchor cable grouting and high-performance anchor-mesh-cable shotcreting support are integrated in the strategy. Surrounding rock deformation can be effectively controlled and a good application effect is achieved. The proposed support system is also applicable to roadway projects in metal and non-metal mines with similar geological conditions. Full article

The long-term reliability of XLPE submarine cable insulation is influenced by progressive thermal degradation during operation and subsequent seawater ingress caused by external damage. Although thermal aging and seawater exposure have been widely investigated individually, the influence of the prior thermal-aging state on the subsequent seawater-induced degradation behavior of XLPE remains insufficiently understood. In this study, XLPE insulation specimens prepared from the same commercial compound used for 500 kV submarine cables were subjected to sequential accelerated aging consisting of controlled thermal pre-aging followed by simulated seawater exposure. Broadband dielectric spectroscopy, AC breakdown testing with two-parameter Weibull analysis, scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) were employed to investigate the evolution of electrical properties, surface morphology, and molecular structure. The results demonstrate that seawater-induced electrical deterioration strongly depends on the initial thermal-aging state of XLPE. Increasing thermal pre-aging duration resulted in progressively higher relative permittivity and dielectric loss, together with reduced characteristic breakdown strength after subsequent seawater exposure. Under the most severe condition of 1440 h thermal pre-aging followed by 672 h seawater exposure, the power–frequency relative permittivity increased by 32.1%, while the characteristic breakdown strength decreased by more than one-third compared with the initial state. SEM observations revealed that thermally pre-aged specimens developed accelerated surface damage during seawater exposure, including pores, cracks, corrosion pits, and honeycomb-like structures. FTIR analysis further indicated molecular-chain degradation and increased hydroxyl-related species during sequential aging. These results suggest that thermal-aging-induced molecular oxidation, polar-group formation, and microstructural defects enhance water and ion penetration pathways, thereby increasing the susceptibility of XLPE insulation to subsequent seawater-induced degradation. This study provides material-level experimental evidence for understanding sequential aging processes in submarine cable insulation and highlights the importance of considering historical thermal damage in future condition assessment and lifetime evaluation models. Since accelerated laboratory conditions were adopted, the results should be interpreted as comparative degradation characteristics rather than direct predictions of field-service lifetime. Full article

Barrier layers are an essential component of flexible packaging for products susceptible to degradation or spoiling through ingress of water vapour or oxygen, which can readily penetrate conventional polymeric films. Vacuum metallisation of thin films for polymer packaging is widely employed to provide these barrier properties and hence extend the shelf life of the product. However, the environmental impacts associated with producing this metallised layer for packaging solutions are yet to be fully investigated or reported in the literature in the form of a Life Cycle Assessment (LCA). Using 87% primary data derived directly from industry, this study considers in detail all inputs, consumables, and outputs necessary to commercially produce a vacuum-metallised layer onto a high-area roll-to-roll polymer film substrate. A rating of “excellent quality” as per the industry-recognised pedigree matrix, along with validation of the data and acquisition procedures by relevant industrial experts throughout the production chain and adherence to (ISO) 14040:2006 and (ISO) 14044:2006, ensures the highest standards of quality assurance and rigour. The Life Cycle Impact Assessment (LCIA) was performed for impact categories of climate change, freshwater consumption, and energy consumption, using the ReCiPe 2016 midpoint (H) methodology. Whilst the metalliser operation contributed the greatest energy use in the process, half of the climate change emissions and the majority of freshwater consumption were attributed to the raw materials and transportation. It should be noted that other converting processes experience a higher energy consumption (more than double) due to additional drying steps. A comparative LCA study was conducted, employing only secondary data found from publicly available literature and databases. The findings from this comparative study highlight significant overestimation of environmental impact, hence emphasising the importance of using up-to-date primary data wherever possible to reduce uncertainty in environmental impact from LCA. Full article

Conventional valorization of blast furnace slag commonly involves granulation, fine grinding, mechanical activation, or chemical activation, which increase energy demand and processing complexity. This study investigated a minimally processed blast furnace slag (MP-BFS), defined here as the fraction passing 64 µm obtained by sieving a 0–8 mm industrial material without grinding, additional granulation, thermal treatment, or chemical activation. MP-BFS replaced 10–50% of the cement by mass to reduce clinker in industrial mortars formulated at a constant flow spread of 23–24 cm and tested from 8 h to 90 d. Bulk density, water-accessible porosity, total and capillary water absorption, and compressive and flexural strengths were evaluated. Replacing 10% of the cement with slag improved compressive strength from the earliest test age and increased the 28-day compressive and flexural strengths by 5.1% and 9.5%, respectively, relative to the control mortar; this response coincided with a reduction in measured porosity from 8.95% to 8.01%. This improvement is consistent with a physical filling effect and improved particle packing, although these mechanisms were not directly verified by microstructural analyses. At higher replacement levels, water-accessible porosity increased, reaching 24.45% at 50% slag replacement, alongside greater water ingress and delayed strength development. Exploratory empirical regression analyses described associations among slag content, porosity, water transfer, and compressive strength within the investigated formulations. A simplified screening-level constituent-production-and-transport comparison per cubic meter, based on generic ICE factors and an assumed 50 km transport distance, estimated a maximum embodied carbon reduction of 44% at 50% replacement. Curing energy, use, carbonation, maintenance, and end-of-life stages were excluded. Overall, 10% MP-BFS replacement provided the most favorable performance–carbon content balance, whereas 30–50% achieved larger carbon reductions but showed early-age strength losses that limit their suitability for rapid-demolding applications under the investigated conditions. Full article

Underwater concrete infrastructure is gradually damaged by water scouring, chloride ingress, freeze–thaw cycles, and fatigue loading, so reliable in situ repair materials are increasingly needed. Conventional cement-based repair materials are often unsuitable for underwater use because they disperse in water, bond weakly to wet substrates, and show limited durability. Polymer-modified cementitious materials can reduce these problems by combining cement compatibility with polymer film formation and interfacial strengthening. Water-soluble polymers mainly improve fresh-state cohesion and anti-washout performance through adsorption, bridging, and flocculation regulation. In comparison, polymer emulsions and latexes are more effective after hardening, improving bonding, crack resistance, and durability through polymer films and organic–inorganic networks. For self-leveling underwater repair, the flow spread should reach at least 130 mm. For vertical repair with a 20 mm layer, a yield stress of about 360 Pa is needed to prevent sagging. Therefore, performance should not be judged by strength alone, but by constructability, interfacial water films, and pore connectivity. Future studies should consider responsive polymers, multi-component modification, standardized tests, and low-carbon binders. Full article

This study reports the synthesis of low-defect Prussian blue analogues (PBAs) using a single iron-source method and systematically investigates the influence of atmospheric components, particularly water and oxygen, on their oxidative decomposition. Our findings demonstrate that the oxidative degradation of PBAs is governed synergistically by moisture and oxygen, with ambient humidity identified as the primary factor determining both the extent and kinetics of their decomposition. Notably, a pure oxygen environment by itself does not trigger material degradation, while oxygen markedly accelerates the decomposition only in the presence of moisture. As a result of the oxidation, enhanced Coulombic interaction between sodium ions and cyano groups induces structural modifications in the lattice framework, driving a phase transformation from monoclinic to cubic symmetry, accompanied by changes in its unit cell volume. Furthermore, in high-humidity environments, atmospheric moisture promotes the gradual deintercalation of sodium ions from the Prussian blue framework, resulting in the conversion of sodium-rich Prussian blue to the sodium-deficient form. Concurrently, an increase in lattice defect density leads to partial structural collapse, inducing the release of free ferrocyanide ions, which may subsequently react with the deintercalated sodium ions to form the sodium ferrocyanide impurity phase. We also find that the preferential decomposition of low-spin iron over high-spin iron within the framework leads to a further reduction in its electrochemical capacity. In contrast, potassium Prussian blue exhibits minimal interaction with water molecules and can effectively repel them through steric hindrance. Therefore, partial substitution of sodium with potassium ions is proposed as a viable strategy to enhance the structural stability of the Prussian blue framework, improve the storage performance of sodium Prussian blue (NaPB), and mitigate water ingress. This work offers fundamental insights into the storage characteristics and oxidative degradation mechanisms of PBAs. Full article

Graphene-based nanosheets (GNS), including graphene, graphene oxide (GO), reduced graphene oxide (rGO), and graphene nanoplatelets (GNPs), have attracted increasing attention for developing high-performance and sustainable cementitious composites. Compared with conventional dispersion strategies, graphene-based coating strategies enable the targeted localization of GNS at critical interfacial transition zones (ITZs), thereby maximizing their reinforcing efficiency while mitigating agglomeration issues. This review systematically summarizes recent advances in GNS coating technologies for cementitious composites, including physical adsorption, chemical assembly, electrophoretic deposition, and in situ growth. The effects of GNS coatings on interfacial engineering, mechanical performance, durability enhancement, and smart functionalities are critically discussed. Existing studies indicate that GNS coatings can improve strength, crack resistance, impermeability, and resistance to chloride ingress, freeze–thaw cycles, and other degradation processes mainly through ITZ densification and microstructure refinement. However, these benefits are strongly dependent on the coating method, substrate type, and stability of the graphene–substrate interface in calcium-rich alkaline pore solutions. In particular, physically adsorbed GO coatings may suffer from desorption or Ca²⁺-induced aggregation, chemically assembled coatings require further validation beyond laboratory-scale systems, and electrophoretic deposition is mainly applicable to electrically conductive substrates. In addition, localized conductive networks created by GNS coatings facilitate multifunctional properties such as self-sensing, electromagnetic shielding, and electrothermal performance. From a carbon-neutrality perspective, the improvements in mechanical properties and durability provide opportunities to reduce material consumption, extend service life, and lower life-cycle carbon emissions. Nevertheless, their carbon-neutral contribution should be verified through quantitative life-cycle assessment rather than inferred directly from strength or durability enhancement alone. Finally, the remaining challenges associated with large-scale implementation, long-term stability, cost-effectiveness, and field-scale validation are discussed. Particular attention is given to the fact that most existing evidence is derived from laboratory-scale specimens rather than real structural elements exposed to service environments. Full article

Hydrogen–steel interactions remain a critical concern for the safe deployment of hydrogen–natural gas mixtures in pipeline infrastructures. Thermally grown iron oxides may be a good barrier to hydrogen ingress into the crystalline lattice of pipeline steels, but their actual effectiveness depends strongly on their composition and stability under service conditions. Several experimental approaches have been proposed to investigate the correlation between thermally grown oxides and hydrogen permeation. Among these, electrochemical permeation testing offers a more complex but safer methodology compared to pressurized hydrogen gas tests. However, when the oxide is directly exposed to the charging side (cathodic charging conditions), permeation behaviour often appears comparable to that of bare steel, and rapid oxide degradation occurs. This study introduces an alternative permeation testing configuration that enables direct assessment of thin thermally grown oxides while preserving their structural integrity. By deliberately placing the oxide on the anodic detection side, mechanical removal during hydrogen evolution is suppressed, allowing the intrinsic resistance of the oxide to hydrogen transport to be evaluated. Carbon steel samples were thermally oxidized at 250 °C for controlled exposure times, and the resulting oxide scales were characterized by Raman spectroscopy, revealing variations in hematite and magnetite fractions. Hydrogen permeation was evaluated using a Devanathan–Stachurski cell by positioning the oxidized surface either on the cathodic charging side or on the anodic detection side. Under these conditions, significant variations in apparent steady-state permeation current density were observed as a function of oxidation time and oxide composition. Full article

As a critical insulation component in cable systems, the cable terminal is susceptible to defects caused by human and environmental factors during manufacturing, installation, and service. Such defects may lead to local electric-field distortion and insulation weaknesses at the cable terminal, posing a severe threat to the safe operation of the cable system. In this study, an electric-field simulation model of a 10 kV cable terminal was implemented to investigate the effects of various defects, such as insufficient stress-cone overlap, axial scratch, ring-cut defect, and moisture ingress on the cable terminal. The results show that insufficient stress-cone overlap produces a severe field distortion, and the distortion level is strongly correlated with the misalignment distance. For mechanical damage defects, axial scratches and ring-cut defects mainly distort the electric field inside the air gap, and defect position induces a stronger distortion level than that of defect depth. With increasing ring-cut depth, the maximum value of distorted electric field first decreases and then rises slightly. For moisture defects, the distorted field primarily occurs at the angle between the water-film tip and the stress cone, where the maximum value appears near the XLPE/SIR interface. These results provide a theoretical basis for defect diagnosis, structural optimization, and assembly process control of cable terminals. Full article

Freshwater scarcity is driving the construction industry to seek alternative mixing waters, and seawater is an abundant resource; however, its suitability is commonly judged by total salinity, which overlooks the fact that coastal seawater chemistry varies hugely between locations and may govern long-term strength performance in varying locations. To address this problem, this study investigates the long-term strength performance and its microstructural and phase transformation of cement mortars mixed with seawater, with the aim of establishing a technical understanding between region-specific seawater chemistry and mortar strength. Seawater was collected from four coastal locations in Tamil Nadu, India, and characterized for chloride, sulfate, magnesium, organic solids, and related parameters. The cement mortar cubes were cast with each seawater, and compressive strength was measured from 3 to 360 days; the microstructural and phase changes underlying the strength behavior were examined at 360 days using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). All samples showed accelerated early-age strength gain from the catalytic effect of chloride and sulfate ions, followed by strength loss at later ages caused by the same ionic environment, with a critical strength loss between 28 and 56 days. The Chennai sample, with the highest chloride and sulfate concentrations, suffered the most severe degradation of 11.5% loss of peak strength, which is attributed to ettringite and gypsum formation together with magnesium attack that consumed Portlandite to form non-cementitious brucite and secondary Calcite. In contrast, the Rameshwaram sample, with exceptionally low sulfate, exhibited superior stability with 3.5% loss, while Puducherry and Tuticorin showed intermediate degradation of 3.9% and 7.8% respectively, with the Puducherry sample further compromised by high organic solids. The results identify the chloride to sulfate ratio, rather than total salinity, as the key predictor of long-term strength performance. The main takeaway for the cement industry is that the suitability of seawater as mixing water is highly site-specific, and a detailed chemical analysis quantifying sulfate and magnesium content is an indispensable prerequisite for strength assessment and material selection before seawater is adopted in marine and coastal construction. Full article

To investigate the influence of propeller rotational speed on the flooding process, sailing trajectory, and motion responses of a damaged surface naval ship under various sea conditions, numerical simulations were conducted using STAR-CCM+. The study is based on the Finite Volume Method (FVM), the Volume of Fluid (VOF) approach, the body force method, overset grids, and a multi-degree-of-freedom motion system. The flooding behavior, trajectory evolution, and hydrodynamic responses of the damaged naval ship were analyzed under calm water, head sea, and beam sea conditions, each at four distinct propeller speeds. The research findings indicate that, regardless of the sea state, a damaged naval ship initially travels in a straight line for a certain distance before transitioning into a curved trajectory. The length of the straight-line travel remains largely unaffected by variations in propeller rotational speed but varies with different sea conditions. Notably, under beam sea conditions, this distance exhibits a significant reduction. The subsequent curved motion trajectory is significantly influenced by the propeller rotational speed and varying wave directions. In calm water, the motion exhibits repetitive circular trajectories toward the damaged side, with the diameter of the circular path increasing as the propeller speed rises. Under head and beam sea conditions, the vessel exhibits a helical motion, with the trajectory becoming more pronounced as the propeller rotational speed increases. In all three wave conditions, the maximum cumulative ingress of the damaged compartment is positively correlated with the propeller speed, whereas the ship’s roll, pitch, and heave motions exhibit distinct variation trends. Full article

Wood- and lignocellulosic-residue-derived constituents have attracted increasing attention in cementitious materials because they may support clinker reduction, waste valorization, moisture regulation, crack control, and longer service life. This review synthesizes evidence on wood ash, wood-derived biochar, and wood or lignocellulosic fibers in low-clinker and low-carbon-oriented cementitious systems, with emphasis on severe cold service involving freeze–thaw cycling, salt freezing, and chloride ingress. This review clarifies the evidence boundaries among direct wood-derived materials and related biomass or lignocellulosic analogues, because wood ash, non-wood biomass ashes, such as bamboo ash and bagasse ash, wood fiber, and non-wood plant fibers cannot be treated as equivalent materials. Wood ash is best regarded as a controlled partial binder replacement or filler whose performance depends on combustion temperature, oxide composition, alkali content, residual carbon, fineness, and water demand. Biochar is more appropriately treated as a low-dosage functional additive, commonly in the range of approximately 1–3 wt.% of binder, where it may assist internal curing, nucleation, moisture redistribution, and pore regulation; excessive dosage can increase porosity and reduce mechanical or transport performance. Wood and lignocellulosic fibers mainly contribute to crack control, toughness, and post-cracking behavior, but their effectiveness is limited by water absorption, swelling, lignin- and extractive-related hydration interference, and long-term interfacial degradation in alkaline matrices. Across these material classes, engineering performance is governed by the interfacial transition zone, pore-size distribution, moisture state, air–void compatibility, and exposure-specific durability response. The main contribution of this review is to propose a boundary-conscious framework for material classification, quantitative comparison, mixture-design screening, and severe-cold durability qualification. Future application requires source-specific characterization, water-demand control, treated fibers, low-dosage biochar optimization, and service-informed testing that couples freeze–thaw cycling, chloride transport, saturation state, and microstructural verification. Full article

The durability of cement-based materials is strongly affected by ionic ingress and transport within calcium silicate hydrate (C-S-H) nanopores, governing their long-term degradation in saline environments. However, the coupled effects of pore size and salinity on nanoscale ionic behaviors remain insufficiently understood, limiting the mechanistic interpretation of durability evolution in cementitious systems. Existing studies have mainly considered pore size and solution salinity separately, while a systematic understanding of their coupling effects on ionic spatial distribution, transport properties and regime transitions is still lacking. In this study, molecular dynamics simulations are performed for NaCl solutions confined in C-S-H nanopores with pore sizes of 2.5–12.5 nm and salinities of 0–2 M. Results show layered water and ion structures that become increasingly confined with decreasing pore size. Increasing salinity enhances ion accumulation while suppressing water mobility due to competitive adsorption. Ion diffusion is significantly lower than that of water molecules, while transport parallel to the C-S-H surface is much higher than in the perpendicular direction, indicating strong anisotropy. Regime-dependent diffusion behaviors are observed across pore size–salinity conditions. These findings deepen the understanding of water and ionic transport and adsorption, improving durability models for cement-based materials in construction engineering. Full article

Silicone rubber is an important external insulating material for composite bushings, composite insulators, and other power equipment. During long-term service, it is inevitably exposed to coupled environmental and electrical stresses, such as elevated temperature, moisture ingress, strong electric fields, and partial discharge, which may lead to hydrophobicity loss, surface chalking, crack propagation, and particle shedding. To reveal the microscopic degradation mechanism of silicone rubber under complex operating conditions, a molecular model of methyl vinyl silicone rubber was constructed using Materials Studio. A stable silicone rubber molecular structure was obtained through crosslinking, geometry optimization, and ensemble relaxation. Subsequently, a reactive molecular dynamics simulation system under coupled temperature–humidity–electric field conditions was established using LAMMPS and the ReaxFF reactive force field. Different temperature gradients, electric field intensities, and aging–recovery stages were designed to investigate the degradation behavior of silicone rubber. The evolution of the maximum carbon content, maximum silicon content, carbon-containing decomposition products, and typical small-molecule products, including H₂, H₂O, CH₄, C₂H₂, C₂H₄, and C₂H₆, was statistically analyzed. In addition, atomic trajectory tracking was performed to clarify the processes of methyl group detachment, Si-O bond cleavage, water molecule participation, and molecular chain reconstruction. The results show that high temperature mainly promotes methyl group detachment from side chains and fracture of the siloxane main chain, while a strong electric field accelerates the decomposition process and induces the transformation of long siloxane chains into shorter chains. Water molecules can react with broken siloxane chains to form hydroxyl-containing structures, making the structural degradation partially irreversible. The degradation process of silicone rubber under coupled temperature–humidity–electric field stress can be summarized as side-chain detachment, main-chain scission, water-assisted reactions, free-radical recombination, and local molecular aggregation. This study provides a molecular-level theoretical basis for aging mechanism analysis, condition assessment, and lifetime prediction of composite external insulating materials. Full article

The durability of reinforced concrete is closely related to the transport behavior of water and aggressive ions within the complex nanoporous network of calcium silicate hydrate. While molecular dynamics simulations provide critical atomistic insights into these confined transport behaviors, their immense computational cost limits their scalability to complex structural and temporal domains. To overcome this bottleneck, we propose a novel, modular computational framework that synergizes high-throughput molecular dynamics with advanced graph neural networks. By rigorously learning the mapping between the local atomic environment and kinetic behaviors, our model achieves high-fidelity predictions of pore water diffusion coefficients in saturated calcium silicate hydrate while improving computational efficiency by three orders of magnitude compared to conventional force field methods. Furthermore, the model demonstrates strong transferability and can accurately capture localized nonlinear diffusion characteristics in multiparticle pore structures with rough surfaces. Building on the interchangeability of this framework’s core modules, we envision a visionary multiscale computational strategy that dynamically couples nanoscale atomistic predictions with mesoscale simulations. This work not only provides an ultrafast, highly accurate tool for screening transport properties across diverse structural configurations but also lays the groundwork for next-generation multiscale modeling of chloride ingress, ultimately advancing the design of resilient and sustainable reinforced concrete. Full article