Search Results (579)

The utilization of recycled concrete aggregate presents an effective solution for construction waste mitigation. However, concrete service in sulfate environments leads to sulfate ion retention in recycled aggregates, substantially impairing their quality and requiring modification approaches. A critical question remains whether traditional recycled aggregate modification techniques can effectively enhance the performance of these sulfate-containing recycled aggregates (SRA). Cement paste wrapping in various proportions was used in this investigation to enhance SRA. The performance of both SRA and modified aggregates was systematically assessed through measurements of apparent density, water absorption, crushing value, and microhardness. Microstructural analysis of the cement wrapping modification mechanism was conducted by scanning electron microscopy coupled with mercury intrusion porosimetry. Results revealed that internal sulfate addition decreased the crushing value and increased the water absorption of recycled aggregates, primarily due to micro-cracks formed by expansion. Additionally, the pores were occupied by erosion products, leading to a slight increase in the apparent density of aggregates. The performance of SRA was effectively enhanced by cement paste wrapping at a 0.6 water–binder ratio, whereas it was negatively impacted by a ratio of 1.0. The modifying effect became even more effective when 15% fly ash was added to the wrapping paste. Scanning electron microscopy observations revealed that the interface of SRA was predominantly composed of gypsum crystals. Cement paste wrapping greatly enhanced the original interface structure, despite a new dense interface formed in the modified aggregates. Full article

The aviation industry is under increasing pressure to reduce its environmental impact while maintaining safety and performance standards. One promising area for improvement lies in the use of sustainable materials in airport infrastructure. One of the issues preventing uptake of emerging sustainable technologies is the lack of guidance relating to the opportunities, potential benefits, associated risks and an implementation plan specific to airport pavements. This research reviewed opportunities to incorporate waste materials into rigid airport pavements, focusing on concrete base slabs. Commonly used supplementary cementitious materials (SCMs), such as fly ash and ground granulated blast furnace slag (GGBFS) were considered, as well as recycled aggregates, including recycled concrete aggregate (RCA), recycled crushed glass (RCG), and blast furnace slag (BFS). Environmental Product Declarations (EPDs) were also used to quantify the potential for environmental benefit associated with various concrete mixtures, with findings showing 23% to 50% reductions in embodied carbon are possible for selected theoretical concrete mixtures that incorporate waste materials. With considered evaluation and structured implementation, the integration of waste materials into rigid airport pavements offers a practical and effective route to improve environmental outcomes in aviation infrastructure. It was concluded that a Triple Bottom Line (TBL) framework—assessing financial, environmental, and social factors—guides material selection and can support sustainable decision-making, as does performance-based specifications that enable sustainable technologies to be incorporated into airport pavement. The study also proposed a consequence-based implementation hierarchy to facilitate responsible adoption of waste materials in airside pavements. The outcomes of this review will assist airport managers and pavement designers to implement practical changes to achieve more sustainable rigid airport pavements in the future. Full article

Coal gangue, a major by-product of coal mining, poses significant environmental challenges due to its large-scale accumulation, land occupation, and potential for air and water pollution. This manuscript presents a comprehensive overview of continuous chamber gangue storage technology as a sustainable mining solution for coal mines. The principles of this approach emphasize minimizing disturbance to overlying strata, enabling uninterrupted mining operations, and reducing both production costs and environmental risks. By storing the surface or underground gangue in continuous chambers, the proposed method ensures the roof stability, maximizes the waste storage, and prevents the interaction between mining and waste management processes. Detailed storage sequences and excavation methods are discussed, including continuous and jump-back excavation strategies tailored to varying roof conditions. The process flows for both underground and ground-based chamber storage are described, highlighting the integration of gangue crushing, paste preparation, and pipeline transport for efficient underground storage. In a case study with annual storage of 500,000 t gangue, the annual economic benefit reached CNY 1,111,425,000. This technology not only addresses the urgent need for sustainable coal gangue management, but also aligns with the goals of resource conservation, ecological protection, and the advancement of green mining practices in the coal industry. Full article

Concrete is a cornerstone material in the construction industry owing to its versatile performance; however, its inherent brittleness, low tensile strength, and poor permeability resistance limit its broader application. Graphene, with its exceptional thermal conductivity, stable lattice structure, and high specific surface area, presents a transformative solution to these challenges. Despite its promise, comprehensive studies on the multifunctional properties and underlying mechanisms of graphene-enhanced concrete remain scarce. In this study, we developed a novel concrete composite incorporating cement, coarse sand, crushed stone, water, and graphene, systematically investigating the effects of the graphene dosage and curing duration on its performance. Our results demonstrate that graphene incorporation markedly improves the material’s density, brittleness, thermal conductivity, and permeability resistance. Notably, a comprehensive analysis of scanning electron microscopy (SEM) images and thermogravimetric (TG) data demonstrates that graphene-modified concrete exhibits a denser microstructure and the enhanced formation of hydration products compared to conventional concrete. In addition, the graphene-reinforced concrete exhibited a 44% increase in compressive strength, a 0.7% enhancement in the photothermal absorption capacity, a 0.4% decrease in maximum heat release, a 0.8% increase in heat-storage capacity, and a 200% reduction in the maximum penetration depth. These findings underscore the significant potential of graphene-reinforced concrete for advanced construction applications, offering superior mechanical strength, thermal regulation, and durability. Full article

Background: A critical review of the literature demonstrates that masticatory apparatus with an artificial oral environment is of interest in the fields including (i) dental science; (ii) food science; (iii) the pharmaceutical industries for drug release. However, apparatus that closely mimics human chewing and oral conditions has yet to be realised. This study investigates the vital role of dental morphology and form–function connections using two-bite test parameters for effective drug release from medicated chewing gum (MCG) and compares them to human chewing efficiency with the aid of a humanoid chewing robot and a bionics product lifecycle management (PLM) framework with built-in reverse biomimetics—both developed by the first author. Methods: A novel, bio-engineered two-bite testbed is created for two testing machines with compression and torsion capabilities to conduct two-bite tests for evaluating the mechanical properties of MCGs. Results: Experimental studies are conducted to investigate the relationship between biting force and crushing/shearing and understand chewing efficiency and effective mastication. This is with respect to mechanochemistry and power stroke for disrupting mechanical bonds releasing the active pharmaceutical ingredients (APIs) of MCGs. The manuscript discusses the effect and the critical role that jaw physiology, dental morphology, the Bennett angle of mandible (BA) and the Frankfort-mandibular plane angle (FMA) on two-bite test parameters when FMA = 0, 25 or 29.1 and BA = 0 or 8. Conclusions: The impact on other scientific fields is also explored. Full article

The semi-autogenous grinding (SAG) mill, renowned for its high efficiency, high production capacity, and low cost, is widely used for crushing and grinding equipment. However, the current understanding of the overall particle behavior influencing its efficiency remains relatively limited, particularly the impact of the shape of SAG mill liners on material behavior. This study employs discrete element method (DEM) simulation technology to investigate the effects of different liner structures on particle trajectories and collision energy, systematically investigating the impact of lifter bars angle, height, and the number of lifter bars on grinding efficiency. The results of single-factor simulations indicate that when the lifter bars height (230 mm) and the number of lifter bars (36) are fixed, the total collision energy dissipation between steel balls and ore, as well as among ore particles, reaches a maximum of 526,069.53 J when the lifter bars angle is 25°. When the lifter bar angle is fixed at 25° and the number of lifter bars is set to 36, the maximum collision energy dissipation of 627,606.06 J occurs at a lifter bars height of 210 mm. When the angle (25°) and height (210 mm) are fixed, the highest energy dissipation of 443,915.37 J is observed with 12 lifter bars. Results from the three-factor, three-level orthogonal experiment reveal that the number of lifter bars exerts the most significant influence on grinding efficiency, followed by the angle and height. The optimal combination is determined to be a 20° angle, 12 lifter bars, and a 210 mm height, resulting in the highest total collision energy dissipation of 700,334 J. This represents an increase of 379,466 J compared to the original SAG mill liner configuration (320,868 J). This research aims to accurately simulate the motion of discrete particles within the mill through DEM simulations, providing a basis for optimizing the operational parameters and structural design of SAG mills. Full article

Circulating fluidized bed fly ash (CFBFA) stockpiles release alkaline dust, high-pH leachate, and secondary CO₂/SO₂—an environmental burden that exceeds 240 Mt yr⁻¹ in China alone. Yet, barely 25% is recycled, because the high f-CaO/SO₃ contents destabilize conventional cementitious products. Here, we presents a pressurized flue gas heat curing (FHC) route to bridge this scientific deficit, converting up to 85 wt% CFBFA into structural lightweight gravel. The gypsum dosage was optimized, and a 1:16 (gypsum/CFBFA) ratio delivered the best compromise between early ettringite nucleation and CO₂-uptake capacity, yielding the highest overall quality. The optimal mix reaches 9.13 MPa 28-day crushing strength, 4.27% in situ CO₂ uptake, 1.75 g cm⁻³ bulk density, and 3.59% water absorption. Multi-technique analyses (SEM, XRD, FTIR, TG-DTG, and MIP) show that FHC rapidly consumes expansive phases, suppresses undesirable granular-ettringite formation, and produces a dense calcite/needle-AFt skeleton. The FHC-treated CFBFA composite gravel demonstrates 30.43% higher crushing strength than JTG/TF20-2015 standards, accompanied by a water absorption rate 28.2% lower than recent studies. Its superior strength and durability highlight its potential as a low-carbon lightweight aggregate for structural engineering. A life-cycle inventory gives a cradle-to-gate energy demand of 1128 MJ t⁻¹ and a process GWP of 226 kg CO₂-eq t⁻¹. Consequently, higher point-source emissions paired with immediate mineral sequestration translate into a low overall climate footprint and eliminate the need for CFBFA landfilling. Full article

This study investigates a lithium-ion battery failure in heating insoles that ignited during normal walking while powered off. Through comprehensive material characterization, electrical testing, thermal analysis, and mechanical gait simulation, we systematically excluded electrical or thermal abuse as failure causes. X-ray/CT imaging localized the ignition source to the lateral heel edge of the pouch cell, correlating precisely with peak mechanical stress identified through gait analysis. Remarkably, the cyclic load was less than 10% of the single crush load threshold specified in safety standards. Key findings reveal multiple contributing factors as follows: the uncoated polyethylene separator’s inability to prevent stress-induced internal short circuits, the circuit design’s lack of battery health monitoring functionality that permitted undetected degradation, and the hazardous placement inside clothing that exacerbated burn injuries. These findings necessitate a multi-level safety framework for lithium-ion battery products, encompassing enhanced cell design to prevent internal short circuit, improved circuit protection with health monitoring capabilities, optimized product integration to mitigate mechanical and environmental impact, and effective post-failure containment measures. This case study exposes a critical need for product-specific safety standards that address the unique demands of wearable lithium-ion batteries, where existing certification requirements fail to prevent real-use failure scenarios. Full article

In tight sandstone gas reservoirs, proppant flowback severely limits stable gas production. This study uses laboratory flowback experiments and field analyses of the ShaXimiao tight sandstone in the Wenxing gas area to investigate the mechanisms controlling sand production. The experiments show that displacing fluid viscosity significantly affects the critical sand-flow velocity: with high-viscous slickwater (5 mPa·s), the critical velocity is 66% lower than with low-viscous formation water (1.15 mPa·s). The critical velocity for coated proppant is three times that of the mixed quartz sand and coated proppant. If the confining pressure is maintained, but the flow rate is further increased after the proppant flowback, a second instance of sand production can be observed. X-ray diffraction (XRD) tests were conducted for sand produced from practical wells to help find the sand production reasons. Based on experimental and field data analysis, sand production in Well X-1 primarily results from proppant detachment during rapid shut-in/open cycling operations, while in Well X-2, it originates from proppant crushing. The risk of formation sand production is low for both wells (the volumetric fraction of calcite tested from the produced sands is smaller than 0.5%). These findings highlight the importance of fluid viscosity, proppant consolidation, and pressure management in controlling sand production. Full article

This research focuses on improving the characteristics of recycled concrete and utilizing solid waste resources through the combination of industrial waste pre-impregnation and the carbonation process. A novel pre-impregnation–carbonation aggregate method is proposed to increase the content of carbonatable components in the surface-bonded mortar of recycled coarse aggregate by pre-impregnating it with carbide slag slurry (CSS). This approach enhances the subsequent carbonation effect and thus the properties of recycled aggregates. The experimental results showed that the method significantly improved the water absorption, crushing value, and apparent density of the recycled aggregate. Additionally, it enhanced the compressive strength, split tensile strength, and flexural strength of the recycled concrete produced using the aggregate improved by this method. Microanalysis revealed that CO₂ reacts with calcium hydroxide and hydrated calcium silicate (C-S-H) to produce calcite-type calcium carbonate and amorphous silica gel. These reaction products fill microcracks and pores on the aggregate and densify the aggregate–paste interfacial transition zone (ITZ), thereby improving the properties of recycled concrete. This study presents a practical approach for the high-value utilization of construction waste and the production of low-carbon building materials by enhancing the quality of recycled concrete. Additionally, carbon sequestration demonstrates broad promise for engineering applications. Full article

Solar fuels production requires developing redox active materials with porous structures able to withstand thermochemical cycles with enhanced thermal stability under concentrated solar irradiation conditions. The mechanical performance of 3D-printed, macroporous black zirconia gyroid structures, coated with redox-active ceria, was assessed for their suitability in solar thermochemical cycles for CO₂ and H₂O splitting. Experiments were conducted using a 1.5 kW solar furnace to supply the high-temperature concentrated heat to a windowed reaction chamber to carry out thermal redox cycling under realistic on-sun conditions. The ceria coating on ceramic structures improved the thermal stability and redox efficiency while minimizing the quantity of the redox material involved. Crushing strength measurements showed that samples not directly exposed to the concentrated solar flux retained their mechanical performance after thermal cycling (~10 MPa), while those near the concentrated solar beam focus exhibited significant degradation due to thermal stresses and the formation of Ce_xZr_1−xO₂ solid solutions (~1.5 MPa). A Weibull modulus of 8.5 was estimated, marking the first report of such a parameter for fused filament fabrication (FFF)-manufactured black zirconia with gyroid architecture. Failure occurred via a damage accumulation mechanism at both micro- and macro-scales. These findings support the viability of ceria-coated cellular ceramics for scalable solar fuel production and highlight the need for optimized reactor designs. Full article

Hydraulic fracturing is a key stimulation technique for enhancing the productivity of tight sandstone reservoirs, with the conductivity of propped fractures serving as a critical parameter for evaluating stimulation effectiveness. This study investigated the conductivity behavior of propped fractures through laboratory experiments using commonly used oilfield proppants. The effects of proppant size, type, concentration, and proppant combination on fracture conductivity were systematically evaluated. Results show that at low closure stress, conductivity differences among various proppant types are negligible. However, under high closure stress, proppants with lower compressive strength exhibit significantly higher crushing rates, resulting in reduced conductivity compared to high-strength proppants. In mixtures of silica sand and ceramic proppant proppants, increasing the ceramic content lowers the overall crushing rate and mitigates conductivity degradation. Additionally, blending proppants of different sizes under high stress reduces breakage, with finer particles contributing to this effect. Higher proppant concentrations also lead to lower crushing rates and improved fracture conductivity. This work provides valuable insights into optimizing proppant selection and design for reservoir stimulation and oil and gas recovery. Full article

Previous research on geopolymers has not fully established their porosity and its influence on the matrix structure, as well as its relevance to mechanical and durability properties, supporting the potential of this material as a sustainable alternative to traditional construction materials. In this study, three geopolymer mortar (GM) mixtures were prepared: the first was obtained with fly ash (FA) without mechanical grinding (GM_FA), the second with FA that required crushing and sieving through a #200 sieve (GM_FA_200), and the third was a GM with FA that required crushing and sieving through a #325 sieve (GM_FA_325). The main objective was to evaluate the porosity of the geopolymeric paste and the interfacial transition zone (ITZ) between the aggregate and the geopolymerization products. Due to the susceptibility of this area to develop higher porosity, which leads to reduced mechanical properties and durability, it has become a significant focus of investigation in materials such as concrete and mortar. These analyses were carried out using physical adsorption of gases (PAG), and a methodology for image analysis of GM microporosity was implemented using micrographs obtained from a scanning electron microscope (SEM) and processed with the NI Vision Assistant 8.6 software (VA). The results from both image analysis and physical adsorption demonstrated that the GM_FA_325 matrix exhibited 19% less porosity compared to the GM_FA matrix. The results confirmed that GMs are predominantly mesoporous. It was observed that GM_FA_325 has the lowest total porosity, resulting in a denser and more compact microstructure, which is a key factor in its mechanical performance and potential applications as an eco-friendly construction material for coatings and precast elements such as blocks, panels, and similar products. In addition, image analysis using VA is highlighted as an efficient, cost-effective, and complementary technique to PAG, enabling robust results and resource optimization. Full article

Geometallurgy is an approach that utilizes predictive models that can support business decisions, mitigate risks, and enhance production efficiency. To develop an accurate geometallurgical model, it is essential to understand the behavior of each lithology within the ore body through geometallurgical testing. In this context, the present study aims to evaluate the performance of bench-scale tests conducted on the main mining fronts of a zinc mine operation located in Brazil. The mineral processing plant was designed to process lead and zinc sulfide ores without material stockpiling, where all ores extracted from the underground mine are immediately processed. The geometallurgical characterization was conducted through the following steps: sampling, crushing, grinding, and flotation. The recovery, concentrate, and tailing contents during the flotation stages of galena and sphalerite were analyzed. A mineralogical characterization using a Mineral Liberation Analyzer (MLA) was performed to assess the degree of particle liberation and mineral associations within the studied mining fronts. The results indicate that a higher degree of pyrite liberation leads to greater metallurgical recovery of mineralized bodies A (breccia-hosted orebody), B (sphalerite-rich doloarenite orebody), and C (upper replaced stratiform orebody). Among these, mineralized body C presents the highest recovery in the zinc and lead stages, with 99.5% and 86.2%, respectively. Full article

Background: Numerous experimental studies aim to improve outcomes of peripheral nerve repair following trauma. This study evaluates the efficacy of the human epineural patch (hEP) compared to the human amniotic membrane (hAM) in promoting nerve regeneration following sciatic nerve crush injury. Methods: Thirty-six athymic nude rats were divided into three groups (n = 12 per group) following nerve crush: (1) an unprotected injury site; (2) crush injury wrapped with hEP; and (3) crush injury wrapped with hAM. Animals were assessed over 6 or 12 weeks post-injury. Evaluations included motor recovery (Toe-Spread test), sensory recovery (Pinprick test), muscle denervation atrophy (the gastrocnemius muscle index (GMI)), histomorphometry (myelin thickness, axonal density, fiber diameter, and percentage of myelinated fibers), and immunofluorescence (GFAP, Laminin B, NGF, S-100, VEGF, vWF, HLA-DR, and HLA-I) assessments. Results: The hEP group showed superior motor recovery, axonal density and higher GMI values compared to the hAM and control groups. The increased expression of neurogenic and angiogenic markers highlighted its neuroregenerative potential. Negligible HLA-DR and HLA-I expression confirmed the lack of hEP and hAM immunogenicity. Conclusions: The application of hEP following sciatic nerve crush injury facilitated nerve regeneration, improved functional outcomes, and offered a viable alternative to hAM. Structural stability and the regenerative capacity position hEP as a new, promising off-the-shelf product for nerve regeneration. Full article