Search Results (130)

Various methods for classifying and evaluating the shape, size, and surface texture of sand particles are examined, highlighting their impact on concrete mixture properties. This study emphasizes the role of particle morphology in determining concrete workability and segregation, particularly in glass-fiber-reinforced (GRC) thin-layer concrete for building facade panels. The effects of different aggregate types on concrete workability and segregation are analyzed, showing that aggregates with spherical particles and a lower elongation index improve mixture consistency and reduce segregation. Three types of fine aggregates were used (instead of quartz sand in the mixtures, natural sand and granite screenings were chosen, which would be a sustainable alternative to quartz sand), and thin-layer glass-fiber-reinforced concrete using aggregates of different shapes was characterized by layering the mixture. The workability and segregation of fine-grained fiberglass-reinforced concrete mixtures depend on the aggregate particles’ shape. Up to 50% of quartz sand can be replaced with granite siftings or natural sand, as measured by the segregation index, as calculated according to the method proposed in this paper. Increasing the amount of natural sand from 10% to 50% also increases the segregation index from 1.9 to 2.6, and when using granite sifting aggregates, it rises from 2.6 to 3.5. Aggregates with spherical particles are more suitable for this thin-layer GRC concrete, if we examine the consistency parameters of fresh concrete and the possibilities of working with it in real production conditions. Full article

Three-dimensionally printed (3DP) samples with quartz sand effectively avoid the heterogeneity of reservoir rocks in underground gas storage (UGS), providing reliable supports for rock mechanics research under cyclic injection–production pressures. A study on the mechanical properties of 3DP rock samples was conducted by coupling triaxial tests with discrete element method (DEM) simulation. Key results are as follows: (1) The graded particle model (GPM) based on actual particle size distribution (PSD) closely matched experimental data, with an average peak strength error of 1.13%. (2) Cyclic saturation post-processing with silica sol significantly enhanced mechanical properties, increasing peak strength from 5.70 to 52.84 MPa and inducing a plastic-to-brittle failure transition. A power-law relationship was identified between saturation cycles and macroscopic strength. (3) DEM simulations revealed that bond effective modulus linearly controls Young’s modulus. The influence of cohesion on peak strength is greater than that of the friction angle, and the bond stiffness ratio regulates shear failure threshold. The cohesion force is 50 MPa, and the peak strength has been increased to 107.89 MPa. (4) Enhancing particle cohesive strength was key to improving the mechanical properties of 3DP rock samples. This study provides a reliable framework for customized 3DP rock preparation and UGS-related mechanical simulations. Full article

Capillary barrier covers (CBCs) have gained widespread application as engineered surface layers in landfill systems, agricultural water retention infrastructures, and slope protection designs due to their superior water storage capacity and lateral drainage characteristics. During the long-term service of CBCs, fine particles may enter into the coarse-grained layer, which affects the water storage capacity and even causes CBCs to fail. Therefore, this study investigated the influence of admixing different types of soils (into the coarse-grained layer) and their proportions on water storage capacity through laboratory soil column experiments. The results indicate the following: (1) A method is proposed to determine the failure of the capillary barrier by utilizing the variation pattern of volumetric water content (VWC) at the fine–coarse-grained layer interface. (2) An effective capillary barrier can only be formed if the saturated permeability coefficient of the coarse-grained layer is at least one order of magnitude greater than that of the fine-grained layer. (3) When the saturated hydraulic conductivity of the fine particles incorporated into the coarse-grained layer is less than 10⁻⁵ cm/s, the matric potential of the fine-grained layer consistently exhibits a CBC line type. When the saturated hydraulic conductivity of the fine particles is greater than 10⁻⁵ cm/s, the matric potential of the fine-grained layer shows a homogeneous line type at an incorporation ratio of 1:0.6. (4) When the particle size of the fine particles mixed into the coarse-grained layer (quartz sand, silt, and diatomite with admixture ratios of 1:0.1, 1:0.3, 1:0.6, and 1:1) is smaller than that of the particles in the fine-grained layer, the water storage capacity of CBCs is only affected by the proportion of fine particles added to the coarse-grained layer and is independent of the type of fine particle used. Full article

Quartz purification is a key driver of the silicon-based industrial sector. This study used typical vein quartz from Jiangxi Province, China as a raw material to systematically investigated the occurrence states of impurities and conducted an in-depth chemical purification study. The effects of various parameters on impurity removal via acid leaching were investigated. The results revealed distinct removal patterns: independent minerals were effectively removed with low-concentration acid; inclusion impurities were efficiently eliminated by optimizing temperature and acid concentration; and lattice impurities proved resistant to removal. The optimal acid-leaching conditions were identified as follows: 80 °C leaching temperature, mixed acid system of HF-HCl-H₂SO₄ (volume ratio 1:1:1), 7 wt% acid concentration, 6 h leaching time, and a 1:1 solid–liquid ratio. The removal efficiencies of Al, K, and Fe reached 77.0%, 87.5%, and 80.0%, respectively, and the product (the quartz particles after acid leaching) purity was elevated to 99.92%. Furthermore, this study clarified the influence of acid-leaching parameters on purifying high-aluminum low-iron quartz sand, providing a valuable theoretical basis and technical reference for the deep processing of similar quartz ores. Full article

The utilization of hydrocyclones dates back more than a century. As the key channel for multiphase flow, the inlet chamber exerts a notable influence on the separation efficiency of hydrocyclones. Conventional feed bodies mainly adopt straight lines as guidelines. During the transition of fluid from linear motion to circumferential motion, significant kinetic energy loss and particle misalignment are exhibited, resulting in relatively low classification accuracy of the hydrocyclone. Therefore, in this study, a hydrocyclone featuring a complex curved inlet chamber structure was designed, and numerical analysis was employed to examine the particle distribution and aggregation characteristics within both the inlet chamber and the hydrocyclone. Supplemented with RSM/VOF/TFM simulations and quartz sand experimental validation, this study compares the separation performance of the complex curved inlet with the conventional linear inlet. The results indicate the following: when particle sizes are small, particles are dispersed throughout the hydrocyclone and inlet chamber, exhibiting a disordered state, which leads to poor classification performance. As particle size increases, particles gradually form layers along the radial direction; larger particles tend to accumulate on the hydrocyclone wall. When the particle concentration is maintained within a specific range, it promotes the migration of fine particles toward the center, thereby reducing the likelihood of fine particles entering the outer vortex and allowing for more precise classification of fine particles. As the particle concentration increases, the cutting ability of the hydrocyclone progressively diminishes; when the concentration exceeds 20%, the maximum underflow recovery rate for particles smaller than 50 µm is only 60%, resulting in significant coarse overflow and a notable decrease in classification precision. Furthermore, as the inlet concentration increases, the dispersion index for 0.5 µm particles ranges from 0.6 to 1.6, for 4 µm particles from 0.6 to 1.4, and for 60 µm particles from 0.6 to 1. The decreasing dispersion index indicates an increasing classification force, which aids in the formation of a coarse particle layer on the wall. The conclusions and data obtained provide a theoretical foundation and empirical support for the design of innovative inlet chamber structures. Full article

In this study, four types of Fe₃O₄-based magnetic nanospheres were functionalized with distinct surface groups to examine how surface chemistry influences their co-transport with tetracycline (TC) in porous media. The functional groups investigated are carboxyl (−COOH), epoxy (−EPOXY), silanol (−SiOH), and amino (−NH₂). Particles bearing −COOH, −EPOXY, or −SiOH are negatively charged, facilitating their transport through porous media, whereas −NH₂-modified particles acquire a positive charge, leading to strong electrostatic attraction to the negatively charged TC and quartz sand, and consequently substantial retention with reduced mobility. Adsorption of TC onto Fe₃O₄-MNPs is predominantly chemisorptive, driven by ligand exchange and the formation of coordination complexes between the ionizable carboxyl and amino groups of TC and the surface hydroxyls of Fe₃O₄-MNPs. Additional contributions arise from electrostatic interactions, hydrogen bonding, hydrophobic effects, and cation–π interactions. Moreover, the carboxylate moiety of TC can coordinate to surface Fe centers via its oxygen atoms. Molecular dynamics simulations reveal a hierarchy of adsorption energies for TC on the differently modified surfaces: Fe₃O₄-NH₂ > Fe₃O₄-EPOXY > Fe₃O₄-COOH > Fe₃O₄-SiOH, consistent with experimental findings. The results underscore that tailoring the surface properties of engineered nanoparticles substantially modulates their environmental fate and interactions, offering insights into the potential ecological risks associated with these nanomaterials. Full article

This article presents the results of a comprehensive investigation into geopolymer composites synthesized from fly ash, incorporating ground asphalt derived from reclaimed road pavement and quartz sand. The primary objective of this study was to elucidate the influence of mixture composition on the mechanical, physical, and microstructural characteristics of the developed materials. The innovative aspect of this research lies in the integration of two distinct filler types—mineral (quartz sand) and organic-mineral (milled asphalt)—within a single geopolymer matrix, while preserving key performance parameters required for engineering applications, including compressive and flexural strength, density, water absorption, and abrasion resistance. The experimental methodology encompassed the characterization of the raw materials by X-ray diffraction (XRD), chemical composition analysis via X-ray fluorescence (XRF), and assessment of particle size distribution. Additionally, the produced geopolymer materials underwent density determination, compressive and flexural strength measurements, abrasion testing, and mass water absorption evaluation. The chemical composition was further examined using XRF, and the surface morphology of the specimens was analyzed by scanning electron microscopy (SEM). The findings demonstrate that the incorporation of quartz sand enhances the density and mechanical strength of the composites, whereas the addition of recycled asphalt, despite causing a modest reduction in mechanical performance at elevated dosages, augments water resistance. Moreover, ternary composite material provide an optimal compromise between mechanical strength and durability under humid conditions. Overall, the results substantiate the feasibility of utilizing asphalt waste for the fabrication of functional and sustainable geopolymer materials suitable for construction applications. Full article

In this work, a core mold which combines excellent high-temperature compressive properties and rapid water solubility was successfully fabricated by using polyvinyl alcohol (PVA) as the adhesive and quartz sands as reinforcing particles. The influence of the molecular weight and alcoholysis degree of PVA, the concentration of PVA and the size of the quartz sands on the compressive performance and water penetration rate of core molds was studied in detail. The results revealed that core molds which were prepared using PVA-4 (i.e., a degree of polymerization of 2400 and an alcoholysis degree of PVA of 88%) and 160–200 mesh quartz sands with a mass ratio of 1.2:10 possessed a 160 °C compressive strength of 7.4 MPa, a 160 °C compressive modulus of 179.3 MPa and 50 °C water penetration rate of 0.94 mm/s. Furthermore, a validation experiment was conducted to verify the efficacy of using the as-prepared core mold to fabricate a hollow composite part, which shows a promising application in industrial sectors. Full article

To address the challenges of low permeability, high gas adsorption, and a fragile structure in coalbed methane reservoirs, this study developed a high-strength composite proppant with an activated carbon skeleton via nitric acid pretreatment, silica–alumina sol coating, and calcination. Orthogonal experiments optimized the preparation conditions: 30–40 mesh activated carbon, Si/Al molar ratio of 4:1, calcination at 650 °C for 2 h. The resulting proppant exhibited an excellent performance: a single-particle compressive strength of 55.5 N, porosity of 33.2%, crushing rate of only 2.3% under 50 MPa closure pressure, and permeability 48.5% higher than quartz sand. In simulated acidic coalbed environments (pH 3–5), its acid corrosion rate was <2.8%, and it enhanced methane desorption by 16.2% compared to pure coal. Additionally, the proppant showed a superior transport performance in fracturing fluids, with better distribution uniformity in fractures than ceramsite, and its hydrophobic surface (contact angle 115.32°) improved fracturing fluid flowback efficiency. This proppant integrates high strength, good conductivity, gas desorption promotion, and corrosion resistance, offering a novel material solution for efficient coalbed methane extraction. Full article

To improve fracturing support efficiency of terrestrial shale oil reservoirs with uneven proppant placement, this study used complex mesh flat-plate simulations and ANSYS FLUENT (2020) simulations to test four sand addition processes. Proppants were 70/140 mesh quartz sand with a density of 2650 kg/m³ and 40/70 mesh ceramic particles with a density of 2000 kg/m³, and the carrier was hydroxypropyl guar gum fracturing fluid with a viscosity of 4.46–13.4 mPa·s at 25 °C. Alternating sand addition performed best: sand-laying efficiency reached 52 percent, 10 percentage points higher than continuous sand addition and 12 percentage points higher than mixed sand addition; sand embankment void area was 1400 cm², 18.3 percent lower than continuous sand addition; proppant entry into secondary cracks increased 23.8 percent compared with reverse sand addition; at branch crack Position 2, 1.3 m from the inlet and at a 90-degree angle, its equilibrium height was 210 mm and paving rate 0.131. This study fills gaps of no systematic multi-process comparison and insufficient quantification of crack geometry–sand parameter coupling in existing research; its novelty lies in the unified visualization comparison of four processes, revealing geometry–parameter coupling and integrating experiment simulation; the optimal scheme also improves fracture support efficiency 21.5 percent compared with conventional continuous sand addition. Full article

This study focuses on the clastic reservoir in the first member of Yaojia Formation within Qijia-Gulong Sag, Songliao Basin. The results indicate that the reservoir in the study area develops within a shallow-water delta sedimentary system. The dominant sedimentary microfacies comprise underwater distributary channels, mouth bars, and sheet sands. Among these, the underwater distributary channel microfacies exhibits primary porosity ranging from 15.97% to 17.71%, showing the optimal reservoir quality, whereas the sheet sand microfacies has a porosity of only 7.45% to 12.08%, indicating inferior physical properties. During diagenesis, compaction notably decreases primary porosity via particle rearrangement and elastic deformation, while calcite cementation and quartz overgrowth further occlude pore throats. Although dissolution can generate secondary porosity (locally up to 40%), the precipitation of clay minerals tends to block pore throats, leading to “ineffective porosity” (permeability generally < 5 mD) and overall low-porosity and low-permeability characteristics. Carbon–oxygen isotope analysis reveals a deficiency in organic acid supply in the study area, restricting the intensity of dissolution alteration. Reservoir quality evolution is dominantly governed by the combined controls of sedimentary microfacies and diagenesis. This study emphasizes that, within shallow-water delta sedimentary settings, the material composition of sedimentary microfacies and the dynamic equilibrium of diagenetic processes jointly govern reservoir property variations. This insight provides critical theoretical support for understanding diagenetic evolution mechanisms in clastic reservoirs and enabling precise prediction of high-quality reservoir distribution. Full article

This study investigates the development of a fully rubberized fine-aggregate engineered geopolymer composite (R-EGC) by replacing quartz sand with waste rubber particles (RPs). The influence of the rubber aggregate-to-binder mass ratio (A/B) on the performance of the R-EGC was systematically examined from both macroscopic and microscopic perspectives. Quantitative analysis of crack width and number was conducted using binarized image-processing techniques to elucidate the crack propagation patterns. Moreover, scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were employed to analyze the interfacial transition zone (ITZ) between the rubber aggregates and the geopolymer matrix under varying A/B ratios, aiming to explore the underlying failure mechanisms of the R-EGC. The research results indicated that the flowability of the R-EGC decreased gradually with increasing A/B ratio. The flowability of R-0.1 was 73.5%, outperforming R-0.2 and R-0.3 (66% and 65%, respectively). R-0.1 achieved the highest compressive strength of 35.3 MPa (compared to 31.2 MPa and 28.4 MPa for R-0.2 and R-0.3, respectively). R-0.3 demonstrated the most effective crack-control capability, with a tensile strength of 3.96 MPa (representing increases of 11.9% and 3.7% compared to R-0.1 and R-0.2, respectively) and the smallest crack width of 104 μm (indicating reductions of 20.6% and 43.5% compared to R-0.1 and R-0.2, respectively). R-0.2 exhibited the best ductility, with an ultimate tensile strain of 8.33%. Microstructural tests revealed that the interfacial transition zone (ITZ) widths for R-0.1, R-0.2, and R-0.3 were 2.47 μm, 4.53 μm, and 1.09 μm, respectively. An appropriate increase in the ITZ width was found to be beneficial for enhancing tensile ductility, but it compromised the crack-control ability of the R-EGC, thereby reducing its durability. Overall, this study clarifies the fundamental influence of the A/B ratio on the mechanical performance of the R-EGC. The findings provide valuable insights for future research in this field. Full article

Porous artificial reef materials made of cement used in the offshore area can repair and improve the ecological environment and enrich fishery resources. In this study, quartz sand was used as the aggregate, high-alumina cement as the cementing agent, and crushed particles of waste tires as the modifier to prepare porous cement–polymer composites. Through orthogonal tests, the effects of the aggregate particle size, the ratio of aggregate to cement, the rubber particle size, and the rubber ratio on the strength and permeability of the porous cement–polymer composites were studied. The significant degrees of different influencing factors were analyzed, and an appropriate configuration scheme for the porous cement–polymer composites was proposed. The experimental results show that the quantity of rubber particles added and the particle size of the rubber particles have a relatively large impact on the properties of the porous cement–polymer composites. Through response surface tests, the interactive effects of various factors in the porous cement–polymer composites on the compressive strength and permeability of the material were verified. The microstructure of the porous cement–polymer composites was observed by SEM. The differences in the microstructure and internal structure between the specimens with a low rubber content and large rubber particle size and those with a high rubber content and small rubber particle size were analyzed, and the influence mechanism of the differences in the microstructure and internal structure on the strength and permeability was proposed. Full article

Coral sand is characterized by unique particle morphology and pore structure, which result in pronounced dilatancy and a high internal friction angle during shear. The dilatancy angle is a critical parameter for finite element analyses of sand foundation bearing capacity; the inappropriate selection of this parameter can lead to significant computational errors. In this research, a series of consolidated drained triaxial tests were conducted on coral sand samples from the South China Sea to investigate the dilatancy behavior and its effect on shear strength parameters. A dilatancy equation for coral sand was proposed, incorporating the dilatancy index, relative density, and mean effective stress. The results indicate the following: (1) Within the confining pressure range of 25–400 kPa, the stress–strain curves exhibit varying degrees of strain softening. When the effective confining pressure reaches 400 kPa, the dilatant behavior is nearly suppressed, resulting in a transition from dilatancy to contraction; (2) The peak internal friction angle decreases significantly with increasing effective confining pressure. However, the sensitivity to confining pressure varies for samples with different relative densities (Dr = 30–90%), with denser samples showing a more rapid reduction in peak friction angle; (3) At a confining pressure of 25 kPa, the maximum dilatancy angle of coral sand samples reaches 44.2°, significantly exceeding the typical range observed in terrestrial quartz sands. This difference may be attributed to the irregular and angular characteristics of the coral sand particles; (4) Based on Bolton’s dilatancy theory, a dilatancy equation applicable to coral sand was developed, demonstrating a strong linear relationship among the dilatancy index (I_R), relative density (Dr), and peak mean effective stress (p′_f). These findings provide valuable guidance for the selection of strength parameters for engineering applications involving coral sand. Full article

A lime–sand island–reef formation has a dual structure consisting of an overlying loose or weakly consolidated coral sand (CS) layer and an underlying reef limestone layer. The coral sand layer is the sole carrier of the underground freshwater lens in the lime–sand island–reef, and it differs in terms of its hydraulic properties from common terrigenous quartz sand (QS). This study investigated the mechanism of freshwater lens formation, dominated by solute dispersion, combining multi-scale experiments and numerical simulations (GMS) to reveal the control mechanisms behind the dispersion properties of coral sand and their role in freshwater lens formation. Firstly, the dispersion test and microscopic characterization revealed the key differences in coral sand in terms of its roundness, roughness, particle charge, and surface hydrophilicity. Accordingly, a hierarchical conversion model for the coral sand–quartz sand coefficient of dispersion (COD) was established (R² > 0.99). Further, combining this with numerical simulation in GMS revealed that the response pattern of the coefficient of dispersion to key parameters of freshwater lens development is as follows: freshwater appearance time > steady-state freshwater body thickness > steady-state freshwater reserve > lens stabilization time. These results clarify the development mechanism and formation process behind freshwater lenses on island reefs, from the micro to the macro scale, and provide a scientific basis for optimizing the protection of freshwater resources in coral islands and guiding the construction of artificial islands. Full article