Quartz Research Articles

The Development of a Novel Nitrate Portable Measurement System Based on a UV Paired Diode-Photodiode.

Nitrates can cause severe ecological imbalances in aquatic ecosystems, with considerable consequences for human health. Therefore, monitoring this inorganic form of nitrogen is essential for any water quality management structure. This research was conducted to develop a novel Nitrate Portable Measurement System (NPMS) to monitor nitrate concentrations in water samples. NPMS is a reagent-free ultraviolet system developed using low-cost electronic components. Its operation principle is based on the Beer-Lambert law for measuring nitrate concentrations in water samples through light absorption in the spectral range of 295-315 nm. The system is equipped with a ready-to-use ultraviolet sensor, light emission diode (LED), op-amp, microcontroller, liquid crystal display, quartz cuvette, temperature sensor, and battery. All the components are assembled in a 3D-printed enclosure box, which allows a very compact self-contained equipment with high portability, enabling field and near-real-time measurements. The proposed methodology and the developed instrument were used to analyze multiple nitrate standard solutions. The performance was evaluated in comparison to the Nicolet Evolution 300, a classical UV-Vis spectrophotometer. The results demonstrate a strong correlation between the retrieved measurements by both instruments within the investigated spectral band and for concentrations above 5 mg NO3-/L.

Temperature stability and enhanced transport properties by surface modifications of silica nanoparticle tracers for geo-reservoir exploration

Tracer tests are an important tool for characterizing and monitoring subsurface reservoir properties. However, they are limited both because of the tracer molecules constraining factors such as irreversible adsorption, retention, and degradations, i.e. interaction processes of fluorophore molecule with surrounding media resulting in a large variation in transport properties. Elaborate tests utilizing more than one tracer to distinguish time or location of injection are complex and interpretation is ambiguous because each tracer interacts differently. In this study, we present an approach to increase tracer stability and enhance the transport uniformity of different tracers, thus making tests utilizing multiple tracers simpler and more feasible. We present this concept of tracer multiplicity by encapsulating an anionic, cationic or amphoteric fluorophore inside mesoporous silica nanoparticle carriers coated with a protective titania layer. Upon encapsulation, increased thermal resistance and drastically lowered sorption affinity towards quartz sand was detected in batch and flow-through experiments. An additional advantage of the presented nanoparticle tracers over molecular tracers is their modularity, which is demonstrated by surface modifications and application of additives that greatly reduce sorption and increase recovery rates in the flow experiments. With the here presented concept of tracer multiplicity, we introduce a new approach for colloidal tracer design that has the potential to expand and enhance measurable parameters, measurement accuracy and simplicity of analysis.

Experimental and theoretical investigations into the surface chemical properties and separation of serpentine from quartz using xanthomonas campestris as a selective flocculant

Separation of fine serpentine (SPT) from quartz (QZ) both of d80 close to 20 µm using an eco-friendly microbial exo-polysaccharide, xanthomonas campestris (XCT), as a selective flocculant for SPT was conducted experimentally and substantiated theoretically. The adsorption of XCT onto SPT was observed to decrease with increase in pH, whereas that of QZ was nearly nil beyond pH 2.1. Zeta potential of SPT in presence of XCT decreased with increase in pH further attesting to the adsorption and anionicity of XCT. The FTIR studies confirmed the interaction of XCT with SPT in presence of sodium hexametaphosphate. The nature of intermolecular interactions present in complexes formed on SPT surface was revealed by quantum theory of atoms in molecules to be non-covalent. The electron density difference plot conducted on formed complexes indicated that electrons drifted from XCT to the surface of SPT. Selective flocculation SPT-QZ (1:1) mixture conducted at pH 6 and pH 7.5 in presence of 4 mg/L and 2 mg/L of sodium hexametaphosphate coupled with 100 mg/L of XCT yielded separation efficiency and selectivity ratio of 96.5 % and 71.2, respectively, after three desliming stages. Therefore, XCT is a potential selective flocculant for serpentine.

Recycling of magnesium oxychloride cement: Application of crushed MOC waste as a filler in the next-generation MOC composites

This study deals with magnesium oxychloride- (MOC-) based construction composites in which, a filler formed from end-of-life MOC-based composite recyclate is used as a partial or full replacement of standard quartz sand filler. The developed composites pose as a highly environmentally sustainable alternative to Portland cement (PC), which has dominated the global construction sector, largely due to its unique properties and adaptability to various conditions. As the PC industry is a major contributor to greenhouse gas emissions, it is ultimately necessary to find a suitable alternative. In our study, we demonstrated that the proposed composite, even with a very high content of the MOC-based recyclate performs well concerning its mechanical parameters evidenced by compressive strength exceeding 64 MPa. The developed composites also yield a low water absorption of about 3.3 wt% and even when exposed to the harsh environment of 95 % RH for 7 days, their softening coefficient reaches values higher than 85 %. The acquired material parameters of the prepared composites make them suitable for application in the production of construction materials with high mechanical strength and acceptable resistance to the action of moisture. The approach which was taken, where MOC-based construction waste can be fully reutilized in the next generation of MOC composites as a filler represents a very promising route for the development of waste-free and CO2-neutral technology.

Impact of diatomit on the transport behavior of unmodified and carboxyl-modified nanoplastics in saturated porous media

Due to the extensive use of plastic products and unreasonable disposal, nanoplastics contamination has become one of the important environmental problems that mankind must face. The composition and structure of porous media can determine the complexity and diversity of the transport behavior of nanoplastics. In this study, the influence of diatomite (DIA) on the nanoplastics transport in porous media is investigated by column experiments combined with XDLVO interaction energy and transport model. Results suggest that the recovery rates of unmodified polystyrene nanoparticles (PSNPs) and carboxyl-modified polystyrene nanoparticles (PSNPs-COOH) in the porous media containing DIA decreases compared with that in the pure quartz sand (QS), and the BTCs showed a “blocking” pattern. The presence of DIA inhibits the transport of both PSNPs and PSNPs-COOH, but the inhibition is not significant. This may be because the presence of DIA provides more favorable deposition sites for PSNPs and PSNPs-COOH to some extent. However, since DIA itself carries a certain negative charge, this can only play a role in compressing the double electric layer for PSNPs and PSNPs-COOH with the same negative charge, and cannot destabilize them. The migration capacity of PSNPs and PSNPs-COOH is strongest in the DIA-QS porous media at pH = 7, and is weak at pH = 9 and pH = 5. The inhibition of migration at pH = 9 can be attributed to the dissolution of the DIA surface under alkaline conditions and the formation of pore and defect structures, which provide more deposition sites for PSNPs and PSNPs-COOH. The presence of humic acid (HA) leads to an increase in the mobility of PSNPs and PSNPs-COOH, and the mobility is enhanced with HA concentration. The mobility of PSNPs and PSNPs-COOH in DIA-QS decreases with ionic valence and ionic strength, and PSNPs-COOH is more significantly inhibited compared to PSNPs.

Sensing performance of Schiff base-calix[4]arene including amide units for detection of pharmaceutically active compounds on QCM sensor system

This study aimed to investigate the sensing performance of a Quartz Crystal Microbalance (QCM) sensor coated with a calix[4]arene derivative (calixarene phenol amide, CPhA), containing both Schiff base and amide groups against various pharmaceutically active compounds (PhACs) such as ibuprofen, diphenhydramine, naproxen, and ascorbic acid in aqueous media. CPhA was successfully coated on the QCM crystal surface, and its surface properties were studied using Atomic Force Microscopy (AFM) and contact angle measurements. Sensing studies showed that the CPhA-coated QCM sensor detected more PhACs than the compound 4 (unfunctionalized derivative)-coated sensor. The highest frequency variation and binding ratio values were achieved with the QCM sensor with a relatively low coating amount. The CPhA-coated QCM sensor achieved higher adsorption capacity and was significantly more sensitive to all PhACs than the compound 4-coated one. The fabricated sensor showed remarkable reproducibility for all PhACs except naproxen (NAP). The fabricated sensor exhibited a remarkable sensing performance for detecting PhACs, which is promising for developing novel calix[4]arene-coated QCM sensors for PhACs.

Photolytic Mass Loss of Humic Substances Measured with a Quartz Crystal Microbalance.

Laboratory studies have shown that photolytic mass loss can be a significant sink for secondary organic aerosol (SOA). Here, we use a quartz crystal microbalance to measure mass loss of Suwannee River Humic Acid (SRHA) and Suwannee River Fulvic Acid (SRFA), surrogates for SOA, exposed to 254, 300, and 405 nm radiation over the course of 24 h. We find that the photolytic mass loss rates of these materials are comparable to those for laboratory-generated limonene and toluene SOA material from the study of Baboomian et al, ACS Earth Space Chem. 2020, 4, 1078. Scaling our results to ambient conditions, we estimate that humic substances in aerosols can lose as much as 8% by mass in the first day of exposure in the atmosphere, equivalent to 0.025% of J NO2 , the photolysis rate of nitrogen dioxide. By using zero air instead of nitrogen, we also find that the presence of oxygen accelerates the photolytic mass loss rate by a factor of 2 to 4 at all wavelengths suggesting a potential role for reactive oxygen species. UV photolysis of an aqueous SRFA solution demonstrated both photobleaching at UV wavelengths and photoenhancement at visible wavelengths. Ultrahigh-resolution mass spectrometric analysis showed that condensed-phase SRFA photolysis led to decreased intensity in the 100-300 m/z range while aqueous SRFA photolysis resulted in an increase in intensity in the same range. This work reaffirms that photolytic mass loss is a potentially significant sink for SOA, but only on the time scale of a day or two and demonstrates that SRHA and SRFA are suitable surrogates for atmospheric SOA with respect to photolytic mass loss.

Electrochemical and surface characterisation of poly(3,4-ethylenedioxythiophene) dodecylbenzenesulfonate layers

Poly(3,4-ethylenedioxythiophene) (PEDOT) films were electrochemically synthesised with sodium dodecylbenzenesulfonate (DBS) and chloride acting as dopant anions within the polymer matrix. Upon redox switching of the PEDOT/DBS film between conducting and non-conducting states, the DBS anion remained within the polymer and cation insertion and expulsion occurred, as confirmed by Electrochemical Quartz Crystal Microbalance (EQCM) measurements. Electrolytes composed of alkali metal cations of varying masses (Li+, Na+, K+) were employed to investigate the cation insertion/expulsion processes, thereby resulting in varying mass changes being observed upon film redox switching. The charging and discharging of bulky anion doped polymer films presented higher capacitance upon charging and lower capacitance when discharging, which is expected during doping and de-doping as confirmed by AC impedance. In this work, the main results obtained by chemical-physical characterisation are presented and critically discussed, with regard to the possible use of a viable conducting polymer as a drug delivery vehicle.

Fully recycled engineered geopolymer composite: Mechanical properties and sustainability assessment

Combining the two advantages of mitigation of dependence on cement and natural sand resources and recycling waste concrete material, the utilization of recycled concrete powder (RCP) and recycled fine sand (RFS) to produce geopolymer concrete is of great value. However, the insufficient compressive strength and inherent brittleness of the existing RCP or RFS geopolymer concrete hampered its application. This paper aims to develop a high-performance engineered geopolymer composite (EGC) by maximizing the recycle amount of RCP and RFS. The effects of RCP and RFS on the physical, mechanical, and microscopic properties of EGC were investigated. The results indicated that, the less reactivity of RCP decreased the amount of gel products and compromised the strength development, while favored the multi-cracking behavior and the robust ductility. RFS showed a stronger interfacial bond with paste than quartz sand, compensating the degradation of strength driven by RCP and marginally affecting the tensile strain capacity. The developed EGC incorporating 50% RCP and 100% RFS possessed an 84 MPa compressive strength, 7.4 MPa tensile strength, and 8.1% tensile strain, which are at the highest level among the existing RCP or RFS geopolymer concretes. The main products included the coexistence of calcium aluminosilicate hydrate and alkali aluminosilicate (C(N)-A-S-H) gel and layered double hydroxide (LDH). The energy- and carbon-reduction were 16% and 57%, respectively, compared to the M45-ECC.The current findings prove the feasibility of utilizing high amounts of recycled materials to produce high value-added concrete.

Electron paramagnetic resonance signature of rock-forming blue quartz from the Albești (Romania) granite

Electron paramagnetic resonance signature of rock-forming blue quartz from the Albești (Romania) granite

Injection 3D Printing of Doubly Curved Ceramic Shells in Non-Synthetic Particle Suspensions.

This paper examines the application of non-synthetic particle suspensions as a support medium for the additive manufacturing of complex doubly curved ceramic shells with overhangs between 0° and 90° using clay paste. In this method, the build-up material is injected within a constant volume of air-permeable particle suspension. As the used clay paste does not solidify right after injection, the suspension operates like a support medium and enables various print path strategies. Different non-synthetic suspension mixtures, including solid and flexible components such as quartz sand, refractory clay, various types of wood shavings, and cotton flocks, were evaluated for their ability to securely hold the injected material while allowing drying of the water-based clay body and its shrinkage. The balance between grain composition, added water, and the compressibility of the mixture during printing and drying played a pivotal role in the particle suspension design and assessment. Furthermore, the moisture absorption of the particle suspension and the structural integrity of the layer bond of the fired ceramics were also assessed. The examined additive manufacturing process not only enables the production of meso-scale doubly curved ceramic shells with average overhang of 56° but also introduces a new practice for designing specialized surfaces and constructions.

Tracking the movement of quartz sand particles with neural networks

Tracking the movement of particles is of paramount significance for studying the impact of particle breakage on the macroscopic mechanical behaviour of granular materials and remains a persistent challenge to date. This paper presents a novel particle tracking method that integrates Pointon and PointNetLK networks, enabling an accurate tracking of both intact and broken Leighton Buzzard sand (LBS) particles. Initially, morphological information of LBS particles was extracted from X-ray micro-tomography (CT) data collected from a miniature triaxial test. Various image processing techniques were applied to the raw CT images to achieve a realistic three-dimensional (3D) reconstruction. Subsequently, particle point cloud data was processed through sampling, Gaussian noise injection, and grouping for training and testing the Poynton and PointNetLK networks. Next, the correspondences among particles across different scans were established by PointConv, and the transformation matrix between two mutually matched particles was predicted using PointNetLK. Finally, an examination of the changes in the spatial distribution and morphological parameters of both tracked and untracked particles throughout the shearing process was conducted and followed by an analysis of particle kinematics.

Molecular Simulations Study of the Ionic Adsorption on Oscillating Carbon Electrodes

Molecular dynamics simulations are a method of choice to study, at microscopic scales, the adsorption of electrolyte ions onto the electrodes of capacitive storage systems such as supercapacitors1.Here, we use all-atom molecular dynamics simulations to model a pure ionic liquid electrolyte ([EMIM][TFSI], 1-ethyl-3-methylimidazolium trifluoromethanesulfonylimide) in contact with graphite electrodes (Figure: Supercapacitor composed of graphite electrodes (in light blue) in contact with a pure ionic liquid electrolyte ([EMIM][TFSI], atoms colored according to the atom type. The arrows illustrate the oscillations of electrodes used to probe the influence of such a motion on the interfacial liquid.)When applying a potential difference between the two carbon electrodes, a migration of counter ions is observed, ultimately leading to a compensation of the charges carried by the electrode atoms. The adsorption dynamics depend on several parameters (electrostatic interactions, coordination number, viscosity of the electrolyte, size of the ions etc.) and influence the power of these capacitive systems2. In order to improve the performance of supercapacitors, it is then important to describe and understand interfacial properties at a molecular scale.Experimentally, an Electrochemical Quartz Crystal Microbalance (EQCM) can be used to study ion flow on top of the electrode. The frequency variations recorded by the EQCM are linked to variations in the mass adsorbed on the quartz surface, thus making it possible to study the dynamics of ion adsorption during the charge of a supercapacitor.3 However, variations in quartz frequency can influence the stability of the electrode-electrolyte interface, thus modifying ionic interactions and adsorption dynamics at the electrode surface4.Here, thanks to molecular simulations, we have access to the adsorption rate of ions, to their re-orientation, to the variation of charge of the electrode atoms during adsorption etc. This allows us to study in detail the mechanisms governing the electrolyte-electrode interface during the charging of supercapacitors as part of EQCM. And study the extent to which perturbations caused by quartz oscillations in the ionic liquid affect electrode-electrolyte interfacial properties. References 1 K. Xu, H. Shao, Z. Lin, C. Merlet, G. Feng, et al.. ENERGY & ENVIRONMENTAL MATERIALS, 3, 235-246 (2020) 2C. Péan, B. Rotenberg, P. Simon, M. Salanne, ELECTROCHIM. ACTA, 206, 504-512 (2016) 3Y-C. Wu, J. Ye, G. Jiang, K. Ni, N. Shu, P-L. Taberna, Y. Zhu, P. Simon, ANGEW. CHEM. INT. ED., 60, 13317-13322 (2021) 4Nikolai V. Priezjev, MICROFLUIDICS AND NANOFLUIDICS, 14, 225-233 (2013) Figure 1

Kinetics of Charge Reversal in the Double Layer Studied with an Electrochemical Quartz Crystal Microbalance (EQCM-D)

Normal pulse voltammetry on inert electrolytes was combined with a new electrochemical quartz crystal microbalance (EQCM) with millisecond time resolution, which allows to probe the kinetics of charge reversal in the diffuse double layer (DL) after a step in electrode potential. The QCM responds to the charge reversal because the local viscosity-density product depends on the type and the concentration of the ions. The time resolution was improved to 1 ms using multifrequency lockin amplification, which allows to study kinetic effects in dynamic electrochemistry, which were previously not accessible with gravimetry. The noise was lowered to less than 10 mHz by modulating the electrode potential and averaging Δf and ΔΓ over many modulation cycles.The overtone scaling was found to be the same as in gravimetry (-Δf/n » const. and ΔΓ/n < -Δf/n with n the overtone order), which, however, is not caused by a deposition of a rigid film in the Sauerbrey sense. A Sauerbrey-type QCM response is also caused by changes in Newtonian viscosity inside a layer with a thickness far below the penetration depth of the shear wave (such as the double layer).The frequency response in the electrolytes studied correlated well with the viscosity B-coefficients of the respective ions as employed in the Dole-Jones equation. The time constants inferred from gravimetry were similar to the time constants (the RC-times) from electrochemical impedance spectroscopy (EIS). There were small differences, which presumably go back to slow rearrangements inside the Helmholtz layer, which are not seen in EIS.The QCM response to double layer recharging in inert electrolytes is of great importance for the interpretation of QCM results on processes involving Faradayic charge transfer. Such a response is omnipresent as a background and might be misinterpreted as a gravimetric signal.[1] References[1] Leppin, C.; Peschel, A.; Meyer, F. S.; Langhoff, A.; Johannsmann, D. Kinetics of Viscoelasticity in the Electric Double Layer Following Steps in the Electrode Potential Studied by a Fast Electrochemical Quartz Crystal Microbalance (EQCM). Analyst 2021, 146 (7), 2160–2171. Caption: Shifts in frequency and bandwidth in response to potential steps (left). The gravimetric signal followed the steps with a delay of a few milliseconds. The amplitude and the response time depend on cation type (right). The counter ion was NO3 -. Both the amplitude and the response time correlate well with the viscosity B-coefficient. Figure 1

Quartz luminescence sensitivity enhanced by residence time in the critical zone

The emerging use of quartz luminescence properties to characterize Earth-surface processes shows promise, with optically stimulated luminescence (OSL) sensitivity proposed as a valuable tool for provenance or sediment history tracing. However, the geologic processes that lead to quartz sensitization remain unclear. Here we study the impact of source rock and surface processes on the luminescence properties of quartz sand from bedrock and modern and Late Pleistocene alluvium generated from a mountainous catchment in northern Utah, USA. Continuous wave and linear modulated OSL are used to characterize the luminescence sensitivity and intensity of the fast-decay component. We compare the OSL sensitivity with sand-grain provenance and with proxies for surface processes such as topographic metrics, cosmogenic 10Be-derived erosion rates, chemical weathering indices, and magnetic susceptibility. Late Pleistocene sediment has low OSL sensitivity and a weak fast-decay component, similar to bedrock samples from the source area. In contrast, modern alluvium is dominated by the fast-decay component and has higher and more variable OSL sensitivity, with no clear relationship to upstream bedrock source. There is, however, an inverse relationship between OSL sensitivity and catchment-averaged erosion rates and a positive relationship with chemical weathering indices and magnetic susceptibility. These metrics suggest that the modern alluvium has experienced increased residence time in the shallow critical zone compared to the Late Pleistocene sediments. We suggest that changes in hillslope processes between the effectively wetter, cooler Pleistocene and the dryer, warmer conditions of the Holocene enhanced the luminescence properties. The results suggest that climatic controls on rates and processes of chemical and mechanical weathering and sediment transport and residence within the critical zone are encoded in the luminescence properties of quartz sand.

Tracking quartz and zircon provenance in sedimentary rocks using Ti distributions: Unlocking the volcanic-plutonic connection in old igneous systems

Although the relationship between silicic volcanic and plutonic rocks has been extensively studied, it remains controversial whether most plutons have volcanic counterparts and how the volcanic-to-plutonic ratio has evolved through time. This stems primarily from the scarcity of geologic examples with both volcanic and plutonic counterparts, especially in ancient terranes where volcanic deposits have likely been eroded. Here, we introduce a novel approach to identify remnant volcanic crystals in proximal siliciclastic/detrital rock formations. As most erupted crystals stop their growth before reaching the solidus, in contrast to plutonic crystals, the distribution of Ti (a proxy for temperature of crystallisation and/or magma evolution) in (weathering-resistant) quartz and zircon can help in identifying volcanic crystals in sedimentary rocks derived from supracrustal sources that have been completely eroded. Laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) analyses of quartz and zircon from volcanic and plutonic units that are known to be spatially and temporally related (from Southern Rocky Mountain Volcanic Field, Colorado, and Taupo Volcanic Zone, New Zealand) reveal that volcanic crystals have generally distinct distributions of, and on average higher Ti contents than, plutonic crystals. To further develop and test this methodology, we analysed samples from the 1.075 Ga Pikes Peak granite (CO, USA) and from the associated series of intra-granite sedimentary dikes that form part of the Cryogenian Period Tava sandstone. Blue band cathodoluminescence (CL) images can be used as a proxy for Ti-in-quartz. Our CL-screening method provides a statistically representative distribution of Ti contents in quartz crystals from individual thin sections. The Tava sandstone contains a higher concentration of high-Ti (and hence high-temperature) quartz and zircon grains than the average Pikes Peak batholith, interpreted as grains eroded from a no longer exposed, volcanic counterpart of the Pikes Peak magmatic system. Our study illustrates a means to test whether magmatic reservoirs that are now represented by crystallised ancient plutons once fed volcanic eruptions, and identifies a strategy for reconstructing volcanic-plutonic relationships, even when parts of the geological association have been eroded.

Flexural and fracture characterization of UHPGC notched beam with various glass sand replacement ratios and steel fiber contents

The preparation process of quartz sand (QS) can cause serious environmental pollution, which is particularly important to find a new replacement material for QS in cement-based construction materials. In this study, an economical and environmentally friendly ultra-high performance glass sand concrete (UHPGC) was prepared by partially replacing QS in conventional ultra-high performance concrete (UHPC) with glass sand (GS) ground from waste glass. The effects of material composition characteristics including water-binder ratio (W/B), GS replacement ratio, and steel fiber content on the flexural and fracture characteristics of UHPGC notched beams were investigated based on response surface method (RSM) and acoustic emission (AE) monitoring. The results indicate that the GS replacement rate presents almost no effect on the tensile strength and flexural toughness of the specimens while reducing the water-binder ratio or increasing the steel fiber content can significantly improve the flexural tensile strength of UHPGC notched beams. UHPGC notched beams show the best performance when the W/B is 0.17, the steel fiber content is 3 %, and the GS replacement rate is 50 %. By analyzing and comparing the AE parameters and fracture modes, the discrepancies in flexural and fracture properties of UHPGC notched beams with variable material composition characteristics can be elucidated. Among them, the low water-binder ratio or high steel fiber content has a significant effect on the fracture characteristics and fracture process of the specimens, while the GS replacement rate exhibits negligible effect.

Flexural performance of reinforced concrete beams repaired with BFRP grid-TSUHDC

Due to the influence of time, load, and external environmental factors, many reinforced concrete beams have been damaged and require repair. Tailings are waste generated during mineral production, resulting in substantial environmental pollution and economic losses due to the excessive generation of tailings and low comprehensive utilization. In the UHDC, tailings replaced quartz sand, while BFRP grids itself is an environmentally friendly material. Two repair methods were evaluated in this study, Tailings Sand Ultra-High Ductile Concrete (TSUHDC) and Basalt Fiber Reinforced Polymer (BFRP) grid-TSUHDC, grounded in the principles of green and sustainable development. Five reinforced concrete beam specimens were designed and fabricated for bending performance tests and finite element simulations. The effects of different repair methods and levels of damage on the flexural performance of reinforced concrete beams were investigated. The results reveal that, compared to untreated reinforced concrete beams, both TSUHDC and BFRP grid-TSUHDC repair methods enhanced bending load-bearing capacity. However, the stiffness of specimens repaired with TSUHDC decreased when subjected to 80 % of the pre-applied failure load. When the pre-applied failure load is less than 80 %, the recommended repair approach is the use of TSUHDC for repair. For cases where the pre-applied failure load exceeds 80 %, BFRP grid-TSUHDC is the preferable option. The flexural bearing capacity formula for this type of repair method was derived by improving existing formulas, yielding prediction results in close alignment with the experimental results.

Prediction and analysis of dominant factors influencing moisture content during vacuum screening based on machine learning

The study of the dominant factors influencing moisture content is essential for investigating vacuum filtration mechanisms. In view of the present situation where there is insufficient experimental data and the dominant factors influencing the moisture content of a filter cake have not been identified, in this study a vacuum filtration apparatus was designed and constructed. Quartz sand particles were used as the filtration material. 300 datasets of moisture contents of a filter cake were obtained under different experimental conditions. Multiple Linear Regression, artificial neural network, decision tree, random forest, and extreme gradient boosting were used to establish a prediction model for moisture content during vacuum screening. By comprehensively analyzing the feature importance rankings and the effects of positive and negative correlations, the dominant factors influencing the moisture content of the filter cake during vacuum screening were the particle ratio, screen mesh, and airflow rate. This finding not only provides a scientific basis for the optimization of vacuum screening technology but also points the way for improving screening efficiency in practical applications. It is of significant importance for deepening the understanding of the vacuum screening mechanism and promoting its extensive application.

Application of the EBSD Technique in the Study of Porosity and Permeability in Deformation Bands in Sandstone.

Deformation bands are common constituents of porous clastic fluid reservoirs. Various techniques have been used to study deformation band structure and the associated changes in porosity and permeability. However, the use of electron backscatter diffraction technique is limited. Thus, more information is needed regarding the crystallographic relationships between detrital crystals, which can significantly impact reservoir rock quality. We employ microscopic and microstructural investigation techniques to analyze the influence of cataclastic deformation bands on pore space. Porosity measurements of the Cretaceous Ilhas Group sandstone in NE Brazil, obtained through computerized microtomography, indicate that the undeformed domains exhibit a total porosity of up to 13%. In contrast, this porosity is slightly over 1% in the deformation bands. Scanning electron microscopy analyses revealed the presence of grain fragmentation and dissolution microstructures, along with cement-filling pre-existing pores. The electron backscatter diffraction analyses indicated extensive grain fragmentation and minimal contribution from intracrystalline plasticity as a deformation mechanism. However, the c axes of quartz crystals roughly align parallel to the orientation of the deformation band. In summary, we have confirmed and quantified the internal changes in a deformation band cluster, with grain size reduction and associated compaction as the main mechanism supported by quartz cementation.