Hydrate Compounds Research Articles

Basic properties of foamconcrete on quartzcement binder

Subject of research: the article considers foamconcrete on quartz cement binder, the mass introduction of quartz raw materials in construction can be considered practically achievable and economically profitable.
 Purpose of research: the technology of foam concrete on quartz-cement binder is proposed by introducing an ultrafine filler (nanomodifier) from activated quartz waste into the binder, reduces cement consumption by 10 % and improves its physical and mechanical properties.
 Methods and objects of research: the nanomodifier was obtained with mechanical and mechanohydraulic activation, the proposed filler activation technologies will improve the structure of cement stone forming foamconcrete pore-forming partitions by increasing the packing density and chemical activity of nanoscale particles in the processes of hydrate compounds phase formation.
 Main results of research: the proposed technology of heat-insulating foamconcrete on quartzcement binder allows you to create a pore structure with a diameter of 52 microns at a density of 500 kg/m3 foamconcrete samples and a total porosity of 6575 %, and will also increase the strength characteristics of foamconcrete to 7.713.8 % due to discrete reinforcement with quartz waste (nanomodifier) of pore-forming partitions.

GEP tree-based computational AI approach to evaluate unconfined compression strength characteristics of Fly ash treated alkali contaminated soils

The structural failures induced by alkali-contamination of soils are well established by earlier researchers. In the present study, the effect of alkali concentration (2 M and 4 M) and duration of curing on the unconfined compressive strength (UCS) of two types of soils (Kaolin and BC soil) were evaluated. Further, the effect of fly ash (FA) addition (10%, 15%, and 20%) on the UCS of alkali-contaminated soils was also determined. The results revealed that alkali contamination resulted in reducing UCS (by 36% and 46%), observed for kaolin and BC soil, respectively. The addition of FA has resulted in a linear increase in UCS of both soils. The optimum content was noted at 15%, attributed to the pozzolanic reaction initiated by alkali and subsequent gain of UCS with the formation of calcium (with FA addition) based hydration compounds. In addition, three attributes, i.e., FA content, curing period, and alkali concentration, have been used to develop GEP tree-based models to furnish simple prediction equations for calculating the UCS of Kaolin and BC soils. The accuracy of the developed models were initially validated using various statistical checks such as R, MAE, RMSE and RSE. For the 2nd level validation, parametric and sensitivity analyses were carried out for both soils, which yielded a comparable variation and contribution of each input conforming to the literature.

Multi Expression Programming Model for Strength Prediction of Fly-Ash-Treated Alkali-Contaminated Soils.

Rapid industrialization is leading to the pollution of underground natural soil by alkali concentration which may cause problems for the existing expansive soil in the form of producing expanding lattices. This research investigates the effect of stabilizing alkali-contaminated soil by using fly ash. The influence of alkali concentration (2 N and 4 N) and curing period (up to 28 days) on the unconfined compressive strength (UCS) of fly ash (FA)-treated (10%, 15%, and 20%) alkali-contaminated kaolin and black cotton (BC) soils was investigated. The effect of incorporating different dosages of FA (10%, 15%, and 20%) on the UCSkaolin and UCSBC soils was also studied. Sufficient laboratory test data comprising 384 data points were collected, and multi expression programming (MEP) was used to create tree-based models for yielding simple prediction equations to compute the UCSkaolin and UCSBC soils. The experimental results reflected that alkali contamination resulted in reduced UCS (36% and 46%, respectively) for the kaolin and BC soil, whereas the addition of FA resulted in a linear rise in the UCS. The optimal dosage was found to be 20%, and the increase in UCS may be attributed to the alkali-induced pozzolanic reaction and subsequent gain of the UCS due to the formation of calcium-based hydration compounds (with FA addition). Furthermore, the developed models showed reliable performance in the training and validation stages in terms of regression slopes, R, MAE, RMSE, and RSE indices. Models were also validated using parametric and sensitivity analysis which yielded comparable variation while the contribution of each input was consistent with the available literature.

Effect of Microwave Treatment on Adzuki Beans (Vigna angularis L.) under Dry State-Analyzing Microstructure, Water Absorption, and Antioxidant Properties.

In this study, a microwave was used on adzuki beans (Arari and Geomguseul) without water, in order to investigate their changes in microstructure, water absorption, and antioxidative properties. As the microwave treatment time increased (2450 MHz, 0 to 60 s), the lightness, redness, and yellowness were reduced, and moisture content significantly decreased in both varieties. The microstructure space between the seed coat, cotyledon, and pores within the cotyledon were observed, due to the loss of moisture. Regardless of microwave treatment, the water absorption behavior of the adzuki beans was sigmoidal. However, the water absorption kinetics of Arari increased after microwave treatment, whereas with microwave-treated Geomguseul, the water absorption rate decreased, compared to the control, except for the sample treated for 30 s. During soaking, the water absorption and softening rates in the microwave-treated adzuki bean were twice as fast as the untreated beans. Antioxidant activity, total phenolic compounds, and total flavonoid compounds were greatly improved by microwave treatment. These results indicate that microwave treatment affects the color, hydration, and bioactive compounds, and it can be used as a pretreatment method before processing adzuki beans.

FORMATION OF GAS HYDRATES, METHODS OF COMBATING THEM AND CAPTURE OF METHANOL LOSSES IN THE GAS PHASE

The article provides a brief analysis of the formation of gas hydrates, methods of combating them and the capture of methanol losses in the gas phase. Under certain thermodynamic conditions, natural gases combine with water to form hydrates, which accumulate in mining and main gas pipelines, increase hydraulic resistance, reduce pipeline capacity and, in some cases, fill the entire section of the pipeline. Hydrate compounds can form not only in gas pipelines, but also in gas wells, depending on the conditions. Therefore, during the extraction and transportation of natural gases, it is almost always possible to encounter hydrate compounds in mining equipment and gas pipelines. Because hydrates of natural gases are unstable compounds, they are separated into gas and water when the temperature rises or the pressure decreases. Hydrate compounds are a white crystalline mass that looks like ice or black. Components such as carbon dioxide, hydrogen sulfide, nitrogen, etc. are often found in natural gases. The presence of sour gases dramatically accelerates the process of hydration. Keywords: hydrates, methanol losses, gas phase, sour gases, hydraulic resistance, hydration formation

Kinetic Inhibition of Clathrate Hydrate by Copolymers Based on N-Vinylcaprolactam and N-Acryloylpyrrolidine: Optimization Effect of Interfacial Nonfreezable Water of Polymers.

Amphiphilic polymers have now been designed to achieve an icephobic performance and have been used for ice adhesion prevention. They may function by forming a strongly bonded but nonfreezable water shell which serves as a self-lubricating interfacial layer that weakens the adhesion strength between ice and the surface. Here, an analogous concept is built to prevent the formation of clathrate hydrate compounds during oil and natural gas production, in which amphiphilic water-soluble polymers act as efficient kinetic hydrate inhibitors (KHIs). A novel group of copolymers with N-vinylcaprolactam and N-acryloylpyrrolidine structural units are investigated in this study. The relationships among the amphiphilicity, lower critical solution temperature, nonfreezable bound water, and kinetic hydrate inhibition time are analyzed in terms of the copolymer compositions. Low-field NMR relaxometry revealed the crucial interfacial water in tightly bound dynamic states which led to crystal growth rates changing with the copolymer compositions, in accord with the rotational rheometric analysis results. The nonfreezable bound water layer confirmed by a calorimetry analysis also changes with the polymer amphiphilicity. Therefore, in the interface between the KHI polymers and hydrate, water surrounding the polymers plays a critical role by helping to delay the nucleation and growth of embryonic ice/hydrates. Appropriate amphiphilicity of the copolymers can achieve the optimal interfacial properties for slowing down hydrate crystal growth.

A comprehensive evaluation of fracture toughness, fracture energy, flexural strength and microstructure of calcium aluminate cement concrete exposed to high temperatures

In this study, a comprehensive experimental program was developed to determine the microstructural, mechanical, and fracture features of calcium aluminate cement concrete (CACC) after exposure to high temperatures. The residual fracture parameters, including fracture toughness, fracture energy, and characteristic length, were obtained based on RILEM recommendations. In addition, XRD and SEM were used to evaluate microstructural changes after exposure to different temperatures. Mechanical properties such as the residual compressive, tensile, and flexural strengths, as well as the elastic modulus, were also assessed. The SEM images revealed that the voids among the particles increased due to increasing internal vapor pressure, indicating that the number of pores in the concrete structure increased. Furthermore, the results showed that after subjecting the specimens to high temperatures, the concrete became more ductile, which may be due to the increase in the number of pores after water evaporation. The residual fracture energy of CACC was observed to increase with increasing temperature. However, the residual fracture toughness and flexural strength decreased as temperatures increased. In addition, the results demonstrated that, above 400 °C, the weight loss in the concrete is mainly due to the evaporation of chemically bound water and decomposition of cement hydration compounds, which are chemical processes.

Molecular dynamics approach to study the effects of MgCl2 salt atomic ratio on the phase transition phenomenon in the phase change materials

In general, phase change materials reduce energy consumption in different structures by increasing the thermal conductivity or decreasing the phase change time. On the other hand, hydrated salts are the most important group of phase change materials with high phase change temperatures and are extensively studied in latent thermal energy storage systems. Today, these atomic structures are used in different usages such as thermal transfer compounds, commercial and industrial applications, for cooling and heating on a small scale, etc. In the current computational study, we utilized Molecular Dynamics procedure to explain the thermal and phase transition (from liquid to solid-state) behavior of water liquid in the presence of MgCl2 salt as salts hydrate compound. Computationally, physical parameters like temperature, potential/total energy, phase transition time, thermal conductivity, and velocity/density profile of H2O-MgCl2 nanofluid were reported for time=15 ns. Molecular Dynamics outputs indicated that the phenomenon of phase transition in simulated nanofluid happens in a shorter time using a 4% atomic ratio salt structure. This atomic behavior of simulated structure causes thermal behavior improvement is defined nanofluid. Numerically, by MgCl2 salt ratio optimizing, H2O-MgCl2 nanofluid thermal conductivity converged to 0.67 W/m.k. Technically, thermal conductivity calculation in current research is done by using the Green-Kubo method.

Study of the action of nano-alumina particles in hydrated lime pastes

The present study aims to describe the effect of the addition of nano-alumina (NA) in the properties of hydrated lime pastes. Different proportions of NA (0%, 3.0%, 6.0% and 12.0%w/w) were added in hydrated lime, the specimens were cured for a 90-day-period and the mechanical and microstructural properties were studied. The X-Ray diffraction (XRD) patterns revealed the formation of Ca–Al–CO3-LDH compounds at early age lime pastes. The accelerated carbonation of NA-modified systems, the interlayer water and the hydroxyl groups of Ca–Al–CO3-LDH compounds were recorded using thermogravimetric analysis (TGA). Attenuated total reflection (ATR) assignments confirmed the findings mentioned above by identifying the formed carbonate groups. The calcium aluminate carbonate hydrate compounds (Ca4Al2O6(CO3).11H2O) that were formed were found to be unstable in time. As a result, their decomposition led to the acceleration of carbonation and compressive strength enhancement. NA improved the inherent weakness of hydrated lime by providing early age strengthening.

Reactive Transport Modelling of Chloride Ingress in Saturated Coral Aggregate Concrete

Utilizing coral aggregate concrete (CAC) for construction on remote islands can significantly reduce construction cost and period, CO2 emission, and consumption of non-renewable energy. The durability of reinforced CAC structures is critically influenced by their resistance to chloride attack. In this study, a reactive transport modelling was developed to investigate chloride ingress in CAC, in which a COMSOL-PHREEQC interface based on MATLAB language was established. The experiment from the literature was taken as a benchmark example. The results show that the developed numerical model can accurately predict chloride transport in CAC. Differing from ordinary aggregate concrete (OAC), Kuzel’s salt does not appear in cement hydrate compounds of CAC during chloride ingress. The numerical results indicate that the penetration depth of chloride in CAC gradually increases as the exposure time is prolonged. When CAC is exposed to an external chloride solution, the decrease in the pH of the pore solution affects the precipitation of Friedel’s salt, which is detrimental to the chemical binding of chloride.

Synthesis and identification of some azatidinone containing pyridine moiety and evaluation their biological activity

Compound dimethyl pyridine-2,6-dicarboxylate (1) was synthesized via the reaction of pyridine-2,6-dicarboxylic acid with methanol. Pyridine-2,6-dicarbohydrazide (2) was synthesized via the reaction of compound (1) with hydrazine hydrate compounds of N,N-bis-(sub. benzylidine) pyridine-2,6-dicarbohydrazide (3–8) were synthesized Via the reaction of compound (2) with aromatic aldehyde compounds of N,N-bis(3-chloro(sub,phenyl)-4-oxoazetine-1-yl-pyridine)-2,6-dicarboxamide (9–14) were synthesized via the reaction of compounds (3–8) with chloro acetyl chloride the biological activity for some compounds were tested the synthesized compounds were identified by I.R, C13.N.M.R, H1.N.M.R and melting point.

Spectroscopy of excised skin patches exposed to THz and far-IR radiation.

Applications of far infrared (Far-IR) and terahertz (THz) radiation in areas such as healthcare and security are fast-growing. As a consequence, humans and the environment are becoming more exposed to mm-wave and Far-IR radiation than previously. We examined typical skin-care and sunscreen ingredients and propitiatory products with transmission FTIR, ATR-FTIR and THz-time domain spectroscopy (THz-TDS) methods using fresh and dehydrated toad and fresh human skin samples for their absorption properties in these frequency ranges. The skin hydration compounds glycerol and sorbitol have comparable absorption characteristics to physiological bulk water. Products containing these and similar hydrating compounds have significant Far-IR absorption characteristics. The sunscreen ingredients ZnO (20 micron), TiO2 (mesh 325), and graphene platelet demonstrate a generally poor Far-IR absorbance, with TiO2 displaying some frequency-specific absorption in the 3-6 THz and 12 THz regions. The Far-IR absorbance of proprietary sunscreens was, however, shown not to be significant. The absorption properties of melanin, collagen, bound water, and other constituents are significant in dehydrated skin samples but are not of the same order of importance as the hydrating agents examined.

X-Ray Diffraction and Infrared Spectroscopy Data Review Analyses of the Calcium Phosphates

The objective of this literature reviews is to report the various methods used in the synthesis of the calcium monophosphates and condensed phosphates compounds, such as the co-precipitation method, Boulle's process, solid-state reactions, hydrothermal synthesis, and thermal dehydration, and present the crystalline data of these salts as classified from the hexagonal to the triclinic system. For the monophosphates, the compounds with (PO4)3- groups crystallized in the hexagonal, rhombohedral, trigonal, orthorhombic, and monoclinic systems, against the compounds with (HPO4)2- and (H2PO4)-, which are crystallized in low symmetry systems (monoclinic, and triclinic). For the long polyphosphates chain (PO3-)n, where the formula contains one (PO4)3- group, the compounds crystallized in the high possible symmetry (tetragonal systems); the compounds of a formula containing two, three, and four (PO4)3- groups are crystallized in the lower symmetry systems (monoclinic, and triclinic). In the anhydrous cyclotetraphosphates, the substitution of 2K+ by Ca2+ induced lowering symmetry from the tetragonal system in CaK2P4O12 to the triclinic system in Ca2P4O12. The calcium cyclohexaphosphates are all found to be hydrate compounds. With ammonium cations, the (NH4)6P6O18.1H2O crystallized in the orthorhombic system, as a highly symmetrical system found in this phosphate type. Besides, the study is extended to review the inferred characterization made particularly for anions, PO3- in γ-Ca(PO3)2, PO43- in CaHPO4, P2O74- in β-Ca2P2O7, P3O93- in MnCa2(P3O9)2, P4O124- in Ca2P4O12.1.5H2O2⋅3H2O and P6O186- in Ca2K2P6O18.6H2O.

Gas Hydrates as a Means for Biogas and Biomethane Distribution

Biomethane is receiving great attention as a renewable energy gas with lower environmental impacts and diversified sources of production. However, availability of gas infrastructure is an important factor in biomethane development and use. Biomethane can be distributed by the natural gas or local biogas grid. Biomethane can also be road-transported as compressed biomethane (CBG) or liquefied bio-methane (LBG). Biomethane could be distributed via gas hydration technology, where methane molecules are physically trapped within the crystalline structures of frozen host water molecules as gas hydrate compounds. Using life cycle assessment methodology, this study compared the energy performance and climate impact of two gas hydrate scenarios, biogas hydrate and biomethane hydrate, with that of a base case distributing biomethane as CBG. The technical system, from biogas upgrading, hydration, compression and road transport to filling station of biomethane as CBG, was included in the analysis. Results of this study show that distribution of biomethane as gas hydrates had a lower energy performance and higher climate impact than compressed biomethane distribution. The low energy performance was due to high electricity demand in hydrate formation and dissociation processes. The gas hydrate scenarios also had higher climate impacts as a result of high methane losses from hydrate formation and dissociationdissociation and emissions related to energy source use. Biogas upgrading to biomethane also significantly contributed to methane losses and climate impact of the scenarios studied.

3D-АДДИТИВНЫЕ СТРОИТЕЛЬНЫЕ ТЕХНОЛОГИИ. ТЕОРИЯ И ПРАКТИКА

The results of the study of the theoretical foundations of the manufacture of building materials using 3D printing based on composite binders with various molding methods and their practical testing on prototypes of fine-grained concrete are presented. The principles of regulating the structure and properties of composites through the use of a mineral modifier for the construction of high-rise building objects using 3D-additive technology are considered. The influence of the characteristics of the raw material components on the properties of the obtained composite is shown. The structure formation of the hardening cement-containing system in the presence of a mineral modifier proceeds more intensively due to the high specific surface area and energy capacity of the components, which is an active mineral additive and the basis for the crystal formation of new hydrate compounds. The difference in the strength characteristics of the printed wall is due to the direction of the sample cut. Applying a breaking load along the direction of forming of a 3D printer gives a slightly higher strength than perpendicular to the direction of forming. This phenomenon can be explained by the shape of the layer after solidification of the mixture, which is an ellipse in cross section

Influence of pH on chloride binding isotherms for cement paste and its components

In this paper, chloride (Cl−) binding isotherms are developed for cement hydration compounds, specifically, calcium-silicate-hydrates (CSH) and AFm phases including mono-sulfate aluminate, hydroxy-AFm, monocarbonate-AFm, and hemicarbonate-AFm, in simulated concrete pore solutions to account for the effect of pH and the presence of other ions. pH and the presence of other ions have a strong influence on the Cl− binding capacity of cement compounds, which have not been taken into consideration in previous research. A novel experimental technique is developed to characterize the binding capacity from very low (1 mM) to very high concentrations (5 M). To overcome the existing challenges of measuring both low and high Cl− concentrations without significant dilution and in the presence of SO42− and OH− ions, a potentiometric method was used. The amorphous CSH in the hydrated cement paste; thus, the heterogeneity of the hydrated components of the cement paste was also quantified and accounted for in this study.

Humidity and Moisture Degradation of Perovskite Material in Solar Cells: Effects on Efficiency

Humidity is the concentration of water vapor in air and moisture is the relatively small amount of water in a material. The two both have positive and negative influences on the development of perovskite solar cells. It is becoming increasingly clear that the effects of humidity will be a key factor to drive the commercialization of this promising new solar cell technology. The interface amid MAPbI3 and water vapor has been explored and studied by different researchers through optical absorption spectrometry, morphological and crystallographic studies. These studies have helped to demystify the complex interactions going on in the system. A particular study reported the possibility of a perovskite molecule forming a hydrate compound when exposed to H2O vapor in the dark coupled with its dissolution of MAPbI3. Some researchers have said that to improve the stability of this device in moisture. The device must be studied as a whole system rather than studying just the individual components. This review paper explores the works done on perovskite stability highlighting how humidity and moisture affect both the preparation and performance of perovskite material and perovskite solar cell.

Influence of fly ash on hydration compounds of high-volume fly ash concrete

<abstract> Development of sustainable materials has become one common goal across the globe to meet the ever-increasing demand for the construction materials. High volume fly ash (HVFA) concrete is one such sustainable construction material which utilizes fly ash in concrete as a partial replacement of cement. Though the existing literature focuses abundantly on high volume fly ash concrete, the present work aimed to explore the intricate hydration process thorough a systematic experimental program. A series of experiments including compressive strength, rapid chloride permeability, UPV, acid resistance, X-ray diffraction, SEM and EDAX were performed to examine the effect of varying proportions of fly ash (0%, 20%, 40%, 60%) on cement replacement. Analysis of results indicated formation of hydration compounds in the form of alite, belite, celite, portlandite and tobermorite (C-S-H gel). Results of mechanical and durability tests showed that, to achieve maximum benefits, cement can be replaced to an optimum value of fly ash of 40%. The authors believe that the formation of hydration compounds tobermorite and celite resulted in attaining enhanced durability and strength in high volume fly ash concrete. </abstract>

Study on cement paste blended with calcined granite powder

Granite in India is famous for flooring and also used as concrete aggregate. Granite mineral is processed in the industry and large sheets are made which are used as the flooring of dwelling units. During the processing of granite, the mineral is cut into suitable pieces and polished which produces very fine powder. The fine granite powder is a by-product of the granite industry and which is often used for landfill. On the other hand, the granite crushers industries break the granite to suitable sizes to make concrete aggregates also have this fine granite powder as its by-product. Granite is a hard mineral-rich in silica. The silica-rich mineral can be used in concrete as a mineral additive. The hydration compounds of cement in concrete have free lime and mineral admixtures rich in silica are useful in secondary reacting with the excess lime to form C-S-H gel. In the present study, experimental results are discussed for the suitability of granite powder in concrete manufacturing. In the present work, the cement by partial replacement with granite powder in normal state and calcined state up to 50% and the compressive strength of cement paste is found at 28 days. The results indicate that the partial replacement of cement with granite powder results in only a 10% decrease in strength when cement is replaced up to 30% with granite powder.

ТЕРМОДИНАМИЧЕСКИЕ СВОЙСТВА ГАЗОГИДРАТНЫХ СОЕДИНЕНИЙ

The most stable forms (compositions) and thermodynamic characteristics of gas hydrates СН4•6Н2О, С2Н6•8Н2О, С3Н8•17Н2О, i-С4Н10•17Н2О, СO2•6Н2О, O2•6Н2О, H2S•6Н2О, N2•6Н2О, Ar•6Н2О were defined based on the analysis of literature data and own research on the composition and thermodynamic properties of gas hydrate compounds. Correlation dependences of thermodynamic characteristics of gas hydrates depending on the composition were graphed. All the main thermodynamic characteristics of gas hydrates – standard enthalpies and Gibbs energies of formation, standard entropies, temperature dependences of isobaric heat capacity, enthalpy and entropy of dissociation (formation) of gas hydrates into hydrate-forming gas and water (ice) – were determined based on the results of the examination, assessment, calculation and data agreement