Silica Raw Material Research Articles

Shrinkage behavior of autoclaved aerated concrete containing calcined diatomaceous earth as the main silica raw materials at various autoclaving temperatures

AbstractIn previous studies, calcined diatomaceous earth (DE) was used as the main silica raw material within the mixture of autoclaved aerated concrete (AAC) to produce DE‐based AAC. Compared to the quartz‐based AAC autoclaved at 192°C, the DE‐based AAC autoclaved at 165°C exhibited, a 57% higher compressive strength and a 54% higher A‐value. In this study, the values of total drying shrinkage are presented in order to complete the results reported in previous studies. According to the results obtained in this study, for AAC with calcined DE, a decrease of 27% in the total value of drying shrinkage was observed as the autoclaving temperature was adjusted to 165°C instead of 192°C. This observation was in opposition to the behavior of AAC with quartz sand which its total value of drying shrinkage increased by 59% when the autoclaving temperature was set to 165°C instead of 192°C. However, in general, a higher total drying shrinkage was observed for the DE‐based AAC autoclaved at 165°C compared to that for the quartz‐based AAC autoclaved at 192°C. The reason could be due to the higher portion of capillary pores and non‐crystalline C‐S‐H as a result of replacing quartz sand with calcined DE within the AAC mixture.

Formation and properties of block vanadium SiO<sub>2</sub> nanomaterial catalyst for SO<sub>2</sub> oxidation

A method for producing a block vanadium catalyst for the oxidation of sulfur dioxide has been studied, which includes the stage of preparing a honeycomb structure framework based on silica raw materials in the form of white soot, followed by applying a substrate in the form of amorphous silicon dioxide and an active component to the surface of the channels. Data on the structural and mechanical properties of the honeycomb catalyst paste have been obtained. A mode of heat treatment of molded products with the production of mechanically strong blocks as carriers of the vanadium catalyst is proposed. Information about the performance of a block vanadium catalyst in comparison with an industrial catalyst of a granular form is given. Ill. 4. Ref. 14. Tab. 1.

A large-scale Sr and Nd isotope baseline for archaeological provenance in Silk Road regions and its application to plant-ash glass

Bioavailable Sr and detrital Nd isotopes are important tools for archaeological provenance. To apply Sr and Nd isotopes for provenance, regional isotope databases and baselines are generally needed. For the vast Silk Road regions of Mesopotamia, Iran, and Central Asia, detailed isotopic distribution patterns essential for determining provenance may not become available in the short term due to the severe deficiency of available data. In the present work, we investigate the geo-environmental factors controlling the Sr and Nd isotopic signatures and use published data from archaeology and Earth sciences, selected by rigorous criteria, to construct the first large-scale, semi-quantitative Sr–Nd isotope baseline for these Silk Road regions. Three isotopic zones are proposed for Central Asia: CA-1 (mountains), εNd < −7.5, 87Sr/86Sr > 0.7095; CA-2 (deserts), εNd = −5 to −2, 87Sr/86Sr ∼ 0.709; CA-3 (loess), εNd = −5 to −2, 87Sr/86Sr > 0.710. General isotopic signatures are suggested for Iran: εNd = −8 to −4, 87Sr/86Sr = 0.7075–0.7090. Three isotopic zones are proposed for Mesopotamia: MP-1 (floodplain and foothill), εNd = −6.5 to −4 (putative extended range MP-1N, εNd = −8 to −6), 87Sr/86Sr = 0.7080–0.7085; MP-2 (deserts), εNd < −8, 87Sr/86Sr > 0.7085; MP-3 (Syrian Euphrates), εNd = −5.5 to −2, 87Sr/86Sr = 0.7080–0.7085. Within the limitation of available data, these ranges indicate the overall trend of bioavailable Sr and detrital Nd isotopic signatures for each isotopic zone, which are controlled by their geological context, climate (e.g., precipitation), and various Earth surface processes (e.g., riverine versus aeolian transport). This baseline can be used as an essential guide for geochemical contexts to suggest or verify the provenance of plant-ash glass, serving as part of an integrative Sr–Nd isotopic approach. We illustrate the potential of this approach using two case studies. By investigating the isotopic compositions of Mesopotamian plant-ash glass, we suggest possible northern Mesopotamian origins for plant ash and silica raw materials used for Mesopotamian glass-making. By reassessing medieval plant-ash glass from San Lorenzo, Italy, we propose diverse origins including Central Asia and Mesopotamia. Additionally, as part of this isotopic approach, by examining the Nd isotope mixing lines in the context provided by the Nd isotope baseline, we reveal the occurrence of glass recycling for Islamic plant-ash glass from different production zones in association with a westward spread from Mesopotamia to the Eastern Mediterranean metropolises.

Energy-efficient Non-autoclave Aerated Concrete Based on Local Silica Raw Materials From Production Wastes

Presents the results of studies (research) on the use of silica raw materials from the production waste of refinement tailings of antimony ores (or antimony ores refinement tailings) and basalt fiber waste, their influence on the quality characteristics of non-autoclave aerated concrete.

Rice husk ash as a silica source for the production of autoclaved aerated concrete – A chance to save energy and primary resources

If the silica raw material used in autoclaved aerated concrete (AAC) requires a lower level of energy for dissolution, a lower autoclaving temperature could be applied to reach the required product performance. Accordingly, the raw material quartz sand in the AAC mixture was replaced with rice husk ash (RHA) which has a higher solubility of silica with increasing temperatures in alkaline binder systems. AAC samples were produced at autoclaving temperatures of 152 °C, 165 °C, 175 °C, and 192 °C with an autoclaving time of 6 h. Quantitative X-ray diffraction (XRD) analysis according to Rietveld refinement, qualitative XRD analysis, and scanning electron microscopy (SEM) were carried out to investigate the microstructure of the hardened AAC samples. Additionally, the compressive strength, dry bulk density, A-value, and total drying shrinkage were determined. In contrast to the quartz-based AAC, the properties of the RHA-based AAC were improved by applying a lower autoclaving temperature than the typical temperature used for industrial production of AAC, i.e. 192 °C. For the RHA-based AAC, a maximum increase of 22% in the compressive strength, 132% in the total content of tobermorite, 19% in the A-value, and a maximum decrease of 33% in the total value of drying shrinkage were observed as the applied autoclaving temperature was changed from 192 °C to 165 °C. Moreover, the material efficiency of the AAC product can be improved by using RHA as an agricultural waste product in the mixture. The RHA-based AAC autoclaved at 165 °C exhibited a slightly higher compressive strength to density ratio (A-value) than the quartz-based AAC autoclaved at 192 °C. However, a higher total drying shrinkage was observed for the RHA-based AAC autoclaved at 165 °C compared to the quartz-based AAC autoclaved at 192 °C. From a general point of view, the results showed that the optimum temperature for autoclaving AAC has a direct dependency on the dissolution properties of silica raw materials used in the mixture.

Rheological properties of Al2O3–CaO–SiO2 slags

The Al2O3–CaO–SiO2 ternary is a basic oxide system relevant for the Pedersen alumina production process and for aluminothermic silicon production with low environmental impact using secondary aluminium and silica raw materials. Rheological property is one of the most important properties for the above applications. A phenomenological viscosity model, inspired by the Calphad technique, has been proposed for the description of the rheological properties covering from homogenous liquid to heterogenous partial solidified Al2O3–CaO–SiO2 slags. The model has been developed by modification of the well-known Vogel-Fulcher-Tammann (VFT) formalism. Based on the phenomenological viscosity model, the effective diffusivity of slag can be evaluated. The relationships between cooling temperature rate, incubation time of solid precipitates as well as transition temperature have then been estimated. The model calculated the isothermal time-temperature-transformation (TTT) and the non-isothermal continuous-cooling-transformation (CCT) curves of CaAl2O4 and anorthite phases are in good agreement with the experimental observations.

Properties of both Chinese silica brick and silica raw material

ABSTRACT The phase and morphology changes of both Chinese silica brick and silica raw material after high-temperature heat treatment, as well as the high-temperature compressive creep behaviour of silica bricks were investigated. The results show that silica raw materials presented a dense structure at room temperature, but cracks and pores appeared after heating treatment. With the crushing of silica particles, silica brick was transformed into homogeneous structure, and final homogeneous degree of the silica brick made of crystalline silica is higher than that of cemented silica. The final creep results of the silica bricks showed expansion after high-temperature compressive creep testing (1550 °C, 50 h), and the expansion of silica brick made of crystalline silica was larger. Compared with the Chinese standard GB/T 5073 - 2005, setting L0 as the original height of the silica brick can more fully reflect the expansion creep characteristics of silica brick.

Obtaining and Properties of a Photocatalytic Composite Material of the "SiO2-TiO2" System Based on Various Types of Silica Raw Materials.

Compositions and technology for obtaining a photocatalytic composite material (PCM) by deposition of titanium dioxide particles synthesized by the sol–gel method on a silica support of various types (microsilica, gaize and diatomite) have been developed. The properties (chemical and mineral composition, dispersion, specific surface area, porosity, ζ-potential, acid–base properties, and microstructure) of microsilica, gaize and diatomite were studied to assess the effectiveness of using a photocatalytic agent as a carrier. In terms of specific viscosity (ηsp = 45), the concentration of the precursor (tetrabutoxytitanium—TBT) is set at 22 vol. % in a solvent (ethanol), at which it is possible to obtain the maximum amount of dissolved film oligomer without the formation of an aggregate-like precipitate. Modification of the reaction mixture (precursor: ethanol = 1:3) by replacing part of the solvent with a Span-60 surfactant/TBT = 1–1.1 made it possible to obtain polydisperse titanium dioxide particles with peak sizes of 43 nm and 690 nm according to laser granulometry data. Taking into account the interaction of titanium complexes with the surface of a silica support, a phenomenological model of the processes of structure formation of a photocatalytic composite material is proposed. By the value of the decomposition of rhodamine B, the photocatalytic activity of the developed composite materials was determined: PCM based on diatomite—86%; PCM based on microsilica—85%; PCM based on gaize—57%.

Production of autoclaved aerated concrete with silica raw materials of a higher solubility than quartz Part II: Influence of autoclaving temperature

This study examines the effects of autoclaving temperature on the mechanical and microstructural properties of autoclaved aerated concrete (AAC) containing calcined diatomaceous earth (C-DE) as the main silica source. The autoclaving process was conducted using an autoclave at various temperatures of T = 134–192 °C and a corresponding steam pressure of P = 2–12 bar for 6 hours. The resultant phases were characterized using quantitative and qualitative X-ray diffraction (XRD), differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The compressive strength of samples containing C-DE as the main silica source increased by 30% when the autoclaving temperature decreased by around 60 °C. This is in complete opposition to samples containing quartz as the only SiO2 source. The compressive strength of the latter decreased by 85% when the autoclaving temperature decreased by approximately 60 °C. For all samples, changes in compressive strength corresponded with changes in tobermorite formation.

Specifics of Structure Formation of Cement Stone with Silica Raw Material - A Substrate of Photocatalytic Composite Material

The increasing urbanization of urban areas poses the challenge of the development of materials capable of self-cleaning from organic pollutants formed. Previous papers substantiated the possibility of the coating of titanium oxide as the main agent of the photocatalytic method of cleaning structural materials on silica raw materials in order to increase the degree of its distribution in the volume of cement matrix and, as a result, increase its efficiency.It is obvious that a silica substrate will affect the processes of structure formation during hardening of a cement matrix. During the research, the processes of phase transformations of cement stone modified with silica raw materials of natural and technogenic origin were studied. As a result, the influence of siliceous modifiers on the strength characteristics of the cement stone was determined, which allowed ranking them according to the degree of decrease in efficiency as follows: technogenic raw materials; natural raw materials of silicate composition; natural raw materials of aluminosilicate composition. Quantitative assessments of the degree of efficiency showed the irrationality of using aluminosilicate composition as a silica modifier of natural raw materials, which is explained by its low pozzolanic activity.

Production of autoclaved aerated concrete with silica raw materials of a higher solubility than quartz part I: Influence of calcined diatomaceous earth

This study examines the effects of calcined diatomaceous earth (C-DE) as a silica raw material of a higher solubility than quartz, on the mechanical and microstructural properties of autoclaved aerated concrete (AAC) produced at the steam curing temperature of 192 °C for 6 h. Quartz within an AAC mixture was replaced at various replacement ratios by C-DE. The resultant phases were characterized using quantitative and qualitative X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA), and thermogravimetric analysis (TGA). In the mixtures with more than 50% substitution of quartz with C-DE, the autoclaving temperature of 192 °C with a duration of 6 h prevented the crystallization of amorphous calcium silicate hydrate (C-S-H) to tobermorite. The optimum strength was obtained at the substitution ratio of 75% despite having the lowest tobermorite content. By substituting quartz with C-DE for higher than 50%, plate-like tobermorite was changed to grass-like and amorphous C-S-H with low CaO/SiO2.

Comparative activity evaluation for silica raw materials and photocatalytic composite materials based on them

Comparative activity evaluation for silica raw materials and photocatalytic composite materials based on them

An archaeometric study of Archaic glass from Rhodes, Greece: Technological and provenance issues

In the present study, a set of 86 beads, of various colours, dating to the Archaic period (640–600 BCE) and excavated on Rhodes island, Greece is investigated using a range of analytical techniques such as SEM/EDX, mXRF and LA-ICP-MS. The role of Rhodes in ancient glassmaking is undoubtful and has been attested by various scholars. Its favourable geographical position being a node between mainland Greece and Asia Minor, Cyprus and consequently the Levantine coast and Middle East enhanced its trading activities and its cultural influences.The main aim of this study is to shed light to the technological features of Archaic glass and in a second stage and through the comparison with already published analytical data of coeval, earlier and later glass samples, to investigate thoroughly the provenance of the Rhodian assemblage.The scientific data demonstrates that there is no continuity in the technology used for the Archaic glass and glass of the subsequent centuries in Rhodes in terms of the basic glass composition. It seems that the technology shifts both in terms of the silica raw materials towards other possible sources and in alkali raw material towards the use of a mineral source rather than plant ash.Relating to the provenance of the Archaic beads, both major-minor and trace elements analysis show that there are strong indications for a Mesopotamian origin. As it is demonstrated in various biplots there is higher correlation between the majority of Archaic samples from Rhodes with samples from Mesopotamia.

SILICA ROCK SINTERING IN WALL CERAMICS PRODUCTION

The paper presents research results on the use of silica rock in the production of lining ceramic brick. The analysis of clay samples showed that they are non-sintering raw materials. The dependence is obtained between the firing temperature and the average density of ceramic brick. It is shown that the firing temperature depends on the material composition with the product water absorption. The relationship is detected between the firing shrinkage, density, and water absorption. The experiments on silica rock sintering show that the ceramic brick made therefrom has a low average density, increased firing shrinkage, porosity and water absorption. Silica raw materials can be used in the ceramic brick production.

Effect of Silica Composition from Rice Husk Ash on The Performace of Absorbing Electromagnetic Wave on Composite of Unsaturated Polyester Resins/Silica

This study aim is to know the effect of silica composition on the absorption of electromagnetic waves in the composite of unsaturated polyester resins (UPR)/silica. Silica raw materials have been synthesized from the results of rice husk ash extraction. The results of the analysis phase and elementary respective using X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) show that the extraction of silica has an amorphous phase with a high purity. This silica powders are filler material acts as an electromagnetic waves absorber material and combined with the UPR as a matrix to form a composite. Silica powder varied with several compositions in this composite. The observation of scanning electron microscope (SEM) shows that the silica particles have been distributed evenly in the UPR matrix. Meanwhile the results of testing the absorption of electromagnetic waves at frequency range of 8 GHz - 12 GHz using a vector network analyzer (VNA) show that the addition of silica composition have significant effect on the absorption of electromagnetic waves. The more the silica content in the UPR matrix causes the absorption of electromagnetic waves more increasing. It was concluded that the presence of silica can improve the absorption performance of electromagnetic waves in composite UPR/silica.&#x0D; Keywords: rice husk ash, silica, UPR, composites, electromagnetic wave absorber

Hydrophobization of Concrete Using Granular Nanostructured Aggregate

The possibility of giving hydrophobical properties to the fine-grained concrete matrix by using a granular nanostructured aggregate (GNA) with a hydrophobizing additive is investigated in this work. GNA is obtained by granulating the silica raw material with an alkaline component. The introduction of a hydrophobizing additive into the raw mix of GNA allows to encapsulate it reducing the negative effect on hydration processes, the intensity of migration of moisture and efflorescence in concrete and, consequently, improving the performance characteristics of fine-grained concrete products. The hydrophobizing ability of a solution of sodium polysilicates formed in the core of GNA during concrete heat and moisture treatment is proved. The analysis of IR spectra after the impregnation of cement stone samples with a solution of sodium polysilicates showed an increase in the degree of hydration and the formation of framework water aluminosilicates. Atmospheric processes modelling showed that the use of GNA on the basis of gaize with calcium stearate and on the basis of fly ash with GKZh-11 makes it possible to increase the resistance of fine-grained concrete to the atmospheric effect of the medium, namely, the outwashing of readily soluble compounds.

Preparation of silica glass with a low degree of internal friction

Based on the analysis of dissipative processes in solids, the factors which determine the magnitude of internal friction in silica glasses have been highlighted and the main principles of the synthesis of silica glass with low internal friction have been stated. In accordance with the developed principles, the process for the preparation and vacuum melting of the silica raw material has been implemented. The results of the study of the prepared glass specimens, which was performed based on the procedure for the measurement of the oscillation decay time, have shown a sufficiently a low degree of internal friction.

Research on the Effect of High-Temperature Melting β-SiC by Raw Materials and Power Supply

Using high quality carbon raw material,high quality silica raw material , the β-SiC powder are prepared by high-temperature vacuum smelting method. The effects of different materials and electrical power to the product of β-SiC quality has been studied. The microstructure and phase analysis of β-SiC powder samples were observed by Scanning Electron Microscopy and X-ray diffraction. The result shows that the raw materials are better, the product quality are better. In addition, the result also indicates that the β-SiC powder have better quality when the power are 3000W.

Optical and spectroscopic characterizations of Algerian silica raw material to predict high quality solar-grade silicon

We assess the potential use as raw material for photovoltaics of Algerian silica samples from the quartz veins of the Tirek deposit and quartz sandstones of the Ain Barda deposit. With 97–98% purity, they all require enrichment before their industrial utilization. Acid leaching and gravimetric separation are used to remove the impurities at the grain boundaries and within the crystal lattice. We obtain course, middle, and fine products. The acid leaching process and the gravimetric separation increase the content of SiO2 up to 99.68%; the residue concentration of iron, alumina and zirconium is decreased to 70, 72 and 58 ppm respectively. These values are in agreement with requirements for silica as raw material destined for solar-grade silicon production.

Mechanically Strong and Hierarchical Porous Silica Ceramics via Gelcasting-Lyophilization

Highly porous silica ceramics were prepared by in-situ gelation of an aqueous suspension with well dispersed silica particles and N’N-dimethylacrylamide (DMAA) monomer, followed by lyophilization and pressureless sintering. The gelcasting process was imparted by polymerization of DMAA. The silica raw materials used in this experiment are the dusts collected from the exhaust fumes of silicon industry. The as-obtained porous silica ceramics had three-dimensional and hierarchical pore structure and the porosity ranged from 75 to 88 % as the sintering temperature varied from 850 to 1050 °C. In addition, the porous silica ceramics appeared to have strong mechanical strength. Compressive strength of the porous silica ceramics was as high as 3.2 MPa even when the porosity was nearly 80%. The gelcasting-lyophilization method was proved to be a novel and promising route for the preparation of highly porous and mechanically strong materials.