Anhydrite Binder Research Articles

Снижение экологической нагрузки на регион за счет рационального способа утилизации фторангидрита

The article considers the chemical industry technologies contaminating the environment with sulfate-calcium waste in three regions of the former Soviet Union, i.e., the Tomsk region (SHK LLC, Seversk), the Perm territory (Galopolimer JSC, Perm), and East Kazakhstan region (UMZ JSC, Ust-Kamenogorsk). The differences and similarities of technological processes of anhydrous calcium sulfate production in the above-mentioned regions have been considered. Some properties of sulfate calcium (acid fluoride) that until recently was the main environmental contaminator used in the technology of hydrogen fluoride production have been specified. The objective of the study is to provide generalized positive results obtained by the authors of the article in the field of optimization of sulfuric decomposition of fluorspar not changing the production conditions and the quality of the main product — hydrogen fluoride. As a result of the process, the solid waste of hydrogen fluoride production is transformed into a target product, i.e., a technogenic anhydrite binder that can be an alternative to Portland cement and gypsum binders in the construction industry. Therefore, acid fluoride waste is removed from the hydrogen fluoride technology, and the environmental contamination with sulfate-calcium waste is prevented. In addition, a new trend in the construction industry is set, which is the industry production of anhydrite materials and products. The list of pilot-industrial and semi-industrial tests of the production of various anhydrite products has been provided (as an image listing the fields of use of acid fluoride in the industry of construction materials). In conclusion, the amount of environmental damage caused by the acid fluoride waste has been specified. In the Ob basin of the West Siberian region, it was 270 million rubles for 2023.

Activation of fluoranhydrite with various chemical additives for the production of gypsum fiberboards

Preliminary studies of fluoranhydrite as a binder showed that on its own it almost does not harden, intervention in the technological process of basic production is almost impossible, so in order to obtain materials it is necessary to develop ways of modifying it to initiate the binder properties or use “acidic” fluoranhydrite before the neutralization stage. In this work the influence of various additives (sodium sulfate and sodium sulfite, potassium sulfate, copper sulfate, iron sulfate crystallohydrate, alumina aluminate, sodium carbonate) on the properties of fluorine hydrite binders produced by neutralization of sour waste from hydrofluoric acid production with an excess of limestone was studied. In this work to obtain dependences of anhydrite binder technological properties on the number of introduced additives and determine the optimal composition of the binder, as well as create mathematical models of the processes under study and their statistical analysis used mathematical planning of the experiment. As the conducted studies showed the speed of setting of products based on anhydrite binder and their strength mainly depend on the temperature of water and its amount for mixing at the optimum dispersity of the binder. The strength of the samples made from the neutralized waste was found to be in the range of 0.5‒1.2 MPa, and the strength of the samples based on the activated anhydrite binder ― in the range of 5.3‒10.7 MPa that corresponds to the parameters of the material suitable for the production of boards.

Analysis of Compressive Strength of Anhydrite Binder Using Full Factorial Design.

Flue gas desulfurization gypsum (FGD gypsum) is obtained from the desulphurization of combustion gases in fossil fuel power plants. FGD gypsum can be used to produce anhydrite binder. This research is devoted to the investigation of the influence of the calcination temperature of FGD gypsum, the activators K2SO4 and Na2SO4, and their amount on the compressive strength of anhydrite binder during hydration. The obtained results showed that as the calcination temperature increased, the compressive strength of anhydrite binder decreased at its early age (up to 3 days) and increased after 28 days. The compressive strength of the anhydrite binder produced at 800 °C and 500 °C differed more than five times after 28 days. The activators K2SO4 and Na2SO4 had a large effect on the hydration of anhydrite binder at its early age (up to 3 days) in comparison with the anhydrite binder without activators. The presence of the activators of either K2SO4 or K2SO4 almost had no influence on the compressive strength after 28 days. To determine which factor, the calcination temperature of FGD gypsum (500-800 °C), the hydration time (3-28 days) or the amount (0-2%) of the activators K2SO4 and Na2SO4, has the greatest influence on the compressive strength, a 23 full factorial design was applied. Multiple linear regression was used to develop a mathematical model and predict the compressive strength of the anhydrite binder. The statistical analysis showed that the hydration time had the strongest impact on the compressive strength of the anhydrite binder using activators K2SO4 and Na2SO4. The activator K2SO4 had a greater influence on the compressive strength than the activator Na2SO4. The obtained mathematical model can be used to forecast the compressive strength of the anhydrite binder produced from FGD gypsum if the considered factors are within the same limiting values as in the suggested model since the coefficient of determination (R2) was close to 1, and the mean absolute percentage error (MAPE) was less than 10%.

The effect of carbonate fillers on the properties of anhydrite binder and gypsum stone

Technology of contact hardening composite materials based on substandard raw materials is presented. Production of anhydrite binder having relatively high strength in comparison with other types of gypsum binders is shown. The scope of application of anhydrite binder: plaster and masonry mortars, floor screeds, solutions for filling mine workings, decorative facing plates, architectural details, small-piece wall stones, dry mixes.

Production of Anhydrite Binder from Waste Fluorangydrite

The technology for obtaining hydrofluoric acid and the peculiarities of its production were studied, and the physical and chemical properties of the waste were examined. Activators that accelerated the hardening of the anhydrite binder were selected. The process of recycling fluorine hydrite waste from the production of hydrofluoric acid at Ulba Metallurgical Plant JSC was studied, and anhydrite unburnt binder with a setting time of 30 min was obtained. On the basis of the obtained data, a technological scheme of anhydrite binder production was developed. The effectiveness of the technological scheme was confirmed experimentally. This work aimed to study the possibility of the integrated use of secondary and anthropogenic raw materials from Ulba Metallurgical Plant, which represents an important means of not only increasing production efficiency and economic benefits and reducing the irrational alienation of land resources, but also protecting against the pollution of water and air basins, as the environmental policy of UMP JSC is nowadays of great importance.

Research of the Possibility of Creation of a Multipurpose Complex Additive for Dry Mixtures

The main objective of the study was to obtain an effective component composition of a dry building mixture with the use of a complex additive. In this work the specific surface area of the anhydrite binder was determined. It is optimal for providing the mixtures with the required characteristics. The manufacture of experimental compositions was made, according to pre-selected recipes. From them through the performed tests, the most effective was identified. The composition of the modified anhydrite binder was established. It had to match the reference requirements for filling mixtures. The conclusion was formulated about the ability of additives to influence the technological and physical-mechanical properties of the filling mixtures.

Anhydrite Binder Modified with a Complex Additive for Dry Building Mixtures

Anhydrite Binder Modified with a Complex Additive for Dry Building Mixtures

Technogenic anhydrite binder for high-strength concrete

Technogenic anhydrite binder for high-strength concrete

Efficient technologies for making gypsum binders

A number of various proposed options and flow charts applied for the production of gypsum binders are considered herein. Large volumes of inorganic waste amount to millions of tons therefore the phosphogypsum utilization to get effective gypsum binders is an urgent issue. The production of phosphogypsum binders both in our country and abroad is indicated to go in three main directions - burnt, autoclaved and anhydrite (hard-burnt) binders.

Low‐energy technology for producing anhydrite in the CaCO3–H2SO4–H2O system derived from industrial wastes

AbstractBACKGROUNDA high‐quality anhydrite binder could be produced due to the exergy of sulfuric acid in the CaCO3–H2SO4–H2O system derived from industrial wastes. Waste of sulfuric acid derived from the production of heat‐resistant fibers and wastes of limestone that was formed on the metallurgical enterprise were used for the synthesis of anhydrite. Such a product is safe from an environmental point of view and has many advantages, both operational and economic, over standard gypsum binders.RESULTSThe optimal technological parameters have been established and a technological scheme for producing anhydrite excluding the stage of calcium sulfate dihydrate formation has been proposed. Anhydrite production in the CaCO3–H2SO4–H2O system, due to the exergy of sulfuric acid, is a promising technology to replace the traditional thermal technology for producing anhydrite. This technology can reduce fuel costs because the required synthesis temperature is 95–105 °С, instead of 800–1000 °С in the traditional one, and this significantly reduces the cost of manufactured products.CONCLUSIONThe maximum yield of synthetic anhydrite was provided by a limestone suspension taken in a stoichiometric amount. This neutralizing agent makes it possible to obtain particles of a prismatic shape, the size of which is generally more than 20 μm. © 2021 Society of Chemical Industry (SCI).

Analysis of early structure formation of anhydrite binders from secondary raw materials using microcalorimetry

This article presents results of a research on changes in energy parameters of fluorogypsum composition of normal consistency with introduction of various additives (μΔn) such as sodium sulfate and sodium sulfite. Activity of binder in interaction with water was defined as the sum of thermal effect of hydration and thermal effect of dispersion of fluorogypsum crystal lattice. In order to compare processes of heat release in the studied gypsum-containing systems, the article presents results of analysis for the following ones: fluorogypsum binder – water, fluorogypsum binder – sodium sulfate – water and fluorogypsum binder – sodium sulfite – water. Research has shown that processes of hydration during by development of alternating exothermic and endothermic effects in systems containing fluorogypsum binders.

A STUDY ON MECHANICAL PROPERTIES AND STRUCTURE OF ANHYDRITE BINDER MODIFIED BY ULTRA-DISPERSED SILTSTONE

This research is devoted to modification of physical and mechanical properties and structure of a binder based on natural anhydrite. A sedimentary rock siltstone was added into the composition as a mineral ultrafine additive. The presence of aluminosilicate minerals proves that finely ground siltstone can be used as a mineral additive in the composition of the anhydrite binder, accelerating crystallization of gypsum new formations and densifying the structure of gypsum stone. For the first time, the effectiveness of using sodium and ammonium phosphates as hardening activators of an anhydrite binder was shown. Siltstone, added to the composition in the amount from 0 to 5%, lead to up to 40% increase in strength, which is due to the action of siltstone particles as “crystallization centers” and formation of crystalline hydrates of calcium sulfate dihydrate on their surface. Combined action of calcined siltstone and lime leads to a 45% increase in strength due to the additional compaction by new hydration products formed in the course of metakaolin and lime interaction. Microstructural analysis showed that samples with calcined siltstone and lime have a more dense and uniform structure with a lower porosity, compared to those with only natural siltstone.

Research in the Influence of Various Activating Additives on the Properties of Anhydrite Binder

Research in the Influence of Various Activating Additives on the Properties of Anhydrite Binder

Efficient heat-insulating material based on technogenic anhydrite

Physical and mechanical properties of the heat-insulating composition based on high-strength anhydrite binder with expanded perlite sand as a lightweight aggregate have been studied. The study has evaluated the influence of two poring components, air-entraining additives and aluminum powder suspension, on the main characteristics of the composition: the compressive strength of the sample, its average density, thermal conductivity, and water absorption. The studies have shown that adding an air-entraining agent in an amount of 1.2% by the weight of dry fluoroanhydrite significantly influenced the decrease in the average density (up to 37%) of the material. The developed composition with a lightweight aggregate based on expanded perlite sand and an air-entraining additive can be used in construction as an efficient heat-insulating material, including for filling cavity walls during frame construction.

Structural and Thermal Insulation Materials Based on High-Strength Anhydrite Binder

The properties of a structural and thermal insulation composition based on a high-strength anhydrite binder based on fluoroanhydrite and expanded perlite sand have been studied. Fluoroanhydrite is a waste product of hydrofluoric acid and it is an eco-friendly material. Due to the processing of man-made anhydrite, it is possible to reduce the harm caused to nature in places of raw materials dumps, as well as significantly reduce the cost of producing new construction materials. The use of anhydrite compounds in the manufacture of products is limited with low speed setting and hardening. To activate the structure formation of the anhydrite binder, 3% aqueous solution of sodium phosphate Na3PO4 was used. Expanded perlite sand was used as an ultralight aggregate. As a result of the experiments, it was possible to obtain a lightweight composition possessing high strength. Studies of the microstructure and X-ray microanalysis showed new formations appearing in the interfacial zone at the border of the anhydrite binder and expanded perlite, which is confirmed by the results of the infrared spectroscopy. Also there has been noted the consolidation of the anhydrite binder structure by nanodispersed structures formed in the intercrystallite pores of the anhydrite binder. The developed composition can serve as a cheap substitute for gypsum in the production of warm plaster, gypsum boards, architectural elements by molding, tongue-and-groove slabs, wall blocks, as well as wall thermal insulation during frame construction, including for filling hollow masonry.

Properties and Structure of Anhydrite Binder of Ergachinsky Deposit in the Presence of Phosphate Activators and Aleurolite

Properties and Structure of Anhydrite Binder of Ergachinsky Deposit in the Presence of Phosphate Activators and Aleurolite

Influence of modifying composition of gypsum binders on the structure of composite materials

At present, the modern society utilizes composite materials in various branches of the national economy. The properties of such materials depend on their composition and structure, and may considerably differ from the properties of source materials. In turn, texture and structure of crystals, their packing order, size and level of sophistication affect the structure of materials. This is particularly demonstrated by hydration curing materials on the basis of gypsum and magnesia binding materials, as well as portland cement. Structuring control is one of the key problems of composite materials. Gypsum binding materials with various modification composition are suggested as a model system to study the influence of texture and structure of materials on their properties. One of them is the construction gypsum – an anhydrite binder and a multiphase gypsum binder (MGB). Scanning electron microscopy (SEM) was chosen as the main method of study. It is found that gypsum crystals that are formed during hydration and curing of gypsum binders with various modification composition have different texture and structure. It prevents from getting the optimal packing of a material. It is justified and confirmed that the MGB consisting of several modifications of calcium sulfate allow choosing the best material composition due to the combination of crystals having different size and form. Besides, MGB contains significant amounts of insoluble anhydrite that reduces the water-gypsum ratio of a binder and compacts its structure. Considerable attention is paid to microfillers, which significantly affect the texture and structure of materials based on gypsum binders. Iron ore concentrate of the Lebedinsky GOK generally consisting of magnetite, as well as impalpable flour cullet waste of sodium and potassium glass were used as microfillers in the given study. Ultra- and nanodispersed powders at their introduction to gypsum and anhydrite compositions change the size and morphology of crystal newgrowths and ensure the formation of ordered, denser and uniform fine-crystalline structures of composite materials, which leads to the reduction of structure imperfection, porosity and increase in contact areas of crystalline hydrates increasing physical and mechanical performance of gypsum materials. Efficient composite construction materials are obtained on the basis of MGB and microfillers.

Influence of Plasticizers on Properties of Anhydrite Binder

This paper deals with the development and research of sulphate binder based on anhydrite for the industrial production of dry mortar self-leveling mixtures. As part of the experimental activity, selected plasticizers for the sulphate binders were tested. These additives were added in various weight ranges. The tests were carried out first on anhydrite pastes and then on anhydrite mortars of standard composition. Their influence was mainly observed on the achieved basic technological properties, such as the consistency, the initial setting time and the achieved strength.

Fuzzy batch controller for granular materials

The paper focuses on batch control of granular materials in production of building materials from fluorine anhydrite. Batching equipment is intended for smooth operation and timely feeding of supply hoppers at a required level. Level sensors and a controller of an asynchronous screw drive motor are used to control filling of the hopper with industrial anhydrite binders. The controller generates a required frequency and ensures required productivity of a feed conveyor. Mamdani-type fuzzy inference is proposed for controlling the speed of the screw that feeds mixture components. As related to production of building materials based on fluoride anhydrite, this method is used for the first time. A fuzzy controller is proven to be effective in controlling the filling level of the supply hopper. In addition, the authors determined optimal parameters of the batching process to ensure smooth operation and production of fluorine anhydrite materials of specified properties that can compete with gypsum-based products.

Modification of Natural Anhydrite by Mixed Exciter

The objective of this experimental work was to monitor the influence of applied external exciter on anhydrite obtained properties. As a basic raw material anhydrite imported from Poland was used, as hydration exciter a mixture of anhydrous sodium sulphate and Portland cement CEM I 42.5 R in total dose of 5 % by anhydrite weight was applied. In the first step the anhydrite underwent the setting of mineralogical composition using the X-ray diffraction analysis (XRD) and monitoring of grain size and shape by the scanning electron microscopy (SEM). In the next step the influence of applied mixing exciter on obtained basic technological properties according to standard CSN EN 13454 was monitored. It was the setting of basic technological properties of anhydrite binder with and without addition of the mixing external exciter and also the setting of strengths of standard anhydrite mortar with addition of external mixing exciter. Upon the obtained values the comparison with technical requirements of the standard for calcium sulphate binders was carried out and this anhydrite mortar was classified as well.