摘要 :
We analyzed the stable isotopes (delta O-17, delta O-18 and delta D) of gypsum hydration water (GHW) in a variety of speleothems, as well as condensation and infiltration waters in five caves of the semiarid gypsum karst of Sorbas...
展开
We analyzed the stable isotopes (delta O-17, delta O-18 and delta D) of gypsum hydration water (GHW) in a variety of speleothems, as well as condensation and infiltration waters in five caves of the semiarid gypsum karst of Sorbas basin (Almeria, SE Spain). Microclimate parameters (air temperature, relative humidity and effective condensation rate) were also monitored over an annual cycle. We found that the mother solution from which the majority of gypsum speleothems grow is composed of a mixture of condensation (similar to 60%) and infiltration water (similar to 40%) that undergoes evaporation. Although evaporation of infiltration water alone was thought to be responsible for secondary gypsum precipitation in vadose caves, our results suggest that condensation can be a major source of water for the formation of gypsum speleothems. The modelled d-excess and Delta O-17 trajectories of water during the evaporative process confirm that the majority of speleothems precipitate from a mixture of condensation and infiltration water under relative humidity of 75-85%, similar to that measured in the cave atmosphere during winter. These findings have important implications for future studies of gypsum speleothems as paleoenvironmental archives. (C) 2017 Elsevier B.V. All rights reserved.
收起
摘要 :
Synthetic calcium sulfate dihydrate, obtained from sulfuric acid waste of chemical plants and waste of the fine fraction of limestone, is a potential source of gypsum-containing raw materials. We investigated the processing of syn...
展开
Synthetic calcium sulfate dihydrate, obtained from sulfuric acid waste of chemical plants and waste of the fine fraction of limestone, is a potential source of gypsum-containing raw materials. We investigated the processing of synthetic calcium sulfate dihydrate from sulfuric acid waste to gypsum, high-strength gypsum binder, and anhydrite. The effects of technological parameters on the strength indicators of binders were studied. It was found that the obtained samples of binders (based on synthetic gypsum) meet all standards and even exceed the performance of binders obtained from natural gypsum stone. Our studies show that synthetic gypsum is a promising gypsum-containing raw material for the production of gypsum binders and can be a promising alternative to natural gypsum stone. (c) 2021 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
收起
摘要 :
The amount of waste gypsum board, which is one of the controlled industrial wastes, is increasing year by year, and there is an urgent need to take measures due to concerns about the tightness of the final disposal site. Waste gyp...
展开
The amount of waste gypsum board, which is one of the controlled industrial wastes, is increasing year by year, and there is an urgent need to take measures due to concerns about the tightness of the final disposal site. Waste gypsum board was treated as controlled industrial waste in 1999, and there is concern that there will be a shortage of controlled final disposal sites. In this study, waste gypsum board powder （hereinafter referred to as recycled gypsum powder）, which is obtained by crushing, separating, and heating waste gypsum board, is kneaded into cement mortar. The applicability as a material or an admixture was considered. Although the strength of mortar mixed with recycled gypsum powder decreases, the results show that it is possible to control the strength decrease to some extent by using fly ash and blast furnace slag fine powder together. Since gypsum has swelling properties, the length of mortar mixed with regenerated gypsum powder was changed between wet and dry states, and the effect of mixing was clarified from experiments. Based on these results, the use of recycled gypsum powder was considered. Although the activity of recycled gypsum powder cannot be expected, it is desired to develop applications as bulk materials and backfill materials by paying attention to the feature of reducing shrinkage performance.
收起
摘要 :
The rural and monumental architecture of Northern Spain gives testimony of the wide-ranging constructive possibilities of traditional gypsum for exterior and structural applications. However, today, gypsum is only used for finishi...
展开
The rural and monumental architecture of Northern Spain gives testimony of the wide-ranging constructive possibilities of traditional gypsum for exterior and structural applications. However, today, gypsum is only used for finishing purposes. By combining a bibliographic review with local visits/interviews and experimental gypsum calcinations, we were able to document traditional processing methods and analyze the factors responsible for the decline of exterior and structural gypsum use. Obtained results are also valid for other European countries and contribute to a better understanding of the technical peculiarities of traditional gypsum, hopefully reviving traditional processing techniques to produce compatible and sustainable conservation materials.
收起
摘要 :
The chemical, physico-mechanical properties of gypsum minerals of various deposits of Karakalpakstan are investigated. Studied the colloid-chemical basis for the production of binders. Based on gypsum minerals, gypsum binders such...
展开
The chemical, physico-mechanical properties of gypsum minerals of various deposits of Karakalpakstan are investigated. Studied the colloid-chemical basis for the production of binders. Based on gypsum minerals, gypsum binders such as building gypsum, high-strength gypsum and extreme gypsum, as well anhydrite cement.
收起
摘要 :
We estimate the crystallisation pressure of gypsum quantitatively, with reference to the geological context of the Gypsum Keuper formation. The formation contains sulphatic claystones which have the property of swelling in the pre...
展开
We estimate the crystallisation pressure of gypsum quantitatively, with reference to the geological context of the Gypsum Keuper formation. The formation contains sulphatic claystones which have the property of swelling in the presence of water and have caused substantial structural damage to the linings of several tunnels in Switzerland and Germany. The swelling of these rocks is attributed to the transformation of anhydrite into gypsum, which occurs via the dissolution of anhydrite in pore water and the precipitation of gypsum from the solution. This simultaneous dissolution-precipitation process happens because the solubility of gypsum is lower than that of anhydrite under the conditions prevailing after tunnelling, and it does not cease until all of the anhydrite has been transformed. The elementary mechanism behind the . development of the macroscopically observed swelling pressure is the growth of gypsum crystals inside the rock matrix: If a crystal is in contact with a supersaturated solution, but its growth is prevented by the surrounding matrix, it then exerts a so-called crystallisation pressure upon the pore walls. In the present paper, the crystallisation pressure is calculated by means of a thermodynamic model that takes coherent account of all relevant parameters, including the chemical composition of the pore water and pore size. Variations in these parameters lead to a very wide range of crystallisation pressures (from zero to several tens of megapascals). By using the results of mercury intrusion porosimetry and chemical analyses of samples from three Swiss tunnels, however, we show that the range of predicted values can be reduced significantly with the help of standard, project-specific investigations.
收起
摘要 :
A huge amount of gypsum is generated as an industrial solid waste from flue gas desulphurisation (FGD) installations of thermal power stations. Properties of gypsum - by-product from FGD installation in Maritsa-East-2 thermal powe...
展开
A huge amount of gypsum is generated as an industrial solid waste from flue gas desulphurisation (FGD) installations of thermal power stations. Properties of gypsum - by-product from FGD installation in Maritsa-East-2 thermal power station were studied. Dihydrate gypsum was dried and on the base hemihydrate produced different composite building materials were produced. Using plasticimeter measurments and modelling extrusion process it was proved that the materials obtained may cover all quality requirements for plaster building materials. The optimal conditions related to the extrusion process have been determined on the basis of using different weight ratios of used components. Setting time and the mechanical properties of the materials give sufficient evidences that the new materials produced can be used for wall panels. It was also proved that the new materials would more economically efficient in comparison with the same type of materials produced on the basis of natural gypsum. Gypsum extruded panels production is recommended on the basis of gypsum - by-product as a BAT and suitable way for sustainable utilisation, because the new materials are environmental friendly and economically more efficient.
收起
摘要 :
Continually developing construction industry covers a wide range of building materials with various chemical and mineralogical composition, external and internal structure, physical characteristics, decorative properties. The comb...
展开
Continually developing construction industry covers a wide range of building materials with various chemical and mineralogical composition, external and internal structure, physical characteristics, decorative properties. The combination of these materials leads to the creation of new composite materials with unique characteristics. Although synthetic materials based on polymers and plastics have excellent performance, they demonstrate a significant drawback - they are environmentally unfriendly: when heated, they can emit toxic for humans and the environment products. There is also an issue of processing and utilization of polymer organic materials, the manufacturing of biodegradable materials. Currently, the production of building materials based on eco-friendly gypsum is being resumed. However, gypsum materials are highly porous and hygroscopic, which leads to a decrease in strength. It is known that microorganisms, such as bacteria and microscopic fungi, grow on permanently moistened porous surfaces. Therefore, the objective of this study is to consider various chemical admixtures of hydrophobic and fungicidal action to the surface of gypsum products. The methodological basis is the literature data analysis of obtaining and application of fungicidal-hydrophobic additives for building materials. The result of the study is to make up a list of fhydrophobic chemicals with fungicidal action, and to show the importance of nanotechnological approach in this field.
收起
摘要 :
The object of the study is portland cement produced by grinding clinker with technogenic waste of energy and chemical industries. The possibility to replace the natural gypsum block used to control setting time with technogenic wa...
展开
The object of the study is portland cement produced by grinding clinker with technogenic waste of energy and chemical industries. The possibility to replace the natural gypsum block used to control setting time with technogenic waste is proved. The quality indices of portland cements with various active mineral additives have been subjected to experimental studies in the course of work.
收起
摘要 :
Anhydritic claystones consist of a clay matrix with finely distributed anhydrite. Their swelling has led to severe damage and high repair costs in several tunnels. Gypsum growth combined with water uptake by the clay minerals is t...
展开
Anhydritic claystones consist of a clay matrix with finely distributed anhydrite. Their swelling has led to severe damage and high repair costs in several tunnels. Gypsum growth combined with water uptake by the clay minerals is the main cause of the swelling process. Identifying the conditions under which gypsum rather than anhydrite represents the stable phase is crucial for understanding rock swelling. As existing studies on the anhydrite-gypsum-water equilibrium appear to be contradictory and do not provide all of the information required, we revisit this classic problem here by formulating and studying a thermodynamic model. In contrast to earlier research, our model is not limited to the anhydrite-gypsum equilibrium, but allows for the determination of the equilibrium concentrations of the individual anhydrite dissolution and gypsum precipitation reactions that underlie the sulphate transformation. The results of the paper are, therefore, also valuable for the formulation of comprehensive sulphate-water interaction models that consider diffusive and advective ion transport simultaneously with the chemical dissolution and precipitation reactions. Furthermore, in addition to the influencing factors that have been considered by previous studies (i.e., fluid and solid pressures, concentration of foreign ions, temperature), we consistently incorporate the effect of the surface energy of the sulphate crystals into the thermodynamic equations and discuss the effect of the clay minerals on the equilibrium conditions. The surface energy effects, which are important particularly in the case of claystones with extremely small pores, increase the solubility of gypsum, thus shifting the thermodynamic equilibrium in favour of anhydrite. Clay minerals also favour anhydrite because they lower the activity of the water. The predictions from the model are compared with experimental results and with predictions from other models in the literature. Finally, a comprehensive equilibrium diagram is presented in terms of pore water pressure, solid pressure, temperature, water activity and pore size.
收起
原文获取