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seawater can be estimated on the basis of petrographic and experimental evidence. In thin sections, black-smoker caminite typically fills interstitial spaces between laths of anhydrite (Fig. l), which implies that anhydrite precipi-tates before caminite as seawater heats. The water depth at EPR, 2l'N is roughly 2600 m, corresponding to a hy-
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gypsum contains impurities of anhydrite, calcite, dolomite, and clays. 9 Anhydrite is a rare mineral because it transforms * To whom correspondence should be addressed: Interdisciplinary Nano-
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Anhydrite, a calcium sulfate mineral with the chemical formula CaSO4, possesses a range of chemical, physical, and optical properties. Here are some key characteristics: Chemical Properties: 1. Chemical Formula: CaSO4 – Anhydrite consists of calcium (Ca), sulfur(S), and oxygen (O) atoms. 2. …
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As the anhydrite dosage increased from 15% to 20% and 25%, the setting time of the decreased. The reason is that the formation of ettringite through the reaction of and anhydrite accelerated the formation of a dense microstructure in the cement paste. Adding anhydrite to changes the hydration reaction mechanism.
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Although gypsum, bassanite, and anhydrite are common mineral names, terminology used for Ca-sulfate phases can be complex, particularly in the use of "soluble anhydrite," "g-anhydrite," or ...
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Four phases can be found at room temperature: calcium sulfate dihydrate (gypsum, preferred), anhydrite (in two polymorphs called anhydrite III and anhydrite II), and calcium sulfate hemihydrate. Anhydrite III is metastable and soluble at room temperature as it contains small amounts of crystal water (~1 mol% relative to gypsum), while Anhydrite ...
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When gypsum loses its water component, it forms the mineral anhydrite (CaSO4). When anhydrite absorbs water it becomes gypsum. This ease of exchange is …
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In addition, the hydration and recrystallisation of anhydrite to gypsum can cause considerable expansion and pressures capable of causing uplift and heave. Sulphate-rich water associated with the ...
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Data showed that a stable anhydrite can be produced by heating phosphogypsum at 1000°C. The effects of different chemicals on setting and hardening of anhydrite cement and its hydration characteristics were studied. ... This anhydrite gypsum has higher solubility than Gypsum di hydrate / hemi hydrate gypsum. Usage of the anhydrite gypsum shows ...
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Thus, a long-standing discussion about the thermodynamic aspect of the gypsum-anhydrite conversion can be closed, not the kinetic part. Comparison of the data selection of Shen et al. (2019) and ...
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Microscopic analysis techniques were used to study the effect of anhydrite on the performance and hydration process of under standard curing conditions. The results show that adding an appropriate amount of anhydrite promotes the hydration of . ... Calcium silicate hydrate (C-S-H), calcium hydrate (CH), and calcium sulfoaluminate hydrate ...
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Hydrate compound: Hydrate compounds are chemical compounds with water of crystallization attached to it. For example, Gypsum (CaSO 4. 2 H 2 O), epsom salt (MgSO 4. 7 H 2 O). Anhydrate compound. Anhydrate compound is a chemical compound with no water of crystallization attached to it. For example, Silica gel.
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Strength development and hydrate formation rate. Investigation on anhydrite binders ... obtain an accurate correlation between the strength development and the rate of calcium sulfate dihydrate formation in anhydrite binders. Investigations on the hydration and hardening of anhydrite samples from different origins allows us to point out that ...
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According to British Standards, an anhydrite screeds needs to dry to no more than 75% relative humidity or 0.5 Water by Weight before tiling can commence. To reach this moisture content, the drying time for anhydrite screeds is approximately 1mm per day up to 40mm in ideal conditions – that is where the air temperature is 20°C with a ...
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Download Citation | The hydrothermal decomposition of calcium monosulfoaluminate 14-hydrate to katoite hydrogarnet and β-anhydrite: An in-situ synchrotron X-ray diffraction study | We apply in ...
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The water in hydrates is not merely trapped physically; it's chemically bonded to the host compound. This water can be integral to the compound's stability and appearance. Anhydrates lack these water molecules, which can lead to a significant alteration in their physical characteristics, such as color and form, and in their chemical behavior.
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This sequential reaction can be observed not only with anhydrite but also with hemihydrate and gypsum. Since the solubility rate of gypsum and hemihydrate is increased compared to anhydrite, this sequential reaction occurs much faster. ... The presence of a Ca-containing hydrate can therefore not be completely ruled out. Due to the high w/CA ...
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Gypsum and gypsum plaster products can be made from an anhydrite or mixed anhydrite and gypsum starting material, of natural origin or derived chemically as a byproduct, by mixing the powdered anhydrite with part or all (but not more) of the water necessary for complete hydration to gypsum, compressing the mixture into compacted blocks or other bodies, and allowing the …
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XRD pattern for Alipre clinker, with anhydrite at either 15% or 35% and a w/s ratio of 0.5 or 0.7. Increased ye'elimite hydration can be observed by the decrease of the main peak at 23.7° 2θ with increasing calcium sulfate and water content. Background levels have been reduced, most notably preceding 8° 2θ, in order to generate this figure.
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Gypsum is a hydrate with two water molecules attached to each calcium sulfate unit, making it softer. Anhydrite lacks these water molecules, resulting in a harder mineral. ... Gypsum can transform into anhydrite through dehydration, and anhydrite can rehydrate to form gypsum under the right conditions, highlighting their close relationship. 5.
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At least five crystalline phases can be found in the CaSO 4 -H 2 O system, which are gypsum CaSO 4 · 2H 2 O, the subhydrates Rand -CaSO 4 · 0.5H 2 O, and the soluble and insoluble anhydrite CaSO 4 . The formation of these five phases in the CaSO 4 -H ... Within the 343-383 K thermal range, c-anhydrite has been found to partially re-hydrate to ...
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ChEBI: Calcium sulfate hemihydrate is a calcium salt and a hydrate. General Description. Gypsum is a naturally hydrated calcium sulfate. It can also be easily synthesized in a partially hydrated or anhydrous form. The partially hydrated form is called hemihydrate calcium sulfate, while the anhydrous form is called anhydrite (Jorgensen 1994).
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Three crystalline phases are known in the CaSO 4 –H 2 O system, distinguishable by their degree of hydration: gypsum (CaSO 4 ·2H 2 O), bassanite (CaSO 4 ·0.5H 2 O), and anhydrite (CaSO 4).On Earth, calcium sulfate is mainly encountered as gypsum or anhydrite related with evaporitic environments (e.g. Buick and Dunlop, 1990, Warren, 2006), although …
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The evidence for and against various possible calcium sulphate hydrates is reviewed. The hydrates that exist are calcium sulphate dihydrate CaSO 4 .2H 2 O, calcium sulphate hemihydrate CaSO 4 .1/2H 2 O, and three anhydrous phases : soluble calcium sulphate anhydrite, insoluble calcium sulphate anhydrite, and a high temperature calcium sulphate anhydrite phase. The α- …
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A large amount of gypsum arising in underwater conditions could be dehydrated in anhydrite. These anhydrites have pseudomorph based on gypsum, and often preserve beautiful contours …
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Using X-ray diffraction patterns the dihydrate, hemi-hydrate, soluble anhydrite, and natural anhydrite can be identified. The a- and /3-forms of hemi- hydrate and of soluble anhydrite are not distinguishable from powder diagrams. Natural or insoluble anhydrite has the lowest solubility above 40 of any calcium sulfate modification.
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in the study of gypsum and anhydrite beds, for if estimates of the depth of burial, temperature, and concentration of ground water solutions can be made for these deposits then the stable calcium sulphate phase can be determined. Finally, in an attempt to find some means of cor-relating gypsum and anhydrite zones, a number of differential
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Various forms of calcium sulphate hydrate have been reviewed by Hand [1].Depending on the temperature, calcium sulphate exists as anhydrite (CaSO 4), subhydrate ([2]; CaSO 4.xH 2 O, 0
Different hydrate phase assemblages can be expected to form in dependence of the dry mix composition [6]. ... Thermodynamic modeling presents a powerful tool for the qualitative prediction of the formed hydrate phases in ternary CSA-OPC-anhydrite systems. The modeled stable phase assemblages were already reached after 28d of hydration.
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Hydrate compounds are chemical compounds with water of crystallization attached to it. For example, Gypsum (CaSO 4. 2 H 2 O), epsom salt (MgSO 4. 7 H 2 O). Anhydrate compound is a chemical compound with no water of …
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