Study with Quizlet and memorize flashcards containing terms like Which of the following is true concerning the chemical properties of gypsum materials? a. Chemically, the mineral gypsum is a hemihydrate of calcium carbonate. b. To form the raw material into a powder, the manufacturer heats it and adds water. c. When the dihydrate is again mixed with …
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Therefore, the mechanism of the HH-CSW formation from gypsum should be such that the two Ca–O–H bonds broken in the gypsum structure release H 2 O and bond with the two S-formed novel Ca–O–S bonds, along the c-axis of the H 2 O released. 1/2 water molecule in HH-CSW structure is held to the sulphate ion by hydrogen …
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The apparent empirical activation energies (Ea) suggest that the transition from gypsum to hemihydrate is mainly controlled by nucleation and growth …
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Furthermore, within a deeper layer of the crystal, new crystals become visible but disappear during dehydration of the upper layers. These are expected to be α-hemihydrate. This theory of the formation of α …
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Flue-gas desulphurization (FGD) gypsum is a highly prevalent industrial by-product worldwide, which can be an excellent alternative to natural gypsum due to its high content of CaSO4·2H2O. The preparation of α-calcium sulfate hemihydrate is a high-value pathway for the efficient use of FGD gypsum. Here, a dynamic method, or an improved …
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hemihydrate gypsum, and the influence degree of different forms of soluble phosphorus is unclear. Therefore, the utilization of a-hemihydrate gypsum is greatly limited. In this study, the effect of soluble phosphorus on the setting time and mechanical properties of a-hemihydrate gypsum was investi-gated by adding different amounts of H 3PO 4 ...
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1. Introduction. Gypsum plaster, also known as plaster of Paris, is one of the earliest materials used for construction [1], [2], [3], whose use can be traced back to several thousands of years ago.Now, it is still primarily used for indoor applications owing to a whole bunch of advantageous attributes, such as easy fabrication feature, thermal …
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Using solar energy to dehydrate gypsum to produce β-hemihydrate is one way to improve the carbon footprint 13,14 . Alternatively, α-hemihydrate is produced from gypsum using an autoclave process ...
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α-Calcium sulfate hemihydrate (α-HH) is an important cementitious material, which can be prepared by hydrothermal method from calcium sulfate dihydrate (DH) in an electrolyte solution. Study of the …
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The apparent empirical activation energies (Ea) suggest that the transition from gypsum to hemihydrate is mainly controlled by nucleation and growth mechanism, while the transition from gypsum to γ-anhydrite is mostly followed by phase boundary mechanism. ... Impact of limestone fineness on cement hydration at early age. Cement …
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Whereas control specimens based on hemihydrate binder has higher level of shrinkage (up to 0.08 mm/m) with subsequent achieving …
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Due to its excellent cementitious properties and higher strength, α-calcium sulfate hemihydrate (HH: CaSO 4 ·0.5H 2 O), traditionally known as "plaster of Paris", is widely used in modern construction and ceramics industries [3], [4].Currently, it is commercially produced by dehydration of natural gypsum, or from flue gas …
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Calcium sulfate whiskers (CSWs) are columnar crystalline synthetic microfibers with excellent heat resistance, high elastic modulus, and good processability [20], [21].CSWs not only offer the advantages of a fiber and inorganic filler, but also have the same chemical composition as that of the gypsum matrix, which results in good …
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Phosphogypsum can be used to prepare β-hemihydrate gypsum (β-CaSO4·1/2H2O) plaster. A prerequisite for any effective reuse of phosphogypsum is to understanded the act by which impurities in ...
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The applications of gypsum in China are primarily twofold: the preparation of high-strength gypsum, construction gypsum, composite cementing materials, and others, and the preparation of gypsum building products like gypsum board and gypsum blocks. Among these, α-hemihydrate gypsum (α-HH) is a high-end gypsum product, mainly …
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Gypsum is a naturally occurring mineral that has been used by humans for various purposes for thousands of years. It is a versatile mineral with a wide range of applications in construction, agriculture, industry, and even art. In this introduction, we'll explore the definition and composition of gypsum.
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1. Introduction. Flue gas desulphurization gypsum (FGD gypsum) is an industrial byproduct generated during the desulphurization and purification processes of power plant flue gas emissions [1].This byproduct is primarily comprised of calcium sulfate dihydrate (CaSO 4 ·2H 2 O, DH), along with minor impurities and a high moisture …
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Flue gas gypsum may be converted to α-hemihydrate by suspending the starting material in inorganic salt solutions of high concentration or in diluted sulfuric acid and maintaining the suspension at boiling, or near boiling temperature for a period of time. The crystal morphology of the produced α-hemihydrate gypsum and, thus, its quality …
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Phosphogypsum can be used to prepare β-hemihydrate gypsum (β-CaSO 4 ·1/2H 2 O) plaster. A prerequisite for any effective reuse of phosphogypsum is to understanded the act by which impurities in phosphogypsum influence the performance of β-CaSO 4 ·1/2H 2 O plaster, and the role NaF was explored in this study. The results …
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The synthesis of α-calcium sulfate hemihydrate (α-CSH) from flue gas desulfurization (FGD) gypsum is a good way to realize the comprehensive utilization of FGD gypsum. To obtain α-CSH with the satisfactory performances, a facile hydrothermal-aging pretreatment process for FGD gypsum raw materials was proposed, where FGD …
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The polyvinyl alcohol (PVA) reinforced macro-defect-free α-hemihydrate gypsum composite (PMC) was prepared by compression molding technique. The mechanical strength from the age of 3 d to 120 d and water resistance of PMC were tested, and the phase composition, microstructure, pore structure of PMC was characterized by …
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Pouring time should be controlled in the time before α-hemihydrate decorative gypsum hydration, and the pouring temperature can be slightly lower than the autoclave temperature.
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CAH 10 and C 28 are the main hydration products in CAC and they are responsible for its high strength at the early age [9]. ... Dihydrate and β-hemihydrate gypsum exhibit relatively higher solubility and dissolve more quickly than CaSO 4. However, there is little information on their incorporation in CAC.
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The results showed that as soon as a stable gypsum nucleus is formed, hemihydrate hydration will proceed to its end and all the hemihydrate will become …
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Calcium sulfate occurs in nature in form of three different minerals distinguished by the degree of hydration: gypsum (CaSO4·2H2O), hemihydrate (CaSO4·0.5H2O) and anhydrite (CaSO4).
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Calcium sulphate dihydrate (CaSO4·2H2O or gypsum) is used widely as building material because of its excellent fire resistance, aesthetics, and low price. Hemihydrate …
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Containment of sulfate in leachate as gypsum (CaSO 4 ·2H 2 O) mineral formation in bio-cemented sand via enzyme-induced carbonate precipitation
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Gypsum is the name given to a mineral categorized as calcium sulfate mineral, and its chemical formula is calcium sulfate dihydrate, CaSO 4 ⋅ 2H 2 O. However, a broader definition includes all the calcium sulfates, including calcium sulfate hemihydrate, CaSO 4 ⋅ 0.5H 2 O, which is known as plaster or plaster of Paris (POP).
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Phosphogypsum can be used to prepare β-hemihydrate gypsum (β-CaSO 4 ·1/2H 2 O) plaster.A prerequisite for any effective reuse of phosphogypsum is to understanded the act by which impurities in phosphogypsum influence the performance of β-CaSO 4 ·1/2H 2 O plaster, and the role NaF was explored in this study. The results …
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The dehydration of gypsum to hemihydrate has been studied for decades because it is an important model reaction for understanding fluid-triggered earthquakes, …
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Calcium sulfate hemihydrate whiskers (CSHWs) were prepared from high-purity salt gypsum in a glycerol–water system. The effects of the glycerol/water ratio, reaction temperature, reaction time, and stirring speed on the crystal morphology of the CSHWs were investigated.
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DOI: 10.1016/j.conbuildmat.2023.130453 Corpus ID: 256217243; Utilization of phosphogypsum to synthesize α-hemihydrate gypsum in H3PO4–H2O solution @article{Chen2023UtilizationOP, title={Utilization of phosphogypsum to synthesize $alpha$-hemihydrate gypsum in H3PO4–H2O solution}, author={Long Chen and Lin …
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The effects of phosphoric acid (H3PO4) in pressurized aqueous solution on the dehydration of CaSO4·2H2O to form α-hemihydrate gypsum (α-HH) phase and the …
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