This paper briefly describes the results of utilization of natural anhydrite in cement pastes of CEM-I and CEM-II types. The aim of the study has been to inquire the extent of natural gypsum replacement by natural anhydrite. ... Alternative …
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The aim of this paper is to investigate the possible displacement of natural gypsum (CaSO4·2H2O) in cement with an alternative setting retarder, such as the industrial by-product derived from ...
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Experimental results indicated that anhydrite in CFBC ash can be used as an efficient setting retarder but lead to lower mortar strength. The effect is harmless to volume …
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The mineral composition of fluorogypsum is similar to that of natural anhydrite, which can replace natural anhydrite under certain conditions and is mainly used as a cement retarder [13, 14], but ...
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The natural anhydrite permeability characteristics based on the Katz-Thompson model are size-dependent, with a favorable fit to the thermal fractal dimension of the small pore size range under the k = aD b model, i.e., the larger the fractal dimension, the lower the permeability coefficient. This finding offers new theoretical basis into the ...
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In China, more and more cement factories are trying to use the chemical gypsums as a cement retarder instead of natural gypsum (NG). Cement is the most massive man-made material, 0.04–0.08 ton of gypsum is needed to produce 1 ton of cement, and there were around 1.5 billion tons of cement produced in China in 2008.
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This paper briefly describes the results of utilization of natural anhydrite in cement pastes of CEM-I and CEM-II types. The aim of the study has been to inquire the extent of natural gypsum replacement by natural anhydrite. ... The experimental data conclude that natural anhydrite can be a very efficient retarder of the setting of cement, with ...
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clinker blended with 10 wt.-% of the natural anhydrite (labelled CAH). ... were tested at a single addition rate of 0.5 % by cement weight. The impact of retarders was evaluated by measuring the ...
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Taking China's production of 2.377 billion tons of cement in 2020 as an example, and if phosphogypsum modified by CFB fly ash and carbide slag is used as a retarder, around 95.08 million tons of natural gypsum can be saved; in addition, approximately 85.57 million tons of phosphogypsum, 5.7 million tons of carbide slag, and 3.8 million tons of ...
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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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The most common cement setting retarder used in industry is natural gypsum, which is primarily a dihydrated product of calcium sulfate (CaSO 4 · 2H 2 O). The need for gypsum in cement increases with increasing amount of C 3 A and alkalies in the clinker and the fineness of the cement [1], [2], [3]. Gypsum also promotes cement strength at an optimum …
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Manufacturing of Portland cement consumes huge amounts of both energy and natural raw materials and is one of the main emitters of CO 2.According to World Cement Association estimations, 2018 global cement production will only slightly increase compared to 2017 (4.2 billion tonnes [1] compared to 4.1 billion tonnes [2]).In the same year, the total CO 2 …
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The experimental data conclude that natural anhydrite can be a very efficient retarder of the setting of cement, with no significant change in the physicomechanical properties of the hardened ...
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Cement retarder preparation is one of the main avenues for the resource utilization of phosphogypsum, and appropriate modification technology is the key for ensuring that the phosphogypsum is adjusted for achieving the desired setting time. ... Compared with the cement prepared with natural gypsum, the 28 d compressive strength and flexural ...
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natural stone aztec gold factury - Jaw crusher: PE series jaw ..., natural anhydrite as cement retarder; natural sand drying system; natural stone quarries in india; grinding stone chakki of natural stone rough surface; Randome Posting. Go to Product Center. TAIHEIYO International (Thailand) Co., Ltd., ...
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Gypsum (CaSO 4 ·2H 2 O) and/or natural anhydrite (CaSO 4) are usually added to clinker in the grinding stage.Depending on the temperature reached on the mill, the gypsum may dehydrate in hemihydrate (CaSO 4.1/2H 2 O) and/or soluble anhydrite (CaSO 4), which are more soluble and, therefore, will influence the cement hydration [3].In this paper, the term "calcium …
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US Patent # 4,670,055. Method for quick setting of a pourable ..., The natural anhydrite plays only a minor ... The additive can also be produced after the addition of the premixture composed of the alumina cement and retarders.
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The experimental data conclude that natural anhydrite can be a very efficient retarder of the setting of cement, with no significant change in the physicomechanical properties of the …
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The experimental data conclude that natural anhydrite can be a very efficient retarder of the setting of cement, with no significant change in the physicomechanical properties of the hardened ...
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The experimental data conclude that natural anhydrite can be a very efficient retarder of the setting of cement, with no significant change in the physicomechanical properties of the hardened ...
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The totally anhydrous form known as -anhydrite or "natural" anhydrite is generated when heated over 250 °C. Unless very finely crushed, natural anhydrite does not react with water over geological timeframes. ... and 5.4 million tons was used mostly as a cement retarder or as agricultural land plaster, out of a total supply of 24.5 million ...
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In Portland cement, usually natural gypsum is added to act as an effective retarder controlling the hydration of the C 3 A phase [10]. Tzouvalas et al. have investigated the replacement of natural gypsum with natural anhydrite and by-product gypsum [11], [12].
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Various by-product gypsum such as phosphor-, fluoro-, citro-, boro-, titano-, tartare-, and desulphogypsum have chemical composition similar to the natural gypsum, but its use in replacing natural gypsum as cement retarder is limited, mainly due to the variation of moisture and impurities content that can affect the cement workability [4], [5], [6], [7].
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Use of inorganic setting retarders in cement industry. Aris Papageorgiou. 2005, Cement and Concrete Composites. See full PDF download Download PDF. Related papers. Alternative calcium sulfate-bearing materials as cement retarders. Nikitas Dermatas, S. Tsimas. Cement and Concrete Research, 2004.
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1.. IntroductionThe setting behaviour of cement is mainly due to the reaction of tricalcium aluminate (C 3 A), 3CaO · Al 2 O 3.The reaction of pure C 3 A with water leads to immediate stiffening of the paste, known as flash set. Thus, gypsum is added to the cement clinker during the grinding of Portland cement to retard the rapid reaction between C 3 A and …
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With desulfurization technology developing, the content of anhydrite in fly ash and CFBC ash has been an upward trend [7]. In order to use industrial wastes with high content of anhydrite in cement, many researchers try to make cement with no or less added gypsum and use anhydrite in wastes as cement setting retarder instead of added gypsum.
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However, due to environmental concerns and the lack of natural deposits of gypsum, various gypsum by-products, such as phosphor-, citro-, desulpho-, boro- and FGD gypsum, are used as setting retarders to replace the natural gypsum (Papageorgiou et al., 2005, Kavas et al., 2005, Ozkul, 2000, Tzouvalas et al., 2004).
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The experimental data conclude that natural anhydrite can be a very efficient retarder of the setting of cement, with no significant change in the physicomechanical properties of the hardened pastes. (C) 2004 Elsevier Ltd.
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stability and hydration process. Experimental results indicated that anhydrite in CFBC ash can be used as an efficient setting retarder but lead to lower mortar strength. The effect is harmless to volume stability of cement paste with appropriate anhydrite addition. Compared with natural gypsum, anhydrite
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In the process of cement production a certain amount of gypsum is added in order to adjust setting time of cement, contribute for strength acceleration in early stage and reduce drying shrinkage of hardened cement paste [1], [2], [3].In Portland cement, usually the added gypsum is natural dihydrate gypsum, but mixed gypsum and chemical gypsum are also used in cement …
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In China, more and more cement factories are trying to use the chemical gypsums as a cement retarder instead of natural gypsum (NG). Cement is the most massive man-made material, 0.04–0.08 ton of gypsum is needed to produce 1 ton of cement, and there were around 1.5 billion tons of cement produced in China in 2008. ... and anhydrite and ...
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This paper briefly describes the results of utilization of natural anhydrite in cement pastes of CEM-I and CEM-II types. The aim of the study has been to inquire the extent of natural gypsum replacement by natural anhydrite. ... Alternative calcium sulfate-bearing materials as cement retarders Part I. Anhydrite // Cement and Concrete Research ...
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This article reports on a study of the displacement of natural gypsum (CaSO4-2H2O) in cement with an alternative setting retarder, such as the industrial by-product derived from flue gas desulfurization process called FGD gypsum. ... Portland cement; Retarders (Concrete); Setting (Concrete) Subject Areas: Highways; Materials; I32: Concrete ...
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retarder for Portland cement. It is added to the clinker at the cement grinding stage, usually at a concentration of 5–6%, depending on its purity. The use of phosphogypsum to replace natural ...
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Various modification and activation methods, such as grinding, heat treatment, and salt activation, have been developed because of the ongoing research of domestic and international scholars. The natural anhydrite-based cementitious materials prepared using these methods are also called "green cement".
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