The experimental data conclude that natural anhydrite can be a very efficient retarder of the setting of cement, with no significant change in 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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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. ... Alternative …
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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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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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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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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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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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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 experimental data conclude that natural anhydrite can be a very efficient retarder of the setting of cement, with no significant change in the physicomechanical …
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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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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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The anhydrite in CFBC ash is a suitable alternative to gypsum to act as an efficient retarder of the setting of cement based on the setting results but lead to lower strength of the …
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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 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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The cement test proved that treated PG could partially replace natural gypsum as a retarder.Keywords: phosphogypsum treatment, phosphorus pentoxide removal, calcium sulfate transition phase ...
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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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Compared with the added gypsum, protogenetic anhydrite is the anhydrite in clinker and cement admixture. And using protogenetic anhydrite as the setting retarder instead of …
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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.
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Fluorgypsum belongs to Ⅱ-anhydrite, its hydrated speed is very slow, its dissolution speed is slower than that of calcium sulphate dihydrate in water. If fluorgypsum is directly added as a cement retarder, this cement be "false coagulated". In addition, the grain size of fluorgypsum is very small, affecting the materials' transportation.
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The aim of this paper is to investigate the possible displacement of natural gypsum in cement with anhydrite in CFBC ash in terms of setting time, strength development, volume stability and ...
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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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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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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 pastes with hemihydrates also present a higher amount of hydrated sulfoaluminate phases, mainly monosulfoaluminate formations, than those with dihydrates [27]. The use of natural anhydrite as set retarder has been also studied, and the reduction of strengths in the first three days was the main difference found [7].
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of the study, it was stated that natural anhydrite added to concrete mixtures at certain ratios increased the strength and showed linking properties by acting like cement [2]. In the cement industry, calcium sulphate (gypsum or anhydrite) is one of the components of Portland cement that increases the time required for setting [11].
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This article reports on the use of alternative calcium sulfate-bearing materials, notably anhydrite, as cement retarders in cement pastes of CEM-I and CEM-II types. The aim of the study is to …
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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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