Natural Anhydrite As Cement Retarder

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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Investigations of anhydrite in CFBC fly ash as cement retarders

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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Researches into Possibility of Application of Lithuanian Anhydrite

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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Alternative Calcium Sulfate-Bearing Materials as Cement Retarders

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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Effects of sulfates on the hydration of Portland cement – A review

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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ALTERNATIVE CALCIUM SULFATE-BEARING MATERIALS AS CEMENT RETARDERS…

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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Effect of retarders on the early performance of CSA-type …

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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Using gypsum to control hydration kinetics of CSA cements

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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Effect of protogenetic anhydrite on the hydration of cement under

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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natural anhydrite as cement retarder

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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Purification of South African phosphogypsum for use …

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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Investigations of anhydrite in CFBC fly ash as cement retarders

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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Alternative Calcium Sulfate-Bearing Materials as Cement Retarders

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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Pore structure characteristics and permeability analysis of natural

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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Modification of fluorgypsum as cement retarder

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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Analysis of anhydrite's effects on quality of cement

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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CN115368101A

The invention relates to the technical field of building materials, and discloses natural anhydrite self-leveling anti-crack mortar which comprises the following ingredients, wherein the ingredients comprise natural anhydrite, water, sand, cement, fibers, a water retaining agent, a retarder, a water reducing agent, a deing agent, an exciting agent and a plasticizer, the raw …

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Alternative calcium sulfate-bearing materials as cement retarders: …

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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Characterization of a more sustainable cement produced with …

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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Tartaric acid effects on hydration development and physico-mechanical

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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ALTERNATIVE CALCIUM SULFATE-BEARING MATERIALS AS …

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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Influence of Anhydrite on the Properties and Microstructure of

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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Alternative calcium sulfate-bearing materials as …

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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Economically the Sivas Basin Natural Anhydrite Potential, …

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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Analysis of anhydrite gypsum effects on quality of …

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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Modification of phosphogypsum using circulating fluidized bed fly …

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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natural anhydrite as cement retarder

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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Use of waste gypsum to replace natural gypsum as set retarders …

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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Technical feasibility for use of FGD gypsum as an additive setting …

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 waste gypsum to replace natural gypsum as set retarders …

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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