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Use of inorganic setting retarders in cement industry
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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Investigations of anhydrite in CFBC fly ash as cement retarders
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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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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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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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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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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Modification of phosphogypsum using circulating fluidized bed fly …
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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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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Calcium Sulfate (Properties, Uses)
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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(PDF) Anhydrite vs Gypsum: Impact on Cement Quality
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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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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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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natural anhydrite as cement retarder
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Use of inorganic setting retarders in cement industry
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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Investigations of anhydrite in CFBC fly ash as cement retarders
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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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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ALTERNATIVE CALCIUM SULFATE-BEARING MATERIALS AS CEMENT RETARDERS…
Substances that regulate the setting of cement, such as natural anhydrite, have attracted significant scientific interest during the past years. 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 inquire ...
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(PDF) BELICEM CSA CEMENT
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
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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Modification of waste fluorgypsum and its applications as a cement retarder
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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Purification of South African phosphogypsum for use as …
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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Effect of protogenetic anhydrite on the hydration of cement under
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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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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Pore structure characteristics and permeability analysis of natural
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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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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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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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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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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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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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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