gypsum dehydration cement

gypsum dehydration - page 1 of 1

gypsum dehydration - page 1 of 1

Gypsum dehydration is necessary for it to become an effective set moderating agent. Gypsum itself is insolouble and therefore cannot moderate the setting of the C3A in cement clinker. For that to happen soluble sulphate must be present. Dehydration of gypsum to hemihydrate renders it soluble.

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the thermal dehydration of synthetic gypsum - sciencedirect

the thermal dehydration of synthetic gypsum - sciencedirect

Mass losses vary between 13.7 and 16.5% and heat of dehydration values between 377 and 420 J g1 for the dehydration of ground and mixed inhomogeneous gypsum samples. As for the dehydration of CaSO42H2O, the dehydration of synthetic gypsum proceeds via multi-step reactions. Using a heating rate of 5C min1, the very slow dehydration of CaSO42H2O and impurities in the gypsum samples start at temperatures lower than 95C. The main dehydration of the calcium sulphate dehydrate part of synthetic gypsum occurs between 95 and 170C (heating rate 5C min1) and seems to proceed via a process with an activation energy of 392 100 kJ mol1 for -values between 0 and 0.1. For -values between 0.1 and 0.7, the reaction can be described by a first-order process with autocatalysis with an activation energy value of 100.5 1.2 kJ mol1. The third part of the reaction (0.7 < < 1), up to temperatures of 180C, gives an activation energy value of 96 15 kJ mol1. Even at temperatures above 250C, some CaSO4O.15H2O was still observed. The dehydration of calcium hemihydrate seems to proceed via the formation of CaSO40.15H2O.

gypsum content determination in portland cements by thermogravimetry | springerlink

gypsum content determination in portland cements by thermogravimetry | springerlink

Gypsum quantitative determination in cements may be done from their thermogravimetric analysis (TG) data, which uses the mass of the water released from its gypsum dehydration during cement analysis, to determinate its content stoichiometrically. Depending on the operational conditions used to mill the gypsum with clinker, its partial dehydration may occur, which leads to unreal results when only unhydrated cement TG data are used. To solve this problem, TG analysis of the 1-h paste of respective cement must be done on respective initial cement mass basis. The method was applied to four different classes of Portland cements, showing that for all of them, the application of the method was needed to avoid erroneous determinations. As mineral composition data show that the cements have other sulfated phases, different from gypsum and its dehydration phases, the total cement SO3 content cannot be used directly to quantify gypsum. However, using the present suggested thermogravimetric method, the original gypsum content can be determined, which also estimates and includes the amount which was consumed to form ettringite during the first hour of hydration.

Dweck J, Aderne RS. The effect of the presence of pozzolanic material in the solidification of a tannery waste. In: Proceedings of III seminar on pollution prevention and control DEQ/EPUSP, So Paulo, 2007. p. 2029 (in Portuguese).

Silva DM, Alberoni VG, Dweck J, Yokoyama L. A thermal analysis study of the stabilization/solidification of a waste containing aluminum. In: Proceedings of II seminar on pollution prevention and control DEQ/EPUSP, So Paulo, 2005. p. 17 (in Portuguese).

Melchert MBM, Viana MM, Lemos MS, Dweck J, Bchler PM. Simultaneous solidification of two catalyst wastes and their effect on the early stages of cement hydration. J Therm Anal Calorim. 2011;105(2):62533.

Dweck J. Gypsum moldsa micro-processed system to determinate the Plaster of Paris hydration time and the water absorption rate. In: Proceedings of 39th Braz. Ceram. Congress. guas de Lindia, Brazil 1995. p. 10521057 (in Portuguese).

Neves A Jr, ToledoFilho RD, Fairbaim EMR, Dweck J. Early stages hydration of high initial strength Portland cement, Part I. Thermogravimetric analysis on calcined mass basis. J Therm Anal Calorim. 2012;108:72531.

Dweck J, Melchert MB, Viana MM, Cartledge FK, Bchler PM. Importance of quantitative thermogravimetry on initial cement mass basis to evaluate the hydration of cement pastes and mortars. J Therm Anal Calorim. 2013;111(3):110.

Jo, D., Leonardo, R.S., Cartledge, F.K. et al. Gypsum content determination in Portland cements by thermogravimetry. J Therm Anal Calorim 123, 10531062 (2016). https://doi.org/10.1007/s10973-015-5078-y

21 difference between gypsum plaster and cement plaster | what is gypsum plaster | what is cement plaster

21 difference between gypsum plaster and cement plaster | what is gypsum plaster | what is cement plaster

Gypsum plaster ismade by heating gypsum at low temperaturesto drive off water, toproduce plasterof Paris a chalky, fast-setting material commonly used formolds and for casts to repair broken bones.

Gypsum plaster, white cementing material made by partial or complete dehydration of the mineralgypsum, commonly with special retarders or hardeners added. Applied in a plastic state (with water), it sets and hardens by chemical recombination of the gypsumwith water.

Gypsum is a soft sulfate mineral composed of Calcium sulfate dihydrate (CaSO4:2H20). It is widely used as a fertilized, in mould, in sculptures, and asplaster material. Gypsum although a much older material than cement & sandplaster has rarely been used extensively in the construction industry.

Gypsum (composed of crystallized calcium sulfate (CaSO4) is added to Portland cement to regulate the extreme setting reaction which occurs in the presence ofwater. The gypsum content of cement is expressed in terms of its sulphate (SO3) content.

Gypsum plaster, white cementing material made by partial or complete dehydration of the mineralgypsum, commonly with special retarders or hardeners added. Applied in a plastic state (with water), it sets and hardens by chemical recombination of the gypsumwith water.

Cement plaster can be used on exterior and interior surfaces. Whereasgypsum plaster can only be used on the ceiling and interior walls it cannot be used in wet areas like toilet bath kitchen wash area balconies etc. Whereas gypsum plastergives a very smooth finish which makes it compatible with paints.

The application ofgypsum plasteris a time-saving process thus decreases the projectcost. Nowadays river sand availability is a major problem and rivers and has become costly hencecement plasteris costlier thangypsum plaster.Gypsum plasteris cheaper as compared tocement plaster.

Ingypsum plaster, readymade POP powder is mixed with water and applied directly to the wall.Gypsum Plastercan be applied directly on any brick, solid or hollow blocks, AAC blocks andplasterboards.Gypsum plaster has good insulation properties, fire-resistant and impact resistant.

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