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Jun 29, 2019· Its chemical formula is CaSO 4 ·2H 2 O. Gypsum contains calcium, sulfur bound to oxygen and water. It is an abundant mineral and widely mined. In structural engineering, from a corrosiontechnical point of view, contacts of metals and mineral building materials that are produced with cement and gypsum play an important role.
If gypsum wallboard, ½ inch ( mm) thick, could be made solely from stucco, the weight would be ~5,500 lbs./MSF ( kg/m2) When this size board is made with stucco and water, the weight would be ~2,700 lbs./MSF ( kg/m2) Water of hydration and excess water are needed to make the gypsum slurry fluid enough to form the board
First of all, gypsum board products have a certain level of water in the paper, and water is chemically bound into the gypsum itself. Under normal circumstances, this water is not detrimental to the performance of the gypsum board. It is well known that gypsum board products are subject to damage by water and high humidity.
Results indicated that at temperatures up to 200 o C, the gypsum boards (both PCMGB and SGB) act as fire retardants because of the dehydration of the contained free and chemically bound water.
The chemical kinetics of three main reactions that take place when a gypsum board is exposed at elevated temperatures: evaporation of free moisture content, dehydration of chemically bound water and crystal mesh reorganization were investigated using Differential Scanning Calorimetry measurements under non isothermal conditions and in an inert ...
A process is provided for recovering phosphoric acid from phospho gypsum produced as a byproduct in a phosphoric acid production process and having water soluble P 2 O 5 bound in the crystal lattice thereof. The process includes a) forming a suspension of phospho gypsum in an aqueous medium; b) subjecting the suspension to ultrasonic waves under conditions suitable to shatter the phospho ...
The water can be classified as free and bound water. The water which does not have any Interaction with materials and melted at OOC is called free water. The water which is not frozen at mmus temperature region or start melting below OOC due to the interactions with materials is called bound water.
Oct 06, 2013· Arizona Instrument manufactures the Computrac® MAX® 5000XL, a high temperature rapid lossondrying analyzer that is capable of heating samples to 600°C, and can start testing at room temperature, making it an ideal candidate for testing gypsum for free and bound moisture.
The chemical kinetics of three main reactions that take place when a gypsum board is exposed at elevated temperatures: evaporation of free moisture content, dehydration of chemically bound water and crystal mesh reorganization were investigated using Differential Scanning Calorimetry measurements under non isothermal conditions and in an inert ...
May 02, 2019· The ovens cause the free water in gypsum panels to evaporate thus enabling the moisture content to be calculated by the difference in weight of the specimen before and after its exposure to heat. If the ovens are improperly operated, causing the temperature to go too high or the sample to heat for too long, the water of hydration that is part ...
floors, due to the endothermic gypsum dehydration process that takes place in high temperature. When a gypsum board is subjected to fire, the free and chemically bound water is released and transferred through the board, absorbing energy and thus reducing the mean wall temperature. This phenomenon can be of great importance from the safety point
Free and Bound Moisture in Gypsum Quickly determine gypsum purity. If you work with gypsum, you know how crucial moisture measurement is to making a highquality product. Computrac® understands; that''s why Computrac has been the de facto industry standard for moisture measurement in gypsum .
laminated surfaces which provide tensile strength to the lining. Gypsum contains chemically bound water and a small amount of free water, which play a key role in the performance of the assembly at elevated temperatures. During a fire, when gypsum board is heated up to about 100°C, a great amount of heat is absorbed to drive off water.
Pure Gypsum, known as Calcium sulphate dihydrate (CaSO 4 .2H 2 O), consists of Calcium sulphate with 45% of free water and 1518% chemically bound water by weight [2] [3][4][5][6][7]. The free ...
When gypsum boards are heated to temperatures above 80 degrees C, the chemically bound water dissociates from the crystal lattice and, together with the free moisture, evaporates. This process, known as "dehydration" of gypsum, and takes place at temperatures between ~80 .
In its natural state, gypsum contains the water of crystallization bound in the form of hydrates. When exposed to heat or fire, this water is vaporized, over a range of temperatures from 80 to 170 °C (176 to 338 °F) (see calcium sulphate ), retarding heat transfer until the water in the gypsum is gone.
Gypsum "dehydration" phenomena, occurring when gypsum plasterboard wall assemblies are exposed to a high temperature environment, result in water vapour production and subsequent dispersion in ...
The existing standard ASTM C471 Standard Test Methods for Chemical Analysis of Gypsum and Gypsum Products describes manual gravimetric analytical methods for evaluating the free and combined water of gypsum materials, including natural gypsum, synthetic gypsum, rehydrated plasters, and gypsum .
50 % RH. The gypsum has a very low moisture content of m 3 m3. This relative humidity was chosen close to the average humidity in a building. Compared to the amount of chemically bound water in gypsum, the free water content is only % of the total water content.
VARIATIONS within the normal range of temperature do not exert a very profound effect upon the rate of hydration of gypsum plaster1,2. For example, Fig. 1 shows the maximum rate of increase of ...
At temperatures up to 300°C, the materials act as a fire retardant because of the dehydration of the free and chemically bound water contained in the gypsum boards. On the other hand, at temperatures higher than 300°C, the temperature rise within the samples is enhanced and accelerated because of the oxidation of the phase change material and ...
% chemically bound water (H 2O). However, since gypsum is a natural material, pure gypsum is rarely found. ... product then rehardens to gypsum (dihydrate). The excess free water evaporates or can be removed by gentle drying at low temperatures ... precise temperature control and fast, homogenous drying, and the robust ...
Thermochemistry of gypsum fibre Gypsum fibre is a material made of calcium sulphate and water. In a first step, around 100°C, the free water evaporates (≈% of the mass). In a second step, between 120 up to 220°C, the chemically bound water dissociates from the crystal lattice and evaporates (≈24% of .
Excess water needed above mL that is not bound to the calcium sulfate dihydrate and is free to evaporate? ... Strength of gypsum BEFORE Free Water has evaporated? Wet Strength, 1/2 dry strength ... temp of water 2) temp and humidity of environment 3) the type of alginate used (regular or fast set) ...
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