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50 % RH. The gypsum has a very low moisture content of 6.10-4 m 3 m-3. 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 0.4 % of the total water content.
If gypsum wallboard, ½ inch (12.7 mm) thick, could be made solely from stucco, the weight would be ~5,500 lbs./MSF (26.9 kg/m2) When this size board is made with stucco and water, the weight would be ~2,700 lbs./MSF (13.2 kg/m2) Water of hydration and excess water are needed to make the gypsum slurry fluid enough to form the board
best suited technique where weight loss as function of temperature allows estimation of water content in percentage. Generally bound water would evolve at high temperature compared to free water as large energy is required to break the crystal structure and release the water. This allows separation of free and bound water, for further
A process is provided for recovering phosphoric acid from phospho gypsum produced as a by-product 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 ...
Oct 06, 2013· Arizona Instrument manufactures the Computrac® MAX® 5000XL, a high temperature rapid loss-on-drying 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.
20.9% 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 ...
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.
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 ...
• Chemically bound water is driven out by heat. • Gypsum wallboard reacts to fire in predictable manner – First paper burns off, then color changes • Rate and depth do not indicate burn times. 4 Glass Effects (1 of 3) • Glass deposits free of soot usually indicate
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 .
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 ...
Results indicated that at temperatures up to 200 o C, the gypsum boards (both PCM-GB and S-GB) act as fire retardants because of the dehydration of the contained free and chemically bound water.
Excess water needed above 18.6 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) ...
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
1. hemihydrate mixes with water and forms a thick fluid suspension [ hemihydrate is MORE SOLUBLE than dihydrate] "Hemihydrate is soluble in water at the rate of 0.8g/100 ml.This compares with dihydrate which is only soluble in water at the rate of 0.2g/100 ml." 2. as the hemihydrate dissolves, a saturated solution forms--> since dihydrate is LESS SOLUBLE than the hemihydrate, the dihydrate ...
2.2. 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 (≈1.1% 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 .
wn is the chemically bound water at complete hydration of the cement quantity c. The quotient wn /c 0 varies between about 0.18 and 0.26 depending on the composition of the cement; [1]. Often the value 0.25 is used. ... Gypsum added to the cement clinker in connection with grinding of this (about 5 .
weight loss during the temperature scan (10°C/min). From this temperature scan, it becomes evident that the bulk of the free moisture evolves at approximately 80 °C, while the bound moisture (which is indicative of the gypsum purity) evolves at 240°C. The MAX® 5000XL allows the user to have
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 ...
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 ...
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.
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.
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 corrosion-technical point of view, contacts of metals and mineral building materials that are produced with cement and gypsum play an important role.
Gypsum is moderately water-soluble (~2.0–2.5 g/l at 25 °C) and, in contrast to most other salts, it exhibits retrograde solubility, becoming less soluble at higher temperatures. When gypsum is heated in air it loses water and converts first to calcium sulfate hemihydrate, (bassanite, often simply called "plaster") and, if heated further, to anhydrous calcium sulfate (anhydrite).
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