The total cost of gypsum in Australia 2. Therefore, if properly characterized, a calcination depth profile of a given enclosure could provide fire investigators with a detailed history of the total heat exposure to the walls and ceiling of the space. However, calcination is also used to mean a thermal treatment process in the absence or limited supply of air or oxygen applied to ores and other solid materials to bring about a thermal decomposition. As such, a moisture meter calibrated using the techniques commonly applied for wood can yield misleading results for quantifying the moisture content of a gypsum panel. Stone is made from gypsum by carefully controlled calcination under steam pressure in a closed container. ORTHOROMBIC ANHYDRATE. googletag.cmd.push(function() { googletag.display('div-gpt-ad-1449240174198-2'); }); Michael F. Bräu (BASF Construction Chemicals GmbH) and Horst Weiss (BASF SE) have now brought this speculation to an end: by using single-crystal structural analyses they were able to solve the structure, generate a structural model, and support it with computer calculations. A moisture meter properly calibrated for the specific material being measured can provide useful data on a wide variety of materials. On subsequent addition of water to stucco, it will return to a rock-like calcium sulfate dihydrate. f) Burning the composition in a kiln to form clinkers. Gypsum panels can occasionally be subjected to moisture. 19, 3520-3524, doi: 10.1002/anie.200900726. ... or an autoclave , the process is called wet calcination. Apart from any fair dealing for the purpose of private study or research, no Usually in the process, the temperature is also regulated. We are a distinguished manufacturer and exporter of Gypsum Calcination Plant. Calcination refers to heating a solid to high temperatures in absence of air or oxygen, generally for the purpose of removing impurities or volatile substances. Paper and glass facings will have a different response to changes in the environment than the gypsum core resulting in different moisture levels for the materials. a) Raw material extraction. Answers to many of these questions are found in an Association document revised in 2019, GA-231 Assessing Water Damage to Gypsum Board. They are packed in so tightly that no further water molecules can enter into the channels of the basic structure. In addition, these materials may be dissolved in the water and will be left behind as the water evaporates, altering the measured weight change in the gypsum specimen. Calcination of gypsum, in its most common commercial form, involves heating gypsum, calcium sulfate dihydrate, and driving off some of the water of crystallization to form stucco, calcium sulfate hemihydrate. In each case, gypsum panels must not be overexposed to excessive moisture levels. © 2021 Gypsum Association. However, unless extremely careful laboratory calibrations have been conducted for the specific types of gypsum panels being tested, a moisture meter will not provide reliable readings of the actual gravimetric moisture content of a panel. by mixing the calcium sulfate with water. Known as dihydrate in construction chemistry, gypsum is a water-containing calcium sulfate (CaSO4• 2 H2O). In the wet process, water is usually added to the raw mix to The measurement volume includes a thin hygroscopic layer (in the case of a paper facer), and a much larger volume of inorganic mineral (the gypsum core). Cement, Industrial Efficiency Technology & Measures. • Standard laboratory tests using convection ovens have been conducted to measure the actual moisture content of gypsum panel specimens to specifically compare the results to moisture meter readings on the same specimens. Beyond a flood or natural disaster, gypsum panels can be exposed to water in a number of ways, including improper installation, missing flashing, ruptured pipes, bathtub overflows, and general water leaks. This document is subject to copyright. On heating above 250 °C (480°F), the completely anhydrous form called β-anhydrite or dead burned plaster is formed. It is important to recognize that, unlike lumber, a gypsum panel consists of an inorganic core comprising the bulk of panel thickness with thin paper or glass mat facers laminated to the front and back of the panel. Wet chemical gypsum cake may be directly fed to a continuous kettle calciner to produce a stucco having lowered dispersed consistency. However, there has always been disagreement about whether the water molecules also adopt a defined arrangement and if so, what it looks like. The word Calcination h… Large production rate, compact shape, ergonomic design, low energy usage rate and ease of controlling are its key features. By using various tricks they were able to interpret the diffraction pattern and to use their computer calculations to consolidate the data into a plausible structural model. However, this has been very difficult to achieve in the case of gypsum crystals. In various calcination processes, some of the water of crystallization is removed, resulting in calcined gypsum, or hemihydrate (CaSO4• 0.5 H2O). Pre-drying of the chemical gypsum is eliminated and the thus produced stucco may be used in the formulation of building plasters and in gypsum wallboard manufacture that will use less fuel for drying excess gauging water. For instance, hand-held moisture meters can be used to identify areas of gypsum panels that are relatively “moist” and areas that are relatively “dry” after a building has been exposed to excessive amounts of water. The calcination of gypsum by continuously feeding fine gypsum spirally downwardly through a cylindrical zone into which heated air is injected almost tangentially forming a spiral air conveyor. or. and Terms of Use. Driving off the chemically combined water in the gypsum core with heat is technically referred to as “calcination.” An understanding of the chemistry of gypsum and the calcination process is necessary to accurately measure the moisture content of gypsum panels, even under laboratory conditions with trained technicians. In the preliminary study, the gypsum plaster for finish coat-ing was prepared by adding a protein-based retarder (SC), a polycarboxylate-based water-reducing admixture (F10), and an ether-based water-retaining admixture (HPMC) to the hemihydrate from calcination of FGD gypsum. GYPSUM. Consequently, acquiring an accurate and reliable moisture reading from gypsum panels using a hand-held moisture meter is a challenge. 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