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Free Moisture Measurement. This is the amount of water that will evolve off of the material, but is not chemically bound to the plaster. In order to determine the purity of the gypsum in the wallboard, this must be measured and removed, since it may significantly impact the bound moisture measurement.
FREE AND BOUND WATER DETERMINATIONS BY THE HEAT OF FUSION OF ICE METHOD* BY WILLIAM ROBINSON (From the Otho S. A. Sprague Memorial Institute and the Department of Pathology of the University of Chicago, Chicago) (Received for publication, February 19, 1931)
Water vapor is free to ow through the porous gypsum and condense in colder regions of the board. The condensed water can ow due to capillary pressure. Eventually temperatures will become sufciently high such that all of the moisture is released from the board. As was discussed in the previous section, it is unclear whether water vapor
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. Bound water is researched in the various fields as it has the influence on the quality of foods and medicines _ By observmg the melting phenomena of water using DSC, free and bound water can be identified
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#174; understands; thats why Computrac has been the de facto industry standard for moisture measurement in gypsum
#0183;#32;Compared to the amount of chemically bound water in gypsum ( m 3 m 3), this free water content is only % of the total water content. The gypsum sample is initially fully hydrated ( =1). Any increase of the signal above the maximum hydration degree of one must therefore originate from free
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
place at high temperatures. 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 fire safety point of view, allowing sufficient building evacuation times.
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,
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
JOURNALS FREE ACCESS. 1957 Volume 1957 Issue 31 Pages DOI https the primary dehydration temperature of natual dihydrated gypsum used as a test sample is 133#176;C while its secondary dehydration temperature being 192#176;C. Under pressure of saturated water vapor,
specimens of gypsum (Type X) with temperature. The results are represented in Fig. 6. As can be seen, between 100#176;C to 160#176;C about % of the initial mass is lost, which indicates the first dehydration reaction and the release of water of crystallization ( #215; 21% = %) as well as the evaporation of the free water (less than 3%).
minimal free energy. Figure 1 provides a full scheme and temperature ranges for the changes that it undergoes on heating (Ferronskaya 2004). The principal physical and chemical process in the production of gypsum binding materials is the disengagement of chemically bound water from the
Measurement of Free Water and Combined Water of Gypsum. Mark Flumiani, Jim Turner and ia Trimble (CertainTeed Gypsum Canada) Presented at ASTM C11 Centennial Symposium on Advances in Gypsum Technologies and Building Systems, Aneim, 2015 Printed in ASTM STP1588.
In addition, gypsum boards usually contain small amounts of absorbed free water (lt;4 wt%) [1][2][3], as well as magnesium carbonate (MgCO 3 ) [4], calcium carbonate (CaCO 3 ) [4,5] and/or other
Calcination is the practice of dehydrating gypsum into plaster or stucco through a batch or continuous process which includes heating the gypsum to evaporate the crystalline water. Typically, free water is removed in an initial process at approximately 45 and crystalline bound water is removed in a second process at 120180.
#0183;#32;Commercial gypsum boards are porous materials that consist mainly of calcium sulphate dihydrate (CaSO 4 #183;2H 2 O) (gt;65 wt%), which contains 21% by weight chemically bound water, and a small amount of absorbed free water (4%),,, .
chemically bound water and the free moisture were evaporated, as well as during the PCM evapora tion, the thermal conductivity of the gypsum board was reduced due to increase of the porosity. 1.
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