STP861

    The Effect of Sorbed Water on the Determination of Phase Composition of CaSO4 · H2O Systems by Various Methods

    Published: Jan 1984


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    Abstract

    The efficiency of calcination processes is monitored by careful phase analysis of CaSO4 · H2O systems. The usual method of determining a small amount of gypsum in such systems involves the determination of sorbed (free) water, water of crystallization (combined water), and Ca++/SO4−− ratio. The removal of free water from CaSO4 · ½H2O and active orthorhombic calcium sulfate occurs at about the same temperature range as the decomposition of CaSO4 · 2H2O, which then becomes a most critical stage in the phase analysis of these systems. This paper discusses (1) relative merits of various methods utilized in removing free water, which includes several thermal methods and microwave drying, and (2) the state of the sorbed water as it develops from exposure to radically varying relative humidity conditions.

    Keywords:

    gypsum, drying, anhydrite, α-hemihydrate, β-hemihydrate, phase analysis, drying curves, water sorption


    Author Information:

    Turk, DH
    Research associates, United States Gypsum Company, Graham J. Morgan Research Center, Libertyville, IL

    Bounini, L
    Research associates, United States Gypsum Company, Graham J. Morgan Research Center, Libertyville, IL


    Paper ID: STP30269S

    Committee/Subcommittee: C11.01

    DOI: 10.1520/STP30269S


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