Some Properties of the Combined Water of Ground Gypsum and Its Effects on the Hydration of Hemihydrate

DOI
  • YAMADA Tamotsu
    Department of Industrial Chemistry, Chubu Institute of Technology
  • WATANABE Makoto
    Department of Industrial Chemistry, Chubu Institute of Technology
  • KIMURA Hazime
    Department of Industrial Chemistry, Chubu Institute of Technology

Bibliographic Information

Other Title
  • 摩砕二水セッコウの結合水の性質と半水セッコウの水和への影響

Abstract

The ground gypsum dihydrate (the ground) has powerful accelerating effect to the setting of gypsum hemihydrate (hemihydrate), and it is increased by cooperation with usual accelerators, and the setting can be shortened to 20-90%.<BR>The ground deducts the retarding effect of usual retarders, and shortenes the setting time to 20-70%.<BR>Set gypsum mixed with the ground has higher compressive strength than normal set gypsum.<BR>By scanning electron micrograph of the ground crystal which was taken from the slurry under setting, the activated nucleation on the crystal surface was observed.<BR>The ground loses water of about 0. 7% by atomospheric drying or by coevaporation with ethanol. Quantity of this loss was calculated from the increase of crystal surface, and was nearly equal to experimental value.<BR>The dehydration of the ground begins at about 60°C, and the activation energy of this dehydration was estimated as 250 J/mol. Uuder atomosphere of RH 81% and room temperature the ground loses water of about 0. 7%, and then absorbs moisture to 0.4% increase of the weight. Under this condition mixture of hemihydrate and the ground absorbs moisture quickly and converts to dihydrate.<BR>Under RH 9% and room temperature the ground acts as under RH 81%, but the mixture of hemihydrate loses water of about 0. 7% and then absorbs moisture to 0. 4% loss of the weight regardless of the coexistence of the ground.<BR>The mechanism of this moisture absorption can be explained that the ground carry the water to hemihydrate from moisture by repeating dehydration and absorption.

Journal

  • Gypsum & Lime

    Gypsum & Lime 1983 (184), 124-130, 1983

    The Society of Inorganic Materials, Japan

Keywords

Details 詳細情報について

  • CRID
    1390001205389495040
  • NII Article ID
    130004011233
  • DOI
    10.11451/mukimate1953.1983.124
  • ISSN
    21854351
  • Data Source
    • JaLC
    • CiNii Articles
  • Abstract License Flag
    Disallowed

Report a problem

Back to top