ETTRINGITE, THAUMASITE AND WOODFORDIT

Studies have found that the thermal decomposition of ettringite in water suspensions at temperatures above 110, 190 and 280 deg. C is as follows: C6ASH32 110 - C4ASH12 + H:H =190 = C3AH6 + CS + H:280 = C4A3H3 + CH + H where C=CaO; A = A1203; S=SO3; and H = H20. It was also found that ettringite had the formula Ca6 (A1 (OH)6)2.(SO4)3.25.7H23. Investigation have revealed that deterioration of a soil-cement pavement resulted from the formation f Thaumasite Ca6 (S1(OH)6)2.24 H20(SO4)2(CO3)2 or a solid solution of it with ettringite. Further studies show that damage to a concrete tunnel lining was the result of formation of Thaumasite and Woodfordit CA6A11.5 (SO4.SiO2 CO3).(OH)10.5 15 H20. The composition of si-ettringite has been found to be Ca6 (Si(OH)6)2 (SO4)3 24H20.

  • Corporate Authors:

    United States Gypsum Company

    Department No. 119-7, 101 South Wacker Drive
    Chicago, IL  USA  60606

    United States Gypsum Company

    Chemicals Division Department 125-4, 101 South Wacker Drive
    Chicago, IL  USA  60606
  • Publication Date: 1976-10

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Filing Info

  • Accession Number: 00149614
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 13 1977 12:00AM