Solubility and Aging of Calcium Silicate Hydrates in Alkaline-Solutions at 25-Degrees-C

Donald E MacPhee, K LUKE, Fredrik Paul Glasser, Eric Lachowski

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Abstract

Calcium silicate hydrate (C‐S‐H) gels are the principal bonding material in portland cement. Their solubility properties have been described, enabling pH and solubilities to be predicted. However, the gels also interact with other components of cements, notably alkalis. C‐S‐H has been prepared from lime and silicic acid in solutions of sodium hydroxide or potassium hydroxide and by the hydration of tricalcium silicate (C3S) in sodium hydroxide solutions. Analyses of aqueous phases in equilibrium with 85 gels show that the aqueous calcium and silicon concentrations fit smooth curves over the range of increasing sodium concentrations. Where anomalous data occur, they correspond to solids with low lime contents: such gels are tentatively assumed to fall into a region where the presence of another gel phase influences the aqueous composition. Dimensional changes have been observed in the hydration products of C3S as a function of alkali content and these may be relevant to the alkali‐silica reaction. The significance of this and other data is discussed with reference to real cement systems.
Original languageEnglish
Pages (from-to)646-654
Number of pages9
JournalJournal of the American Ceramic Society
Volume72
Issue number4
DOIs
Publication statusPublished - Apr 1989

Keywords

  • alkalis
  • calcium
  • cements
  • hydrates
  • silicates

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