Alkali binding in cement pastes Part I. The C-S-H phase

S Y Hong, F P Glasser

Research output: Contribution to journalArticle

240 Citations (Scopus)

Abstract

The binding of sodium and potassium into cement paste influences the performance of concrete: for example, alkali balances between solid and paste constituents and pore fluid affect the potential for reaction with alkali-susceptible aggregates. However, quantification of the binding potential into paste solids has proven to be difficult, although much empirical data are available from pore fluid analyses. In this study. single-phase homogeneous C-S-H phases have been prepared at Ca:Si molar ratios of 1.8, 1.5, 1.2, and 0.85 and reacted with six alkali hydroxide concentrations, both NaOH and KOH, between 1 and 300 mM, giving a grid of 48 alkali concentrations and Ca:Si ratios. A steady-state alkali partition is attained in less than 48 h. A distribution coefficient, R-d, was calculated to express the partition of alkali between solid and aqueous phases at 20 degrees C. The numerical value of R-d is independent of alkali hydroxide concentration and depends only on Ca:Si ratio. Approximate reversibility is demonstrated, so the R-d values are constants of a C-S-H over wide ranges of alkali concentration. The trend of R-d values indicates that alkali binding into the solid improves as its Ca:Si ratio decreases. (C) 2000 Elsevier Science Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)1893-1903
Number of pages11
JournalCement and Concrete Research
Volume29
Publication statusPublished - 1999

Keywords

  • C-S-H
  • sodium
  • potassium
  • alkali
  • pore solution
  • PORTLAND-CEMENT

Cite this

Hong, S. Y., & Glasser, F. P. (1999). Alkali binding in cement pastes Part I. The C-S-H phase. Cement and Concrete Research, 29, 1893-1903.

Alkali binding in cement pastes Part I. The C-S-H phase. / Hong, S Y ; Glasser, F P .

In: Cement and Concrete Research, Vol. 29, 1999, p. 1893-1903.

Research output: Contribution to journalArticle

Hong, SY & Glasser, FP 1999, 'Alkali binding in cement pastes Part I. The C-S-H phase' Cement and Concrete Research, vol. 29, pp. 1893-1903.
Hong, S Y ; Glasser, F P . / Alkali binding in cement pastes Part I. The C-S-H phase. In: Cement and Concrete Research. 1999 ; Vol. 29. pp. 1893-1903.
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AB - The binding of sodium and potassium into cement paste influences the performance of concrete: for example, alkali balances between solid and paste constituents and pore fluid affect the potential for reaction with alkali-susceptible aggregates. However, quantification of the binding potential into paste solids has proven to be difficult, although much empirical data are available from pore fluid analyses. In this study. single-phase homogeneous C-S-H phases have been prepared at Ca:Si molar ratios of 1.8, 1.5, 1.2, and 0.85 and reacted with six alkali hydroxide concentrations, both NaOH and KOH, between 1 and 300 mM, giving a grid of 48 alkali concentrations and Ca:Si ratios. A steady-state alkali partition is attained in less than 48 h. A distribution coefficient, R-d, was calculated to express the partition of alkali between solid and aqueous phases at 20 degrees C. The numerical value of R-d is independent of alkali hydroxide concentration and depends only on Ca:Si ratio. Approximate reversibility is demonstrated, so the R-d values are constants of a C-S-H over wide ranges of alkali concentration. The trend of R-d values indicates that alkali binding into the solid improves as its Ca:Si ratio decreases. (C) 2000 Elsevier Science Ltd. All rights reserved.

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