Effect of alkali hydroxide on calcium silicate hydrate (C-S-H)

Yiru Yan*, Sheng Yu Yang, George D. Miron, Ines E. Collings, Emilie L'Hôpital, Jørgen Skibsted, Frank Winnefeld, Karen Scrivener, Barbara Lothenbach

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

1 Citation (Scopus)
28 Downloads (Pure)

Abstract

This paper investigates the effect of KOH and NaOH on C-S-H structure and solubility. Both KOH and NaOH have a similar effect, they increase pH values and silicon concentrations, and decrease calcium concentrations. At higher alkali hydroxide concentrations, more portlandite precipitates, while amorphous silica dissolves. This increases the Ca/SiC-S-H at low Ca/Sitarget but lowers the maximum Ca/SiC-S-H from 1.5 to 1.2 in 1 M KOH/NaOH. The amount of alkalis bound in C-S-H increases with increasing alkali hydroxide concentrations and is higher at low Ca/SiC-S-H. KOH/NaOH lead to a structural rearrangement in C-S-H, increasing the interlayer distance, number of layers stacked in c direction and shortening the silica chains. The mean chain lengths (MCL) estimated from FTIR and Raman spectroscopy agree well with the trends from 29Si NMR. Comparison with the independently developed CASH+ thermodynamic model showed a good agreement between the observed and modelled changes, including the shortening of the MCL.

Original languageEnglish
Article number106636
JournalCement and Concrete Research
Volume151
Number of pages22
ISSN0008-8846
DOIs
Publication statusPublished - Jan 2022

Keywords

  • Alkali hydroxide
  • C-S-H
  • Ca/Si ratio
  • Cement
  • Characterization

Fingerprint

Dive into the research topics of 'Effect of alkali hydroxide on calcium silicate hydrate (C-S-H)'. Together they form a unique fingerprint.

Cite this