Assessment of the protective effect of carbonation on portlandite crystals

Isabel Galan, F. P. Glasser, D. Baza, C. Andrade

Research output: Contribution to journalArticle

Abstract

The kinetics of many reactions important to cement hydration and use are not well understood: this is in part due to the great complexity of many supposedly "simple" processes. One such process, carbonation of portlandite, Ca(OH)2, in moist air at ~ 23 °C has been investigated by microscopy and microchemical analysis. Single crystals of portlandite were grown, carbonated at relative humidities between ~ 25 and ~ 90%, and the transport properties of the self-generated calcite, CaCO3, product film were determined. The calcite films thus grown within days or weeks varied in thickness but typically were polycrystalline and epitaxial: a variety of morphologies and surface features are recorded. Permeation was measured by determining the time taken for Ca2 + ions, arising from the Ca(OH)2 substrate, to diffuse through the calcite coat into initially pure water. The spontaneous formation of self-protecting films on concrete has long been envisaged: results demonstrate that passivation can actually be achieved.

Original languageEnglish
Pages (from-to)68-77
Number of pages10
JournalCement and Concrete Research
Volume74
DOIs
Publication statusPublished - 1 Aug 2015
Externally publishedYes

Keywords

  • B surface layer
  • C carbonation
  • C durability
  • C permeability
  • D Ca(OH)<inf>2</inf>

ASJC Scopus subject areas

  • Building and Construction
  • Materials Science(all)

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