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 language | English |
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Pages (from-to) | 68-77 |
Number of pages | 10 |
Journal | Cement and Concrete Research |
Volume | 74 |
DOIs | |
Publication status | Published - 1 Aug 2015 |
Externally published | Yes |
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)