Abstract
The carbonation resistance of alkali-activated binders is often tested via accelerated test protocols designed for Portland cements, without questioning whether the tests replicate the mechanisms observed in service. Thus, validation of accelerated methods is required to enable realistic prediction of material performance. Changes in pore solution equilibria cause the formation of sodium bicarbonates during accelerated carbonation, compared with hydrous sodium carbonates in natural carbonation. This shifts the carbonation mechanism to favour more rapid reaction progress, to give a higher apparent degree of acceleration (compared to natural conditions) than in Portland cements. The pore solution pH under accelerated carbonation is significantly lower than at natural CO 2 concentrations, leading to a falsely short predicted service life (time to expected corrosion of embedded steel), as natural CO 2 concentrations appear not to reduce the pH below 10. Thus, accelerated carbonation testing is unduly aggressive towards alkali-activated binders, and test results must be cautiously interpreted.
| Original language | English |
|---|---|
| Pages (from-to) | 1317-1326 |
| Number of pages | 10 |
| Journal | Cement and Concrete Research |
| Volume | 42 |
| Issue number | 10 |
| DOIs | |
| Publication status | Published - 31 Oct 2012 |
Keywords
- Alkali-activated cement (D)
- Carbonation (C)
- Durability (C)
- Pore solution (B)
- Thermodynamic calculations (B)
ASJC Scopus subject areas
- Building and Construction
- General Materials Science