Underwater carbonation of alkali-activated slag pastes

Chen Liu, Yu Zhang, Minfei Liang, Zhenming Li*, Guang Ye*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

Carbonation of alkali-activated slag (AAS) materials has been primarily concerned in atmospheres with gaseous CO2. This study, by contrast, highlights that AAS pastes would also be carbonated under tap water immersion. Calcite is the main CO2-bear phase in both sodium hydroxide- and sodium silicate-activated AAS pastes, and the paste pre-cured for a longer curing period shows more severe carbonation. Additionally, calcium carbonate can densify the deteriorated microstructure of sodium hydroxide-activated paste caused by long-term leaching. The indentation modulus of pastes subjected to tap water immersion is higher than those under deionized water immersion. The uptake of CO32- by hydrotalcite (Ht) and gels is also detected, resulting in the formation of Ht-CO3 and decalcification of gels. Due to the synergistic effect of leaching and carbonation, a characteristic layered distribution of pastes close to the exposure front is observed, comprising the carbonated layer, transitional (carbonated + leached) layer, and leached layer, progressing from the outermost to the inner regions. Eventually, the kinetics of underwater carbonation, as well as the discrepancy between dry and underwater carbonation, is revealed.

Original languageEnglish
Article number137967
Number of pages13
JournalConstruction and Building Materials
Volume445
DOIs
Publication statusPublished - 2024

Keywords

  • Alkali-activated slag
  • Carbonation
  • Leaching
  • Nanoindentation
  • Water immersion

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