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Underwater carbonation of alkali-activated slag pastes

Journal Article (2024)
Author(s)

C. Liu (TU Delft - Materials and Environment)

Y. Zhang (TU Delft - Materials and Environment)

Minfei Liang (TU Delft - Materials and Environment)

Z. Li (Harbin Institute of Technology)

G Ye (TU Delft - Materials and Environment)

Research Group
Materials and Environment
DOI related publication
https://doi.org/10.1016/j.conbuildmat.2024.137967
More Info
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Publication Year
2024
Language
English
Research Group
Materials and Environment
Volume number
445
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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.