TY - JOUR
T1 - Underwater carbonation of alkali-activated slag pastes
AU - Liu, Chen
AU - Zhang, Yu
AU - Liang, Minfei
AU - Li, Zhenming
AU - Ye, Guang
PY - 2024
Y1 - 2024
N2 - 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.
AB - 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.
KW - Alkali-activated slag
KW - Carbonation
KW - Leaching
KW - Nanoindentation
KW - Water immersion
UR - http://www.scopus.com/inward/record.url?scp=85201611257&partnerID=8YFLogxK
U2 - 10.1016/j.conbuildmat.2024.137967
DO - 10.1016/j.conbuildmat.2024.137967
M3 - Article
AN - SCOPUS:85201611257
SN - 0950-0618
VL - 445
JO - Construction and Building Materials
JF - Construction and Building Materials
M1 - 137967
ER -