Alkali-activated materials partially activated using flue gas residues: An insight into reaction products

•Flue gas residues (FGR) was utilized as alkaline activator.•Reaction products were examined by selective dissolution approach.•FGR could successfully replace the commercial activator in the AAFS pastes.•N-A-S-H and C-A-S-H gels were main reaction products of AAFS pastes. This study explored the fea...

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Bibliographic Details
Published in:Construction & building materials 2023-03, Vol.371, p.130760, Article 130760
Main Authors: Riaz Ahmad, Muhammad, Khan, Mehran, Wang, Aiguo, Zhang, Zuhua, Dai, Jian-Guo
Format: Article
Language:English
Subjects:
Alkali-activated gel
Flue gas residue
Microstructure
Nuclear magnetic resonance
Reaction products
Selective dissolution
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Summary:•Flue gas residues (FGR) was utilized as alkaline activator.•Reaction products were examined by selective dissolution approach.•FGR could successfully replace the commercial activator in the AAFS pastes.•N-A-S-H and C-A-S-H gels were main reaction products of AAFS pastes. This study explored the feasibility of using flue gas residues (FGR) and commercial sodium silicate (CSS) as hybrid activators (HA) to prepare alkali-activated materials (AAMs). The CSS was replaced by 8, 16, and 24% FGR for a fixed amount of Na2O. Results from selective dissolution techniques showed that control paste (CP-0F, 0% FGR) contained a slightly higher amount of N-A-S-H gel as compared to pastes prepared by hybrid activators (HAPs), whereas the amount of C-A-S-H gel was higher in HAPs containing 16% and 24% FGR. These findings were further corroborated by SEM-EDS analysis results. TGA, XRF and SEM-EDS analysis on paste residues confirmed the efficacy of HCl and SAM dissolution approaches to selectively dissolve the reaction products (N-A-S-H and C-A-S-H gels). SEM-EDS analysis showed that calcium-rich cross-linked gel (C-(N)-A-S-H) was present in all pastes. The gradual increase in reaction products of alkali-actived fly ash/slag (AAFS) pastes with the increase in curing age was observed by XRD analysis. The 29Si MAS NMR analysis revealed the formation of a higher amount of Q4(0Al) and Q4(1Al) species in HAPs as compared to control paste however a decline in the amount of Q4(3Al) and Q4(4Al) species was observed.
ISSN:0950-0618
1879-0526
DOI:10.1016/j.conbuildmat.2023.130760