Compositions and Microstructures of Carbonated Geopolymers with Different Precursors
It is thought that geopolymers are easy to carbonate, especially when they are cured in ambient temperatures. Matrix gel’s composition and microstructure, and new products of geopolymers (GPs) after carbonation were investigated in this study on the basis of XRD and SEM-EDS measurements and ternary...
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MDPI AG
2024-03-01
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| Online Access: | https://www.mdpi.com/1996-1944/17/7/1491 |
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| author | Zhuguo Li Ko Ikeda |
| author_facet | Zhuguo Li Ko Ikeda |
| author_sort | Zhuguo Li |
| collection | DOAJ |
| description | It is thought that geopolymers are easy to carbonate, especially when they are cured in ambient temperatures. Matrix gel’s composition and microstructure, and new products of geopolymers (GPs) after carbonation were investigated in this study on the basis of XRD and SEM-EDS measurements and ternary diagram analysis, which were prepared from low-lime fly ash (FA) and ground granulated blast-furnace slag (GGBS) alone or a blend, as a precursor. The specimens were hardened in a 20 °C environment with alkali activator solution (S/N = 1.1 in mole), followed by storage under sealing or accelerated carbonation. XRD patterns show that carbonation products were nahcolite for the sole FA-based GP and calcite for the GPs using GGBS alone or as a blend. The SEM images of carbonated samples show that there were cube-shaped calcite and small calcite particles in the GGBS-based GP, but hail-like particles in the FA/GGBS blend-based GP. The hail-like particles were complexes of calcite and C-A-S-H gels determined by ternary diagram analysis, and were found to plug the top of the pores of the spongy C-A-S-H gels. We also confirmed that combined ternary diagram analysis of S-(C + M + N)-A and A-(C + M)-N are very effective in determining the gel type of a geopolymer, as well as the products and compositional changes after carbonation, in which oxide components of gels are determined by SEM-EDS. In the former diagram, C-A-S-H gels were plotted linearly along the (C + M + N)-albite (Ab) join, while N-A-S-H gels showed a scattered distribution. In the latter diagram, the plots for N-A-S-H and C-A-S-H gels are distributed in different zones. N = Na<sub>2</sub>O, C = CaO, M = MgO, A = Al<sub>2</sub>O<sub>3</sub>, S = SiO<sub>2</sub>, H = H<sub>2</sub>O. |
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| language | English |
| last_indexed | 2024-04-24T10:41:37Z |
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| spelling | doaj.art-cdaaa310069f4474823f4598f01ee9782024-04-12T13:21:48ZengMDPI AGMaterials1996-19442024-03-01177149110.3390/ma17071491Compositions and Microstructures of Carbonated Geopolymers with Different PrecursorsZhuguo Li0Ko Ikeda1Graduate School of Science and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611, JapanGraduate School of Science and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611, JapanIt is thought that geopolymers are easy to carbonate, especially when they are cured in ambient temperatures. Matrix gel’s composition and microstructure, and new products of geopolymers (GPs) after carbonation were investigated in this study on the basis of XRD and SEM-EDS measurements and ternary diagram analysis, which were prepared from low-lime fly ash (FA) and ground granulated blast-furnace slag (GGBS) alone or a blend, as a precursor. The specimens were hardened in a 20 °C environment with alkali activator solution (S/N = 1.1 in mole), followed by storage under sealing or accelerated carbonation. XRD patterns show that carbonation products were nahcolite for the sole FA-based GP and calcite for the GPs using GGBS alone or as a blend. The SEM images of carbonated samples show that there were cube-shaped calcite and small calcite particles in the GGBS-based GP, but hail-like particles in the FA/GGBS blend-based GP. The hail-like particles were complexes of calcite and C-A-S-H gels determined by ternary diagram analysis, and were found to plug the top of the pores of the spongy C-A-S-H gels. We also confirmed that combined ternary diagram analysis of S-(C + M + N)-A and A-(C + M)-N are very effective in determining the gel type of a geopolymer, as well as the products and compositional changes after carbonation, in which oxide components of gels are determined by SEM-EDS. In the former diagram, C-A-S-H gels were plotted linearly along the (C + M + N)-albite (Ab) join, while N-A-S-H gels showed a scattered distribution. In the latter diagram, the plots for N-A-S-H and C-A-S-H gels are distributed in different zones. N = Na<sub>2</sub>O, C = CaO, M = MgO, A = Al<sub>2</sub>O<sub>3</sub>, S = SiO<sub>2</sub>, H = H<sub>2</sub>O.https://www.mdpi.com/1996-1944/17/7/1491geopolymercarbonationcompositional changemicrostructurefly ashslag |
| spellingShingle | Zhuguo Li Ko Ikeda Compositions and Microstructures of Carbonated Geopolymers with Different Precursors Materials geopolymer carbonation compositional change microstructure fly ash slag |
| title | Compositions and Microstructures of Carbonated Geopolymers with Different Precursors |
| title_full | Compositions and Microstructures of Carbonated Geopolymers with Different Precursors |
| title_fullStr | Compositions and Microstructures of Carbonated Geopolymers with Different Precursors |
| title_full_unstemmed | Compositions and Microstructures of Carbonated Geopolymers with Different Precursors |
| title_short | Compositions and Microstructures of Carbonated Geopolymers with Different Precursors |
| title_sort | compositions and microstructures of carbonated geopolymers with different precursors |
| topic | geopolymer carbonation compositional change microstructure fly ash slag |
| url | https://www.mdpi.com/1996-1944/17/7/1491 |
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