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A long-term study on structural changes in calcium aluminate silicate hydrates.
- Source :
-
Materials and structures [Mater Struct] 2022; Vol. 55 (10), pp. 243. Date of Electronic Publication: 2022 Nov 24. - Publication Year :
- 2022
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Abstract
- Production of blended cements in which Portland cement is combined with supplementary cementitious materials (SCM) is an effective strategy for reducing the CO <subscript>2</subscript> emissions during cement manufacturing and achieving sustainable concrete production. However, the high Al <subscript>2</subscript> O <subscript>3</subscript> and SiO <subscript>2</subscript> contents of SCM change the chemical composition of the main hydration product, calcium aluminate silicate hydrate (C-A-S-H). Herein, spectroscopic and structural data for C-A-S-H gels are reported in a large range of equilibration times from 3 months up to 2 years and Al/Si molar ratios from 0.001 to 0.2. The <superscript>27</superscript> Al MAS NMR spectroscopy and thermogravimetric analysis indicate that in addition to the C-A-S-H phase, secondary phases such as strätlingite, katoite, Al(OH) <subscript>3</subscript> and calcium aluminate hydrate are present at Al/Si ≥ 0.03 limiting the uptake of Al in C-A-S-H. More secondary phases are present at higher Al concentrations; their content decreases with equilibration time while more Al is taken up in the C-A-S-H phase. At low Al contents, Al concentrations decrease strongly with time indicating a slow equilibration, in contrast to high Al contents where a clear change in Al concentrations over time was not observed indicating that the equilibrium has been reached faster. The <superscript>27</superscript> Al NMR studies show that tetrahedrally coordinated Al is incorporated in C-A-S-H and its amount increases with the amount of Al present in the solution.<br />Supplementary Information: The online version contains supplementary material available at 10.1617/s11527-022-02080-x.<br />Competing Interests: Conflict of interestThe authors have no competing interests to declare that are relevant to the content of this article.<br /> (© The Author(s) 2022.)
Details
- Language :
- English
- ISSN :
- 1359-5997
- Volume :
- 55
- Issue :
- 10
- Database :
- MEDLINE
- Journal :
- Materials and structures
- Publication Type :
- Academic Journal
- Accession number :
- 36447990
- Full Text :
- https://doi.org/10.1617/s11527-022-02080-x