The Role of Al in Cross‐Linking of Alkali‐Activated Slag Cements
By R. Myers, S. A. Bernal, J. Gehman, J. V. van Deventer, J. Provis. 2015
263 citations recorded by the source corpus.
The structural development of a calcium (sodium) aluminosilicate hydrate (C–(N-)A–S–H) gel system, obtained through the reaction of sodium metasilicate and ground granulated blast furnace slag, is assessed by high-resolution 29Si and 27Al MAS NMR spectroscopy during the first 2 yr after mixing. The cements formed primarily consist of C–(N-)A–S–H gels, with hydrotalcite and disordered alkali aluminosilicate gels also identified in the solid product assemblages. Deconvolution of the 27Al MAS NMR spectra enables the identification of three distinct tetrahedral Al sites, consistent with the 29Si MAS NMR data, where Q3(1Al), Q4(3Al), and Q4(4Al) silicate sites are identified. These results suggest significant levels of cross-linking in the C–(N-)A–S–H gel and the presence of an additional highly polymerized aluminosilicate product. The mean chain length, extent of cross-linking, and Al/Si ratio of the C–(N-)A–S–H gel decrease slightly over time. The de-cross-linking effect is explained by the key role of Al in mixed cross-linked/non-cross-linked C–(N-)A–S–H gels, because the cross-linked components have much lower Al-binding capacities than the noncross-linked components. These results show that the aluminosilicate chain lengths and chemical compositions of the fundamental structural components in C–(N-)A–S–H gels vary in a way that is not immediately evident from the overall bulk chemistry.
Subfields: Biomaterials, Ceramics and Composites, Civil and Structural Engineering
View Paper: https://www.semanticscholar.org/paper/ad85f23455600d008ba80b88fb40bc8e119c37e5
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Citations in the corpus
- Structural evolution of an alkali sulfate activated slag cement (2016, background): “The low intensity band centred at 4 ppm , ainly 309 observed after 12 and 18 months of curing , s attributed to the third aluminate hydrate (TAH) 310 [27], as this phase has been identified in other alkali -activated slag systems [28].”
- Phase diagrams for alkali-activated slag binders (2017, background): “[8], including strätlingite [15], and sodium aluminosilicate (hydrate) (N-A-S(-H))-type gels [6,11].”