A molecular dynamics study of the aluminosilicate chains structure in Al‐rich calcium silicate hydrated (C–S–H) gels

Manzano, Hegoi; Dolado, Jorge S.; Griebel, Michael; Hamaekers, Jan

doi:10.1002/pssa.200778175

Cited by 69 publications

(40 citation statements)

References 30 publications

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“…A detailed distribution of Q n sites as function of Ca/(Al + Si) ratio is provided in Table . This matches well with the formation of alumino‐silicate glasses using reactive force field modeling by Manzano et al . This theoretically explains the formation of alumino‐silicate networks observed in NMR experiments which indicates the increase of the Q 2 (1Al) signal and the appearance of a Q 3 (1Al) peak.…”

Section: Resultssupporting

confidence: 89%

“…Roughly, by a 10% increase in the aluminum content in the interlayer of CSH structure which is equal to 45% decrease in Ca/(Al + Si) ratio, the mean chain length is increased by 85%. These results are in good agreement with the separate NMR experiments of Puertas et al 44 and Richardson et al 45 , and polymerization simulations of Manzano et al 43 Although NMR experimentalists attribute the increase in chain length to the siliconaluminum substitution 16,17 only, we highlight that this phenomenon is probably due to calcium-aluminum replacements. The possibility of cross-links between layers (Q 3 sites giving rise to a three-dimensional solid) can influence the way load is transferred from one layer to the next.…”

Section: ) Substitution Of Silicon By Aluminum In Cshssupporting

confidence: 92%

“…and Richardson et al ,. and polymerization simulations of Manzano et al . Although NMR experimentalists attribute the increase in chain length to the silicon‐aluminum substitution only, we highlight that this phenomenon is probably due to calcium‐aluminum replacements.…”

Section: Resultsmentioning

confidence: 51%

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Evidence on the Dual Nature of Aluminum in the Calcium‐Silicate‐Hydrates Based on Atomistic Simulations

Qomi

Ulm

Pellenq³

2012

J. Am. Ceram. Soc.

118

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Hydration of tri‐calcium silicate (C3S) and di‐calcium silicate (C2S) precipitates calcium‐silicate‐hydrate (CSH) which is the bonding phase responsible for the strength of cementitious materials. Substitution of part of C3S and C2S with aluminum‐containing additives alters the chemical composition of hydration products by precipitating calcium‐aluminate‐silicate‐hydrate (CASH). Incorporation of aluminum in the molecular building blocks of CSH entails structural and chemo‐mechanical consequences. These alterations can be measured through solid state nuclear magnetic resonance (NMR) experiments. By conducting a wide spectrum of atomistic simulation methods on thousands of aluminum‐containing molecular CASH structures, an overall molecular approach for determination of CASH nanostructure is presented. Through detailed analysis of different order parameters, it is found that aluminum can exhibit a tetra‐/penta‐/octahedral behavior which is fully consistent with the recent NMR observations. This corresponds to the formation of a class of complex three‐dimensional alumino‐silicate skeletons with partial healing effect in the CASH nanostructure potentially increasing durability and strength of hydration products. We explored the variation of mechanical observables by increasing aluminum content in CASH structures of varying calcium to silicon ratio. Finally, deformation of CSHs and CASHs of different chemical formula in a multi‐scale fashion unravels the effect of chemical composition on the strength and kinematics of deformation in this particular type of composites.

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Section: Resultssupporting

confidence: 89%

Section: ) Substitution Of Silicon By Aluminum In Cshssupporting

confidence: 92%

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Evidence on the Dual Nature of Aluminum in the Calcium‐Silicate‐Hydrates Based on Atomistic Simulations

Qomi

Ulm

Pellenq³

2012

J. Am. Ceram. Soc.

118

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“…The other is a pairing tetrahedron where the Si atom shares one O atom with the CaO sheet . Al can substitute for Si in either bridging tetrahedra or pairing tetrahedra or both types of tetrahedra . The space between the silicate chains contains water and cations (such as Na + , Ca 2+ for charge balance) and this space is referred to as the interlayer.…”

Section: Introductionmentioning

confidence: 99%

Slag‐fly ash and slag‐metakaolin binders: Part II—Properties of precursors and NMR study of poorly ordered phases

2018

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Sodium silicate‐activated slag‐fly ash binders (SFB) and slag‐metakaolin binders (SMKB) are room‐temperature hardening binders that have excellent mechanical properties and a significantly lower carbon footprint than ordinary Portland cement (OPC). The aim of this study was to use nuclear magnetic resonance (NMR) spectroscopy to study the nanostructure of poorly ordered phases in SFB by varying slag/fly ash ratio, curing time, and curing temperature. Fly ash was completely substituted with metakaolin and the effect of this substitution on the poorly ordered phases was studied. It was observed that the proportion of geopolymer was generally higher in SMKB when compared to SFB. Although C–N–A–S–H and geopolymer coexisted in SFB and SMKB, C–N–A–S–H was the major product phase formed. The mean chain length (MCL) and the structure of C–N–A–S–H gel were estimated as a function of time, temperature, and slag/fly ash ratio. The MCL was found to have a negative correlation with slag/fly ash ratio and Ca/(Si+Al) ratio, but positive correlation with curing temperature. The average Si/Al atom ratios for geopolymers were also estimated. Lastly, the increased proportion of five‐coordinated aluminum (Al(V)) in metakaolin resulted in the decreased unreacted metakaolin in the hardened binder but did not increase the geopolymer content.

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Nevertheless, there is less information on the synergies that appeared during the hydration of C 3 S and b-C 2 S mixtures [17][18][19][20] and the conclusions are contradictory. The knowledge of the behavior of every phase separately will be a reference to establish the degree of synergy in case of the cement.…”

Section: Introductionmentioning

confidence: 99%

Synergy of T1-C3S and β-C2S Hydration Reactions

Hernández

Goñi

Puertas

et al. 2010

Journal of the American Ceramic Society

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The hydration processes of T1‐C3S and β‐C2S and their mixtures 70‐30 and 30‐70 (% in weight) have been followed by conduction calorimetric studies. The synergy of the T1‐C3S and β‐C2S hydration reactions, across their mixtures in proportions of 70‐30 and 30‐70, has been studied through the quantification of the portlandite carried out by thermogravimetric analysis. The hydration reactions and the quantitative evolution of all the components with the time have been studied during a period of 90 days at the room temperature of the laboratory. The microstructure was studied by scanning electron microscopy, the type of silicate tetrahedron, and mean chain length of the C–S–H gel by 29Si magic angle spinning nuclear magnetic resonance, and the porosity and pore‐size distribution by mercury intrusion porosimetry. The main results showed that the hydraulic activity of the β‐C2S strongly increased in the presence of T1‐C3S, mainly at early stages, avoiding its inactive induction period. As a consequence of the increase of the hydraulic activity of the β‐C2S, the pore microstructure is refined and the surface area is diminished.

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A molecular dynamics study of the aluminosilicate chains structure in Al‐rich calcium silicate hydrated (C–S–H) gels

Cited by 69 publications

References 30 publications

Evidence on the Dual Nature of Aluminum in the Calcium‐Silicate‐Hydrates Based on Atomistic Simulations

Evidence on the Dual Nature of Aluminum in the Calcium‐Silicate‐Hydrates Based on Atomistic Simulations

Slag‐fly ash and slag‐metakaolin binders: Part II—Properties of precursors and NMR study of poorly ordered phases

Synergy of T1-C3S and β-C2S Hydration Reactions

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