Generalized Structural Description of Calcium–Sodium Aluminosilicate Hydrate Gels: The Cross-Linked Substituted Tobermorite Model

Myers, Rupert J.; Bernal, Susan A.; Nicolas, Rackel San; Provis, John L.

doi:10.1021/la4000473

Cited by 443 publications

(299 citation statements)

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“…Many papers can now be found in the literature that confirm the presence of Q 3 (nAl) units in the C-A-S-H gels forming during slag alkaline activation (53,63,69,70). One prominent article, authored by Puertas et al (69), reported that in C-A-S-H gels forming in slag activated with a NaOH solution, the existence of tetrahedral Al in bridging positions in the silicate chains goes hand-in-hand with a considerable increase in the number of Q 2 (1Al) units, as well as with a small amount of Q 3 (nAl) units.…”

Section: Fundamentals Of Alkaline Activation In Calcium-rich Systems:mentioning

confidence: 91%

“…This gel was also observed to contain a small amount of alkalis (normally Na), that neutralised the charge imbalance created when a Si is replaced by an Al tetrahedron. Actually, then, these are calcium-sodium aluminosilicate hydrate [C-(N)-A-S-H] gels (70)(71)(72)(73) proposed a model to describe this gel as a mix of cross-linked and non-cross-linked tobermorite-based structures (the cross-linked substituted tobermorite model, CSTM).…”

Section: Fundamentals Of Alkaline Activation In Calcium-rich Systems:mentioning

confidence: 99%

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A review on alkaline activation: new analytical perspectives

et al. 2014

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For many years now the idea of including alkalis in a Portland cement matrix has been regarded as a daft or inexcusably erroneous proposition: despite its absurdity, that opinion has been widely accepted as a basic premise by the scientific and technical community working in the area of the chemistry of cement. In 1957 Glukhovsky proposed a working hypothesis in which he established a close relationship between alkalis and cementitious materials. That hypothesis has become consolidated and has served as a basis for developing a new type of binders, initially called "alkaline cements". The present paper reviews the most significant theoretical interpretations of the role played by alkalis in the formation of the "stony" structure of cement. It ends with a broad overview of the versatility of this type of materials for industrial applications and a discussion of the possibility of building on the existing legislation to meet the need for the future regulation of alkaline cement and concrete manufacture. RESUMEN: Activación alcalina: Revisión y nuevas perspectivas de análisis.Hace algunos años, la sola idea de la presencia de álcalis en una matriz de cemento Portland se consideraba casi como una aberración, o como un error imperdonable; convirtiéndose en un postulado básico (absurdo) ampliamente aceptado por la comunidad científica y técnica vinculada a la química de los cementos. En 1957 Glukhovsky propuso una hipótesis en la que se establecía una estrecha relación entre los álcalis y los materiales cementantes. Hoy día nadie duda de que dicha hipótesis ha servido de base para el desarrollo de una nueva clase de materiales cementantes: "cementos alcalinos". En el presente trabajo se hace una revisión sobre los aspectos teóricos más relevantes del papel de los álcalis en la formación de estos conglomerantes. También se da una visión genérica de su versatilidad, desarrollo industrial y estado de la normativa actual para regular en el futuro la fabricación de cementos y hormigones alcalinos.

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Section: Fundamentals Of Alkaline Activation In Calcium-rich Systems:mentioning

confidence: 91%

Section: Fundamentals Of Alkaline Activation In Calcium-rich Systems:mentioning

confidence: 99%

A review on alkaline activation: new analytical perspectives

et al. 2014

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“…Al substitutes into bridging sites with strong preference over paired sites in these chains [15,16]. It has also been suggested that the aluminosilicate chains in C-(A-)S-H products can cross-link in lowCa (Ca/Si < 1) cements [17] to form disordered analogues of 'double chain' calcium silicate minerals, e.g. 11Å tobermorite [18] ( Figure 1A).…”

Section: Preprint Version Of Accepted Article Please Cite As: Rj Mmentioning

confidence: 99%

Effect of temperature and aluminium on calcium (alumino)silicate hydrate chemistry under equilibrium conditions

Myers

L’Hôpital

Provis

et al. 2015

Cement and Concrete Research

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ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. KeywordsTemperature, Calcium-Silicate-Hydrate (C-S-H), Thermodynamic Calculations, Hydration Products, Blended Cement. AbstractThere exists limited information regarding the effect of temperature on the structure and solubility of calcium aluminosilicate hydrate (C-A-S-H). Here, calcium (alumino)silicate hydrate (C-(A-)S-H) is synthesised at Ca/Si = 1, Al/Si ≤ 0.15 and equilibrated at 7-80°C. These systems increase in phase-purity, long-range order, and degree of polymerisation of C-(A-)S-H chains at higher temperatures; the most highly polymerised, crystalline and crosslinked C-(A-)S-H product is formed at Al/Si = 0.1 and 80°C. Solubility products for C-(A-)S-H were calculated via determination of the solid-phase compositions and measurements of the concentrations of dissolved species in contact with the solid products, and show that the solubilities of C-(A-)S-H change slightly, within the experimental uncertainty, as a function of Al/Si ratio and temperature between 7°C and 80°C. These results are important in the development of thermodynamic models for C-(A-)S-H to enable accurate thermodynamic modelling of cement-based materials. IntroductionTemperatures experienced by cement and concrete based construction materials in service can vary greatly, due to heat evolution from cement hydration, variable ambient environmental conditions, steam curing, and other factors. understanding of the nature of C-S-H and other constituent phases in these systems at equilibrium [6][7][8][9] has meant that hydrated neat PC materials can be accurately described by thermodynamic modelling at temperatures from 5°C to above 80°C [10]. Extending this analysis to the CaO-Al 2 O 3 -SiO 2 -H 2 O system represents a major step toward applying this technique to hydrated PC blends with high replacement levels of supplementary cementitious materials, which are not fully described by existing thermodynamic models [11]. This will enable a much deeper understanding of the chemistry and phase composition, and hence durability, of these materials in service.The chemistry and structure of calcium (alumino)silicate hydrate (C-(A-)S-H) products at ambient conditions have been the subject of sustained research for more than half a...

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“…Samples A and B (empirical formulas 2SiO2·Al2O3 and 4SiO2·Al2O3, respectively) were chosen to represent the range of bulk silicon and aluminium content typically found in fly ashes, with A also representing the approximate composition of metakaolin (see Figure 1) [19]. Samples C, D, E and F (empirical formulas 0.800CaO·SiO2·0.078Al2O3, 1.214CaO·SiO2·0.078Al2O3, 0.709CaO·SiO2·0.026Al2O3 and 1.104CaO·SiO2·0.026Al2O3, respectively) were chosen to enable synthesis of binders exhibiting chemistry in regions of the quaternary CaO -Na2O -Al2O3 -SiO2 system which are important for the study of sodium-and aluminium-substituted calcium silicate hydrate gels, the main reaction product present in alkali-activated slag binders [11,20]. …”

Section: Aluminosilicatesmentioning

confidence: 99%

“…This can be particularly challenging due to the wide variation of chemical and physical characteristics exhibited by commercial geopolymer precursors where a range of chemical reactivity is observed, Postprint of a paper published in Powder Technology, 29(2016): [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Version of record is available at http://dx.doi.org/10.1016/j.powtec.2016.04.006 3 meaning it is often difficult to distinguish reactive from inert species.…”

Section: Introductionmentioning

confidence: 99%