Transmission Electron Microscopy and Microanalytical Studies of Ion‐Beam‐Thinned Sections of Tricalcium Silicate Paste

Groves, G. W.; Sueur, P. J. Le; Sinclair, W.

doi:10.1111/j.1151-2916.1986.tb04746.x

Cited by 80 publications

(38 citation statements)

References 9 publications

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“…The Ca/Si ratios of the C 3 S and the double decomposition groups both increase with Ca concentration, as expected, but two different curves are suggested from the data. Ignoring samples 1c-1g (which are only believed to be in partial equilibrium as discussed below), the Ca/Si ratios of the C 3 S group follow the upper curve, which leads to maximum Ca/Si ratio of ~ 1.8 at CH saturation; this value agrees with EDX [26][27][28][29][30][31] and indirect [24,25] measurements on C 3 S pastes. The Ca/Si ratios of the double decomposition group follow the lower curve, which leads to a maximum Ca/Si ratio of ~ 1.5; this value agrees with other equilibrium studies using double decomposition (Section 5.4).…”

Section: Resultssupporting

confidence: 74%

“…These spacings correspond to the most prominent repeats in the Ca-O layers of both tobermorite and jennite, so it is impossible to conclude solely from XRD evidence which structure better approximates the nanostructure of C-S-H gel. Determinations of the contents of CH and of residual C 3 S [24,25], and microanalyses using the microprobe [26][27][28] or the TEM [29][30][31] indicate a Ca/Si ratio in C-S-H gel of 1.7-1.8. These observations, combined with other evidence from silicate structure, local variations in Ca/Si ratio, selected area electron diffraction patterns, thermogravimetric curves, and density have led to the hypothesis that C-S-H gel is initially a mixture of tobermorite-and jennite-like structures, the latter becoming increasingly dominant, and ultimately solely present, with age [32].…”

Section: (Ch) C-s-h Gel Is Even Less Ordered Than C-s-h(i) or C-s-h(ii)mentioning

confidence: 99%

“…In contrast, C-S-H gel in C 3 S pastes has a high Ca-OH content [36] and invariably obtains a high Ca/Si ratio of 1.8 when coexisting with portlandite [24][25][26][27][28][29][30][31]; C-S-H gel thus tends to jennite-like phases that equilibrate near curve C. These trends therefore suggest that the structures of synthetic C-S-H and C-S-H gel from C 3 S pastes are generally (but not always) distinct. Moreover, it may be misleading in some instances to extrapolate conclusions about the nanostructure of C-S-H gel from data on synthetic C-S-H, especially those produced from double decomposition.…”

Section: Differences Between Synthetic C-s-h and C-s-h Gelmentioning

confidence: 99%

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Solubility and structure of calcium silicate hydrate

Chen

Thomas

Taylor³

et al. 2004

Cement and Concrete Research

721

414

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C-S-H, the poorly crystalline calcium silicate hydrate formed in cement paste and aqueous suspension, is characterized by extensive disorder and structural variations at the nanometer scale. An analysis of new and published solubility data for C-S-H formed by different preparation methods and with a broad range of compositions illustrates a previously unrecognized family of solubility curves in the CaO-SiO 2 -H 2 O system at room temperature. As demonstrated by 29 Si magic-angle spinning (MAS) NMR data and by charge balance calculations, the observed differences in solubility arise from systematic variations in Ca/Si ratio, silicate structure, and Ca-OH content. Based on this evidence, the family of solubility curves are interpreted to represent a spectrum of metastable C-S-H phases whose structures range from purely tobermorite-like to largely jennite-like. These findings give an improved understanding of the structure of these phases and reconcile some of the discrepancies in the literature regarding the structure of C-S-H at high Ca/Si ratios.

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Section: Resultssupporting

confidence: 74%

Section: (Ch) C-s-h Gel Is Even Less Ordered Than C-s-h(i) or C-s-h(ii)mentioning

confidence: 99%

Section: Differences Between Synthetic C-s-h and C-s-h Gelmentioning

confidence: 99%

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Solubility and structure of calcium silicate hydrate

Chen

Thomas

Taylor³

et al. 2004

Cement and Concrete Research

721

414

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show abstract

“…One of the key issues in designing a realistic C-S-H molecular model is the calcium-to-silicon ratio (C/S). Indeed, confirming earlier measurements by Groves et al (6) and Richardson and Groves (7), energy dispersive X-ray analyses of C-S-H in hardened Portland cement pastes aged 1 day to 3.5 years reveal a composition variation spanning C/S from approximately 1.2 to 2.3 with a mean value of 1.7; this variation also depends on the water-to-cement (W/C) mass ratio at which cement is hydrated (5). Given the shortfalls of the natural analogs, tobermorite and jennite, to meet this compositional constraint, Richardson proposed a two-fold classification to clarify C-S-H chemistry (5).…”

supporting

confidence: 92%

“…Much of our knowledge of C-S-H has been obtained from structural comparisons with crystalline calcium silicate hydrates, based on HFW Taylor's postulate that real C-S-H was a structurally imperfect layered hybrid of two natural mineral analogs (2) 6 .8H 2 O (4)]. While this suggestion is plausible in morphological terms, this model is incompatible with two basic characteristics of real C-S-H; specifically the calcium-tosilicon ratio (C/S) and the density.…”

mentioning

confidence: 99%

A realistic molecular model of cement hydrates

Pellenq

Kushima²,

Shahsavari³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

787

533

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Despite decades of studies of calcium-silicate-hydrate (C-S-H), the structurally complex binder phase of concrete, the interplay between chemical composition and density remains essentially unexplored. Together these characteristics of C-S-H define and modulate the physical and mechanical properties of this ''liquid stone'' gel phase. With the recent determination of the calcium/silicon (C/S ‫؍‬ 1.7) ratio and the density of the C-S-H particle (2.6 g/cm 3 ) by neutron scattering measurements, there is new urgency to the challenge of explaining these essential properties. Here we propose a molecular model of C-S-H based on a bottom-up atomistic simulation approach that considers only the chemical specificity of the system as the overriding constraint. By allowing for short silica chains distributed as monomers, dimers, and pentamers, this C-S-H archetype of a molecular description of interacting CaO, SiO2, and H2O units provides not only realistic values of the C/S ratio and the density computed by grand canonical Monte Carlo simulation of water adsorption at 300 K. The model, with a chemical composition of (CaO)1.65(SiO2)(H2O)1.75, also predicts other essential structural features and fundamental physical properties amenable to experimental validation, which suggest that the C-S-H gel structure includes both glass-like short-range order and crystalline features of the mineral tobermorite. Additionally, we probe the mechanical stiffness, strength, and hydrolytic shear response of our molecular model, as compared to experimentally measured properties of C-S-H. The latter results illustrate the prospect of treating cement on equal footing with metals and ceramics in the current application of mechanism-based models and multiscale simulations to study inelastic deformation and cracking.atomistic simulation ͉ mechanical properties ͉ structural properties B y mixing water and cement, a complex hydrated oxide called calcium-silicate-hydrate (C-S-H) precipitates as nanoscale clusters of particles (1). Much of our knowledge of C-S-H has been obtained from structural comparisons with crystalline calcium silicate hydrates, based on HFW Taylor's postulate that real C-S-H was a structurally imperfect layered hybrid of two natural mineral analogs (2) (4)]. While this suggestion is plausible in morphological terms, this model is incompatible with two basic characteristics of real C-S-H; specifically the calcium-tosilicon ratio (C/S) and the density. Recently, small-angle neutron scattering measurements have fixed the C/S ratio at 1.7 and the density at 2.6 g/cm 3 (1), values that clearly cannot be obtained from either tobermorite (C/S ϭ 0.83, 2.18 g/cm 3 ) or jennite (C/S ϭ 1.5 and 2.27 g/cm 3 ). From the standpoint of constructing a molecular model of C-S-H, this means that these crystalline minerals are not strict structural analogs. Here we adopt the perspective that the chemical composition of C-S-H is the most essential property in formulating a realistic molecular description. We show that once the C/S ratio is described...

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The Structure, Stoichiometry and Properties of C-S-H Prepared by C3S Hydration Under Controlled Condition

Nonat

Lecoq

1998

Nuclear Magnetic Resonance Spectroscopy of Cement-Based Materials

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Transmission Electron Microscopy and Microanalytical Studies of Ion‐Beam‐Thinned Sections of Tricalcium Silicate Paste

Cited by 80 publications

References 9 publications

Solubility and structure of calcium silicate hydrate

Solubility and structure of calcium silicate hydrate

A realistic molecular model of cement hydrates

The Structure, Stoichiometry and Properties of C-S-H Prepared by C3S Hydration Under Controlled Condition

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