Effects of temperature on the atomic structure of synthetic calcium–silicate–deuterate gels: A neutron pair distribution function investigation

White, Claire E.

doi:10.1016/j.cemconres.2015.09.001

Cited by 27 publications

(19 citation statements)

References 30 publications

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“…It is apparent that there are differences in the scale factors according to the type of radiation used (X-rays versus neutrons), especially for mullite, which is attributed to the relatively weak scattering of neutrons from aluminum atoms. Such discrepancies in scale factors according to the type of radiation used have been previously reported in the literature [66]. Peaks positions for the nearest-neighbor atomatom correlations before and after crystalline subtraction are reported in Supplementary Material (Tab.…”

Section: Neutron Pair Distribution Functionssupporting

confidence: 66%

Elucidating the atomic structures of different sources of fly ash using X-ray and neutron PDF analysis

Natali

White

Bignozzi

2016

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This paper presents the comparative results obtained from X-ray and neutron pair distribution function (PDF) analysis aimed at determining the variability in aluminosilicate glass chemistry in five types of class F fly ash (FA). Results have been discussed in light of the complementary information provided by the two methods in order to give a comprehensive overview of FA structure at the nanoscale. The analysis of short range correlations reveals that the bulk glassy structure of FA sources differing in chemical composition are relatively similar, but some specific distinctions in atomic structure are visible in those containing high levels of amorphous VIcoordinated aluminum (e.g., amorphous mullite/alumina), iron and/or carbon (with similar local bonding environment to graphite). The obtained experimental results fill a deficit in literature in the atomic structure and associated variability for class F FA, which is extensively used in several industrial applications including as raw material in alkali-activated cements.

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Section: Neutron Pair Distribution Functionssupporting

confidence: 66%

Elucidating the atomic structures of different sources of fly ash using X-ray and neutron PDF analysis

Natali

White

Bignozzi

2016

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“…As for the magnesium co- The X-ray PDF of Co-0.70 and Co-0.75 and C-S-H ( Figure 5b) bore strong resemblance. According to the literature (Grangeon et al, 2013;Lequeux et al, 1999;Meral et al, 2011;Skinner et al, 2010;White, 2016;White et al, 2015), the correlations peaks might correspond to Si-O distances (r = 1.61 Å The intensity of the correlation peaks assigned to Ca-Ca distances was also lower. These results might suggest the presence of small amounts of M-S-H in the co-precipitated samples, but this again needed to be confirmed by other techniques.…”

Section: Solid Analysismentioning

confidence: 80%

Magnesium and calcium silicate hydrates, Part I: Investigation of the possible magnesium incorporation in calcium silicate hydrate (C-S-H) and of the calcium in magnesium silicate hydrate (M-S-H)

Bernard

Lothenbach

Cau-dit-Coumes

et al. 2018

Applied Geochemistry

108

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Calcium silicate hydrate (C-S-H) and magnesium silicate hydrate (M-S-H) have been described as two separate phases. This work investigates their stability domains and the possible uptake of small amounts of magnesium by C-S-H or, reversely, the uptake of small amounts of calcium by M-S-H. The phases, synthesized by co-precipitation, are characterized using a large panel of techniques (thermogravimetry analysis, X-ray diffraction, X-ray pair distribution function analysis, 29 Si MAS-NMR spectroscopy, 17 measurement of zeta potential and cation exchange capacity) while the compositions of the solutions at 18 equilibrium are determined by ion chromatography and pH measurements. Syntheses of C-S-H samples 19 in the presence of magnesium ((Ca+Mg)/Si = 0.8 and Mg/Si = 0.05 or 0.10) yield two separate phases: 20

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“…Atomic structure of a C-S-H nanolayer is comprised of a pseudo-octahedral Ca-O sheet covered by defective silicate chains and surrounded by interlayer ions and water molecules. 43 The nanoscale structure of the C-S-H is yet the subject of intensive research. 6,10,11,44,45 Although far from perfect, the proposed molecular models based on the so-called defective Tobermorite description can adequately reproduce a wide range of chemo-physical properties and therefore will be the focus of this work.…”

Section: Interaction Bet Ween C-s-h Nanolayersmentioning

confidence: 99%

Nanolayered attributes of calcium‐silicate‐hydrate gels

et al. 2019

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Calcium‐silicate‐hydrates (C–S–H) gel, the main binding phase in cementitious materials, has a complex multiscale texture. Despite decades of intensive research, the relation between C–S–H's chemical composition and mesoscale texture remains experimentally limited to probe and theoretically elusive to comprehend. While the nanogranular texture explains a wide range of experimental observations, understanding the fundamental processes that control particles’ size and shape are still obscure. This paper strives to establish a link between the chemistry of C–S–H nanolayers at the molecular level and formation of C–S–H globules at the mesoscale via the potential‐of‐mean‐force (PMF) coarse‐graining approach. We propose a new thermomechanical load‐cycling scheme that effectively packs polydisperse coarse‐grained nanolayers and creates representative C–S–H gel structures at various packing densities. We find that the C–S–H nanolayers percolate at ~10% packing fraction, significantly below the percolation of ideal hard contact oblate particles and rather close to that of overlapping ellipsoids. The agglomeration of C–S–H nanolayers leads to the formation of globular clusters with the effective thickness of ~5 nm, in striking agreement with small angle neutron and X‐ray scattering measurements as well as nanoscale imaging observations. The study of pore structure and local packing distribution in the course of densification shows a transition from a connected pore network to isolated nanoporosity. Furthermore, the calculated mechanical properties are in excellent agreement with statistical nanoindentation experiments, positioning nanolayered morphology as a finer description of C–S–H globule models. Such high‐resolution description becomes indispensable when investigating phenomena that involve internal building blocks of globules such as shrinkage and creep.

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Effects of temperature on the atomic structure of synthetic calcium–silicate–deuterate gels: A neutron pair distribution function investigation

Cited by 27 publications

References 30 publications

Elucidating the atomic structures of different sources of fly ash using X-ray and neutron PDF analysis

Elucidating the atomic structures of different sources of fly ash using X-ray and neutron PDF analysis

Magnesium and calcium silicate hydrates, Part I: Investigation of the possible magnesium incorporation in calcium silicate hydrate (C-S-H) and of the calcium in magnesium silicate hydrate (M-S-H)

Nanolayered attributes of calcium‐silicate‐hydrate gels

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