A Structural Study of Dehydration/Rehydration of Tobermorite, a Model Cement Compound

Gmira, A.; Pellenq, Roland J.‐M.; Rannou, I.; Duclaux, Laurent; Clinard, C.; Cacciaguerra, Thomas; Lequeux, Nicolas; Damme, H. Van

doi:10.1016/s0167-2991(02)80186-0

Cited by 21 publications

(15 citation statements)

References 17 publications

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“…The central positions of these mass loss peaks, and the total mass losses in each temperature range, do not vary systematically across the sample synthesis temperature range of 7-80°C, which suggests that the equilibration temperature is not the primary factor controlling the interlayer and structural water content of the C-(A-)S-H products formed here. The relationship between temperature and bound water content in tobermorite [40] and hydrated PC pastes [2] is different; these materials dehydrate progressively with increasing temperature over this temperature range. A distinct shoulder at ~200°C is observed in the differential mass loss trace for the Al/Si* = 0.15 sample equilibrated at 20°C ( Figure 3D), which is assigned to strätlingite [41].…”

Section: Thermogravimetric Analysismentioning

confidence: 96%

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

323

130

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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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Section: Thermogravimetric Analysismentioning

confidence: 96%

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

323

130

View full text Add to dashboard Cite

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“…NMR. 29 Si NMR spectra were recorded on a Bruker AVANCE 9.3 T operating at 79.5 MHz and equipped with a 4 mm double bearing MAS probe head spinning at 12 kHz. About 16 000 scans were accumulated after a 45 ° pulse, using a 60 s recycling delay.…”

Section: Sample Characterizationmentioning

confidence: 99%

“…

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mentioning

confidence: 99%

Hydration Properties and Interlayer Organization in Synthetic C-S-H

et al. 2020

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Water in calcium silicate hydrate (C-S-H) is one of the key parameters driving the macroscopic behavior of cement materials, for which water vapor partial pressure has a impact on the Young's modulus and the volumic properties. Several samples of C-S-H with bulk Ca/Si ratio ranging between 0.6 and 1.6 were characterized to study their dehydration/hydration behavior under water-controlled conditions, using 29 Si NMR, water adsorption volumetry, X-ray diffraction, and Fourier-transform near-infrared diffuse reflectance, under various water pressures. Coherent with several previous studies, it was observed that an increase in the Ca/Si ratio is due to the progressive omission of Si bridging tetrahedra, with the resulting charge being compensated for by interlayer Ca and that water conditioning influences the layer-to-layer distance and the achieved NMR spectral resolution. Water desorption experiments exhibit one step toward low relative pressure, accompanied by a decrease in the layerto-layer distance. When sufficient energy is provided to the system (T ≥ 40 °C under vacuum) to remove the interlayer water, the shrinkage/swelling is partially reversible in our experimental conditions. A change in layer-to-layer distance of less than 3 Å is measured in the C-S-H between the wet and dried states. When the bridging SiO 2 tetrahedra are omitted, interlayer Ca interacts with layer O and water interacts with the cations and potentially with the surfaces. This structural organization is interpreted as a mid-plane monolayer of water in the interlayer space, this latter accounting for about 30 % of the volume of C-S-H particles.

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“…As described earlier in the XRD study, this cement had four major hydration products, 1.1 nm tobermorite, calcium silicate hydrate (l), portlandite, and hydrogrossular. According to the literatures [29][30][31], the dehydration of tobermorite and dehydroxylation of hydrogrossular was observed at the temperatures between 50° and 700°C and between 260° and 350°C, respectively. Thus, the fact that hydrogrossular disappeared after 3 cycles was likely to demonstrate the possibility of the phase transformation of hydrogrossular into unknown chemical compounds by its dehydroxylation.…”

Section: Tga Analysismentioning

confidence: 90%

Thermal Shock-resistant Cement

Sugama¹,

Pyatina²,

Gill³

2012

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We studied the effectiveness of sodium silicate-activated Class F fly ash in improving the thermal shock resistance and in extending the onset of hydration of Secar #80 refractory cement. When the dry mix cement, consisting of Secar #80, Class F fly ash, and sodium silicate, came in contact with water, NaOH derived from the dissolution of sodium silicate preferentially reacted with Class F fly ash, rather than the #80, to dissociate silicate anions from Class F fly ash. Then, these dissociated silicate ions delayed significantly the hydration of #80 possessing a rapid setting behavior. We undertook a multiple heating -water cooling quenching-cycle test to evaluate the cement's resistance to thermal shock. In one cycle, we heated the 200C-autoclaved cement at 500C for 24 hours, and then the heated cement was rapidly immersed in water at 25C. This cycle was repeated five times. The phase composition of the autoclaved #80/Class F fly ash blend cements comprised four crystalline hydration products, boehmite, katoite, hydrogrossular, and hydroxysodalite, responsible for strengthening cement. After a test of 5-cycle heat-water quenching, we observed three crystalline phase-transformations in this autoclaved cement: boehmite  -Al 2 O 3 , katoite  calcite, and hydroxysodalite  carbonated sodalite. Among those, the hydroxysodalite  carbonated sodalite transformation not only played a pivotal role in densifying the cementitious structure and in sustaining the original compressive strength developed after autoclaving, but also offered an improved resistance of the #80 cement to thermal shock. In contrast, autoclaved Class G well cement with and without Class F fly ash and quartz flour failed this cycle test, generating multiple cracks in the cement. The major reason for such impairment was the hydration of lime derived from the dehydroxylation of portlandite formed in the autoclaved cement, causing its volume to expand.4

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A Structural Study of Dehydration/Rehydration of Tobermorite, a Model Cement Compound

Cited by 21 publications

References 17 publications

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

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

Hydration Properties and Interlayer Organization in Synthetic C-S-H

Thermal Shock-resistant Cement

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