On the reaction of C-S-H(di, poly) with alkali hydroxides

Stade, H.

doi:10.1016/0008-8846(89)90051-3

Cited by 89 publications

(86 citation statements)

References 8 publications

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“…The steep drop in the calculated alkali content of the pore solution reflects the increased uptake of alkalis in more Si-rich C-S-H phases as observed experimentally on synthetic C-S-H [78,83]. The general decrease of the alkali and hydroxide concentrations predicted by the thermodynamic model agrees well with the experimental data, except in the case of sodium, where the experimental data show no decrease.…”

Section: Fly Ashsupporting

confidence: 80%

“…The strong pozzolanic reaction increases the amount of C-S-H formed and leads to the formation of C-S-H phases with lower Ca/ Si ratio. These C-S-H phases take up more alkalis [78,83]. Due to the higher reaction degree of SF compared to FA and the higher silicon content, the reduction of alkalis is much stronger than for FA (compare Fig.…”

Section: Alkali and Hydroxide Concentrationsmentioning

confidence: 99%

“…This trend to lower alkali concentration is accentuated during hydration, as the alkalis which are released from the dissolving FA are bound to the reaction products. The pozzolanic reaction leads to C-A-S-H phases with lower Ca/Si ratio, which take up more alkalis than high Ca/Si C-S-H [78,83].…”

Section: Alkali and Hydroxide Concentrationsmentioning

confidence: 99%

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The pore solution of blended cements: a review

et al. 2015

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This paper is the work of working group 3 of the RILEM Technical Committee on Hydration and Microstructure of Concrete with SCM (TC 238-SCM). The pore solution is an essential but often overlooked part of hydrated cements. The composition of the cement pore solution reflects the ongoing hydration processes and determines which solid phases are stable and may precipitate, and which phases are unstable and may dissolve. The study of the cement pore solution therefore contributes to the understanding of the mechanisms as well as of the kinetics of cement hydration. This paper reviews the impact of supplementary cementitious materials (SCMs) on the pore solution composition of blended cements. In a first part, the extraction and analysis methods of cement pore solutions are reviewed, leading to a set of practical guidelines and recommendations. In a second part, an extensive literature survey is used to document the effect of the addition of SCMs (blast furnace slag, fly ash and silica fume) on the pore solution. Finally, in a third part the collected literature data are compared to thermodynamic simulations. The performance and current limitations of thermodynamic modelling of blended cement hydration are demonstrated and discussed in view of future progress.

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Section: Fly Ashsupporting

confidence: 80%

Section: Alkali and Hydroxide Concentrationsmentioning

confidence: 99%

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The pore solution of blended cements: a review

et al. 2015

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“…Many studies also showed that there is no significant 3.0 w/c=0.6, 10% Na 2 O by mass Mean chain length of C-S-H 3.6 3.1 w/c=0.5, the same as above (Mendoza et al 2015) difference between the amount of Na and K uptake in C-S-H (Stade 1989;Hong and Glasser 1999;L'Hôpital et al 2016). However, some studies suggested that the binding capabilities are different for different types of alkali cations (e.g.…”

Section: +mentioning

confidence: 99%

Effect of Alkalis on Cementitious Materials:Understanding the Relationship between Composition, Structure, and Volume Change Mechanism

Radlińska

2017

ACT

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Journal of Advanced AbstractPrevious studies demonstrated that alkalis can considerably affect the volumetric properties of hardened cementitious binders, including shrinkage, creep, and micro-cracking. The objective of this paper is to reexamine the effect of alkalis on the composition, nanostructure, phase stability, and morphology of calcium-silicate-hydrate (C-S-H) in cementitious materials, and to further propose a conceptual model bridging the C-S-H characters with its volume change mechanisms in alkali-enriched systems. The proposed microstructural model is an extension of the colloidal model of C-S-H considering the effect of alkalis. It is suggested that the presence of alkalis makes C-S-H more thermodynamically unstable and structurally disrupted, and easier to reorganize and redistribute upon drying-induced internal stresses or external loading. In addition, new experimental results regarding the influence of lithium on shrinkage and micro-cracking of alkali-activated blast-furnace slag are discussed. It shows that lithium addition can dramatically improve the cracking resistance and volumetric stability of alkali-activated slag.

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“…There are some references related to alkali sorption of C-S-H gel (Stade 1989;Hong and Glasser 1999;Bach et al 2013). Among them Hong and Glasser (1999) performed an experiment for C-S-H gel with different Ca/Si molar ratios from 0.85 to 1.8 and different concentrations of alkaline solution (1 -300 mmol/l).…”

Section: Model For Alkalinity Of Pore Solutionmentioning

confidence: 99%

Evaluation of Alkalinity of Pore Solution Based on the Phase Composition of Cement Hydrates with Supplementary Cementitious Materials and its Relation to Suppressing ASR Expansion

Kawabata

Yamada

2015

ACT

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A model to evaluate quantitatively the alkalinity of pore solution based on phase composition of cement hydrates with SCMs was proposed and was compared with suppressing effect of ASR expansion. The model is devised from the perspective of alkali sorption by C-S-H gel, and the parameters for calculation can be evaluated thanks to phase composition analysis such as XRD/Rietveld analysis and selective dissolution. The experimental results have shown that ASR expansion is strongly correlated to the alkalinity of the pore solution, which can be calculated with the proposed model. Based on the results, the ASR suppressing effects of SCMs are converted to the reduction in total alkali content as available alkali content. Finally, the required replacement level of SCM with the proposed model was compared to the CSA A23.2-27A standard based on numerous experiments and field experiences in Canada. The calculated result was well consistent with the minimum replacement level of SCMs specified in CSA A23.2-27A. A subsequent interpretation of this study supports that the dominant mechanism of SCMs for ASR suppression is a reduction of alkalinity of pore solution.

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On the reaction of C-S-H(di, poly) with alkali hydroxides

Cited by 89 publications

References 8 publications

The pore solution of blended cements: a review

The pore solution of blended cements: a review

Effect of Alkalis on Cementitious Materials:Understanding the Relationship between Composition, Structure, and Volume Change Mechanism

Evaluation of Alkalinity of Pore Solution Based on the Phase Composition of Cement Hydrates with Supplementary Cementitious Materials and its Relation to Suppressing ASR Expansion

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