The microstructure of dispersed and non-dispersed fresh cement pastes — New insight by cryo-microscopy

Zingg, Anatol; Holzer, Lorenz; Kaech, Andres; Winnefeld, Frank; Pakusch, Joachim; Becker, Stefan; Gauckler, Ludwig J.

doi:10.1016/j.cemconres.2007.11.007

Cited by 122 publications

(65 citation statements)

References 21 publications

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“…The study presented here is part of a project where macroscopic phenomena of cementitious suspensions containing superplasticizers [15][16][17] are linked to their microstructural evolution [18,19] during early hydration up to setting. This paper aims to contribute to a better understanding of the interaction mechanisms of PCE with cement of different C 3 A-contents (all cements are CEM I 42.5 N types) in fresh cement pastes.…”

Section: Introductionmentioning

confidence: 99%

Interaction of polycarboxylate-based superplasticizers with cements containing different C3A amounts

Zingg

Winnefeld

Holzer

et al. 2009

Cement and Concrete Composites

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279

110

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Section: Introductionmentioning

confidence: 99%

Interaction of polycarboxylate-based superplasticizers with cements containing different C3A amounts

Zingg

Winnefeld

Holzer

et al. 2009

Cement and Concrete Composites

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279

110

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“…For this purpose the solution can be vitrified with high pressure freezing~Bachmann & Mayer, 1987;Moor, 1987;Monaghan et al, 1998!. Because it is beyond the scope of this article to discuss the details of high pressure freezing and of cryoimaging, we are referring to previous publications about cryo-FIB applications on cement suspensions Holzer et al, 2007;Zingg et al, 2008!. With the present case study, we intend to evaluate the methodological reproducibility of particle analysis based on cryo-FIB-nt.…”

Section: Case Study 3: Reproducibility Test For Cryo-fib-nt and Influmentioning

confidence: 99%

“…Recently, the high-resolution focused ion beam nanotomography~FIB-nt! technique has been adapted for cryoimaging, and first quantitative results were presented for cement suspensions~Holzer et al, 2007;Zingg et al, 2008!. In the present article the methodological requirements for representative particle analysis with~cryo-!FIB-nt are critically evaluated.…”

Section: Introductionmentioning

confidence: 99%

Toward Reproducible Three-Dimensional Microstructure Analysis of Granular Materials and Complex Suspensions

Holzer¹,

Münch²

2009

Microsc Microanal

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Focused ion beam nanotomography~FIB-nt! is a novel method for high resolution three-dimensional 3D! imaging. In this investigation we assess the methodological parameters related to image acquisition and data processing that are critical for obtaining reproducible microstructural results from granular materials and from complex suspensions. For this purpose three case studies are performed:~1! The precision of FIB-nt is evaluated by analyzing a reference sample with nanospheres. Due to the implementation of an automated correction procedure, drift phenomena can be removed largely from the FIB data. However, at high magnifications remaining drift components can induce problems for 3D-shape reconstructions.~2! Correct object recognition from densely packed microstructures requires specific algorithms for splitting of agglomerated particles. To establish quantitative criteria for the correct degree of splitting, a parametric study with dry portland cement is performed. It is shown that splitting with a k-value of 0.6 leads to accurate results. 3! Finally, the reproducibility of the entire cryo-FIB analysis is investigated for high pressure frozen cement suspensions. Reproducible analyses can be obtained if the magnification is adapted to the particle size. At low magnifications the small particles and their surface area are underestimated. At high magnifications representativity is questioned because local inhomogeneities can become dominant.

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“…In cement, calcium silicate hydrate (C-S-H) as the main hydration product precipitates on the surface of un-reacted particles and causes aggregation of the particles into grains. Then interparticle forces will increase not just because of greater forces between C-S-H layers but also due to an increase in surface area of the particles (Gauffinet-Garrault 2012), although the roles of ettringite phases could be equally important at the early age of cement hydration because of rapid formation of these products and their roles in adsorption of chemical plasticizers (Plank and Hirsch 2007, Rossler et al 2008, Zingg et al 2008. Calcium (sodium) aluminosilicate hydrate as the main product of alkali-activated slag could behave similarly although it has not yet been studied in sufficient detail.…”

Section: Measuring Time-resolved Yield Stress Of Evolving Cementitioumentioning

confidence: 99%

Time-resolved yield stress measurement of evolving materials using a creeping sphere

Kashani

Provis

Deventer³

et al. 2015

Rheol Acta

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Physico-chemical phenomena influenced by aging or reaction can result in rheological changes across several orders of magnitude, but the classical rheometry methods available for analysis of concentrated suspensions can face challenges in correctly measuring the yield stress of aging/reacting (evolving) materials and need some precautions to enable precise measurement of the evolution of the yield stress with time. Here, a creeping sphere method has been applied to measure time-resolved yield stress; the force required to pull a solid sphere at very low velocity is used to calculate yield stress using previous analytical solutions for local flow of a creeping sphere in yield stress materials. The measured yield stress values agree well with the data recorded using vane-in-cup geometry for timeindependent measurements using Carbopol gel. The creeping sphere is less affected by shear history because of the constantly changing shear region, and therefore measures yield stress changes in evolving materials such as cement for a long time period in a single run, without altering ongoing structural network bond formation.

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The microstructure of dispersed and non-dispersed fresh cement pastes — New insight by cryo-microscopy

Cited by 122 publications

References 21 publications

Interaction of polycarboxylate-based superplasticizers with cements containing different C3A amounts

Interaction of polycarboxylate-based superplasticizers with cements containing different C3A amounts

Toward Reproducible Three-Dimensional Microstructure Analysis of Granular Materials and Complex Suspensions

Time-resolved yield stress measurement of evolving materials using a creeping sphere

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