Quantification of Capillary Pores and Hadley Grains in Cement Paste Using Fib-Nanotomography

Holzer, Lorenz; Gasser, Philippe; Muench, B.

doi:10.1007/978-1-4020-5104-3_62

Cited by 13 publications

(14 citation statements)

References 10 publications

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“…However, there is a lack of work in this area compared to, for example, pore-scale modelling of permeability [43][44][45]. More work is needed to characterise the connectivity of the pore structure and crack network in three-dimensions [46][47][48] to advance this area. However, none of the existing three-dimensional imaging techniques are able to image a representative volume of concrete at sufficiently high resolution to capture the pores and cracks important to transport.…”

Section: Discussionmentioning

confidence: 99%

Computational investigation of capillary absorption in concrete using a three-dimensional mesoscale approach

Abyaneh

Wong

Buenfeld

2014

Computational Materials Science

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In many exposure environments, capillary absorption of water controls the rate of deterioration of concrete. This paper presents a three-dimensional numerical investigation of capillary absorption by treating concrete as a heterogeneous composite discretised into a cubic lattice. The lattice elements were considered as conductive "pipes" with transport properties assigned based on the phase they represent. The capillary absorption process was described by a non-linear diffusion equation, with the hydraulic diffusivity a non-linear function of the degree of saturation of the composite. A non-linear finite element method was used to solve the governing differential equations. The numerical results were validated against analytical approximations, as well as experimental data from the literature. A sensitivity analysis was then performed to evaluate the effect of heterogeneities produced by aggregate particles on the absorbed water profile and the sorptivity coefficient. It was found that water penetrates concrete in an uneven profile influenced by the amount, spatial distribution and shape of the aggregate particles. Sorptivity decreased when spherical aggregate particles were replaced with ellipsoidal particles due to the consequent increase in tortuosity of the cement paste. This effect increased with increase in aspect ratio and volume fraction of aggregate. However, the size of aggregate particle appears to have an insignificant influence.Keywords: Concrete; Cement-based materials; Lattice-Network model; Unsaturated flow; Capillary absorption; Aggregate shape; Sorptivity Highlights:• Capillary absorption in concrete was simulated using a three-dimensional model.• Simulations were verified by comparing with experimental results and analytical approximations.• Effects of different variables influencing capillary absorption were investigated.• Sorptivity decreased with an increase in the aspect ratio of the aggregate particles.

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Section: Discussionmentioning

confidence: 99%

Computational investigation of capillary absorption in concrete using a three-dimensional mesoscale approach

Abyaneh

Wong

Buenfeld

2014

Computational Materials Science

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“…After completion of each sectioning process, electron microscopy image of the sectioned surfaces was taken. The further details of the sample preparation procedure are – together with the results of nanoporosity and particular details of FIB‐nt methodology – reported elsewhere (Holzer et al ., 2006).…”

Section: Methodsmentioning

confidence: 99%

Limitation in obtainable surface roughness of hardened cement paste: ‘virtual’ topographic experiment based on focussed ion beam nanotomography datasets

Trtik

Dual

Muench

et al. 2008

Journal of Microscopy

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SummarySurface roughness affects the results of nanomechanical tests. The surface roughness values to be measured on a surface of a porous material are dependent on the properties of the naturally occurring pore space. In order to assess the surface roughness of hardened cement paste (HCP) without the actual influence of the usual sample preparation for nanomechanical testing (i.e. grinding and polishing), focussed ion beam nanotomography datasets were utilized for reconstruction of 3D (nanoscale resolution) surface profiles of hardened cement pastes. 'Virtual topographic experiments' were performed and root mean square surface roughness was then calculated for a large number of such 3D surface profiles. The resulting root mean square (between 115 and 494 nm) is considerably higher than some roughness values (as low as 10 nm) reported in the literature. We suggest that thus-analysed root mean square values provide an estimate of a 'hard' lower limit that can be achieved by 'artefact-free' sample preparation of realistic samples of hardened cement paste. To the best of our knowledge, this 'hard' lower limit was quantified for a porous material based on hydraulic cement for the first time. We suggest that the values of RMS below such a limit may indicate sample preparation artefacts. Consequently, for reliable nanomechanical testing of disordered porous materials, such as hardened cement paste, the preparation methods may require further improvement.

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“…Much smaller features (nm to tens of nm) are analyzed using electron microscopy techniques, eg Focused ion beam/scanning electron microscopy (FIB/SEM) or Scanning Transmission Electron Microscopy (STEM), and X‐Ray ptychography . Representativeness is only achieved at the scale of the cement paste or of the C‐A‐S‐H, owing to significantly smaller samples sizes.…”

Section: Introductionmentioning

confidence: 99%

Mesoscale pore structure of a high‐performance concrete by coupling focused ion beam/scanning electron microscopy and small angle X‐ray scattering

et al. 2018

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This contribution couples (a) Small angle X-ray scattering (SAXS) experiments of a high-performance concrete (HPC) at the millimetric scale, and (b) Focused ion beam/scanning electron microscopy (FIB/SEM) of the cement paste of the HPC, with 10-20 nm voxel size. The aim is to improve the understanding of the 3D pore network of the HPC at the mesoscale (tens of nm), which is relevant for fluid transport. The mature HPC is an industrial concrete, based on pure Portland CEMI cement, and planned for use as structural elements for deep underground nuclear waste storage. Small angle X-ray scattering patterns are computed from the 3D pore images given by FIB/SEM (volumes of 61-118 μm 3 ). They are positively correlated with SAXS measurements (volumes of 5 mm 3 ). Aside from correlations with FIB/SEM data, experimental SAXS allows to investigate a wider range of effects on the pore structure. These are mainly the HPC drying state, the presence of aggregates (by analyzing data on cement paste alone), and the use of Poly Methyl MethAcrylate resin impregnation. K E Y W O R D Sfocused ion beam/scanning electron microscopy, high-performance concrete, mesoscale pore network, small angle X-ray scattering

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Quantification of Capillary Pores and Hadley Grains in Cement Paste Using Fib-Nanotomography

Cited by 13 publications

References 10 publications

Computational investigation of capillary absorption in concrete using a three-dimensional mesoscale approach

Computational investigation of capillary absorption in concrete using a three-dimensional mesoscale approach

Limitation in obtainable surface roughness of hardened cement paste: ‘virtual’ topographic experiment based on focussed ion beam nanotomography datasets

Mesoscale pore structure of a high‐performance concrete by coupling focused ion beam/scanning electron microscopy and small angle X‐ray scattering

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