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

Abstract

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

Microscopic Factors Affecting the Performance of Pervious Concrete

“…These include studies of the design of the mix ratio [2][3][4][5], the influence of the aggregate particle size [6][7][8][9][10] and type [11,12] on the performance and porosity [13][14][15][16], the relationship between permeability and the mechanical properties of pervious concrete [17,18], and fatigue performance [19][20][21][22]. However, most scholars have not extensively investigated the fine-scale parameters of pervious concrete to analyze its pore structure characteristics, except through electron microscopy [23], computed tomography scanning reconstruction [24], and the piezomercury method [25].…”

Advanced characterisation of 3D structure and porosity of ordinary portland cement (OPC) mortar using plasma focused ion beam tomography and X‐ray computed tomography

“…However, it is not technologically relevant to the large‐scale and heterogeneous structure of cement. To obtain appropriate statistics, it is necessary that multiple samples with volumes of tens of mm 3 be prepared to study macroscopic fluid transport property for aggregate sizes of tens of mm 15 . Nano‐ and micro‐computed X‐ray tomography (CT) allows 3D visualisation up to millimetric scale, with a maximum resolution of 50 nm for nano‐CT 16 , while other advanced synchrotron‐based tools further enhance the capability of understanding cement systems with the ultimate resolutions of 10 nm 17 .…”

“…Holzer et al 22 presented the first application of cryo-FIB-nanotomography for quantifying particle structure in dense cement suspensions by etching the specimen at −105 • C for 4 min and transferring it onto the cold stage (−115 • C), followed by FIB-milling and imaging processes with electron beam voltage and spot size of 3 kV and spot 3, respectively. Brisard et al 15 promoted the understanding of potential fluid transport and 3D pore network and microstructure (10-20 nm voxel size) combining with small angle X-ray scattering and FIB/SEM experiments, in which four samples (volumes of 61-118 μm 3 ) were required on a Ga + FIB/SEM system. Lim et al 23 implemented FIB tomography on cement pastes incorporating nanosilica and silica fume from 1000 images with dimensions of 10 × 10 × 20 μm.…”

Reconstruction of calcium silicate hydrates using multiple 2D and 3D imaging techniques: Light microscopy, μ‐CT, SEM, FIB‐nT combined with EDX

“…This enables a cross‐scale 3D‐representation of the microstructure of hydrated alite using a single specimen. Comparable cross‐scale examinations using at least some of these methods were already done, for example, for coal, 2 clay material 3 and hydrated cement 4,5 .…”

“…This can be overcome using the FIB‐nT, which is already widely adopted in material science 2–5,9,10 . It utilises a gallium ion beam to cut layer by layer of a material volume and then using the various detectors available in a SEM to image and analyse the revealed surface.…”