A Coupled Nanoindentation/SEM‐EDS Study on Low Water/Cement Ratio Portland Cement Paste: Evidence for C–S–H/Ca(OH)<sub>2</sub> Nanocomposites

Chen, Jeffrey J.; Sorelli, Luca; Vandamme, Matthieu; Ulm, Franz‐Josef; Chanvillard, Gilles

doi:10.1111/j.1551-2916.2009.03599.x

Cited by 294 publications

(138 citation statements)

References 61 publications

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“…The literature includes descriptions of slightly different hydration reactions for alite, which lead to calcium silicate hydrate gels with slightly different densities and compositions [5][6][7][8]. Here, we have chosen the Ca-to-Si average ratio of 1.8, because it is compatible with many previous reports, which gave values ranging from 1.7-2.0.…”

Section: Cementssupporting

confidence: 48%

Synchrotron Radiation Pair Distribution Function Analysis of Gels in Cements

et al. 2017

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Abstract:The analysis of atomic ordering in a nanocrystalline phase with small particle sizes, below ≈5 nm, is intrinsically complicated because of the lack of long-range order. Furthermore, the presence of additional crystalline phase(s) may exacerbate the problem, as is the case in cement pastes. Here, we use the synchrotron pair distribution function (PDF) chiefly to characterize the local atomic order of the nanocrystalline phases, gels, in cement pastes. We have used a multi r-range analysis approach, where the~4-7 nm r-range allows determining the crystalline phase contents; the~1-2.5 nm r-range is used to characterize the atomic ordering in the nanocrystalline component; and the~0.2-1.0 nm r-range gives insights about additional amorphous components. Specifically, we have prepared four alite pastes with variable water contents, and the analyses showed that a defective tobermorite, Ca 11 Si 9 O 28 (OH) 2 ·8.5H 2 O, gave the best fit. Furthermore, the PDF analyses suggest that the calcium silicate hydrate gel is composed of this tobermorite and amorphous calcium hydroxide. Finally, this approach has been used to study alternative cements. The hydration of monocalcium aluminate and ye'elimite pastes yield aluminum hydroxide gels. PDF analyses show that these gels are constituted of nanocrystalline gibbsite, and the particle size can be as small as 2.5 nm.

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Section: Cementssupporting

confidence: 48%

Synchrotron Radiation Pair Distribution Function Analysis of Gels in Cements

et al. 2017

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“…The SEM can be used to location the indents and provides a way to determine the mechanical properties of a specific phase [14,15] and the arrangement of the phases of cement paste [16,17]. It is known that the hardness of pure anhydrous materials is higher than their hydrated counterparts [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Microstructure and hardness of cement pastes with mineral admixture

et al. 2017

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Portland cement pastes are highly heterogeneous material and exhibits heterogeneous features over a wide range of length scales. Mechanical properties of microstructure can be determined using depth-sensing indentation. Coupled indentation/SEM technique can be used to location the indents and provides a way to determine the mechanical properties of a specific phase. Thus, the present paper aims to determine the hardness of different phases of cement pastes prepared with different mineral admixtures including sugarcane bagasse ash. The microstructure of cement pastes prepared with different mineral admixtures is analyzed by X ray diffraction, scanning electron microscopy and dynamic hardness tests on polished sections. The different backscatter coefficient allows to differentiate anhydrous phases from C-S-H, calcium hydroxide, silica fume and quartz. A grid of indentation is used to determine the hardness of the different phases and a complete phase segmentation of the different samples is achieved. The results show that the hardness of the different phases follow the sequence (from higher to lower hardness) quartz, anhydrous particles, calcium hydroxide, C-S-H and agglomerated silica fume. The presence of agglomerated silica fume is clearly observed in scanning electron microscopy images and the poor mechanical properties of these areas might compromise the cement pastes. The microstructure of cement pastes prepared with sugarcane bagasse ashes is similar to the observed in samples with crushed quartz.

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“…These aberrant tests may present themselves as irregular loading and/or unloading curves (as shown in Figure 2). In heterogeneous cement-based materials, aberrant test results may occur due to the presence of voids, polishing defects, cracking during indentation, and as noted more recently, composite or "nanocomposite" multiphase response of material present in the interaction region of the indent [13][14][15]. The multiphase response of cement-based materials was a topic of recent discussion in the literature and represents an issue that may diminish the utility of nanoindentation as a quantitative microstructural characterization technique.…”

Section: Resultsmentioning

confidence: 99%

“…In order to further evaluate the possible mechanisms causing the observed degradation in nanomechanical properties, indents likely associated with homogenous C-S-H regions were extracted from the full dataset of non-impacted and impacted RPC specimens. Indents identified as C-S-H were selected based on a Ca:Si between 1 and 2 (consistent with C-S-H) with an elastic modulus between 10 and 50 GPa (range typical for LD and HD C-S-H [10,13]. Out of each dataset, approximately 10% of indents were deemed as homogenous C-S-H. Ca:Si ratios of the C-S-H sub-dataset were 1.44 and 1.42 for non-impacted and impacted specimens, respectively.…”

Section: Resultsmentioning

confidence: 99%

Nanomechanical structure-property relations of dynamically loaded reactive powder concrete

Allison¹,

Moser²,

Chandler³

et al. 2011

Materials Characterisation V

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Low water-to-cement ratio ( w / c ) reactive powder concretes (RPCs) exhibit much higher compressive strengths compared to conventional concrete through optimized particle packing and specialized curing regimes. The high strain-rate impact behavior of RPCs was investigated at the macroscale. However, little work has been done to study the fundamental material behaviors and failure mechanisms of RPC under high strain impact and penetration loads at lower length scales. These high strain-rate loadings have many possible effects on RPCs at the microscale and nanoscale, including alterations in the composition and bonding present in hydrated phases such as calcium silicate hydrate (C-S-H), in addition to fracture and debonding. In this work, the possible chemical and physical changes of RPCs under high strain-rate impact and penetration loads were investigated using a novel technique wherein nanoindentation measurements were spatially correlated with chemical composition using electron microscopy. Results indicate that high strain-rate impacts degrade both the elastic modulus and indentation hardness of RPCs and, in particular C-S-H, with damage likely occurring due to microfracturing and debonding. Additional studies will be required to better understand degradation phenomena within C-S-H itself.

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A Coupled Nanoindentation/SEM‐EDS Study on Low Water/Cement Ratio Portland Cement Paste: Evidence for C–S–H/Ca(OH)₂ Nanocomposites

Cited by 294 publications

References 61 publications

Synchrotron Radiation Pair Distribution Function Analysis of Gels in Cements

Synchrotron Radiation Pair Distribution Function Analysis of Gels in Cements

Microstructure and hardness of cement pastes with mineral admixture

Nanomechanical structure-property relations of dynamically loaded reactive powder concrete

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A Coupled Nanoindentation/SEM‐EDS Study on Low Water/Cement Ratio Portland Cement Paste: Evidence for C–S–H/Ca(OH)2 Nanocomposites

Cited by 294 publications

References 61 publications

Synchrotron Radiation Pair Distribution Function Analysis of Gels in Cements

Synchrotron Radiation Pair Distribution Function Analysis of Gels in Cements

Microstructure and hardness of cement pastes with mineral admixture

Nanomechanical structure-property relations of dynamically loaded reactive powder concrete

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Product

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A Coupled Nanoindentation/SEM‐EDS Study on Low Water/Cement Ratio Portland Cement Paste: Evidence for C–S–H/Ca(OH)₂ Nanocomposites