A Coupled Nanoindentation/SEM‐EDS Study on Low Water/Cement Ratio Portland Cement Paste: Evidence for C–S–H/Ca(OH)2 Nanocomposites
By Jeffrey J. Chen, Luca Sorelli, M. Vandamme, Franz-Josef Ulm, G. Chanvillard. 2010
372 citations recorded by the source corpus.
A low water/cement ratio (w/c=0.20) hydrated Portland cement paste was analyzed by grid-indentation coupled with ex situ scanning electron microscope-energy-dispersive X-ray spectra (SEM-EDS) analysis at each indentation point. Because finite element and Monte-Carlo simulations showed that the microvolumes probed by each method are of comparable size (approximately 2 μm), the mechanical information provided by nanoindentation was directly comparable to the chemical information provided by SEM-EDS. This coupled approach provided the opportunity to determine whether the local indentation response was a result of a single- or a multiphase response--the latter being shown predominant in the highly concentrated w/c=0.20 hydrated cement paste. Results indicate that, in the selected microvolumes where C-S-H and nanoscale Ca(OH)2 (CH) are present, increasing fractions of CH increase the local indentation modulus (and hardness), yielding values above those reported for high-density (HD) C-S-H. Micromechanical analyses show that C-S-H and CH are associated, not merely as a simple biphase mixture, but as an intimate nanocomposite where nanoscale CH reinforces C-S-H by partially filling the latter's gel pores. The paper discusses the mechanism of forming the C-S-H/CH nanocomposite, as well as the impact of nanocomposites on various macroscopic properties of concrete (e.g., shrinkage, expansion). On a general level, this study illustrates how a coupled nanoindentation/X-ray microanalysis/micromechanics approach can provide otherwise inaccessible information on the nanomechanical properties of highly heterogeneous composites with intermixing at length scales smaller than the stress field in a nanoindentation experiment.
Subfields: Civil and Structural Engineering
View Paper: https://www.semanticscholar.org/paper/4f8759a41862d39cf90db3694c78e0cc9bfe927f
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In Civil and Structural Engineering
Citations in the corpus
- A review on the mechanical properties of cement-based materials measured by nanoindentation (2015, methodology): “UHD phase was found to be a composite of HD C–S–H and nano-CH by coupled nanoindentation/SEM (scanning electron microscope)-EDX (energy-dispersive X-ray spectroscopy) analysis [4].”
- Nanomechanical characteristics of interfacial transition zone in nano-engineered concrete (2021, background): “5%), are similar to the two-scale random limit packing density (87%) [44,51].”