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Calcium silicate hydrate (C-S-H), the main product in Portland cement hydration, influences the physical and mechanical properties of most cementitious materials. However, there are no structural models that currently relate chemical composition, nanostructure, and microstructure with the physicochemical and mechanical properties. In this work, the indentation technique was used to evaluate the micro/nanomechanical properties of synthetic C-S-H with different Ca/Si (CaO/SiO2) molar ratios. C-S-H was also characterized by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray fluorescence (XRF). Analysis of the results verified that the elastic modulus and hardness increased when the Ca/Si molar ratio of C-S-H decreased, achieving elastic modulus values of 27 and 20 GPa for Ca/Si ratios of 0.7 and 2.1, respectively, corroborating calculations based on the force field method of Manzano et al. Our results also determined that micro- and nanoporosity significantly influence the outcome. The research results are limited to synthesized C-S-H, but clarify the potential of the Ca/Si ratio to modify the mechanical properties, while permitting investigation of C-S-H without the presence of other phases of hydrated Portland cement.

The aim of this work was to investigate the mechanical properties of the titanium anodic films (TiO2) produced by anodic oxidation under galvanostatic conditions, using a 1.4M phosphoric acid electrolyte, with different current densities (J) on commercially pure titanium (cp-Ti). The morphology of the oxide films were observed by scanning electron microscopy (SEM), whereas the composition of the film was determined by Raman spectroscopy. Porosity, average roughness (Ra) and thickness of the TiO2 films increased with the applied J. Hardness and elastic modulus were measured by instrumented indentation technique, and the influence of the substrate was corrected using analytical models. The anodic films presented higher hardness and lower elastic modulus values compared with the cp-Ti.

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