Methodology of Study of the Structure of Cement Materials by the Method of Nanoindentation

Abstract

The parameters of the nanoindentation method were selected to ensure the final consistent results were obtained. These results are presented by histograms of the distribution of nanoindentation points by elasticity and hardness moduli and distributions by these characteristics in the horizontal XY plane perpendicular to the movement of the nanoindenter. It was revealed that the elastic modulus increases in samples that contain a complex additive containing nano-sized particles. The effect is also observed when introducing an additive containing only one type of nanoparticles (hydrothermal SiO 2 nanoparticles or multiwalled carbon nanotubes MWCNTs. Studies of cement stone samples at W/C = 0,21 and the content of SiO 2 in the combined additive is 0,000006 wt. % and MWCNT 0,00004 wt. % for cement showed that the effect of nanoparticles on the structure of the CSH gel becomes more pronounced, because the volume fraction of the LD phase of the CSH gel with a low packing density of nanograins becomes significantly lower than the fraction of the HD phase with an increased hexagonal packing density of granules. The results obtained indicate that there is a change in the nanostructure of the C−S−H gel, which is compared with an increase in strength, Young's and shear moduli with the introduction of SiO 2 nanoparticles and MWCNT nanoparticles. Using the nanoindentation method, it becomes possible to explain the nanogranular nature of the CSH gel, which is characteristic and determined by the contact forces of the CSH gel particles for these phases.