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363 results on '"Zhdanok, S."'

27. Investigation of the Structure of a Cement Composite Modified by Hydrothermal SiO2 Nanoparticles and MCNT Nanoparticles by the X-Ray Phase Analysis Method.

Author

Polonina, E. N., Potapov, V. V., Zhdanok, S. A., and Leonovich, S. N.

Subjects
CEMENT composites, COMPOSITE structures, MULTIWALLED carbon nanotubes, SMALL-angle X-ray scattering, PORTLAND cement, NANOPARTICLES, X-rays
Abstract

The x-ray phase analysis method has been used to study the effects of small doses of hydrothermal SiO2 nanoparticles and nanoparticles of multiwalled carbon nanotubes (MCNTs) on the structure of a Portland cement composite separately and in a combination at the age from 4 h to 28 days. It has been established that clinker minerals and Portlandite components do not differ significantly in nanomodified specimens compared to control specimens, which agrees with the thermogravimetrical data for the ages of 1 and 28 days. In the region of the angles 2θ = 5–12 degrees, structural differences were identified for the CSH gel in the nanomodified specimens: at the age of 1 day (24 h), there were CSH peaks (I) in the diffraction patterns of the modified specimens with Basel distances of 12.44–12.54 Å between the layers. At the age of 28 days, relatively higher peaks of a tobermorite-like structure were identified with a Basel distance reaching a maximum value of 14.54 Å in a specimen modified by a combination of SiO2 and MCNT nanoparticles. The increase in the Basel distances corresponds to a reduction in the values of the Ca/Si ratio and an improvement in the ordering of the CSH-gel structure and agrees with the IR-spectroscopy data having shown the higher degree of polymerization of silicon–oxygen tetrahedrons in nanomodified specimens. [ABSTRACT FROM AUTHOR]

Published
2023
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28. Studying the Structure of a Cement Composite Modified by Hydrothermal SiO2 Nanoparticles and MCNTs by the IR-Spectroscopy Method.

Author

Polonina, E. N., Potapov, V. V., Zhdanok, S. A., and Leonovich, S. N.

Subjects
CEMENT composites, COMPOSITE structures, MULTIWALLED carbon nanotubes, PRECIPITATION hardening, NANOPARTICLES, TETRAHEDRA
Abstract

The influence of hydrothermal small doses of SiO2 nanoparticles (NPs) and multiwalled carbon nanotubes (MCNTs) separately and combined with adding a polycarboxylate superplasticizer (SP) at the water–cement ratio W/C = 0.21 has been studied by the IR-spectroscopy method. From the shift of the frequency of absorption of silicon–oxygen tetrahedrons SiO4 to the region of reciprocal electromagnetic-radiation (EMR) wavelengths 900–1100 cm–1, it has been established that the nanoparticles added increase their kinetics and the degree of their polycondensation. The influence on the degree of polycondensation of silicon–oxygen tetrahedrons was more significant than on the rate of hydration of clinker minerals and the gross amounts of hydration products of cement. The effect of influence on the kinetics and the degree of polycondensation of silicon–oxygen tetrahedrons depended on the chemical composition of the added nanoparticles (SiO2, MCNTs, and SiO + MCNTs) and on the age of hardening of the cement composite: it was more pronounced at the age of 28 days than at the age of 1 day for the combination of nanoparticles (SiO2 + MCNTs) and was absent at the age of 4 h. Increase in the dehree of polycondensation of silicon–oxygen tetrahedrons corresponds to the rise in the crystallinity of a CSH gel and to the increase in the volume density of packing of nanogranules of the gel, and also determines the increment in the mechanical characteristics of the cement composite. [ABSTRACT FROM AUTHOR]

Published
2022
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