Influence of carbon nanotubes on the effectiveness of plasticizers, hydration and structure of cement-based materials

Ekaterina Karpova

Doctoral dissertation

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This work aims to investigate the effect of multi-walled carbon nanotubes (MWCNT) suspension in combination with plasticizing admixtures (Pl) on the rheological and technological properties of cement-based materials. The study of the cement hydration process, structure and properties of modified cement-based materials were performed.

The different types of Pl, such as lignosulphonate (LS), sulfonated naphthalene formaldehyde condensate (NF) and polycarboxylate ether (PCE) were used in the course of the research. The homogenization of MWCNT in the aqueous suspension was provided by the ultrasonication method. It was established that the usage of PCE contributes to the increase of the average diameter of the particles caused by the intermolecular interactions between the carboxyl groups of the carboxymethyl cellulose (CMC) located on the MWCNT surface and the carboxylate groups of PCE with further formation of the hydrogen bonds.

The rheological properties of cement paste modified by MWCNT suspension with different Pl were tested by the rotational rheometer with coaxial cylinders at 5, 60, 120 min after cement paste mixing. The yield stress, plastic viscosity and shear thinning/ shear thickening indexes were evaluated for the tested cement pastes based on the experimental data and their approximation by the Hershel-Bulkley rheological model. The increase of MWCNT dosages from 0 to 0.24% bwoc provided the changes in rheological properties of cement pastes. The essential reduction of water bleeding and high stability of cement paste were achieved with MWCNT modification.

In addition to the rheological tests, the calorimetry, setting time, structure formation investigation of the cement-based materials with MWCNT and different Pl were undertaken.  The addition of MWCNT caused the acceleration of the Portland cement hydration, increase in total emitted heat and changes in the morphology of the cement hydration products.

The dissertation is сomposed of an introduction, three chapters (literature survey, experimental methodology, and discussion of the results), general conclusions, lists of references, sources, and author's publications on the subject of the dissertation, summary in Lithuanian and seven annexes.

The author has published 12 articles on the topic of the dissertation (two of them in the journals with the citation index referred by the Clarivate Analytics Web of Science).

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DOI: https://doi.org/10.20334/2020-028-M

Book details

Data sheet

Year:
2020
Imprint No:
2020-028-M
Dimensions:
160×240
Pages:
158 p.
Cover:
Softcover
Language:
English
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