The article presents the results of studies of the rheological behaviour and plasticity of 3D-printable mixtures. The results of the influence of the type, dosage, and particle size range fillers, and aggregates on the rheological behaviour of mixtures, the stability of their structure, and plasticity under compression are discussed. Two types of 3D-printable mixtures were investigated “cement – filler – plasticizer – water”, “cement – aggregate – plasticizer – water”. A compression test with a constant strain rate of 5 mm/s was used in the experiments. It was found that the best extrusion ability is possessed by mixtures capable of viscoplastic flow without destruction of the structure. For these systems, overcoming the stability threshold and the onset of plastic flow without cracking corresponds to a pressure of 2.5–4 kPa, rational values of plastic yield value are 1.5–3.5 kPa. When fillers and aggregates with mono-particle size are applied, 3D-printable mixtures have low structural stability to the action of loading, they are characterized by irreversible destruction of the structure after overcoming the stability threshold. Fillers and aggregates with multi-particle size range in their particle size range d=1–630 mm can effectively regulate the plasticity and stability of the structure of 3D-printable mixtures. Higher ductility and aggregate stability under load are achieved when fillers with an amorphous structure are used. 3D-printable mixtures are capable of viscous-plastic flow without destruction of the structure and sufficient structural strength at a dosage of fillers (d=1–55 mm) up to 30% of the cement mass, aggregates (d=150–560 mm) in an amount of 100–125% by weight of cement.

G.S. SLAVCHEVA, Doctor of Sciences (Engineering) (This email address is being protected from spambots. You need JavaScript enabled to view it.),
E.A. BRITVINA, Engineer (This email address is being protected from spambots. You need JavaScript enabled to view it.),
M.A. SHVEDOVA, Engineer (This email address is being protected from spambots. You need JavaScript enabled to view it.),
P.Y. YUROV, Engineer (This email address is being protected from spambots. You need JavaScript enabled to view it.)

Voronezh State Technical University (84, 20-letiya Oktyabrya Street, 394006, Voronezh, Russian Federation)

1. Le T.T., Austin S.A., Lim S., Buswell R.A., Gibb A.G.F., Thorpe T. Mix design and fresh properties for high-performance printing concrete. Material and Structure Constraction. 2012. No. 45 (8), pp. 1221–1232. DOI: 10.1617/s11527-012-9828-z
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The modification of silicate composites is an urgent task in building materials science. There is a growing demand on the market for the materials with peculiar properties, suitable for operation in specific conditions. Examples of such materials can be those that have electrically conductive properties, which can be obtained through the addition of conductive functional additives. In this research, the composition of an electrically conductive concrete was developed and its mechanical properties, electrical conductivity, and the microstructure were studied. X-ray microanalysis was also carried out in order to study the chemical composition of the hydration products and modifying additives in the hardened matrix. The additives that were used for the modification of the composition included electrically conductive nickel/carbon nanostructures and dispersed chrysotile nanofibers in combination with a solution of calcium nitrate. Methods for the manufacture and functionalization of additives before their introduction into the cement matrix are described. As a result of the Ni/C nanocomposite introduction, an increase in the strength characteristics and a decrease in electrical resistance of the modified composite are noted, which are due to structural changes in the cement matrix. X-ray microanalysis indicated the formation of new structures in the modified cement matrix. However, the electrical conductivity of the composite with Ni/C dispersions does not show stability and decreases with time. The second part of the research shows the results of the cement matrix modification with a calcium nitrate solution added into the composition together with chrysotile nanofibers. In this case, an ultrafine suspension was preliminary prepared, which made it possible to stabilize the electrical resistivity values during the hardening of the cement stone. It is assumed that the combined introduction of Ni/C nanocomposites with a solution of chemical salts will also allow the stabilization of the electrical resistivity of the composition during hardening.

G.I. YAKOVLEV¹, Doctor of Sciences (Engineering) (This email address is being protected from spambots. You need JavaScript enabled to view it.);
Vit ERNY², Dr.-Engineer (This email address is being protected from spambots. You need JavaScript enabled to view it.);
I.A. PUDOV¹, Candidate of Sciences (Engineering) (This email address is being protected from spambots. You need JavaScript enabled to view it.),
I.S. POLYANSKIKH¹, Candidate of Sciences (Engineering) (This email address is being protected from spambots. You need JavaScript enabled to view it.),
Z.S. SAIDOVA¹, Engineer (This email address is being protected from spambots. You need JavaScript enabled to view it.),
S.N. SEMYONOVA¹, Engineer (post-graduate student) (This email address is being protected from spambots. You need JavaScript enabled to view it.),
E.V. BEGUNOVA¹, Engineer (postgraduate student) (This email address is being protected from spambots. You need JavaScript enabled to view it.)

¹ Kalashnikov Izhevsk State Technical University (7, Studencheskaya Street, Izhevsk, 426069, Russian Federation)
² Faculty of Civil Engineering, Brno University of Technology (Veveří 331/95, 602 00 Brno, Czech Republic)

1. Li Z., Ding S., Yu X., B. Han, J. Ou. Multifunctional cementitious composites modified with nano titanium dioxide: a review. Composites Part A: Applied Science and Manufacturing. 2018. Vol. 111, pp. 115–137. DOI: 10.1016/j.compositesa.2018.05.019.
2. You I., Yoo D.-Y., Kim S., Kim M.-J., Zi G. Electrical and self-sensing properties of ultra-high-performance fiber-reinforced concrete with carbon nanotubes. Sensors. 2017. Vol. 17, pp. 2481. DOI: 10.3390/s17112481
3. Baránek Š., Černý V., Yakovlev G., Drochytka R. Silicate conductive composites with graphite-based fillers. IOP Conf. Series: Materials Science and Engineering. 2021. 1209. DOI: 10.1088/1757-899X/1209/1/012035
4. Ramezani M., Dehghani A., Sherif M.-M. Carbon nanotube reinforced cementitious composites: A comprehensive review. Construction and Building Materials. 2022. Vol. 315. 125100. DOI:10.1016/j.conbuildmat.2021.125100
5. Wang J., Yin J., Kong X. Influences of PCE superplasticizers with varied architectures on the formation and morphology of calcium hydroxide crystals. Cement and Concrete Research. 2022. Vol. 152. 106670. DOI: 10.1016/j.cemconres.2021.106670
6. Yakovlev G.I., Drochytka R., Skripkiunas G., Urkhanova L., Polyanskikh I., Pudov I., Karpova E., Saidova Z., Ali E.M.M. Elrefai. Effect of ultrafine additives on the morphology of cement hydration products. Crystals. 2021. Vol. 11. No. 8. 1002. DOI: 10.3390/cryst11081002
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The information on the state and main trends of the cement market development in Russia in 2021 is given. Data on the volumes and dynamics of production, consumption and foreign trade operations with cement are summarized.

A.A. SEMENOV, Candidate of Science (Engineering), General Director (This email address is being protected from spambots. You need JavaScript enabled to view it.)

LLC “GS-Expert” http://www.gs-expert.ru/