The article presents the results of experimental studies. The optimal time of dispersion of the mixing water together with the nano-additive has been determined. The results of experiments to determine the effect of carbon nanotubes and plasticizer on fine-grained concrete are also presented. Strength characteristics were determined for the studied compositions. Based on the data obtained, the effect of the dispersion time was determined, as well as the effect of the combined use of the SikaVC 5-500 plasticizer and carbon nanotubes "Taunit-M".

Keywords: fine-grained concrete, carbon nanotubes, ultrasonic dispersion, plasticizer

The construction of a Polar gas turbine power plant is carried out on permafrost soils. Features of the construction of reinforced concrete structures of foundations and other elements in the permafrost zone implies high requirements for strength, density and frost resistance. A new composition of the concrete mixture with improved physical and mechanical properties is proposed. Superplasticizing additives and production waste are used in the composition of the concrete mixture.

Keywords: foundation, permafrost, borehole piles, superplasticizer, sulfuric acid sludge, concrete mix, strength, frost resistance

The influence of redispersible polymer powders on the change in the properties of building mortars after holding at high temperature in accordance with GOST R 56387-2018 has been studied. An increase in the compressive strength by 10 – 15% was revealed at a dosage of RPP 2 – 3%. It was found that the introduction of an air-entrapping admixture into the composition has a negligible, up to 5%, negative effect on increasing the compressive strength. The increase in the flexural strength after holding at high temperature was 1.5 – 1.8 times. The decrease in the E-modulus practically does not depend on the dosage of RPP. After holding at high temperature, the E-modulus was 0.8 – 0.84 relative to normal hardening conditions. A decrease in the adhesion strength to the concrete base to values of 0.39 – 0.71 relative to normal hardening conditions was revealed. It is noted that the decrease in adhesion strength significantly depends on prescription factors, with the exception of formulations containing an air-entrapping additive, in which there is practically no decrease in adhesion strength after holding at high temperature.

Keywords: redispersible polymer powders, adhesion strength, E-modulus, compressive and flexural strength, high temperature

Results of research of waste ash-and-slag mixture being a waste product of thermal power plants are presented. Effectiveness of its use as a mineral component of a complex organic-mineral additive is shown. Methodology of mathematical modeling and optimization of properties of concrete modified by complex organomineral additive allowing to reduce cement consumption by 20% without loss of concrete strength is presented.

Keywords: оrganomineral additives, industrial waste, mathematical modelling, cement saving

The article proposes new compositions of a fast-hardening concrete mixture using Portland cement, fine and coarse aggregates, basalt fiber, a complex modifying additive including acetone-formaldehyde resins and magnesium chloride (bischofite). The results of scientific and experimental studies are presented and the influence of the proposed additives on the formation of the structure, rheological and physico-mechanical properties of fast-hardening concrete is determined. Analysis of the test results showed that the proposed formulations, including a complex additive and basalt fiber, contributed to a decrease in the water-cement ratio, increased mobility of the mixture and increased strength of hardened concrete in the early and final hardening periods.

Keywords: concretes, oil and gas storage, modifying additives, fiber, mobility, setting time, strength

This article discusses strength testing of welded joints by pulling joint materials using an automated material testing system.

Keywords: YAG laser welding, packaging of photonic devices, laser processing of materials.