The results of experimental studies on the use of fly ash of thermal power plants for the production of high-strength concrete or the replacement of part of the cement in the concrete mixture with TPP ash are presented. The results of experimental studies show the high efficiency of the multifunctional complex APP (fly ash⁺) developed on the basis of fly ash of thermal power plants in the production of high-grade concretes and the possibility of replacing a significant part of cement in the concrete mixture. To obtain high-strength concretes, the amount of APB (fly ash⁺) additionally introduced into the concrete mixture is from 5 % to 100 % of the cement mass. At the same time, an increase in the strength of concrete by 2–2.3 times in comparison with the strength of the concrete of the base composition can be achieved. The replacement of a part of cement in the concrete mixture with a multifunctional complex of APB (fly ash⁺) in an amount from 5 % to 80 % makes it possible to preserve the strength of concrete at the strength level of the concrete base composition. The possibility of utilization of practically unlimited volumes of coal burning waste and reduction of cement consumption in concrete mixtures is shown. At the same time, the anthropogenic impact on the biosphere and the size of the carbon footprint are reduced, both in the production of thermal and electrical energy, and in the production of cement.

The results of experimental studies of fire resistance of slab structures made of fibroconcrete with the addition of fiberglass macrofiber are presented. Full-scale plates of solid cross-section with steel reinforcement and glass composite reinforcement were subjected to fire tests. During the experiments, the possibility of increasing the fire resistance limit of plates with composite reinforcement due to the introduction of fiberglass macrofiber into concrete, by analogy with polypropylene microfiber, was checked. According to the research results, it was found that the introduction of fiberglass macrofiber into concrete does not increase the fire resistance limit by loss of bearing capacity of slab structures, but increases the intensity of explosion-like destruction of concrete and the degree of damage to the heated surface in case of fire, and in thin-walled structures with a thickness of 50 mm leads to the formation of through cracks, holes and the onset of the fire resistance limit by loss of integrity. In addition, fiberglass macrofibre has increased toxicity in case of fire, which makes it necessary to limit the scope of its application for housing, public and industrial buildings, especially various types of tunnels where the operation of objects is associated with the mass stay of people.

The results of field studies of bored piles using a complex methodology, including tests by the seismo-acoustic method and the method of ultrasonic inter-well monitoring, are presented. Complex tests made it possible to assess not only the uniformity of the pile shaft , the presence of various kinds of defects, but also made it possible to determine the compressive strength of the concrete of the pile shaft along its entire length. This is especially important because the piles will be subjected to loads of about 1000 tons. Ultrasonic inter-well monitoring, in addition to the seismo-acoustic method, makes it possible to get a more realistic picture of the pile structure, as well as to give the technologist and designer strength indicators of structural concrete piles with a step of 500 mm along the length of the trunk. This information is important both for work producers who have the opportunity to immediately respond to the shortcomings of concreting, and for designers who make timely adjustments to the calculation. Bored reinforced concrete piles with a diameter of ~ 800 mm were selected as an object of the study. The subject of the study is a seismo-acoustic (echo–pulse) method of monitoring reinforced concrete bored piles, inter-well ultrasonic monitoring. The purpose of the work: is to study the uniformity of the structure of bored piles; to determine the actual length of piles; to identify pile defects, to assess the compressive strength of concrete by ultrasonic pulse method.

When constructing offshore pipelines, the concreting of pipes is used as a protective and weighting structure. The requirements for concrete water absorption are set only to ensure the corrosion resistance of concrete. When determining the design characteristics of the structures described above, it is not taken into account that the water-saturated concrete has an increased ballasting capacity, which makes it possible to ensure the stability of the design spatial position of the main gas
pipeline of underwater crossings for the entire period of operation of the gas pipeline. Determining the actual water absorption of concrete under pressure can reduce the volume of concrete used, as well as reduce the cost of ballasting while ensuring the stable position of the pipeline. This article describes a new developed technique for determination of the water absorption of concrete under water pressure based on the UVF-6/09 unit. The obtained experimental data of the water absorption of concrete at various values of water pressure are shown. An analysis of the results of experimental work is given.

The methods of designing frost-resistant and high-frost-resistant concretes and technologies of concrete works used in the construction of port facilities on Sakhalin Island are given. Justifications for improving the design methods and technology of concrete works, taking into account the actual work of concrete construction, are presented. The analysis of the construction of port facilities on Sakhalin Island using traditional and modern technology of concrete works, revealed the advantages and disadvantages of traditional and modern technologies of concrete works. It is shown that on the basis of the principles of traditional technology of concrete works, it is possible to obtain high-resistance concretes for the structures of port facilities in conditions of frost exposure. The principles of modern technology, based on the use of additive-modifiers in concrete to improve the technological properties of the concrete mixture and improve the qualitative indicators of concrete, make it possible to increase frost resistance by two orders of magnitude. It is established that the observed destruction of concrete after the first winter season is associated with technological miscalculations that do not take into account the actual work of concrete in the structure. A comparative analysis of various concrete technologies, working conditions and its quality indicators in structures make it possible to establish the defining qualitative indicators of external influences and concrete, which it is advisable to take as a basis for improving concrete technology and formulating the concept of a concrete durability model in conditions of frost exposure.

Research and development work (R&D), the main task of which was to assess the punching strength of flat floor slabs of monolithic reinforced concrete in the areas of support on the ends of the walls, was carried out at NIIZHB named after A. A. Gvozdev. As part of the study, experimental, as well as computational and theoretical studies were carried out on the issue of determining the strength of fragments of flat slabs for punching in the zones of the ends of the walls. On the basis of the research results obtained and their analysis, it was found that there is an influence of bending moments in the plane of the walls on the punching strength of the plate, which requires appropriate consideration in the calculation methods.

The main construction and technical properties and specific advantages of monolithic foam concrete, making it possible to use it in emergency braking systems installed on the runways of airfields are analyzed. Monolithic foam concrete of D200-D500 density grades with a pore volume of 65-85 % have been developed. It is shown that such important physical and technical properties of concrete as average density, thermal conductivity, strength and frost resistance depend on the quality indicators of the macroporous structure of foam concrete and the structure of interpore partitions (membranes). A decrease in the strength of foam concrete was found as the porosity dispersion increased. It is shown that an increase in the water-solid ratio leads to a significant improvement in the pore distribution.