At present, the load-bearing enclosing structures of buildings and structures are designed and built considering the increasing requirements for energy efficiency and energy saving of such structures. This is due to the need for a thrifty attitude to the energy consumed and the need to strive for the greening of construction and increase the energy efficiency of buildings and structures. In this regard, one of the most effective and proven building materials is cellular concrete. The purpose of this study was to study the influence of some prescription factors on the structure formation and properties of non-autoclaved aerated concrete with improved characteristics. Standard test methods were used, as well as SEM analysis of the structure of aerated concrete. Non-autoclaved aerated concrete with the replacement of part of the cement with microsilica in an amount from 4% to 16% MS showed higher strength characteristics compared to aerated concrete, where part of the cement was replaced by the addition of granulated blast-furnace slag and a complex additive. The maximum value of compressive strength was recorded for aerated concrete with 16% MS addition. The largest increase in the coefficients of constructive quality was observed in compositions of aerated concrete with the addition of silica fume from 11% to 46% compared with the control composition. The addition of microsilica makes it possible to achieve an improvement in the thermal conductivity characteristics of non-autoclaved aerated concrete (up to 10%). Replacing part of the cement with slag and complex additives does not have a significant effect on thermal conductivity. The obtained dependencies were confirmed by the analysis of the structure formation of the studied aerated concrete at the micro level. An improvement in the microstructure of aerated concrete with the addition of microsilica in comparison with samples of the control composition has been proven.

The utilization of aquaculture waste, such as snail shells, is a severe issue. These shells are common in water-sources and are a by-product of sifting sand for masonry and concrete work. Calcium-rich river shells are of great interest for cement building materials. In this regard, the purpose of this article was to develop a nanomodified concrete with improved characteristics based on the powder of snail shells. Experimental studies have confirmed the effectiveness of the use of river shells in concrete without a decrease in strength characteristics and deterioration of other properties. It has been found that the optimal replacement by the snail shell powder that replaced cement is in the amount of 6%. By the nanomodification of concrete with the powdered shells of river snails, it was possible to achieve an increase in compressive strength up to 12%, axial compressive strength—up to 8%, tensile strength in bending—up to 9%, axial tensile strength—up to 11%, elastic modulus—up to 8%. Concrete nanomodification with snail shell powder in the amount of 6% contributed to a reduction of deformations of up to 7%. The study of the microstructure of concrete samples nanomodified with snail shell powder confirmed the obtained dependences of the cement’s properties on the nanomodifier dosage, as well as the most effective dosage of snail shell powder.

Fundamental knowledge of the processes of cement gel formation for new generation concretes is a scientific deficit. Studies aimed at the formation of a cement gel for standard vibrated concrete research, and especially for centrifugally compacted concrete, are of interest because the structure of this concrete differs significantly from the structure of standard vibrated concrete. This article aims to study the fundamental dependencies of the theoretical and practical values that occur during compaction using vibration, as well as the centrifugal force of new emerging concrete structures. New theoretical findings about the processes of cement gel formation for three technologies were developed: vibrating, centrifuging, and vibrocentrifuging of concrete; the fundamental difference in gel formation has been determined, the main physical and chemical processes were described, and a significant effect of technology on the gel formation process was established. The influence of indirect characteristics based on the processes of cement gel formation, rheological properties of concrete mixtures, water squeezing processes, and the ratio between the liquid and solid phases in the mixture was evaluated. The process of formation of cement gel for centrifugally compacted cement systems was studied and graphical dependences were constructed, giving answers to the mechanism of interaction according to the principle “composition-rheological characteristics-structure-properties of concrete”. The quantitative aspect of the achieved result is expressed in the increase in the indicators demonstrated by centrifuged and especially vibrocentrifuged samples compared to vibrated ones. Additionally, in terms of strength indicators, vibrocentrifuged samples demonstrated an increase from 22% to 32%, depending on the type of strength, and the rheological characteristics of concrete mixes differed by 80% and 300% in terms of delamination.

Introduction. In recent years many researchers have become interested in applying the various types of finite element method to studying of the buildings oscillation problems. In recent decades the finite element method is being successfully used for natural oscillations analysis along with the physical modeling. The scaled physical modeling and experimental approaches are also suitable for solving the complex problems. The main aim of our research is to identify the dependence of dynamic characteristics of a building frame on geometric characteristics of the frame elements. The objective of this research is to make an analysis and overview of the topic, to determine the scientific deficit, to conduct numerical and experimental studies, to formulate conclusions, to model and analyse the results. The scientific novelty consists in the possibility to use the obtained data on building frame natural oscillations depending on the geometric characteristics of the frame elements as an optimal rigidness ratio. The practical significance of the research consists in development of specific analytical relations for choosing a building frame design solution with an optimal natural frequencies parameter to be used in design and construction practice.Materials and methods. The creation and calculation of the finite element model was carried out in the LIRA software package.Results. As a result of calculation the frequencies and periods of building frame natural oscillations were obtained.Discussion and conclusions. Based on the results of the building natural oscillations analysis the conclusion was made that by changing the frame elements rigidity it’s possible to select its dynamic characteristics to find the optimal design solution of structures.

Introduction. Concrete is one of the materials most frequently used in construction thus the technologies of its manufacturing are being constantly improved. In our article we will develop the laboratory-made compositions of concrete based on the certain raw materials resources and restrictions existing at the construction site of one of the nuclear power plants in the Republic of Türkiye. One of the results of elaborating the concrete composition design technology is the selfcompacting concrete that fosters sustainable construction due to significant reduction of energy consumption. Self–compacting concrete is a type of concrete that can completely fill in the formwork only by gravity, without need for concrete consolidating by vibration. Its high fluidity and filling capacity are its advantages over conventional concrete. Self-compacting concrete has high fluidity, high water retention capacity, good strength. The aim of the study was to obtain the laboratory-made compositions of concrete based on the certain raw materials resources and restrictions existing at the construction site.Materials and methods. The list of raw materials potentially meeting the design documentation requirements has been specified. The concrete compositions using various aggregates were selected, the minimum amount of cement was determined, aimed among other things at corrosion resistance improvement.Results. Based on the restrictions existing at the construction site and according to the results of raw materials analysis including their oxide composition specification, 5 compositions were developed for each of NPP engineering structures.Discussion and conclusions. The study has completed all the tasks set forth, the main of which are: analysis of the raw materials market, laboratory studies of raw materials, specification of their actual physical and mechanical properties, identification of components meeting the standards and requirements, obtaining the laboratory-made compositions of concrete mixtures classified by their designation. The perspectives for further research are indicated.