Архив

Functionalization of one-component cement silicate paint

https://doi.org/10.58224/2618-7183-2024-7-5-5
Аннотация
The paper presents the results of a study devoted to expanding the functional properties of one-component cement-silicate paints based on white Portland cement, soluble sodium glass and a hardening retarder (sodium phosphate). Existing compositions, despite their exceptional performance qualities, are not able to provide the entire range of required functional characteristics. Therefore, in order to expand the areas of cement silicate paints application, additives based on aluminum powder and nano-sized titanium dioxide were introduced into the coating composition. This resulted in the increase in the electrical conductivity of the coating and made the paint self-cleaning due to photocatalysis.
The study showed that the introduction of nano-sized titanium dioxide particles into the paint composition provides the rapid degradation of organic pigments (within 2 days) due to the photocatalysis reaction occurring under the influence of ultraviolet solar radiation. The pigments are further removed due to precipitation. This helps to maintain the aesthetic properties of the paint even in high dust conditions, for example, in conditions of sandstorms, which are frequent in the African climate.
The introduction of aluminum powder into the paint composition reduces its electrical resistance (in a wet state) from 5.05 kOhm for the reference sample to 2.7 kOhm for the modified sample. The thickness of the applied paint was 350 microns. This can help the coating to absorb man-made electromagnetic radiation due to shielding, while preventing the accumulation of static electricity on the surface, which also contributes to less dust in the premises. In addition, the use of aluminum powder instead of traditional electrically conductive carbon-containing additives allows maintaining the aesthetically pleasant white color of the paint.
PDF

Study of the concordance between various concrete deformation models and experimental data for uniaxial compression cases

https://doi.org/10.58224/2618-7183-2024-7-5-6
Аннотация
There are various equations describing concrete stress-strain curves, each yielding different theoretical curves. An important scientific question is achieving the best correspondence to experimental data. The Geniyev theory inherently includes equations for three components of stress and strain. In contrast, the Eurocode and the Russian Building Code equations are provided for uniaxial stress conditions. This paper presents a comparison of theoretical curves for uniaxial compression based on Eurocode equations, the Russian Building Code, and Geniyev theory with experimental results from tests on prism and cube samples. The analysis includes deviations of the maximum stress points of theoretical curves from the corresponding experimental data. Numerical analysis is provided for both stresses and strains. A distinguishing feature of this work compared to existing research on Geniyev theory equations is that they are presented in a resolute form, incorporating three parameters: concrete compressive strength, tensile strength, and the initial modulus of elasticity.
The importance of using secondary resources on the basis of industrial waste is understood by both governments of developed countries and business (production of Portland cement using ground metallurgical slag as a mineral additive at Novotroitsk, Magnitogorsk, Sterlitamak, Katav-Ivanovsk and other plants in the South Urals). The use of secondary raw materials requires the creation of technological infrastructure for processing of secondary raw materials, the costs of which can be quickly recouped due to the cheapness and availability of industrial secondary raw materials and freeing the territory from environmental pollution. In order to recoup the costs of the infrastructure, it is necessary to guarantee full compliance of the quality of pavement elements with the requirements of GOST R 59120-2021. Secondary raw materials have a great variety and laboratory analysis of the quality of pavement elements is required in order to design compositions with the best quality, satisfying all regulatory requirements. In our work the authors present the results of laboratory research and evaluation of the possibility of using clinker-free lime-slag binder based on the mineral product of soda production and metallurgical slags to strengthen and stabilize soils for their use in pavement structures in the construction of roads for various purposes and climatic zones.
It is experimentally shown that the addition of lime-slag binder in the amount of 8-10% of the dry weight of both cohesive (loamy soil, loamy sand) and non-cohesive (fine sand) soil allows to obtain reinforced soil with improved strength and elastic-deformative characteristics, which can be used instead of scarce natural crushed stone and gravel in the construction of underlying layers of pavements in the construction and reconstruction of highways. This technology can be used not only in the Russian Federation, but also in a number of other countries, including those with hot dry climates (e.g., the Republic of Egypt).
PDF

Effect of powder morphology on the structure and properties of Al2O3 based coatings obtained by detonation spraying

https://doi.org/10.58224/2618-7183-2024-7-5-7
Аннотация
Aluminum oxide (Al2O3) remains a crucial material in the field of engineering ceramics, particularly in industrial applications. Notably, its transitional phases, in addition to the α-phase, demonstrate good properties. In this article the structure and properties of coatings obtained by detonation spraying from aluminum oxide powder with different production methods (fragmentation and spherical particle shape) and crystalline modification (α-Al2O3 and γ-Al2O3) but with similar average particle size were studied. The goal of the study was to investigate the influence of the morphology and phase composition of the powder on such properties of the coatings as microstructure, porosity, roughness and hardness. The results of the study showed that agglomerated spherical powder leads to low porosity of the coatings, while crushed fragmentation particles provide dense layers. In addition, the coating obtained using fragmentation powder showed higher hardness, and the surface had twice the roughness, compared to the coating applied using spheroidal powder. These results confirm the effect of the morphology of the original powder on the final properties and efficiency of the coatings. The study showed that the detonation spraying method allows for the efficient application of coatings from two types of Al2O3 powders with different morphology (spherical and fragmentation) and phase composition (γ-Al2O3 and α-Al2O3) but with similar particle sizes.
PDF

Technical feasibility factors affecting urban environmental sustainability in decision-making: Erbil-Iraq

https://doi.org/10.58224/2618-7183-2024-7-5-8
Аннотация
This paper introduce decision-making model of sustainable urban development in Erbil city in Iraq. The decision-making model will includes higher-level policy orientation, grass-roots environmental protection, economic feasibility, and environmental pressure. The quantitative analyze of urban environmental sustainable development decision-making in prefecture-level. The data analysis collected from the annual government work report using seven specific factor, which set up according to the theoretical model framework. The results show that the driving force of sustainable development is mainly from top to bottom, the macro strategy of the central government and other upper-level governments is the core factor of sustainable transformation, and the demand for sustainable development of the grassroots people needs to continue to increase. In addition, prominent environmental issues have attracted the attention and actions of local governments, but urban governments still regard sustainable development as a distributive policy to a large extent, and the awareness or conditions for seeking economic welfare through environmental governance have not yet achieved.
PDF

Technical aesthetics of stained glass panels for the modern architectural paradigm of Southern Russia

https://doi.org/10.58224/2618-7183-2024-7-5-9
Аннотация
The construction sector consumes more than half of the energy generated in Russia. Therefore, practical application of energy-efficient and aesthetic construction products is highly required. The article aims at looking into the way to enhance characteristics of the double-glazed window, which is an energy-saving product in a building that regulates the amount of light energy indoors and affects the amount of heat loss in winter. Until now, this function has been the main one for double-glazed windows. Secondary, but no less important, is the aesthetic appearance of the double-glazed window. The study is based on the experimental data obtained through the ramp-hold programme according to COE 96 as well as through the comprehensive analysis of six glass types manufactured by Oceanside Glass & Tile®. As a result, the study discusses characteristics of stained glass that can be used for Tiffany technique inserts in a window opening. Such stained glass panels throughout the entire historical path have demonstrated sublime beauty and lightness, both indoors and outdoors. Modern technologies allow us to take the art of stained glass and its adaptation in modern double-glazed windows to a new level. Finally, special attention is paid to the aesthetics of stained glass panels for the modern architectural paradigm of Southern Russia.
PDF

Assessment of the influence of building parameters on the urban heat island in the districts of Moscow

https://doi.org/10.58224/2618-7183-2024-7-5-10
Аннотация
Large cities, as financial centres, attract a dense adult population, leading to a high demand for housing. This growth requires urban expansion and increased building density, which disrupts the ecosystem and gives rise to a concentrated urban heat island (UHI). In a study conducted in Moscow, a numerical climate simulation model was used to explore the relationship between urban indices, specifically the building height-to-width ratio (H/W), sky view factor (SVF), and UHI intensity. The results indicated significant impacts of both H/W and SVF on UHI. More accurate predictions were achieved by adjusting coefficients in the Oke model using non-linear regression of simulated H/W and heat island intensity. These findings highlight the crucial role of urban morphology in UHI formation and development, providing a scientific basis for mitigating UHI impacts through urban planning strategies. While it is challenging to generalise a formula for calculating UHI intensity due to the diversity of urban forms, our research method offers a valuable approach for similar studies in other cities.
PDF

Improving the procedure for interaction between participants in the construction control system in order to increase labor productivity

https://doi.org/10.58224/2618-7183-2024-7-4-1
Аннотация
In connection with the current demand for reducing the implementation of investment and construction projects, there is a need to determine the risks that affect the duration.
Within the framework of building and construction works, there is a risk of various destabilizing factors arising, leading to economic losses and increased construction period, and consequently a decrease in labor productivity.
Existing administrative barriers, maintaining and coordinating a large amount of executive documentation leads to high costs of various resources. In this regard, the work optimized the functioning of the construction control system.
The study identified factors that influence the functioning of the construction control system. A rational procedure for carrying out construction control of capital construction projects has been determined.
The study used such methods as: the method of expert assessments, statistical data analysis, and the Varimax rotation method.
The results of the study were introduced into the activities of the organization performing the functions of a developer at the stage of construction of objects.
As a result, a method of interaction between participants in the construction control system has been formed, which allows increasing labor productivity.
PDF

Study of thermophysical characteristics of variatropic concretes

https://doi.org/10.58224/2618-7183-2024-7-4-2
Аннотация
An important task in the development of the construction industry is to find rational technologies, materials and solutions that ensure energy efficiency in construction and create conditions for obtaining energy-saving products and structures for various construction projects. At the same time, the issue of structures made of the same material, but having a difference in their properties and characteristics in thickness, the so-called variatropic building material, which, due to differences in structure and properties, ensures variatropic properties of the building structure itself, has been poorly studied. The goal of this study was to eliminate a significant scientific deficit, consisting in the absence of a systematized knowledge base on the structure and thermophysical properties of variatropic products and structures made of concrete or reinforced concrete. The modeling was performed in the ANSYS environment (Ansys version 2024 R1). An element selected for modeling was a ring-section heavy concrete pillar with an outer diameter of 450 mm and an inner diameter of 150 mm. Variatropy was specified by conventionally dividing the element’s cross-section into several layers with different physical and mechanical properties: three for centrifuged concrete and four for vibrocentrifuged concrete. In the course of modeling, the authors determined the main initial data for the calculations, and based on the results of the calculations, dependencies were established confirming the improvement of the concrete’s heat-insulating properties due to the use of centrifugal compaction technology. The phenomenon of variatropy leads to an increase in heat-transfer resistance – from 13% for centrifuged concrete to 23% for vibrocentrifuged concrete in comparison with vibrated concrete. At the same time, vibrocentrifuged concrete turned out to be 8% more efficient than centrifuged concrete in terms of “heat-transfer resistance”. The conducted modeling shows that variatropic concrete is promising for further research and practical application in terms of its thermophysical characteristics.
PDF

Specific heat dissipation of concrete and the risk of early cracking of massive reinforced concrete foundation slabs

https://doi.org/10.58224/2618-7183-2024-7-4-3
Аннотация
Introduction. The modeling of temperature fields and stresses used to prevent the risk of early cracking of massive monolithic reinforced concrete structures determines the relevance of improving the algorithm for calculating temperature stresses due to the «center-top» temperature difference depending on the magnitude and kinetics of heat dissipation of concrete, autogenous shrinkage, heat transfer conditions and ambient temperature. Purpose of the study: modeling of temperature fields and stresses of massive structures using the example of a flat foundation slab 1.5 m thick based on the proposed dependencies of the kinetics of strength, heat dissipation, autogenous shrinkage, and deformation properties of concrete of various classes. Methods. Modeling of temperature fields and stresses taking into account specific heat dissipation and properties of concrete. Results: A system of equations is proposed, identical in structure to the strength kinetics equation according to EN 1992-1-1, to describe the kinetics of autogenous shrinkage and heat dissipation of hardening concrete depending on the type of cement according to the hardening kinetics. Modeling of the formation of temperature fields and stresses of a massive flat foundation slab 1.5 m thick was carried out depending on the class of quick-hardening concrete and the specific heat dissipation of cement. It is substantiated that it is insufficient to prevent early cracking by limiting only the «center-top» temperature difference without taking into account the specific properties of concrete. It has been shown that autogenous shrinkage, when dependent on the strength of concrete according to the EN 1992-1-1 equation, can slightly reduce the level of tensile stresses in the early period of concrete hardening of a massive foundation slab. An approach to normalizing the heat dissipation of concrete and cement is proposed in order to limit the stress level under the conditions of the problem considered. The values of the permissible values of the «center-top» temperature difference taking into account the properties of concrete were obtained.
PDF

The production technology of high-performance ceramic stones based on the products of processing of coal dumps

https://doi.org/10.58224/2618-7183-2024-7-4-4
Аннотация
The aim of the research was to study the main properties of coal dumps processing products, their impact on the quality of finished products and the development of a technology for manufacturing process of ceramic stones with high efficiency. Structural features and chemical-mineralogical composition of coal dumps processing products have been studied, their pre-fired and firing ceramic properties have been studied. The raw mass compositions were chosen based on this, along with testing of laboratory samples. The impact of different technological factors on the properties of the final products has been identified and established. The material composition and technological properties of fine, fine and medium fraction materials are shown. A basic classification of the products derived from processing of waste heaps has been conducted based on grain composition, coal component content, and mineralogical and petrographic characteristics. The optimal formulations for raw material mixtures and the manufacturing process for producing large ceramic bricks with an average density below 800 kg/m3 are described. The impact of grinding degree of the waste heap processing products and the firing temperature on the strength of the samples have been established. The incorporation of finely dispersed products from waste heap processing decreases the density and strength of the samples. It is suggested to use semi-rigid extrusion technology for molding these products. Utilizing processed coal waste materials in wall ceramics production will aid in their disposal and enhance the environmental conditions in the area. This research was conducted in Russia at Don State Technical University in Rostov-on-Don. In creating a technology for producing ceramic blocks from screenings of waste heap processing in Eastern Donbass, minimal production costs and high profitability of production are envisaged.
PDF