Browsing by Author "Netesa, Nikolay I."

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    Determining the Rational Compositions of Low-Strength Concretes
    (НВП ПП «Технологічний Центр», Харків, 2019) Shishkin, Alexsander; Netesa, Nikolay I.; Netesa, Andrii M.
    ENG: The paper reports regularities in the influence of the amount of waste from iron ore enrichment at a rational composition of grain components on strength of concretes with a minimal cement consumption. Low-strength concretes are used in the non-reinforced structures, so they are not subject to the requirement for the minimal cement consumption in order to ensure the protection of reinforcement against corrosion. A significant reduction in cement consumption by low-strength concretes while maintaining the required strength can be ensured by a rational grain composition of the components of a concrete mixture, which is characterized by the ratio between large, medium, and small components of 52:23:25. In such formulations, the required amount of fine-grained component is achieved by introducing the fine-grained components, made, for example, from the secondary products of industry, specifically the iron ore dressing waste. The result of the research conducted established that ensuring the rational grain composition of the concrete mixture components provides for the required low strength of concrete at a significantly less cement consumption than that for concretes whose composition is defined in line with other procedures. It was found that it is advisable to use the iron ore dressing waste as a fine-grained supplement, the introduction of which at rational amount ensures significant improvement in the efficiency of cement utilization in concretes of low strength. Application of concretes of the proposed formulations, which could be used for temporary structures ‒ a concrete cap for making floor slabs at formwork-free molding, could save a significant amount of cement, and dispose of the secondary products from industry. The research has also established that the use of plasticizers makes it possible to obtain concretes of the rational grain composition with the required workability.
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    Effect of the Iron-Containing Filler on the Strength of Concrete
    (НВП ПП «Технологічний Центр», Харків, 2017) Shishkin, Alexsander; Netesa, Nikolay I.; Scherba, Vladimir
    EN: The purpose of present research is to determine the impact of a mixture of river and technogenic sand containing iron compounds in the presence of plasticizers on the strength of fine-grained concretes. As a result of the performed research it was established that the technogenic sand, representing mineral complexes containing iron compounds, interacts with Portland cement minerals and the products of their hydration. The studies we conducted showed the possibility of targeted regulation of the processes of formation of structure of finegrained concretes by joint application of mineral complex with iron ions, river sand and surface-active substances that are substantially different in the structure of molecules. It was established that using a mixture of river and technogenic sand containing iron compounds in the form of a fine aggregate leads to a significant increase in concrete strength. There is a certain ratio between river sand and the technogenic sand containing iron compounds, which provides concrete with the largest strength. An optimal content of the technogenic sand in a fine aggregate depends on the type and amount of minerals within its structure, and the content of particles with different size. It is demonstrated that the effectiveness of using modern superplasticizers in fine-grained concretes increases considerably with the introduction of mineral complexes containing ions of iron to the compositions of concrete.
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    Problems of Development of an Underground Transport Infrastructure of Cities
    (The Silesian University of Technology, Faculty of Transport. Katowice, Poland, 2020) Pshynko, Oleksandr M.; Radkevych, Anatolii V.; Netesa, Nikolay I.; Netesa, Andrii M.
    ENG: Summary. The goal of this article is to determine rational constructional and technological options for the development of underground space, in particular, the arrangement of underground parking lots under the specific hydrogeological conditions of Dnipro city. In this article, the best practices in the construction of similar facilities in the world are discussed. Arrangements for individual structural elements and structures as a whole were considered. The main resources for their implementation are determined, the most important performance indicators are calculated, their comparison is carried out and proposals for the use of individual technological concepts are developed. The experience of underground space development in Dnipro city is studied and the problems of construction of underground structures under specific difficult hydrogeological conditions are identified. The proposed technological concepts make it possible to implement such design solutions under difficult hydrogeological conditions with dense development and preservation of historical buildings in the city.
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    Rational Compounds of Low-Strength Concrete with Improved Coefficient of Efficiency of Cement Use
    (Trans Tech Publications LTD, Switzerland, 2019) Netesa, Andrii M.; Netesa, Nikolay I.; Radkevych, Anatolii V.; Yakovliev, Serhii O.
    ENG: Abstract. The purpose of the research findings, given in article, is aimed to determine the rational compounds of concrete with an average cubic compressive strength less than 20 MPa with minimum required expenditures of cement. To reach the goal, mathematical planning of the experiment was used with variability of cement consumption from 90 to 190 kg / m3 in the compositions of the concrete mixture, and for the fine-grained filler from tails of processed ores, the consumption was like at 100 to 400 kg / m3. The result of processing experiments has shown us the dependences of the change in strength and coefficient of efficiency of the use of cement of the factors involved. Optimized values increase most intensively with minimum cement consumption and a change in the consumption of fine filler within the limits of the study. The highest coefficient of efficiency of use of cement is expressed by the ratio of the achieved strength per unit mass of used cement in the concrete mix and it was obtained at a cement consumption of 90 kg / m3 and a filler of 400 kg / m3. Using the obtained dependences of optimized values on the factors under study, the composition of concrete may be predicted with a strength up to 20 MPa with the required amount of filler.