Browsing by Author "Ananova, Oxana"

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Citation - WoS: 6
Citation - Scopus: 7
Modeling and Calculation of Improved Centrifuged Reinforced Concrete Columns With Variotropic Structure
(MDPI, 2023) Stel'makh, Sergey A.; Shcherban', Evgenii M.; Beskopylny, Alexey N.; Mailyan, Levon R.; Veremeenko, Andrey; Shilov, Aleksandr V.; Ananova, Oxana; Aksoylu, Ceyhun
The use of vibro-centrifugation technology allows the manufacture of variotropic structures that are inhomogeneous in the annular section and have different characteristics along the section thickness. Hardening of the outer layers allows the structure to better resist bending conditions, however, the behavior of the variotropic column under central and eccentric compression remains unexplored. This article considers the problem of compression of hollow columns made of homogeneous concrete that is non-uniform in the annular section (variotropic), and is reinforced with steel reinforcing bars at different values of the load application eccentricity. Variotropic concrete obtained by vibro-centrifugation technology has a stronger outer part and a less durable inner part. The strength of a homogeneous column corresponds to the strength of the middle part of variotropic concrete. The problem was solved numerically in the ANSYS environment for a vertical column rigidly clamped at the bottom edge and loaded with eccentricity at the top edge. Three types of eccentricity are considered; e/r = 0, 0.16 and 0.32 (respectively 0 mm, 0.24 mm and 48 mm). The results of the solution in the form of stress fields, deformations and a pattern of crack development in a spatial setting are obtained. The results showed that for central compression, a homogeneous column has a better bearing capacity of 3.6% than a variotropic one. With the values of eccentricity e/r = 0.16 and 0.32, the variotropic column has a higher bearing capacity (by 5.5% and 6.2%) than the homogeneous one and better resists the development of cracks. The significance of the study lies in the practical application of the proposed approach, developed on a research basis, for non-trivial and complicated operating conditions of columns. This study influences the development of reinforced concrete structures and applies scientific findings to engineering practice.
Citation - WoS: 4
Citation - Scopus: 3
Performance Assessment of a Novel Green Concrete Using Coffee Grounds Biochar Waste
(Mdpi, 2024) Beskopylny, Alexey N.; Stel'makh, Sergey A.; Shcherban', Evgenii M.; Ananova, Oxana; Chernil'nik, Andrei; El'shaeva, Diana; Pogrebnyak, Anastasia
An actual scientific problem in current concrete science is poor knowledge of the problem of modifying concrete with plant waste. At the same time, plant waste benefits from other types of waste because it is a recycled raw material. A promising technological approach to modifying concrete with plant waste is the introduction of components based on the processing of coffee production waste into concrete. This study aims to investigate the use of biochar additives from spent coffee grounds (biochar spent coffee grounds-BSCG) in the technology of cement composites and to identify rational formulations. A biochar-modifying additive was produced from waste coffee grounds by heat treatment of these wastes and additional mechanical grinding after pyrolysis. The phase composition of the manufactured BSCG additive was determined, which is characterized by the presence of phases such as quartz, cristobalite, and amorphous carbon. The results showed that the use of BSCG increases the water demand for cement pastes and reduces the cone slump of concrete mixtures. Rational dosages of BSCG have been determined to improve the properties of cement pastes and concrete. As a result of the tests, it was determined that the ideal situation is for the BSCG ratio to be at a maximum of 8% in the concrete and not to exceed this rate. For cement pastes, the most effective BSCG content was 3% for concrete (3%-4%). The compressive and flexural strengths of the cement pastes were 6.06% and 6.32%, respectively. Concrete's compressive strength increased by 5.85%, and water absorption decreased by 6.58%. The obtained results prove the feasibility of using BSCG in cement composite technology to reduce cement consumption and solve the environmental problem of recycling plant waste.