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Kinetics of contact formation between dissimilar crystalline materials during the period of active strain of the first stage of a solid-phase topochemical reaction

https://doi.org/10.58224/2618-7183-2025-8-6-7
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Abstract
One of the key processes that largely determines the quality of a permanent precision joint formed in the solid state under pressure and heat, which belongs to the class of solid-state topochemical reactions and proceeds in three main stages, is the formation of actual contact, which transitions to a state of physical contact (stage one) at a certain ratio of the level of thermal strain and the contact area. The latter is formed due to plastic strain and the shape change of microprotrusions on the surfaces being joined, which alters the mechanical properties of the resulting contact pads and the near-contact volume of the metal microprotrusions. To develop valid process parameters for producing a high-quality joint, it is important to establish the influence of temperature, pressure, and the height of microroughness of the contacting surfaces of the materials being joined on the kinetics of individual stages of the solid-state topochemical reaction under thermal strain. This paper presents the kinetic dependencies of contact formation during the period of active strain or active loading between dissimilar crystalline materials using the example of synthetic single-crystal corundum – MB copper (oxygen-free) and provides their physical and mathematical justification. Knowledge of the kinetic laws governing the formation of actual contact and the transition to physical contact at a certain ratio of the level of thermal strain action and stress state (the ratio of normal and tangential microstresses of the 2nd kind on the surface of contact pads and in the volume of microprotrusions) and the occurring mechano-physical-chemical processes on the surface of the forming contact pads and in the volume of microprotrusions, allows for a more rational consideration, construction and implementation of the technological process for obtaining a precision detachable (contact of the traction sheave with the cable) or permanent connection of materials in a wide variety of combinations, including those with different nature of chemical bonds and resistance to plastic strain, and will also allow for the consideration and assessment of the role of microstresses of the 2nd kind in the occurrence and propagation of microcracks in the grain of the metal and the provision of recommendations for the prevention of sudden brittle failure of welded building metal structures.
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Environmental safety management of city life cycle through low-carbon principles

https://doi.org/10.58224/2618-7183-2025-8-6-8
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Abstract
The contemporary urban environment, being a complex system saturated with construction objects interconnected by engineering and social communications, contains numerous potential sources of hazardous technosphere situations. Preventing and mitigating their consequences becomes feasible only through timely automated monitoring of early warning signs and forecasting dynamics of development. At the same time, construction objects within the urban context consume significant material and energy resources, contributing to increased carbon emissions impacting the environment. Therefore, there is a pressing need for digital instruments capable of managing these processes across their entire lifecycle. In this regard, effective means of ensuring ecological safety in cities involves monitoring technical, organizational, and functional components of works conducted and planned for both construction and maintenance phases of urban infrastructure. Based on these measures, maintaining the carbon sustainability of urban immovable property and infrastructure funds becomes achievable when implemented within an adaptable City Information Model (CIM) tailored specifically for managerial tasks. The scientific novelty of the proposed research lies in developing scientific-methodological foundations for digital monitoring of current conditions and predicting the evolution of carbon state and resilience of constructed and operational urban objects and infrastructure integrated into a unified CIM. This approach serves as the basis for instrumentation aimed at managing ecological safety of construction objects. In the research, the technology of information modeling of city objects is constructed based on the author's factor space, incorporating monitoring and forecasting of conditions for realization and assessment of carbon sustainability of constructed and operated objects. This effort utilizes international databases regarding the carbon impact of construction materials and processes, along with analytical data derived from project estimates documentation of urban objects. Automated expert activity tools, including the integration of unmanned aviation systems, are utilized extensively. Algorithms for automated evaluation and forecasting of City carbon impact Indicator (CCII) are presented and to be used as a basepoint for unmanned city carbon analysis within city life cycle management. These algorithms aim to optimize recommended construction, restoration, or operational measures by leveraging results from drone surveillance, neural network detection, mapping, quantitative assessments, and dynamic parameter changes of objects. Ultimately, this allows for synthesizing optimal management decisions ensuring environmentally safe urban spaces towards the carbon homeostasis as an ultimate goal for modern city ecological management.
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Experimental analysis of a new high-tech method of strengthening reinforced concrete structures based on the use of metal and CFRP materials

https://doi.org/10.58224/2618-7183-2025-8-6-9
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Abstract
This paper presents a large-scale experimental analysis of a new high-tech method for strengthening reinforced concrete columns using metal and CFRP materials. The research is justified by evaluating existing traditional and modern methods of strengthening reinforced concrete compressed elements, identifying their main drawbacks, and taking these into account, a new strengthening method was developed. To study the large-scale effect of the new high-tech metal and composite-based strengthening method, two groups of a total of 46 reinforced concrete column samples with different flexibilities were designed and tested for central and eccentric compression until failure. The main test parameters included column flexibility, load application eccentricity, internal and external metal reinforcement, spacing, and cross-sectional area of composite strengthening. The study investigated the influence of the above-mentioned variable factors on the failure pattern, ultimate strength, peak stress, and deformation characteristics of columns strengthened with carbon fiber composite materials (CFRP). The results showed that reinforced concrete columns strengthened with CFRP, having the same dimensions and tested under the same load application eccentricities, demonstrated different increases in ultimate strength compared to unstrengthened columns. Peak stress increased with an increase in the cross-sectional area of metal reinforcement and decreased with an increase in the distance between composite stirrups. Ultimate axial strains of strengthened samples increased with a decrease in the distance between composite stirrups. The difference in the cross-sectional area of composite strengthening did not have a significant impact on the load-bearing capacity and ultimate strains of reinforced concrete strengthened structures.
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Variatropic concrete compressive strength prediction under freeze-thaw conditions using machine learning methods

https://doi.org/10.58224/2618-7183-2025-8-6-10
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Abstract
The introduction of intelligent models, in particular using machine learning methods, opens up prospects for the development of the construction industry. The construction of regression models for predicting the physical and mechanical properties of various types of building materials is a promising and relevant area. The use of such models makes it possible to take into account complex and multifactorial dependencies, while minimizing the influence of the human factor. In the present study, variatropic concrete B30, obtained by centrifugation, acts as the test material. The dataset (351 objects) was assembled during laboratory studies to study the effect of freeze-thaw cycles on the strength characteristics of the material. Using the computer vision method based on the convolutional neural network U-Net, the damage on each of the concrete layers was assessed on different cycles. 4 machine learning models for predicting compressive strength were trained and tested on the collected dataset: Ridge Regression (RR), Random Forest (RF), CatBoost (CB) and Multi-layer Perceptron (MLP). The hyperparameters of the models were optimized using Grid Search + 3-fold cross-validation. As a result of testing the algorithms on a test sample, the best quality metrics were demonstrated by tree architectures: MAE for RF and CB 0.09 and 0.17 MPa, respectively, R2 = 0.99. The results are supplemented by SHAP analysis. The results obtained are a useful tool for optimizing the composition of variatropic concretes used under aggressive conditions.
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Plasma electrolyte discharge in metal powder production processes

https://doi.org/10.58224/2618-7183-2025-8-6-11
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Abstract
Zinc ultrafine powder has found applications in the medical, electronic, chemical, construction, and metallurgical industries. Existing methods of producing zinc powder have a number of drawbacks: some of them are highly energy-consuming, while others are characterized by low productivity and a coarse-grained structure of the powders. A solution to this problem can be found in the use of a gas discharge between an electrolytic anode and a metallic cathode immersed in an alkaline solution.The aim of this work was to study the combustion processes of a gas discharge between an electrolytic anode and a metallic cathode immersed in an aqueous solution of sodium hydroxide. The possibility of applying a gas discharge with a liquid electrolytic anode for the production of zinc powder from alkaline solutions has been established.The pulsed mode can be used at the voltages of the I-V characteristic curve only in the region where intensive hydrodynamic disturbances are observed and where a gradual increase occurs in the area of the metallic electrode surface covered by the gas discharge (U = 150–215 V for a 1% solution, U = 100–125 V for a 3% solution, and U = 70–110 V for a 5% aqueous solution of sodium hydroxide).
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Orientation-dependent mechanical properties of 3D-printed components fabricated by selective laser melting of metal powders

https://doi.org/10.58224/2618-7183-2025-8-6-12
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Abstract
This study investigates the mechanical properties of aluminum alloys AlSi10Mg and AK9ch fabricated by selective laser melting (SLM), taking into account the build orientation (longitudinal, transverse, 45°) and applied heat treatment regimes (stress-relieving annealing, T6 treatment, prolonged aging). A comprehensive tensile test program was conducted to determine ultimate tensile strength, yield strength, elongation, and hardness. Results show that SLM-processed specimens significantly outperform conventionally cast AK9ch, especially after T6 treatment, achieving up to 285 MPa in strength with ~9% elongation. For the first time, it is demonstrated that the Russian casting alloy AK9ch is suitable for SLM technology, with post-treatment strength reaching 259 MPa and ductility ~5%, comparable to that of AlSi10Mg. The influence of build orientation was found to be negligible at high relative density (>99%). The findings confirm the potential of additive manufacturing to produce high-performance aluminum parts using domestic alloys, offering a promising path toward import-independent 3D production in Russia.
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Systemic-ecological symbiosis model: integrating secondary resources into construction materials to enhance the environmental safety of machine-building enterprises

https://doi.org/10.58224/2618-7183-2025-8-5-1
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The research addresses the integration of secondary resources from machine-building enterprises into construction composites as a pathway to reduce clinker consumption, lower the carbon footprint, and improve industrial sustainability. A symbiotic model was developed that links a machine-building plant as a donor of metallurgical, glass, and polymer by-products with construction material production as a recipient. The model operates on weekly “generation–utilization–storage” balances for production lots of 10 m³ and is optimized under three groups of constraints: economic (cost minimization), environmental (CO₂ intensity reduction), and technical (compressive strength, water absorption, and chloride permeability by RCPT). A multi-objective optimization scheme using ε-constraint methods was applied together with regression-based property models and stochastic simulations (Monte Carlo and bootstrap). The analysis demonstrates that partial clinker substitution with up to 50% ground granulated blast-furnace slag and up to 20% recycled glass achieves a 40–45% reduction in unit CO₂ emissions, while maintaining 28-day strength above 40 MPa and RCPT values within 2,000–3,000 C (Coulombs). The Pareto front highlights an equilibrium zone of 55–60% CO₂ and 84–87% relative cost as a rational compromise between environmental and economic performance. Statistical verification confirms the robustness of the solutions with failure probability Pf < 10%. Practical implications include the ability to design low-carbon mixtures with predictable durability, integrate secondary resource flows into construction supply chains with ≥95% utilization efficiency (and >97% for glass/ash streams), and reduce regulatory and environmental risks. The framework provides machine-building and construction industries with a reproducible methodology to scale decarbonization strategies while ensuring infrastructure reliability.
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Experience of concreting a massive monolithic foundation slab

https://doi.org/10.58224/2618-7183-2025-8-5-2
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The large number of recipe and technological factors affecting the stress-strain state of concrete in the initial period of massive monolithic structures erection predetermines the expediency of using modeling of temperature fields and stresses with software packages based on analytical and numerical solutions when developing technological regulations for concreting. Improving the algorithm for calculating temperature fields and stresses taking into account the kinetics of concrete heat release, heat exchange conditions, ambient temperature and the stages of construction of structures is a pressing task. A comparison was made of calculated, laboratory and natural values of some parameters when concreting a foundation slab with a volume of 1642 m3, a surface area of 821 m2, and a thickness of 2 m. Concreting was completed in 13.5 hours with an average intensity of concrete mix placement of 122 m3/h, and a peak intensity of up to 240 m3/h. A method for calculating temperature fields and stresses taking into account the staged nature of construction has been developed in the MATLAB environment. It does not require rebuilding the geometry of the finite element model, adding nodes and elements during the process of laying new layers, and allows for the correct consideration of the dependence of the strength and deformation properties of concrete on the degree of its maturity. The results of calculated and measured temperature values excluding heating from solar radiation showed a discrepancy of up to 10 °C on the upper surface at some points in time. Some discrepancy between the calculated and experimental values of stresses and deformations with a qualitative coincidence in the nature of the curves is due to the neglection of shrinkage and rapid creep of concrete and poor study of the deformation properties of concrete with additives based on polycarboxylate esters at an early age.
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Effect of substrates on the photocatalytic activity of the composite coating fabricated by detonation sprayed Ti powders

https://doi.org/10.58224/2618-7183-2025-8-5-3
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Composite coatings based on titanium oxides were successfully deposited on fine-grained concrete and porcelain tile substrates using a robotic complex for detonation spraying. The study focused on the influence of substrate roughness and composition on the microstructure, phase composition, and photocatalytic properties of the coatings. Dense, uniform coatings with a bimodal lamellar microstructure and thicknesses ranging from 20–30 µm on concrete to 250–300 µm on porcelain tiles were obtained without cracks or significant porosity. It was observed that the phase composition of the coatings, which included a mixture of titanium, anatase, rutile, TiO, and Ti₂O₃ phases, remained unaffected by variations in the substrate composition. Regardless of the substrate material used, all coatings exhibited similar phase constituents. However, the surface roughness of the substrates played a crucial role in determining the microstructure and photocatalytic performance. The rougher concrete surface promoted a higher anatase content, resulting in enhanced photocatalytic activity compared to coatings on smoother porcelain tiles. Coating thickness and porosity did not significantly affect photocatalytic efficiency. Additionally, the kinetic constants of the obtained coatings exceeded those of commercial sol-gel coatings and aligned with values typical for thermally sprayed coatings. The obtained results indicate that composite titanium oxide coatings demonstrate high potential for industrial applications where effective breakdown of organic pollutants on diverse surfaces is required.
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Wall materials based on low-grade loams and industrial waste

https://doi.org/10.58224/2618-7183-2025-8-5-4
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Abstract
Clay raw materials used in Kyrgyzstan for the ceramic industry characterized as low-plasticity , highly sensitive and saline. In addition, the high content of carbonates in loams leads to the production of low-quality bricks. In order to obtain ceramic bricks with high-quality performance characteristics, it is necessary to use innovative approaches in the preparation of clay raw materials.
The raw used materials were local loess-like loams from the Orok deposit and ash from the Bishkek thermal power plant and a surfactant – sodium naphthenate. The loam and ash subjected to mechanochemical activation by joint grinding in activator-mixer and adding sodium naphthenate together with mixing water. The dried cylindrical samples fired in the temperature range of 900, 950 and 1000 0 C.
The results of the studies showed that mechanochemical activation of ash-clay raw materials increases the plasticity of the clay-ash mass by 140 %, while reducing the molding moisture and sensitivity coefficient.
The sintering process is intensified: at a firing temperature of 950 0C and 60 % ash, it is possible to obtain a shard with a density of 1.57 g/cm3 and water absorption of 17 %. The compressive strength is 16.3 MPa.
Amorphization and destruction of raw material particles contribute to an increase in the glass phase content. As a result, open pores are tightened, forming a strong monolithic structure.
The obtained samples based on mechanochemical activation with the addition of 60 % ash have the M150 grade and frost resistance of F 25.
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