Resource-saving materials, structures, buildings and structures
These new results of fundamental and applied research in the field of building materials and their production technologies, theories of resistance elements of building structures outside influences, methods of calculation. Some questions on the basics and foundations and strengthening of buildings
NATIONAL UNIVERSITY OF WATER AND ENVIRONMENTAL ENGINEERING
THE CONCEPT OF USING RECYCLED CONCRETE AGGREGATES IN LOW-CARBON CONCRETE TECHNOLOGY
The concept of using recycled concrete aggregates (RCA) contributes to the further development of one of the most promising sustainable construction technologies, which is consistent with the principles of the circular economy and decarbonization of the industry. The use of Portland cement with limestone CEM II/A-LL 42.5 R, combined active pozzolanic additive "fly ash - microsilica" ensures uniform passage of the pozzolanic reaction of components at different structural levels in the formation of a cementing matrix, which largely determines the characteristics of the modified concrete. The combination of components with polycarboxylate ethers provides modification of the mesostructure of the cementing matrix of concretes based on RCA and creates the possibility of achieving high mobility of mixtures and increasing the strength of recycled aggregate concretes. Multi-component cementitious materials fill the pore space of the cement paste and contribute to the compaction of the interface transition zone due to the reaction with calcium hydroxide to form C-S-H gels, which leads to improved recycled aggregate concrete characteristics. The integration of RCA into the production of building materials is an important step towards reducing construction waste, conserving natural resources and creating competitive solutions for the green transformation of the construction sector.
Copyright (c) 2025 Resource-saving materials, structures, buildings and structures
PROSPECTS OF USING COFFEE WASTE FOR THE PRODUCTION OF ECOLOGICAL CONCRETES AND MORTAR
approaches to enhance the value of coffee industry by-products in the formulation of sustainable concretes and cement mortars. The areas of application of coffee grounds in the production of ecological concretes and cement mortars are summarized. Five main areas of use are highlighted: pozzolanic additives that replace part of the cement; organic fibers that can improve crack resistance; rheological additives; modifiers or corrective additives; partial replacement of fine aggregates in the cement mixture. A detailed analysis of experimental studies demonstrates how partial replacement of fine aggregates or cement with coffee waste can change key material properties, including density, compressive strength, thermal conductivity, shrinkage behavior and durability indicators such as water absorption. In addition to technical characteristics, the environmental benefits of this approach are critically evaluated. Indeed, the use of coffee waste achieves the dual benefit of diverting organic waste from landfills and simultaneously reducing material costs. Finally, we outline promising directions for future research, including optimization of mix design, long-term durability studies under different environmental conditions. By reflecting the current state of the art and pinpointing knowledge gaps, this review aims to guide materials scientists, civil engineers, and sustainability practitioners toward unlocking the full potential of coffee waste as a resource for sustainable building materials.
INFLUENCE OF PLASTICIZING-ACCELERATING ADDITIVES ON THE KINETICS OF CONCRETE STRENGTH AT ALTERNATING TEMPERATURES
The article presents the results of a comprehensive study on the influence of polycarboxylate-based superplasticizers and non-chloride hardening accelerators on the strength development kinetics of concrete under alternating temperature conditions, which are typical for the cold seasons. The difference between these types of additives is depicted: the polycarboxylate ether-based superplasticizer demonstrated a significant water-reducing effect, improving workability and strength by enhancing cement particle dispersion and hydration. However, it slightly delayed the early strength gain. The addition of the hardening accelerator compensated for this effect by promoting rapid hydration of clinker minerals and slightly lowering the freezing point of the mix water. The findings confirm that the combination of polycarboxylate superplasticizers and hardening accelerators is an effective technological solution for enhancing the strength development kinetics of concrete in fluctuating and low-temperature environments. Such an approach promotes faster early strength development, facilitating earlier formwork removal and load application. At the same time, it allows for reduced cement usage and lowers the energy requirements for heating concrete during cold-weather construction. Winter concreting presents significant technological challenges, including the risk of freezing water within the concrete matrix. One of the most critical factors is the prevention of water freezing inside the concrete matrix and ensuring the achievement of a minimum critical strength as early as possible. Therefore, it is necessary to use heated mixing water to maintain the initial temperature of the concrete mix above +5 °C. Proper curing conditions should also be ensured throughout the early hardening period.
GLASS DESIGN IN ACCORDANCE WITH THE TECHNICAL SPECIFICATION SIA 2057
The analysis of technical specifications and drafts of parts of the future Eurocode 10 (EN19100) has resulted in the highlighting of the provisions and features necessary for the practical calculation of load-bearing structures made of single and laminated glass. Glass components are designed for the following limit states: Serviceability Limit State (SLS), when the glass does not fracture; Ultimate Limit State (ULS), when the glass does not fracture; Fracture Limit State (FLS), during fracture; Post Fracture Limit State (PFLS), when the glass has fractured. In addition to the classification by Consequence Classes (CC), glass components are classified into Limit State Scenarios (LSS). The basic principles of glass design in accordance with the Swiss Technical Specification SIA 2057 and the future Swiss Standard SIA 268 are presented. Fracture conditions are divided into five classes from 0 to 4 according to the fracture state verification (‘Nachweise im Bruchzustand’, NB): NB 0 - no additional verification; NB 1 - to be verified in a partially fractured state under its own weight; NB 2 - to be verified in a fully fractured state under its own weight; NB 3 - to be verified in a partially fractured state under its own weight and other loads: NB 3A - with one broken glass layer, NB 3B - with two broken glass layers; NB 4 - to be verified in a fully fractured state under its own weight and other loads. SIA 2057 applies to the design of load-bearing structures and components made of glass as well as to temporary structures. It regulates the structural analysis and design of the following glass components: vertical glazing, horizontal glazing, insulating glazing, fall-protection glazing, accessible glazing, walk-on glazing, trafficable glazing, glass components subject to compressive stress (buckling), glass components subjected to bending around the strong axis (tilting).
Saving fuel and energy resources, rapid construction of new housing and reconstruction of damaged ones, increasing the efficiency of thermal insulation of buildings and structures, and introducing energy-efficient materials are priority areas in the development of the construction industry. One of the effective building materials is structural and heat-insulating gas concrete. In practice, products made of structural and heat-insulating gas concrete of autoclave hardening have found wide application, the production of which is characterized by high energy consumption, metal consumption, and a large production area. The relevance of this work is that the preparation of non-autoclave gas concrete can be carried out from pre-prepared dry mixes. The advantages of dry building mixes for aerated concrete are high dosing accuracy and a high degree of homogenization of components, which ensure the stability of technological and operational-technical properties of the material. The use of dry building mixtures for the production of structural and heat-insulating gas concrete can be promising in low-rise monolithic construction. Monolithic housing construction is most appropriate in rural areas. Dry building mixtures for gas concrete include a binder, a gas former and regulators of the structure formation of gas concrete. Most often, the following are used to obtain gas concrete: binder - Portland cement grade 500; gas former - aluminium powder PAP 1, 2, PAK-3. Based on the conducted research, non-autoclaved gas concrete D 600 with stable density and strength indicators was obtained
TESTING OF A PRECAST BEAM REINFORCED WITH INDIVIDUAL BARS AND MANUFACTURED BY 3D PRINTING
The publication is devoted to the testing of single-span beams reinforced with individual rebars without transverse reinforcement and manufactured by 3D printing. The purpose of the study is to test beams reinforced with individual longitudinal rebars without transverse reinforcement and manufactured by 3D printing according to the developed methodology. To accomplish this task, two samples of beams were designed and printed on a 3D construction printer. The article presents the design solutions and working drawings of the samples. The beams were 1700 mm long and 150x100 mm in cross-section. The scheme of the laboratory bench with the marked measuring instruments is presented in the paper. In total, sixteen clock-type micro-indicators with a division price of 0.001 mm were used to determine the deformations of concrete and reinforcement, three clock-type indicators with a division price of 0.01 mm to determine the deflection and settlement of the supports. As a result of the experiment, the fracture pattern of the beam was determined, the value of the critical breaking moment was determined, as well as the nature of the increase in deflections and the increase in deformations of reinforcement, compressed concrete, and in inclined sections.
METHODS OF PRODUCING CELLULAR CONCRETE USING FLY ASH
The fly ash from power plants is a man-made raw material for many industries. It is utilized up to 92% in dry form and is of practical interest in the production of effective thermal insulation building materials and products as a filler and aggregate. The feasibility of producing non-autoclave gas-ash slag concrete using cement with an increased content of highly basic minerals - alite and tricalcium aluminate - has been proven. The technology of obtaining ash-alkali cellular concrete using fly ash and an alkaline component is presented. The economic efficiency of cellular ash-intensive concretes is justified by the replacement of sand with ash, and a 1.2-1.5 times less in lime consumption compared to lime-sand concrete, as well as approximately 2 times less in capital costs for the extraction and processing of raw materials. Comparative physical and mechanical properties of autoclaved and non-autoclaved aerated concrete products are presented. The process of manufacturing products by vibrovacuuming and vibrocompaction of ash concrete is shown. The presented data show that the strength of vacuum ash concrete is 30-40% higher than that of vibration-compacted concrete with a rigid mixture.
CONCRETES AND MORTAR BASED ON TPP WASTE ASH
Tens of millions of tons of various secondary mineral resources have accumulated in landfills, dumps, and storage facilities in the Dnieper region - ash and slag mixtures from thermal power plants (TPPs), etc.). Theoretical and experimental studies have shown that vibrovacuum compaction is a more effective method of compacting fly ash concrete compared to the traditional method of vibration compaction. Compaction of concrete mixtures using vibration vacuum makes it possible to significantly increase the density, strength, frost resistance and other properties of such concretes. For concretes with the same strength, it is possible to reduce cement consumption. In this case, it is possible to carry out immediate demolding, as well as significantly reduce the duration of heat treatment. The proposed molding method does not require significant capital costs for implementation, since it uses standard equipment that is widely used in the construction industry and reinforced concrete technology. The relevance of the work is the development and research of the technology of vibrovacuum processing of concrete mixtures based on secondary mineral resources, which allows obtaining high-quality concrete (increased density with strength and other properties). A method of improving the quality of ash-slag vacuum concrete by adding a small amount of electrolyte to the concrete mixture during its preparation is proposed. The main properties of vibrocompacted and vibrovacuum-filled concretes based on secondary mineral resources were investigated, a comparative assessment of these properties was carried out, and the advantages of vacuum concretes were proven. The most objective assessment of the strength characteristics and other physical and mechanical properties of concrete based on secondary mineral resources, compacted by vibration vacuum, can be obtained in production conditions, for example, in reinforced concrete plants.
ДОСЛІДЖЕННЯ ПРОГИНІВ В ЗАЛІЗОБЕТОННИХ АРКАХ З ВИСОКОМІЦНОГО БЕТОНУ НА ДІЮ КОРОТКОЧАСНИХ СТАТИЧНИХ МАЛОЦИКЛОВИХ ПОВТОРНИХ НАВАНТАЖЕНЬ
The issue of improving Ukraine's defense capabilities in this difficult time is now an urgent one. There is an urgent need to build new and restore destroyed defense and civil defense facilities. In order to achieve the fastest possible pace of construction of defense facilities, it is proposed to use high-strength quick-setting concrete. The use of high-strength concrete can significantly reduce the volume of concrete, and thus the dead weight of structures, and reduce the consumption of reinforcing steel in reinforced concrete structures. This type of heavy concrete can significantly reduce the time required to construct structures, increase the strength and reliability of structures and the building as a whole. One of the effective structural schemes of a civil defense protective building (shelter) is a combination of structural elements made of monolithic reinforced concrete and prefabricated elements in the form of two-hinged arches made of high-strength concrete.
RECONSTRUCTION OF THE HOSPITAL BUILDING WITH INSPECTION OF THE TECHNICAL CONDITION OF THE STRUCTURES
A technical inspection of the hospital building structures was carried out to assess its actual technical condition, in particular the condition of the building elements. As part of the inspection, a visual inspection of the facility was carried out, a structural diagram of the building was established and a detailed analysis of the main load-bearing elements, such as foundations, walls, floors, roof structures and roofing, was carried out. According to the results of the inspection, typical defects and damage were recorded, photo documentation of the identified shortcomings was carried out and recommendations were formulated for their elimination to ensure the safe further operation of the building. In addition, in order to prepare design documentation for the reconstruction, detailed measurements of the internal premises were made and relevant drawings were developed that reflect the current state of the facility.
INVESTIGATION OF THE RECYCLED CONCRETE FINES AS A MINERAL ADDITIVE FOR CONCRETE
This research investigates the potential of utilizing the recycled concrete fines (RCF) as a partial replacement for Portland cement in concrete production. The study addresses the growing concern of construction and demolition waste management, particularly in the context of Ukraine's post-war reconstruction and alignment with European Union environmental regulations (specifically, Regulation (EU) 2024/1159). The research focuses on the influence of key concrete mix parameters on workability and compressive strength. These parameters include the water-cement ratio (W/C), the percentage of cement replaced by the RCF (<0.3 mm), and the dosage of superplasticizer (SP). A designed experiment approach was employed to analyze the effects of these factors. The results of the study are presented through regression models that describe the relationships between the mix parameters and concrete workability and strength (at 3 and 28 days). The findings indicate that the W/C ratio is the most influential factor on compressive strength, while the superplasticizer dosage primarily affects workability. Notably, replacing up to 10-15% of cement with the RCF does not significantly compromise strength and has a limited impact on workability. The research also reveals an interaction between factors, where the effect of RCF is more significant at higher W/C ratio. This research contributes to the development of sustainable concrete production methods by providing valuable insights into the effective utilization of recycled concrete waste. The findings support efforts to reduce reliance on virgin materials, minimize waste, and promote circular economy principles within the construction sector, particularly in the context of reconstruciton efforts and adherence to evolving environmental standards.
EXPERIMENTAL RESEARCHES OF THE STRESS-STRAIN STATE OF HEAVY CONCRETE UNDER SMALL CYCLE LOADING OF HIGH LEVELS
Structural elements are exposed to cyclic loads, the effect of which on the strength and deformation properties of the material has not been studied sufficiently. The impact of such loads can cause special destruction in structures, in which deformations will increase significantly under cyclic loads, not exceeding the single limit load. The purpose of the work is an experimental and theoretical study of the stress-strain state of heavy concrete prism specimens under the action of high-level cyclic loads. The methodology and results of experimental studies of the stress-strain state of heavy concrete prism specimens under high-level cyclic loading are presented. The upper level of low-cycle loading affects the performance of concrete. The dependences of the change in relative longitudinal and transverse deformations and the diagrams of linear correlation dependences of the secant moduli of longitudinal and transverse deformations of concrete prisms under low-cycle loads of high levels were obtained. A sequential three-stage deformation of concrete has been established: Stage I - gradual decrease in the increase in deformations and the width of hysteresis loops; Stage II - stabilization of the increase in deformations, hysteresis loops at the loading stages repeat each other; Stage III - increase in the increase in deformations, the width of hysteresis loops. The constructed volumetric deformation diagrams allow us to trace the trend of concrete deformation with increasing number of load application cycles. The low-cycle fatigue limit of the studied concrete was established at ncyc → ∞, the value of ηcyc = 0.747. Repeated high-level compressive loads lead to gradual decompression of the structure from cycle to cycle, "grinding" of the material, and its destruction occurs.
THE INFLUENCE OF FINE AGGREGATES ON THE CHARACTERISTICS OF VIBRO-COMPRESSED CONCRETE BASED ON ULTRA-HARD MIXTURES
The publication highlights the problems of physical-mechanical and physical-chemical properties of inert aggregates and cohesive vibro-pressed shaped paving elements, which are manufactured on modern blockmaking machines of leading German machine-building manufacturers based on fine-grained ultra-hard and hard concrete mixtures in the latest conditions of development of the construction industry in Ukraine. An analysis of factors affecting the operation of concrete paving stones and causing increased requirements for their physical-mechanical properties has been conducted. In this article, the author studies the granulometric composition, sieving curves, chemical composition, X-ray phase analysis of the product of grinding strong rocks, washed construction sand with gradation factor more than 2.1 and the chemical composition of Portland cement CEM 42.5 produced by "Ivano-Frankivskcement", which are used in the production conditions of the Trade Mark "Mii Dvir" for the production of fine-grained concrete mixtures using specialized dosing and mixing equipment in the process of serial production of figured paving elements. The article determines the main factors that form the strength characteristics and durability of concrete at the early and late stages of its hardening; considers the factors that create conditions for factory vibropressing of products of this category and provides components that should be considered optimal for creating highly efficient ultra-hard concrete mixtures. The materials of the publication present experimental data on the content of the main components of concrete in each of the layers of building products. These studies were conducted in the scientific laboratory of the National University "Lviv Polytechnic" according to domestic and European standards by the method of forming beams measuring 40x40x160.
Bridge operating conditions are often characterized by the impact of aggressive environmental factors that lead to intense corrosion of steel reinforcement, a traditional material for reinforcing reinforced concrete structures. The search for and implementation of new, durable and corrosion-resistant materials for reinforcement is a priority for modern bridge construction. One of these promising materials is non-metallic composite reinforcement made on the basis of high-strength glass or basalt fibers and a polymer binder. It has a number of advantages over steel, which makes it attractive for use in bridge structures. The article is devoted to the study of the use of composite reinforcement in bridge construction, in particular for reinforcing girders of span structures. The aim of the work is to compare the efficiency of using steel and composite reinforcement (fiberglass and basalt) in a 12 m long girder of a span structure. The calculations were performed in the LIRA-FEM software package using finite element modeling. Static and structural calculations were performed for four reinforcement options: steel reinforcement, fiberglass reinforcement, basalt reinforcement, and non-metallic composite periodic profile reinforcement. The results of calculating the required reinforcement area for 4 design variants are presented, separately to meet the requirements of the first and second groups of limit states. Also, the required reinforcement area is compared with its total weight in the beam. The stress-strain analysis confirmed the acceptability of the composite reinforcement in terms of strength characteristics. At the same time, the low modulus of elasticity of composite materials requires careful design for load-bearing structures due to the higher deformations. The study emphasizes the economic and technical advantages of composite reinforcement to improve the durability and efficiency of bridge structures, as well as the need for further research to optimize its use in real-world projects.
NANOMODIFICATION OF CEMENT SYSTEMS AS AN EFFECTIVE WAY TO IMPROVE THE QUALITY OF SPECIAL-PURPOSE BUILDING MORTARS
The principles of compositional construction of nanomodified special-purpose mortars with improved performance characteristics are proposed, which involve optimization of the processes of structure formation not only at the nanolevel, but also at the micro- and meso-levels of their structure. The properties of waterproofing mortars based on cement systems modified with carbon nanotubes, which are distinguished by improved properties, are studied. The properties of optimized decorative plaster mortars based on white cement modified with nanocarbonate additives in the presence of a polycarboxylate superplasticizer are also considered, which are characterized by durability, low porosity, sufficiently high strength, crack resistance, which is achieved by controlling the processes of structure formation of artificial stone both at the nano-, micro- and meso-levels.
DETERMINATION OF THE HEAT TRANSFER COEFFICIENT OF THE WALL OF A MULTI-STOREY RESIDENTIAL BUILDING BY THE THERMOMETRIC METHOD
During thermal modernization of existing buildings and assessment of energy parameters of new housing, there is a need for experimental in-kind determination of the heat transfer coefficient (heat transfer resistance). In our opinion, the optimal method for determining it is the thermometric method (THM). Its equipment is cheaper, the sensors do not disturb the measured heat flow, and temperature measurement is affected by fewer factors than when using a thermal imager. The thermometric method is not standardized, but along with this, it is widely used to measure the heat transfer coefficient during energy audits, in commercial devices. During the research, experimental in-kind measurements were carried out over certain periods of the temperatures of the internal environment, external environment, and internal wall surface. Before taking measurements, the internal wall surface was examined with a thermal imager to select an area with minimal impact of heat-conducting inclusions. The wall surface temperature in the room was measured by three type K thermocouples placed at a distance of approximately 15 cm from each other and recorded by a recorder at a specified interval. The thermocouples were placed so that they were not on the same horizontal or vertical line. Average temperature values ​​were entered into the calculation. The temperature of the environment inside the room was measured by a temperature recorder, which was placed at a distance of approximately 30 cm from the wall surface at a height of 1.5 m, the same as the height of the thermocouples on the surface. The temperature of the outside environment is recorded by a logger. Thermologgers recorded the temperature of the air environment at a given interval. Using the temperatures measured at a given interval, the heat transfer coefficient of the wall of a residential building was calculated using the thermometric method (THM). The heat transfer coefficient of the inner surface of the wall is adopted according to DSTU. An analysis of the influence of various factors, in particular measurement intervals, on the value of the heat transfer coefficient was performed.
COMPOSITE CEMENT BINDERS USING SYNTHESIZED ALUMOSILICATES
The article presents a literature review, the results of which show that materials obtained on the basis of alkaline activated binders (geopolymers) have low permeability and high pH of the pore fluid, which provides them with good resistance to chloride corrosion of reinforcing steel. The good resistance of geopolymers to aggressive environments and temperature changes makes these materials suitable for operation in adverse conditions. Thus, according to literature data, geopolymers are of interest as matrices for the immobilization of toxic and radioactive waste. Compared to Portland cement, which is currently used to solidify low and medium-level nuclear waste, geopolymers provide the resulting materials with greater stability. Technological aspects of the preparation of concretes based on alkaline activated binders and their construction and technical properties are basically similar to the technology and properties of concretes based on PC, although in the synthesis of geopolymer concretes, as a rule, thermal activation is always required. Temperature significantly accelerates the process of dissolving the initial aluminosilicate framework and thus has an important effect on the hardening of geopolymer compositions, especially in the initial reaction period. Fly ash at normal temperature reacts very slowly and even after a month of hardening under normal conditions gives insignificant strength. However, keeping a freshly prepared product at 70-90 ° C for several hours to 1 day allows you to achieve almost the final strength, which is up to 60-70 MPa (according to some data, the strength of geopolymers can reach 100 MPa and more). Among the reasons why geopolymers have not yet been widely used is their insufficient study (mostly due to the heterogeneous composition of the raw materials).
EXPERIMENTAL CORROSION-MECHANICAL STUDIES OF WELL-DRYING EQUIPMENT IN THE OIL PRODUCTION INDUSTRY UNDER DYNAMIC LOAD IN AN AGGRESSIVE ENVIRONMENT
In the first, comprehensive experimental studies of full-scale welded joints and steel structures under dynamic loading in the presence of a corrosive environment, in particular 5% saline solution and NACE - an environment according to the requirements of the International Association of Corrosion Engineers. The authors of this article developed a test bench scheme and worked out the expected modes of testing welded joints when programming the pressure and temperature of the environment and dynamic vibration modes. The test rig was manufactured jointly with specialists from the E.O. Paton Institute of Electric Welding of the National Academy of Sciences of Ukraine. All the main units of the rig are a hydropulsator, a thermal chamber, which included pipeline blocks with experimental welded joints, heating devices, a pneumatic control panel, a temperature and pressure control unit. The obtained experimental results made it possible to summarize, in particular: it was established that in the initial period (number of cycles N = 500) the crack growth rates in air and in 5% NaCl solution are close, and in the final period of testing they differ by more than an order of magnitude. Due to the more intense influence of the plane deformed state compared to the plane stressed state, the crack propagates in depth and only after germination over the entire thickness of the sample does its elongation begin. A significant reduction in the test period due to the introduction of a crack in the sample with a high stress concentration at the crack tip, which allows you to significantly reduce or modify the initial period. The possibility of detecting the sensitivity of materials to cracking, which is not detected when testing samples without a concentrator (for example, for pipe steels in seawater). However, the fracture mechanics method, like any other method, has a number of specific limitations on materials, thickness, and environments related to the correct use of fracture mechanics.
EFFECTIVE HIGH-STRENGTH RAPID HARDENING CONCRETE
The Department of Building Products Technology and Materials Science NUWEE has conducted a number of studies on reducing the resource and energy intensity of the production of high-strength rapid-hardening concrete. It has been established that it is possible to obtain concrete with a compressive strength of up to 90 MPa at the age of 28 days and up to 50% of the 28 days strength at the age of 1 day using composite cements containing 50% clinker, 12% blast furnace slag and 35% fly ash. The cement contains a complex additive of propylene glycol and a superplasticizer. It has been experimentally shown that metakaolin can serve as a substitute for microsilica as an active mineral additive when producing high-strength concrete. A technology has been developed for producing high-strength rapid-hardening concrete based on activated low-clinker cements. Activation of cement containing 12% clinker is achieved by introducing a complex additive of lime and silicon sodium fluoride. The possibility of obtaining high-strength self-compacting and reactive powder ash and slag-containing concretes has been substantiated. The effectiveness of dispersed reinforcement of high-strength concretes with steel and basalt fibers has been determined.
INFLUENCE OF DAMPING AND PRESSURE DURATION ON THE STRENGTHS OF STRUCTURES UNDER EXPLOSIVE LOADING
The article presents an analysis of the influence of the damping coefficient, the phase of structural vibrations, and the duration of the explosion wave on the magnitude of the dynamic factor. Different methods for determining the dynamic factor depending on these factors are considered. In the literature, the disregard of damping is associated with simplifying calculations. The article demonstrates that in some cases, to save materials, the dynamic factor can be reduced by up to 16%. When considering the actual curvilinear pressure diagram of the explosion wave, the maximum response of the system may occur in the first phase of oscillations. Therefore, it is shown that instantaneous impulse calculation is not always applicable. By considering the damping coefficient (if objectively justified) and the actual curvilinear pressure diagram, materials can be saved by reducing the dynamic factor. It is demonstrated that a more accurate calculation method is direct integration of the equations of motion. However, for multi-mass systems, solving these equations is only possible through numerical methods. In such systems, the vibration frequencies for different modes can significantly differ. Thus, the question arises of which integration step to choose for a more accurate solution, as an optimal step for one frequency may not be suitable for another. In such cases, a better approach is the well-known modal superposition method, which transforms the coupled system of differential equations in physical coordinates into independent differential equations in modal coordinates. These second-order differential equations for a linear oscillator are easily solved in closed form, allowing the derivation of an analytical solution for both linear and curvilinear pressure functions, with or without considering the negative pressure phase. Given that these equations are analytically solvable, the problem of selecting the appropriate integration step is automatically eliminated.
DETERMINING THE WEAR RESISTANCE OF A PARQUET BOARD
There are many different types and methods of experimental tests that mimic the different types of loads of lacquered surfaces used. The main indicators of the quality of lacquered surfaces of wooden floors are adhesion, elasticity, impact resistance, wear resistance and resistance to various liquids, mechanical damage, abrasion, etc. During the test of wooden coatings for wear resistance, laboratory tests should simulate the operating conditions of wooden floors. However, mainly all methods of experimental tests are standardized, but some of them do not allow to determine the minimum requirements or control values of certain technical properties of different paint surfaces. Which in turn creates a dilemma for technologists or even consumers, who are expected to determine the quality requirements of certain products. The article presents the results of experimental research to determine the coefficient of abrasion of the surface layer of the parquet board and to establish the class of its resistance to abrasion according to the results of the Taber test. They can serve as information for the relevant properties of wooden floor surfaces and be aimed at better knowledge of information on experimental tests of floor coverings for wear resistance.
PRESSED MATERIALS BASED ON WASTE CONCRETE POWDER
This study investigates the feasibility of using the fine fraction of crushed concrete waste as a component for producing pressed construction composites. It is assumed that powdered concrete waste can harden under pressure through a mixed mechanism involving contact-crystallization and partial hydration, especially if unhydrated cement particles remain in the material. Four types of concrete waste were tested, differing in age, strength, and cement content. Specimens were pressed at 20 MPa, a pressure commonly used in the production of autoclaved materials. Results showed that samples made from waste with higher cement content and lower age achieved the highest strength – 13.4 MPa at 28 days – and average density of 1.62 g/cm³. Softening coefficients near 0.9 indicate sufficient water resistance. Strength increased steadily over time, peaking at 7–10 days, confirming active structure formation in pressed conditions. The curing method had a notable effect. Optimal results were obtained under high humidity (in a desiccator), preventing moisture loss. Air-dry curing was less effective due to rapid drying, while water immersion showed slightly reduced strength, likely from excess water disrupting structural development. A correlation was observed between strength and the mineral composition of the waste, particularly alite and calcium hydroxide content. A pH test of aqueous extracts is suggested as a rapid screening method to evaluate the suitability of waste concrete for pressing. The findings confirm the potential of recycled concrete fines in producing pressed composites with properties comparable to those of common ceramic materials.
STRESS-STRAIN STATE OF REINFORCED CONCRETE WHEN EXPLOSIVES ACT ON IT IN ENCLOSING STRUCTURES OF PROTECTIVE STRUCTURES OF CIVIL BUILDINGS
The results of theoretical and experimental studies of the properties of reinforced concrete and its improvement, especially under dynamic and extreme loads, are presented. The main attention is paid to the analysis of the influence of dynamic explosive waves on the mechanical properties of concrete and the optimization of its composition using fiber. Research confirm that the use of polymer fiber in concrete mixtures significantly improves the mechanical characteristics of the material, providing increased crack resistance, impact strength and durability. Fiber concrete demonstrates the ability to effectively counteract dynamic loads, which makes it promising for use in protective structures, especially in high-risk areas. Fiber concrete is significantly superior to traditional concrete due to its ability to slow the spread of cracks, which reduces the risk of brittle fracture. In explosive conditions, this is critically important, since ordinary concrete has a tendency to sharp destruction with the formation of fragments that can pose an additional threat. The inclusion of polymer, steel or glass fibers in the concrete mixture allows to achieve a uniform distribution of stresses and improve the overall mechanical properties of the material. Experimental studies have confirmed that fiber concrete beams show an increase in limiting moments by 20-40% compared to traditional concrete elements. Reinforced concrete structures with the addition of fiber helps to reduce the risk of sudden destruction and the formation of dangerous debris, which increases safety when used in civil protection structures. Further development of such materials opens up wide opportunities for their adaptation to modern construction challenges, in particular under martial law, ensuring their reliability, durability and economic efficiency of the structure.
RESTORATION OF THE OPERATING SUITABILITY OF LARGE-PANEL BUILDINGS DAMAGED AS A RESULT OF MILITARY ACTIONS
The article examines the features of restoring the operational suitability of large-panel residential buildings damaged as a result of military actions. The need for restoration is due to socio-economic factors in the current conditions on the territory of Ukraine. Large-panel buildings make up a significant proportion of residential buildings damaged as a result of military operations. The experience of restoring large-panel residential buildings presented in the article reveals the need to implement experimental technical solutions. In order to restore the operational suitability of damaged panel objects on a large scale, it is necessary to develop non-typical constructive solutions and improve calculation methods. The key issue in restoring the operability of panel buildings is the reliability of the connections between existing and new slabs.
QUESTIONS OF STRUCTURAL FORMATION OF CEMENT CLINKER WHEN USING INDUSTRIAL WASTE
The use of waste from other industries as a component of raw material mixtures for producing cement clinker requires taking into account their complex impact on the processes of structure formation in the technological production cycle. This work examines the features of the structure formation of raw material mixtures using high-tonnage waste from the thermal power industry in the technological process of cement clinker production. The object of the study was three-component raw material mixtures based on silicate systems of limestone with various alumino-silica-containing components and fly ash from the Burshtyn TPP. The work used a combination of modern physicochemical analysis methods with standardized testing of raw material and binder properties. Structural, mechanical and rheological properties of cement slurry samples were determined using Weiler-Rebinder and Rheotest-2 devices. X-ray phase analysis of clinker samples was performed using a DRON-3M diffractometer. Using the computer program "Clinker", a quantitative assessment of the possible volumes of waste utilization was given and the composition of mixtures with a content of 8.5 to 15.5 wt. % of fly ash was determined. The influence of fly ash on the structural, mechanical and rheological characteristics of sludge is shown, which determines the possibility of regulating its stability in working tanks and fluidity during transportation through pipelines. The increased content of iron oxides and the glass phase of fly ash contribute to the intensification of sintering of the mixture during firing with changes in the phase composition of clinker. It has been determined that the development of the physicochemical principles of the structure formation of silicate systems in the processes of clinker production using technogenic raw materials is an important aspect of further modernization of technology and equipment of modern cement production.
INFLUENCE OF REINFORCEMENT ON THE STRESS-STRAIN STATE OF A CURVED GLUED-LAMINATED TIMBER STRUCTURE
Timber is widely used in construction, particularly as elements subjected to bending and combined compression with bending. One of the main disadvantages of timber structures is their insufficient stiffness under bending, which leads to significant deformations. Reinforcement of solid and gluelam timber provides an effective solution to this issue. However, current Ukrainian standards for the design of solid and glued timber structures lack guidelines for the calculation of reinforced elements, despite their proven effectiveness in reconstruction, strengthening, and new construction projects. To validate the modeling methodology of timber deformation, a numerical analysis was conducted using the LIRA-SAPR software package, which applies the finite element method. This software enables the determination of displacements and the stress-strain state of structures using different types of finite elements. The results obtained can be used to verify the modeling process and compare it with deformation-based analytical methods, which supports the relevance of their application. The efficiency of LIRA-SAPR has also been confirmed through multiple studies and expert evaluations. The aim of the study is to improve the design process of reinforced solid and glued timber structures by numerically modeling reinforced and non-reinforced curved laminated timber elements in LIRA-SAPR and comparing the results with those from deformation-based analytical approaches. The study involved the creation of a numerical model of a curved gluelam timber structure used as a roofing element. The structural geometry, physical and mechanical properties of timber and reinforcement, and loading conditions were defined based on existing research. Modeling was conducted using volumetric finite elements with orthotropic material properties, and reinforcement was simulated through embedded bars in tension and compression zones. Results showed a significant reduction in timber stress due to reinforcement, which also led to decreased displacements in both vertical and horizontal directions. A comparative analysis of internal stresses obtained via LIRA-SAPR and those calculated using deformation methods indicated that the software tends to yield slightly higher values in timber stress, while the reinforcement stress was found to be lower in analytical calculations. Overall, the study highlights the effectiveness of reinforcing curved timber structures, particularly in areas subjected to the highest bending moments. Modeling with LIRA-SAPR enables detailed assessment of the stress-strain state, supports the adoption of rational reinforcement strategies, and helps identify zones of shear stress concentration. The results confirm the importance of using advanced finite element modeling tools for the accurate analysis and design of complex timber structures.
DAMAGE ANALYSIS AND PROPOSALS FOR THE RESTORATION OF HEAVILY LOADED DEFORMED BRICKWORK OF BUILDINGS WITH THE POSSIBILITY OF INSTALLING BUILT-IN CIVIL DEFENSE STRUCTURES FROM STEEL CONCRETE
Brick structures are a traditional and effective solution for multi-storey residential construction. Soaking and destruction of brickwork as a result of prolonged temperature and humidity effects are serious problems that arise due to various external factors. The paper analyzes the damage to brick heavily loaded structures (walls, partitions, pillars) of a public building that occurred after prolonged temperature and humidity effects as a result of the building being in an unfinished, non-preserved state. The description of typical damages to brick walls is based on the results of an inspection of an unfinished brick building that has been in a state of suspended construction without the implementation of preservation measures for about 8 years. The building has external longitudinal load-bearing walls 510 mm thick; internal longitudinal load-bearing walls 380 mm thick; partitions between rooms 120 mm thick. At the time of the inspection, there were actually load-bearing brick walls on two floors and reinforced concrete floor panels under the first, second, and third floors. On the third floor, the brick exterior walls and internal partitions were built to a height of 1...2 meters from the top of the reinforced concrete floor slab. The main damage to the brick wall structures is their frost damage of up to 40%, which is mainly due to the different porosity of the bricks and their exposure to precipitation. The second part of the article presents proposals for increasing the bearing capacity of brickwork by means of tie clips made of 75×6 mm steel corners on 100×8 mm strips. Recommendations have been developed for the installation of these cages with their inclusion in joint work with existing brick elements. To do this, the lower end of the steel posts is installed through the distribution angle on a concrete pad, and the upper ends of the posts are brought under the distribution angle at the top of the opening or at the bottom of the floor elements. Thus, the bearing capacity of the resulting combined structures is calculated using the same algorithm as for steel and reinforced concrete structures.
MIX DESIGN APPROACH FOR HIGH TEMPERATURE RESPONSE FOR OPC
Substitution a part of the clinker with fly-ash (further, FA) and application of alkali metal compounds are considered as the main factors to enhance the heat resistance of portland cement. This modification allows hydrates of the Na2O-CaO-SiO2-Al2O3-H2O hybrid system to be synthesized without undergoing structural destruction at high temperatures. The possibility of increasing the heat resistance of portland cements by using an aluminosilicate admixture of the fly ash type with the simultaneous use of sodium water glass has been proved. Methods of physico-chemical analysis revealed the peculiarities of the microstructure of alkali-activated FA-containing portland cements, such as the absence of portlandite Са(ОН)2 in hydration products as well as the synthesis of C-A-S-H phases of katoit and zeolite-like N-C-A-S-H phases of hydronepheline Na2O·Al2O3·2SiO2·2H2O and gismondine CaO·Al2O3·2SiO2·4H2O. Thus, heat resistance of such cement, in contrast to portland cement CEM I, was caused by the smooth course of structure formation processes at high temperatures with increased fragmentation by prevention of rehydration of СаО, formation of the high-temperature phase of gehlenite 2CaO·Al2O3·SiO2 by sintering of C-A-S-H phases, and recrystallization of zeolite-like phases into nepheline Na2O·Al2O3·2SiO2 and anorthite CaO·Al2O3·2SiO2 without structural destruction. These processes resulted in increasing the residual strength of the mortar based on proposed alkali-activated portland cement up to 41.6…90.6 % compared to 5…35 % of analogues based on CEM I. The optimized composition region of alkali-activated fly ash portland cement based on CEM IV/A 32.5N was determined: fly ash – 28...30 wt. %, density of water glass – 1150...1160 kg/m3. The proposed cement was characterized by residual strength ³ 70 % while increasing of compressive strength after 28 days of hardening ³ 50 MPa.
EXPERIMENTAL RESEARCH FIBER REINFORCED CONCRETE UNDER THE AN AGGRESSIVE ENVIRONMENT INFLUENCE
The initial costs of constructing concrete pavement for road surfaces are higher — approximately 70–80% more compared to asphalt pavement. However, after just 8 years of operation, the total expenses for both types of pavement become comparable. Cement concrete road pavements are among the most effective solutions for ensuring high load-bearing capacity, durability, and operational reliability of highways. The relevance of enhancing these characteristics is driven by the increasing traffic intensity, greater dynamic impacts, and rising axle loads from heavy-duty vehicles. A methodology research of materials which are used in highway building. Experience of application is presented hard highway coverage in the developed countries of Europe and USA. Expedience of fiberconcrete application is analysed in highway building at arranging of cement-concrete coverage and bases trouble-free reіnforcement. The combined use of steel and polymer fiber is a promising direction in construction, enabling the creation of durable, strong, and wear-resistant structures. Research in this field will help optimize the composition of fiber-reinforced concrete for various operating conditions. Fiber-reinforced concrete (FRC) demonstrates improved resistance to aggressive environmental impacts, such as chemical exposure, freeze-thaw cycles, and mechanical abrasion. However, prolonged contact with fuels, oils, de-icing salts, or acidic substances can still degrade the matrix and reduce the bonding efficiency between the fibers and the cement paste, especially if not properly protected or formulated.
INFLUENCE OF MODIFIERS AND POLYMER FIBER ON THE STRENGTH OF CONCRETE OF RIGID PAVEMENTS
he paper presents the results of comprehensive experimental research aimed at developing modified fiber concretes for use in rigid cement concrete road pavements. The main objective of the study was to investigate the effect of polymer fibers and a combination of chemical additives, including superplasticizer, air-entraining and colmatation additives, on the basic physical and mechanical properties of fiber concrete. The research methodology was based on experimental-statistical modeling using a symmetric four-factor model of experiments to systematically evaluate the influence and interaction of the selected components. The obtained data indicate that the inclusion of polymer fiber in the amount of up to 3 kg/m³ contributes to a significant increase in tensile strength in bending, reaching values up to 11.0 MPa, while having an insignificant effect on compressive strength. As a result of experimental studies, the optimal compositions of concrete mixtures were determined, providing an average density in the range of 2.3-2.4 g/cm³, water absorption of no more than 1.7% and compressive strength of more than 55 MPa. These parameters meet and exceed the requirements for high-strength road concretes. According to the experimental results, the developed modified fiber concretes can be recommended for use in the construction of road pavements of I and II categories, where increased mechanical characteristics and durability are important. The frost resistance and durability are planned for further study.
The optimal solution for door construction was selected. The article presents the options for door construction: solid wood, laminated doors and metal doors. The cost of materials for door installation and the calculation of capital investments in the base for construction works were made. The annual operating costs for door repair and renovation were determined. The calculation of the reduced costs is carried out, the conclusion and arguments for the choice of options for future projects are made.
PROPERTIES OF RECYCLED CONCRETE AGGREGATE AND THE POSSIBILITY OF THEIR APPLICATION IN ROAD CONSTRUCTION
У статті досліджено властивості матеріалів рециклінгу будівельних відходів (RCA-Recycled concrete aggregate) та їх потенційне застосування в дорожньому будівництві. В умовах сучасної концепції сталого розвитку, оптимізація використання ресурсів і зменшення впливу на довкілля є ключовими глобальними пріоритетами. Для України ці завдання стали ще актуальнішими через повномасштабну війну. Масштабні руйнування будівель, доріг та інфраструктури призвели до значного накопичення будівельних відходів, що створює як екологічні загрози, так і логістичні труднощі для процесу відновлення. Використання будівельного сміття як вторинної сировини відкриває нові можливості для ефективного управління відходами. Рециклінг таких матеріалів дає змогу не лише зменшити навантаження на навколишнє середовище, а й посилити потенціал для сталого відновлення. Дорожня інфраструктура відіграє вирішальну роль у забезпеченні мобільності, розвитку торгівлі та зв’язку громад — це один із фундаментальних елементів економічного відновлення України. У роботі проаналізовано характеристики матеріалів, отриманих із перероблених будівельних відходів, та оцінено їхню доцільність як альтернативи традиційним заповнювачам у дорожньому будівництві. За результатами дослідження встановлено, що одержаний після рециклінгу заповнювач має подібні до природного характеристики, зокрема насипну густину, вміст пилуватих і глинистих частинок, а також зерен пластинчастої і голчастої форми. Водночас він характеризується суттєво вищим (у 5–7 разів) водопоглинанням, що зумовлено наявністю на поверхні зерен налиплого розчину. Показано, що товщина цього розчину збільшується зі зменшенням розміру фракції, що негативно впливає на міцність заповнювача. Цей фактор є критичним при оцінці довговічності та ефективності використання RCA в дорожньому будівництві.
THE STUDY OF TECHNOLOGICAL PARAMETERS FOR THE INSTALLATION OF BORED PILES WITH AN ANTIFRICTION LAYER IN COMPLEX ENGINEERING-GEOLOGICAL CONDITIONS.
When installing bored piles in complex engineering-geological conditions, it is recommended to use antifriction materials in the contact zone between the pile and the surrounding soil. These materials reduce the impact of negative friction and help increase the load-bearing capacity of the piles. However, there is currently no clearly defined and scientifically substantiated technological scheme for installing bored piles with an antifriction coating in such soil conditions. Existing technological sequences for installing bored piles with antifriction coatings in complex engineering-geological conditions have a number of drawbacks: high labor intensity in applying the coating, difficulty in achieving a quality coating, and insufficient durability and operational reliability of bored piles for building foundations during the operational period. This can lead to premature failure of the coating layer and, consequently, a reduction in the load-bearing capacity of the pile during the building's service life. Additionally, there are challenges in the processes of lowering the reinforcement cage, joining the layers of antifriction coating, and ensuring proper contact between the pile body and the coating. Therefore, there are several directions for improving the technology of applying antifriction coatings on bored piles when constructing in complex engineering-geological conditions: improving the connection of the antifriction coating and enhancing its attachment to the concrete pile body. Improvements in the technological sequences for installing piles with antifriction coatings in similar engineering-geological conditions have been described, as well as methods for improving the application of the antifriction coating to provide stronger adhesion between the coating strips and the pile body. The result of such improvements is a more guaranteed service life of the antifriction coating on the bored pile and a reduction in negative friction between the coating and the pile body during the operation of the pile.
CHANGING THE STRENGTH OF CEMENT STONE BY THE INTRODUCTION OF ADDITIVES AND GROUND DOLOMIT
One of the effective ways to protect concrete structures from the effects of environmental factors is bulk hydrophobization. The most widespread and more studied are organosilicon substances, the disadvantage of which is a decrease in the initial strength of concrete. The paper presents the results of studies that confirm that the strength of cement stone with an admixture of GKZh-11K is carried out with the participation of the processes of activation of mineral dissolution and dispersion of the surface of cement particles due to the additional formation of H+ protons as a result of the dissociation of KOH. Potassium in bulk hydrophobization acts as an active alkaline center. Thus, the process of dissolving minerals of the dispersion of the surface of cement grains with hydrolysis and hydration can be attributed to pseudocatalysis because the main catalyst for the dissolution of the proton H+ does not regenerate. According to the results of the research, it was found that adding dolomite dispersions and GKZh-11K admixture to the cement dough in an amount of more than 0.2% of the cement mass activates the dissolution processes, which leads to an increase in the number of calcium hydrosilicate nanoparticles, the number of contacts per unit volume of cement stone, a decrease in pore size, and the formation of their closed nature, a decrease in shrinkage phenomena, and an increase in strength.
SUPER-STABLE CATIONIC BITUMEN EMULSIONS FOR COLD RECYCLING TECHNOLOGY OF PAVEMENT
The article presents the results of a study on the effect of a composite binder consisting of bitumen emulsion and Portland cement on the physical and mechanical properties of materials produced by cold recycling technology. It discusses the feasibility of using super-stable cationic bitumen emulsions for mixtures produced by this method. Super-stable cationic bitumen emulsions are defined as emulsions that exhibit high resistance to decomposition, low reactivity with the mineral components of the mixture or individual aggregates, and high storage stability. It was found that the compressive strength at 3 days in mixtures containing bitumen emulsion (at different dosages) was lower than in mixtures without it. However, by 7 days, the strength of the mixtures with emulsion surpassed that of those containing only the mineral binder. This trend continued after 28 days of curing. Thus, the cationic emulsion delays the initial hardening of the cement but does not reduce the final strength of the samples. Furthermore, the delayed heat of hydration can result in reduced shrinkage and improved crack resistance of the layer. The highest compressive strength at 20°C and 50°C, along with the lowest water absorption, were observed in samples containing Portland cement and 2% bitumen emulsion with the Redicote 4875 NPF emulsifier. This is expected, as this bitumen emulsion provides superior resistance to decomposition. In terms of bitumen emulsion dosage efficiency, all performance indicators were optimized when the emulsion content in the composite binder was at 2% by weight. Overall, the addition of bitumen emulsion slows the hardening of Portland cement, enabling longer transportation times for the mixture when produced "at the plant," and allowing for extended timeframes for laying, profiling, and compacting operations.
THE PHENOMENON OF MULTI-CENTRE STRUCTURE FORMATION OF BUILDING COMPOSITES
The article considers structure formation as a non-stop irreversible process. The main features of structure formation are present, which allows separating the concept of "structure formation" from the concept of "structure". The structure reflects the instantaneous state of the object, which makes it possible to conduct qualitative and quantitative analysis of the components. The lack of a history of the appearance of certain elements makes it impossible to predict further patterns of change over time. Structure formation proceeds from multi-center mechanisms on various structural heterogeneities. This leads to the spontaneous emergence of fundamentally different structural elements. These elements become dominant in further transformations of the structure, which violates the symmetry of evolutionary development. The spontaneous, continuous processes of structure formation themselves indicate that nothing happens in the system by itself. Thus, there is a kind of self-renewal of the system due to internal restructuring of the structural organization. Such processes violate causal changes and allow us to move on to the concept of development on the principle of "from what has been achieved." Structure formation requires not so much multidisciplinary methods of description as research of themselves. Comprehensive studies of the incessant processes of structure formation at different levels of heterogeneity will provide an opportunity to expand the horizons of knowledge about the mechanisms, phenomena and processes of self-development of the system as a whole. This will allow more direct determination of rational recipe and technological factors in the production of building materials, products and structures.
DESIGN AND METHODOLOGY OF RESOURCE-SAVING CONTINUOUS STEEL-CONCRETE SAMPLES SLABS EXPERIMENTAL TESTS FOR THE CONSTRUCTION OF CIVIL DEFENSE STRUCTURES
The problem of ensuring a uniform distribution of stresses in continuous steel-reinforced concrete slabs is relevant for modern construction. The use of self-stressing technologies can reduce the uneven distribution, but the issue of effective self-stressing in experimental samples of such slabs has not yet been sufficiently investigated. The paper presents design solutions and methods for the manufacture of experimentally tested samples of resource-saving non-cut three-span steel-reinforced concrete slabs that can be used for the construction of floors of civil defense structures. A two-stage technology for the manufacture of continuous steel-reinforced concrete slabs has been developed. It is proposed to create preliminary bends of the more deformed extreme spans by the slabs' own weight. The middle span should be concreted at the first stage, and the outer spans at the second. The paper describes the design features of manufacturing two samples of continuous three-span slabs 6 m long, made on fixed formwork from profiled flooring. The specimens differed in the lengths of the concreting grips, which made it possible to study the development of deflections in the extreme and middle spans due to changes in the stiffness of the section at the supports. The length of the concreting section is determined by the points of zero bending moments. During the first stage of concreting, the middle span of the steel structure bends downward due to the concrete mix's own weight, which causes the extreme sections that are not under load to bend upward. After the concrete of the first stage reaches the design strength, the concrete of the outer spans is concreted. At the same time, the extreme spans bend downward due to the weight of the concrete mixture, forcing the middle span, which already has a steel-reinforced concrete section, to bend upward. The paper presents the results of determining the physical and mechanical properties of the slab materials: concrete, steel rods of longitudinal reinforcement, and steel sheets of corrugated board of external reinforcement.
FORECASTING OF GREEN BUILDING PROJECTS IN TERMS OF USE OF TECHNICAL CROPS
The issue of the relevance of determining the economic profit from construction operations is being studied on an ongoing basis. The current present poses new production tasks. The concept of combining the organization of construction processes and the implementation of architectural forms makes developers and designers think. Global warming experts provide consulting services on leveling temperature effects throughout the year. Developers accept such services and adapt typical projects to modern climatic and sanitary and hygienic requirements for premises. The objectivity of data forms the need for competitive building projects. The presence or development of new binders in compounds of alkali metals, lithium, sodium, potassium, rubidium, cesium, on the basis of which alkaline and alkaline earth binders are formed. A special case of architectural combination is the use of technical crops for recreational tasks. Multitasking - growing food crops, the ability to organize new technological food processes and the use of plant parts on the roofs of buildings provides additional services for breeders and designers. Studying the conditions for the formation of green roofs of buildings for use as a recreational area adds new geometric and hygienic conditions for residents of such buildings. The use of amaranth on the roofs of high-rise buildings offers new opportunities for both building structures and representatives of small businesses for the organization of landscape patios on the roofs of buildings. This is a separate additional service for those wishing to relax, as well as for representatives of the spa industry for holding sports events. This adds tone to the residents of the house and additional income to local producers. The solution of the technological scheme of some energy-intensive and environmentally polluted processes of expanding the local cheap raw material base leads to savings in raw materials, fuel resources, electricity and preservation of environmental cleanliness. The cost-effectiveness of the technology lies in the progressiveness of operations and the overall sustainable effect of implementing energy-efficient green logistics chains.
DRY MIXTURES WITH ADDITIVES BASED ON POLYVINYL ACETATE DISPERSION AND QUICK LIME
The development of dry building mixes based on gypsum and time increase of time of their conformance through adding of complex additives on the basis of burnt lime and polyvinyl acetate dispersions [PVAD]. The study used standard research techniques to determine physical and mechanical properties of gypsum binders and quality of complex additives according to ДСТУ Б В.2.7-82-2010, ДСТУ Б В.2.7-23-95, ДСТУ Б В.2.7-171-2008. Study of phase composition of materials, micro – and macrostructure was carried out by x-ray diffraction, electron and light microscopy. The influence of the main components of the additive (polyvinyl acetate dispersion and lime) on the properties of hemihydrate gypsum is investigated. The chemistry of the interaction of components of the complex additive, according to which the result of alkaline hydrolysis of polyvinyl acetate is formed: polyvinyl alcohol, a feature of its molecules structure is the presence of hydrophilic OH− groups and the hydrophobic component − a hydrocarbon radical. The hydrophilic part of the molecule being ion adsorbed on the surface of the particles of the binder, forms a monomolecular layer that is oriented with the hydrophobic part of the gypsum particles. It is also possible the formation of calcium acetate Ca(СН3СОО)2, which increases the concentration of calcium ions in solution. The combined effect of hydrolysis products significantly reduce the solubility of hemihydrate, the rate of formation of crystallization centers, due to the slowing effect of these supplements. The results is theoretically substantiated and experimentally confirmed the possibility of obtaining a dry additive-retarder of gypsum setting based on lime and polyvinyl acetate dispersions due to the formation of polyvinyl alcohol and salts of calcium acetate in the result of alkaline hydrolysis of polyvinyl acetate dispersion (PVAD) with the slaked lime in hydrated lime. The results of the work implemented in the production of dry gypsum mixes.
ASSESSMENT OF THE BEARING CAPACITY OF REINFORCED CONCRETE CORBELS TAKING INTO ACCOUNT THE DEFORMATION CHARACTERISTICS OF CONCRETE
Modern methods of calculating reinforced concrete corbels under vertical load and potential opportunities for their improvement from the point of view of taking into account the deformation characteristics of materials are considered. The study demonstrates that commonly used models for assessing the resistance of reinforced concrete corbels are significantly simplified – both in terms of their geometric representation and in accounting for the deformation behavior of materials. The article analyzes the deformation characteristics of concretes of various strength classes, revealing potentially different failure mechanisms. Numerical simulations of corbel’s resistance are presented, including material nonlinearity and crack formation. These simulations reveal internal force trajectories that deviate from those predicted by conventional models and vary across different loading stages. The obtained trajectories are compared with those predicted by the Strut-and-Tie Model, which is widely applied in corbel’s resistance analysis. The paper highlights that current design standards recommend using a deformation-based model for reinforced concrete structures, which considers the complete compression and tension diagrams of concrete, the nonlinear behavior of reinforcement, and their combined deformation. However, the models currently in use do not account for the deformability of materials in any way. It is shown that, in addition to compressive strength, parameters such as the modulus of elasticity, tensile strength, and ultimate strains significantly impact the behavior of reinforced concrete corbels. The authors stress that conclusions regarding corbel’s resistance derived for one concrete class cannot be directly applied to structures made with concrete of a different class. This supports the need for further research into the influence of the deformation properties of both concrete and reinforcement when evaluating the bearing capacity of reinforced concrete corbels.
CALCULATION OF A CONCRETE WALL DAMAGED BY AN EXPLOSION FOR FRAGMENT PENETRATION ACCORDING TO THE UFC 3-340-02 METHODOLOGY
The article examines the evolution of building codes for designing structures resistant to blast effects in the United States and Europe. It analyzes the historical background that contributed to the development of modern standards, particularly UFC 3-340-02 and the Eurocodes. Special attention is given to the methodology for assessing damage to protective structures caused by fragments generated during explosions. An algorithm is presented for determining the required wall thickness to prevent perforation and spalling, taking into account the characteristics of explosive projectiles. The study offers recommendations for enhancing the design methodology of blast-resistant structures.
INNOVATIVE STRATEGIES FOR MANAGING CONSTRUCTION WASTE IN THE POST-WAR PERIOD
The article analyzes the multifaceted problem of managing construction waste in the context of eliminating the consequences of armed aggression in Ukraine. The armed conflict has resulted in the widespread destruction of real estate and critical infrastructure, thereby triggering a potential large-scale environmental crisis. In light of these developments, the study investigates the urgent need to reassess and modernize traditional waste management approaches by incorporating the principles of a circular economy at the state level. The scientific inquiry delves into both technological innovations and organizational strategies that can facilitate the implementation of efficient recycling systems. In doing so, it aims to optimize the planning processes within the construction market and to maximize the utilization of recycled materials during the restoration of infrastructure. Furthermore, the research examines in detail various methods for effective sorting, precise accounting, and systematic reduction of waste volumes that require safe disposal. It highlights how these methods can be integrated into existing waste management frameworks to mitigate the negative environmental impact. The analysis is supported by comparative studies of different recycling technologies and case studies from similar post-conflict scenarios in other regions, thus providing a comprehensive overview of potential solutions. The findings not only underscore the critical role of innovative waste management in preventing environmental degradation but also serve as a scientific basis for developing actionable recommendations. These recommendations aim to improve the efficiency and sustainability of construction waste management systems during the post-war reconstruction period, which is of paramount importance for ensuring the resilience and advancement of modern civil engineering practices.
ANALYTICAL REVIEW OF THE LITERATURE ON THE MASONRY COMPRESSIVE STRENGTH
Masonry is a traditional building material that is still actively used in modern civil and industrial construction. Determining its strength characteristics, in particular in compression, remains an urgent task, since it is the compressive forces that are the main ones in load-bearing walls, columns and other masonry elements. The strength of masonry is influenced by a large number of factors: stone strength, geometric dimensions, correct shape of the stone, the presence of voids in the stone, mortar strength, deformation characteristics of the hardened mortar, mobility of the mortar mixture, adhesion of the mortar to the stone, filling of joints with mortar, dressing of joints, quality of masonry. One of the main problems is the lack of a single approach to determining the geometric parameters of the samples used in testing. Available recommendations: for prisms, a height of at least 400 mm (from 5 to 6 rows of stone) is recommended; for brick pillars, the recommended length is at least 2 brick lengths, the height is at least 3 rows of masonry, the minimum thickness is one brick, in addition, the height of the test specimen should be within 3 to 15 of its thicknesses and be no less than its height. The purpose of this study is to formulate scientifically based recommendations regarding the shape and dimensions of standard specimens, which will allow the most reliable assessment of the compressive strength of masonry based on the test results. For this purpose, an analysis of existing studies, methods and regulatory provisions was carried out.
ENERGY-EFFICIENT CEMENT-SLAG MIXTURES FOR 3D-PRINTING
The article presents a set of experimental-static models of the properties of fine-grained concretes on a cement–slag binder and quartz sand with the addition of a hardening accelerator made on a 3D printer. The influence of the factors of the composition of the mixture and the effects of their interaction on the studied properties of concrete was established. By analyzing the models, the influence of the factors of mixture composition on the studied properties was ranked. The nature and degree of interrelation of individual properties of concrete are shown. The relationships between structural strength and setting time, as well as various strength indicators of concrete produced on a 3D printer, were established for different values of mixture composition factors. The use of a binder containing 30… 40% of ground-granulated blast-furnace slag and of hardening accelerator–sodium sulfate in the amount of 1…2% by weight of the binder allows obtaining energy-efficient mixtures suitable for 3D printing.
STRENGTH OF REINFORCED CONCRETE BEAM ELEMENTS IN INCLINED SECTIONS
The results of experimental studies of the beam reinforced concrete members strength in inclined sections to the action of shear forces when changing the relative shear spans in the interval 1.4 ≤ c/d ≤ 3.2 with different intensities of shear reinforcement are presented. 6 experimental beams of two series were tested using the “pure bending” scheme. The deformed state of the compressed zone of concrete in an inclined section near the point of force application and shear reinforcement crossing the crack was investigated at different loading levels using strain gauges. A significant increase in the plastic component of the relative strain of compressed concrete at the stages preceding failure and the achievement of the yield stress in the shear reinforcement has been established. The failure of beams occurs by shearing concrete above a dangerous inclined crack. The basis for improving the calculation of the ultimate strength of beam reinforced concrete members in areas near the supports behind a dangerous inclined crack when shearing concrete in the compressed zone, taking into account the combined work of concrete and shear reinforcement, has been determined. Based on the results of experimental and theoretical studies, the calculation parameters of the inclined section were determined, which require introduction into the dependence to determine the limiting value of strength. A relationship has been established between the parameters that determine the outline of a dangerous inclined crack: the height of the compressed zone near the crack tip, the angle of its inclination, and the projection of the crack onto the longitudinal axis of the beam element depending on the shear span.
INFLUENCE OF THE COMPOSITION OF REACTIVE POWDER ALKALINE-ACTIVATED SLAG PORTLAND CEMENT CONCRETE ON THE EVOLUTION OF ITS PROPERTIES
The influence of the composition of alkali-activated reactive powder concretes (RPC) and other factors on the genesis of their properties is established. It was shown that an increase in the binder content in the composition caused an increase in strength, and the dependence of strength on the sand content at all stages of hardening is almost direct at water-cement ratio £ 0.35. Optimization of sand granulometry allowed to improve the rheological properties of the mixture and to increase the strength by 5...6%. The effect of increasing the OPC within 5...45% in the mixture with ground granulated blast furnace slag (GGBFS) on the strength of RPC is ambiguous - in the early stages (up to 3 days) it causes an acceleration of strength gain, but in the long term, composition with 5% OPC and 95% GGBFS has the highest strength. Shrinkage deformations decrease with an increase of OPC/GGBFS ratio and part of fine aggregate. The introduction of an optimal amount of dispersed calcite additive allows to reduce the shrinkage deformations. The admixtures allow regulating the initial setting times within 19...118 min. The performed work resulted in obtaining high-strength, ultra-rapid-hardening, alkali-activated cement reactive powder concrete of strength class C80/95 with high early strength (52.3 MPa at 1 d; 76.3 MPa at 2 d; 85.0 MPa at 3 d), high crack resistance (compressive strength / flexural strength ratio = 5.3…5.9), reduced shrinkage (0.5…0.6 mm/m), stable performances, and technologically acceptable setting times. In terms of early strength gain, the designed ultra-rapid-hardening RPC significantly surpasses concretes based on alumina cement, super-rapid-hardening portland cement and low-water-demand cement, while having acceptable shrinkage. Considering the high physical, mechanical, operational and special characteristics, the obtained RPC can be classified as high performance concrete.
INFLUENCE OF BUILDING MATERIALS ON THE THERMAL INERTIA OF BUILDING CONSTRUCTION
One of the important, but insufficiently studied factors affecting energy efficiency is the thermal inertia of building envelopes. Recent studies confirm the key role of thermal inertia in increasing the energy efficiency of buildings, especially in a changing climate and increasing demands for sustainable construction. This paper examines various building materials from the point of view of their inertial properties. Insufficient consideration of thermal inertia can lead to inefficient use of passive heating or cooling, and energy overconsumption by heating, ventilation and air conditioning systems. Particular attention is paid to the use of thermal insulation and structural materials in building walls. The purpose of this paper is to conduct a comparative analysis of thermal insulation and wall building materials to identify their impact on the thermal inertia of building envelopes. To analyze the thermophysical characteristics of the main thermal insulation and structural materials used in building envelopes. The obtained data allow us to state that the thermal inertia of the structure is largely determined by the physical properties of the structural layer (wall materials), primarily its density and specific heat capacity. To ensure a comfortable microclimate in the premises, it is advisable to use wall materials with high thermal inertia. The obtained results can serve as the basis for modeling temperature changes in walls with different material options for a more accurate assessment of their real energy efficiency.
EFFECT OF WETTING OF COARSE AGGREGATES ON THE PROPERTIES OF CEMENT CONCRETE
The article analyzes the literature on the effect of filler wetting on the processes of structure formation and physical and mechanical properties of concrete. It is shown that the weakest element of the concrete structure is the interphase transit zone (ITZ) between the hardened cement stone and the filler. The quality of this zone largely depends from the wetting of fillers with water or aqueous solutions of chemical additives. It is known that the wetting efficiency is affected by the quality of the filler surface, its porosity and W/C. However, there is no correlation between the wetting of the filler surface and the strength and durability of concrete. There are also no data on the effect of the mineral composition of fillers and the type of wetting liquid on the nature of wetting. Therefore, the article presents the experimental results of determining the contact angle of wetting of fillers by different mineral composition with water and aqueous solutions with superplasticizers of different concentrations. In addition, the wettability of fillers with cement - water suspensions of different concentrations with and without superplasticizers was studied. One of the criteria for good wetting of aggregates is the formation of high-quality ITZ. This leads to an increase in the strength of concrete. The article presents data on the effect of the wetting angle of aggregates on the strength of concrete. The relationship between wetting and mixing time of concrete mixture is established. This allowed us to establish that by improving wetting, the time of concrete mix preparation can be reduced. The conducted studies showed that in order to increase the strength of concrete and the efficiency of its preparation technology, it is necessary to select a specific type of wetting liquid for each type of filler.
PERMANENT FEATURES OF WATER SUPPLY FOR GREEN CROPS
The issue of water treatment is becoming more relevant as the cost of basic technological processes increases. The search for new opportunities requires changes in technology, products and organizational approaches to production. Processing statistics of old production facilities, new trends in greening production facilities, development of new products and by-products pose new challenges to the economic components of the cost of products. New research in the field of water treatment, new equipment leads to anti-crisis solutions in the field of water supply. The critical infrastructure of municipalities aims to provide reliable and safe water to city residents and industrial enterprises. The generation of new areas of research and materials, which is seen by new clients and residents of smart cities, leads to innovative solutions of universities and startups based on laboratories. The tasks of increasing the capacity of small flows with the existing good quality of surface water force researchers to look for alternative options for water resource sources. When conducting research, it is important to keep in mind the issues of sustainable development and differentiation of new products. The coordination of the issue of certification of new products becomes the next test for local manufacturers aiming to develop technologies. The development of new filter materials, even from man-made raw materials, requires the calculation of a hypothetical material balance of salts to prove the concepts.
DEVELOPMENT OF CONCRETE MIXTURES BASED ON AGGREGATES FROM DIFFERENT REGIONS OF UKRAINE TO PRODUCE HARDENED CONCRETE OF THE SAME STRENGTH CLASS
The use of regional aggregates reduces logistics costs and increases the profitability of construction work, but requires an individual approach to the design of concrete mixtures. The article presents the results of designing the composition of concrete mixtures using aggregates from four different regions of Ukraine using carboxyl-containing polymers as modifiers. The main purpose of the study was to ensure the same mobility of mixtures and strength class of hardened concrete stone, taking into account the characteristics of regional ingredients, namely local fine aggregate. The coarse aggregate chosen as a constant was crushed stone from igneous and sedimentary rocks, fraction 5-20, and binder (Portland cement) CEM II/A-LL 42.5 R. The experimental part involved the selection of the recipe, in particular the optimal dose of the modifying additive for each composition of the concrete mix. In general, the composition of concrete mixtures was determined by the calculation and experimental method with the preliminary application of the absolute volume method and further refinement of the recipe based on trial batches, which made it possible to optimize the content of components taking into account the actual properties of materials and ensure compliance with design requirements. The main physical and mechanical characteristics of concrete mixtures were determined, including fresh mobility and hardened concrete strength. Tests have shown that all developed concrete mixtures compositions correspond to mobility class S4, and hardened concrete corresponds to strength class C32/40 with a certain margin, which confirms the effectiveness of the proposed design approach. It was found that the optimal dosage of the carboxyl-containing modifier required to achieve this goal significantly depends on the properties of the regional components of the mixture. The results confirm the need for an individual approach to designing the composition of concrete mixtures, even with the same requirements for their performance.
DETERMINATION OF DEFLECTIONS OF U-SHAPED REINFORCED CONCRETE FRAMES
This paper presents a methodology for calculating the deflections of reinforced concrete u-shaped frames designed according to the second group of limit states, based on the consideration of deformation characteristics of the material and external loading conditions. The deflections in u-shaped frames primarily depend on bending deformations, which can be determined by calculating the curvature. The curvature of the element is expressed through a formula that accounts for the impact of cracks on the stiffness of the material. The proposed algorithm includes several stages for determining the curvature in the "crack-free" and "cracked" states. These stages involve the calculation of the cracking moment, the internal stresses in the reinforcement, and the deformations in the concrete under tension and compression. The methodology focuses on calculating the height of the compressed concrete zone, which is essential for ensuring the internal force equilibrium in the cross-section. The algorithm also involves an iterative process for refining the values of internal stresses and bending moments, ensuring accurate prediction of u-shaped frames deflections. The importance of determining the stiffness reduction factor, which accounts for the loss of stiffness due to cracks and material deformations, is emphasized in the paper. Additionally, the paper explores the effect of loading duration and repeated loads on the average deformation behavior of the u-shaped frame. The methodology is based on the assumption of plane cross-sections and incorporates the use of polynomials to represent the stress-strain relationships for concrete in both tension and compression. The calculation procedure involves determining the initial deformation in the concrete, calculating the stresses in the reinforcement, and then calculating the cracking moment, followed by the deflection calculation using the generalized curvature. The method also accounts for external loading conditions, including both short-term and long-term loads, by considering the influence of repeated load cycles and the duration of loading on the material’s behavior. The paper provides a detailed explanation of how to use these methods in practical applications, including the necessary formulas and steps for accurate deflection predictions. The proposed methodology ensures the reliable design of reinforced concrete structures, taking into account all relevant factors such as material properties, structural dimensions, and loading conditions. The calculations are consistent with modern standards, such as Eurocode, and can be applied to various types of reinforced concrete structures.
FEATURES OF THE WATER ABSORPTION PROCESS OF THERMALLY MODIFIED WOOD
The paper analyzes the process of thermal modification of wood obtained by a controlled pyrolysis process of heating wood (> 180 °C), which causes some chemical changes in the structures of cell wall components (lignin, cellulose, and hemicellulose) in order to increase its durability. It has been proven that the thermal modification process causes the breakdown of hemicelluloses and the amorphous part of cellulose, reduces water absorption, and reduces the amount of substances that are a breeding ground for fungi. In addition, lignin and the resulting pseudolignin undergo polymerization and redistribution throughout the cell volume, giving the cell walls greater density, hardness, and increased hydrophobicity (water repulsion), thereby reducing their ability to absorb moisture and swell. The polymerized lignin fills the internal cavity of the cell, forming a closed porous structure with a low ability to bind water. It has been established that the most effective parameter for reducing such substances is temperature and exposure time. The results of water absorption are presented, and a dependence is determined on the basis of which the diffusion coefficient for water absorption is calculated. During the thermal modification of wood for 6 hours, water absorption decreases by more than 10 times, which makes it possible to use it in objects with high humidity.
INFLUENCE OF SIC-MICRO AND SIC-NANO ADDITIVES ON THE MINERAL BINDER HYDRATION PROCESSES
One of the modern approaches to the mineral binder property improvement is the nanomodification problem solving based on a comprehensive approach to changing the material’s structure. The core idea involves the introduction of nanostructured elements and the use of surfactants (surface-active agents), which makes it possible to significantly enhance the physical and mechanical properties of the final material or even impart new, unique characteristics to it. This approach enables the hydration optimization and structure formation processes, opening up broad perspectives for the practical application of such modified binders. Nanoparticles, acting at the early stages of hydration, may change the gypsum crystallization morphology, regulate the crystal size and shape, and thereby directly influence the artificial stone structure, density, strength, and durability. Purpose of the study: to identify the patterns of the gypsum binder structure formation mechanisms and to improve their physical and mechanical properties through the introduction of modifying nanoadditives and surfactants. Currently, there are very few scientific studies dedicated to examining the combined influence of surfactants and nanomodifiers on the hydration processes and material structure, which highlights the relevance of further research in this field. The study discovers the impact of key factors on the hardening and structure formation processes of gypsum binders,determines the correlation between the additive nanoscale characteristics and the final material microstructural properties and proposes a theoretical model that explains the observed effects. All of this enables targeted control over the modification processes and the development of a new generation of materials with enhanced performance characteristics.
IMPACT OF LOCAL DESTRUCTION OF THE LOAD-BEARING WALL OF THE FIRST FLOOR ON THE BUILDING STRUCTURE
The article analyzes a specific case of an emergency condition in a five-story residential brick building in the city of Lviv, constructed according to a classical structural scheme with transverse and longitudinal load-bearing brick walls and wooden floor structures. The primary focus is on the consequences of mechanical intervention into the load-bearing structures carried out without appropriate design documentation and technical supervision. The study is of an applied nature and is based on the results of a comprehensive technical inspection. According to the inspection data, a loss of load-bearing capacity was recorded in the wall along axis 1 (between axes H–D), with a vertical crack up to 70 mm wide that splits the wall in half. In the same area, a window opening was discovered, which was not included in the official BTI (Bureau of Technical Inventory) plans and is likely the key factor that triggered the emergency condition. Other identified defects include cracks in exterior and interior walls, particularly along chimney flues; settlement and displacement of floor structures; biological degradation of wooden beams; moisture penetration in walls and roof; corrosion of metal balcony elements; deformation of stair flights; and cracks at the junction with an adjacent building. This combination of defects indicates comprehensive degradation of the building’s structural elements. Based on the collected data, the authors proposed urgent temporary reinforcement measures, some of which were implemented during the inspection. These measures included the installation of external metal braces, internal metal supports with wooden beams transferring loads to the floor, and reinforcement of the damaged wall area from both sides. Further interventions must be carried out strictly in accordance with the structural reinforcement design documentation. The article not only illustrates the importance of regular technical monitoring of older buildings but also demonstrates the necessity of complying with regulatory requirements during remodeling or structural interventions. Furthermore, it emphasizes the importance and necessity of developing a systematic approach to housing stock management that includes periodic inspections, risk assessments, and regulated interventions
COMPREHENSIVE ASSESSMENT OF THE TECHNICAL CONDITION AND GEOMETRIC PARAMETERS OF AN INDUSTRIAL CHIMNEY USING LASER SCANNING TECHNOLOGY
The article presents the results of a comprehensive survey of the technical condition of a reinforced concrete chimney of an industrial enterprise. The scientific and practical task was to determine deviations of the geometric parameters of the structure from the design values and to identify defects in the structure using laser scanning technology. The methodology of laser scanning, including a description of the equipment, scanning parameters, and data processing methods, is described in detail. The results indicate the presence of significant deviations from the vertical and defects, which allows us to conclude that the chimney is in unsatisfactory technical condition and requires repair or dismantling. The use of laser scanning technology made it possible to obtain objective data on the geometric parameters of the chimney and to more accurately assess its technical condition. The findings can be used for making informed decisions on the future operation of the chimney, developing repair projects or dismantling, as well as for improving methods of surveying and monitoring industrial structures. The laser scanning technology is an effective tool for the survey of industrial chimneys, allowing to quickly and accurately obtain information about their geometric parameters, identify defects and assess the technical condition, improving the objectivity and efficiency of the survey and reducing risks to staff. The detailed analysis of the technical condition of the chimney can be used to improve the safety and reliability of industrial enterprises.
HEAT AND SOUND INSULATION MATERIALS AND PRODUCTS BASED ON MODIFIED BASALT FIBER
The current level of development of the industrial production of thermal and sound insulation products based on continuous fibers implies: reduced energy and raw material costs, increased environmental safety of technological processes for the production of fibers and products based on them, increased reliability and durability of products, as well as increased chemical stability. Basalt is a natural material that is environmentally friendly, does not emit harmful substances when melted and is easy to recycle, and the combination of properties such as chemical resistance, high temperature stability and mechanical strength makes basalt fibers compete with more expensive glass fibers in the production of harnesses and products for various functional purposes based on them. Therefore, the use of basalt fibers in the production of heat and sound insulation products provides a secondary environmental effect compared to the products currently used, which reduces the risk of environmental pollution by highly toxic metals and their oxides, which are part of the charge for the production of conventional mineral and borosilicate glasses. The relevance of research in this area is highlighted in the works performed in leading research laboratories and at modern industrial enterprises. The problems of the use of basalt fibers in building materials are discussed in the works of Dzhigiris D.D., Makhova M.F., Aslanova M.S., Mohort M.A., Gotz V.I., Walz A., Mayer M., which emphasize the need to ensure the conditions and control the processes of basalt fiber structure formation to obtain heat and sound insulation products with improved performance properties. However, with increasing requirements for heat and sound insulation products, the requirements for fiber properties increase, which requires improvement of its structure. According to the data in the literature, this can be done both by modifying the melt and by processing the fiber before its use
COMPARATIVE ANALYSIS OF THE APPLICATION OF STRESS-STRAIN RELATIONSHIPS PROVIDED IN DBN V.2.6-98:2009.
The article presents the results of a comparative analysis of concrete stress-strain diagrams based on the functional mathematical dependencies provided in DBN V.2.6-98:2009 ([1], (3.4), (3.5)). The obtained results indicate minor discrepancies between the graphs derived from these dependencies, which suggests the equal applicability of both for the design of reinforced concrete structures according to the limit state method. The relevance of this study is due to the necessity of clarifying methodological approaches to the use of the specified normative provisions in the design of concrete and reinforced concrete structures. This research is particularly significant for the design of civil protection shelters, where precise calculations are critical for ensuring structural reliability. The findings contribute to enhancing the safety and durability of such concrete structures under extreme conditions.
ENGINEERING AND GEOLOGICAL FEATURES OF WORKS IN THE CONSTRUCTION OF TRANSPORT FACILITIES.
A comparison of the reliability of mathematical modelling results of the heat treatment plate systems by moving heating sources is made. An approach to determining the amount of thermal energy redistributed in the welding plate due to local thermal effects is proposed. Increasing requirements for the strength and durability of the relevant nodes and elements of welded structures, as well as the problem of saving metal and energy in the context of the transition to resource- and energy-saving technologies, determines the urgency of the task of determining the optimal parameters of low-temperature processing technology using moving sources and heat sinks. The continuous increase in the volume of welding work in industry and construction is inextricably linked with the development of ways to minimize residual stresses and deformations and their harmful effects on the quality and performance of welded structures. The analysis of known literary sources indicates insufficient study of the process of heat treatment using moving zones of heating and accompanying cooling and taking into account elastic-plastic deformations, since this is associated with great difficulties of a mathematical nature associated with the mobility of thermal effects, the emergence of purely elastic zones , elastic-plastic and purely plastic deformations. The possibility of solving such problems is performed by numerical methods, namely: the method of finite differences, the method of finite elements, and the method of boundary integral equations. Analytical methods that make it possible to construct solutions of such problems in a closed form can be used in calculations only under the condition of significant simplifications of the description of the deformation process, which introduces errors in establishing the real picture of the development of elastic-plastic deformations.
RATIONAL AREA OF USE OF GRANITE CRUSHED STONE FROM MYKYTIVSKY AND SOFIIVSKY DEPOSITS IN ROAD CONSTRUCTION
The article presents the results of testing crushed stone from the Mykytivsky and Sofiivsky quarries of the Mykolaiv region. A comparative analysis of the physical and mechanical characteristics of the samples was carried out, the main differences in the composition and strength of the rocks of these quarries were determined. The research results allowed us to draw conclusions about the feasibility of using materials from each deposit in road construction. The results of the work will optimize the choice of building materials, which will contribute to increasing the efficiency of their use. This is especially important for road design, where it is necessary to take into account not only the initial properties of the material, but also their stability during operation. Along with this, the construction industry, in particular in road construction, is in dire need of high-quality materials. The use of high-quality materials in the base layers of the road pavement allows to increase the service life of not only the pavement layers, but also the road pavement as a whole. Mykytivsky and Sofiivsky deposits are important sources of building materials widely used in road construction and concrete production. The purpose of this study is to compare the physical and mechanical characteristics of materials from the Mykytivsky and Sofiivsky quarries to determine their optimal scope of application in aggregate-sand mixtures. The study will help optimize the use of materials from natural deposits in the construction industry and will improve the efficiency of choosing raw materials for specific engineering tasks in the design and construction of road
INFLUENCE OF THE TYPE OF FINITE ELEMENTS ON THE RESULTS OF DYNAMIC ANALYSIS OF A BRIDGE SPAN
Increasing traffic volumes, increasing weight and speed of vehicles, as well as trends in modern bridge construction towards the use of new materials and lightweight structures increase the sensitivity of bridges to dynamic impacts and make traditional static calculations using a dynamic coefficient insufficient. A key aspect of ensuring reliability and durability is the accurate determination of dynamic characteristics, in particular natural frequencies and vibration forms, to prevent dangerous resonance phenomena. The purpose of this paper is to study the natural vibrations of a typical reinforced concrete road bridge span structure using the finite element method (FEM) and to compare the results obtained using different approaches to finite element modeling. The study was carried out in the LIRA-FEM software package by performing a modal analysis. Two objects are considered: a single reinforced concrete beam of a 24 m long span structure and a complete bridge span structure of the same length, consisting of five beams connected by a monolithic slab. Two computational models were created for each object: the first one using a combination of universal spatial rod and plate finite elements; the second one using universal spatial volumetric (eight-node isoparametric) finite elements. The first three shapes and their corresponding frequencies of natural oscillations are determined. The analysis of the results for an isolated beam showed a relatively small difference in the values of natural frequencies between the rod and volume models, which indicates the acceptability of using simpler models for individual beam elements. However, for the complete span structure, significant differences in frequencies between the two modeling approaches were found. This demonstrates the critical importance of choosing an adequate type of finite element to accurately model the dynamic behavior of complex spatial systems. The results confirm the effectiveness of FEM for the dynamic analysis of bridges and emphasize the need for a careful approach to the creation of computational models.
EFFECTIVENESS OF CURING CATALYST ADDITIVES ON FORMING THE PROPERTIES OF POWDER COATINGS
The article presents the results of experimental studies on the influence of various curing catalysts on the physico-mechanical properties of powder coatings under reduced curing conditions. The study investigated three catalysts: tetradonium bromide (DT 3126-4), triphenylethylphosphonium bromide (ADDITOL® P 964), and a carboxyl-terminated polyester oligomer (JG804A), each introduced into the system at a concentration of 0.6%. Key performance indicators such as impact resistance, flow properties, bending strength, and adhesion were evaluated according to relevant ISO standards. The most effective catalyst was DT 3126-4, which ensured high-quality polymerization even at a curing temperature of 120 °C. The study concludes with recommendations regarding the suitability of each catalyst depending on operational conditions and technological requirements. The results may be applied to the optimization of powder coating formulations with enhanced performance characteristics under energy-saving curing regimes.
THE CONCRETING TECHNOLOGY OF RAPID-HARDENING CONCRETE
У статті розглянуті технологічні питання застосування швидкотверднучих бетонів у будівництві. Проведений аналіз роботи опалубочних систем та розглянуті терміни розпалубки виробів з використанням швидкотверднучих бетонів. Розглянуті основні типи опалубочних систем при зведенні обєктів промислового та цивільного призначення. Розглянуті особливості ущільнення бетонних швидкотверднучих сумішей. Наведені основні види вібрування. Розглянуті технологічні особливості догляду за бетоном із швидкотверднучих сумішей. За результатами аналізу зроблений висновок про ефективність впровадження наведених технологічних аспектів застосування швидкотверднучих бетонів у будівництві.
STUDY OF THE INFLUENCE OF MINERAL COMPONENTS ON THE PROPERTIES OF ROAD HYDRAULIC BINDERS
The development of modern road construction requires the continual improvement of materials that ensure high quality, durability, and reliability of pavements. A key role in this process is played by road hydraulic binders, which are used for constructing road bases and pavements due to their ability to harden and maintain strength under demanding operating conditions. In response to current challenges in transport infrastructure, increasing attention is being paid to roller-compacted concrete (RCC), driven by rising costs of bituminous binders and the widespread availability of asphalt paving equipment that can be adapted for RCC placement. This study explores the potential of using various mineral components —natural and synthetic zeolites, metakaolin, limestone, coal slag waste, and calcined sunflower ash—as partial substitutes for Portland cement in hydraulic binders. These materials were incorporated in varying proportions, and their effects on setting time, volume stability, and compressive strength were evaluated. The mineral additives, compliant with EN 13282-2:2021, significantly influenced hydration processes and microstructure development, especially under low water-to-cement ratios. Among the tested components, metakaolin, natural zeolite, and calcined sunflower ash (at up to 10 wt.% cement replacement) demonstrated the most promising results, contributing to enhanced early and final strength. The use of such mineral additives not only improves the performance characteristics of binders but also supports the principles of circular economy by recycling industrial by-products and reducing environmental impact. The findings highlight the viability of integrating sustainable materials into road construction to achieve both technical efficiency and environmental responsibility.
ANALYSIS OF FACTORS THAT INFLUENCE THE COMPLEXITY OF ENGINEERING SERVICES
The article analyzes state and foreign regulatory documents regarding the presence of requirements for taking into account the influence of complicating factors when organizing engineering services during the construction of architectural objects. It has been established that the specifics of the construction site, technological complexity, geographical conditions, regulatory environment, social and environmental requirements, as well as financial, personnel and organizational constraints directly affect the efficiency of engineering processes. Taking into account complicating factors when organizing engineering services is not only advisable, but also critically necessary to ensure their effectiveness. Ignoring such factors as the specificity of the facility, regulatory environment, geographical conditions, technological complexity and socio-ecological risks leads to quality losses, increased costs and increased risk of accidents. Foreign experience convincingly demonstrates that a systematic approach to identifying and integrating these factors into contractual, technical, and management decisions allows not only to minimize risks, but also to increase the responsibility of construction participants, the transparency of processes, and trust in results. Therefore, institutionalizing the consideration of complicating factors should become a mandatory element of both public and private sector policies in the field of civil engineering.
RENEWAL OF THE DESTROYED EDUCATIONAL BUILDING OF THE NATIONAL UNIVERSITY "ODESSA POLYTECHNIC"
Abstract The results of the inspection of the technical condition of the roof of the building of the Institute of Electromechanics and Energy Management of the Odesa Polytechnic National University are presented. The building was destroyed as a result of the hostilities of the russian aggressor. The main defects and damage to the building's roof elements are analyzed. Their final bearing capacity is established using information technology methods and recommendations are provided for eliminating damage and restoring the roof. In connection with the unauthorized full-scale invasion of the russian aggressor into the territory of Ukraine, massive missile technology and unmanned aerial vehicles are constantly being used. This has led to the destruction of vital transport, energy infrastructure, educational, public and residential buildings. Therefore, the problem of providing means of protection for the city of Odessa and its population, the restoration of destroyed buildings and structures is urgent. The authors present studies of the wooden roof of the building and the roof destroyed as a result of the impact of the rocket shock wave on the basis of current regulatory documents of Ukraine, methods of analysis of scientific, library, archival and other sources. Materials for calculating the roof truss system using modern software and information technologies are provided. Ways of restoring the roof of the building of the Institute of Electromechanics and Energy Management are proposed.
EVALUATION OF THE QUALITY OF AGGREGATES AND WATER-CEMENT RATIO INFLUENCE ON THE RELATIVE DEFORMATION OF HEAVY CONCRETE
The article considers the principle of evaluating the dependence of relative deformations of heavy concrete at different water-cement ratios and aggregate quality, which will allow for a better assessment of the bearing capacity of concrete and reinforced concrete structures. It has been established that with an increase in the water-cement ratio, a clear increase in the relative deformation characteristics of concrete is observed. The use of high-quality fillers increases the relative deformation index compared to medium and low-quality fillers.
SCHEMES OF CONNECTION OF RAIN GARDENS TO DRAINAGE NETWORKS
Based on existing technologies for accumulation, temporary retention, and filtering of surface runoff, 3 schemes for connecting rain gardens to storm sewer networks are proposed and the shapes of hydrographs for a specific scheme are substantiated. According to scheme № 1, the entire volume of rainwater with a flow rate Qд enters the rain garden. This scheme is used in cases where the rainwater is conditionally clean, for example, runoff from the surface of roofs, from improved surfaces on which there is no traffic and there are no other sources of pollution. For this scheme, the inflow of rainwater to the rain garden Qen coincides with the hydrograph of rainwater: Qen=Qд. According to scheme № 2, the polluted part of the runoff with a flow rate Qоч enters the facility's drainage system or directly to the treatment facilities, and the conditionally clean runoff with a flow rate Qen enters the rain garden. In this case, the overflow flow rate Qпер can be discharged back into the network or into the nearest ravine, depression, etc. Accordingly, for this scheme, the inflow of rainwater to the rain garden is: – at Qд<Qоч: Qen =0; – at Qд >Qоч: Qen =Qд–Qоч. where Qоч – treatment flow, i.e. the flow of contaminated wastewater that requires treatment. According to scheme № 3, the polluted part of the runoff from the runoff basin first goes to local treatment facilities, and then is fed into the rain garden. The advantage of this scheme is the possibility of installing an autonomous surface drainage system. This scheme also allows for the fullest use of the rain garden's post-treatment function without the risk of groundwater contamination and without clogging of the garden's filtration and drainage loading. For this scheme, the inflow of rainwater to the rain garden is: – at Qд<Qоч: Qen =Qд ; – at Qд> Qоч: Qen =Qоч. Compared to scheme No. 1, schemes No. 2 and No. 3, under the same conditions, have smaller calculated areas of the filter bed.
EFFICIENCY OF THE CONCRETE WASTE DISPERSED FRACTION ACTIVATION AS AN MINERAL ADDITIVE FOR PORTLAND CEMENT
The article presents experimental results on the feasibility of using crushed concrete waste (dispersed particles smaller than 1 mm remaining after sieving out coarser fractions intended for use as recycled aggregate) as a complete or partial replacement for ground granulated blast furnace slag in the production of Portland cement. Experimental studies have shown that the introduction of concrete waste without additional activation may lead to a reduction in the standard compressive strength of Portland cement. Activation of the dispersed fraction of concrete waste is achieved by increasing its fineness, the combined use of active mineral additives, and alkali-fluoride salts. A full range of standard tests was conducted on the resulting cements, including determination of granulometric characteristics, chemical composition, water demand, setting times, compressive strength, and activity index. It was shown that the composition of concrete waste, particularly the content of cement paste and calcium hydroxide formed as a result of the hydrolysis during clinker minerals hydration, plays an important role. The significance of the content of cement paste and calcium hydroxide in the dispersed fraction of concrete waste formed during hydration was confirmed. The application of activation measures in the introduction of 15% of the dispersed fraction of concrete waste in combination with blast furnace slag made it possible to obtain Portland cement that meets standard performance requirements.
INFLUENCE OF PROLONGED MOISTURE ON THE DESTRUCTIVE CHARACTERISTICS OF HEAVY CONCRETE
The description of the occurrence of changes in the stress-strain state of concrete and its physico-mechanical properties under the action of short-term loading directly depends on the duration of its wetting with water, i.e. on the changes in the internal stress state caused by this phenomenon, along with the action of the absorption wedging action of water in the defects and pores of the concrete structure and the excess pressure in these pores. It was found that simultaneously with these processes, the destruction of some and the creation of other physico-mechanical and physico-chemical bonds between the solution and the aggregate, the solution and water. Only the chemical bonds remain unchanged. This leads to a change in the properties of the capillary-porous body of concrete. During this period of load application, continuous compaction of concrete occurs to the lower limit of longitudinal microcrack formation. Subsequently, with increasing compressive loads, the moistened concrete undergoes decompression, its volume begins to increase and at a certain level reaches the initial values. This level corresponds to the upper limit of longitudinal microcrack formation and development. With further increase in load, microcracks in concrete also grow and a critical level of microcrack development is reached, which, merging, create a macrocrack. It has been established that with prolonged moistening of heavy concrete for 2-4 days, the strength decreases to 27% of the initial one with subsequent recovery to 40-60 days of moistening, and subsequently exceeds the initial one. Destructive coefficients , , showing physical and mechanical changes in the internal structural state of heavy concrete also change, repeating to one degree or another the change in the strength of concrete from the action of prolonged moistening.
CONSTRUCTIVE SOLUTIONS FOR REINFORCED CONCRETE pile-strip foundation UNDER THE WALLS OF BUILDINGS.
Under the walls of buildings, strip foundations of shallow laying are most often used, and in some cases, pile foundations are also used. A rather important and positive feature of pile-strip foundations is that they are reliable in transferring the vertical load from the walls to the base soil. The reliability of these foundations is due to their high bearing capacity, as well as small deformations, because they, as a rule, penetrate the lower ends of the piles into the dense soils of the base and transfer the majority of the load to them. However, the field of use of pile foundations in modern construction is limited by their rather high cost. That is why an urgent issue when using strip pile foundations is to reduce their cost to the value of shallow foundations on a natural basis. In this case, the reliability of pile foundations combined with a low cost will make it possible to expand the scope of their application, and the consequence of this will be an increase in the industrialization of zero-cycle works, a reduction in the amount of manual labor, and the convenience of execution in adverse climatic conditions. The main directions for achieving the specified tasks are a more complete use of the capabilities of the base soils to accept the load from strip pile foundations, as well as optimization of the design solutions of these foundations and their foundations. It should be noted that the load absorption from the foundations involves mainly the soils into which the lower ends of the piles enter, and the upper part of the soil stratum within the inter-pile space is almost not involved in this process. In order to use the upper part of the space between the piles to absorb the vertical load, it is proposed to use a low grid in the process of transferring pressure to these soils. In modern construction practice, the possibility of transferring part of the vertical load through the low grid of the strip pile foundation is not taken into account.
ROLE OF FIBER IN THE ORGANIZATION OF THE STRUCTURE OF MATERIAL ON THE LEVEL OF PRODUCTS
The article proposes to consider architectural products in the form of decorative material decorated in certain geometric frames. In order to obtain an operational-reliable material for products of complex shape, it is proposed to use reinforcement of the composite structure. Previous studies on the nature of the influence of fiber on the processes of organization of structures at the micro level of the material showed an active, peculiar and unique role of linear elements. The results of structural parameters of cement compositions presented in this paper are a continuation of previous studies. For the study of structural parameters, models of decorative elements of various shapes are taken as objects. Models were made on the basis of water-clays, water-cement and epoxy compositions. To assess the effect of linear elements, fiber of different lengths and hybrid mixtures were used. When conducting experiments on models, the change in volume mass over time, relative shrinkage, material’ damage through to the value of the damage coefficient were determined. To assess the distribution of residual deformations, a graphoanalytic method and a photoelasticity method were used. Experiments on the organization of the structure of models of decorative elements of various shapes confirmed that the distribution of deformations is determined by the geometric parameters of the products. It is established that the use of fiber changes the mechanisms of organization of integral structures of products. The active participation of fiber in the organization of the structure of products gives grounds to consider it not only as a reinforcing’ components of the structure, but also an equal component of decorative materials with a directed purpose - to regulate and manage the processes of structure formation at all levels of structural heterogeneities of the material. Dispersed-reinforced structures formed under the influence of fiber change the damage of the material, perceive and dissipate volumetric integral deformations.
INVESTIGATION OF THE BEHAVIOR OF SUPPORT ZONES OF CONTINUOUS REINFORCED CONCRETE BEAMS UNDER REPEATED AND LOW-CYCLE ALTERNATING LOADS
Based on the authors' and other researchers' experimental studies, this article presents an analysis of the behavior of inclined sections in the support zones of single-span and continuous reinforced concrete beams under low-cycle loads and changes in the stress-strain state depending on the shear span of the external load application. The calculation of reinforced concrete beams inclined crack is due to many interdependent factors. Beam testing attempts to identify the main criterion for the strength of the inclined section and, based on this, proposes a method for calculating inclined sections. The accuracy of calculating the strength of inclined sections of reinforced concrete beams on the action of the transverse force and bending moment according to the methods, according to methods based on the theory of concrete strength fully depends on the reliability of the assumptions made and functional expression of tangent stresses and normal stresses taking into account factors, considering the factors that characterize the behavior of the reinforced concrete element in the shear span. If we compare these calculation methods with the method based on the equilibrium of limiting forces, the latter is the least labor-intensive for designers. Current regulatory documents [1] propose a method for calculating inclined sections using a strut-and-tie model (truss analogy of the new European standards [2]), which also has a number of difficulties in actual calculations of the transverse sections of beams. In this case, bent bars in beams can be used as transverse reinforcement in combination with vertical transverse bars.
FORMATION OF INCLUSIVE SPACES IN ARCHITECTURE
The article analyses the current state and problems of forming inclusive spaces in the world and national architecture. The International and Ukrainian regulatory documents that regulate the inclusiveness and barrier-free accessibility for all the population groups are analysed. The concepts of “inclusion”, “disabled person”, “disability”, “people with limited mobility”, “barrier-free space” are defined. The main organising elements of a quality inclusive environment in all the social spheres are identified. An urgent task is to provide the availability of residential and public buildings for all the citizens, regardless of their physical capabilities. Inclusive spaces of modern architectural development are not only about creating the appropriate infrastructure, but also about transforming the existing one. The purpose of this research is to identify the main elements of the organisation of a high-quality inclusive environment in all social spheres. The necessary analysis of the current trends in the architectural development of inclusive spaces in large cities, as well as the peculiarities of accessibility for people with disabilities and people with limited mobility, has been carried out. Main research methods are comparative and historical analysis; visual and analytical method; monitoring method; analysis of statistical data and qualitative indicators; collection, analysis, presentation, and interpretation of the information on theoretical and practical issues of organising an inclusive environment, which is reflected in the works of foreign and Ukrainian researchers. The findings of the study showed that the developments aimed at solving the problems of creating inclusive spaces are relevant and timely. An important aspect of a barrier-free environment is the development of inclusive spaces in modern cities. The different types of barrier-free environment, including physical barrier-free, digital, educational and economic, social and civic, as well as the information barrier-free, are very important for the development of inclusive spaces in the world and national architecture. Persons with disabilities and people with limited mobility have extremely limited opportunities to realise their rights.
PROSPECTS OF USING RECYCLING AGGREGATES IN VIBROPRESSED MASS-PRODUCED CONCRETES BASED ON ULTRA-STIFF MIXTURES
Serial production of vibropressed fine-grained ultra-stiff concrete paving elements (PE) has been increasingly widespread in Ukraine in recent years, progressively occupying a leading position in the manufacture of construction products for road and municipal construction. As the production of modern concrete PEs on high-performance forming complexes allows for the possibility of defective freshly molded products, there arises a need for their removal from the technological line of finished product manufacturing. Defective freshly molded concrete products obtained during production should be processed into recycled aggregates for subsequent use in the production of high-quality vibropressed finished products.
EXPERIENCE IN IMPLEMENTING THE PROBABILITY METHOD FOR CALCULATION OF BUILDING STRUCTURES
The current method of calculating building structures by limit states (previously by allowable stresses) is essentially semi-probabilistic. The main parameters of the method – load values, strength characteristics of materials, dimensions of elements, etc. – have a variable statistical nature. They are described by probabilistic methods, on the basis of which deterministic ​​design parameters are justified, which are subsequently used in calculations. Meanwhile, in parallel with this dual method, for many years, fully probabilistic (statistical) approaches to the calculations have been developed. The beginning of this process can be considered the end of the 1930s, when the probabilistic nature of the safety factor, represented in the canonical form of the product of factors, was discovered, and numerical values ​​of the guarantee of the non-destructibility of the structure were obtained. The 1950s and 1960s were marked by proponents attempts of probabilistic methods to introduce the concept of strength reserve and safety characteristics into design practice. Since the 1970s, domestic specialists have been actively developing probabilistic methods, and their results have been implemented in regulatory documents. In recent years, publications have appeared with proposals for further implementation of probabilistic approaches in the calculation.
SUITABILITY OF MIXTURES FOR 3D PRINTING BASED ON TECHNOGENIC RAW MATERIALS
The article studies the comparative effect of dispersed mineral products of technogenic origin on the suitability of the mixture for extrusion molding using a 3D printer. To study the properties of extruded mixtures, a laboratory printer was designed and built. The use of the most common mineral additives of technogenic origin in Ukraine was considered, in particular: ground blast furnace granulated slag, fly ash, limestone dust and granite aspiration dust. The studied compositions of fine-grained concrete mixtures provide the minimum required values of structural strength and compressive strength at the age of 1 day. The possibility of obtaining suitable mixtures for 3D printing, based on dispersed materials of technogenic origin, is experimentally substantiated. A method is proposed for determining the suitability of mixtures for 3D printing and changing it over time, which ensures the extrusion of the mixture and the definition of a possible printing window. The criterion for determining the parameter of formability by the spread of the cone on a shaking table is different for different mineral additives, but is within the range of 200...220 mm. The proposed method can be suitable for mixtures using and containing the studied dispersed materials of technogenic origin, as well as determining the possible printing window of fine-grained concrete mixtures.
МЕТОДИКА ВИПРОБУВАННЯ ДВОШАРНІРНИХ ЗАЛІЗОБЕТОННИХ РАМ З ШТУЧНИМ РЕГУЛЮВАННЯМ ЗУСИЛЬ
Currently, monolithic reinforced concrete is the main building material in the construction of housing, social and cultural facilities, in industrial construction, in the effective development of underground space, in transport construction, in the construction of buildings and structures of various configurations. At the same time, one of the main load-bearing elements of buildings and structures is frame structures. Despite the fact that reinforced concrete frames are widely used in modern construction practice, there has been insufficient experimental research into the operation of frames, especially frames with artificial force regulation. To study П-shaped reinforced concrete frames with artificial force regulation, reinforced concrete frame samples were manufactured. During the research, three series of reinforced concrete frames were tested, four frames in each series