The monograph discusses the tasks of assessing the reliability, safety and operational quality of marine reinforced concrete structures, taking into account all types of corrosion. A review of studies of corrosion of concrete and reinforced concrete of buildings and structures on land and in the aquatic environment within the framework of the time paradigm is carried out. A method for calculating erosion and abrasion from ice formations is given. A multiscale multiphysical approach to corrosion analysis is described. A method for calculating the mass transfer of a pore solution using a modified method of streamlines at the meso level is presented. The finite element macromodel is applied with a deformation modulus determined by the mesomodel and non-destructive testing methods. It is intended for researchers, teachers and graduate students of construction specialties.

The purpose of this paper is to develop a unique multifunctional composite material and study its properties. To achieve this goal, it is necessary to solve the following main tasks: - study of the evolution of mechanical properties of sludge concrete under the action of cyclic water saturation-drying; - study of conductive coating modified with carbon nanomaterial; - study of hardening of heavy metals and mechanical properties of sludge concrete under the influence of cyclic water saturation-drying; - study of sludge concrete with an electrically conductive coating modified with carbon nanomaterial. Currently, there are more than 200 municipal sewage treatment plants in operation in the Republic of Belarus. The amount of wet sludge released during wastewater treatment at municipal treatment plants can be up to 2% of the volume of incoming wastewater. A significant amount of waste generated creates a problem with the need to place it, and not only in Belarus, but also in most countries of the world. The most promising method of using wastewater sludge is to use dewatered sludge as a fuel alternative to coal, for example, for cement production. Although this approach to a certain extent ensures effective disposal of sludge, but in the process of its combustion, the ash is enriched with toxic heavy metals, which creates a risk of environmental pollution. Thus, this does not completely solve the problem of sludge recycling. It was proposed to use the obtained sludge ash as an additional binder for concrete in order to prevent the leaching of heavy metals in sediments and reduce the environmental impact of clinker production. At the same time, there is the issue of floods and other external factors that provoke saturation of concrete with water, which leads to expansion and contraction of the material, thereby increasing the internal stress of the concrete. When these stresses reach the strength threshold of the concrete, cracks begin to form. At the same time, this increases the risk of leaching of heavy metals from the concrete matrix. These factors have become a problem for the use of slurry concrete in green building.

The monograph substantiates the concept of multilevel reinforcement of structural heavy concrete, including the level of nano-, micro-reinforcement of cement stone with tubular carbon nanomaterials and macro-reinforcement of the concrete structure with steel fiber. Fiber-reinforced concrete compositions have been developed to determine the optimal content of steel fiber and carbon nanomaterial during monoarming, the properties of fiber-reinforced concrete of multilevel reinforcement with a combination of nano-, micro-reinforcement with tubular UNM and macro-reinforcement with steel fiber have been studied. A technique has been developed for a multiparametric assessment of the properties of fiber reinforced concrete of multilevel polydisperse reinforcement in order to determine strength, crack resistance and deformability in laboratory and building conditions. A set of technological measures for conducting concrete works with the preparation and use of fiber reinforced concrete of multilevel polydisperse reinforcement in the construction of monolithic building structures is proposed. A comprehensive methodology for assessing the quality of fiber concrete in building structures has been developed.

A literature review has been carried out on the effects of carbon nanotubes (CNT) and macrolevel fiber on concrete porosity indices. The results are presented of investigations into the porosity of nanomodified concrete with dispersed reinforcement (nanofiber reinforced concrete) in terms of the kinetics of water absorption of nanotubes and hard fiber. For dispersed reinforcement, use was made of various hard fibers and their combinations: polymer, basalt, steel wire ones and those from wave-, anchor-, and straight profile sheets. It has been established that the introduction of dispersed fibers results in a change of concrete porosity indices. Hard fibers break up relatively large capillary pores into smaller ones. In this case, the fiber coarseness and its amount in a volume are important. In integrated fiber reinforcement, the size of capillary pores either decreases or does not change at all with respect to the initial concrete. Intense mechanical mix agitation contributes to raising the porosity index. Hard fibers of a more rigid structure tend to demonstrate a higher propeller effect in mixing. The presence of different-scale hard fibers makes it possible to avoid a propeller effect and the need to increase the concrete porosity index.

This paper adopts a contrastive experimental method to design and prepare reed fiber concrete. It discusses the influence of reed fiber content (2%), fiber length (1.5 cm for short reed fiber and 3 cm for long reed fiber), and moisture content (0% for dry fiber and 85% for wet fiber) on the mechanical properties of concrete, and compares it with the reference concrete without reed fiber. The experiment obtained the flexural and compressive strength of reed concrete, and analyzed the apparent mechanism of concrete specimens after failure. The experimental results show that the addition of reed fiber enhances the mechanical properties of concrete, the compressive strength of concrete increases by 1.13 MPa compared with the reference concrete, and the flexural strength increases by 2.32 MPa. The flexural performance of reed fiber reinforced concrete with 3 cm dry fiber and 0% moisture content is the highest, reaching 3.5 MPa; the compressive performance of reed fiber reinforced concrete with 85% moisture content and short reed fiber is the highest, reaching 2.69 MPa. This paper shows that adding 2% of reed fiber to concrete is feasible, and adding 1.5 cm, 85% moisture content wet reed fiber can better promote the mechanical properties of reed fiber concrete.

There are several models in which the corrosion rate, rust expansion, and resulting crack propagation around reinforcement can be assessed. The effect of crack-induced corrosion on the behavior of the structure can also be assessed. Several methods have been proposed to evaluate the mechanical performance of reinforced concrete structures with corroded reinforcing bars. Changes in the mechanical properties of reinforcing bars, concrete and their interactions need to be modeled based on the concept of analytical methods. The load-bearing capacity of reinforced concrete beams with reinforcement corrosion was calculated using the finite element method. The influence of reinforcement corrosion is considered from the point of view of changes in the mechanical properties of reinforcement and adhesion of reinforcement to concrete. Instead of reducing the cross-sectional area of the reinforcement, the Young’s modulus and yield strength of the corroded reinforcement are reduced. Numerical modeling of the structural performance of reinforced concrete structures with reinforcement corrosion using a finite element program has shown that modeling of structural deterioration, such as reinforcement corrosion and concrete cover cracking, sometimes has a large impact on the analytical results. The structural characteristics of reinforced concrete elements with reinforcement corrosion are calculated. Using this modeling method, an analysis of the degree of influence of corrosion on structural characteristics was carried out.

Hydration of cement materials is accompanied by the formation of calcium silicate hydrates (CSH). Accordingly, the hydration process is completed in the early, middle, and late periods, leading to the formation of two types of CSH phases: of low density (LD) and high density (HD). Usually, under normal conditions, LD CSH is formed in the middle period, while the formation of HD CSH predominates in the later stage. In using the nanoindentation method, it becomes possible to explain the nanogranular nature of the CSH gel, which is characterized by the contact forces of the CSH gel particles for these phases. Studies of cement stone samples at W/C = 0.21 and at the content of hydrothermal SiO2 nanoparticles in the combined additive 0.000006 wt.

The optimization of mechanical performance through the use of fiber-reinforced polymer composites is achieved via META simulated experimental design, with a primary emphasis on enhancing the mechanical characteristics. Incorporating reeds and coconut shells, this approach aims for an optimal design that minimizes polymer usage while ensuring specified mechanical performance and economic efficiency. The research, anchored in a probabilistic framework, prioritizes a reliability-based optimization methodology. To assess mechanical performance, nonlinear pushover analyses at the system level are conducted, with META simulations playing a key role in exploring uncertainties. Within the META framework, inelastic interstory drift ratios are treated as indeterministic variables, while the thickness of the polymer jacket–featuring reeds and coconut shells–is considered a deterministic design variable. This refined design process not only reduces polymer costs but also systematically evaluates the cost-effectiveness of incorporating reeds and coconut shells, all while adhering to stringent structural reliability constraints. Explicit reliability index constraints, honed through META simulations, ensure the robustness and adaptability of the design optimization process. The numerical optimality criteria method within the META framework provides an efficient solution to the nonlinear retrofit design optimization problem. Illustrating the application, a design example showcases the seamless integration of reeds and coconut shells, resulting in a significant enhancement of mechanical performance within the context of retrofitting.

Concrete composites with low defects, dense and homogeneous, with a high degree of adhesion between the cement matrix and aggregates, as well as a high ratio between static tensile and compressive strengths and plasticity have the best crack resistance characteristics. This ratio increases in the case of the use of fiber-reinforced concrete. Modern research in nanotechnology focuses on the management of matter at the nanoscale level, which makes it possible to create materials with new properties. Due to the high aspect ratio, flexibility, high strength and rigidity, carbon nanotubes (CNTs) exhibit reinforcing properties. Due to their nanoscale features, CNTs interact with a complex network of calcium-silicate-hydrate binder (C – S – H), contribute to a decrease in porosity and compaction of the cement stone structure, increase the shear forces of matrix adhesion in the contact zone. Thus, there are all prerequisites to assert that fiber concrete with a cement matrix modified with carbon nanotubes will have the required high strength characteristics and crack resistance due to multilevel dispersed reinforcement and the efficient operation of fiber in a nanomodified concrete matrix. This article presents the results of testing samples made of cement stone, concrete and fiber concrete with carbon nanotubes. The presence of carbon nanotubes in cement stone contributes to an increase in compressive strength by 11 %, tensile strength during bending by 20 %. The test results of samples made of reinforced fiber concrete modified with nanocarbon materials have shown an increase in tensile strength during bending up to 109 %, tensile strength during splitting up to 82 %, axial tensile strength up to 78 %.

The recycling bio-waste shells problem has grown more and more serious in recent years and many efforts have been made to solve this problem. One possible solution is to put these bio-shells into concrete and recycle them as building materials using the aggregate matrix concrete approach. To verify the engineering feasibility, the mechanical properties of bio-shells aggregated concrete were invested via gradient substitution rates at 10%, 30%, and 50% with a total of 78 groups of specimens in this paper. Our results show that the mechanical properties of the concrete were enhanced in maximum flexural strength and maximum compressive. Economic performance was also analyzed and found that the costs of frame-shear structure, frame structure, and tube-in-tube structure were reduced by 10.2%, 10%, and 10.3%. The carbon environmental assessment also shows superiority in the carbon reduction of a single specimen with various rates of the shell. In summary, compared with ordinary concrete materials, it is very possible to use waste bio-shells as a substitute for aggregates to develop the sustainable recycling development of concrete materials.

This article mainly conducts mechanical and mechanical experiments on non-metallic nanofiber concrete and non-metallic reed fiber concrete. Through relevant mechanical experimental data, the mechanical properties of the two fibers are compared in detail and the structures of the two fibers in concrete are determined. Durability, environmental protection, chemical stability and physical and mechanical properties hope to provide reference for the development of non-metallic fiber concrete materials.

The article proposes an approach to improve the technological level of production on the basis of systematization of the main tasks and solutions of technical re-equipment of precast construction plants. The principle of realization of the proposed system approach is presented in the form of a flowchart. The proposed algorithm demonstrates the practical importance of taking into account the interrelation of construction and production processes for technical re-equipment without stopping the main production and reducing the duration of construction and installation works. Solutions for increasing the production capacity of lines pallet circulation and compensating for the increasing demand for concrete mix while increasing the productivity of the lines are presented. For technological lines circulation of pallet the efficiency of the organization of processes exceeding the directive schedule at the posts not connected with the main flow and with the individual schedule of work is substantiated. The functionality of local mortar-concrete unit of block-modular layout in the span is shown to increase productivity and rhythmicity of work of molding stations.

Hydration of cementitious materials is accompanied by the formation of calcium hydrosilicates (CSH). Accordingly, the hydration process is completed in the early, middle and late periods, leading to the formation of two types of CSH phases: low density (LD) and high density (HD). Using the nanoindentation method, it was explained nanogranular nature of the CSH gel, which is due to the contact forces of the CSH gel particles for these phases.

The homogeneity of the structure of the boired pile shaft has been studied based on the results of four-channel inter-well ultrasonic (US) monitoring. The actual lengthy of the piles has been determined with the detection of defragmentation of the pile shaft, the compressive defects have been determined, and continuity defects have been identified based on a joint analysis of data from the method of interwell ultrasonic monitoring. The use of four channels allows to control separately the peripheral and central areas of the pile in six directions. The data of the seismoacoustic method coincided with the parameters of ultrasonic monitoring in terms of identifying zones of concrete heterogeneity, reducing the pile cross section, etc. For all of the listed piles, data are not registered by the named test methods indicating defragmentation of the pile shaft – the presence of sections in the cross sections of which there is no concrete at all. These test methods for all piles confirmed the compliance of their actual length with the design values. A significant defect in the continuity of the concrete of the 40op pile, according to the data of ultrasonic monitoring and seismoacoustic method, was registered in the interval of marks – (17.5–18) m, manifesting itself a sa decrease in the propagation velocity of the ultrasonic pulse from 25 to 50 % in two sounding directions, inclu-ding diametrical. This defect can be interpreted as a decrease in the effective section of the pile to 25–50 % of the average value. Defective sections of piles were found in their upper part at depth marks from 0 to –1.5 m, counting from the end surface of the head. At the same time, differences in the physical and mechanical parameters of concrete at these marks were also observed within the cross section of piles [1–5].

Despite the fact that in principle the problem of durability of concrete for marine and transport structures in harsh climatic conditions has been solved, cases of premature destruction of structures are observed at the present time. The results of field surveys show that the destruction of concrete in structures can be both local and global. It is established that if the properties of concrete correspond to external influences, the maintenance-free service life can be at least 100 years. Examples of the construction and operation of seaport facilities on Sakhalin are a confirmation of this. The study of the mechanisms of freezing and destruction of concrete under frost exposure, taking into account the real indicators of the quality of concrete, showed that there are significant reserves in concrete technology that can be used to increase the durability of concrete without resorting to its complication. However, in the conditions of the construction site, these reserves are not properly realized due to objective and subjective reasons. Therefore, the main goal of durable concrete technology is to organize the manufacture of structures with concrete quality indicators that meet the design indicators in the conditions of the construction site.

The monograph is devoted to improving the methods of directed and controlled regulation of the C — S — H-gel structure by varying the doses, sizes, physical and chemical characteristics of the surface, and the nanoparticles used. The authors have developed an additive that additionally contains a superplasticizer to reduce the water demand of the concrete mixture and stabilize the nanoparticles. The dependences of the strength growth of cement stone and structural heavy concrete on the components of the complex additive are revealed. Experimental confirmation of the mechanism of action of a combined nano—additive with a reduced consumption of nanoparticles on the structure of C — S - H-gel was obtained based on the results of the application of a set of methods. It is revealed that the use of a complex additive contributes to a proportional increase in the reduced modulus of elasticity, hardness, and mechanical characteristics of Portland cement stone and concrete. The study of the additive in the conditions of the construction site showed the prospects of its application for construction, ensuring a reduction in the cost of the technology of nanomodification of concrete relative to the effect of improving performance. For specialists of research, construction and design organizations dealing with the modification of concrete with nanomaterials, as well as for students, undergraduates, postgraduates, teachers who work on the problems of building materials science.

Myocardial remodeling is well-known to be both an adaptive option under certain conditions of life (sports, pregnancy, etc.), and the result of cardiovascular pathology. The study of the features of cardiac remodeling includes the involvement of cardiomyocytes in the process by the level of troponins, creatine phosphokinase, and its cardiac isoform as markers of ischemia and necrosis. Also, neurohormonal rearrangement is evaluated using a natriuretic peptide, and endothelial dysfunction is determined using a C–reactive protein. The level of matrix metalloproteinases (MMP) and their tissue inhibitors (TIMP) reflects the degree of the proteolytic activity and collagen fibers’ degradation. However, there are no clear biochemical markers of “adaptive heart” and pathological changes in different age periods, in the climatic environment, various types and severity of sports loads, especially when evaluating matrix metalloproteinases and their tissue inhibitors. The primary task in determining the criteria for pathological remodeling of the myocardium becomes the definition of normative indicators.The aim of the study was to determine the reference values of the main biochemical markers of cardiac remodeling in healthy adolescents living in the Far North. The levels of troponin I, creatine phosphokinase-MV, aspartate aminotransferase did not exceed the generally accepted standard values. There were correlations between lactate dehydrogenase, aspartate aminotransferase, and mass-growth indicators of adolescents. Markers of extracellular matrix degradation (MMP-9, TIMP-1 and TIMP-4, MMP-9/ TIMP-1) differed from the data available in the published studies, which is probably due to the influence of tissue hypoxia associated with the climatic living conditions and the age in children of the study group.

In this paper, the mechanical and mechanical properties of two plant non-metallic fibers and one metallic fiber in concrete were analyzed. Design tests were conducted using two variable indicators of normal stress (σu/ MPa) and gradient fiber admixture (r/%). The flexural and compressive properties of reed fiber concrete, coconut fiber concrete, steel fiber concrete and plain concrete specimens were compared by the tests. It was concluded that both non-metallic fibers and metallic fibers can effectively improve the mechanical properties of structural concrete. According to the analysis of the experimental parameter diagram, the optimal dosing ratio of reed fiber and coconut shell fiber is 2%, and the optimal dosing ratio of steel fiber is 1.5%. In contrast, the impact toughness of metal fibers prompted the compressive performance of metal fibers is much stronger than non-metallic fibers, while the bending of non-metallic plant fibers can well improve the flexural strength of concrete prompted the flexural performance of non-metallic fibers is much higher than that of metal fibers. Therefore, the relationship between the mechanical stress of fiber concrete is: steel fiber concrete > reed fiber concrete > coconut fiber concrete.

Nanomodified fiber-reinforced concrete is a building material for which the required characteristics of fracture toughness are a distinctive feature. Determination of the stress intensity factor of fiber-reinforced concrete makes it possible to correctly assess the resistance of the material during the formation and development of cracks. The proposed multi-parameter methodology for assessing the quality indicators of nanomodified fiber-reinforced concrete makes it possible to evaluate the quality of a fiber-reinforced concrete structure in construction and laboratory conditions. To carry out control at the construction site, modern and long-used methods of non-destructive testing are used: ultrasonic sounding, ultrasonic tomography, elastic rebound, separation with chipping. For laboratory studies, the technique provides for the manufacture of prism samples that can be molded or cut from the body of the structure. This methodology makes it possible to obtain in laboratory conditions such material parameters as tensile strength in bending, tensile strength in splitting, critical stress intensity factor for normal separation, critical stress intensity factor for transverse shear, energy consumption for individual stages of deformation and destruction of the sample, as well as to evaluate the uniformity of distribution fibers. Moreover, it is provided to obtain all the parameters on one sample from the series, which eliminates errors and inaccuracies in the quality indicators of the material associated with different conditions of hardening, molding, inaccuracies in duplicating the composition.

Studies have been carried out aimed at improving the corrosion resistance of concrete and its other characteristics for operation in harsh environmental conditions. The influence of a complex additive containing multilayer carbon nanotubes and hydrothermal SiO 2 nanoparticles on the durability of concrete has been determined. Experiments were carried out to study water tightness, frost resistance, water absorption, and power parameters of concrete (stress intensity factors). It has been established that the introduction of nanoparticles into concrete improves the microstructure of its cement matrix, which leads to a decrease in the penetration of chloride ions into concrete and to an increase in its water permeability.