"Вестник МГСУ"

For more than 20 years the author with his colleagues conducts engineering researches, design of restoration and reconstruction of various architectural monuments. Full cycles of works from engineering investigations to implementation of the own projects are executed on three objects: 1) architectural monument of the 19th century, the church in the museum preserve Abramtsevo (Moscow region), during 2005-2006; 2) a monument of Orthodox church history, a unique soil construction which is called "The Holy Ditch" in the village Diveevo (Nizhny Novgorod region) since 1997 to the present; 3) Church of Our Lady of Kazan also in Diveevo village during 1997-2002. For churches engineering researches are executed, calculations of the bases are made, ways of strengthening the bases are chosen, architectural projects of restoration are created. The church is restored by students under supervision of the experts from the university. The church in Diveevo was partially destroyed during the Soviet period. During restoration high-rise parts of the church were constructed. The works were performed by working restorers under control of the author of article in 2002-2004. Participation of students, masters, graduate students in restoration works had great educational value, gave to young people experience and knowledge. Students studied under professional restorers. Generalization is given in summary. D.S. Likhachyov's theory and our own experience are used. The principle of reconstructing barbarously destroyed engineering constructions, buildings and architectural complexes is formulated. It corresponds to the realities of the 21st century, new technological capabilities and requirements of modern society. Briefly: the reconstructed structure, in our opinion, has to face not only the past, but also the future. It is not always necessary to create the exact copy of the lost construction. Recreating the destroyed construction, it is necessary to apply new materials to increase the reliability and eliminate constructive imperfection of ancient constructions together with preserving old forms. Buildings and constructions have to be under construction anew mainly for performance of former functions, but the buildings have to meet modern requirements on the equipment and internal planning, modern technical norms. The project of the lost building needs to be made taking into account the change of environment. These provisions were successfully incarnated in the process of construction of St. Ditch in Diveev and they are also illustrated on the examples of the reconstruction of the Cathedral of Christ the Savior in Moscow and Frauenkiche in Dresden.

Subject: concrete for construction of protective structures from neutrons with energy of 14.8 MeV. When constructing protective structures from ionizing radiation in the buildings of nuclear facilities, special attention is given to the work quality and conformity assessment of the built structures to the project documentation requirements. Research objectives: the objective is to obtain the necessary data for verification of software programs for neutron-physical analysis of protective characteristics of concretes with different chemical composition. Materials and methods: in order to achieve the objectives, computational and experimental studies were carried out using a 14.8 MeV neutron generator, a spectrometric and dosimetric equipment complex, and the ANISN computational software package. Studies were carried out for two compositions of concrete. Results: the results of the performed studies showed satisfactory agreement between the computational and experimental data. Conclusions: the obtained results of computational and experimental studies will allow us to develop simple semi-empirical calculation methods that can be used in designing concrete compositions with the required protective efficiency from neutrons with energy of 14.8 MeV and in controlling the stability of chemical composition of dry concrete mixtures during their production and usage.

The authors examine the impact of dynamic loads produced on the strength and deformability properties of concretes and their micro-cracking. The experiment performed and analyzed by the authors consisted in the dynamic loading of a concrete sample that caused its destruction. The analysis of the experimental findings consisted in the identification of specific conditions of cracking, derivation of dependencies and compilation of charts. The following conclusions are made in furtherance of the authors’ analysis of the experiment in question:1) experimental findings help identify the nature of influence of the stress state on the strength value, deformability and micro-cracking of concretes. For example, it is discovered in the process of the experiments that the lower bound of the microracking dynamics increases more significantly than the prism strength.2) Regularities of influence of the rise in the loading intensity produced on concrete deformation properties are identified. The key factor of the concrete destruction is not the nature of the deformation, but the value of the overall strain.

The behavior of reinforced concrete elements under some types of cyclic loads is described in the paper. The main aim of the investigations is research of the stress-strain state and strength of the inclined sections of reinforced concrete beam elements in conditions of systemic impact of constructive factors and the factor of external influence. To spotlight the problem of cyclic loadings three series of tests were conducted by the author. Firstly, the analysis of the tests showed that especially cyclic alternating loading reduces the bearing capacity of reinforced concrete beams and their crack resistance by 20 % due to the fatigue of concrete and reinforcement. Thus the change of load sign creates serious changes of stress-strain state of reinforced concrete beam elements. Low cycle loads of constant sign effect the behavior of the constructions not so adversely. Secondly, based on the experimental data mathematical models of elements’ strength were obtained. These models allow evaluating the impact of each factor on the output parameter not only separately, but also in interaction with each other. Furthermore, the material spotlighted by the author describes stress-strain state of the investigated elements, cracking mechanism, changes of deflection values, the influence of mode cyclic loading during the tests. Since the data on the subject are useful and important to building practice, the ultimate aim of the tests will be working out for improvement of nonlinear calculation models of span reinforced concrete constructions taking into account the impact of these loads, and also there will be the development of engineering calculation techniques of their strength, crack resistance and deformability.

The author presents the results of measurements of total deformations of the space-grid floor in relation to the torsional strain of beams and the rigidity of beams in bending and torsion while monitoring the erection of the floor of a building.
Any space grid system is utterly sensitive to changes in relations between the rigidity of elements. No experimental data covering space grid floors or any method of analysis of their stress-strain state are available.
The author performed the assessment of interrelations between the rigidity of some beams in the two directions by means of a full-scale loading test (monitoring) of the monolithic space grid floor, beam size 8.0 × 9.2 m. The purpose of the assessment was to confirm the bearing capacity and the design patterns based on deflections and stresses of elements to select the operational reinforcement value. Monolithic concrete was used to perform the load test.
As a result, the width of concrete ribs was found uneven. In the design of reinforced concrete space rib floors it is advisable to develop detailed models of structures through the employment of the finite element method due to the significant sensitivity of the system to distribution and redistribution of stresses.
Large spans of monolithic space rib floors require the monitoring of the stress-strain state and computer simulations to adjust the design pattern on the basis of the monitoring results.

In the article the author describes the importance of the technological regulations development in the process of constructing various transport constructions: tunnels, subways, bridges and other important objects. In the article the peculiarities of the tech- nological regulations development are fully taken into account; the dependence of the depth of their development and the quality of the concrete constructions, as well as the speed of the objects of transport infrastructure construction, including the examples of building the road tunnels in Moscow. The course of their development is shown with account for the main provisions, which should be included in technological regulations in order to ensure the most complete coverage of the issues arising in engineering, laboratory and Supervisory structure in the process of performing the works. The author proposes new effective materials and technologies of works. In particular, sufficient attention is paid to self-compacting concrete — a new type of concrete, which is able to flow and compact under its own weight, completely filling the formwork even in case of dense reinforcement, while maintaining the homogeneity and having no seals. The application experience of concrete self-sealing in the construction of the metro showed that labor costs for the concrete mixture sealing were 5-6 times reduced, and the speed of laying the concrete increased 2-3 times. When laying self-compacting concrete high-quality surfaces are formed, which do not require additional costs to bring them to the design parameters. In addition, the work shows the parameters of the technological processes and sets various types of works sequence: the article describes the features of formwork, placement and curing of the concrete in terms of year-round construction, shows the importance of thermo physical calculations of concrete hardening and the efficiency of using self-sealing concrete. Sufficient attention is also paid to the methods of quality assurance and to the methods of preventing cracking of various structural elements of a construction, as well as to the safety requirements and ensuring proper protection of the environment.

The article represents a summary of findings of various research projects aimed at the optimization of specific items of small size machines developed and pilot tested at different stages of construction operations.For 15 years, Department of Mechanization of Construction Processes, Kharkiv National University of Civil Engineering and Architecture has been engaged in design, pilot testing and monitoring of practical application of small size construction machinery. All machines and items of equipment have adsorbed numerous research findings, and no similar products are available in Ukraine and worldwide.The authors analyze different items of construction machines that have already been tested in the course of construction operations. They include a twin-piston coun- terflow mortar-and-concrete pump, two-piston direct-flow mortar-and-concrete pumps equipped with ball valves, spring valves and disk valves, advanced cascade concrete mixing machines. Each of the above machines can operate in pursuance of a pre-set pattern of shotcrete operations.All machines are universal, as twin-piston concrete pumps may pump concrete mixes having different workability rates; they can also be used to transport building mixes in horizontal and vertical directions; they are applied for shotcrete operations. They are efficiently used in the preparation of different mixes.All machines and items of equipment are protected by Ukraine-wide patents. They are recommended for wide-scale use due to sophisticated structural solutions invested into their design.

Deformation parameters of concrete are adequately studied under static uploading of samples until fracture. Methods of their determination during unloading (primarily due to the lack of experimental data) is not presented in the regulatory and scientific literature. That hinders the development of calculating methods of loadings for reinforced concrete structures, which vary according to certain cyclical regularities. The basis for computational models development for unloading are the results of the studies with short-term tests of concrete samples, where the sample is loaded to a predetermined level of compressive stresses, and then it is unloaded. The purpose of the research is to establish an analytical connection between stress and deformation parameters of concrete on axial loading and unloading branches with compressive stresses. The subject of the study is: axial and transverse deformation coefficient of transverse deformation volume deformations. The treated cycles have different values of maximum stress, including close to the limit values, taking into account the dilation of concrete. Permanent deformations during unloading are determined in increments of stress and strain by radial method. A connection is established between the initial elastic modulus of concrete and the modulus of deformation during unloading. On the basis of experimental data the analytical determination of the quantities depending on the residual strains for partial or complete unloading was offered. It was found out that in case of increasing stress level at the beginning of unloading the share of transverse strain increases and in case of full unloading, volume deformations increase. In case of unloading from the stress level, when dilatation property is manifested, they change the sign to the opposite, which is, become positive. The authors show a comparison of calculation results of the proposed method with experimental data obtained.

Fiber reinforced concretes possess high strength under dynamic loadings, which include impact loads, thanks to their high structural viscosity. This is the reason for using them in difficult operating conditions, where increasing the performance characteristics and the structure durability is of prime importance, and the issues of the cost become less significant. Applying methods of disperse reinforcement is most challenging in case of subtle high-porous materials on mineral binders, for example foamed concrete. At the same time, the experiments conducted in Russia and abroad show, that also in other cases the concrete strength resistance several times increases as a result of disperse reinforcement. This doesn't depend on average density of the concrete and type of fiber used. In the article the fibre reinforced concrete impact resistance is analysed. Recommendations are given in regard to fibre concrete application in manufacture of monolithic floor units for industrial buildings and precast piles.

The objective of the research project was to design multi-component concrete with an optimized pore structure designated for sewage water treatment facilities. It was followed by the study of their stability in aggressive environments. Measurement of mesopores and macropores with diameters of 0.0055 to 360 mcm was taken using AutoPore IV 9500 porosimeter. X-ray analysis of samples was performed using diffractometer ARL X’TRA produced by Thermo Scientific (Switzerland). Modified 28-day concrete cubes were exposed to aggressive environments for 1 year at low (+4 ± 2 °C) and high temperatures (+20 ± 2 °C) to identify their linear deformation characteristics. Compressive strength of samples was tested upon completion of each three-month period.The authors have found out that degradation of concrete samples in the corrosive environment of waste waters accompanied by generation of thaumasite is less intensive than that in the waste waters that have ettringite generated. Thus, the authors have discovered that the lower the temperature of the aggressive environment of the waste water, the more intensive the formation of ettringite that causes destruction of the concrete. Optimization of the concrete structure is attained through the optimization of the concrete composition. Application of fine-grained silica causes generation of concrete that is highly resistant to the aggressive effects of sulfates and chlorides.

Major penetrating waterproofing mixtures represent dry mixtures of cement and sand having admixtures, or systems of mineral salts, used to block the structure of capillaries and pores of cement mortars and concretes. Thin layers of waterproofing mortars are applied to sufficiently porous surfaces. As a result, the water content is reduced in the course of hardening. This process causes contraction and cracks in the coating.The findings of the research performed by the authors have proven that waterproofing materials containing wollastonite-based Antigidron system comply with each basic requirement applicable to penetrating waterproofing materials, as their admixtures penetrate into the concrete to seal concrete pores and to generate insoluble crystals.The new Antigidron system has the following strengths. Each component of the proposed system is made in Russia. It has efficient operating properties, and its cost is1.5 — 2 times lower than the one of similar products.

The objective of the project described in this article was to design the fiber concrete having an optimized structure and high strength characteristics. In the course of the project development, the fibre concrete was modified by the nanodisperse silica additive. As a result, the authors designed several modified fibre concrete compositions having optimal physical and mechanical properties. Electronic microscope Quanta 200 3D was used to study the microstructure of samples. Diffractometer ARL X’TRA was used to perform the X-ray analysis of samples. Selection of the optimal composition of the concrete was performed using the orthogonal experimental design technique. The nanodisperse silica additive was synthesized using method of chemical polycondensation followed by subsequent stabilization of acetate. This super-plasticizer improves the density and strength properties of the composite. Experimental and statistical models were generated as regression equations to determine the optimal composition of the fibre concrete.

Portland cement-based concrete is widely used in civil engineering. Therefore, it is very important to determine the preconditions of corrosion of the cement concrete. The service life of concrete structures can be substantially reduced by the alkali-silica reaction. It is well known that this reaction causes formation of the sodium silicate hydrogel. Thus, by identifying this gel, a researcher can make an assumption about the reasons for the corrosion. Obviously, macroscopic quantities of sodium salts can be discerned using analytical chemistry methods. Unfortunately, determinant values of such salts in the concrete structure are usually very small. Thus, there is a need for special research methods.Raman spectroscopy is an advanced method based on the analysis of instantaneous two-photon non-elastic light scattering. This method is applicable even in case of small quantities of chemicals under research. The first successful study of silicates using Raman spectroscopy methods was performed in the 20ies of the 20th century. In this work the authors have proven that sodium hydrogels can be easily identified in the concrete using the Raman spectroscopy. In the course of the analysis of the interphase boundary between the cement stone and the aggregates, the authors observed, at least, one spectral peak which did not belong to cement or to the disperse phases of the concrete. At the same time, this peak can be classified as a peak of the sodium silicate. Thus, sodium silicate gel is generated during the service life of the structure under research, and this research has revealed the presence of the alkali-silica reaction.

The authors describe methods of composing a concrete dynamic deformation diagramme, if the pre-stress produced by the static load is taken into account. It is noteworthy that the available data concerning the influence of the load preceding any dynamic load and produced on the mechanical properties of the concrete are limited and discrepant. The authors propose their methodology of an experiment and describe items of specialized equipment employed to hold the experiment in question. The authors have held an experimental study to reproduce the conditions of a real structure exposed to an emergency dynamic load. Samples to be tested are exposed to the static load of varied intensity without any relief. Duration of the load application will be six months. The diagram should be recommended for reference in the course of design of concrete and reinforced concrete structures exposed to dynamic loads applied in emergency situations.

The author considers the problem of control over the frost resistance as the most important
characteristic of concretes designated for hydraulic engineering structures. His method is based on
the identification of correlation between the frost resistance and the Poisson ratio. The value of the
Poisson ratio is measurable through the employment of the ultra-sound method.
The proposed methodology contemplates the following sequence of acts. First, the value of
the Poisson ratio of air-dried samples of concrete is identified through the employment of the ultrasound
method. Thereafter, samples are exposed to cyclic freezing and thawing. Based on the testing
results, correlation between the Poisson ratio values and the frost resistance of the concrete is
identified. Further, the same ultrasound method is used to find out the values of the Poisson ratio of
the hydraulic engineering structures on site to identify the value of the frost resistance of the concrete
on the basis of the correlation identified earlier.
Mass produced ultrasound testing devices are to be used for the above purposes. They must
have screens, and their ultrasound range must fit concretes. Poisson ratio values are identified
through the penetration of the ultrasound signal through the thickness of a concrete element under
control. Sensors are to be positioned at the angle of 45°, and the time of travel of longitudinal and
shear (lateral) ultra-sound waves through the thickness of a concrete sample or a concrete element
is measured. The time of travel of longitudinal waves is measured on the basis of the value of the
first signal, while shear waves are measured on the basis of the phase transition of ultrasound
waves. Thereafter, velocities of waves are calculated pursuant to the methodology proposed by the
author. It is noteworthy that the accuracy of the proposed method is quite high, and the margin of
error does not exceed 3 %.

Results of research that aimed on appearance of self-healing ability between characteristics of construction materials and products, based on mineral binding substances, via bioprocesses of selective action, resulting from the introduction of bacterial biomass into the composition of mortar and consruction cement mixes were shown in the article. The article contains the results of revealing the most active forms of biological material adapted to the conditions of formation of building products based on mineral binders and results of investigating their effect on the rheological, technological and operational properties of mortars that are modified. Portland cement and gypsum binder were used as mineral binders to produce solution mixtures with different pH values. Efficiency of bacterial cell action was determined via estimation of cell urease activity. The variations of values of water-cement ratio appeared to be pronounced in dependence on: concentrations of introduced cell biomass content; changes in the urease activity of the bacterial cells, varied with the values of pH of used medium; the use of both highly porous natural and artificial materials as microcontainer carriers. The obtained results make it possible to conclude about significant change in the rheological properties of cement-sand mortars owing to the presence of biological surfactants entering into a content of bacterial cells. The influence of cells concentration on a setting time and strength characteristics of cement-sand mortars was determined.

In the article the information on the upcoming international conference on concrete and reinforced concrete is offered. The aim of the conference is stated, as well as the main points of the program, composition of the conference, the papers’ subject is disclosed. The author highlights the effect of reinforced concrete invention on the world civilization development. According to the author’s point of view, today reinforced concrete became one of the most evident means of the world development.

The process of early structure formation that occurs in hardening concrete where concrete waste are used as coarse aggregate is examined in this article.