April 18, 2023 marked the 110th anniversary of the birth of the USSR State Prize laureate, Honored Worker of Science and Technology of the RSFSR, Honorary Member of the Russian Academy of Architecture and Construction Sciences (RAASN), Honorary Builder of Russia, Doctor of Technical Sciences, Professor Konstantin Vasilyevich Mikhailov.

The editorial board of the magazine, the editors, the older generation of employees of the NIIZHB named after. A.A. Gvozdev, colleagues and friends of Konstantin Vasilyevich Mikhailov highly respect his bright image, remember his intelligent demands as a leader, delicacy and high intelligence.

Article first published: 80th anniversary of NIIZHB named after. A.A. Gvozdev. Collection of scientific articles. Moscow: Publishing house of the Federal State Unitary Enterprise Research Center of Construction; 2007. 272 p.

Introduction. This work mentions the existence of traditional and non-traditional methods of seismic reinforcement of buildings and structures, including buildings built from masonry and historical architectural monuments. Concrete shotcreting, or other cementbased mortar is considered as one of the methods of seismic reinforcement, which belongs to traditional methods and is regarded the most suitable in this case, since it allows seismic reinforcement of buildings constructed from unreinforced masonry, which includes many historical architectural monuments, increasing their load-bearing capacity and at the same time almost without increasing their weight.

Aim. The research is intended to contribute to the seismic reinforcement of buildings, including architectural monuments, built from unreinforced masonry to withstand future seismic impacts from natural phenomena such as earthquake.

Materials and methods. A review and detailed study of the seismic reinforcement method was carried out, namely shotcrete with concrete, which is a traditional method, its advantages and disadvantages, the essence of the method and the sequence of its implementation. A review of historical earthquakes in different countries and their devastating consequences for buildings constructed from unreinforced masonry was also carried out. The in-plane behavior of unreinforced masonry supports and walls under the influence of seismic lateral forces is considered.

Results. The possible practical application and steps of concrete shotcrete over a metal mesh of unreinforced masonry walls for their seismic reinforcement are proposed and clearly demonstrated.

Conclusions. Conclusions have been drawn about the feasibility of using shotcrete over a metal mesh for seismic reinforcement of buildings built from unreinforced masonry, which makes it possible to save the lives of people living in them in case of earthquakes.

Introduction. The construction technical control system evaluates the physical and mechanical properties of concrete on the base of testing a series of samples taken from a batch of concrete. It is necessary to take into account the influence of the control method on the quality of concrete structures and their reliability.

Aim. Creation of a technical control system that should eliminate the causes of the identified risks by reducing the impact of the identified causes.

Materials and methods. The control method affects the reliability of concrete structures being built and is evaluated from the point of view of choosing the number of samples and discarding the minimum strength values in the series. The results of the control of a series of concrete samples for 6 samples selected in such a way as to ensure compliance with the declared class when discarding 2 minimum sample values are compared.

Results. As a result of the analysis of the impact of the methodology on quality and reliability: class B turns out to be 2 steps lower than the prescribed one, the in-series coefficient of variation exceeds the permissible one by 8 %, and the reliability level is significantly lower by 36 %.

Conclusions. The conducted research shows an underestimation of the methodological component of material control, which can leave significant gaps in the system of technical control of construction products and does not allow to ensure the required level of reliability of structures.

Introduction. The corrosion condition of steel reinforcement in reinforced concrete structures and products is the main factor determining their bearing capacity and durability. The alkalinity of the pore liquid of concrete (at pH > 11.8) in reinforced concrete structures and products under normal conditions ensures the passive state of steel reinforcement. In the presence or when chloride, sulfate and other analogous ions enter the concrete, the steel reinforcement of reinforced concrete structures and products depassives, despite the pH value > 11.8, and begins to corrode. In addition, depassivation and subsequent corrosion of steel reinforcement occur during carbonation (neutralization) of the protective layer of concrete due to a decrease in pH < 11.8. One of the promising options for slowing down or stopping the corrosion processes of steel reinforcement is currently the use of migrating corrosion inhibitors.

The aim of the work was to obtain experimental data on the ability of migrating steel corrosion inhibitors to inhibit or completely stop the corrosion of reinforcement in reinforced concrete structures and products initiated by the presence of chloride ions (Cl-) in concrete or neutralization of the protective layer of concrete in relation to steel reinforcement.

Materials and methods. The following types of migrating steel corrosion inhibitors were used for testing:

– Cortec MCI-2020 (manufacturer – KORTEK RUS (KORTEK) LLC, suppliers – Ettrilat LLC, MONUMENT LLC);

– IFKHAN-80 (manufacturer and supplier – IFKHAN LLC);

– Basf Master-Protect 8000 CI (former name Protectosil ® CIT. Suppliers – MBS Construction Systems LLC, MPKM LLC, LKM-FLEET LLC).

The determination of the ability of migrating steel corrosion inhibitors to inhibit or completely stop the corrosion of reinforcement was carried out by accelerated electrochemical research methods in accordance with State Standard 31383-2008 "Protection of concrete and reinforced concrete structures from corrosion. Test methods".

Results. All three types of migrating steel corrosion inhibitors inhibit corrosion of steel reinforcement initiated by the presence of chloride ions in concrete by the age of 90 days. All three types of migrating steel corrosion inhibitors by the age of 30 days do not inhibit the corrosion of steel reinforcement initiated by concrete carbonation.

Conclusions. According to the results of the work, it was revealed that the migrating steel corrosion inhibitors inhibit the corrosion of steel reinforcement initiated by the presence of chloride ions in concrete, while the corrosion initiated by the carbonation of concrete is not slowed down or stopped by migrating steel corrosion inhibitors.

Introduction. The method of concrete strength control based on immersion of a steel dowel into concrete due to the energy of a powder charge has been used since the 60s of the last century. Since the early 2000s, the method has been supplemented by the definition of the dowel pullout force from concrete and the definition of an indirect characteristic in the form of the ratio of the pullout force to the depth of immersion of the dowel.

The object of the present research was a method for determining the strength of concrete based on measuring the depth of immersion and the pulling force of a dowel nail installed in concrete.

Aim: to develop requirements for testing by the proposed method, allowing its use as a non-destructive method for testing the strength of concrete.

Materials and methods. The following research methods are used in this work: analysis of available regulatory documents and technical literature on this issue; collection and analysis of the results of previously conducted research using mathematical statistics methods, development of a research program and assignment of parameters, the value of which must be controlled when performing research; performance of own tests and research; analysis of the obtained results of the performed research using methods of mathematical statistics; analysis of the influence of various factors on the result of research, exclusion of non-influencing factors; development of recommendations for the use of the studied control method.

Results. The limitations for the application of the investigated method and the factors that have the most significant impact on the accuracy of the method are revealed: the power spread of the powder charge, the parameters of the indenter (plugged dowel), the criteria for the quality of the dowel installation; a method for rejecting of low-quality results and processing test results has been developed. The factors that do not have a significant impact on the test results have been identified.

Conclusions. Taking into account the identified limitations, a method has been developed for determining the strength of concrete by the magnitude of the local destruction force of concrete when pulling out a dowel nail immersed in concrete, and proposals have been made for inclusion in the State Standard R "Concretes. Determination of the strength by the depth of immersion of the dowel-nail".

Introduction. In practice, to perform calculations to determine the bearing capacity of reinforced concrete slabs at the stage of cracking, the work of concrete between cracks in the tension zone is taken into account.

This paper presents the results of full-scale tests of damaged precast reinforced concrete floor slabs to determine the coefficients V.I. Murashev – uneven deformations of reinforcement ψ_s in the tension zone and concrete ψ_b in the compression zone for corrosion-damaged slabs in the stage of cracking.

The aim of the work: to determine the coefficients of uneven deformation of reinforcement and concrete experimentally for corrosion damaged reinforced concrete floors at the stage of cracking.

Materials and methods. The article describes the methodology for setting up an experiment to measure the deformations of reinforcement and concrete, slab deflections, crack opening widths, and describes the parameters of the testing installations.

Results. The work presents the main results of experimental studies in graphical form.

Conclusions. Research shows that with the appearance of cracks, the coefficient ψ_sx first increases and then stabilizes. The coefficient ψ_bx immediately after the formation of cracks first increases slightly, then decreases more gradually.

The high level of production quality of electrometallurgical enterprises made it possible to achieve small values of the coefficients of variation of the controlled parameters and introduce a new value into the nominal range of reinforcement classes. In order to launch the production of a new strength class of A550SK reinforcement, studies were conducted to determine the complex of consumer properties. The positive results of the research allowed us to standardize a new strength class, the use of which will allow us to achieve an economic effect by reducing steel consumption.