The results of the study of the grain-size composition and the grade of crushability of recycled crushed stone and their dependence on the strength of the original recycled concrete are presented. It is found that recycled crushed stone obtained from the original concrete of classes B10 - B30 does not meet the reguirements of GOST 8267-93 for total residues on 025, 020, 05 and 02.5 sieves. Regardless of the strength of the original concrete, the main fraction of recycled crushed stone is grains with sizes from 12.5 to 20 mm. The strength (grade in terms of crushability] of the recycled crushed stone increases with an increase in the strength of the original concrete. The study of the main parameters of recycled crushed stone at the current moment has been carried out in an insufficient [for widespread introduction into production) volume and requires further study for the subsequent development of independent regulatory and technical documentation [or additions to the current regulatory and technical documents).

Research work was carried out at NIIZHB named after A.A. Gvozdev, one of the tasks of which was to study the influence of the conditions for stiff fixing supports on the parameters of the effective lengths of reinforced concrete columns with sguare and rectangular cross-sections assigned when calculating the strength of normal sections. As part of the study, the influence of different values and directions of the angles of rotation of the fixing and their displacements was evaluated. The conducted computational and theoretical studies based on the analysis of experimental data showed that the method of determining the effective lengths, adopted in domestic standards, can be improved. Based on the results of the research, proposals were formulated to take the results of the work into account in the current regulatory framework. Taking into account the peculiarities of the conditions for fixing the structures considered in the work, which correspond to the nature of the work of monolithic columns and pylons, it is recommended to include the provisions of the proposed methodology in SP 430.1325800.2018, which applies to monolithic structural systems of buildings. The prepared proposals for the calculation are supposed to be included in the current regulatory documents as one of the possible options for determining the effective length of non-centrally compressed elements when calculating their strength.

The information about the new national standard GOST R «Self-compacting concrete mixtures. Specifications», developed by the «Research Institute for Concrete and Reinforced Concrete» named after A.A. Gvozdev, of JSC «Research Center of Construction», is presented. The standard applies to ready-to-use self-compacting concrete mixtures of heavyweight, fine-grained, light-weight and reactive powder concretes, as well as fiber reinforced concretes, for the production of monolithic or precast concrete structures and products, the shape and reinforcement of which makes it difficult to place and compaction of an ordinary concrete mixture. The standard establishes new terms and definitions, types and designations, uniform reguirements for new technological characteristics (slump-flow, segregation, viscosity and flowability), acceptance rules and test methods, production and transportation processes, control and evaluation procedures conformity of guality indicators of self-compacting concrete mixes.

The article presents examples of the use of ultra-high performance fiber reinforced concrete for load-bearing structures in Russia. Using this material with limits of compressive strength 150 MPa, flexural tensile strength 21 MPa, tensile strength 8.5 MPa, external post-tensioned structures of bridges and tanks are made instead of common solution with the steel anchors. Full-scale tests of anchors were carried out, which did not reveal signs of deformations and destruction of elements during the tension of strands, at the level of design and ultimate loads - before strands rupture. It was concluded that it is advisable to replace steel anchors with anchors from the material, which, with high strength characteristics, has ultra-low permeability and high frost resistance corresponding to the F21000 class. The estimated economic effect of such a replacement is determined by the reduced cost of these elements of structures made of ultra-high performance fiber reinforced concrete in comparison with steel.

The article presents information about the changes made to the code of rules for the design of concrete structures reinforced with polymer composite reinforcement. New rules for the formation of relative deformations at the base point of a two-line diagram of concrete under axial tension, used to calculate reinforced concrete elements for the second group of limit states, are described. The rules for calculating re-reinforced structures of T-or I-beam cross-sections with a shelf in a compressed zone by the method of limiting forces are presented. The rules for taking into account the inelastic properties of concrete of the stretched zone when determining the elastic-plastic moment of resistance for the extreme stretched fibre of concrete with a rectangular cross-section and a T-shape with a shelf located in the compressed zone are clarified.

The impregnating compositions for increasing the strength of concrete surfaces are analyzed, standard methods for testing the physical and mechanical properties of concrete after its impregnation are considered. The need fora uniform classifier and methodology for assessing the quality of impregnation of concrete with various reinforcing materials has been pointed out.

In construction, thin-walled reinforced concrete spatial structures are used both for unique roofs of large-span buildings and for mass buildings of the pavilion type and small architectural forms. The most serious obstacle to the widespread application of economical thin-walled reinforced concrete structures is the shortcomings of the technology used for the manufacture and installation of prefabricated shell elements. The method of bending just formed flat flexible plates to give them a curved shape is one of the most promising technological methods that allow you to abandon the use of expensive metal forms of complex curved outlines, significantly simplify all production processes. The article describes the experience of research and development of structural decisions for spatial structures of building roofs with the use of unified rhombic elements made by the method of bending a flat just formed sheet on a flexible formwork.

Experience in applying the standard 10060-2012 ‘Concrete. Methods for determining frost resistance'shows the need to adjust the methods for determining frost resistance of concrete. Based on the performed by NIIZHB named after A.A. Gvozdev of research on frost resistance of concrete by the third accelerated method of GOST 10060, experimental data were obtained to clarify the freeze-thaw regime of concrete samples and the criterion for evaluating frost resistance by ultrasound speed.

The results of studies of porosity, water absorption, moisture shrinkage and frost resistance of cellular concrete, which are some of the main factors determining the durability of cellular concrete enclosing structures manufactured using autoclave hardening technology, are considered. Methods for determining water absorption, moisture shrinkage and frost resistance are presented. The relationship between the moisture shrinkage and the capillary forces (the sum of the surface tension forces on the micromeniscs of liquid in the capillaries of cellular concrete], as well as the dependence of the shrinkage on the size (radius] of the capillary and gas pores of cellular concrete and on the water-solid ratio (W/S-factor) of cellular concrete, is established. In the field of frost resistance of cellular concrete, the relationship between the structure of the pore space of concrete and its deformation characteristics under the action of negative temperatures is studied. The effect of the presence of gas pores in cellular concrete on the reduction of frost expansion deformations is described.

The article presents the results of studies of the fatigue strength of A500 class reinforcement by GOST 34028-2016 with various types of periodic profile. The data on the results of previously conducted experimental studies of the fatigue strength of various types of reinforcement are generalized and systematized, and the main factors affecting fatigue are established. Experimental data on strength and deformation characteristics under static and high-cycle loads of A500C class reinforcement with various types of periodic profile have been obtained. Based on the research results, proposals were made to improve the characteristics of the reinforcement and the periodic profile to increase its resistance to repeated cyclic loads and to amend the current regulatory documents.

In world practice, self-compacting concrete is increasingly used due to its unique properties and advantages. Self-compacting concrete mixtures have high ductility, better fluidity, high density with tow water content due to the use of special effective minerai and chemical additives that provide high performance for concrete. The rheologicat properties of SCC differ significantly from those of conventional concrete. In this regard, when designing the composition of concrete and controlling its quality in laboratory and production conditions, several methods for controlling the quality of a self-compacting concrete mixture were created. The purpose of this standard was to create a single regulatory document regulating the assessment of the quality of a self-compacting concrete mixture. Concrete from a self-compacting mixture can be used for underground and hydrotechnicai construction for the erection of structures of large length, complex geometric shape and densely reinforced structures.

With the development and simplification of The article describes the application of European norms in the domestic practice for the design of reinforced concrete structures using European norms Eurocode-2. For Eurocode-2, the number of nationally defined parameters is more than a hundred. These are different coefficients, shrinkage, creep of concrete, thickness of protective layers of concrete for steel fittings depending on the type, environment of operation, etc. Differ in the SNIP on the design of designs and individual Eurocodes, the size and shape of the samples tested to determine the strength (regulatory] characteristics of building materials, making it impossible to apply many of the calculation formulas directly. Addressing these issues is a rather capacious task. Many series of prototypes will be reguired only to determine statistically reliable transitional coefficients for the strength of the materials used in SNIP and Eurocodes.

The article is devoted to understanding the place, role and functions of science in the modern world. The author analyzes the process of development of science from the initial individual forms of organization of scientific activity to its transformation into a social institution. The specifics of the process of cognitive and social institutionalization of science are considered. The main conditions for the development of science in the status of a social institution are revealed. The close connection of science with political, economic and social institutions and also the possibility of its development with the state regulation are shown.