The results of the analysis and monitoring of normative and technical documents (NTD) in the field of design and construction of mechanical butt joints of high factory readiness for precast concrete and reinforced concrete structures of buildings are presented. The normative documents regulating the requirements in the field of design and detailing of mechanical butt joints of high factory readiness, including an analysis of the regulatory, methodological and technical documents available both in our country and abroad, are considered. The shortcomings of regulatory documents are analyzed: repeated technical requirements, references to canceled NTDs, contradictions in various standards of requirements for structures. Proposals were formed on the feasibility of performing additional scientific research work in the form of RW and R&DW, as well as proposals for updating existing and developing missing BS and standards in the NTD system.

On the basis of the analysis of experimental studies, brittleness criteria for high-strength concrete at high temperatures are proposed and their threshold values are recommended, which are determined by the developed method for concrete at t = 20 °C. The brittleness criteria for high-strength concrete at high temperature for operational structures are determined on the basis of the dependence of the elastic modulus E and the critical stress intensity coefficient K_IC on the surface hardness H. On the basis of the experimental data obtained, the value of the surface hardness (at t = 20 °C) of high-strength concrete H > 450 MPa is proposed, when heated, brittle fracture will occur.

The new state standard GOST R “Concretes. Acoustic emission control method”, which establishes methods for monitoring concrete and reinforced concrete products and monolithic structures in order to assess damage and early diagnosis of the formation and development of operational (power) cracks by acoustic emission (AE) method, is considered. Unlike traditional methods of non-destructive control and technical diagnostics, the AE method does not require scanning the surface of an object to search for defects, the source of information is the defect itself. Damages are detected long before the onset of the limit state, which makes it possible to plan preventive measures for preventing accidents.

With the development of 3D printing technology in construction, the development of effective building materials with specified performance properties for extrusion molding is becoming increasingly relevant. The article presents the results of the study of the influence of two prescription factors on the properties of light concretes on hollow microspheres by means of mathematical planning of the experiment. Experimental and statistical models describing the dependences of changes in the mobility of the concrete mixture, average density, bending strength, compression and shrinkage deformations of light concrete on the content of a solution of superabsorbing polymer (SAP), which provides hydration of Portland cement under unfavorable hardening conditions, and a dispersed reinforcing additive-polypropylene fiber, are obtained. The optimal ranges of fiber and SAP content were established, which are (in %): C_FєI[1.19; 1.38] and C_SAPєI[0.81; 1.25], respectively. The composition of light concrete on hollow microspheres, containing 1.25 % fiber and 1.25 % SAP, has the best physical and mechanical properties.

On May 27–28, 2021, Gelendzhik hosted the II RUCEM Conference «Open Dialogue of Cement Makers, Manufacturers of Construction Chemicals and Concretes», which is traditionally organized by the online magazine about cement RUCEM.ru and «GK POLYPLAST» JSC with the information support of the industry media and the National Association «Union of Concrete Manufacturers».

The optimum compositions of fiber-reinforced concrete with glass-polymer composite fiber of compressive strength classes B20, B40 and B60 have been developed. Their complex studies demonstrate that based on concrete mixtures with an average density of 2320–2360 kg/m³, air entrainment of 2.5–3.5 %, and workability (slump) of 21–22 cm, the concrete with the following properties can be obtained: average compressive strength of concrete – 28, 54.7 and 83.3 MPa; the average bending tensile strength – 3.5, 4.4 and 5.6 MPa; the breaking strength – 2.92, 5.78 and 6.92 MPa; prismatic strength – 20.1, 40.4 and 60.4 MPa; modulus of elasticity – 35393, 46146 and 51366 MPa; Poisson’s ratio – 0.17, 0.18 and 0.18, respectively. The addition of glass-polymer composite fiber into concrete mixtures in an amount of 0.5, 1.5 and 2.5 % vol. slightly reduces the average density of the mixture by 7–72 kg/m³, increases the air content of mixtures by 0.1–0.6 %, reduces slump by 3–8 cm, and has little influence on the compressive strength. The data on the ultimate bending tensile strength at the moment of crack formation, as well as residual bending tensile strength corresponding to the crack opening in the range 0.5–3.5 mm, were obtained. The shape of a single fiber surface was the determining factor when it broke out of concrete matrix. Three main types of deformation mechanism were identified. The characteristics of fiber-reinforced concrete durability were determined. Overall, the results indicate that fiber-reinforced concrete can be produced with properties that are suitable for wide application.

The methodological manual “Calculation and Construction of Concrete and Reinforced Concrete Pressure-free Pipes” is developed in the development of the provisions of SP 63.13330.2018 “SNiP 52-01–2003 Concrete and Reinforced Concrete Structures. Basic Provisions”, which establishes general requirements for the calculation and design of reinforced concrete structures, and SP 35.13330.2011 “SNiP 2.05.03–84* Bridges and Pipes” in terms of the calculation and design of concrete and reinforced concrete non-pressure pipes used in outdoor underground drainage and sewerage networks. The manual contains recommendations for the calculation and design of non-pressure concrete and reinforced concrete non-stressed pipes with a round hole, taking into account their design features and operating conditions in non-pressure pipelines mounted by the open (trench) method and closed (trenchless) microtunneling method. The theoretical provisions, engineering methods and recommendations set out in the manual are illustrated by a number of detailed examples of determining the loads on pipes and internal forces in the structure, designing and calculating concrete and reinforced concrete pipes according to the limit states.