The RPP introduction has been established up to 3% by weight of the dry concrete mix is ​​accompanied by a decrease in the fine-grained concrete tensile strength in compression to 40% and in tension during bending to 15%. The relationship between the tensile strength limit in bending and compression for the studied materials is invariant to the cement and RPP type. With the concrete tensile strength in tensile bending increase, there is a weak tendency to a decrease in the adhesion ratio value to the concrete base and tensile strength. The adhesion amount to the concrete base with RPP increasing dosage can either increase or decrease after a certain limit, depending on the cement properties. The maximum increase in adhesion to the concrete base was 37%, while the decrease in the concrete elasticity initial modulus was 26%.

Objectives. The aim of this study was to identify variation patterns of the in-series variation coefficient of adhesive strength to base and the dependency of the frost resistance coefficient on the criterion of adhesion on prescription factors of fine-grained concrete obtained from dry building mixtures based on various Portland cements containing various low-modulus inclusions and redispersible polymer powders from 0 to 3%. According to GOST 31357, the main quality indicators of the hardened mixture or fine-grained concrete, in addition to frost resistance, include the indicator of “frost resistance of the contact zone”, which characterises the ability of the hardened concrete to maintain adhesion to the base during normal separation following a certain number of freeze-thaw cycles.Method. The tests of the main samples were carried out after 75 freeze-thaw cycles in accordance with GOST 31356. The marks of the frost resistance of the contact zone are set from FKZ25 to FKZ100. The number of freeze-thaw cycles is taken as a mark, after which the adhesion strength to the base, determined according to GOST 31356, is at least 80% of the strength of the control samples. The arithmetical average is taken at between at least 5 values, while the variation coefficient measured across a series of adhesion strength values is not considered.Results. The average values of the variation coefficient of adhesion strength were: following 75 cycles of freezing-thawing – 0.224 (in a range from 0.058 to 0.616); following 25 cycles of freezing-thawing – an average of 0.129 (in a range from 0.016 to 0.352). The variation coefficient of adhesion strength can exceed the variation coefficient of compression strength by approximately 2.5 to 3 times. When introducing the redispersible powders into the structure of fine-grained concrete, there is no unambiguous pattern of change in the values of the variation coefficient of adhesion to base and it is possible to increase or decrease this value, while the values of the variation coefficient of adhesion can vary by an order of magnitude.Conclusion. For all concretes, there is a tendency of increase of the coefficient of frost resistance with a decrease in the adhesion variation coefficient both after hardening under normal conditions as well as during cyclic freezing and thawing. When conditions VF/V28A<1 are met, the coefficient of frost resistance of adhesion, determined when considering the variation coefficient, will satisfy the requirements of GOST 31356.

Objectives Reliability and durability of structures using materials with various properties (plaster coatings, cement glue, new concrete during repair and restoration of structures, etc.) largely depends on the adhesion of the layers and the deformation properties of the coatings. To obtain the required properties of materials used for coatings, modifiers based on polymers and low-modulus inclusions are introduced into the composition of new concretes, for example, entrained air. The aim of the work is to identify some patterns of change in the properties of concrete with the joint introduction of these modifiers.Method Experimental determination of the tensile strength in bending, compression, E-modulus, adhesion to the concrete base by standard methods.Result The influence of separate and joint introduction of dispersible polymer powders and various low-modulus inclusions into the composition of fine-grained concrete has been established.Conclusion The joint introduction to the composition of fine-grained concrete of various low-modulus inclusions and redispersible polymer powders provides a reduction in the stress level during forced deformations due to the different effects additives on the strength and deformation properties and contributes to increased adhesion to the concrete.

Objectives This study was aimed at identifying the dependency of the frost resistance of the contact zone of fine-grained concretes (FGCs) obtained from dry building mixtures (DBMs) based on various Portland cements (PCs) with the content of various redispersable polymer powders (RPPs) from 0 to 3%.Method The research was based on 75 freeze-defrost cycles.Results Although the average dependency of adhesion with the base on additional porosity after 75 freeze-defrost cycles does not depend on the nature of NMV, adhesion is influenced by the cement type, the type and dosage of RPPs, as well as the nature of additional porosity. Since the content of organised volume of NMV in the form of VV has no effect on changes in adhesion with the concrete base following 75 freeze-defrost cycles, it is impractical to add more than 7% of NMV in the form of MS to the concrete mixture. The feasibility of using sulphate-resistant cement requires more research. The practical RPP dosage should be 1-2%. Some contradictions in conclusions on the volume of the introduced MS (by the strength criterion – at least 6%, by the criterion of frost resistance of the contact zone – no more than 7%) allows us to recommend the dosage of MS in RPP within 6-7% by volume for obtaining additional data on the MS effect on frost resistance.Conclusion The dependency of compressive strength on additional porosity for FGCs without NMV and with NMV in the VV form after hardening during 28 days under normal conditions almost coincides with the known dependency of strength on porosity for cement stone; the maximum divergence of the values ???????? ????0 in the investigated range does not exceed 5%. The dependency of compressive strength on additional porosity for FGCs without NMV and with NMV in the MS form is similar to the known dependency of strength from porosity for cement stone; however, with increasing porosity, there is a slight decrease in the effect of porosity on strength. The dependency of compressive strength after 75 freeze-defrost cycles on additional porosity for FGC without NMV practically coincides with the previously obtained dependency of strength on porosity for cement stone; the maximum divergence of the values ???????? ????0 in the investigated range does not exceed 9%. For FGCs with NMV in the MC form, increasing porosity causes a slight decrease in the porosity effect on strength, and for FGCs with NMV in the VV form, the dependency has a quantitative and qualitative difference. The value of NMV in the VV form recommended for improving the frost resistance of FGCs by the strength criterion is at least 3%, MS – at least 6%. According to the criterion of the frost resistance of the contact zone and the strength of MS, the recommended dosage is 6-7%. It was not possible to disclose the direct impact of the VV volume on the frost resistance of the contact zone.

The paper discusses the development of an expert system for diagnosing electric traction motors of rolling stock. The diagnostic parameters of the electric traction motor commutator-and-brush assembly, being the input linguistic variables of the fuzzy model, were selected with the use of graphoanalytic model. A fuzzy mathematical model and a fuzzy neural network for comprehensive indicator of quality of mechanical machining implementing the Takagi — Sugeno fuzzy inference algorithm were developed. The authors confirmed the practicability and the adequacy of the previously proposed comprehensive indicator of quality of mechanical machining for assessing the technical condition of the electric traction motor commutator-and-brush assembly. The studies carried out allowed creating an element of intelligent expert diagnostics system that enables a comprehensive assessment of technical condition of electric traction motor.