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Introduction. The actual problem of improving the methods of experimental studies of the properties of fibre-reinforced concrete obtained using various types of fibre is considered in the article. As a result of the analysis of the technical literature, some shortcomings of the existing test methods of one of the most important characteristics of fibre-reinforced concrete, crack resistance, were revealed. The aim of this study is to develop methods for determining the fibre-reinforced concrete crack resistance parameters. Materials and methods. The GOST 29167 standard is used as a basis for the development of a new method and device. Regulations of this standard pursue an aim of obtaining the most informative data about the material by plotting the dependences of test specimen deflections on the applied loads and determining with their assistance the power and energy parameters of the crack resistance. The test samples are presented by fibre-reinforced fine concrete beams made using steel wire fibre of circular cross-section and wave profile. Diagrams of the dependences of sample deflections on applied loads were plotted in the course of the tests for tension in bending. Calculations of power and energy parameters of crack resistance were conducted. Results. The device and method of testing the fibre-reinforced concrete crack resistance are developed and proved. A comparative analysis of the results of tests of steel fibre concrete samples is made. Conclusions. The proposed device and method allow researching influence of the fibre reinforcement parameters on fibre-reinforced concrete crack resistance parameters quickly and with minimal labour expenditures for preparation and tests. Increased adequacy of the obtained data promotes building up new trends in research and rapid introduction of fibre-reinforced concrete in the construction industry. As a result of the analysis of the obtained data, it is established that the proposed device and method can be recommended for research of the influence of fibrous reinforcement parameters on the obtained fibre-reinforced concrete properties and accumulation of statistical data for the development and improvement of normative and technical documents.

Introduction. The purpose of the article is to determine the influence of the steel fiber profile and the composition of the matrix on their adhesion in dispersed reinforced concrete.Materials and methods. Studies have been carried out using the test methods set out in national standards. To determine the characteristics of the adhesion strength of fibers with a matrix, an original technique developed at SPbGASU was used.Results. The degree of influence of the geometric shape of steel fibers – anchor and wave profile on the adhesion strength characteristic is determined. The adhesion strength of steel fiber with cement and concrete matrix was assessed (Cement: Sand = 1:1, Cement: Sand = 1:2 and Cement: Sand = 1:3). The influence of the volume fraction of the cement paste on the characteristic of the adhesion strength of the steel fiber with the matrix has been experimentally proven.Conclusions. The experimental data obtained confirm the effectiveness of dispersed reinforcement through the use of anchor fibers in combination with a rationally selected composition of the concrete matrix.

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In this work was carried out a study the purpose of which was the development of physical and mechanical modeling of the processes of deformation and destruction of fiber-reinforced concrete. The process of deformation and the mechanism of destruction of fiber-reinforced concrete reinforced with low-modulus polypropylene fibers have been investigated. The method has been improved and the characteristic of adhesion of polypropylene fiber to the matrix has been determined. Theoretical models for forecasting the behavior of fiber-reinforced concrete reinforced with polypropylene fiber under load have been developed.