The thesis is devoted to experimental and theoretical studies of concrete structures working in bending, with hybrid reinforcement of basalt plastic and steel bar, made of various concrete mixes.The purpose of the thesis is the research of the stress-deformed state; the influence of differences in the mechanical properties between basalt plastic and metal bar on the nature of destruction, strength, stiffness and crack resistance of beams with hybrid reinforcement, basalt plastic and steel bar, made of different concrete mixes; verification of the available calculation methodology; checking the possibility of using the waste of the Mining and Processing Complex as a fine concrete aggregate for beams reinforced with basalt plastic bar and with hybrid reinforcement. In order to fulfill the set aim, the stress-deformed state, nature of destruction, strength, opening width of normal cracks and deflections of beams with hybrid reinforcement with basalt plastic steel bar were experimentally investigated; a check of the convergence of test results with theoretical calculations using the methodology of current norms [1, 2] was performed; recommendations have been developed for the existing methodology for calculating the strength, opening width of normal cracks and deflections of structures working on bending.The introduction contains a general description of the thesis, the relevance of the work is substantiated, the aim and task of the research, the scientific novelty and practical value of the work are formulated.Manufacturing, physical and mechanical characteristics, advantages and disadvantages of basalt-plastic composite reinforcement are considered in the first chapter. The experience of using this bar for reinforcing concrete structures in the USA, Europe, Canada and other countries is considered. The impact of iron ore beneficiation waste on the environment and the possibilities of their use in concrete mixes is considered. The advantages of concrete mixes made of iron ore beneficiation wasteconcrete, in comparison with traditional concretes and their effect on the stress-deformed state of structures, are indicated.Normative documents for the calculation of concrete structures working in bending, reinforced with non-metal composite reinforcement, developed in the USA, Europe, Japan, Canada, and Ukraine are listed.In order to determine the physical and mechanical characteristics of the concrete of the experimental beams, samples of cubes and prisms of concrete were made and tested on quartz sand and sized iron ore beneficiation waste in accordance with the requirements of current standardsand described in the second section. The structure of beams test samples with steel, basalt plastic bar and hybrid reinforcement, i.e. steel and basalt plastic bar, is provided. The program of experimental research is described: the number of beams, the test scheme, the design of the stand, the installation of devices, the sequence of applying loads and the data obtained as a result of the tests.The third section presents the results of experimental studies of beams of all series: crack formation moments, destructive moments, beam fracture pattern, graphs of changes in deflections and relative deformations, comparison of the obtained experimental data.The calculation method of structures working in bending according to the first and second groups of limit states is described in the fourth chapter. Algorithms for calculating the strength of sections normal to the longitudinal axis of the element, crack resistance of elements, deflections of elements are provided.The calculation of test samples of beams was performed according to the methodology of current standards. For the beams of all series, the comparison of experimental indicators with those obtained by calculation according to the second group of limiting states showed an unsatisfactory convergence. As a result of the data analysis from experimental studies, proposals were developed for the current method of calculating beams for crack resistance and deformability. The opening width of normal cracks and the number of deflections when calculating beams are proposed to be determined using the effective moment of inertia, which does not take into account the work of concrete in the stretched zone. A comparison of theoretical and experimental data showed a satisfactory convergence of the obtained results.The effectiveness of the use of the iron ore beneficiation waste as a fine aggregate in the concrete mix for beams reinforced with basalt plastic bars and for beams with hybrid reinforcement has been proven.The general conclusions summarize the work carried out and describe the main results obtained in the study.The thesis is supplemented by appendices, which contain the acts of implementing the thesis research and the patent for the invention.
