Research studies of polymer concretes are frequently carried out under the action of static loads while the material is affected by cyclic loads, most often, low-cycle as a result of its work in the structure. In the case when the level of stresses caused by these loads exceeds a certain limit, irreversible damage accumulation processes begin to occur in the material, which lead to the formation of cracks. In the future, the stress concentration at the edge of the crack contributes to its development. Most often cracks occur at the surface of the part, but sometimes in the thickness of the material. This process weakens the section and after some time, when the crack reaches a critical length, the part or structure is destroyed. As a rule, they are destroyed without visible residual deformations, even in cases when they are made of plastic materials. It was suggested that under the influence of variable stresses material gradually degenerates over time, as if "gets tired" (fatigued). Material fatigue is a process of gradual accumulation of damage under the influence of variable stresses, leading to the formation of cracks and destruction of the material. The peculiarities influencing low-cycle stresses on strength characteristics of polymer concretes based on furfural acetone monomer (FAM) are considered in the article. The regression equation has been obtained as a result of experimenting on a polymeric composite material which allowed constructing the response surface of the low-cycle fatigue of the polymeric composite material based on the resin of furfural acetone monomer. A second-order plan for three factors studying low-cycle fatigue of a tested composite material is also presented in the paper. It has been established that the ratio of the polymer component to the filler and the coarse aggregate spreading factor are the fundamental ideas influencing the cyclic durability of polymer concretes while the thickness of the polymer bonding layer is an insignificant factor.

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To determine the deformability parameters of concrete samples by the formulas of fracture mechanics, equilibrium tests were carried out at the stage of local deformation of the sample, which showed the correspondence of the change in external forces to the internal forces of the material resistance with the corresponding static development of the main crack. For the same purpose, the samples are tested for bending with an initial notch and the “load-deflection” diagram is recorded. In this work, we presented a test scheme for a specimen with a notch (crack) and constructed a diagram of the deformation of a specimen under bending “load-deflection”. Based on it, it is possible to predict the destruction of the material, that is, to determine the value of the load at which the limit value of deflection or the displacement of the outer edges of the notch (opening the throat of the crack on the lower surface of the specimen) can be taken as the moment of loss of the resource of the material. Also, we examined the deformation of a concrete sample during three-point bending and presented a diagram of the deformation of a concrete sample within the plastic zone. Dependencies were derived for determining the ultimate relative strains under tension and bending. Based on the results obtained, the state diagrams of the stretched concrete and the deformation scheme of the normal section of the concrete sample were constructed. As a result, the conclusion and convergence of the results.

Movement joints are one of the most important structural elements of bridge structure and represent gaps between end face of span structure and cabinet wall of support or head part of support. The durability of the structure as a whole depends largely on the correct choice and, then, the installation of the movement joints. The results of numerous technical surveys of bridges and overpasses show that the main defects and damages of movement joints structural elements are: weld structure disorder due to incorrect selection and installation; Formation of cracks in the zone of seams on the coating of different length and with different opening width. In addition to the above-mentioned defects, the formation of gauge due to differences in the marks of the bridge web at the joint of the road clothes and the movement joints plays a major role in the process of breaking the coating in the zone of movement joints. Destruction of coating in zones of movement joints in many cases is due to intensive gauge formation, at the same time, formation of wheels is due to difference of marks of road clothes and movement joints. To prevent colour formation in the zone of movement joints the following technical solutions are used: arrangement of pedestrian zones; Application of concrete tides (boundaries). In these zones it is recommended to arrange tides on the basis of polymer composite materials (PCM), having high damping properties and cyclic durability. Endurance tests and the study of damping properties were carried out according to conventional methods for polymer betons FAM and FAZIS-30. The values of the vibration decree for the above-mentioned materials and their cyclic durability are obtained.

The results of experimental-theoretical work on the creation of new polymeric materials based on wood waste are considered. This material can be used in the outer layers of a wood-based polymer fiberglass composite in order to increase its strength properties. Instantaneous elastic moduli, conditional tensile strengths, and Poisson's ratio were determined, and the potential chemical activity of the components of the wood-based polymer fiberglass composite was revealed. The fiberglass polymer composite on the furfural-acetone monomer showed good performance when used as a structural composite of containers for storing aggressive liquids, chemically resistant tiles for shop floors, etc., which are exposed to electric current, aggressive liquids, and temperature. This material can be used in wood chemical production, capacities of energy chemical plants, furfural production, as well as in the outer layers of wood-based polymer fiberglass composite in order to increase its strength properties, specifically crack resistance. The basic compositions of the polymer fiberglass composite and its basic regulatory mechanical characteristics are given. This development is a kind of continuation of the theme of the use of forest industry waste for the production of competitive composite materials. This material will allow to utilize a huge amount of forest industry waste. In addition, the use of wood waste as a building material will make it possible to replace wood in some areas, which in turn will reduce logging and increase woodworking efficiency. All this will undoubtedly lead to an improvement in the ecological situation.