# Strengthening Polymer Concrete with Carbon and Basalt Fibres
## 1 Introduction
A similar work on the basalt fibre addition shows that the optimum reinforcement percentage in terms of increasing compressive strength is 1%. This basalt fibre content not only improves strength properties, but also reduces drying shrinkage by 31.6% [12]. A large work performed by the authors on the analysis of the influence of basalt fillers on the properties of concrete and polymer concretes shows the main trends and opportunities in improving the performance properties by means of basalt fibres. According to [13], adding basalt fibres to any type of concrete increases its bending strength and tensile strength. However, the addition of basalt fibres does not always result in an increase in compressive strength. The optimum percentage in terms of increasing the compressive strength of ordinary concrete by the basalt fibre reinforcement is between 0.05 and 0.15%. The maximum increase in bending and tensile strengths of ordinary concrete occurs when basalt fibres are added in the amount of 0.5-1%. This review shows that the effect of adding reinforcing fibres depends significantly on the concrete composition and the shape and size of the fibres themselves. In some cases, the maximum increase in properties (bending and tensile strengths) is achieved when adding 2-4% of basalt fibres. The optimum length of basalt fibres used for the reinforcement is usually 10-20 mm. The combination of different types of fillers also shows good results. In addition to basalt fibres, carbon fibres are a promising filler. These conclusions are largely confirmed by the authors of [14; 15]. At the same time, they say that an optimum ratio between an aggregate and a binder is often chosen experimentally. At the same time, the aggregate of such granulometric composition is used, which provides the minimum hollowness of the aggregate mixture. For each specific type of the aggregate, there is a different optimum ratio between the amount of the binder, aggregates and a reinforcing agent. Most of the works on the use of reinforcing admixtures based on basalt fibre are devoted to the reinforcement of conventional concretes. But the works, devoted to geopolymer concretes [16; 17; 18; 19], show similar results. The conclusions on the results of the works largely repeat the conclusions presented earlier in [13]. A further increase in polymer concrete properties can be achieved by using carbon fibre. In comparison with basalt fibre, carbon fibre is more expensive; however, some works show that it is possible to obtain a greater increase in compressive strength when using it [20; 21; 22]. In this research work, the authors focused on studying the strengthening mechanisms of polymer concrete by integrating basalt and carbon fibres of various lengths. The aim of the study is to identify an optimum configuration and properties of fibres that can significantly increase the strength properties of the composite material. Based on previous scientific data and theoretical assumptions, we assumed that the inclusion of carbon and basalt fibres in the structure of polymer concrete improves its strength and deformation parameters, enhances the bond between the matrix and reinforcing elements, and increases resistance to mechanical loads and environmental impacts. In particular, the strengthening process can be realised due to the enhancement of cohesive and adhesive forces at the fibre-matrix interface. At the same time, the analysis of previous works shows that the optimal percentage of reinforcement with carbon and basalt fibres can vary from 0.3 to 2.5%. In a small number of works, a positive effect is given by the addition of 3-4% of fibre. The amount of added fibre and its effect largely depends on the composition of polymer concrete. Therefore, in many ways, to determine the optimal amount of reinforcing additive for each composition, it is necessary to conduct their own studies. In previous works of the authors [10; 23; 24], an attempt was made to replace the metal material of the pump body with polymer concrete. In this paper, we continued this work.