###### Abstract
The advantages of such fibers for dispersed fiber reinforcement of concrete are high tensile strength that meets the requirements of modern construction, low cost, no need for energy-intensive production with high CO\({}_{2}\) emissions into the atmosphere, renewability, low waste production, and relative safety for humans and animals. Several studies were carried out [18,22], during which it was found that the addition of various types of plant fibers to concrete improved its strength properties and affected its deformation properties, making the destruction \"smooth\" instead of brittle such as ordinary concrete. It was revealed that the addition of the listed types of plant fibers in an amount up to 2 % _vol._ of concrete increased the SC in direct proportion to the percentage of fiber reinforcement, and when this value was exceeded, an inverse relationship was observed [18,22]. Coconut fiber, which is a by-product of coconut processing, has attracted special attention in this regard. The structure of the coconut palm fruit is shown in Figure 1.  
Coconut fiber (coir) is originally a part of the fruit of the coconut palm, namely, the fibrous shell surrounding the endocarp (the so-called coconut), which protects the seed from overheating and provides buoyancy to the fruit [25, 26, 27]. Coir is obtained from mature fruits of the coconut palm and contains a large amount of lignin,  
Figure 1: Schematic of the fruit of the coconut palm. rot and has high strength and elasticity [28; 29; 30]. It consists of lignin (45.77%), cellulose (43.24%), water-soluble components (5.22%), pectin (3.30%), ash elements (2.22%), and hemicellulose (0.25%) [31; 32; 33]. The schematic of coconut fiber is shown in Figure 2.  
Coconut fiber consists of four layers: the main and three inner walls surrounding the cavity in the center. The wall mainly consists of lignin and cellulose, which are the main components of coconut fiber, which are arranged in a helical pattern with different angles of inclination to the fiber axis [34; 35; 36; 37]. The study [38] investigated the properties of concrete with the inclusion of coconut shells and coconut fibers. The water absorption of concrete, the volume of permeable pore voids, the permeability of chloride ions, and the sorption capacity and resistance at elevated temperature were studied. The samples were cured under three different conditions: full immersion in water, curing under normal conditions, and curing at low humidity. The samples tested for temperature resistance hardened only under conditions of immersion in water. The study showed that the SC of conventional concrete with dispersed coconut fiber reinforcement were better when cured under water immersion conditions, and the performance of concrete with the addition of coconut shell was higher when cured under normal conditions. Temperature resistance tests have shown that all the studied compositions have the required minimum characteristics and are safe for construction [38; 39]. The study [40] considered the impact of the length of coconut fibers and the percentage of their content in concrete on high-strength concrete properties. Coconut fibers had a positive effect on the strength in compression and tension, flexural strength, and deformability of high-strength concrete compared to a similar composition without coconut fibers. The optimal values for the length of coconut fibers and the percentage of fiber reinforcement for high-strength concrete, namely, 50 mm and 1.5% by weight of cement, respectively, have been identified. In [41], the possibilities of recycling industrial and agricultural wastes as additives in asphalt concrete and bitumen were studied. Additives in the form of coconut and sisal fibers substantially enhanced the mechanical properties of asphalt concrete and increased the elasticity modulus of the material. The study [29] is also part of the data on the efficient use of natural fibers in the form of coir and waste in construction.