###### Abstract
The addition of 1% and 1.5% coconut fiber, as well as 1.5% mineral wool to the mortar, led to an improvement in its flexural strength and an increase in durability [29]. Research [42] in the field of fiber-reinforced concrete with experiments, numerical modeling, and microstructure study once again confirmed that a high dosage of fiber can adversely affect the compressive strength, which can also lead to a change in the microstructure, an increase in pore volume, or non-large increases or decreases in bulk density. A very positive effect of the use of fiber was confirmed by experiments with reinforced concrete beams without transverse reinforcement, with tests performed for various spans and sections [42]. In some studies [43; 44; 45; 46; 47; 48; 49], the properties of concretes with coconut fiber as a dispersed reinforcement and various production wastes as coarse aggregates and additives were studied. According to the results of the research, it was revealed that construction waste in the form of crushed concrete can act as a partial  
Figure 2: Schematic of coconut fiber. substitution for coarse aggregate without losing the quality of concrete, and additives in the form of fly ash, coconut fibers, and other materials improve the deformation and strength properties [43; 44; 45; 46; 47; 48] as well as the fresh and long-term properties [47] of such concrete. In [50], coconut fiber was added to the composite as a replacement for sand in the amount of 3%, 6%, 9%, and 12% by weight during mixing and curing. It was found that the composite reinforced with 9% coconut fiber showed the highest tensile strength and compressive strength [50]. In general, based on the studied literature and [51], the following disadvantages of using coconut fibers in concrete can be distinguished: susceptibility to shrinkage during drying or volume changes due to alternating wetting and drying of concrete, deterioration in the workability of concretes of normal strength, a decrease in density, and an increase in water absorption. The advantages of using coir are as follows: increasing the strength of concrete of normal strength at a fiber dosage of 0.5-1.5% and a length of 50 mm, increasing tensile and bending strength at a dosage of up to 2% coir, and improving the impact strength of concrete. In addition, the use of coconut chips increases the permeability of concrete, as well as the carbonization and permeability to chloride ions; the treatment of coconut fiber with alkali increases the roughness of the coir; and the protective coatings of latex and pozzolana help to preserve the properties of coconut fiber in the cement matrix [51]. The principal differences between coconut fibers and other types of fibers are:  
1. Their plant origin, that is, their classification as renewable resources;
2. The low cost of concrete based on them, in view of their classification as plant and agricultural waste;
3. The environmental friendliness of their production, in contrast to glass, basalt, and polymer fibers;
4. The relatively high physical and mechanical characteristics in comparison with other types of fibers of plant origin;
5. The sufficient prevalence and hence the wide geography of potential application;
6. Good compatibility with other concrete components. This article examines and develops the idea of environmentally friendly FRC. Accordingly, it is necessary to develop methods that make it possible to use their natural, cheap, environmentally friendly, and renewable counterparts as fiber dispersed reinforcement instead of artificial fibers [52; 53; 54; 55; 56; 57; 58; 59]. This study aims for scientific novelty as follows: A rational dosage of fibrous coconut fiber was firstly determined as a component of a new material--FRC with improved characteristics. In terms of technological aspects, the parameters of the processes of introducing and mixing the components of fiber-reinforced concrete mixtures for improved concretes were first set.