# Enhanced Performance of Concrete Dispersedly Reinforced with Sisal Fibers
## 1 Introduction  
### Background  
Compared to ordinary concrete, fiber-reinforced concretes have significantly higher tensile strength, deformability, increased compressive strength and durability, as well as the ability to perceive alternating loads and dynamic impact without destruction [1, 2, 3]. Ordinary concrete initially has in its structure many microcracks formed during concrete hardening, which develop when a load is applied, causing its low tensile strength [3, 4, 5]. The addition of even small fibers to concrete, which would be evenly distributed in the concrete matrix and chaotically oriented, significantly reduces the formation of microcracks during concrete hardening and reduces shrinkage, with a general increase in the strength of the material. Fibers inhibit the development of cracks and hold the concrete matrix even after cracking. Traditionally, steel, basalt, polypropylene and cellulose fibers areused as fiber-dispersed reinforcement of concrete. Fiber reinforcement of concrete with glass and carbon fibers is also quite popular. Despite the outstanding tensile strength characteristics of steel, basalt and synthetic fibers, most of them require separate production and processing, often requiring high energy costs and significantly increasing the cost of construction, which, in the end, does not always justify the obtained characteristics of concrete, and they also have a negative impact on the environment due to massive emissions of greenhouse gases. It can be confidently stated that construction requires significant amounts of non-renewable materials. Thus, the actual problem of modern construction is the search for natural alternatives to steel and synthetic fibers currently used as fiber reinforcement [6; 7; 8; 9; 10; 11]. Natural fibers are a topical environmentally friendly and economical material for improving the properties of fiber-reinforced concrete, while at the same time improving the environmental situation through the disposal of waste of natural origin. The advantages of such fibers are low cost, no need for mechanized production and synthesis, renewability, lack of waste, absence of environmental pollutants, safety for humans and animals, as well as strength characteristics sufficient to cover the needs of modern construction [12; 13; 14; 15; 16; 17]. The main \"components of such fibers are cellulose, hemicellulose, lignin, pectin, wax and water-soluble substances\" [18; 19; 20]. Several studies [12; 13; 21; 22] were aimed at studying the properties of ordinary concrete with the addition of various types of natural fibers, namely, jute, hemp, pineapple and banana fibers. The results of these studies showed that the addition of natural fibers up to 1% of the volume of concrete improved its compressive strength. A restraining effect on failure was also noted, whereby the failure itself became less brittle as the percentage of fiber reinforcement was increased. The compressive strength of the samples increased with an increase in the amount of fibers up to 2%; however, a decrease in strength was noted at higher reinforcement percentages. Sisal fiber attracts a lot of attention among natural fibers. \"It is a coarse natural fiber obtained from the leaves of the Agave sisalana plant\" [23; 24; 25; 26; 27; 28; 29; 30; 31]. The structure of sisal fiber is shown in Figure 1.  
The fibers are extracted from the leaves of Agave sisalana through a process of decoration, which involves the mechanical grinding of the leaves until only the coarse fibers remain. Next, the fibers are thoroughly washed and separated, after which the fiber is dried, undergoes a final brushing and is packed for sale. The microstructure of the sisal  
Figure 1: Sisal fiber structure. fiber consists of separate rings with a diameter of 6-30 \(\upmu\)m. The fiber consists of cellulose (55-66%), hemicellulose (12-17%), lignin (7-14%), pectin (1%) and ash (1-7%). In works [32; 33], a study was carried out on the properties of sisal fiber for use in fiber-reinforced concrete.