# Enhanced Performance of Concrete Dispersedly Reinforced with Sisal Fibers
## 3 Results and Discussion
The increase in compressive strength with an increase in the number of sisal fibers was followed by a decrease in performance with a further increase in sisal fibers due to the following reasons. Firstly, the introduction of additional fibers leads to a greater water demand of the concrete mixture. Accordingly, in order to close the specified mixture, a larger amount of water is required, and this, in turn, negatively affects the strength characteristics. In addition, the introduction of additional fibrous materials requires a larger amount of cement lubricant and binder matrix materials, while the dosage of cement, sand and water did not change. Therefore, excess fiber leads to the expected reduction in strength characteristics. Figure 7 shows the flexural tensile strength \(R_{btb}\) of test concrete samples as a function of the percentage of sisal fiber reinforcement. The results of experimental dependences of tensile strength in the bending of concrete samples in the form of prisms on a different amount of sisal fibers are described by a formula with a coefficient of determination of 0.948. \[R_{btb}=5.5+1.82\times x^{0.912}\times\sin(1.74\,x+\,0.412),\quad\ R^{2}=0.948 \tag{5}\]  
Figure 8 shows the effect of the percentage of sisal fiber reinforcement on the axial tensile strength \(R_{bt}\) of test concrete samples. The results of experimental relations of the axial tensile strength of concrete samples with various percentages of reinforcement with sisal fibers are described by a formula with a coefficient of determination of 0.901. \[R_{bt}=3.4+0.911\times x^{0.978}\times\sin(1.943\,x+\,0.161),\quad R^{2}=0.901 \tag{6}\]  
The results of experimental studies of the tensile strength of samples showed that the maximum gains were recorded at a dosage of sisal fibers of 1%. Compared to conventional concrete, the flexural tensile strength of sisal fiber-reinforced concrete increased by 33% and the axial tensile strength increased by 29%. Figures 9 and 10 show the effect of the percentage of sisal fiber reinforcement on ultimate strains in axial compression and tension of concrete. The results of experimental relations of ultimate strains in axial compression of concrete samples at various percentages of reinforcement with sisal fibers are described by a formula with a coefficient of determination of 0.985. Figure 4:0The results of experimental studies of ultimate strains in axial tension of concrete samples at various percentages of reinforcement with sisal fibers are described by a formula with a coefficient of determination of 0.979. Figure 4:1  
Figure 11 shows the effect of the percentage of sisal fiber reinforcement on the modulus of elasticity of concrete test specimens. Figure 4:2 Results of experimental studies of ultimate strains in axial tension \(\varepsilon_{bt}\) of concrete samples in the form of prisms at various percentages of reinforcement with sisal fibers. Figure 4:3 Results of experimental studies of ultimate strains in axial compression \(\varepsilon_{b}\) of test concrete samples in the form of prisms at various percentages of reinforcement with sisal fibers. The results of experimental relations of the modulus of elasticity of concrete samples at various percentages of reinforcement with sisal fibers are described by a formula with a coefficient of determination of 0.979. Figure 4:4  
From Figures 9-11, it follows that the best values of deformation characteristics are observed in compositions with a dosage of sisal fiber in an amount of 1% by weight of cement. The increase in ultimate strains under axial compression and tension in comparison with the control composition without fiber was 25% and 42%, respectively, and the value of the elastic modulus increased by 15%. The effect of the percentage of dispersed sisal fiber reinforcement on the strength and deformation characteristics of the test samples of normal weight concrete is shown in Table 4 and is presented as a percentage difference compared to conventional concrete without fiber reinforcement.