## 3 Results and Discussion  
Results of Experimental Studies of the Influence of a Combination of Various Types of Fibers and Their Volumetric Content on the Strength and Deformation Characteristics of Fiber-Reinforced Concrete  
Determination of the strength and deformation characteristics of fiber-reinforced concrete was carried out using regression dependences, the type and values of the coefficients of which are determined by the methods of mathematical experimental design techniques. The strength and deformation characteristics of fiber-reinforced concrete are taken as the response functions, depending on the combination of different types of fibers \(k\) and their volume content \(\mu\). The response functions:  
* \(R_{c}\) (\(k\), \(\mu\))--compressive strength, MPa;
* \(R_{then}\) (\(k\), \(\mu\))--tensile strength in bending test, MPa; \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**N**} & **Fiber Type Combination** & **Fiber Volume Content (u), \%** & **Compressive Strength, MPa** & **Strength in Bending Test, MPa** & **Ultimate Deformations during Avail Compression, mm/m\({}^{*}10^{-3}\)** & **Ultimate Deformations during Axial Tension, mm/m\({}^{*}10^{-4}\)** & **Elastic Modulus, GPa** \\ \hline \multirow{2}{*}{1} & & 0/0 & 41.1 & 4.3 & 2.11 & 1.33 & 32.9 \\  & steel/basalt & 0.5/1.5 & 49.7 & 14.4 & 1.42 & 0.78 & 39.2 \\  & & 1.0/1.0 & 54.3 & 14.8 & 1.51 & 0.73 & 39.8 \\  & & 1.5/0.5 & 56.8 & 15.1 & 1.36 & 0.71 & 40.8 \\ \hline \multirow{2}{*}{2} & & 0/0 & 41.1 & 4.3 & 2.11 & 1.33 & 32.9 \\  & & 0.5/1.5 & 48.7 & 12.5 & 1.56 & 0.85 & 38.7 \\  & & 1.0/1.0 & 51.5 & 14.8 & 1.48 & 0.72 & 40.1 \\  & & 1.5/0.5 & 53.8 & 15.9 & 1.33 & 0.70 & 41.3 \\ \hline \multirow{2}{*}{3} & & 0/0 & 41.1 & 4.3 & 2.11 & 1.33 & 32.9 \\  & steel/basalt & 1.5/2.5 & 57.9 & 17.1 & 1.23 & 0.63 & 44.9 \\  & & 2.0/2.0 & 63.7 & 21.2 & 1.11 & 0.52 & 49.3 \\  & & 2.5/1.5 & 59.7 & 18.3 & 1.21 & 0.57 & 46.5 \\ \hline \multirow{2}{*}{4} & & 0/0 & 41.1 & 4.3 & 2.11 & 1.33 & 32.9 \\  & steel/polypropylene & 1.5/2.5 & 54.8 & 16.9 & 1.31 & 0.69 & 44.5 \\  & & 2.0/2.0 & 56.1 & 17.3 & 1.24 & 0.61 & 45.1 \\  & & 2.5/1.5 & 62.6 & 19.3 & 1.15 & 0.55 & 48.2 \\ \hline \multirow{2}{*}{5} & & 0/0 & 41.1 & 4.3 & 2.11 & 1.33 & 32.9 \\  & steel/basalt & 0.5/2.5 & 55.5 & 14.8 & 1.52 & 0.73 & 46.9 \\  & & 1.5/1.5 & 58.3 & 17.9 & 1.25 & 0.60 & 45.2 \\  & & 2.5/0.5 & 59.7 & 18.3 & 1.22 & 0.58 & 46.1 \\ \hline \multirow{2}{*}{6} & & 0/0 & 41.1 & 4.3 & 2.11 & 1.33 & 32.9 \\  & steel/polypropylene & 0.5/2.5 & 52.9 & 13.9 & 1.47 & 0.80 & 38.9 \\  & & 1.5/1.5 & 55.8 & 16.4 & 1.34 & 0.70 & 44.3 \\  & & 2.5/0.5 & 56.7 & 17.9 & 1.27 & 0.59 & 45.4 \\ \hline \multirow{2}{*}{7} & & 0/0 & 41.1 & 4.3 & 2.11 & 1.33 & 32.9 \\  & polypropylene/basalt & 0.5/1.5 & 48.1 & 15.1 & 1.34 & 0.72 & 40.9 \\  & & 1.0/1.0 & 55.4 & 16.8 & 1.29 & 0.69 & 44.7 \\  & & 1.5/0.5 & 53.9 & 14.9 & 1.45 & 0.75 & 40.1 \\ \hline \multirow{2}{*}{8} & & 0/0 & 41.1 & 4.3 & 2.11 & 1.33 & 32.9 \\  & & 1.5/2.5 & 61.8 & 18.9 & 1.19 & 0.56 & 47.3 \\  & & 2.0/2.0 & 59.8 & 17.1 & 1.22 & 0.59 & 44.9 \\  & & 2.5/1.5 & 53.9 & 16.1 & 1.31 & 0.70 & 44.1 \\ \hline \multirow{2}{*}{9} & & 0/0 & 41.1 & 4.3 & 2.11 & 1.33 & 32.9 \\  & polypropylene/basalt & 0.5/2.5 & 57.4 & 17.7 & 1.26 & 0.62 & 45.6 \\  & & 1.5/1.5 & 58.3 & 18.1 & 1.19 & 0.59 & 46.0 \\  & & 2.5/0.5 & 54.1 & 16.8 & 1.28 & 0.68 & 44.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Results of experimental studies of the effect of a combination of various types of fibers and volume content on the strength and deformation characteristics of fiber-reinforced concrete. Figure 8: Dependence of the tensile strength in the bending of fiber-reinforced concrete on the type of fiber combination and volume content. Figure 11: Dependence of the modulus of elasticity of fiber-reinforced concrete on the type of combination of fibers and volume content. Figure 10: Dependence of ultimate deformations of fiber-reinforced concrete under axial tension on the type of fiber combination and volume content.