## 3 Methods  
The following test equipment was used for this research: a laboratory concrete mixer; a laboratory vibrating platform (type SMZH-539-220A, OOO I-MACH, Armavir, Russia); a hydraulic test press (type IP-1000, Neftekamsk, OOO NPK \"TEKHMASH\", Russia) designed for static compression tests of the concrete samples; a universal tensile testing machine (type R-50, OOO I-MACH, Armavir, Russia) for the axial tension testing of the prisms [26; 27]. Measurements of the concrete deformations of the test prisms were conducted with a chain of strain gauges with a side length of 50 mm and dial indicators with a graduation of 0.001 mm. Experimental prisms were tested for axial compression and axial tension at a constant rate of deformation to obtain not only the strength and deformation characteristics of concrete, but to also obtain its full deformation diagrams \"\(\sigma\)-\(\varepsilon\)\" with a descending curve. Compression and tensile bending tests were conducted in accordance with the requirements of GOST 10180 \"Concretes. Methods for strength determination using reference specimens\" [30]. The axial compression and axial tension tests were conducted in accordance with the requirements of GOST 24452 \"Concretes. Methods of prismatic, compressive strength, modulus of elasticity and Poisson's ratio determination\" [31]. The experimental research program is shown in Figure 2. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Basalt Fiber**} & **Tensile** & **Fiber Diameter,** & **Fiber Length,** & **Elastic** & \multirow{2}{*}{**Density, g/cm\({}^{3}\)**} & **Elongation** \\  & **Strength, MPa** & **mm** & **mm** & **Modulus, GPa** & & **Coefficient,\%** \\ \cline{2-7}  & 3200 & \(16\times 10^{-3}\) & 12 & 120 & 2.6 & 3.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Physical and mechanical properties of the fiber. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Average Bulk Density of**} & \multicolumn{3}{c}{**Slag Pumice**} \\ \cline{2-5}  & \multicolumn{3}{c}{**Aggregate Fractions, mm**} \\ \cline{2-5}  & **Grains, kg/m\({}^{3}\)** & 5–10 & 2.5–5 & 1.25–2.5 \\ \cline{2-5}  & \multicolumn{3}{c}{(1.4–1.5) \(\times 10^{3}\)} & \multicolumn{3}{c}{(1.5–1.8) \(\times 10^{3}\)} & \multicolumn{3}{c}{(1.6–1.8) \(\times 10^{3}\)} \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Density limits of grains for combined mixtures. A series is a set of samples made from the same composition. The prism sizes in Figure 1 are in mm. The process of determining the deformation of a prism sample under axial compression is shown in Figure 3a,b. Figure 3: Photo of determining the deformation of the prism sample under axial compression (**a**); destroyed sample (**b**). Figure 2: Block diagram of the experiment program. Using the method of absolute volumes [32], the initial composition of the concrete mixture was determined:  
* Water-cement ratio: \[\frac{W}{C}=\frac{A\,R_{C}}{(R_{b}+0.5\,A\,R_{S})}\] (1) where \(A\) is the coefficient depending on the quality of the materials; \(R_{C}\) is the activity of the Portland cement; \(R_{b}\) is the concrete strength. \(W\) is the water consumption considering the required mobility determined from the graphs and was \(W\) = 205 L/m\({}^{3}\). * Portland cement consumption, kg/m\({}^{3}\): \[S=\frac{W}{W/C}\] (2)
* the crushed stone consumption, kg/m\({}^{3}\): \[CS=\frac{1000}{\alpha\frac{P_{CS}}{P_{t}^{CS}}+\frac{1}{P_{t}^{CS}}}\] (3) where \(\alpha\) is the coefficient of grain spreading; \(P_{CS}\) is the porosity; \(\rho_{t}^{CS}\) is the true density of the crushed stone; \(\rho_{b}^{CS}\) is the bulk density of the crushed stone. * sand consumption, kg/m\({}^{3}\): \[S=\rho_{t}^{S}\left(1000-\frac{C}{\rho_{t}^{C}}-\frac{CS}{\rho_{t}^{CS}}-W\right)\] (4) where \(\rho_{t}^{S}\) is the true density of the sand; \(\rho_{t}^{C}\) is the true density of the Portland cement; \(C\), \(CS\), and \(W\) are the consumption of the Portland cement, crushed stone, and water, respectively.