## 3 Research Results and Analysis
The results of determining the loss of strength and mass of the investigated concrete and fiber-reinforced concrete specimens (in comparison with the control specimens) after 10, 15 and 20 freezing cycles up to \(-50\pm 5\)\({}^{\circ}\)C and thawing in 5% sodium chloride solution are shown in Table 4.  
Analysis of the data given in the table allows us to conclude that all compositions with steel fiber (No. 4-9) have frost resistance F200, which ensures their high durability in climatic conditions typical for most European countries. Concrete composition No. 1 (without fiber and hardening accelerator) is also characterized by frost resistance at the level of F200. With the introduction of the hardening accelerator in the absence of dispersed reinforcement (concrete of compositions No. 2 and No. 3), the frost resistance of the material decreases to the level of F150. The fact of a decrease in the frost resistance of concretes without dispersed reinforcement with the hardening accelerator Sika Rapid 3 indicates a limited negative effect of the modifier on this indicator. The decrease in frost resistance can be explained by a general decrease in the strength of the composite at the design age when using the hardening modifier. The use of steel fiber in general contributes to an increase in the frost resistance of concretes for rigid pavement repair. This is confirmed by the fact that fiber-reinforced concretes, regardless of the amount of hardening accelerator, have frost resistances at the level of F200. In addition, one of the important indicators that determine the durability of the road surface concrete is wear resistance (abrasion). Repaired road sections are exposed to vehicle tires (i.e., abrasion) for a shorter time than the main pavement. However, it is also important for repair concretes to ensure sufficient wear resistance, in particular because, as shown in [43], this indicator affects the ability of the material to withstand complex frost-salt effects. At the same time, in [43], it is recommended to use concrete with abrasion no higher than 0.50 g/cm\({}^{2}\) in road construction. The abrasion resistance was determined on an abrasive wheel by DSTU B V.2.7-212:2009 [44], ASTM C944/C944M-19 [45]. The data of the abrasion resistance of the investigated concretes and fiber-reinforced concretes at nine control points of the experiment plan are shown in Table 5. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{3}{*}{**No. of**} & \multirow{3}{*}{\(X_{1}\), **M**} & \multirow{3}{*}{\(X_{2}\), **S**ield**} & \multicolumn{3}{c}{**Strength Loss after Freezing to \(-50\pm 5\)\({}^{\circ}\)C and Thawing in 5\% Sodium**} & \multirow{3}{*}{\
\begin{tabular}{c} **Mass Loss after Freezing to \(-50\pm 5\)\({}^{\circ}\)C and Thawing in 5\% Sodium**} & \multirow{3}{*}{
\begin{tabular}{c} **Assessment** \\ **of Frost** \\ **Resistance** \\ \end{tabular} } \\  & **A**celearator & & & & **Chloride Solution (\%)** & & & **Chloride Solution (\%)** & & **A**celearator \\ \cline{3-8}  & & & **10 Cycles** & **15 Cycles** & **20 Cycles** & **10 Cycles** & **15 Cycles** & **20 Cycles** & \\ \hline
1 & \(-1\) & \(-1\) & 1.26 & 1.98 & 4.91 & 0.30 & 0.30 & 1.18 & F200 \\
2 & 0 & \(-1\) & 1.58 & 2.74 & 5.93 & 0.30 & 1.57 & 1.87 & F150 \\
3 & +1 & \(-1\) & 1.80 & 4.63 & 6.96 & 0.40 & 0.99 & 2.29 & F150 \\
4 & \(-1\) & 0 & 1.16 & 1.85 & 4.78 & 0.31 & 0.48 & 1.12 & F200 \\
5 & 0 & 0 & 1.42 & 2.45 & 4.86 & 0.39 & 1.16 & 1.61 & F200 \\
6 & +1 & 0 & 2.16 & 3.80 & 4.88 & 0.20 & 0.79 & 1.79 & F200 \\
7 & \(-1\) & +1 & 0.77 & 2.07 & 4.90 & 0.38 & 0.59 & 1.37 & F200 \\
8 & 0 & +1 & 0.87 & 3.33 & 4.88 & 0.39 & 0.78 & 1.36 & F200 \\
9 & +1 & +1 & 0.84 & 3.35 & 4.92 & 0.59 & 0.79 & 1.28 & F200 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Determination of concrete frost resistance according to DSTU B V.2.7-49-96 “Concrete. Accelerated methods for determining frost resistance with repeated freezing and thawing” (third method).