## 3 Research Results and Analysis
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**No. of**} & \multirow{2}{*}{**1**} & \multirow{2}{*}{**2**} & \multirow{2}{*}{**3**} & \multirow{2}{*}{**4**} & \multirow{2}{*}{**5**} & \multirow{2}{*}{**6**} & \multirow{2}{*}{**7**} & \multirow{2}{*}{**8**} & \multirow{2}{*}{**9**} \\
**Mixture** & & & & & & & & & & \\ \hline \hline \multicolumn{2}{c}{Abrasion (g/cm\({}^{2}\))} & \multirow{2}{*}{0.30} & \multirow{2}{*}{0.32} & \multirow{2}{*}{0.34} & \multirow{2}{*}{0.22} & \multirow{2}{*}{0.24} & \multirow{2}{*}{0.26} & \multirow{2}{*}{0.20} & \multirow{2}{*}{0.24} & \multirow{2}{*}{0.25} \\
**(\(\mathrm{g/cm^{2}}\))** & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Abrasion of the investigated concretes and fiber-reinforced concretes. According to the data given in Table 5, an ES-model was built (6) reflecting the effect of the hardening accelerator and steel anchor fiber amount on the abrasion resistance of the investigated concretes and fiber-reinforced concretes. For the ES-model (6), the experimental error is 0.0038 g/cm\({}^{2}\):  
\[G\left(\text{g/cm}^{2}\right)=0.243+0.022x_{1}-0.005{x_{1}}^{2}+0.002x_{1}x_{2 }-0.045x_{2}+0.035{x_{2}}^{2}, \tag{6}\]  
Figure 7 shows the diagram drawn according to the ES-model (6). The diagram data reflect that steel fiber reinforcement reduces the concrete abrasion resistance by 30-35% to values within 0.2 to 0.24 g/cm\({}^{2}\). Compositions with the maximum amount of hardening accelerator without steel fiber also have a rather low abrasion rate, which will have a positive effect on the repair concrete durability. For repair materials, shrinkage is an important quality indicator, since it is through shrinkage deformations that its adhesion to the existing cement-concrete coating can be broken down. It is known [46] that the most important structural indicator for minimizing concrete shrinkage is the \(W/C\) mixture. As noted above, all concretes studied at this stage were modified with a rational amount of MasterGlenium SKY 608 polycarboxylate superplasticizer (1.2%), which ensured the minimum \(W/C\) ratio. The shrinkage of concrete during hardening in air-dry conditions was determined as follows. Concrete prisms of 10 cm \(\times\) 10 cm \(\times\) 40 cm for the first day after molding were stored in molds in a humidity chamber. After that, the prisms were dismantled and placed in air-dry conditions (humidity 60 \(\pm\) 5%, temperature 20 \(\pm\) 2 \({}^{\circ}\)C according to DSTU V.2.7-216:2009 [47]). With the dial indicators, fixed on tripods, the shrinkage of the samples after 3 h, 6 h and 1, 2, 3 and 7 days of being in air-dry conditions was determined. The data of the concrete and fiber-reinforced concrete shrinkage ratios of various compositions are shown in Table 6.  
According to the data given in Table 6, graphs are built (Figure 8) reflecting the effect of the fiber amount on the concrete shrinkage with a different amount of the hardening accelerator Sika Rapid 3 in the composition. Figure 7: Influence of varied factors on concrete and fiber-reinforced concrete abrasion resistance. Figure 8: Shrinkage ratio of investigated fiber-concretes (Table 6) during hardening in air-dry conditions: (**a**) mixtures No. 1, No. 4, No. 7; (**b**) mixtures No. 2, No. 5, No. 8; (**c**) mixtures No. 3, No. 6, No. 9.