## 3 Results  
### Maximum Dry Density (MDD) and Optimum Moisture Content  
The results of the Proctor tests conducted on the investigated hydraulically bound mixtures are presented in Figure 3 (moisture content vs. dry density) and in Table 4 (optimum moisture contents). The type of binder used had a measurable effect on the optimum moisture content of the mixtures. The optimum moisture contents of all of the fly ash mixtures were constrained to a narrow range of 8.75-9.25%, while the maximum dry densities of the reference cement-bound mixtures were obtained at 7.25% and 7.75% moisture content, respectively. The type of binding agent had no visible impact on the maximum dry density of the mixtures. Regarding the effects of the fiber reinforcement content on the Proctor results, it had little-to-no effect on the optimum moisture contents of the mixtures. In the case of the maximum dry density, however, in two of three cases (Figure 3b,c), the mixtures with 0.05% of fiber reinforcement reached a maximum dry density of equal to or higher than that of the mixtures without fibrous additives, while the 0.10% addition of fibers in all cases resulted in a decrease in MDD. Figure 2: Grading of the aggregate mixture used in the evaluated hydraulically bound mixtures. Compressive Strength (\(R_{\text{C 144}}\), \(R_{\text{C 28d}}\), and \(R_{\text{C 42d}}\))  
The results of the uniaxial compressive strength of the investigated mixtures after 14, 28, and 42 days of curing are presented in Figure 4.  
Based on the presented results, it can be stated that all of the evaluated factors in the analyzed mixtures had a significant impact on their compressive strength--the composition of the binder, its amount, and the amount of fiber reinforcement used. Of the two reference mixtures, the 8-0-0 mixture achieved higher strengths (\(\text{R}_{\text{C 28d}}=4.4\) MPa), which corresponds to the \(\text{C}_{3/4}\) class of hydraulically bound mixtures, while the 5-0-0 mixture was characterized by an average strength of \(\text{R}_{\text{C 28d}}=2.3\) MPa, which classifies it as a \(\text{C}_{1/2}\) CBGM. Among the mixtures containing fly ash, their compressive strength after 28 and 42 days was almost directly related to the amount of the binding agent. After 14 days, all of the non-reinforced fly ash mixtures exhibited very low compressive strengths of 0.3-0.4 MPa. The 1-3.5-0 mixture bound with fly ash was characterized by the lowest values of compressive strength of all of the analyzed mixtures (\(\text{R}_{\text{C 42d}}=0.8\) MPa). Increasing the amount of fly ash to 14%, relative to the weight of the entire mixture, resulted in a significantly higher strength of the cured material. In the case of this mixture (1-14-0), its 42-day strength was 3.0 MPa, which is higher than that of the reference 5-0-0 mixture. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{**Optimum Moisture Content**} \\
**Cement** & **Fly Ash** & \multicolumn{2}{c}{**Fiber Content (\%)**} \\
**Content (\%)** & **Content (\%)** & **0.0** & **0.05** & **0.10** \\ \hline
5.0 & 0.0 & 7.25\% & - & - \\
8.0 & 0.0 & 7.75\% & - & - \\
1.0 & 3.5 & 8.75\% & 9.25\% & 9.00\% \\
1.0 & 7.0 & 9.25\% & 9.25\% & 9.25\% \\
1.0 & 14.0 & 9.50\% & 9.25\% & 9.25\% \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Optimum moisture content of the evaluated hydraulically bound mixtures. Figure 3: Results of the Proctor tests for evaluating the optimum moisture content in the evaluated mixtures: (**a**) reference CBGMs, (**b**) mixtures with 3.5% of fly-ash, (**c**) mixtures with 7% of fly-ash, (**d**) mixtures with 14% of fly-ash. The evaluation of the mixtures bound with fly ash and containing dispersed fiber reinforcement showed that its use significantly improved the compressive strength throughout the mixtures' curing periods.