## 2 Materials and Methods  
Procedures based on the guidelines contained in current EU regulations and standards were used to carry out the research. Figure 1 shows a conceptual diagram of the research carried out. To determine the effect of glass flour and polypropylene fibers on compressive strength, samples of ordinary concrete of class C25/30 with consistency K4 (semi-liquid consistency) were prepared based on EN 206 + A2:2021-08. To prepare the concrete mix, Portland cement CEM I 42.5 R from the Ozarow cement plant, in accordance with PN-EN 197-1: 2012, was used [32; 33]. This cement is characterized by its high early strength. The declared  
Figure 1: Conceptual diagram of laboratory tests performed. performance of Portland cement is summarized in Tables 1 and 2. The given values are average values, guaranteed by the manufacturer for 2023. In all samples, the same granulometric composition of fine aggregate, river sand of the 0-2 mm fraction selected by the sieving method according to EN 933-1:2012 and the same composition of coarse pebble aggregate fraction 4-16 mm selected by the method of successive approximations in three stages--Table 3 was assumed [34]. The bulk density of coarse and fine aggregate was determined by the pycnometric method in accordance with EN 1097-6:2002 [35]. The density for sand was 2.60 g/cm\({}^{3}\) and for gravel, 2.65 g/cm\({}^{3}\). For all laboratory tests, drinking water was used in accordance with EN 1008:2004 [36]. As a partial replacement for cement, glass flour was used in amounts of 10, 20, and 30%. flour is a product that is made by grinding and shredding glass into very fine particles, which gives it a light, powdery consistency but still has a relatively high density compared to some other building materials such as cement or sand. The density of the glass flour is 2.4 g/cm\({}^{3}\). Figure 2 shows the grain size of the glass meal. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Blaine Specific** **Surface Area (cm\({}^{2}\)/g)**} & \multirow{2}{*}{**Start of Setting Time** **(min)**} & **Compressive** **Strength after 2 Days** **(MPa)** & **Compressive** **Strength after 28 Days (MPa)** \\ \hline
3330 & 218 & 21.0 & 49.8 \\ \hline \multicolumn{4}{c}{Share of mineral phases CEM I (\% w.)} \\ \hline C3S—55.54 & C2S—14.59 & C3A—8.15 & C4 AF—6.85 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Physical properties and phase composition of cement CEM I 42.5 R (data from the manufacturer—own support). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Fractions**} & \multicolumn{2}{c}{**Fraction Mixing Percentage**} & \multirow{2}{*}{**Particle Size (\%)**} \\ \cline{2-2} \cline{4-5}  & **(for Sand and Gravel)** & & & **Particle Size (\%)** \\ \cline{2-2} \cline{4-5}  & **Stage I** & **Stage II** & **Stage III** & **Sand** & **Gravel** \\ \hline
0.0–0.125 & & & 1.93 & 0.60 \\ \hline
0.125–0.25 & & & 17.82 & 5.52 \\ \hline
0.25–0.50 & & & 28.62 & 8.87 \\ \hline
0.50–1.0 & & & 24.32 & 7.54 \\ \hline
1.0–2.0 & & & 27.31 & 8.47 \\ \hline
2.0–4.0 & & 35 & & 24.15 \\ \hline
4.0–8.0 & 45 & & 69 & 20.18 \\ \hline
8.0–16.0 & 55 & & & 24.67 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Grain composition of aggregate (own version). Polpropylene fibers were also used to strengthen the concrete structure. Polypropylene fibers extruded from polypropylene granulate/polymeric material (CH\({}_{2}\)CH(CH\({}_{3}\))\({}_{3}\)), bundled and cut in accordance with EN 14889-2:2006 (Bautech sp.zo.o Piaseczno near Warsaw, Poland) were also used for the tests. In the concrete mix, they form a three-dimensional supporting network resistant to gravity, thanks to which they maintain a constant level of concrete, prevent cracks, reduce plastic shrinkage, and limit the formation of shrinkage scratches [37]. Figure 3 shows the fibers and their characteristics.