# Experimental Testing of Reinforced Concrete Deep Beams Designed by Strut-And-Tie Method
## 3 Experimental Program  
### Material Properties  
For the preparation of the tested specimens, the following materials were used:  
* Cement type CEM II/A-S with the strength class 42.5R (Nexe, Nasice, Croatia). The basic physical and mechanical properties of used cement, given in Table 1, were tested according to standards EN 196-1 [24] and EN 196-3 [25].
* Fine and coarse aggregate, natural aggregate, had fractions of 0/4 mm, 4/8 mm, and 8/16 mm (river Drina, Serbia). The grain size distribution is shown in Figure 4.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Physical-Mechanical Properties** & **PC 20S 42.5R** \\ \hline Initial Setting time [min] & 160 \\ Soundness [mm] & 0.5 \\ Early strength after 2 days [MPa] & 31 \\ Standard strength after 28 days [MPa] & 55 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Cement properties.  
Figure 4: Grain size distribution of aggregate fractions.  
Figure 3: (**a**) Nodal zone polygon, (**b**) biaxial strength of concrete from the software “ST method”.  
It can be noticed that there are no undersize and oversize grains for all aggregate fractions. The obtained results of the tested physical-mechanical properties are given in Table 2.  
The concrete of class C25/30 is chosen for the preparation of reinforced concrete wall specimens. The composition of the concrete mixture is given in Table 3.  
Three standard cube specimens were tested, with the edge of 150 mm, prepared and cured in accordance with EN 12390-2 [30]. The testing of the concrete compressive strength after 28 days was done according to the EN 12390-3 [31], Figure 5a. The obtained test results are shown in Tables 4 and 5.  
According to the test results, the mean value of the density of hardened concrete was 2406 kg/m\({}^{3}\) and the average concrete compressive strength was 31.9 MPa, while the tensile strength was 2.37 MPa.  
The yield strength and tensile strength of the reinforcing steel were tested according to EN ISO 15630-1 [32] on four specimens (labeled R1, R2, R3, and R4), Figure 5b. Test results are given in Table 6.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{5}{c}{**Compressive Strength**} \\ \cline{2-5}
**Specimen** & **Cube Edge** & **Mass** & **Compressive Force** & **Compressive Stress** \\  & **[cm]** & **[kg]** & **[kN]** & **[MPa]** \\ \hline
1 & 15.40 & 8.10 & 752 & 31.71 \\
2 & 15.30 & 8.15 & 746 & 31.61 \\
3 & 15.40 & 8.10 & 768 & 32.38 \\ \hline mean & 15.37 & 8.12 & 755.33 & 31.90 \\ \hline \hline \end{tabular}
\end{table}
Table 4: The results of concrete compressive strength.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{5}{c}{**Fraction [mm]**} & **Recommendations** \\ \cline{3-5}
**Type of Testing** & **Procedure** & **0/4** & **4/8** & **8/16** & \\ \hline Finest content (\%) & EN 933-1 [26] & 0.76 & 0.07 & 0.02 & to be declared \\ Shape Index & EN 933-4 [27] & - & 8.3 \(\text{SI}_{15}\) & 15.6 \(\text{SI}_{20}\) & \(\leq\)\(\text{SI}_{55}\) \\ Resistance to fragmentation “Los Angeles” & EN 1097-2 [28] & & 25.4 \(\text{LA}_{30}\) & 27.3 \(\text{LA}_{30}\) & \(\leq\)\(\text{LA}_{50}\) \\ Oven-dry particle density (kg/m\({}^{3}\)) & EN 1097-6 [29] & 2620 & 2620 & 2510 & \(\geq\)2100 kg/m\({}^{3}\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Physical-mechanical tests of the fractionated natural aggregate.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{5}{c}{**Fensile Splitting Strength**} \\ \cline{2-5}
**Specimen** & **Cube Edge** & **Mass** & **Compressive Force** & **Tensile Stress** \\  & **[cm]** & **[kg]** & **[kN]** & **[MPa]** \\ \hline
1 & 15.30 & 8.10 & 82 & 2.23 \\
2 & 15.20 & 8.10 & 80 & 2.20 \\
3 & 15.10 & 8.00 & 96 & 2.68 \\ \hline mean & 15.20 & 8.06 & 86 & 2.37 \\ \hline \hline \end{tabular}
\end{table}
Table 5: The results of tensile splitting strength.