# Numerical Identification of Material Model Parameters of UHPFRC Slab under Blast Loading
## 2 Tested Specimens  
The slabs and specimens for the basic mechanical test were made of UHPFRC (Ultra-High Performance Fibre Reinforced Concrete) with a 1% volume ratio of reinforcement with Dramix fibres and a 1% volume share of Fibrex fibres. The mechanical characteristics of Dramix OL fibres 13/.20 (O 0.2 mm, \(l\) = 13 mm) are as follows: tensile strength of 2750 MPa and Young's modulus of 200 GPa, while for Fibrex A1 fibres (0.4 \(\times\) 0.6 \(\times\) 25 mm) the tensile strength reaches 350 MPa and Young's modulus value is 200 GPa.  
Six test slabs with dimensions of 500 mm \(\times\) 500 mm \(\times\) 60 mm were manufactured and treated in accordance with EN 12390-1,2 [47; 48]. These slabs were used to perform the main experiment described in Chapter 3.  
Six test cubes of concrete with dimensions of 150 mm \(\times\) 150 mm \(\times\) 150 mm were used to verify the compressive strength of the concrete meeting the EN 12390-3 standard [49]. To determine the increase in concrete strength, a compression strength test was performed on samples at 1, 3, 7 and 28 days old.  
The results of the cube strength tests are presented in Tables 1 and 2. The average value of the cube strength of 28-day-old concrete reaches 149 MPa. This value corresponds with the value of cubic strength of similar composition and grade concrete manufactured and used in previous authors' work [50].  
To determine the tensile strength of concrete from the three-point bending test according to the standard EN 12390-5 [51], 12 beams with dimensions of 100 mm \(\times\) 100 mm \(\times\) 400 mm were produced and treated in accordance with standard EN 12390-1 [47].  
Table 3 shows the results of the bending test with the resulting average value of tensile strength 8.85 Mpa calculated from the measured values according to the relation [51]:  
\[f_{c}=\frac{F.l}{d_{1}.d_{2}^{2}} \tag{1}\]  
where \(f_{c}\) (Mpa) is tensile strength, \(F\) (N) is the maximum load, \(l\) (mm) is the distance between the support rollers and \(d_{1}\) (mm) and \(d_{2}\) (mm) are the dimensions of the cross section of the body.  
In Figure 1 it is possible to see three-point bending test results from samples T3.1-T3.3.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Spec.** & **Density** & **Age** & **Force** & **Cubic Strength** \\
**No.** & **(kg/m3)** & **(days)** & **(kN)** & **(MPa)** \\ \hline P1 & 2742 & 1 & 520 & 23.3 \\ P2 & 2682 & 3 & 2300 & 103.6 \\ P3 & 2744 & 7 & 2580 & 117.8 \\ P4.1 & 2648 & 28 & 3020 & 136.0 \\ P4.2 & 2652 & 28 & 3020 & 153.9 \\ P4.3 & 2661 & 28 & 3560 & 157.2 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Results of UHPFRC cube strength tests on samples of batches P1–P3 and P4.1–P4.3.  
Figure 1: Three-point bending test results of the 28-day-old samples from the batch T3.1–T3.3.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Dimensions**} & \multicolumn{3}{c}{**Tensile**} \\
**Spec.** & **Height** & **Width** & **Length** & **Weight** & **Density** & **Age** & **Force** & **Strength** \\
**No.** & **(mm)** & **(mm)** & **(mm)** & **(kg)** & **(kg/m3)** & **(days)** & **(kN)** & **(MPa)** \\ \hline T1.1 & 101.2 & 100.2 & 400 & 10.50 & 2590 & 28 & 25.84 & 7.64 \\ T1.2 & 101.0 & 100.4 & 400 & 10.4