## 4 Experimental Results and Discussion  
### Evaluation of Concrete Parameters in the Elastic State  
The experimentally obtained dependences between the longitudinal deformations and the stresses in uniaxially loaded cylindrical concrete specimens, which were tested in the first test series, are presented in Figure 4. As evident from this figure, the dependences are close to linear and allow for the disclosure of the concrete's ultimate elastic deformations and its modulus of elasticity.  
The dependences of the transverse deformations on stresses are shown in Figure 5. These dependences enable the concrete's Poisson's ratio as well as the pattern of inelastic concrete deformation development (which cannot be done using only longitudinal deformations) to be obtained. It should be mentioned that this possibility becomes available when the transverse deformations exceed the Poisson's ratio validity range, i.e., after the initiation of longitudinal cracks, when \(\varepsilon_{trans}>\varepsilon_{ct\ ul}\).  
Figure 3: Measurement device system: 1. LDT devices; 2. SG sensors; 3. load sensor; 4. data logger; 5. Wheatstone bridge.  
Following Figure 5, the tested specimens exhibited elastic behavior in the transverse direction up until about 70% of the concrete strength (concrete specimen strength ranges from 20.9 to 28.2 MPa). For example, the concrete strength of Sp1.1 is equal to 24 MPa, and the strength value corresponding to the elastic stage reaches 17 MPa, which is about 70% of the specimen strength. Further, transverse deformations grow in a nonlinear manner, which indicates the development of inelastic deformations that are not evident in the longitudinal direction (see Figure 4). The experimental results are summarized in Table 3.  
The obtained experimental data correspond to those available in Eurocode 2 [2]. A comparison of the known Poisson ratios data [6] is presented in Table 4. As evident from this table, the Poisson's ratios for all of the tested specimens are close to the known results.  
Figure 4: Experimental dependences \(\sigma_{c}\) vs. \(\varepsilon_{c}\).  
Figure 5: Experimental dependences \(\sigma_{c}\) vs. \(\varepsilon_{trans}\).  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Specimen** & \(\varepsilon_{c}\)**, \%** & \(\varepsilon_{c}\)**, \%** & \(\varepsilon_{c}\)**, \%**o & \(\varepsilon_{c}\)**, MPa** & \(\
u\) \\ \hline Sp1.1 & 0.678 & 0.100 & 27700 & 0.15 \\ Sp1.2 & 0.453 & 0.100 & 27600 & 0.22 \\ Sp1.3 & 0.556 & 0.086 & 26740 & 0.16 \\ Sp1.4 & 0.605 & 0.092 & 32000 & 0.15 \\ Average & 0.573 & 0.095 & 28510 & 0.17 \\ \hline \end{tabular}
\end{table}
Table 3: Experimental values of maximum elastic and ultimate transverse concrete strains, modulus of elasticity, \(E_{c}\), and Poisson’s ratio, \(\
u\).  
It should be also noted that according to the previously proposed theoretical model [1], the maximum elastic longitudinal deformations are within 0.5%, and the ultimate elastic deformations are equal to 1%, which is also confirmed by the obtained experimental data.  
The data obtained in the second test series show the similar tendencies in the behavior of the specimens and confirms the previously presented results (Figures 6 and 7).