## 2 Materials and Methods
### Bending Tests and DIC Measurements  
The three-point bending tests were carried out with Zwick 1454 (Zwick Roell Group, US, Singapore) at 7.6 mm/min loading speed with load cell HBM U3 20 kN (HBM Ltd., Budapest, Hungary) and data collector HBM quantum MX840A (HBM Ltd., Budapest, Hungary), where the specimens were under load until they showed a sign of cracking. During the tests, a specific test method was applied rather than a standard one, where each test piece was loaded at 7.6 mm/min loading speed with load cell HBM U3 20 kN. A uniform load with a constant 20 kN causes the test specimens to move. The amplification effect of the reinforcing elements can be determined as a function of the displacement of the test pieces relative to their initial state (vertical displacement in mm) and the resistance to the load (force in kN). The load was placed in the middle of the specimens, and the distance between the supports (i.e., bay length) was 75 mm. The tests were carried \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Material** & **Mass [g]** & **Mass Percentage [\%]** & **Volume Percentage [\%]** \\ \hline ESD & 1.24 & 1.07 & 2.0 \\ ENG & 1.24 & 1.07 & 2.0 \\ HI & 1.24 & 1.07 & 2.0 \\ GYP & N/A & N/A & 2.0 \\ ABS & 1.05 & 0.91 & 2.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Basic parameters of reinforced concrete elements. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Material** & **Manufacturer (Brand)** & **Amount/Quantity** \\ \hline Water & - & 480.6 g \\ Cement & CEM-II-AS-42.5 (Duna-Drava Cement, Vac, Hungary) & 1369.6 g \\ limestone powder & Lafarge (Lafarge, Paris, France) & 328.4 g \\ Fine aggregate & graded sand 0/1 (Duna-Drava Cement, Vac, Hungary) & 1489.8 g \\ Fluxing agent & VC 5 NEW (Sika, Baar, Switzerland) & 8.8 mL \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Concrete composition per 1.6 L of concrete. out according to the MSZ EN 12390-5:2019 standard [69]. Since the laboratory we used is not an accredited measuring laboratory, and the measurement is related to research, the chosen length of \(L=80\) mm was used instead of the length \(L\geq 3.5\times d\) (87.5 mm), defined in MSZ EN 12390-5:2019 [69], where \(d\) is the dimension of the specimen in cross-section (i.e., the width and the height), as well as the distance between the support points and the applied vertical concentrated forces and between the two concentrated forces in the case of 4-point bending (see Figure 4). In the case of the bending tests, even though the standard MSZ EN 12390-5:2019 [69] was included, the authors had to deviate from the instantaneous measurement described in the standard. The reason was the GOM ARAMIS (GOM, Braunschweig, Germany) measurements. It was necessary to deviate because if the paint had not adhered to the surface, the measurements would not have been able to be made since the technology calculates the amount of deformation from the displacements of the points painted on the surface. Before laboratory experiments, each sample was dried for two days to ensure that moisture content did not affect the results. This was verified by weighing the specimens every 4 h on the first day and every hour on the second day until the difference in weight was negligible. The specimens were then painted, first with a matte white lacquer primer (Deco Color Moto Techno Aerosol (Chemmot Ewa Kumorek Spolka Komandytowa, Skawina, Poland)) and then with a matte black lacquer topcoat spray (United Sealants Sprays Matte Black Spray (Neosil Kft., Bag, Hungary)). Getting the paint pattern right was essential for the DIC (digital image correlation) GOM ARAMIS (GOM, Braunschweig, Germany) measurements. The issue of stain pattern was most carefully examined by [PERSON] [70; 71]. According to [PERSON], the pattern can be described by four primary characteristics: spot size, contrast, overlap of spots, and density of spots. It is the combination of these characteristics that most accurately determines the spot size.