## 2 Materials and Methods
### Applied Printing Set-Ups and Structures  
Two different printing strategies were applied, as the research examines the relationship between PLA and concrete from two perspectives. The design was created using Solidworks 2016 \(\times\) 64 Edition SP01 (SolidWorks Corporation, Waltham, MA, USA). To convert the stl. files to printing instructions, a slicing software, UltiMaker Cura 5.3 0 (Ultimaker, Geldermalsen, The Netherlands), was used.  
The first layout concerned determining the solubility of the PLA material, so a 0.4 mm thick layer of sample was needed. During the printing process, the infill value did not influence the final structure of the PLA thin sheets due to its thin design. The size of the thin sample sheets was 25.0 \(\times\) 0.4 \(\times\) 80.0 mm.  
The other layout was the structure, which was used as a reinforcing element in concrete beams, with a size of 25.0 \(\times\) 5 \(\times\) 80.0 mm. Each element was printed with a grid infill pattern and 10% infill density, with the top and bottom layers set to 0. As the initial and final layers were set to 0, the grid structure was visible.  
This was a practical set-up as well as a functional one. Upon removing the initial and final layers, the printing time was reduced; furthermore, it was functional because, during casting, the concrete could spread between the gaps of the grid infill structure. Figure 2 shows the two structures in the UltiMaker Cura software with a coordinate system, and Figure 3 illustrates the six-cavity mold that was used during the casting of the concrete beams.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Material** & **Tensile Strength** & **Flexibility** & **Heat Resistance [\({}^{\circ}\)C]** & **Printability** & **Eco-Friendliness** \\ \hline \multirow{2}{*}{ESD} & Moderate & Flexible & 65–70 & Moderately easy & Non-degradable \\ \cline{2-6}  & \(\bullet\bullet\) & \(\bullet\bullet\) & \(\bullet\bullet\) & \(\bullet\bullet\) & \\ \hline \multirow{2}{*}{GYP} & Low & Brittle & 55–70 & Easy & Biodegradable, \\ \cline{2-6}  & \(\bullet\) & \(\cdot\) & \(\bullet\bullet\bullet\) & \(\bullet\bullet\) & non-recyclable \\ \hline \multirow{2}{*}{ABS} & Moderate & Flexible & 80–95 & Moderately hard & Non-degradable, \\ \cline{2-6}  & \(\bullet\bullet\) & \(\bullet\bullet\bullet\) & \(\bullet\bullet\) & \(\bullet\) & recyclable \\ \hline \multirow{2}{*}{
\begin{tabular}{c} PETG \\ (polyethylene \\ treephthalate \\ glycol-modified PLA) \\ \end{tabular} } & \multirow{2}{*}{Moderate} & \multirow{2}{*}{Flexible} & \multirow{2}{*}{70–85} & \multirow{2}{*}{Easy} & Non-degradable, \\  & & & & & \\ \cline{1-1} \cline{5-5}  & & & & & \\ \hline \end{tabular}
\end{table}
Table 2: _Cont._  
Figure 2: Printing set up of the specimens in UltiMaker Cura.  
The other printed (Figure 3) structure was the casting mold. The size of the concrete elements was 25.0 \(\times\) 25.0 \(\times\) 80.0 mm, so the inner size of the mold was identical. Three layers of the base were applied to the structure while printing. The wall thickness of the shape was 0.5 mm, with the same grid pattern and infill rate as the reinforcing element.  
In summary, three and three samples were made per material: for each material, three were reinforcing elements for casting, and three were used for dissolution tests.