## 3 Results and Discussion
### Concerning the Dissolution of the Fiber-Reinforced Concrete Specimens Underwater  
The dissolution tests of the reinforcing materials were carried out in parallel with tests on the broken fiber-reinforced concrete specimens stored underwater. The specimens were stored in tap water, covered, and subjected to the three-point bending test for a further 4 weeks after the fracture tests. During this time, the pH and temperature of the aqueous medium were monitored. The pH and temperature of the medium were rechecked after a further 4 weeks, i.e., at week 8 after the start of the observation, to see if there were any outliers. Table 9 represents the pH values and the temperature of the aqueous medium over the four-week study. The measured pH values fell in the alkaline range but were not high enough (9-12) to clearly indicate the presence of calcium hydroxide (Ca(OH)2). The pH increase caused by Ca(OH)2 was generally more significant, as it is a highly alkaline substance. Rising pH values (7.73 \(\rightarrow\) 8.19) could indicate that a solution is alkalinizing, but other alkaline substances such as carbonates (e.g., sodium carbonate) can also be responsible. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Material** & **Reaction to Flame** & **Dissolution** & **pH Value** & **Temperature [\({}^{\circ}\)C]** \\ \hline pH 12.55 solutions & & & & \\ \hline ESD & none & full & 10.14 & 21.0 \\ ENG & none & full & 10.31 & 20.9 \\ HI & none & full & 10.39 & 20.2 \\ ABS & none & uneven & 10.62 & 21.2 \\ GYP & decolorization & uneven & 10.81 & 21.6 \\ \hline
**Material** & **Reaction to flame** & **Dissolution** & **pH Value** & **Temperature [\({}^{\circ}\)C]** \\ \hline pH 12 solutions & & & & \\ \hline ESD & none & full & 10.47 & 22.5 \\ ENG & none & full & 10.66 & 22.9 \\ HI & none & full & 10.17 & 22.0 \\ ABS & none & uneven & 10.19 & 24.1 \\ GYP & none & full & 10.17 & 23.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Flame test and pH measurement test results of the white matter. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Observed Period in Weeks** & **pH Value** & **Temperature [\({}^{\circ}\)C]** \\ \hline
1 st & 7.75 & 21.2 \\
2 nd & 7.99 & 21.0 \\
3 rd & 8.05 & 21.2 \\
4 th & 8.19 & 21.4 \\
8 th & 8.10 & 20.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: pH and temperature changes in aqueous medium over four weeks plus one week. It is also possible that the chemical equilibrium of the solution is altered, for example, by loss of carbon dioxide, which could cause natural alkalinization. This issue needs further investigation. In the third week of the observations, white crystals, similar to the white material observed in the dissolution tests, appeared on the concrete elements in all cases right next to or on the reinforcing element. The observed white crystalline particles are presented in Figure 17.  
Another observation outside the appearance of crystals was the behavior of PLA-based materials. In several parts, especially HI, the material was exposed to water due to fracture and disintegrated on contact. ENG, GYP, and ESD were smeared. As shown in Figure 18, HI was the most severely affected by the material condition. While ABS was completely intact compared to the other PLA-based materials, ENG, GYP, and ESD samples were smearable with HI, which even showed fiber degradation. Figure 17: Occurrence of white crystals on the reinforced concrete beams kept underwater for four weeks. Figure 18: The smearable texture on paper of PLA materials exposed to water in week 3. These observations were necessary, as only by measuring the pH of the medium in a continuous flow could it be determined whether the white matter released was lime leached from the concrete. Since Ca(OH)\({}_{2}\) forms an alkaline solution in water, the pH of the water will be higher than 7. The alkalinity of the solution (pH around 9-12) could be quickly determined by using a pH meter.