# Study About the Influence of Diatoms on the Durability of Monumental Limestone
## 3 Results and Discussions
### Frost Resistance Test Results  
Table 7 presents the percentages of mass loss experienced by the control and diatom samples after the freeze-thaw cycles. Data indicate that the control samples exhibited approximately 17% greater mass loss compared with the diatom samples. Note that this difference may be even greater, as traces of nondiatom green algal fibers from the biofilm pool were detected in the water used during the freeze-thaw cycles of the diatom samples.  
In addition to determining the percentage of mass loss after 45 freeze-thaw cycles, two water absorption parameters were evaluated. First, the capillary water absorption capacity was measured using a water sheet of 3 \(\pm\) 1 mm thickness, both before and after the freeze-thaw cycles, as shown in Figure 24a,b. Prior to the freeze-thaw test, the control samples exhibited higher water absorption than the diatom samples. However, after the 45 cycles, the results favored the diatom samples, which absorbed 0.28 g less water after 48 h, compared with the control samples, which absorbed 0.73 g more water. This suggests that the presence of diatoms imparts a protective effect against freeze-thaw damage.  
The samples were also subjected to the pipette test after the freeze-thaw process. The results, shown in Figure 25, indicate that the diatom samples took longer than the control samples to absorb each increment of 0.1, 0.2, 0.3, 0.4, and 0.5 mL of water. This suggests that water penetration into the diatom samples was slower and more difficult. Furthermore, as the volume of absorbed water increased, the trend line for the diatom samples progressively diverged from that of the control samples, with a steeper slope. This means that, for each 0.1 mL increment absorbed, the time required by the diatom samples to absorb it increased more than that of the control samples. Over time, water penetration and absorption decreased more significantly in the diatom samples compared with those in the control samples.  
\begin{table}
\begin{tabular}{l c c} \hline \hline _Value_ & **Average Control** & **Average Diatom** \\ \hline
**\% mass loss** & \(-\)0.42\% & \(-\)0.35\% \\ \hline
**Standard deviation** & \(\pm\)0.19 & \(\pm\)0.042 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Percentages of mass loss experienced by the control and diatom samples after freeze–thaw cycles.  
Figure 23: Representation of the volume of water absorbed after 24 h in the control and diatom samples.  
Figure 24: Mass increase of samples in contact with water sheet (**a**) before being subjected to ice cycles and (**b**) after being subjected to ice cycles.  
Figure 25: Average time elapsed until absorbing the different volumes of water.  
Focusing on the results obtained after 24 h, Figure 26 shows that the samples with diatoms absorbed an average of 0.90 mL of water, while the control samples absorbed 1.23 mL. This indicates that, after undergoing 45 freeze-thaw cycles, the diatom samples absorbed 27% less water than the control samples. Additionally, the test results reveal that the mass loss in the diatom samples was greater than in the control samples following these cycles.  
This test provides a useful comparison between the initial state before the freeze-thaw cycles and the final state after the cycles for each sample type independently. However, to better compare the control and diatom samples after freeze-thaw exposure, a more targeted test focusing only on the upper surface of the diatom-treated samples is advisable. For this purpose, the water absorption test using the pipette method was selected, with results indicating better performance in the diatom samples. Therefore, it cannot be conclusively stated that the freeze-thaw cycles negatively impacted the antiabsorption properties of the diatom-treated samples.