## 3 Results and Discussion
Figure 7: Simultaneous thermal analysis with mass spectroscopy of MOC 5-1-8 measured in inert atmosphere  
The residual structural parameters of MOC 5-1-8 phase samples exposed to selected elevated temperatures are summarized in Table 2, together with the water absorption and compressive strength data. The obtained data represent an average from five measured specimens. For comparison, the reference data obtained for samples cured at a laboratory temperature of \(22\pm 2\)\({}^{\circ}\)C are also given. These samples were labeled MOC 20. Symbols MOC 150, MOC 250, and MOC 350 stand for MOC samples heated for 2 h at 150 \({}^{\circ}\)C, 250 \({}^{\circ}\)C, and 350 \({}^{\circ}\)C, respectively. The compressive strength of the reference material was similar for samples cured for 96 h to the 28-day compressive strength of Portland cement paste made of CEM I 42.5 and a water/cement ratio of 0.5 [33]. As reported by [PERSON] et al., the 28-day compressive strength of CEM 32.5 is \(\sim\)48 MPa, which is significantly lower than that measured for MOC 20 and MOC 150 samples and similar to the strength of MOC 250. In the measurement of water absorption, MOC 20 samples dissolved in water. Due to that, the moisture content of specimens was not possible to measure. On the other hand, the heating of MOC samples at elevated temperatures increased the durability of these materials against disruptive moisture effects. In comparison with the reference samples (MOC 20), the release of six molecules of water at 145 \({}^{\circ}\)C led to a decrease in bulk density (7.8%) due to the water evaporation, an increase in specific density (5.2%) as a result of material shrinkage, and an increase in porosity of MOC 150 samples, which was 96.5% and corresponded to high water absorption. Surprisingly, the compressive strength remained almost unaffected by the material structural changes. The heating to 250 \({}^{\circ}\)C led to the loss of two other water molecules, which resulted in a significant drop in bulk density (25.4%), an increase in porosity (284%), and a loss of compressive strength (11.3%) of MOC 250 samples compared to the reference material. The water absorption of MOC 250 samples was high and was in agreement with the increased porosity. Although the structural changes were significant, the mechanical strength of MOC 250 samples was considered as good in general. On the other hand, samples exposed at 350 \({}^{\circ}\)C exhibited a significant drop in the compressive strength (78.9%) compared to the unheated samples. This was in agreement with the decrease in bulk density (35.5%) and increase in porosity (386%). The water absorption was about 41% higher compared to that measured for MOC 250. The temperature-dependent compressive strength and porosity data are graphed for clarity in Figure 8. Based on the plotted compressive strength and porosity curves, the critical temperature for the studied MOC 5-1-8 phase was identified at 250 \({}^{\circ}\)C. A higher temperature of exposure led to a significant drop in the compressive strength. \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Material**} & \(\rho_{b}\) & \(\rho_{s}\) & \(\psi\) & \(W_{a}\) & \(f_{c}\) \\  & **(kg/m\({}^{3}\))** & **(kg/m\({}^{3}\))** & **(\%)** & **(Mass \%)** & **(MPa)** \\ \hline MOC 20 & \(1613\pm 29\) & \(1820\pm 22\) & \(11.4\pm 0.2\) & a & \(54.8\pm 0.8\) \\ \hline MOC 150 & \(1487\pm 27\) & \(1916\pm 23\) & \(22.4\pm 0.4\) & \(15.2\pm 0.2\) & \(53.8\pm 0.8\) \\ \hline MOC 250 & \(1204\pm 22\) & \(2142\pm 26\) & \(43.8\pm 0.8\) & \(36.8\pm 0.4\) & \(48.6\pm 0.6\) \\ \hline MOC 350 & \(1041\pm 19\) & \(2339\pm 28\) & \(55.5\pm 1.0\) & \(51.9\pm 0.6\) & \(11.6\pm 0.16\) \\ \hline \end{tabular}  
* Samples dissolved in water.  
\end{table} 
Table 2: Structural and mechanical parameters of MOC 5-1-8 phase samples.