## 5 Results and Discussion
### Stage 2--TES Properties in the Fireplace Operational Conditions
The thermographic examination was carried out in order to detect possible anomalies, i.e., an intensified infrared radiation for selected materials, which would not be compatible with temperature readings obtained from the thermocouples. The thermal images of the ceramic materials, concretes, and natural stone were similar in quality. This fact may indicate that concrete composites can fulfill the functions of heat radiators that have traditionally been made in old fireplaces made of ceramic and stone materials. As in the case of the first stage of the experiment, the thermal power of the materials tested was calculated and the results are shown Table 8. The comparison of the thermal power between samples  
Figure 5: The relation of the temperature drop as a function of the cooling time during the second stage of the experiment; designations are the same as for Figure 4.  
subjected to the low temperature load (stage 1) and the fireplace operational temperature are shown in Figure 6.  
The thermal power of the materials heated to 400 \({}^{\circ}\)C ranges from 6.2 (for steel) to 11.4 (for aerated concrete) times greater than the materials' thermal power obtained during the first stage of the experiment. Previously, only the steel obtained higher thermal power than the concrete samples. In the second stage the highest thermal power was achieved by the CGA-PC concrete. All tested concretes had a thermal power greater by an average of 82% than other materials (excluding steel). In addition, the largest increases in the thermal power (between the first and the second stage of the experiment) were achieved in the concretes and the steel sample. This shows that the TES properties of these materials are better when they operate at elevated temperature conditions. Testing at the operating temperature of the fireplace shows that the concretes (including the fireproof concrete with ceramic waste aggregate) have very good TES properties, and in combination with high durability can successfully be used as a heat accumulator in the construction industry. After conducting the research, specimens were left in a laboratory for a period of two weeks, after which their inspection was made. The samples made of concrete with gravel aggregate (CGA-PC, CGA-AC) showed damage in the form of cracks (Figure 7). A similar type of damage was observed for  
Figure 6: Comparison of the materials’ thermal power between the results obtained in the course of the first and the second stages of the experiment. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Material Type** & **S** & **AC** & **SLB** & **CB** & **FB** & **CGA-PC** & **CGA-AC** & **CCA-PC** & **CCA-AC** & **G** \\ \hline \(m\) (kg) & 2.078 & 0.252 & 0.465 & 0.536 & 0.439 & 0.574 & 0.575 & 0.52 & 0.56 & 0.666 \\ \(c\) (0/(kg-K)) & 449 & 1130 & 800 & 850 & 850 & 1130 & 1130 & 1130 & 1130 & 670 \\ \(\Delta T\) (K) & 212 & 233 & 244 & 243 & 306 & 257 & 267 & 261 & 260 \\ \(\Delta Q\) (k) & 197.8 & 66.3 & 90.8 & 110.7 & 89.6 & 198.5 & 167.0 & 156.9 & 165.2 & 116.0 \\ \(t\) (s) & 3600 & 3600 & 3600 & 3600 & 3600 & 3600 & 3600 & 3600 & 3600 & 3600 \\ \(P\) (W) & 54.94 & 18.43 & 25.21 & 30.75 & 24.88 & 55.13 & 46.38 & 43.58 & 45.88 & 32.23 \\ \hline \hline \end{tabular} where: \(m\) sample weight, \(c\): specific heat, \(\Delta T\): temperature difference, \(E=\Delta Q=c\cdot m\cdot\Delta T\): amount of emitted energy, \(t\): emission time, \(P\): thermal power.  
\end{table} 
Table 8: The thermal power of materials tested—second stage of the experiment. the concrete made of ceramic aggregate and Portland cement (CCA-PC). Damage occurred as a result of too high a temperature during the heating process. Other materials remained intact, including the CCA-AC concrete. Damage after heating the concretes based on Portland cement (CGA-PC, CCA-PC) made it impossible to determine their basic mechanical properties--the compressive and tensile strength. The edges of the samples flaked off after heating, and the loss of their mass was noted.