## 3 Results and Discussion
### Results of the Characterization of Raw and Sintered Samples
#### 3.2.3 Results of the Leaching Tests of the Raw and Sintered Samples  
From the obtained results of ICP analysis in Table 4, it can be observed that the concentrations of all examined elements in the samples GC15 and GC20 were lowered after being thermally treated at 750 \({}^{\circ}\)C for 80 h, except for Cr. The increased mobility of Cr after the sintering process can be explained by the fact that, unlike Hg and Cd, Cr is considered nonvolatile and tends to reside in the material after being sintered at certain temperatures [33]. Moreover, some studies have reported that heat treatment might promote the Cr leaching behavior of samples, which, therefore, might exhibit relatively higher Cr leaching accumulation after exposure to high temperatures up to 750 \({}^{\circ}\)C [34]. However, the values of leached Cr do not practically pass the limitation if we consider a permissible measurement error of \(\pm\)2.5%. Also, the leached concentrations of As for the raw samples exceed the maximum allowed concentration values for the classification of waste as nonhazardous, according to the _Rulebook on Categories, Testing and Classification of Waste (\"Standard Sl. Glasnik 56/2010\")_, as well as EN 12457/EN 16192: 2011, which applies in the Republic of Serbia to the disposal of nonreactive hazardous waste. Nevertheless, after exposure to high temperatures, which are inevitable in the operating environment of refractory ceramic adhesives and IT-SOFC sealants, these concentrations decreased to acceptable values below the prescribed limits. In addition to the concentrations of all the leached elements for the examined GC samples, the pH values measured before and after the leaching tests of the examined GC samples are given in Table 4. \begin{table}
\begin{tabular}{c c c c c c} \hline \multicolumn{6}{c}{**Concentration, mg/kg, in Adhesive and Sealant Samples’ Composition**} \\ \hline
**Parameter** & **GC\({}_{15}\) Raw** & **GC\({}_{20}\) Raw** & **GC\({}_{15}\) Sint** & **GC\({}_{20}\) Sint** & **Ref. Values** \\ \hline pH before test & 10.91 & 10.92 & 11.71 & 11.52 & - \\ pH after test & 10.67 & 10.67 & 10.9 & 10.39 & - \\ \hline Al & 132.4 & 104.1 & 257.1 & 120.1 & - \\ As & 3.282 & 3.29 & 0.02452 & 0.2154 & 2 */25 ** \\ Ca & 64.96 & 58.45 & 769.1 & 616.1 & - \\ Cd & 0.008039 & 0.008372 & 1 UDV & UDV & 1 */5 **- \\ Co & 0.1895 & 0.2401 & 0.008266 & 0.02789 & - \\ Cr & 0.09819 & 0.1081 & 10.11 & 10.25 & 10 */70 ** \\ Cu & 2.395 & 2.761 & 0.4003 & 0.7381 & 50 */100 ** \\ Fe & 12.18 & 13.63 & 0.3947 & 2.701 & - \\ Hg & 0.001594 & 0.000053 & 0.000661 & 0.000223 & 0.2 */2 ** \\ K & 187.3 & 198.2 & 62.92 & 92.2 & - \\ Mg & 17.66 & 16.44 & 34.25 & 35.56 & - \\ Mn & 0.4034 & 0.4925 & 0.009729 & 0.08828 & - \\ Mo & 1.89 & 2.659 & 2.86 & 3.452 & 10 */30 **- \\ Na & 25770 & 26420 & 693.1 & 2532 & - \\ Ni & 0.1875 & 0.1983 & UDV & 0.01233 & 10 */40 ** \\ P & 1514 & 1802 & 0.4047 & 52.39 & \\ Pb & 0.9608 & 1.265 & 0.07941 & 0.2532 & 10 */50 ** \\ S & 792.7 & 839.4 & 299.7 & 323.3 & \\ Se & 0.192 & 0.2617 & 0.009627 & 0.01374 & 0.5 */7 ** \\ V & 1.248 & 1.242 & 0.9937 & 1.106 & \\ Zn & 0.1989 & 0.3054 & UDV & 0.02292 & 50 */200 ** \\ \hline \end{tabular} \({}^{1}\)UDV- under detection values. According to \({}^{\circ}\)_Standard Sl. Glasnik 56/2010\({}^{\circ}\)_, * _values refer to the disposal of nonreactive hazardous waste in landfish for nonhazardous waste in fields that are not used for disposal of biodegradable waste. ** values refer to the disposal in landfish for hazardous waste._  
\end{table} 
Table 4: Results of leaching test for raw and sintered samples GC\({}_{15}\) and GC\({}_{20}\). 3.2.4. Results of the Dilatometry Analysis of the Raw Samples  
The dilatometry analysis curves of percentage linear changes in all the compacted GC samples from RT to 800 \({}^{\circ}\)C are presented as a function of temperature in Figure 7a and as a function of heating time in Figure 7b.