## 3 Results and Discussion
### Chemical Composition Analysis
#### 3.1.2 Discussion on the Content of Fluxing Oxide Content  
Fe\({}_{2}\)O\({}_{3}\), sodium oxide (Na\({}_{2}\)O), potassium oxide (K\({}_{2}\)O), calcium oxide (CaO), and magnesium oxide (MgO) can all be called fluxes, which can reduce the temperature of melt formation during the firing of aggregates and can affect the temperature range of material softening [44; 45; 46]. It can be seen from Table 3 that the fluxing oxide content of Sample A was 15.09%. It can be expected that the addition of Sample A can reduce the sintering temperature of the aggregates. However, the fluxing contents of Sample B and Sample C were extremely low (2.36% and 2.21%, respectively), which means they may not be able to effectively reduce the sintering temperature of the aggregates.  
1.3 Discussion on the Ratio of SiO\({}_{2}\) + Al\({}_{2}\)O\({}_{3}\) Content to Fluxing Oxide Content  
In the chemical composition of lightweight aggregate source materials, when the ratio of (SiO\({}_{2}\) + Al\({}_{2}\)O\({}_{3}\))/fluxing is 3.5-10.0, it is a better-sintered material [48]. If the ratio is too small, the viscosity of the liquid phase becomes smaller, the bloating gas can more easily escape, and the bloat of the green pellets is poor. Conversely, if the ratio is too large, the required sintering temperature is high, and low-temperature sintering is not conducive to bloat. In other words, the bloating of green pellets consumes, relatively, more heat energy.  
The (SiO\({}_{2}\) + Al\({}_{2}\)O\({}_{3}\))/fluxing ratios of three kinds of textile sludge and water purification sludge are shown in Table 4. Sample A had a ratio of 3.92, Sample B had a ratio of 10.34, and Sample C had a ratio of 12.90. It can be seen from the data that although Sample A was within the range of a better-sintered material, the data were small, its liquid phase viscosity was small, and the bloating gas easily escaped from the surface, resulting in poor bloating performance. In contrast, Sample B and Sample C were not within the range of better-sintered material, indicating that the sintering temperature may need to be higher. Therefore, the three kinds of textile sludge were only added as auxiliary ingredients.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Item**} & \multicolumn{4}{c}{**Code**} \\ \cline{2-5}  & **Sample A** & **Sample B** & **Sample C** & **WPS** \\ \hline SiO\({}_{2}\) (\%) & 14.35 & 6.86 & 4.43 & 58.84 \\ Al\({}_{2}\)O\({}_{3}\) (\%) & 44.83 & 17.55 & 24.07 & 19.30 \\ Fluxing (\%) & 15.09 & 2.36 & 2.21 & 13.08 \\ (SiO\({}_{2}\) + Al\({}_{2}\)O\({}_{3}\))/fluxing & 3.92 & 10.34 & 12.90 & 5.97 \\ \hline \hline \end{tabular}
\end{table}
Table 4: (SiO\({}_{2}\) + Al\({}_{2}\)O\({}_{3}\))/fluxing ratios of different sludge sources.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Fluxing Oxide**} & \multicolumn{4}{c}{**Code**} \\ \cline{2-5}  & **Sample A** & **Sample B** & **Sample C** & **WPS** \\ \hline Fe\({}_{2}\)O\({}_{3}\) (\%) & 0.59 & 1.38 & 0.71 & 6.63 \\ Na\({}_{2}\)O (\%) & 6.76 & 0.40 & 0.21 & 1.15 \\ CaO (\%) & 0.45 & 0.47 & 1.25 & 1.75 \\ K\({}_{2}\)O (\%) & 7.29 & 0.11 & 0.04 & 3.55 \\ Total (\%) & 15.09 & 2.36 & 2.21 & 13.08 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Fluxing oxide compositions of different sludge sources.