## 4 Results and Discussion
### Technological Characterization of Fired Products  
The linear shrinkage increases with the firing temperature (Figure 8a). The loss of weight varies between 5 and 17%. The values are almost constant for all the firing temperatures (Figure 8b). This may be justified by the low organic contamination of the samples or to the predominance of clay minerals. The flexural strength increases with the firing temperature because of an increase in densification (Figure 8c). This densification is supported by the XRD patterns, in which an increase in mullite formation with temperature is noticeable. The highest value obtained was 15.75 MPa for sample BR5 fired at 1100 \({}^{\circ}\)C. For all other samples, the highest value of flexural strength was reached at 1100 \({}^{\circ}\)C (Figure 8c). This can be explained by the high Al\({}_{2}\)O\({}_{3}\) content [34] and/or the increased formation of a dense phase, such as mullite during sintering [35]. The bulk density (Figure 8d) followed the same trend as the flexural strength,  
Figure 5: TG-DSC of Lokoundje alluvial materials. which was consistent with the proposed increase in density upon firing, because of dense phase formation. Between 800 and 1000 \({}^{\circ}\)C, the bulk density is almost constant. This may be due to the similar mineralogical composition of the samples, in which the main dense phases are quartz and a primary mullite from 1000 \({}^{\circ}\)C (Figure 7). The density of the BR5 sample was also the highest among the series. Given that its clay size fraction, from particle size analyses, was the highest (76%) for the GR2 sample, then the mullite formation from sintering was higher in these samples compared to others. The difference reached in the flexural strength was probably due to crystallinity differences, which may affect the kinetics of mullite formation. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{2}{c}{**Temperature**} & \multirow{2}{*}{**Color**} & \multirow{2}{*}{**Sound**} & \multirow{2}{*}{**Cohesion**} \\  & & (\({}^{\circ}\)C) & & & \\ \hline \multirow{4}{*}{BR-5} & 25 & Pale brown & - & - \\  & 800 & Light red & Metallic & Good \\  & 900 & Light red & Metallic & Good \\  & 1000 & Light red & Metallic & Very good \\  & 1100 & Light red & Metallic & Very good \\ \hline \multirow{4}{*}{BR-8} & 25 & Pale brown & - & - \\  & 800 & Reddish yellow & Metallic & Good \\  & 900 & Reddish yellow & Metallic & Good \\  & 1000 & Light red & Metallic & Good \\  & 1100 & Light red & Metallic & Very good \\ \hline \multirow{4}{*}{BR-9} & 25 & Light gray & - & - \\  & 800 & Reddish yellow & Metallic & Weak \\  & 900 & Light red & Metallic & Average \\  & 1000 & Red & Metallic & Average \\  & 1100 & Dark red & Metallic & Good \\ \hline \multirow{4}{*}{BR-11} & 25 & Reddish yellow & - & - \\  & 800 & Reddish yellow & Metallic & Good \\  & 900 & Reddish yellow & Metallic & Very good \\  & 1100 & Light red & Metallic & Good \\ \hline \multirow{4}{*}{GR-2} & 25 & Brownish gray & - & - \\  & 800 & Reddish brown & Metallic & Good \\  & 900 & Pink & Metallic & Good \\  & 1100 & Pink & Metallic & Good \\ \hline \multirow{4}{*}{GR-3} & 25 & Light gray & - & - \\  & 800 & Pinkish white & Metallic & Good \\  & 1000 & Pinkish white & Metallic & Very good \\  & 1100 & Pink & Metallic & Good \\ \hline \multirow{4}{*}{GR-6} & 25 & Brownish gray & - & - \\  & 800 & Reddish yellow & Metallic & Good \\  & 900 & Reddish yellow & Metallic & Good \\  & 1000 & Pink & Metallic & Very good \\  & 1100 & Pink & Metallic & Very good \\ \hline \multirow{4}{*}{GR-8} & 25 & Pale brown & - & - \\  & 800 & Light red & Metallic & Good \\  & 900 & Light red & Metallic & Good \\  & 1000 & Light red & Metallic & Very good \\  & 1100 & Light red & Metallic & Very good \\ \hline \end{tabular}
\end{table} 
Table 3: Color, sound, and cohesion of the raw materials and fired products. Figure 6: Pictures of specimens.