## 3 Results and Discussion
### Characterization of the Used WB.
The presence of the band at 1084 cm\({}^{-1}\) could indicate that the used mixture contained kaolinite clay [48]. The FTIR spectra of the two cake mixtures, before calcination, indicated that that Jed-Brick cake exhibited a different spectrum compared to Med Brick, due to the different clays in their mixtures. Indeed, the Jed Brick exhibited strong bands related to kaolinite clay mineral at 3700 and 3612 cm\({}^{-1}\)[48], in addition to the bands of silica phase. While, the Med-Brick mixture contains mainly silica with characteristic band of 1029 cm\({}^{-1}\) and other weak bands in the ranges of 3300 to 2800 cm\({}^{-1}\) and from 1500 to 500 cm\({}^{-1}\)[49]. The band at 1424 cm\({}^{-1}\) was related to carbonate materials [50]. This band was not observed in the mixture of the Jed-Brick. The hydroxyl bands at 3300 to 2800 cm\({}^{-1}\) vanished due to the dehydroxylation during the calcination process of the mixtures and the shape of the Si-O bands changed to one broad brand, due to the formation of silica phase and other amorphous phases. The WB materials are red, which indicated the presence of iron oxide. The characteristic bands of iron oxide are reported in the range of 526 and 436-459 cm\({}^{-1}\)[51], however, in our case, it was difficult to detect these bands, which could indicate that the iron oxide was dissolved into the silica phase, as reported in previous studies. The FTIR spectra of the base treated samples (not shown) were similar to the raw waste bricks, indicating that the base treatment did not alter the structure of the waste bricks and the silica phase was stable during the base treatment. The TGA curves of the starting cakes before calcinations are presented in Figure 3. The Medina cake exhibited a mass loss from room temperature (RT) to 200 \({}^{\circ}\)C, related to the water molecules physisorbed, and a second one starting from 450 to 700 \({}^{\circ}\)C, associated with the dehydroxylation of the used mixture and the release of carbonate materials, mainly calcium carbonate (as indicated by FTIR) [52]. The total mass loss was about 25%. The Jed- brick cake exhibited similar steps, however, with a shift to low temperatures at the second mass loss. Indeed, the DTG curve exhibited a maximum temperature loss at 450 \({}^{\circ}\)C, with a total of 15% mass loss. This difference could be related to the composition and the types of clays in both mixtures. However, the waste bricks exhibited different features and only a negligible mass loss of 2% was detected in the ranges of 100-600 \({}^{\circ}\)C and 600-900 \({}^{\circ}\)C, indicating that the raw materials of bricks were fired at temperatures higher than the temperature of dehydroxylation and they were completely dehydroxylated. The TGA of the base treated waste brick (not shown) features exhibited similar ones to the pristine materials, indicating that there was no effect of the base treatment on the structure of these materials. The SEM micrographs, presented in Figure 4, reveal that the two WB have different morphologies, The Med-WB exhibited a compact appearance, which was free of pores and had plate-shaped grains [33]. The Jed-WB also had a compact appearance, with a different aggregation of the particles. After the treatment with the NaOH solution, no alterations of the particle shapes were observed for both WB materials. Figure 4: SEM micrographs of (**a**) Med-WB and (**b**) Jed-WB materials. (**a**\({}^{\prime}\)) and (**b**\({}^{\prime}\)) correspond to (**a**) and (**b**) after treatment with NaOH solution, respectively. Figure 3: TGA features of (**b**) Med-WB and (**d**) Jed-WB materials. (**a**,**a**\({}^{\prime}\)) and (**c**,**c**\({}^{\prime}\)) correspond to TGA (solid lines) and DTG (dashed lines) of the Med and Jed cake mixtures before firing. The nitrogen adsorption isotherms exhibited a type II for both materials, characteristic of non-porous materials, the high adsorbed nitrogen volume was related to the capillary condensation of nitrogen gas at a higher relative pressure.