## 5 Discussion  
According to [PERSON] [28], there are three stages in the synthesis of geopolymers, and these stages are:  
Dissolution;  
Coagulation-condensation;  
Condensation-crystallization. During the dissolution stage, the high concentration of OH\({}^{-}\) in the system is responsible for the breakage of Si-O-Si, Si-O-Al, and Al-O-Al bonds of the soluble glassy aluminosilicate phases, forming Si-OH and Al-OH groups [29], causing an increase in the pH of the medium, as observed in Figure 11. The appearance of \(\equiv\) Si-O\({}^{-}\)-Na\({}^{+}\) bonds prevents the Si-O-Si bonds from reforming again. The aforementioned alkali silicate bonds can contribute to ion exchange and types of complexes such as Si-O-Ca-OH. With Al-O-Si bonds, the same type of reaction happens and ends up generating predominantly Al(OH)\({}_{4}\)\({}^{-}\)-type complexes. The -Si-O-Na\({}^{+}\) complexes are stable in an alkaline medium, thus fulfilling a transport role and allowing the development of a coagulated structure (colloidal phase) based on the abovementioned units. In the coagulation-condensation stage, due to the high pH > 11, the disintegration of the Si-O-Si bond gives rise to hydroxylated complexes, with Si(OH)\({}_{3}\)O\({}^{-}\) as the most stable component, which condenses and forms a new Si-O-Si bond. The OH\({}^{-}\) ion acts as a catalyst for the reaction. The polyhydroxylan groups are formed by the polymerization of orthosilicic acid and can grow in all directions, leading to the formation of colloidal particles. The formation of the hydroaluminogel depends on the pH of the medium. For the condensation-crystallization stage, in addition to the microparticles formed from the condensation, the particles of the solid phases coming from the source (copper flotation tailings in the case of this research) indicate the precipitation of products that are  
Figure 19: Permeability test results of the created geopolymers. dependent on the mineralogy and chemistry of the initial phase, as well as the nature of the alkaline component and the hardening conditions. According to the study by [PERSON] et al. [30], the simple compressive strength could be improved due to the coupling effect of calcium aluminosilicate gel (C-A-S-H), calcium silicate gel (C-S-H), and sodium aluminosilicate gel (N-A-S-H) in the hydration of alkali-activated fly-ash-based geopolymer products; however, for the present study and given that the percentage of calcium present according to the ICP test was 3.28% in the copper flotation tailings, the same analysis cannot be done. It is suggested to carry out future research by making geopolymeric mixtures with calcium addition and studying their behavior. The carbonation mechanism in alkali-activated geopolymers is different from that in Portland cement since, in Portland cement pastes, atmospheric CO\({}_{2}\) dissolves in the pore solution and reacts rapidly with portlandite to form CaCO\({}_{3}\) and then with a calcium-silicate-hydrate (C-S-H) gel to form CaCO\({}_{3}\) and silica gel; in contrast, the carbonation of alkali-activated pastes occurs directly in the calcium-aluminosilicate-hydrate (C-A-S-H) gel due to the lack of portlandite, leaving an alumina-containing silica gel remaining, in addition to CaCO\({}_{3}\)[31; 32]. Relative humidity of 95% in the curing chambers can inhibit initial carbonation in geopolymers [33]. On the other hand, the dissolution of calcium in sources processed in a low alkalinity system, which was not the case in this research, provides good resistance to simple compression due to the formation of C-S-H gel (calcium-silicon-H\({}_{2}\)O) that coexists with the geopolymer gel (N-A-S-H), which complements each other and forms a mostly amorphous structure that provides better mechanical behavior. For aluminosilicate sources, such as copper flotation tailings, very little calcium is dissolved (the percentage of calcium present according to the ICP test was 3.28% in copper flotation tailings), causing a C-S-H gel not to form.