NaOH and KOH are suitable for geopolymer synthesis because they are strong alkali metal hydroxides that effectively dissolve aluminosilicate sources, promoting the geopolymerization process. These alkalis increase the pH significantly, facilitating the breakdown of the aluminosilicate structure and enabling the release of Al and Si ions necessary for forming the geopolymeric network.

In contrast, Ca(OH)₂ and Mg(OH)₂, hydroxides of alkaline earth metals, are less effective because they have lower solubility in water and provide insufficiently high pH levels. Additionally, Ca ions tend to promote hydration reactions rather than true geopolymerization, leading to calcium silicate hydrate (C-S-H) formation instead of the desired aluminosilicate network. This difference limits the effectiveness of Ca and Mg hydroxides in creating stable geopolymeric bonds and structures.

Dear Hasan Altawil,

Thanks a lot for your answer