Feasibility of producing geopolymers from two different Tunisian clays before and after calcination at various temperatures

Two Tunisian clays, kaolinitic from the Tabarka (Clay T) region and illito-kaolinitic rich in hematite from the Medenine (Clay M) region, are tested as potential aluminosilicate sources for the synthesis of geopolymers. The raw clays and clays calcined at 700, 800, 850 and 900°C were characterized using XRD, DTA/TG, and FTIR spectroscopy and 29Si and 27Al MAS NMR measurements. It was demonstrated that samples based on Clay M present more reactivity than those based on the Clay T because of the amorphization of clay minerals. The structural evolution on calcination is studied in detail to predict the behavior of the clay during geopolymerization. Despite its lower content in kaolinite than Clay T, Clay M is capable of providing geopolymers. •Two Tunisian clays Tabarka (Clay T) and Medenine (Clay M) are tested as potential aluminosilicate sources for the synthesis of geopolymers.•The raw clays and calcined at (700–900°C) were characterized using XRD, DTA/TG, FTIR and NMR measurements.•It was demonstrated that samples based on Clay M present more reactivity than those based on the Clay T because of the amorphization of clay minerals.•The structural evolution on calcination is studied in detail to predict the behavior of the clay during geopolymerization.•Despite its lower content in kaolinite than Clay T, Clay M is capable of providing geopolymers.