I am worried that bentonite will work as precursor for geopolymers. The best clay, so for, used for geopolymerization is calcined kaolin (metakaolin). Very recently, laterite was found as active precursor for geopolymerization, but the strength of the geopolymers was not enough.

Hello, I think you have to consider the mineralogy of your bentonite, because this clay mineral isn't the best for geopolymerization. Also it usually contains organic matter and this could be other problem...but if you want to use bentonite you could do calcining test at different temperatures, I suggest you from 650 to 800°C' for 2 or 4h to know what will be the best . You could mix bentonite with metakaolin in your binder, only bentonite hasn't the correct mineralogy and amorphous minerals content to react efficently with alkaline liquid, if you want lower efflorescence use K based ,but if you need reduce cost could use Na based taking care to mixing procedure to avoid risk of efflorescence. Mechanical properties should be quite the same. Probably this system is low in CaO, this depends on your bentonite, so you need temperature to improve geopolymerization 60-70°C for 24h will be enough.

Many Thanks for bot respected researchers.  Your valuable comments are highly appreciated.

Hi Amr Ibrahim Ibrahim Helmy

In theory all inorganic material with enough SiO2 and Al2O3, can form a geopolymer. The point is, that the silica must dissolve with the alkaline mixture NaOH / Na2SIO3. I suggest using 12 M NaOH and the Na2O . 2 SiO2, formulation silicate, which is the most commercial. The ratio solution volume / bentonite = 0.38 L / kg. Thermal activation: 24 h at 30 ° C followed by 24 h at 80 ° C. If water is added, it must be enough to achieve a workability 30 minutes after mixing, before the setting begins. As there are two types of bentonite, sodium and calcium, you must specify what type you are geopolitizing.