Clay based geopolymers need waterglass to become dense and strong enough,
even if the clay is calzined at 750°C.
Grog becomes dense by calcining above 1000°C and thus does not require waterglass,
however grog and clay mixtures likely require waterglass, depending on the percentage of clay.
For clay based just add water mixtures one could use waterglass powder.
The pozzolanic activity of natural clay is low and thus some metakalolin,
or other lightweight pozzolans like perlite, white wood ash, fly ash etc. is required.
The much higher density of grog may cause segregration if mixed with natural clay.
Segregration of grog clay mixtures can be prevented by a very short potlife.
White clays and grogs are preferable, as the iron in reddish clays may disturb the polymerisation.
For the same reason light colors are preferable for pozzolans too.
Typicaly perlite contains much lower amounts of iron than vermiculite.
Pozzolans with high reactivity like fly ash, granulated slag or grog tolerate more iron than natural pozzolans.
In water solutions calcium hydroxide can take away the carbon from carbonates of alkali metals such as
Lithium, Sodium, Potassium, leaving them as their hydroxide.
Ca(OH)2 + Li2CO3 → CaCO3 + 2 LiOH.
Ca(OH)2 + Na2CO3 → CaCO3 + 2 NaOH
Ca(OH)2 + K2CO3 → CaCO3 + 2 KOH.
Thus in mixtures with lime or cement the hydroxides of alkali metals can be replaced
by their more user friendly carbonates for alkaline activation.
A geopolymer is basically one or more alkali cations such as potassium, sodium or calcium
with silicon oxide and aluminium oxide.
www.geopolymer.org/fichiers_pdf/KIEV.pdfEven a mixture of portland cement and reactive alumosilicates can be a geopolymer.
www.google.com/patents/US4842649 Pyrament® which is often mentioned as a sample of success of the geopolymer technology was made of 80 % portland cement.
Even pure portland cement will not spall if it contains enough porous material to let steam escape.
BTW, where are you lokated ?
