Recipe Geopolymer

I’ve redacted the above geopolymer formula to make it a little more readable, and added some notes:

== Prasad and Shahoma McAlister’s GP#8 ==

Step (A) … alkaline solution

– 320g lye [sodium hydroxide, drain cleaner]
– 1 liter water
– ~2.5 liters sodium silicate [SS40?]

# Stir lye slowly, with care, into water (never water into lye!).
# Gets very hot!
# Let rest 12 hours… it’s “dissolving”.
# Mix 1 part of this lye solution with 2.5 parts sodium silicate.
# That’s it!

Step (B) … Basic GP binder #8

– 4.5 parts metakaolin [750*C calcined kaolin]
– 0.5 part “Type S” hydrated lime
– 8 parts aggregate (sand mix)
– alkaline solution as needed (~1/3 by weight of metakaolin)

# Mix dry ingredients
# Stir in just enough alkaline solution to yield stiff mix
# Keep the liquid content as low as possible.
# Ta-daa!
# Cure like concrete, warm and moist (under plastic?).

Rough ratios:
.33 : 1 : 2.5 == lye:water:SS40
4.5 : .5 : 8 : ~1 == pozzolan:hydrated-lime:sand:alk-sol

Note: “Class C” fly ash can replace both the metakaolin and hydrated lime by weight. “Type F” fly ash can replace only the metakaolin. Metakaolin and fly ash are both pozzolans, and Class C fly ash contains enough quicklime (CaO) to replace the type-S hydrated lime (roughly CaOH2).

Thoughts: These components seem reactive enough to fudge the ratios and still get results. Does “part” refer to weight or volume? “Sand mixture” usually means a mixture of powdered, fine, and course sand or other aggregates (gravel, glass, vermiculite). It may be possible to incorporate much larger aggregates, especially chunks of limestone pre-moistened by the alkaline solution (refer to Davidovits

For anyone who might be interested, here is a starting point for a simple geopolymer recipe. In Joy, Prasad

Geopolymer cement notes.
The making of alkaline solution:
*12 hr before mixing, slowly! dissolve 320gm sodium hydroxide (pure lye, as in a drain cleaner) into a liter of water. This should be stirred in slowly, with care, wearing gloves and goggles as it is very caustic. This mix will generate some heat while dissolving.
*After the lye solution is fully dissolved (12hr) mix one part lye solution with 2 1/2 parts sodium silicate. (available at pottery supplies)

* Basic recipe #8
4 1/2 parts metakaolin [Ed.: heat treated kaolin]
1/2 part lime (type-S)
8 parts aggregate (sand mix)
alkaline solution as needed (about 1/3 the amount of metakaolin and ash, by weight)

*Mix all the dry ingredients together then stir in just enough alkaline solution to make a stiff mix. Keep the liquid content as low as possible. Cure like concrete, warm and moist.
*Class C fly ash can replace the metakaolin and lime, if its type F fly ash replace only the metakaolin.

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