Introducing the "famous"
Geopolymer Calculator

The Kriven Formula

Precise geopolymer formulas are hard to find on the Internet. Not because it is big secret but because the field is still in development (=chaos). One of the leading scientists is Waltraud M. Kriven, we'll use her formula on this page for our calculations. This one:
M•AlO2•2SiO2•5.5H2O
Which looks absolutely crazy.

Deciphering the formula

First of all, that capital M at the beginning of the formula is not a chemical element you never heard of but a placeholder for either Sodium (Na) or Potassium (K).

Second, if we omit that bloody oxygen (O) we end up with a much more condensed version:
M•Al•2 Si•5.5 water

In plain English

We want:
  • the same number of "M" (Sodium or Potassium) atoms as Aluminum (Al) atoms in the mix
  • twice as much Silicon (Si) atoms than Aluminum atoms
  • 5.5 times more water molecules than Aluminum atoms

Or in short:

1 part "M", 1 part Aluminum, 2 parts Silicon, 5.5 parts water

Molecular mass and mol

We'll calculate with mols, or 6*1023 atoms (or molecules) at a time. 1 mol material has the convenient property to "calculate" its weight by simply telling "grams" after the molar mass number.

If you are not familiar with these concepts, please learn them before moving on or you'll get lost. Guaranteed.

Example: calculating water's molecular mass

Hydrogen (H) has 1 proton only, so its atomic mass is 1.
Oxygen (O) has 8 protons + 8 neutrons, so it's atomic mass is 16.

What is the molecular mass of water (H2O) then?
1 + 1 + 16 = 18
What is the weight of 1 mol water?
18 grams.
How many mols of H can be found in 1 mol water?
2 mol H.

Molecular masses we use

Atomic masses (atoms) Molecular masses (molecules)
K (Potassium): 39 KOH: 56
Na (Sodium): 23 NaOH: 40
Si (Silicon): 28 SiO2: 60
Al (Aluminum): 27 Al2O32: 102
O (Oxygen): 16 Water (H2O): 18
Waterglass (Na2SiO3): 122
Step One
Calculating 1 part (1 mol) Aluminum

Locking a parameter: Aluminum

We can easily lock the amount of Al to 1 mol, because we have only one source of Al, the metakaolin. (All the other elements are coming from two sources. Sodium is found both in the waterglass and in NaOH for example.)

1 mol Al2O3 contains 2 mol (or 2 part) Aluminum atoms. But we only need 1 mol Aluminum so we need half mol Al2O3 in our mix to have 1 mol Al. According to our table above, half mol of Al2O3's weight is
102 / 2 = 51 g

How many Metakaolin we need?

We can calculate the whole amount of metakaolin needed by using the percentage ratio of Al2O3 in it. You will find this number in the product data sheet (probably a pdf).

Percentage of Al2O3 in your metakaolin product: %


We have silicon in the metakaolin!

Before we continue: there is another important number in that pdf, that is the percentage of SiO2 in the metakaolin product. This is crucial because it is a constant amount we can only increase but not decrease with the other components. Let's calculate the "hidden" (in plain site) SiO2 content in that  g metakaolin!

Percentage of SiO2 in your metakaolin product: %
This button is disabled until you calculate the amount of metakaolin above.


Scoreboard

It's time to summarize where we are now. What do we have and what do we miss?
"M" Al Si H2O
Target 1 1 2 5.5
Current 0 1 ✔️ 0
Missing 1 5.5
Step Two
Calculating the other three components

Mind the gap!

We need to add some other materials to the mix:
  • Sodium (Na): from waterglass solution or from NaOH
  • Silicon (Si): from waterglass solution or from cat litter (not kidding)
  • Water: from waterglass solution or from the tap
Cat litter is an excellent source of water soluble, amorphous SiO2, it's easy to use, dirt cheap and clean. (If you use it directly from the bag, not from under the cat.)

Sodium silicate

Now we only need one more (and last) paramterer: the weight percentage of Na2SiO3 in your waterglass solution. It is clearly marked on the bottle, a typical number being 36%.

Percentage of Na2SiO3 in your waterglass product:
%
This button is disabled until you calculate the SiO2 content of the metakaolin above.