There’s a wide variety of fill material that can go in earthbags – road base, subsoil, gravel, crusher fines, etc. Use what’s low cost and locally available. But also consider durability and climate. Do you live in a very cold climate? Then consider using insulating materials in the bags. Do you live where flooding is common? Then raise the site as much as practical and use water resistant, stabilized fill materials such as lime stabilized subsoil.
This blog post introduces yet another possibility: pumice-lime or scoria-lime in the earthbags. This material is similar to pumice-crete, except cement is substituted with hydraulic lime. The basic process involves mixing some lime with one of these lightweight aggregates to improve wall strength and stability (loose fill materials tend to shift) but yet retain a fairly good level of insulation.
From Building with Pumice, by Klaus Grasser and Gernot Minke:
Building blocks can be made of natural pumice and lime. Indeed, such blocks used to be quite common. However, careful consideration must be given to the characteristics of the lime. In the first place, use only hydraulic -or better -eminently hydraulic lime. Dolomitic or magnesium lime, i.e. lime with a somewhat grey color, is preferable to fat lime, i.e. chalk-colored lime, for making good pumice. Lime blocks, thanks mainly to the fact that the grey types, as the name implies, contain more magnesium, which reacts with the silica fraction to give the finished product superior strength properties. On the other hand, whatever lime is used should contain as little salt as possible, particularly in the form of sulfuric acid, because salt causes efflorescence and detracts
from the blocks’ mechanical strength.
To obtain pumice-lime blocks with strength values exceeding 20 kg/cm²:
– the exact chemical composition of the lime and all pumice materials under consideration should be ascertained by way of careful chemical analysis, and
– sample blocks and compression strength test specimens should be prepared.
http://www.nzic.org.nz/ChemProcesses/production/1G.pdf the recipe
This article provides some useful back info, but I would buy sodium silicate already made.
I found a recipe for pumice geopolymer http://www.mendeley.com/research/investigating-the-possibility-of-utilizing-pumicetype-natural-pozzonal-in-production-of-geopolymer-cement/ which uses pumice, Lye (sodium hydroxide NaOH), and Sodium Silicate (Na2SiO3) The sodium silicate is the problem here in that to make it, there is a process where it gets heated in a furnace. So although mostly this recipe is low temp, all of it is not. The pumice geopolymer however shows matching strength of portland cement after 28 days. Here is one recipe I found to make the sodium silicate….. maybe someone could come up with a better/easier recipe for it?
I’ll check this when I have more time. This is the general concept I was leading up to in this blog post about Lightweight, Insulating Geopolymer Earthbags Part 1.
http://earthbagbuilding.wordpress.com/2011/05/29/lightweight-insulating-geopolymer-earthbags-part-1/ It looks they have already developed a specific recipe for pumice. This is exciting news. New discoveries every day. What we REALLY need is a good book written for builders.
Here where I live, I have only seen Lime Type S in a solid bag so I dont know what color or texture it is without buying it and taking my chances. It is about $10.00 US dollars for a 50lb bag
Yes, Type-S is the correct type of lime.