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ferro-cement

Re: the question on replacement materials for concrete in ferro-cement, and
despite the original author's open admission to having purposely committed a
pun...

	Concrete is mostly harmless (isn't that what they said about earth?) but
can contain significant amounts of aluminum, and smaller amounts of other
metals, including radioactives commonly found in rock materials [radioactives
are one reason Zeolite, a mined mineral with very high cation exchange capacity
-- important in agriculture -- and moisture-absorption coefficeint is not
allowed by the Texas Department of Agriculture in organically-certified soil
mixes]. 

	Probably to a great extent danger from the mineral impurities of concrete
is mitigated by its alkaline reaction in water. It tends to render metals
insoluble in water, and for this reason might actually be a great material for
storing water. However, I personally would only hesitantly recommend building a
ferro-cement tank without sealing the inner surface. Not only would a sealer
obviate any real danger from mineral impurities, but, importantly in thin-shell
constructions, it would protect the crucial steel inside the concrete from the
corrosive effects of moisture. Sealers come in all sorts of bizarre chemical
configurations, which, if concrete worries you, you don't even want to think
about! Perhaps plain parrafin or bee's wax, heated and applied on a hot day,
would work well, and might actually be harmless to humans (who brought up this
harmless-to-humans thing? -- man, that's going to cause all kinds of extra
trouble!).

	Speaking of steel being crucial for tensile strength in water tanks (or
most concrete construction), the same would be true of other earthen materials.
They are very poor in tensile strength (resistance to being pulled apart as
opposed to squashed) and would need to be supported from outside to counter the
forces of the water inside pushing out. Again the problem of sealing the
material to protect the steel enters in. Old water tanks used wood, tightly
bound from the outside, and sealed by its own expansion upon wetting. Adobe has
manure in it, no? Hmm... Bentonite clay could be used as an earthen sealer of
sorts, not perfect at preventing moisture travel and probably presenting the
same mineral-impurities danger as the original concrete (and similarly
expensive).

	I'd go with the phenomenal long-term permanance of well-constructed
ferro-cement, keep about an inch of concrete on the inside of the steel
(construction "re-mesh" is strong, cheap, and the leftover makes the very best
tomato cages, 5' tall, a nice rust color, they blend right in with the garden),
and seal the whole inside with bee's wax or what passes in the mind for other
harmless sealers (the FDA says plastic cement -- you know, the black stuff inept
roofers use for patching roofs (rooves?)  -- is safe for drinking water... Mmmm,
that sounds good...).

	A book on ferro-cement, only one I know of that's not written for
boat-builders (I know, sounds strange, but it's true) can ordered from Jade
Mountain Alternative Products or some such name, at
http://www.indra.com/~jade-mtn/contents.html. The title is Build Your Own
Ferro-Cement Water Tank, and the author is Dannie or Donnie Schulzberg or
Schultzburg, in case you want to look it up locally. Jade Mountain has a lot of
good, very hard-to-find books and products for alternative living.

	Long-winded and full of utterly useless speculation? Sorry,  Jack.