ferro-cement cisterns

Elfpermacl at aol.com Elfpermacl at aol.com
Mon Sep 28 11:35:56 EDT 1998


In a message dated 9/28/98 10:08:42 AM, hanzibra at svn.com.br wrote:

<<As to rainwater catchment:

	Here in the Brazilian drylands the most practical ( economically and in
terms of setting up) form of cistern so far has been cement forms which
the farmer prepares on the ground and then joins up- there are literally
thousands  which have been made this way, and have proven to be
satisfactory.  Now these cisterns are being built with  "cabbage-cement"
as they have been substituting the  chickenwire with those red nylon
bags that oranges and cabbages come in (at least here)... which can be
had free-of-charge.
	Recently a local ( in Irece) mason  developed an even easier and more
foolprooof version which I have not seen, but , as it has been explained
to me, is the following:
	He builds up  the cistern first with small adobes, uses these to give
form and  support to the cistern, putting a layer of sand on the outside
of the adobe to hold the cement.  He then weaves wire around the adobe ,
and up and down as one makes a basket ( chickenwire is prohibitive here,
and using just wire makes it much cheaper).  This is covered with the
layer of cement( I believe it is the usual mixture of 2 of sand to  1 of
cement) and left to dry.  When it is firm, the adobes are removed and
another layer of cement is passed on the inside of the cistern.  The
final cost was approximately 150 dollars for 10,000 liters  including
labor , and took one day to build.  This mason has successfully built
3,000- liter cisterns with this method.  This is the first time he built
one of 10,000 liters, which is still under observation.  After 2 months
it is holding well, with no leakage, one of the major problems when the
cisterns are built with separate forms.

Marsha Hanzi
Instituto de Permacultura da Bahia
Brazil
>>

Excellent addition, Marsha, to the discussion.  Can I use your post in my
report to the folks in Paraguay with whom I'm working?  (Maybe we can get your
mason to do some workshops in Paraguay if we can somehow brige the
Spanish/Portugese/Guraní gaps.)

Are you familiar with fibro-cement, using bamboo instead of chicken wire?  You
have some of the best structural bamboo in the world native to Brazil, though
I suppose you haven't much in the dry country.  In Mexico, I see tall species
of cactus dried and split into laths to support the tile roofing.  It might be
worth experimenting to weave narrow strips, properly cured, into fibrocement
baskets to be covered with mortar.

In all of the materials I have read on ferrocement, it is stressed that it is
important to apply both sides of mortar at the same time.  How long have these
one-side-at-a-time cisterns been holding water?  There is a fairly simple
arrangement whereby the wire is held away from the form and the cement pushed
through so it indeed covered both sides at one time, though one would have to
be careful in the pushing to be sure of a complete coverage against the form. 

the form is then removed, as with the adobe wall.  Generally it is regarded
best to apply all layers at one time so that there are no seams.  Am I
learning from you that this is not so important as the books say?"

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