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[Tvoivozhd <tvoivozd AT infionline.net>]

http://www.bmtpc.org/linkages.htm
 (India concrete, gypsum production, use in precast inverted 
roof-channels, L-Pans)

http://www.cbri.org/patents.htm
 (India construction patents)

http://www.motherearthnews.com/arc/5368/
 (Ken Kern article on building a house---for cash---in Mother Earth News

Ken Kern in "The Owner Built Home", described a $1901 house with outside 
composting toilet, whose most interesting feature was the use of 
cement-asbestos sewer tiles cut in half and laid up in interlocking 
lip-up and lip-down configuration.

Nobody, of course is ever again going to use cement asbestos overhead 
anything in a house, but the design principle is unexcelled in a 
low-cost, very strong, easy-to-attach roof.  Make your own 
roof-components by making an earth-mold on the ground---cut out a 
plywood screed so when it is dragged across the earth-mold on two 
parallel wood runners, it will produce in the earth or wet sand, the 
profile of a lip-down channel of whatever length is desirable. The depth 
of the lip determines loadbearing capacity---and if more is needed, you 
can run small-diameter rebar in the floor of the channel---or rather in 
the corners of the precast channel floor.  Another way to screed a 
profile is to place  an accurately spaced 2 X 6 on each side of the 
earth or sand pile, drag the screed along that---the outer surfaces of 
the channel would be more accurate if the concrete mix used the 2 X 6 
surface as a mold.  I think I would do this in preference to trying to 
get accurate cavities in damp sand alone.

At each end of the mold, insert a plain plywood stop. 

So you don't have to make a new mold every time you strip a cured 
channel out of it, I would stabilize the surface with a Bondwall mix as 
follows:  Cement 19.5 lbs
         Lime 3.75 lbs
         Calcium Stearate 0.25 lb.
         Calcium Chloride 0.50 lb
         Glass fiber 1.0 lb  (could use more easily available
         Water1.5 gallons     polypropylene fiber)
         I would then spray or paint the mold surface with a
         silicone or wax release compound

Lay down chickenwire reinforcement on channel and lips, and insert waxed 
wooden pegs through the lips of the channel (accurate spacing) and 
trowel the concrete mix on the mold.  After the mix sets up, withdraw 
the waxed wooden pegs.  I would also use polypropylene fiber in the 
concrete mix---probably overkill, but would discourage formation of tiny 
cracks in flat, horizontal surfaces.



Strip the concrete channel from the mold, and invert it, install with 
lips up on the roof concrete bond-beam, into which is imbedded metal 
tie-downs. The concrete channel lips will be bolted together, including 
one or two bolts through the sheet metal tiedowns. 

Probably a good idea to lay a strip of EPDM between the channel lips 
too---as a better seal against air leaks.  Forgot, you should install a 
cap over the channel lips---and put your through-bolts through the cap 
as well as the lips.

You will now note that your roof resembles a standing-seam metal roof, 
except it is practically bomb-proof and will even outlast an excellent 
standing-seam metal roof.

If you have a different configuration of house than 
rectangular---hexagonal, for instance, you could make triangular 
concrete pans with reinforcing cast purlins produced by indents in the 
mold.  Ok, so it's more work, but I like hexhouses.  Make more molds for 
tip-up hex-panels---match the lip angles and fasten walls the same way 
as the roof.

You probably won't buy or use one, but the Paul Sarnstrom Tirolessa 
Hopper-Sprayer is interesting for small-scale spraying of ferroconcrete 
in conjunction with a Hole-Hawg powered Onebone Mixer.

Some concrete additives for water-resistance, plasticisers to reduce 
water for more strength, and aiding mixing.

http://www.moxie-intl.com/1800-CUT-SHEET.htm


http://www.moxie-intl.com/tutorial.htm
 (concrete tutorial, note you want to get rid of capillaries, make 
concrete vapor-proof, not just water-resistant)

http://www.gemite.com/products-alphabetical.htm
 (Gemite list of additives)

http://www.masterbuilders.com/eng
 (Degussa, formerly Master Builders)

http://www.arcat.com/divs/sec/sec03300.cfm
 (long list of suppliers, inc. Xypex, colorants etc.)
.