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re: hay/straw bales as concrete forms?
11 may 2000
wrote:
>i just saw a post wherein one fellow suggested using bales of hay/straw
>as concrete forms... if you were building an aboveground structure,
>how thick would the outside walls of bales around the building have
>to be, in order to support the weight of the concrete that goes into
>the walls and the roof of the structure?
an 8' wall full of 150 pound per cubic foot wet concrete exerts
1200 pounds per square foot of force at the bottom, right? so each
square foot of wall needs about 1200 pounds of strawbales near the
bottom, if the coefficient of friction between the strawbales and the
ground is 1 (the wall might still bulge a bit.) that's about 40 30
pound bales for each linear foot of perimeter, at the bottom of the
wall, extending more than 100' outwards from the wall, on both sides!
it seems more interesting to put the bales inside the wall and use
plywood slip forms with wire ties. that's a more economical use of
concrete and it makes better use of its strength. the smaller amount
might be mixed up and placed by the bagful. the bales can provide
excellent insulation, if there's not much concrete bridging the wall
from one face to the other. the strawbales or haybales (why not,
in this case?) would stay inside...
nick
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