Sounds like a carton form slab.

It was suggested as an option on a high plastic index job. We
elected to use lime slurry injection as a less expensive option
that project.

I never got into the details of designing the bearings for that
slab.

Carton forms are usually used to create expansion voids under
grade beams. I know that hay was used for this void in the past,
so your idea has merit. I would guess you simply need a strong
enough slab to span the voids.

Waffle slabs have decks as thin as 2", though I would tend more
toward a thicker slab. Post tension might be considered.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Keep the whole world singing. . . .
DanG


"Wpg Man" wrote in message
om...
Does anybody have any thoughts about using straw bales as a
"void
form" for a concrete garage pad?

Typical garage pads in my area are made on top of a gravel base
that
is deeper around the edge. This gives a one-piece concrete pad
that
is "thickened" around the edge for strength. These pads are
pretty
good, but they are only "thickened" around the edge and can
still
crack.

I want to dispense with the gravel completely, and use hay bales
as a
"void" form as follows:

Place bales in a series of solid 8ft x 8ft squares on the
ground.
Between each set of 8ft squares would be an 8 inch gap. If you
can
imagine, the concrete is poured over the while thing. The
concrete
would go down into the 8" gaps, giving an integral concrete
"beam"
every 8 feet. So instead of a "thickened" edge beam only, this
pad
would have a matrix of beams every 8 feet. Of course there
would be
rebar also.

The hay bales are basically there to "save money" on concrete
(instead
of pouring a 2 foot thick floor). I think this floor would be
so
strong that you could lift one corner and the whole thing would
stay
together (no cracking due to frost etc).

I am wondering about these hay bales though. I really don't
care if
they rot after the concrete sets. Does anybody see any
problems? I
would probably put plastic on top of the bales to seperate them
from
the concrete. Do you think I should also put plastic underneath
them
so they stay dry forever?

I think the cost would be less also. Typically, you need 2 feet
of
gravel under the floor to raise the grade of the garage floor.
With
the bales, I automatically get a 2 foot raise in the grade, as
well as
the extra strength from the beams.

Also, if you really want to go nuts, the beams can be made
deeper (or
the grade can be raised) with very little cost by stacking bales
on
top of each other. If you were to stack 2 bales (instead of
one), the
beams are deeper and it would not take much extra concrete.

I also like the fact that the beams (both in the middle and
around the
edge) are nice and "square". The "thickened edge" garage pad
has a
beam around the edge that is formed by the sloping gravel
beneath it,
giving a "not so pretty" beam.

Thanks.