>What if the form were 'short' - just a couple of feet to square off the
>top
>(visible) part and the rest of the concrete was poured against the bare
>undesturbed earth below? Then I'd only be backfilling the top couple of
>feet to neaten it up. Is the chunk so big that it doesn't really
>matter? Seems like a way to make the form smaller and easier to
>handle.
>Tnx es 73! Brian Smithson, N8WRL
Brian,
Having just done this very thing this weekend, I can say that this is a
very easy way to accomplish the task provided that the soil you're digging
into can hold its shape in a vertical wall, or even slightly tapered.
I dug a 2' diameter round hole, then cut in a square just below grade
with a splitting maul and flat shovel to accommodate a square form having
2'x2' inside dimensions, made from 2x8" lumber. This form rises 4
inches above grade to keep standing water away from the tower. After
curing, just knock the simple form away and throw in a little dirt where
the form was near the top.
This way, your tower foundation rests on undisturbed earth.
There have been some previous posts in the archives about pouring concrete
on top of water. I'll try to recap what was said.
It was the general consensus that if you don't have too much water (1
foot or less?), and give it a place to drain away to via a trench at the
top of the hole, that the concrete will simply displace the water and cure
fine. I assume that this would work best if you could lay the concrete
down through the water on the bottom of the hole with a shovel or minimize
the drop from your chute to maintain a thick stream (minimize mixing). It
may not be the ideal situation, but it can and does work.
However, if it falls some distance first, gathering speed and the stream
is thin and broken, as someone pointed out recently, you could get a
dissolving action from turbulent mixing with the water that would separate
the concrete's components.
Good luck,
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