On 5/4/2017 3:10 PM, Wes Stewart wrote:
> IMHO, the rebar in steel-reinforced-concrete is there to constrain the
> concrete under tension. It's not there to anchor the tower. Generally
> speaking, welding isn't a good idea either, unless rebar graded for
> weld-ability is used (Grade "W"). The stuff you buy at Home Depot is
> probably Chinese made and of questionable quality.
I used big-box store re-bar stock for the cages when I put up my tower 35 years
ago, but the quality was probably better then. I tack-welded the cages
together, just enough to hold the pieces in place while I set the cage in the
hole. I have heard it said that you should never weld re-bar, but I can't see
what harm a small tack-weld could possibly do. I can understand it not being
advisable to solidly weld the pieces together so that the entire pieces at the
joints get red hot. In any case, the tower has been up for 35 years and the
concrete anchors and piers haven't fallen apart yet.
I suspended my cages in place using ungalvanised steel bailing wire attached to
scrap pieces of water pipe laid across the top of the hole, with enough
clearance between the pipes to allow the concrete to be poured without knocking
the cage out of alignment. I didn't trust resting the cage on concrete bricks
or piers, not sure if the concrete could be guaranteed to completely cover and
seal the re-bar away from the soil. Once the concrete was poured I used a pair
of wire cutters and reached down a couple of inches into the wet concrete and
clipped the wires, then smoothed over the top of the concrete anchor where I
had inserted the cutters. Once the concrete is poured, the re-bar isn't going
anywhere; in fact it would be difficult to forcefully move it. It certainly
won't sink to the bottom.
I didn't use concrete forms; just dug the holes to size and filled them with
concrete, except for one where a heavy rain had collapsed the sides of the
hole. I had to dip out the mud and build a form for the anchor, because my
hole had turned into a shallow crater filled with mud with the consistency of
chocolate pudding.
When the holes were all filled, the guy in the concrete truck asked me where I
wanted him to dump the left over concrete. I thought they would take it back
where they had some place to mix it with water and dump it, but no, it was all
mine and he said they had to empty the truck before going back to town.
Instead of having them dump it at the edge of the field somewhere where it
would turn into an immovable boulder, I told the guy to use what was left to
top off the two holes that hadn't collapsed in the flood. The piers were
supposed to be buried about two feet below grade, but the ones they topped off
came up to about 4" from the surface of the ground. I decided that wouldn't
hurt anything, if anything make the piers stronger, and since it would still be
covered with dirt, better to have it part of the anchosr than out in the field
somewhere to be in the way for all eternity.
Don k4kyv
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