The cage must withstand the forces of concrete flowing around it during
the pour. It must also be prevented from moving during the pour.
Flowing concrete pushes real hard!
I built my cage of re-bar that is approved for welding, with E7018 rod,
and I welded it accordingly. It wasn't so heavy that I couldn't put it
onto and off my truck, but I used the loader on my tractor to place it
into the hole with little effort.
Both the cage and the tower legs (Universal Tower, steel legs extend to
near the bottom of the base) rest on concrete pads to that they do not
penetrate the concrete at the bottom, to delay corrosion. I wired the
legs in place inside the cage and I blocked the cage and tower legs with
2 X 4 members wedged against the sides of the hole to prevent movement
while pouring the initial foot or more of concrete. Once that much
concrete was in the hole, I pulled out the 2 X 4 members with ropes I
had tied to them for that purpose and finished the pour.
The first section of tower was mounted to the legs, plumbed, and secured
with guys, to hold the legs straight, aligned with the tower, and
vertical. As the pour progressed, I checked that the assembly did not
move out of plumb. I adjusted the guys once to correct a slight movement.
There are two reason for welding the cage: one is to prevent any uff
dahs while pouring the concrete, the other is to assure conductivity for
a Ufer ground. The cage lies 6" from the sides of the concrete and
three members extend above the concrete for CadWeld connections to
copper cable going to each tower leg (with approved clamps between
copper and aluminum) and to create lightning ground radials with
multiple ground rods. All clamped connection, clamps to legs and cables
to clamps, are treated with anti-oxidant appropriate to the materials
joined and those joints are periodically examined, cleaned, and re-treated.
This didn't take much more effort than wiring the cage together and
didn't increase the material cost very much. When the concrete arrived,
I was confident that all would go well, and it did.
73 de WOØW
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