[TowerTalk] Conductivity of cement
xdavid at cis-broadband.com
Sat Sep 6 22:31:38 EDT 2008
That is extremely illogical. Just because you have part of a Ufer
ground doesn't mean you have a satisfactory Ufer ground. There are
specs for surface area that I'd bet aren't satisfied by a small pad
around a wellhead.
Besides, I would bet that every one of those exploding pads occurred
because the rebar was NOT connected to the wellhead casing. I suggest
you head to the Polyphaser web site for a more authoritative
recommendation ... check out their tech note on Ufer grounds for a tower
Besides #2 ... since concrete is moderately conductive on its own, what
do you think happens to a concrete pad that gets hit by lightning and
doesn't have the rebar to help distribute the current? The concrete is
not an effective insulator for a lightning strike, and rebar certainly
doesn't increase the odds of a lightning strike (not when you have a
couple dozen feet of steel well casing buried in the ground right next
to it), so tell me ... does Ohms Law say you are better off with the
rebar helping to bleed off the current, or is it better to force the
current to blast a path through the bulk concrete?
Besides #3 ... most building codes REQUIRE that a tower be grounded to
the rebar cage in the foundation. My inspector specifically checked to
make sure I had done so.
Larry E Sheriff wrote:
> Hi, as putting ground rods and tying to the rebar; has any of you seen what
> happens to concrete when high heat hits it???
> I live out in the country and alot of us have a well with concrete slabs
> around it. Lighting has hit a few. The concrete explodes into many peices.
> Which would just leave the guy wires to manage the tower.
> I will NEVER ground anything in my base!!!
> Just my 2 cents worth.
> 73, Larry - W4LES
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