[TowerTalk] Tower grounding

[David Gilbert]

Actually, the problems with copper tubes in concrete aren't at all as 
well documented as you might imagine.  Google "copper tube concrete" if 
you don't believe me.   The research a few decades ago that concluded 
corrosion in concrete *due to the cement itself* was the primary issue 
was poorly done, and more recent studies indicate that 
expansion/contraction differences ... or mechanical stress due to bends 
in the tubing ... may alo have a significant influence. Other studies of 
actual failures point to chlorine or sulphur attack from soil chemicals 
that penetrated the porous concrete.  Most codes require sheathing of 
embedded copper tubes for protection, but it isn't exactly clear what 
the protection mechanism is ... mechanical or chemical.  In at least one 
set of cases the failure analysis conculsion was that the plastic 
sheathing CAUSED the failure by trapping contaminated water around the 
tubing.

Here's an interesting link which, while no doubt self serving, points 
out that concrete heavy in sulphur from cinders or fly ash can indeed be 
corrosive to copper.  Fly ash is often used to improve the workability 
of concrete, and also it's resistance to freeze/thaw damage.

http://www.copper.org/applications/plumbing/techcorner/problem_embedding_copper_concrete.html

This thread really hasn't been about copper wires inside concrete tower 
foundations, though.  If it were, all of us should be worried about how 
we connected our towers to the Ufer ground in the first place ... all of 
which I bet used copper wire.  Instead we have been talking about 
whether there is a problem with copper wire exiting the concrete 
directly into the soil.  That's a different issue entirely.

So no, unless you can describe a mechanism where such an exit 
exaggerates any other deleterious effect on the copper or the 
foundation, I don't think the logic holds at all.

Dave   AB7E




On 7/18/2013 8:16 AM, Grant Saviers wrote:
> Agree that the Ufer wiki entry re "chip and flake" is soft. However, 
> the potential problems with buried copper or copper in concrete are 
> well documented/known issues, so I think the logic holds.  I think the 
> codes tend to "get it right" over time and experience, and they 
> support the conclusion.
>
>
> Grant  KZ1W