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
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