No question we agree that certain concrete damages copper.
Grant KZ1W
On 7/18/2013 10:39 AM, David Gilbert wrote:
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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