[TowerTalk] Tower grounding
Grant Saviers
grants2 at pacbell.net
Thu Jul 18 14:01:28 EDT 2013
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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