[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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