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Re: [TowerTalk] Tower grounding

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Tower grounding
From: David Gilbert <xdavid@cis-broadband.com>
Date: Thu, 18 Jul 2013 10:39:03 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>

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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