[TowerTalk] Cadweld vs other welds or brazing

[Patrick Greenlee]

If you get really uptight about your connections consider this... The 
proscription against welding the rebar is a rebar strength issue.  Just 
extend the rebar a bit past its "standard planned length" and weld to 
the extension which is not involved in the design of the cage.  I have 
welded stainless steel tabs to steel with ease.  Then I could use SS 
bolts to secure copper ground strap and not get the corrosion I would 
expect with plain steel.  The forgoing  will work but as Jim L says, it 
may not make much of an improvement.
When in doubt I typically opt for the more is better approach.

Patrick NJ5G

On 5/3/2014 8:44 AM, Jim Lux wrote:
> On 5/2/14, 6:04 PM, N3AE wrote:
>> I've been following this thread with interest.
>>
>> What's the proper way to bond galvanized steel anchor rods to the
>> rebar cage to get a good Ufer ground? The UST specs specifically
>> state not to weld the rebar (because they call out ASTM A-615 rebar,
>> not the weldable A-706).
>
> tie it.
>
> A variety of testing has shown that the metal conductors in a concrete 
> encased grounding electrode do not have to be continuous.  There was 
> one paper where they tested versions of Ufer grounds where the 
> segments of rebar that were welded, segments that were tied, and 
> segments that were just laid together.  They all worked acceptably.
>
> I'm sure there are pathological cases: if you had a bunch of 6" long 
> pieces of rebar randomly placed in a big block of concrete) that 
> technically meet the 20 feet of conductor guideline; but, I would 
> think that pretty much any "conventional" assembly technique would work.
>
> It's mostly about providing a suitable large area contact with the 
> surrounding soil, and after that, making the current density in the 
> metal and at the metal to concrete interface low enough.
>
>>
>> My plan is to use bronze rebar ground clamps rated for direct burial
>> for both the wire-tied rebar cage and the anchor rod connections,
>> with #4 AWG solid copper wire between them and a bit of stainless
>> shim stock between the clamps and the galvanized anchor rods (for the
>> dissimilar metals problem - galvanized with copper-bronze clamps).
>> All the above encapsulated in the concrete pour.
>>
>> Make sense? Are the SS shims overkill or even undesirable (compromise
>> the tightness of the connection to the anchor rods)?
>>
>> Shawn - N3AE
>>
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