[TowerTalk] Conductive Concrete and Grounding

[Jim Brown]

On Wed, 26 Jan 2005 15:48:51 -0500, Tom Rauch wrote:

>Anyone know what the resistivity per unit volume concrete
>is?

In doing research for my white paper on power and grounding, I 
learned that you can buy different types of concrete designed for 
either very high or very low resistivities, depending on your 
application. There are, for example, mixes for use as ties on 
electric transit systems that have extremely high resistivity, and 
mixes designed for use in Ufers that have very low resistivity. And 
there's everything in between. 

When I posed a question on the RFI list re: concrete and grounding, 
Dale, WA9ENA, who is an EMC engineer at Rockwell-Collins, responded 
with his research/study from sources (including AT&T) that concrete 
that becomes part of the path of a lightning hit CAN, indeed, 
explode. 

I think the bottom line is that any concrete that could become part 
of the path of a hit be engineered so that it is a relatively high 
resistance part of that path, and that any Ufers (intentional, low-Z 
ground elements) NOT be part of a structural system.

Jim Brown  K9YC