Ufer Ground Electodes

[doug11046]

Two questions:
1. Is there any evidence that lighning strikes can cause damage to concrete piles configured as Ufer ground electodes?
2. Is ther any evidence that stray ground currents can cause the rebar in Ufer ground electrodes to act as sacrificial anodes?

 

[bphgravity]

Re: Ufer Ground Electodes

1. Yes, but only under very specific conditions both in electrode connection and lightning strike. A high intensity strike is capable of passing through concrete itself with or without the conductive rebar in place. This current super heats the moisture within the cement causing it to turn to steam which rapidly expands possibly cracking or blowing apart the concrete.

2. I don't know. I am under the impression that oxygen or exposure to the air must take place for corrosion in metals to begin. Can current alone do this? I would be interested in reading a study on this.

 

[5Spot]

Re: Ufer Ground Electodes

Originally posted by bphgravity:
I would be interested in reading a study on this.

You'll find an excellent discussion from the the man himself, H.G. Ufer, in Appendix B of Electrical Grounding and Bonding based on the 2005 NEC by J. Phillip Simmons published by Thomson, Delmar Learning.

 

[iwire]

Re: Ufer Ground Electodes

Originally posted by bphgravity:
A high intensity strike is capable of passing through concrete itself with or without the conductive rebar in place. This current super heats the moisture within the cement causing it to turn to steam which rapidly expands possibly cracking or blowing apart the concrete.

I have seen the after effects of that, one of our customers building was struck by lighting and a large section of the cement parapet was blown apart. It was lucky no one was around as chunks of concrete came raining down from about the 6 th floor level.