Query in use of grounding conductor

[Haris]

Hello every body
We r running bare aluminium tape in the concrete parallel to rebar of the column for grounding purpose from top to bottom of the building. Is there any chance of galvanic action between aluminium and rebar? If so than is this advisable to conceal the aluminium tape in the PVC pipe or any other way? :sunny:

 

[Engineer54]

There maybe some while the concrete is green but little after concrete is cured. the most important aspect here is that there must ALWAYS be a minimum of 25mm coverage surrounding the conductor. Better still is to double or more that minimum coverage. Reactions between dissimilar metals require air and or moisture to activate.

Also, if you are bringing the tape conductor out of the concrete at any point ALWAYS insulate at least 10cm before and after it leaves the concrete, or you will have servere corrosion problems, this goes for copper/s/steel/aluminium earthing conductors

 

[benji]

biggest problem iv,e had is protecting tapes from other trades (ground workers & bricklayers ) covering them up pushing them out of there way, they don,t seem to respect other trades

 

[Haris]

There maybe some while the concrete is green but little after concrete is cured. the most important aspect here is that there must ALWAYS be a minimum of 25mm coverage surrounding the conductor. Better still is to double or more that minimum coverage. Reactions between dissimilar metals require air and or moisture to activate.

Also, if you are bringing the tape conductor out of the concrete at any point ALWAYS insulate at least 10cm before and after it leaves the concrete, or you will have servere corrosion problems, this goes for copper/s/steel/aluminium earthing conductors

Thanks for your reply. If you please tell me what you mean exactly by coverage. Is it a coverage of concrete or any sort of PVC pipe.?

 

[benji]

are you going to bond the tape to the bottom of the column

 

[Engineer54]

Thanks for your reply. If you please tell me what you mean exactly by coverage. Is it a coverage of concrete or any sort of PVC pipe.?

Concrete coverage Haris, and it's very important too. Don't run this tape in pipe /ducting unless you want to isolate this earthing tape for some reason!! If you bond the tape to the re-bar, you will be creating a ufer grounding system that will give you the entire footprint of the the foundation slab as part of your grounding/earthing system.... Recommended!!

 

[Haris]

are you going to bond the tape to the bottom of the column

At the bottom aluminium tape is connected through bimetallic connector to copper tape which is exothermically welded with rebar of the pile.

 

[Haris]

are you going to bond the tape to the bottom of the column

At the bottom aluminium tape is connected through bimetallic connector to copper tape which is exothermically welded with rebar of the pile.
Please refer any code such as BS or IEE if possible.

 

[Engineer54]

At the bottom aluminium tape is connected through bimetallic connector to copper tape which is exothermically welded with rebar of the pile.
Please refer any code such as BS or IEE if possible.

First class!! lol!!! A Ufer system you have then...lol!!

 

[Haris]

Engineer54 thanks for your response. You mean that in doing so there is no chance of galvanic action b/w these 2 metals and we can go ahead.
Shall be thankful if u please refer any standard such as BS or IEE.

 

[Engineer54]

Engineer54 thanks for your response. You mean that in doing so there is no chance of galvanic action b/w these 2 metals and we can go ahead.
Shall be thankful if u please refer any standard such as BS or IEE.

I'm at home all the stuff i have, is at the office, and i don't have much at the moment either. I'm having to refer to the on site supervision contractors ref data myself, till after the New Yer...

For galvanic action to take place you need a medium either moisture or air or both.
So you might have a bit of reaction when and while the pour is wet/green, but not after the concrete has cured. That's the reason for the minimal concrete coverage. Too less and water can penetrate any porosity or hairline cracks causing corrosion to re-bar and or your tape. The more coverage you have the less likelihood that will ever happen!!

All the foundations on our project here, are being used as additional Ufer grounding. We are using 240mm hard drawn cooper cable that runs around the site, thru the foundations in conjunction with the re-bar, of every building in a ring format, ...connecting to two ground fields at each end of our project. So long as connections at foundation re-bar are suitable and solid and conductor is protected as it enters and leaves foundation slabs with a good PVC/XLPE heat shrink sleeving (as mentioned to you in post #2) i foresee no problems whatsoever with galvanic reactions or long term stability of these installations...