Hi Allan,

Its a compound or dry powder called Bentonite. You can purchase it in bags from most electrical suppliers or even specilist earthing contractors.

I have used it on TT earthing systems where we have had to drill bore holes due to ground conditions/geology and fill they hole with Bentonite, try and pack it then drive in the earth rod.

Basically it is moisture-retaining clay that is commonly used as a backfill for earth rods installed in drilled holes, or as a layer encapsulating horizontal earth conductors buried in a trench.

Its main advantage as far as earthing is concerned is that it has the ability to retain moisture in the immediate vicinity of an earth rod, and hold it there for a considerable period of time. This reduces contact resistance and increases the effective size of earth electrodes.

Hope that helps, but its easy to purchase and not uncommon.

Cheers GTB

Thanks

Also look at marconite.

  - Andy.

The other family of things like the marconite are intended as cement additives that allow you to turn steel cast in concrete such as rebar, or in my odd case, anchor hooks for antenna mast guy lines, into things that are very well earthed. Unlike the cat litter in the mud, it does not slowly leach away over any sensible time period.

electrical Bentonite is chemically similar to some brands of self-clumping cat litter and the latter is more easily available, and  at a push ...

Both benefit from siting near the rain water soakaway if there is one.

Mike.

In the past I believe that coke has been used (the solid fuel, not the soft drink) I think that coke was favoured if the earth connection was expected to carry significant current in normal operation, rather than just leakage currents and the odd fault current.

Earth connections for single wire earth return power circuits, earth connection for cathodic protection systems. I think that some of the HVDC interconnectors use coke beds in the earthing system. Under normal conditions, two cables are used, one for positive and the other for negative. If one cable is faulty, operation at half power is possible by use of the sound cable and an earth return.

Ignoring the fact that this is not in English, this video shows the installation of a charcoal and salt enhanced rod, in a dry place.

The pictures make the technique clear enough.

https://www.youtube.com/watch?v=LcFNHPkTuQ0

I note with some amusement the 'bulb in series ' test for a nice low electrode resistance about 7 mins in . Not to be repeated in any country with a health and safety policy.... Still, at least he is not bare-foot.

Mike

Furse® Earthing & Lightning Protection catalogue - see page 80

It is expensive, I used it on a project with some tape buried in a deep trench. Managed to get it down to 143ohm

Many years ago, I did some work in an a semiconductor factory where they used to go round the earth rods every Monday morning and pour salt water over them.

regards burn