I beleive your right! Ive only ever used one ground rod for all my electric fences without issues

The last couple places I built in the states required two ground rods. I too have used the rebar in a foundation. Just clamp a #4 copper wire to the rebar and bring it out above the surface of the concrete.

Also built a hangar in which the electrical engineer required three ground rods al connected together.........in the hangar floor.

Ground rods are copper coated steel. Or Galvanized steel. Never seen one that wasn't. Solid copper rod wound be VERY expensive and would not drive well due to the head mushrooming over. Steel rods mushroom bad enough in rocky ground.

Yes copper is the best there is. It's a good thing it's abundant.

Specific 'K' of copper is around 10.9.
Steel is around 100.
Aluminum is around 17

K= resistance in 1 mil of wire 1' long.
Mil=.001 inch

Best conductor out there is silver with a K of about 9.7
Gold comes in at 14.7. Far less than copper.

All Greek to me but I have heard that silver is the best before.

I worked with the power company for 5yrs an I only ever seen one solid copper ground rod. The Forman said that was the second one he had seen. He had been there 30 some yrs. I have no idea how old it was but it was 8’ long an it was star shaped instead of round

Residential services in our area require 2 ground rods, one 6 feet out from the other.
We are told the reasons are that it ensures getting at least one rod out from under the drip line of the roof (potential dry spot), and during droughts or dry spells, more contact with the soil makes a better ground - and two are twice as much as one - and would very rarely not be adequate.

Never seen a copper rod or one star shaped. I can tell you the theory behind it though. For the same size, a star shaped rod would have more surface area to present to the soil hence making it a better conductor.

Talking about the earth as a conductor:
During the Civil War, Lincoln and the War Department could keep up the major battles real time. So, when the Army won or lost a minor or major battle or skirmish Lincoln in Washington knew about it in minutes. Say Picketts Charge, Lincoln knew about it's failure immediately. There was a telegraph group (kind of like our modern day signal corp) that went right along with the Army. When the Army advanced, they advanced. Stringing wire (1) along the way. They strung it on convenient trees if they could, if not they dug in short telegraph poles.
It takes two conductors to complete a circuit. One conductor was the wire on the pole on insulators and the other conductor was the earth. Telegraph of the 1800s and Civil War times was a simple make-break of a circuit so that is all that was needed. One wire on the pole and the Earth.
It was not a safe job either, Behind the line raiders were told to seek out the telegraph group and destroy them if the could. So, just because you were setting on your butt in a little wagon listening to morse didn't mean you were safe.

So, yes, if you can get a rod down to where there where there is moisture the Earth is a very good ground.
Electric fences work on the same principal, one conductor on insulators and the Earth as the other.

Here the idea of 2 grounding rods is one at the pole and the other at the house so the one at the pole is supposed to help if the power line is struck by lightning, and the one at the house protects it with the safety ground in the outlets connected to that, as far as fencers go the idea is about dry conditions, sheep are the worst with a small hoof and wool, when we had sheep we ran a ground wire from the fencer just below the hot wire and grounded at every corner post and still has trouble with them, with the cows it worked great because they learned fast to not touch the fence.

I have never seen an all copper rod. But I have found a copper clad rod.

Did you ground the metal skin of the building to the re-bar or ground the electrical panel to the re-bar?

Both. The three rods in the floor were tied to the panel but the building was grounded to the foundation rebar by way of the bolts in the skin. #4 copper from the bolts down to rebar in concrete. Over ten thousand bolts in that building so we had lots to choose from

silver is better than copper which is better than aluminum which is better than steel. that said - old farmer taught me to ground to a fence t-post. Said if that ground wasnt good and wet - that one tied to the wire fence a half mile way stood a pretty good chance of being better and if it wasnt good - the few hundred posts in between stood a fair chance of getting a decent ground. I learned something from him in that many times we overlook a simple solution for some fancy grounding rod..........

Thanks!