On Wed, 17 Oct 2018 13:42:11 -0400, John H.
wrote:

A friend told me about this stuff:

https://www.youtube.com/watch?v=1uaIVIUVOyM

Will try it.

I am not sure how that will work out with the water in the hole. It
will just float on top where the concrete sinks and displaces the
water. It does look like an interesting idea in a dry hole tho. It
also gives you an idea of the required compressive strength necessary
to hold a pole,. If styrofoam will do it, I can't imagine any concrete
mix that wouldn't even if it started with the consistency of tomato
soup.
I am also not sure why a can of spray foam would not do the same
thing.