In alt.home.repair, on Fri, 14 Oct 2016 09:23:54 -0700 (PDT), TimR
wrote:

Go back to the sledge hammer. It will work, just be persistent.

Or give it to a couple college kids with a case of cheap beer.

Do not stand on a ladder with a jackhammer, that's asking for trouble.

You're the only one to directly address that. I think you're right.

If you insist on using power tools, dig a hole insead. A 3 foot deep 3 foot wide hole is no big deal. If need be use the college kids and case of beer.

That's a good idea, although whenever I've dug a hole of any size, it's
full of big rocks and hard to dig.

I'll look into getting a couple kids to work for me.

Roll the concrete (NOT cement) into the hole.

Stand next to it with your jack hammer ready to pound it.

then realize you're an idiot - you already solved the problem. Throw a little dirt on top and walk away, return the hammer.