An obnoxious contractor working for a neighbor left a ball of cement
almost 3 feet in diameter in the woods next to my house.
They were separate blobs, not yet totally set, but they're all stuck
together now, with a few small empty spaces where the blobs meet,
partially.
I'm going to borrow or rent an electric jack hammer to break it up into
pieces light enough for me to remove.
I've already tried a sledge hammer and a couple tiny chips came off but
the thing didn't crack.

I would drill holes in the concrete, then use feathers and wedges to crack it
into pieces. But I already have the rotary hammer, feathers, and wedges.

Alternatively, you could drill holes in the blob and pour in some "Dexpan".
It slowly expands, splitting the boulder or blob into pieces.

Another option, dig a large hole and use levers to push the blob in the hole.
Then cover it with dirt.

Good luck,

Anthony Watson
www.watsondiy.com
www.mountainsoftware.com