We have a massive concrete step that I'm going to replace. The question is
whether or not I can bust it up with a sledge, in place.

The piece is 3'W x 4'L x 8"Thick.

Will whacking on it with a sledge finally break through that 8" thickness
and start shattering pieces off?

The reason I'm asking before trying is because, if I can bust it up, it will
have to stay in place and maintain function and appearance for a short
interval until I can figure out how to rig it out there in one piece.

I'm hoping sledge blows will put fault lines though the mass and start it
breaking up.