Jon Elson writes:

... the idea
hit me to try the air chisel! I had a short pointed tool that came
with it. It went through the concrete almost like butter. You just
keep the point moving, and it shatters a little cement at a time.

You have reinvented the star drill.

So, I ran the thing practically full blast for about 5 hours one night
and 3 or so the next. I didn't find it particularly horrible to the
bones and joints.

20 minutes with an air chisel, and my hands are suffering vibration
sickness. Half-paralyzed and tingly, like running a string trimmer for too
long. Anti-vibe gloves help, but it still is too fatiguing for long
sessions. This sort of thing can injure you seriously.