How to remove concrete slab
Sledgehammer will work, but it is way too hard work. Use hammer drill instead.

These drills usually have three or four modes of operation:


Drill Like normal drill, usually with higher torque
Hammer drill. Drill with additional hammering for drilling through concrete, stone etc.
Fixed hammer. The head is locked in rotation and the tool is just ramming.
Free hammer. same as 3 but the head rotates freely.


Option 3. is for you. Works like sledgehammer but it is much faster and much easier to do the job. You can lend it at some DIY stores for a good money.