Posted: 01/08/2012 at 17:06
Breaking up concrete with a pickaxe is very hard work. I have done it. If you can try to make a groove along the line where you want to leave the concrete in situ. Hammer and stone chisel would do it, but an angle grinder is better. Then try to get a crow bar under the edge of the bit you wish to break up and then hit the concrete with a sledge hammer. It breaks easier that way. And the groove, cut should stop it going past where you wish to retain it.
Otherwise you are into hiring a pneumatic drill. Donr that too.
Best of luck with it.