How to cut through old concrete slab

[diyreg]

4 inch concrete slab. I've got to cut a channel in it for foundations for a new garage. I've got a powerful angle grinder with a diamond bit - goes through walls easily, but it does little to this concrete.

I'd like a fairly neat break, so put off a Kango. I could hire an industrial strength concrete cutter. What would you guys do?

 

[RonnyRaygun]

If you've got a 9" disc cutter it won't cut through 4" anyway...although would probably be close enough that a good clobber with a sledge hammer would break the rest of it.

If I were you I'd hire a 12" water cooled petrol disc cutter.

 

[Deluks]

I've done similar using a combo of 9" grinder plus stitch drilling with a 4kg SDS and then sledge. But I already had the tools so no investment required. Once you get a hole going it's relatively easy.

 

[RedHerring2]

I've done similar with combination of 9" grinder plus kango hammer. It'll only be the bottom of the cut that will be a bit ragged, so no problem. But once completed and old concrete removed you can clean up the edge if required.