"John Wakefield" wrote in message
...
What's the best thing to use for this? Sledgehammer or some sort of power
tool?



From experience, the easiest way is to put pressure underneath with pickaxe,
then give it some welly with a sledgehammer to break paving slab sized lumps
off. It really depends on what you have available, and how thick the
concrete is. Thinner concrete is easy, just leaver and wack, thicker stuff
may require something like an SDS to weaken it; very thick stuff may require
a small thermonuclear device, but remember to use ear defenders first.