Is this possible? I seem to remeber being told that it was possible to rent a concrete scraper, that basically grinds down high spots on uneven concrete slabs. aappreciate that if such a thing does exist , its likely to be v.heavy and make an unholy racket!
It uses diamond tipped cutters and is very expensive and difficult to handle.
Machine Mart sell diamond tipped cups that fit onto a normal angle grinder that may solve the problem.