Google mud jacking.
I dont even know what mud jacking is, but I suspect it is using the hydraulic pressure of concrete while it is wet to lift the slab under pressure. Heres what wrong with that. If the original floor lost support from settlement, what makes you think that the unstable substrate will not settle further under considerably more load. In a nutshell, you cant shine s**t. Many of the roads built by the Romans are still in service. Now why do you suppose that is?