Worried about Tripping
You can see here that the slab has dropped down below the crub causing the apartment complex to worry about people tipping
Raised Slab
After the PolyLevel was injected you can see that the slab is now level with the curb.
Bandaid
This is not a correct fix for a concrete slab.
Fixing Bad Work
You can see here how far the slab had sunk once the concrete bandaid was removed.
Even Slabs
This is how to correctly fix the sinking, uneven slab.
Large number of Slabs
You can see here just how extensive the sinking was. This is a picture of only one side of the complex.