our rotary lifts have cracks in the floor around the base. you should have at least 3000 psi concrete I would cut out a 4 foot by 4 foot section pore it 6 inches thick and "key" it into the existing slab. you can drill into the existing slab and epoxy rebar in. thats what i would do. I am a civil engineer that would rather build cars
cinch anchor the bolts in at least 4inches or you can buy the epoxy test tubes that have aggagrate in them and insert them in the drilled holes but they run around 30.00 each. crank the bolt torque down to 145-50 foot pounds. you will be good to go. git er done
you can rent the saw and do it yourself. hard part would be getting the small order of concrete you may have to mix yourself but around here you can buy it in small orders.