Try a wire brush and lacquer thinner first and if that does not work you will need a power washer to remove it.

Power Washer, no matter how high the pressure, will remove paint absorbed and embedded in concrete.

You need to sand blast.

Goof Off works best on concrete than Lacq thinner #5,just thought you might like to know for future ref.

P.Washer would work too but I wouldnt go rent 1 for this,unless you have alot of it to clean up.