BROKK BROKK BROKK BROKK!!! <-- there is your solution!!

try to find someone with a BROKK demolition robot to do it for you, a 90 size will do fine! 40 or 50 has quite short reach so it can slow down thing a little.
2 brokk 90 with experienced operators will easily do the jobb in time!
use wide chiesels and turn down the hammer power, then it doesnt break the concrete structure.

a other solution would be to mount a surface cutter on a BROKK 330 or 180, that would probabbly be 2-3 times faster than the hammer solution.

doing it by hand can be quite a task! you need a army of guys with handheld hammers to do it in time!

I have used the Terminator machine before on ceramic tile with a mud bed. It should work if the sandy mud bed is brittle and bonds well to itself. If it is really sandy and doesnt bond well to itself it may be tough to do with the machine becuase it will just rip stips in the mud bed. I would suggest giving the machine a shot and if it doesnt work get a fleet of chipping hammers.