It's very likely your barn has some sort of "rubble" foundation. Is it possible to leave a piece of the slab in place, around the perimeter, to reinforce the top of the footing? You'd likely need a concrete sawing company to saw around the perimeter, lots of jackhammering in any case. An opinion from a local experienced builder could be very valuable. Like Derek says, you need to weigh your options, costs & benefits to choose your best option.
Good luck
Scott