Advice please re dodgy garage floor

[knight]

Moved into a new (to us anyway) house last november, the gargae floor was a right old mess of peeling paint and what looked like a type of mold in certain places on bare concrete. Move forward to this year and I've recently pressure washed the floor to remove as much of the old paint as I can but have noticed the mold has come back.

Now my plan is to hire a concrete sander and give it a damn good sanding to take off the top layer of concrete and then to put a floor sealer down.

My question therefore is, has anyone ever experienced mold on concrete and if so how did you cure it, or could it be something else?

[pikeyboy]

Does the floor have a damp proof membrane under the concrete?

[knight]

I do not know, there is a damp proof course in the walls though.