My basement floor years ago had a tiled floor. Tiles were adhered with what looked like a black tar type adhesive. Tiles came loose and were removed. Even though the floor is smooth I am unable to get all the substance off the floor. Can this stuff be painted over or do I have to retire the floor. Prefer to paint if possible.
Rent a concrete floor grinder from a local tool rental. It should get rid of the majority of the adhesive and any other surface coatings. Then, you should be able to go through the normal process of proper concrete painting (make sure to read up on proper surface preparation for your selected product to ensure best adhesion and results).