There are three ways of looking at concrete objects and their intertwining with abstract objects.
Concrete objects act just like abstract objects.
They can be the subject of properties, new classes of concrete objects can be defined, etc., etc. This view has untenable computational problems, both theoretical and practical. On the theoretical side, reasoning become undecidable. On the practial side, mechanisms have to be provided to give concrete objects properties, etc., etc. Concrete objects cannot participate in abstract properties at all.