A concrete is a thing, a physical object, (at least) a solid, liquid or gas. We will call these concrete particulars. Abstract particulars are processes (verbs), qualities (adjectives) and relations (adverbs, pronouns, determiners, prepositions and conjunctions) of concrete particulars.
Abstract universals are judgments or prototypes from abstract particulars. Concrete universals are judgments from abstract universals.
The chain is: concrete particular; abstract particular; abstract universal; concrete universal.