It seems to me that you would need to indicate the appropriate agency involved in order to get your answer. Different agencies can have their own concrete class designations and their own specifications.
I am doing a FEM analysis on bridge approach slab and would like to have resonable properties for the concrete slabs normally classed as "A" and "AA".
Again, who is the specifying agency????? PennDOT's Class A or AA may not be the same as some other agency's Class A or AA. I am not aware of a universal designation for concrete classes.