Need definitions for circa 1956 concrete class C & D designations

I am preparing documents for the renovation of a building constructed circa 1957.  The original Contract Documents call for structural concrete by classes (i.e. Class D for walls and beams & Class C for slabs).  I have reviewed the 1956 ACI Code as well as other period documentation but could not find descriptions for the classifications.  Can anyone shed any light on this issue?

It could be a regional naming scheme used by either the local city or DOT.  Try asking a DOT Highway or Bridge engineer - they could possibly refer back to an old DOT Spec.

ROCKY,

JAE is right on with the DOT aspect, although "naming scheme" is interesting phraseology.  

In the case of PENN DOT, Class C is 3,000 p.s.i. and Class A is 3,500 p.s.i.

Class AA is 4,000 p.s.i. and Class AAA is 4,500 p.s.i., also PENN DOT spec's.

BRIAN

I got that word "scheme" from listening to Al Gore too many times  :)

And where, pray tell, did Al Gore get it?  (In Florida!)

JAE/JHEIDT,

I cannot imagine living a life of consistent fibbing.  I don't think I would ever get the story straight.

It's so much easier to attempt to be honest, which simply entails telling the truth.

The only thing harder for me to comprehend, is how the American people are still duped into believing all of the statments these suits make, as if they were actually going to follow through with them.

In a way, I suppose in a big way, I should be greatful for the average American's disposition actually.  For when the people stop beleiving in these suits, what will become of this great nation?

Although it would seem, the time is ripe for such change, but only if the alternative is rife with hope and civility.

BRIAN
[The Concrete Philosopher]