Could it be that the "minimum reinforcing requirements" don't take into account the provision or allowance (also in ACI) for using 1.33x the amount of steel required by analysis?
An ACI standard really does not have any effect or power until it is either adopted by a code or specifier.
A code can adopt just a portion of a standard, but that usually requires a great deal of research or a local condition is over-riding.
The same applies to ASTM standards, but on a different scale. It could be possible for a code to adopt an ASTM standard with some noted exceptions, but not too many codes would get into the situation and liability of modifying an existing material or testing standard. A code can adopt a specific version of ASTM standards since they are modified annually in most cases.
CM, exactly right. The government adopts the building code and the building code references the standard. If the IRC has a table of plan concrete foundation walls, you have the option to use that prescriptive design, or design something using the referenced standard ACI 318. And pay attention to the version. If you the 2003 IRC is in effect, then ACI 318-02 is the standard.
