[mjevans]

Using even less material seems likely to lead to most buildings trying to do only that and failing to include any other mechanism for acoustic isolation and privacy.

I am almost equally worried about other previously assumed goals that traditional construction methods happen to fulfill but which could be overlooked due to under-specification. What things? I don't know, and my worry is that experts in those fields might not either until that data is gleaned the hard way.

[jcims]

Great points. Any major change in 'concrete' is likely to yield a few surprises when folks try to drop it in as a replacement for the standard.