(urth) Concrete

[Sonofwitz at butcherbaker.org]

Howdy listers, lurkers, and layabouts,

As I've mentioned previously, I'm working on some illustrations related to New Sun...
I have another question for you scientifically "hard" minded readers.

Concrete.  Is there some reason that I've not yet thought of that would prevent concrete casting from being a viable technology on Urth in Ymar's or Severian's time  It strikes me that concrete casting is a method that humanity would not lose, and I can't think of any reason why it wouldn't be used on Urth.  

This came to mind when reading the Innovation comic, where the Oubliette is pictured with medieval stone masonry.  The thought of a spaceport built on walls of rounded stone just seems wrong to me.  No, the citadel would have tons and tons of concrete along with it's unsmeltable metal.

Am I wrong?


~Son of Witz