Thanks for the interesting ping. It never ceased to amaze me what the Romans could do with sand/gravel, burnt limestone/gypsum, water, and a lot of laborers.
Any links/leads on the more nuts & bolts (or is that nails & pegs?) of the actual form building? My job used to entail building them; it was up to the mudders to fill them, so you can see where my interest is.
I'm a little curious about that myself.
The art of underwater concrete casting was perfected by the Romans, but their concrete was quite different from the concretes used today. I've seen the process reproduced (on a video of course) and with the addition of water the mixture started to "boil". The Pantheon in Rome, which in its time (and for some time thereafter) was the largest dome in the world, and is still standing, was constructed (if memory serves) of concrete.
http://www.ancientroute.com/cities/caesarea.htm
http://ancientneareast.tripod.com/Caesarea_Maritima.html
http://www.padfield.com/1996/caesmari.html
a translation online, by one Bill Thayer (I couldn't get it to load):
http://www.ukans.edu/history/index/europe/ancient_rome/E/Roman/Texts/Vitruvius/home.html
same work, different URL, now it's bedtime for 'Civ:
http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Vitruvius/home.html
http://www.vitruvius.be/index.htm
Oh, I like this guy already:
"Another orphan text that no one wanted to enter, but that many nevertheless will be glad to see online. (Why is it that the self-aggrandizements of Cicero, the lecheries and whining of Ovid and the blatherings of that debauched old goose Seneca made it onto the Net before the works that give us solid technical information about what Rome was really good at, viz. the construction of her great buildings and works of engineering?)" -- Bill Thayer
http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Vitruvius/home.html