[GoLightly]

My point had to do with a reduced need for the quantities of kilned lime you had assumed, at which point we're not talking soft cast chalk, but a form of concrete.

[GSlob]

Amounts are still beyond the reach of technology and resources. The only things they had in abundance was stone, sand, and man-hours. But their secret is much simpler, and is nether technological nor logistical, but organizational: THEY DID NOT HAVE CONSTRUCTION TRADE UNIONS.