The explanation in the article is fascinating, but I wonder how much the Romans knew about the durability of their concrete at the time, and to what extent they just got lucky by the mix of material that happened to be available in their area.
I feel like a single human could trial and error their way to a very good paper airplane over the course of 2 or 3 days. It seems pretty obvious that a large group of people would trial and error products in much the same way, especially those so essential to their civilization. Especially with the large trade networks that we know to exist back then.
