There actually IS a contemporaneous source on how to do it, without exact proportions, unfortunately. They didn't know why it worked, of course. https://en.wik

There actually IS a contemporaneous source on how to do it, without exact proportions, unfortunately. They didn't know why it worked, of course. https://en.wikipedia.org/wiki/Vitruvius https://en.wikipedia.org/wiki/Vitruvius https://news.mit.edu/2023/roman-concrete-durability-lime-casts-0106 https://news.mit.edu/2023/roman-concrete-durability-lime-cas... "pozzolanic material such as volcanic ash from the area of Pozzuoli, on the Bay of Naples." They shipped this all over the Empire. Now we have a better idea why it got better in seawater, instead of deteriorating.