zlacker

>>hrl+(OP)
Tangentially related. The romans figured out that volcanic ash and salty sea water made cement that actually gets stronger with age instead of breaking-down after 50 years: https://www.sciencemag.org/news/2017/07/why-modern-mortar-cr...

>>Concer+Zc
I'm not sure, but this probably fits the facts better: the Romans figured out how to make cement with volcanic ash and salty sea water, and it turns out that it gets stronger with age.

It's not clear to me that the Romans knew that, or that it informed their choice of that building material. I suspect it's more that they built with what they had, and got lucky that it turns out to be incredibly durable stuff.

>>samatm+9h
The Roman scholar Pliny the Elder described underwater concrete structures that become "a single stone mass, impregnable to the waves and every day stronger."

https://www.nature.com/news/seawater-is-the-secret-to-long-l...

Sounds like they knew.