We Finally Know How Ancient Roman Concrete Was So Durable [View all]

The ancient Romans were masters of building and engineering, perhaps most famously represented by the aqueducts. And those still functional marvels rely on a unique construction material: pozzolanic concrete, a spectacularly durable concrete that gave Roman structures their incredible strength.

Even today, one of their structures – the Pantheon, still intact and nearly 2,000 years old – holds the record for the world's largest dome of unreinforced concrete.

https://www.sciencealert.com/we-finally-know-how-ancient-roman-concrete-was-so-durable

Fascinating article on what they mixed and how they mixed it to produce unreinforced concrete that has stayed intact in things like sea walls, something we can't do even with reinforcing the concrete with rebar.