TIL that ancient Roman concrete is more durable than modern concrete and can heal its own cracks. It has lasted for millennia due to its unique composition, including volcanic ash, which prevents cracks from spreading. Recent studies have found that the material actually grows stronger over time.

Yes and no.

It has a significantly lower compressive strength than modern concrete (like 20-25% of modern iirc) and would fail in most modern construction.

However, the use of volcanic ash makes it much more resistant to chemical erosion, and the 'self healing' is due to hot mixing. It creates microscopic calcium silicate hydrate crystals that, when exposed to water(like rain), effectively become more concrete filling in cracks and "healing" the concrete. Hence why a lot of the structures using it still stand