We Finally Know How Ancient Roman Concrete Was So Durable

[Warpy]

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.

[ItsjustMe]

1. Mystery of why Roman buildings have survived so long has been unraveled, scientists say

https://www.democraticunderground.com/100217539003

[GreenWave]

2. Next "mystery". Is glass a liquid?

If you say no, wait a few hundred years.

Next mystery why does broken old glass mixed with a new batch of molten glass make it even stronger? Hades if I know but it does!

Oh your first mystery was blood. Air pockets allow for expansion and contraction.

[Wounded Bear]

3. Rebar corrodes away and leaves voids in the concrete...

Good stuff! Thanks for the link!

[Warpy]

7. Concrete develops microscopic cracks

which are self healing in the Roman stuff. Water gets in to the rebar. Rust takes up more room than iron does, so the rusty rebar exerts force on the concrete and creates big cracks, and eventually the whole business fails and the bridge or the building drops like a rock.

I wonder how soon we're going to see lime clasts in structural concrete.

[Wounded Bear]

8. Sounds like they're working on it...nt

[303squadron]

4. Paging the State of Florida, pick up the condo collapse phone

[SCantiGOP]

5. Hard to believe this process was lost

or that it took so long to figure out.

[krispos42]

9. It's my understanding that the secret ingredient was seen as an impurity to be removed...

...and not as a component of self-healing concrete. Something along of the lines of "this lime is so contaminated with impurities! We can do much better now!"

[IbogaProject]

6. I know rebar allows for huge concret structures

Rebar doesn't just corrode as iron rusts all the way through, I think the only element to do that. Copper piping gets pinprick holes after awhile, but that may be another process. Another interesting option maybe synthetic egg whites. The ancient Mexican Olmec concrete has lasted so long as they added ostridge egg white to theirs.