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

Hopefully of passing interest

Very good. I have seen other speculations on this but it should be noted that even standard concrete heats a bit on mixing with water. It used to be a standard experiment for O level/ GCSE Chemistry to heat limestone to form quicklime, CaO which is allowed to cool but adding a little water the reaction is so exothermic the water will boil.

And hence why it's pretty nasty stuff...

Quote from: Imperial Dave on February 13, 2025, 09:49:40 AMAnd hence why it's pretty nasty stuff...

It is easy to forget that we are basically bags of water on a framework!

 

Quote from: Ian61 on February 13, 2025, 08:56:31 AMIt used to be a standard experiment for O level/ GCSE Chemistry to heat limestone to form quicklime, CaO which is allowed to cool but adding a little water the reaction is so exothermic the water will boil.

Lime mortar, commonly used in heritage restorations, needs special care in site safety terms for this reason.  Imagine mixing buckets of boiling sludge  Quicklime was also used as a blinding agent in Medieval naval and siege warfare.  Ah, those days of chivalry.

Modern concrete structures won't last nearly as long - maybe 100 years.

Reminds me of a documentary on what would happen if all humans suddenly disappeared from the Earth. Upshot is that after 1000 years nothing would remain of our modern structures. But the Pantheon and the pyramids would still be there.

Quote from: Justin Swanton on February 13, 2025, 11:17:26 AMModern concrete structures won't last nearly as long - maybe 100 years.

If you're lucky and they are not made of RAAC.

Less than 40 years in the case of reinforced autoclaved aerated concrete... 

Quote from: Justin Swanton on February 13, 2025, 11:17:26 AMModern concrete structures won't last nearly as long - maybe 100 years.

Reminds me of a documentary on what would happen if all humans suddenly disappeared from the Earth. Upshot is that after 1000 years nothing would remain of our modern structures. But the Pantheon and the pyramids would still be there.

And my lead pile.....

I think that deep down we know our modern civilisation is a very temporary affair and act accordingly, not building for the long term (I've lived my whole life in Africa where the watchword is You Can't Stop Regress).

The earth has only got about another billion years anyway so I wouldn't worry about it 

Quote from: Imperial Dave on February 13, 2025, 11:41:49 AMThe earth has only got about another billion years anyway so I wouldn't worry about it 

Mmmmh...about 500 million before the water is boiled off by the sun.

Even less time to worry about it then