Date: 2017-07-15 06:49 pm (UTC)
jamoche: Prisoner's pennyfarthing bicycle: I am NaN (Default)
From: [personal profile] jamoche
"as lost as the Roman art of making concrete"

Soo.... about 2000 years later someone will work out what the key ingredient was? http://www.pbs.org/wgbh/nova/next/ancient/mystery-of-ultrastrong-roman-concrete-solved/

Date: 2017-07-16 06:54 pm (UTC)
From: [personal profile] nojay
The "secret" of Roman concrete is survivor bias and time. The really good concrete has survived 2000 years and that's the material we're fixated on but all the not-so-good concrete is one with the snows of yesteryear, as the Canadians say.

The other factor is time -- as concrete cures it typically gets stronger given a number of environmental factors. Reinforced concrete may not survive if the steel support rusts and swells internally but undisturbed concrete is a work in progress over decades or even centuries.

There are some excellent "modern" examples of really good concrete such as the Nazi submarine pens in France and other military structures which are pretty much invulnerable to demolition today -- breaking the material up using diggers and such doesn't work and enough high explosives to do the job would level the nearby cities.

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