
How Did the Romans Make Concrete That Lasts Longer Than Modern Concrete? - o_nate
http://www.openculture.com/2017/07/how-did-the-romans-make-concrete-that-lasts-longer-than-modern-concrete-the-mystery-finally-solved.html
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jmcguckin
Are we talking about concrete structures in general, or specifically marine
concrete structures? This topic (or variants thereof) have been floating
around the net for months. They're mostly bullshit. All modern-day PCC
(portland cement concrete) structures continue to harden ('cure') for an
indefinite period after pouring. A 30 year old building is stronger than a 3
month old building.

There's nothing magic or secret about this phenomenon. Adding fly ash (very
similar to volcanic ash) to PCC is a well known ingredient for making high
strength concrete.

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pcmaffey
Portland cement is also incredibly brittle (and thus short-lasting) compared
to the natural lime-based concrete used pre 19th century.

Here's a great explanation of the differences: [http://limes.us/about-saint-
astier-nhl/what-is-natural-hydra...](http://limes.us/about-saint-astier-
nhl/what-is-natural-hydraulic-lime/)

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DrScump
Related:

[http://99percentinvisible.org/article/cracking-case-
secret-i...](http://99percentinvisible.org/article/cracking-case-secret-
ingredient-explains-durability-roman-concrete/)

