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Old Posted May 13, 2019, 2:12 PM
Baronvonellis Baronvonellis is offline
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Location: Chicago
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Originally Posted by ardecila View Post
Fly ash from coal power plants has many of the same chemical properties as the volcanic ash the Romans used, and it's used in quite a few concrete pours these days.

But there are always trade-offs; in our cold climate, concrete actually needs air pockets inside to absorb the expansion of ice crystals from moisture in cold weather. It's a bad thing for it to be too dense. Pozzolanic concrete mixes (like Roman concrete or concrete with fly ash) are denser than traditional Portland cement mixes, and they could have bad spalling problems if exposed to freeze/thaw cycles. That's obviously not a problem in Italy...
Freezing wasn't a problem in Southern Italy, but the Roman empire extended into northern Europe where it freezes and thaws.

Also, the eastern half of the Roman Empire continued uninterrupted till 1453, so it wasn't like the knowledge would have been lost when Rome was sacked in 476. The empire continued in the east the same as it had been with the same knowledge until the Renaissance, and had frequent trade and contact with Venice for example.
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