The Canal du Midi was built using concrete in 1670, and there are concrete structures in Finland that date from the 16th century.^[citation ^needed]
I can find similar rumors all over the internet, but no reliable sources. Does anybody know more about this?
Fyi from a concrete mix background, the Romans were using concrete a long time before this. Modern concrete.just means using Portland cement in the concrete there are other types of concrete that existed earlier (and later).
For example Asphalt (or Bitumen) is concrete using bitumen binder instead of cement binder. This it's probably a simple disconnect between common usage if the word concrete and the technical definition
German archaeologist Heinrich Schliemann found concrete floors, which were made of lime and pebbles, in the royal palace of Tiryns, Greece, which dates roughly to 1400-1200 BC.
Concrete is old. You should probably read that article in full.