What did the Romans mix to get the cement-like material they used in all underwater projects?

Considered the first true cement-like material used by any civilization, the volcanic sand would chemically react to lime and water, causing it to harden. It could be used in large-scale underwater projects like the string of aqueducts it constructed all across the empire. These structures are still standing today. Leave it to the Romans.

Asked by Jennifer Sinclair · Last updated 5 years ago · 6.6K views · SOURCE