Are these guys behind or what? Roman cement has been known for decades to be superior to all other forms of cement in that time period and for centuries after. It took hundreds, if not thousands, of years for the EU civilizations to duplicate the Roman type of cement. It was the only cement of its time and, as I said, for centuries after, to be able to dry while under water, it was in most ways similar to modern cement. They may have been murderous jerks but the Romans were great engineers.
But probably no more so than others.