Opus caementicium exposed inside of a characteristic Roman arch. In distinction to modern-day concrete constructions, the concrete used in Roman structures was usually coated with brick or stone. The Romans made use of concrete extensively from three hundred BC to AD 476.[eighteen] Throughout the Roman Empire, Roman concrete (or opus https://zionlgask.humor-blog.com/34594718/concrete-reinforced-with-rebar-can-be-fun-for-anyone