Opus caementicium exposed inside of a characteristic Roman arch. In distinction to contemporary concrete buildings, the concrete used in Roman buildings was generally coated with brick or stone. The Romans employed concrete extensively from 300 BC to Advertisement 476.[18] During the Roman Empire, Roman concrete (or opus caementicium) was made https://infopagex.com/story5147445/5-tips-about-concrete-reinforced-wall-you-can-use-today