Opus caementicium exposed in a characteristic Roman arch. In distinction to modern day concrete buildings, the concrete used in Roman structures was usually covered with brick or stone. The Romans applied concrete extensively from three hundred BC to Advert 476.[18] In the Roman Empire, Roman concrete (or opus caementicium) was https://griffinikiig.buyoutblog.com/35740360/detailed-notes-on-concrete-reinforced-retaining-wall