Construction techniques of Roman vaults and opus caementicium: The cases of Lupo and St. Gregory’s bridges

In this paper the revolution induced by the use of the opus caementicium on the Roman construction techniques of buildings and vaults, especially during the imperial age, is outlined. Although this new technique reminds that adopted in the proto-Mediterranean period, the revival proposed by the Romans is quite different thanks to the use of pozzolana mortar and intelligent structural solutions to guarantee a mechanical behaviour mainly in compression. Three bridges are analyzed where the opus caementicium is used: in the first two cases for restoration works, and in the last as a consolidate technique for building new arch bridges.