Abstract: The invention relates to a method for working up unused concrete mix and/or mortar whereby the unused concrete mix and/or mortar is gradually supplied to and distributed over a sieve during spraying of the unused concrete mix and/or mortar with water in such a way, that grit or the like which is in the unused concrete mix and/or mortar is cleaned by rinsing and remains on the sieve in order to be discharged therefrom. The material passing through the sieve and consisting of a mixture of sand, cement and water, is supplied to a separation device wherein the sand is separated from said mixture. The remaining mixture of water and cement is returned at least partly from the discharge of said separation device towards the supply side of the separation device.