Abstract: A process and apparatus for the preparation of mortar from an aggregate and a binder is disclosed which comprises the use of a silo provided with at least one partition so as to create in the silo two or more compartments for the separate storage of the aggregate and the binder, the compartments being provided with conveyor screws, the speeds of which can be adjusted to control the volumetric flow of the components to a mixing chamber. When the desired amounts have been dispensed, the remaining materials may be stored indefinitely for layer use. The silo compartment for the aggregate may be provided with a heating element to safeguard the mechanically operated slide valve against freezing. The conveyor screw in the outlet for the binder may be provided with a cam and a plunger rod with transverse projections to prevent arching in the compartment for the storage of the binder.