Unit for Manufacturing and Preparation on the Worksite of a Mortar for Spraying

A unit for manufacturing a mineral matrix 1 produced from a powder and water comprising a mixing module 20, connected to a primary water circuit and to a powder collector 30, comprising a mixer 22 and a pump 24 wherein the powder and the water are mixed to form said matrix, characterized in that said unit further comprises a control unit (UC) being arranged to control the quantity of water coming from the primary water circuit and the amount of powder taken from the powder collector. Colouring means 10 may be provided, being connected to the primary water circuit and being arranged to supply coloured water having a defined colour and controlled by said control unit. The colouring means may include an array of storage tanks for primary colorants 12, a plurality of compartments 120, first and second containers 140, 160 mounted on scales B1, B2. A secondary water circuit 50 may modify the viscosity of the matrix. A cleaning unit (60, figure 4) may be connected to the secondary water circuit to clean said unit. A method of operating the unit is provided. Plasters are mortars specifically formulated to be sprayed on a wall or facade element.