method of spraying a dry concrete, lance projection and corresponding dampening ring

The invention concerns a method and a nozzle for dry process spraying of refractory concrete. Said method is characterised in that it consists in mixing water with a dry product comprising in particular added ultrafine particles, a dispersing agent and a set accelerator, before spraying. The mixture is formed with a volume percentage of water less than 25 %. The nozzle (1) comprises a hose (3) transporting pressurised water and pneumatic hoses (2, 5) transporting the dry product and the moistened product, and a water box (4), comprising a wetting ring (12). The latter comprises four to eight orifices circulating (21-24) water, substantially perpendicular to the axis of flow (10) of the product and having each a diameter ranging between 0.8 and 1.2 mm. The nozzle further comprises means for pressurising water by at least 8 bars. Thus, the wetting ring (12) ensures the moistening of the product with water at said high pressure.