Abstract: An apparatus for the wet spraying of concrete, comprising a mixer embodying a mixing container incorporating means for closing such in a gastight fashion, a compressed air source connected with the mixing container, said mixing container incorporating a closable concrete outlet opening, a substantially cylindrical concrete containing conduit detachably introduced at one inner end through the concrete outlet opening and in a position substantially in alignment with the inner wall of the mixing container and a number of supplementary air infeed conduits located near the mixer and opening into the concrete containing conduit for the infeed therein of compressed air.