Method and a device for adding material in an air stream to a nozzle

Apparatus for manufacturing fiber reinforced concrete by mixing a stream of airborn concrete material with a stream of airborn reinforcing fibers, said apparatus comprising a nozzle assembly including:

• a first pipe for carrying one of said streams;
• a convergent mixing chamber leading from and having a junction with said first pipe;
• a nozzle means leading from a discharge end of said mixing chamber;
• a second pipe leading into said first pipe for carrying the other of said streams, said second pipe including a socket portion extending substantially axially through said first pipe, said socket portion terminating in a discharge end disposed substantially at the junction between said first pipe and said mixing chamber, and further including a curved portion located upstream of said socket portion, the curved portion having larger and smaller radii such that material of greater mass in said other stream is flung by centrifugal force substantially along said larger radius while material of lesser mass in said other stream is directed substantially along said smaller radius;
• a discharge conduit leading from said smaller radius of said curved portion of said second pipe;
• and
• valve means disposed in said discharge conduit for controlling outflow of material of lesser mass in said other stream from said second pipe through said discharge conduit.