Spraying UHPFRC for reinforcement and regeneration of pre-existing structures

A method for reinforcing a structure comprising:

• preparing fiber-reinforced concrete comprising a cement precursor mix, water, a fluidizing agent and metal fibers, the fiber-reinforced concrete having a metal fiber content of at least 2% by volume of concrete;
• transporting the fiber-reinforced concrete by pumping to a spray nozzle;
• spraying the fiber-reinforced concrete onto a surface of the structure by the addition of a compressed air stream in the spray nozzle wherein the spray nozzle is mounted on an end of an intake pipe and comprises a triple-input intake for mixing of the fiber-reinforced concrete originating from the intake pipe with a single or dual compressed air stream, wherein pumping is carried out with a pump with twinned pistons;
• a flow rate of the mixture from the pump is between 2 and 10 m3 per hour;
• and
• the spraying is performed wet by the addition of the compressed air stream with a compressed air flow rate at the spray nozzle of between 10,000 and 17,000 l/min and with an air pressure of between 5 and 11 bar.