The wet mix method involves batching and mixing the aggregates, cement, additives in a batch plant similar to normal concrete. The concrete is delivered to the shotcreting site in a mixer truck and then pumped through a host to a nozzle. Compressed air is added at the nozzle to spray the shotcrete on the rock surface. The wet mix method is used almost exclusively in Scandinavian countries and Italy. These countries have also led the move away from manual application to robotic applications of shotcrete. Concrete is delivered to the site in a mixer truck and loaded into the pump hopper. In the past, progressive cavity type pumps were used but piston type pumps are now more frequently employed. At the nozzle, compressed air is added at the rate of 7-15 m3/min and at a pressure of about 7 bar. The air accelerates the concrete so that it is compacted onto the rock face. Too little air will result in poor compressive strength, and excessive rebound. Set accelerators can also be added at the nozzle. With experienced operators, 60-100 m3/hour can be shot in an 8 hour shift. Advantages and Disadvantages of Wet Mix Advantages of Wet-Mix Method | Disadvantages of Wet-Mix Method | Less dust generation | More expensive equipment | Moisture of aggregates is not as much of a concern compared to dry mix | Increased demands on aggregate quality | More amenable to robotic placement equipment. | Limited pumping distance | More accurate mixing, water addition, and admixture addition | | 4-5 times the application rate of dry-mix | | | Less rebound (in the order of 5-10%) | |
 Introduction
Wet Mix Process Shotcrete Reinforcement: Mesh vs. Fibre Use of Shotcrete Admixtures and Additives Shotcrete Rock Support Design Shotcrete Equipment | 
