Wet mix shotcrete involves pumping of a previously prepared concrete, typically ready-mixed concrete, to the nozzle. Compressed air is introduced at the nozzle to impel the mixture onto the receiving surface. The wet-process procedure generally produces less rebound, waste (when material falls to the floor), and dust compared to the dry-mix process. The greatest advantage of the wet mix process is all the ingredients are mixed with the water and additives required, and also larger volumes can be placed in less time than the dry process.
Wet shotcrete machines are available which control complete process and made it very fast and easy. Manual and mechanical methods are used for the wet spraying process, but wet sprayed concrete is traditionally applied by machine. The high spray outputs and large cross-sections require the work to be mechanized. Concrete spraying systems with duplex pumps are mainly used for working with wet mixes. Unlike conventional concrete pumps, these systems have to meet the additional requirement of delivering a concrete flow that is as constant as possible, and therefore continuous, to guarantee homogeneous spray application.
Wet shotcrete equipment is very useful in underground mining (hard rock). Development of decline pathway to go underground is very critical for movement of heavy machinery, men and material. Shot crating has made these path safe from any ground fall.