The method of application for spraying machine is not far from the wet-sprayed, the only difference they have is the type of mixture being fed to the machine.
For spraying machine, the dry mixture is being placed in a shotcrete and are pressurized through the hose, exiting to the nozzle. Once the dry mixture hit the surface, it will be then applied with water content, enough for it to bond with the surface.
For concrete, it can arrive on-site which is the ready mix concrete or for smaller construction site which can be mixed on-site with ratio depending on the compressive strength of the concrete.
The spraying machine should remain moist for at least a week after it is applied into the surface. The need for it to be moisten is to have a better compressive strength as it cures which results to a better quality of the application.
When the spraying machine is not watered consistently during the curing period, the strength will deteriorate which will result to lesser structural integrity of the surface. After it has cured, it is important to seal the surface because concrete can be porous.
The pores will be prone with water penetration which will lead to leak of structural integrity deterioration.