There are two main types of shotcrete: wet-mix and dry-mix. Wet-mix shotcrete is a mixture of cement, sand, and water that is mixed together before it is sprayed onto a surface. The mixture is typically transported to the site in a truck and pumped through a hose to the nozzle.
Dry-mix shotcrete, on the other hand, is a mixture of dry cement and sand that is transported to the site in bags. Water is added to the mixture at the nozzle, where it is combined with compressed air to create the spray.
Both wet-mix and dry-mix shotcrete have their advantages and disadvantages. Wet-mix shotcrete is typically more efficient and produces a smoother surface, but it requires more equipment and can be more expensive. Dry-mix shotcrete is typically less expensive and easier to transport, but it can be more difficult to apply and may produce a rougher surface.