Difference between manual shotcreting and mechanical shotcreting

Difference between manual shotcreting and mechanical shotcreting

Dry-mix shotcreting：First, mix the concrete (sand, cement, including powder accelerator) on site，then the premixed material will be put into dry-mix shotcrete machine. Compressed air from rubber hose blows the material to spraying hose where there is a water tube. Concrete material and water will be mixed here and then be blew out to the spray surface.

Advantages: dry-mix shotcrete machine is small and compact.

Disadvantages: spraying effect can’t be guaranteed(water volume is controlled by spray worker). high rebound rate, large waste, low working efficiency, poor working environmen.

Wet-mix shotcreting: The concrete is prepared in the mixing station in advance, and then is transported to the construction site by the concrete tank truck and loaded into the wet shotcrete machine. The liquid accelerator then will be added into the premixed concrete.

Disadvantages of wet-mix shotcreting: high cost of wet shotcrete machine and liquid accelerator, high request to the spraying worker, it is suitable for large-scale spraying projects.

Disadvantages of manual shotcreting:
1. High labor intensity and low efficiency, 3 cubic meters per hour;

2. Poor working environment makes workers prone to silicosis;

3. The shotcrete structure is loose and the later strength is low (the compressive strength of C25 concrete is about 10MPa in 28 days), which is easy to collapse and drop pieces;

4. Large resilience, much labor and high injection cost;

5, the number of operating surface, easy to group death group injury malignant safety accident.