Shotcrete---failures & troubleshoot of problems too large rebound of material

There may be some failures in the use of the shotcrete machine for dry material, one of which is that the material rebounds too much. What method should we take to deal with such a failure when using a shotcrete machine? Let's take a look at what we should do when such a failure occurs:

Reason 1 and troubleshooting method:

Reason: Inappropriate sieving curve

Troubleshooting method: Check the material gradation and adjust it if necessary

Reason 2 and troubleshooting method:

Reason: The spray distance from the nozzle to the sprayed surface is too close

Troubleshooting method: increase the spray distance to about 0.8m

Reason 3 and troubleshooting method:

Reason: The spray distance from the nozzle to the sprayed surface is too far

Troubleshooting method: reduce the spray distance to about 1m

Reason 4 and troubleshooting method:

Reason: The spraying direction is not perpendicular to the spray surface (90°)

Troubleshooting method: Correct the spray angle