There is no fixed standard for the "shotcrete speed" of a shotcrete machine. Thickness control mainly relies on the comprehensive adjustment of shotcrete process parameters (air pressure, water pressure, nozzle movement method, layer thickness, etc.)
Key Control Parameters:
Single Shotcrete Thickness: For PZ-type shotcrete machines, the thickness of a single shotcrete application should be controlled at 50-70mm. Re-spraying is necessary, with an interval of no more than 2 hours between applications.
Air Pressure:Not less than 0.4MPa; it is recommended to control it between 0.45-0.70MPa during actual spraying.
Water Pressure:Approximately 0.1MPa higher than air pressure.
Water-Cement Ratio:Approximately 0.4; the amount of water added depends on the operator's experience.
Nozzle Angle:As perpendicular to the sprayed surface as possible, with an angle of not less than 70°.
Rebound Rate:Controlled to no more than 10%.
Other Factors Affecting Thickness/Speed:
Accelerator Dosage (2.5%-4% of cement content):A good accelerator dosage results in faster curing and less flow.
Aggregate gradation (continuous gradation preferred, aggregate ≤10mm).
Is the base layer properly cleaned (no loose soil, loose rock)?
Spraying operator movement: It is recommended to move slowly and evenly in a spiral motion to ensure a smooth surface.
In actual operation, it is recommended to use "no dry spots, no dripping, strong adhesion, and minimal rebound" as the on-site judgment standard. Specific parameters need to be adjusted according to the engineering design and equipment conditions.
