Precautions for Wet Shotcrete Sprayers

Precautions for Wet Shotcrete Sprayers

1.During the wet shotcrete spraying operation, be careful to prevent long, large metal objects such as bolts and nuts from entering the material chamber, as this could damage the machine.

2.The rotational direction of each drive motor was uniformly adjusted during installation of the electronic control system. When observing the rotational direction of the main motors, the phase sequence should be uniformly adjusted at the input power supply; do not adjust the phase sequence of the main motors individually.

3.Before connecting the power supply, be sure to check that the chassis grounding terminal is securely grounded.

When spraying concrete, excessive air pressure will result in high rebound, excessive dust, and high cement consumption; while insufficient air pressure will result in low spray velocity and poor compaction. If the operating air pressure is too high, the material beam will disperse and rebound significantly; if it is too low, the material beam will be weak and will not adhere well to the rock surface.

4.Wet shotcrete nozzle movement: The nozzle should move in a continuous circular motion, forming a spiral, with the last rotation pressing one-third of the previous rotation. The spraying path should be an "S" shape from top to bottom. Concrete in tunnels should be sprayed according to the New Austrian Tunneling Method (NATM), first on the arch and then on the wall. Wet shotcrete spraying thickness: Wet shotcrete spraying achieves a greater thickness than dry (wet) shotcrete, reaching 70mm for arches and over 100mm for sidewalls. The thickness of the spray layer is primarily influenced by the concrete slump, the effectiveness of the accelerator, and the surface temperature. Generally, a slump of around 80mm produces a thicker spray layer; concrete setting within 2 minutes is optimal; and the surface temperature should be above 15°C.

5.Wet shotcrete spraying technology, as an important method in construction, is increasingly being used. Due to its significant advantages, spraying technology is increasingly gaining a dominant position in shotcrete production.