The tunnel manufacturer in wet shotcrete machine said that the hydraulic concrete wet shotcrete machine is a pumping wet spraying machine, which has the characteristics of high pumping pressure, long conveying distance, low rebound and high construction efficiency. Hydraulic concrete wet shotcrete machine is widely used in shotcrete support in railway tunnels, highway tunnels, water conservancy culverts, mine tunnels, dam slopes, building foundation pits and military projects.
How to use hydraulic concrete wet shotcrete machine.
Tunnel manufacturers in wet shotcrete machine introduce the usage of hydraulic concrete wet spraying machine:
- Before starting the hydraulic concrete wet shotcrete machine, turn on the high-pressure air, idle for a few minutes, blow out the residual liquid and dirt in the machine and pipeline, and check whether the pipeline is unblocked; When the main air valve is closed, the system can only be started when the air pressure is higher than 0.5MPa.
- Purge all surfaces to be sprayed with compressed air or pressure water to remove loose impurities or dust on the surfaces to be sprayed; Ensure proper wet spraying speed to facilitate concrete compaction.
- Keep a proper distance between the nozzle and the sprayed surface, and the wet spraying angle should be as close as possible to 90 degrees, so as to obtain a larger pressing force and a smaller rebound; Master the wet spraying sequence correctly, so as to avoid honeycomb or sand bags on the corners and the back of steel bars.
- When starting or stopping wet spraying, send a signal to the driver in wet spraying machine, and inform the driver in wet spraying machine to stop the operation when the nozzle can’t spray the material flow evenly.
- Clean up the sandbags or sagging concrete on the spray surface in time for wet spraying again; At the end of wet spraying, carefully clean the nozzle.
- When the surface to be sprayed is ready to repair the damaged structure, first remove the loose materials, thoroughly rinse them with pressure water, and then blow away the accumulated water.
- The tunnel manufacturer in wet spraying machine said that the operation of wet shotcrete machine would affect the rebound, compactness and uniformity of concrete flow. It is necessary to correctly control the working wind pressure of the wet shotcrete machine to ensure the uniformity of material flow in the nozzle. The working wind pressure in the wet shotcrete machine should be adjusted according to the appropriate wet spraying speed. If the working wind pressure is too high, that is, the wet spraying speed is too high and the kinetic energy is too large, the rebound will be increased. If the working wind pressure is too low and the compressive strength is small, it will affect the concrete strength. The material flow in the wet spraying machine should be uniform to ensure the uniform distribution of the accelerator in the concrete.
- Nozzle operation: The tunnel manufacturer in wet shotcrete machine indicated that the proper distance between the nozzle and the sprayed surface is generally 0.8 ~ 1m. Wet spraying shall be carried out by sections, blocks and blocks (when wet spraying is carried out, the length of each section shall not exceed 6m, and the size of each section shall be 2m×2 from bottom to top). The sprinkler should move continuously in the form of a spiral circle, the diameter of which is about 20 ~ 30m, and the last circle presses one third of the previous one. The wet spraying route should be “S” from top to bottom.
- Wet-sprayed thickness: The thickness of wet-sprayed concrete at the first wall can reach more than 10cm, and that at the first arch can reach 7cm. The main factors affecting the thickness of shotcrete layer are the slump of concrete, the action of accelerator and the air temperature. Generally, a thick shotcrete layer can be obtained, with a slump of about 8 cm, which can ensure that the concrete can set well within 2min, and the working surface temperature should be above 15℃.
- The tunnel manufacturer in wet shotcrete machine said that the tensile strength and bonding strength of layered wet-sprayed concrete are very low for fresh wet-sprayed concrete. Once the dead weight of wet shotcrete is greater than its bonding strength with the sprayed surface, it will droop and fall off, so wet shotcrete should be done in layers. The interval between layers before and after wet spraying is 2 ~ 4 hours, and the thickness of one wet spraying shall be subject to the fact that wet spraying concrete does not slip or fall off.
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