FAQs about shotcreting

1. How to prepare the surface for shotcreting?

Make sure the surface is free of stains, paint, grease marks and detached concrete, then sandblast it with hydrodynamic or water-jet-blast process. The surface should be roughened to ensure proper adhesion. Directly before concreting, blow and flush the surface with water at a pressure of 0.2 - 0.3 MPa.

2. Does the water/cement ratio have any effect on the mixture?

Yes, the strength of the coating directly depends on it. The optimal ratio, as proven in practice, is from 0.4 to 0.45.

3. Is it possible to use shotcreting under domestic conditions?

Yes. For this you will need a hopper, and you do not have to have professional skills to use it, as the main requirement is to maintain the optimal proportions of the mixture.

4. Are there any differences between working with slow-curing and fast-curing mixes?

Yes, there are. When working with the fast-curing mixes, the mixing chamber in the machine should be located directly in front of the nozzle, while when working with the slow-curing mixes, it should be located 2-3 meters away from it, which will extend the flow of the mixture.

5. How can the application layer during shotcreting be controlled?

It can be controlled with the help of special beacons or feelers. On average the thickness of one layer should be in range from 5-7 mm to 20-50 mm, depending on the type of mixture, the location of the surface to be coated and the shotcreting method.

6. How soon can the second layer of mixture be applied?

If you are using pure concrete mixture, then you can apply the second layer after about two hours to both horizontal and vertical surfaces. If the mixture has accelerants and plasticizers added, the second layer can be applied after about 20 minutes to horizontal surfaces and after 40 minutes to vertical surfaces.

7. Can the rebound material be reapplied?

No, as this will degrade adhesion as well as other coating properties.

8. How to maintain the finished shotcrete coating?

If the air temperature is above 5ºC, then it should be periodically moistened during the first week — the first time in 24 hours after application.