Remove damaged concrete, for example by chiselling or water sand blasting. The base must be undamaged, clean, and damp enough to be darker in colour. Begin wetting the base on the previous day. In dry conditions, wet the base during the work as well. Best adhesion can be achieved to a rough base.
In order to reduce dust problems and to ensure an even spraying result, wet the concrete before spraying. A suitable moisture level is around 6% by weight. The pre-wetting is easiest by using Fescon Oy’s automatic mixer & silo combination. The workability time of pre-wetted concrete is less than two hours.
The work must be performed in accordance with the Road Administration’s SILKO guidelines and BY 29 Shotcreting Instructions (1993). The maximum layer thickness sprayed at a time is around 50 mm depending on the conditions. Reinforcements/meshing in accordance with the designer’s instructions. When spraying sections with water leaks, you can use an accelerator. When spraying several layers, the previous layer must be strong enough. If you wish, you can float the shotcrete surface. Brushing is also possible. The lowest usage temperature is + 5°C. Ensure that the temperature does not fall below 0°C during aftercare.
Shotcrete must be given aftercare until its strength is 60% of the nominal strength. This means at least for seven days. Give aftercare by spraying with water or applying a curing compound. The longer the aftercare, the better the end result. Follow the SILKO instructions and the BY 29 Shotcreting instructions (1993) in aftercare as well.
Storage and handling of waste
See the separate storage and disposal instructions https://www.fescon.fi/en/material-bank