The prerequisite for a successful concrete repair is correct preparation. The area for repair must first be cleaned carefully. All damaged concrete and reinforcement corrosion must also be removed. This can be carried out by hand or using mechanical aids such as hydrodemolition or abrasive blasting. Select the cleaning method taking into consideration the extent of the damage. Supplement or replace damaged reinforcement.
The concrete cover to reinforcement should never be less than 20 mm. Depending on the type of structure the cover may need to be a lot greater than that. The shape of the repair site should be suitable so as to avoid cavities.
Water the site of the repair until it is moist, in other words absorbent but not saturated. Then cover the cleaned concrete and reinforcement with Bemix Korrohäft anticorrosion bonding slurry. Apply the next layer before the Bemix Korrohäft anti-corrosion bonding slurry has dried. Build up the damage using Bemix R50 which are easy to work and mould repair mortars.
Use Bemix Betongspackel concrete filler on more demanding repairs; this has a long working time, a smooth consistency and is ideal for many repair sites.
Water the site of the repair until it is moist, in other words absorbent but not saturated. For small repairs and a thin concrete cover prepare the concrete and reinforcement using Bemix Korrohäft anti-corrosion bonding slurry. Larger castings do not normally need to be treated with Bemix Korrohäft anti-corrosion bonding slurry if the watered concrete has a rough, tooled surface.
Use Bemix P3 or A3 for casting depending on the thickness of the layer. These products are highly resistant to frost, chemicals and mechanical wear. In addition they provide good protection to reinforcement.
Hydroblasted surfaces do not normally need further preliminary treatment. Surfaces cleaned dry are to be washed with water at high pressure. When applying shotcrete the surface should be somewhat absorbent. Any exposed reinforcement bar should be treated with Bemix Korrohäft anti-corrosion bonding slurry. Bemix SP40 is then applied using dry mix spray equipment. The mortar is based on Portland construction cement and is suitable for repairs that have a requirement for low shrinkage and cracking. Shotcrete is available in 0–6 millimetre.
Following repair the mortar or concrete must be protected from drying out too quickly. This can be carried out through wetting, or, where possible, by covering it with plastic or wet fabric for about a week. This treatment should be adapted to the climate and product used. If a more uniform surface structure is desired following a repair, Bemix Korrohäft anti-corrosion bonding slurry can be applied to the repair site and surrounding concrete, if surfaces are not subject to wear.