Choosing the correct materials for restoration
The success of a concrete repair is linked to the correct choice of materials to be used. A good mortar for the repair such as:

Mapegrout Thixotropic
Mapegrout BM or
Mapegrout Hi-Flow
.
Must have the following qualities:

Low shrinkage
Low permeability
Good adhesion to existing concrete
Coefficient of elasticity similar to the existing concrete
Ease of application

The use of normal cement mortars has been proved to be unsatisfactory because of the shrinkage of the fresh concrete causing detachment between the old and new materials or cracks in the repair itself.

Clan have worked with Mapei to produce concrete repair mortars which have controlled expansion, now found in the pre-measured Mapegrout mortars creating a pre-compression in the material which cancels or reduces the negative effects of the shrinkage that follows.

Sequence of repairs
Remove the concrete to completely expose the reinforcing rods. Removal of the concrete must include all of the carbonated concrete. Once the demolition is completed the exposed surfaces should be cleaned by either water or sand blasting. During this cleaning operation the reinforcing rods should be cleaned down to bright steel.

After cleaning the reinforcing rods should be treated with an alkaline product such as Mapefer to prevent further rusting.
Where the corrosion has reduced the rods by more than 30% new reinforcing rods should be installed. Mapefer should also be applied to these new rods.

The concrete repair material should be a shrinkage controlled fibre reinforced mortar such as Mapegrout BM. This mortar is characterised by its high elastic properties allowing a vertical application of up to 50mm in one coat without using formwork.