Preserving or restoring passivity

The corrosion of steel reinforcement in concrete can be minimised by replacing concrete cover with high quality repair mortars and concretes from Weber. Also available are materials for increasing effective cover such as a fairing mortar and anti carbonation coatings.

Problems & Solutions

BS EN 1504 Principle 7 is concerned with preserving or restoring the passivity of the concrete by creating chemical conditions in which the surface of the reinforcement is maintained in or is returned to a passive condition. Where the reinforcement is passive, an additional layer of mortar or concrete may be added over carbonated concrete to provide additional protection.

1. Carbonation

Carbonation to concrete leading to reinforcement corrosion and localised spalled concrete to areas of low concrete cover.

2. Delaminated concrete

Due to widespread carbonation or chloride-induced corrosion.

3. Permeable concrete

Permeable concrete due to inadequate curing, shrinkage cracks, poor compaction and a weak surface layer to the concrete.

4. Low concrete cover

Low concrete cover to reinforcement in exposed areas of the structure.


Methods of protection based upon the BS EN 1504 Principle 7 is the use of the following:

  • 7.1 Increasing concrete cover to reinforcement
  • 7.2 Replacing contaminated or carbonated concrete
  • 7.3 Electrochemical realkalisation of carbonated concrete
  • 7.4 Realkalisation of carbonated concrete by diffusion
  • 7.5 Electrochemical chloride extraction

1. Replacing concrete

Replacing concrete with hand-applied mortars and a corrosion inhibitor. Use:

2. Sprayed concrete

To replace contaminated concrete and to increase concrete cover. Use:

3. Recasting concrete

Recasting concrete to pavement to improve and restore passivity. Use webercem pyrapatch or webercem pyratop.

4. Increasing concrete cover

Increasing cover with additional mortar or concrete. Use webercem spray DS.

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