Concrete damage

First and foremost, a distinction must be made between damage to the concrete as such, considered to be an artificial rock, and damage to concrete, due to an underlying phenomenon of reinforcement corrosion.

In the case of damage to the concrete itself, the following can be considered:

• Sulphate attack
• Acid attack
• ASR (alkali-silica reaction)
• Frost-thaw damage

Consider, for example, the effect of acids on concrete in chemical plants, frost-thaw damage on external pavements, etc.

Damage caused by reinforcement corrosion (concrete rot) is a completely different phenomenon, which is often present but does not have to be visible on the surface. It is therefore quite possible that reinforcement corrosion is present, while there are no cracks or rust spots on the concrete surface. That is why curative actions are often taken too late and the costs of repair run high when people wait for the debris to fall down.

The main causes of reinforcement corrosion are:

• The presence of chlorides (swimming pools, balconies on the coast, parking garages ...)
• CO2 penetration into the concrete (the so-called carbonation process).

Recognize damage

Sanacon has the expertise to recognize both classical and more complex damage phenomena. Based on an initial visual inspection of the damage, a hypothesis is formulated that must be verified in a later investigation. For an appropriate concrete repair it is important to know the cause of the presence of rust spots. For example, a concrete repair for reinforcement corrosion as a result of carbonation is fundamentally different than when the corrosion is caused by the presence of chlorides.

Repair strategies

The following repair principles are described in standard EN 1504-9:

• Principle 1 - Protection against intrusion
• Principle 2 - Humidity control
• Principle 3 - Restoration of concrete
• Principle 4 - Structural reinforcement
• Principle 5 - Physical resistance
• Principle 6 - Chemical resistance
• Principle 7 - Maintenance or restoration of passivity
• Principle 8 - Increase resistivity
• Principle 9 - Check cathodic zones
• Principle 10 - Cathodic protection
• Principle 11 - Control of anodic zones

Principles 1 to 6 are specifically linked to damage phenomena with regard to concrete itself. When it comes to damage as a result of reinforcement corrosion, popularly known as "concrete rot", principles 7 to 11 can be used.

Sanacon can determine the cause, severity and extent of the damage on the basis of an on-site investigation, based on scientific methods, and, in the light of the intended lifespan of the structure, can draw up an appropriate repair advice based on a choice of the aforementioned recovery principles.

As an independent consultancy bureau, Sanacon will always prescribe methods and materials based on performance requirements. For coatings and repair mortars, for example, these will always be determined according to the EN 1504-2 and EN1504-3 standards respectively.