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How is a reactive protective system for concrete and masonry, reinforced and pre-stressed concrete made?

Structures in concrete and masonry, reinforced or pre-stressed concrete are rarely subject to mechanical stress but they may be subject to harsh climatic agents. It is therefore essential for the correct procedure to be followed, from the base-coat or primer, to the finishing coat, to ensure the system delivers effective fire protection.
There are a number of phases to the treatment
  • preparing the surface
  • intermediate adhesion treatment
  • fire-protection treatment
  • finishing treatment
Preparing the surface and the intermediate adhesion treatment. 
The surfaces to be prepared can be of different types and in different states of preservation, with each situation requiring different preparation.
The first operation is to make a careful inspection of the structure and the area to be protected from fire. It is necessary to verify the general state of the structure, its solidity, the presence of any contaminants, faults, the emission of water vapour, chemical attack, etc. and above all to check the degree of moisture within the structure, which must be within the prescribed parameters for the type of wall. The way the under-surface is prepared will vary according to the type of surface to be treated. More specifically:
  • A new surface must be checked for the presence of any contaminating agents and for its solidity, whether any water is present on the surface to be treated, its degree of alkalinity and the presence of any soluble salts that could lead to the phenomenon of efflorescence. Any impurities should be carefully cleaned off and if the surface is dusty a product that promotes adhesion must be used. Amonn offers Amotherm Brick Primer WB, a single-component acrylic fixative and we still recommend its use if the surface appears to be in excellent condition.
  • If the structure is old and has been previously painted it must be thoroughly cleaned to eliminate any paint residues not perfectly anchored to the surface. The most effective way of preparing old surfaces for treatment is by low-pressure sand washing, alternatively the surface can be thoroughly brushed, preferably using mechanical equipment, removing any old paint that is peeling off or any dirt, dust or other residues. It is particularly important to remove any dust and materials that are crumbling or loose, because these will have absorbed all the contaminating agents and any products caused by reaction that may have occurred as a result of the prolonged action of various harsh agents. 
If the metal reinforcements have lost their concrete cover in some places and the reinforcement appears to have deteriorated, it is necessary for the reinforcement to be passivated, a treatment that requires the metal parts that have lost their covering to be cleaned of all rust and dirt in general and to restore the oxidised metal to its white state. Once the preparation is complete the passivation treatment can be applied using a suitable product that forms a protective film preventing contact between the steel and moist air that would cause corrosion. Amonn offers Amotherm Steel Primer Epoxi SB. Once the passivation process is finished, the concrete that has been removed must be replaced and the original geometry restored. 
For the best result, we always recommend trying to remove any old layers of paint and to use a suitable fixative. Amonn offers Amotherm Brick Primer WB.
  • When applying the coating to masonry that has not been plastered, the surface should be checked for contaminating agents. Any impurities must be carefully cleaned off, after which a fixative should be applied. Amonn offers Amotherm Brick Primer WB, a single-component acrylic fixative.
The fire-protection treatment. Once the surface has been completely prepared, the fire-proofing treatment can be applied using a spray, paintbrush or roller. It is essential that reactive/intumescent systems must only be applied to a properly prepared, compatible surface. We advise against applying the protective coating in unfavourable environmental conditions and to read the technical information provided by the manufacturer very carefully. The thickness of paint to be applied in order to achieve the required protection is obtained by applying multiple coats, ensuring the correct amount of time has elapsed between coats. The thickness achieved during application can be checked using a wet film micrometer or, once it has dried, using a digital ultrasonic micrometer. Be particularly careful when measuring the thickness because the instrument is unable to distinguish between old and new paint and therefore the reading may be incorrect. If this is the case take a digital measurement before and after the treatment and subtract the thickness of the pre-existing layers from the new measurement.
The finishing treatment. 
If the treatment is applied in unfavourable environmental conditions, in damp interiors with the occasional presence of water or in semi-exposed areas such as sheds, a specific protective finishing treatment should be used. This can also be used merely for aesthetic effect if a coloured finish is wanted. Amonn recommends Amotherm Brick Top WB, a protective water-based topcoat that protects the intumescent treatment from harsh environmental agents and makes the film resistant to condensation, damp and water. 
We would remind you that intumescent paints for brickwork cannot be used outdoors or where there is a likelihood of repeated and prolonged contact with water or where there may be rising damp, as in for example, insufficiently damp-proofed basement walls.
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