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Lime grouting and injection
Coulinex - Lime grouting and injection
St. Astier has developed a product named COULINEX based on NHL 3.5 with no cement or pozzolanic addition. It can be used on its own or with addition of sand, depending on the voids size.
The water addition is dictated by the amount of COULINEX used and the fluidity required.
When grouting porous materials, clean water should be used first to reduce suction to avoid the risk of blocking some voids, impeding the grout to fill the whole of the grouting area. This operation should be conducted slowly and with care, making sure that there is no free water (saturation) in the cavity. This can be done by making a small hole in a joint at the bottom of the grouting area, if water pours out one should stop adding water and wait for the water to be absorbed by the structure.
COULINEX can be applied by gravity feed or by pump with a very low pressure. In fine injection work it can be applied neat or with very fine aggregate, depending on the voids size.
Injection and grouting work normally starts from the lowest part of a structure or the section of a structure to be treated. Re-pointing work is done before the intervention, to the level of the first grouting/injection point. About 24 hours later, the operation is repeated on the section above, until completion of the work.
Grouting can also be used in retro filling work when stones or bricks have been changed in a section of a structure. Here the size of the voids is known and therefore the joints work can be done on larger areas. To allow COULINEX to achieve its best performance, however, the grouting work should be performed in stages at 24 hours interval, depending on the porosity of the materials with which the grout will be in contact.
In choosing a grout, particular attention should be paid to its "stability". This is the property of the grout to retain unnecessary water (this is the water exceeding the amount required for hydration and fluidity) not allowing it to flow freely. It is measured in hours and, ideally, a NIL value should be achieved within 24 hours although figures of about 1% are still considered low enough for further work to continue. In other words, within 24 hours either NIL or only a small percentage of water is free to flow. Tests conducted on COULINEX show that this value is achieved within the time stated.
Injection and grouting materials should not contain sulphates and organic components, especially in restoration/conservation work. None of these is contained in COULINEX.
Dense and non breathable mixes (cementitious) can cause severe long term damage, especially if dense mortars are applied also in the joints, as eventual moisture will not be able to evaporate and condensation will be created. In the presence of porous stones or bricks, the moisture will be absorbed by the bricks or the stones. Moisture movement will also generate the migration of salts that might be present within the structure and unnecessary pressure will be generated within the structure itself.