Hydrophobic impregnations
Hydrophobic impregnations are non-film-forming products that are typically designed to reduce the water absorption of the concrete.
By doing this, all degradations of concrete caused by/or involving water can be reduced, and hence the systems will protect the structure.
Typical hydrophobic impregnations are made from different types of silanes, which react chemically with concrete and create a water-repellent surface.
There are several different commercial products available on the market with different silanes, with or without solvent, and with key features, such as “long-contact time,” and the addition of migrating corrosion inhibitors to the silane.
The effect and expected lifetime of the different systems will vary based on the following factors:
- The type of product used (type of silane, active content, migrating corrosion inhibitor content, and the “contact-time”) – and the documented characteristics of this specific product.
- The existing moisture content in the concrete (as the products need to be absorbed and react in the pores of the concrete this will favour concretes with low humidity).
- The water/cement ratio of the concrete (as the number of pores will be less for concrete with a low w/c-ratio).
- The depth of impregnation can be used as a quality parameter for both performance and expected lifetime.
Hydrophobic impregnations are widely used to protect marine structures in many countries in Europe.
However, before using this protection method a study must be carried out to determine if it will be effective, which will depend on various aspects, such as the type of concrete, the characteristics of the seawater, the climatology of that geographical zone, etc.
Furthermore, it is important to note that this method does not stop the carbonation, but rather keeps it dormant.
Therefore, after approximately five years when the product stops providing humidity protection, if the intervention is not repeated with a new application, an accelerated carbonation will occur when humidity/water reaches the rebar.
As a result, the brown stripes that provide early warning will not appear, resulting in direct severe corrosion.
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