Penetrating sealers

Several European DOTs specify the application of penetrating sealers to exposed concrete on bridges exposed to salt spray or run off. These are discussed in Section 6.3. They have very particular application requirements. In the United States sealers are also used on bare concrete bridge decks. Their effectiveness on trafficked surfaces has not been fully investigated. 

The advantage of silane type penetrating sealers is that they are inexpensive compared with cathodic protection, epoxy coated rebars or other preventative or active treatment methods. If penetration is good then there is no maintenance 

Applying cathodic protection or chloride removal through penetrating sealers if necessary is usually possible. 

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Resin solution penetrating sealers are now available which, for very large warehouse floors, are comparable in applied costs with the concrete surface hardeners and are now being increasingly specified. Experience indicates that certain acrylic resin solutions are proving more durable and offer better protection to chemical and oil spillage than concrete surface hardeners. Acrylic resin solution sealers can markedly improve the abrasion resistance of concrete floors and have rescued a number of poor-quality floors. 

Water-based decorative wall paint Low-viscosity solvent-free epoxy sealer 42 100 38 15 min 2 h 16 h Flat, decorative finish on walls and ceilings, for interior and exterior use Excellent penetrating sealer and adhesion promoter for concrete and prior to application of coatings, excellent chemical resistance... 

Silane A solution of a low molecular weight composition of silicon and hydrogen used as a penetrating sealer for concrete surfaces. 

Nytek 645. [Maag Agrochem.] Industrial fungidde, penetrant sealer, and water repellent. 

Nytek 045. [Maag Agroeb ] Industrial fungicide, penetrant sealer, and w repellent. 

Qrganosilane. [Degussa] For penetrating sealers for concrete and wood. 

Field devices are most effective when used to check improvements in water absorption after a treatment such as the application of a penetrating sealer such as silane. The ISAT test (BS 1881-208, 1996) is particularly useful for checking the effectiveness of coatings. 

Penetrating sealers have been recommended as a way of stopping chlorides getting into concrete. The chemistry of the process is that silanes, siloxysi-lanes and similar chemicals will penetrate the pores of the concrete and react with the water in the pores to from a hydrophobic (water repelling) layer that stops water getting in as a liquid (that may carry salt with it), but allows water vapour in and out of the concrete so that it will breath . 

The penetrating sealer is within the concrete so it is protected from physical damage and degradation by ultraviolet light, etc. The problem is that the colourless liquid must be applied so that most of it gets into the pores and there is enough water in the pores to react, but not too so much that it washes the sealer back out and pores remain uncoated. There is still some debate over the true penetration depth of sealers to good quality concrete in the field. 

In the United States many highway agencies have applied penetrating sealers to concrete bridge decks. There has been no definitive research to show whether sealers work on trafficked surface or for how long they are effective. 

The penetrating sealers approved for application to highway structures in Europe are generally solvent free and are applied in a series of coatings by thorough wetting of the surface with the sealer with a drying period between coats. 

In the United States the SHRP program developed two field tests for penetrating sealers (Whiting et aL, 1992). These can be used in situ to determine the effectiveness of sealers. One is a surface conductivity test and the other is a variation on the initial surface absorption test (ISAT). If silane-based sealers are being used then these tests are recommended. They... 

Chem. Descrip. Methoxy-functional silane Uses Water repellent, penetrating sealer for cementitious substrates Features Good alkali resist., low volatility, exc. penetration, exc. water repellency, suitable for both dry and damp surfaces, reducible with solv. VOC compliant... 

Concrete flooring in the brine area is liable to disintegration by brine, and it is protected by coating with materials such as magnesium or zinc fluosilicate, epoxy or silicone penetrating sealers, and drying oils. Concrete surfaces exposed to mechanical wear are treated with 3- to 6-mm thick epoxy surfacing materials. Sumps and trenches employ reinforced polyester or epoxy resin systems. 

The advantage of silane type penetrating sealers is that they are inexpensive compared with cathodic protection, epoxy coated rebars or other preventative or active treatment methods. If penetration is good then there is no maintenance and a long lifetime (in theory) as the silane forms a hydrophobic layer inside the concrete pores. There is no impact on the design or performance of the structure. The disadvantages are... 

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