Protection for Concrete
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Surface protection of concrete structural members is necessary to protect the structure from damage due to environmental considerations.
Corrosion of reinforcement due to a permeability of water/moisture, a chemical attack on structural members, structures nearby sea-coast etc. are all responsible for damage to concrete structures. So, surface protection of concrete members becomes necessary to prevent such damages.
Methods of Protecting Concrete Surfaces from Damages and Deterioration
Following are the surface protection measures that may be taken to minimize or stop the damage to concrete structures:
- Hydrophobization
- Painting
- Impregnation
- Sealers
- Coating
The degree of surface protection for concrete structures achieved from these measures increases in the order as they have been listed above. The difference between various methods of surface protection lies in the process of how the protection of the concrete surface is achieved.
In the impregnation system, the protection is achieved through prevention of capillary absorption of water by the concrete.
Materials for concrete surface protection
(a) The materials used for impregnation, hydrophobation methods for concrete surface protection are:
- Silicon organic solutions
- Resins
- Oils
(i) Silicon organic impregnation materials are:
- Siliconates
- Silanes
- Siloxanes and
- Silicon resins
(ii) Resins:
The resins provides protection to concrete surface by forming a thin film on the surface of the pores and narrowing of the capillaries. Types of resin materials used for this are:
- Polymethylmethacrylate (PMMA) and
- Epoxy resins
(iii) Oils:
Oil is a low molecular, organic compound and is used for impregnation. Linseed oil is most widely used oil for impregnation. Linseed oil may be used in the following types:
- Boiled (linseed) oil
- Linseed stand oil and
- Mixture products of boiled (linseed) oil or
- Linseed stands oil with not more than 15% unsaturated organic compounds.
Sealers:
In contrast to impregnation and hydrophobization, sealers are more effective in protecting the concrete surface by forming a film on the surface. Sealing of the concrete surface is achieved by increasing the applied quantity of an impregnation agent, which tends to form a film, or through the choice of suitable resins. The following plastics are commonly used as sealers for the concrete surface:
- Epoxy resins (EP)
- Polyurethane resins (PU)
- Polymethylmethacrylate resins (PMMA); and
- Unsaturated polyester resins (UP)
Sealers can also serve as a primer for coatings.
(c) Coatings:
Coatings provide additional protection to a concrete surface as compared to sealers. Consideration should also be given to the fact that coatings, as compared to sealers, have an increased resistance to the diffusion of internal moisture. There are two types of coatings used, thin coating and a thick coating.
Thin coatings follow the contour of any unevenness of the concrete surface. Thick coatings are used to form as much as possible a plain surface with a thickness of 1mm or larger. Therefore, a thick coating will smooth out any unevenness of the surface.
Methods of Using Surface Protection Materials
The concrete surface is first prepared for the impregnation of surface protection materials. The surface is prepared based on the depth of impregnation required on the concrete surface. Then the impregnation liquid is placed on the concrete surface in an amount to fill the voids on the surface, then is sprayed on the concrete surface with the help of a brush, lambskin roller or by spraying.
Depending on the absorptive capacity of the concrete surface, several repetitions may be necessary. For the first application on the concrete surface, a thin solvent containing impregnation systems may be required to achieve a deeper penetration.
A penetration depth of surface protection material is especially important where the wearing of concrete surface is expected. Therefore, impregnation protection systems are only suitable where the concrete surface will not be removed by abrasion, damaged or locally disturbed by the formation of a crack.
While impregnation with resins may be successfully used on horizontal surfaces, hydrophobizing impregnations are not suitable for horizontal surfaces where water will stay on the surface. Therefore, the primary field of application of hydrophobizing impregnation is on vertical or sloped surfaces, where the water can flow off easily.
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