Concrete structures are susceptible to damage from environmental factors such as moisture, chemical exposure, and proximity to coastal areas. The permeability of water can lead to corrosion of the reinforcement, which can compromise the integrity of the entire structure. To prevent such damage, it is necessary to provide surface protection for concrete structural members. This protection will help to mitigate the effects of corrosion and chemical exposure, and preserve the structural integrity of the concrete members. Whether in coastal or inland areas, surface protection is essential for the long-term durability and safety of concrete structures.
Methods of Protecting Concrete Surfaces from Damages and Deterioration
To minimize or prevent damage to concrete structures, there are several surface protection measures that can be taken. These measures include hydrophobation, painting, impregnation, sealers, and coating. The effectiveness of these measures increases in the order listed, with coating being the most effective.
The difference between these methods lies in how they protect the surface of the concrete. In the case of impregnation, the protection is achieved by preventing water from being absorbed by the concrete through capillary action. This can be done by either making the walls of the pores hydrophobic or by narrowing the capillary ducts through the formation of a film on the walls.
Sealers and coatings, on the other hand, create a closed film on the surface of the concrete, providing a higher degree of protection. The type of material used for surface protection will determine how effectively the capillary absorption of water is prevented.
Materials for concrete surface protection
(a) The materials used for impregnation, hydrophobation methods for concrete surface protection are:
Silicon organic impregnation materials, which include siliconates, silanes, siloxanes, and silicon resins, are commonly used to provide protection and impregnation to various materials.
Resins are another type of material used for protection and impregnation of surfaces. They work by forming a thin film on the surface of pores, which narrows the capillaries. Two common types of resins used for this purpose are polymethylmetacrylates (PMMA) and epoxy resins.
Oils are low molecular, organic compounds that are also used for impregnation. Linseed oil is the most widely used oil for this purpose and is available in boiled, stand, and mixture forms. Boiled linseed oil, stand linseed oil, and mixture products of boiled or stand linseed oil with no more than 15% unsaturated organic compounds are all viable options.
(b) Sealers:
When it comes to protecting concrete surfaces, sealers are more effective than impregnation and hydrophobation methods. They work by forming a film on the surface, which provides a greater level of protection. To achieve this, a larger amount of impregnation agent can be applied, which will tend to form a film. Alternatively, suitable resins can be chosen to create a sealant.
There are several types of plastics commonly used as sealers for concrete surfaces, including epoxy resins (EP), polyurethane resins (PU), polymethylmetacrylate resins (PMMA), and unsaturated polyester resins (UP). These plastics are known for their effectiveness in creating a durable film on the surface of the concrete, which can protect against a variety of environmental factors.
One of the benefits of using sealers is that they can also serve as a primer for coatings. This means that if a concrete surface needs to be painted or coated, the sealer can act as a base layer that helps the coating adhere to the surface more effectively. This can improve the overall durability and longevity of the coating, as well as the concrete surface itself. Overall, sealers are an effective way to protect concrete surfaces and can provide long-lasting benefits for a variety of applications.
(c) Coatings:
When it comes to protecting concrete surfaces, coatings offer more benefits compared to sealers. Coatings are particularly effective at resisting the diffusion of internal moisture, making them a popular choice for long-term protection. Thin coatings are designed to follow the contours of any unevenness present on the surface of the concrete. This makes them an excellent choice when the goal is to maintain the original texture of the surface. On the other hand, thick coatings are used when the aim is to create a plain surface with a thickness of at least 1mm. The thickness of the coating allows it to smooth out any irregularities present on the surface of the concrete. By creating a uniform surface, thick coatings provide an extra layer of protection for the underlying concrete.
A good coating materials should have following properties:
Coatings are frequently used to protect concrete surfaces against chemical attacks, temperature changes, abrasion, and cracking. The coatings need to possess specific properties, such as good adhesion to the surface, sufficient tensile strength, elasticity, and abrasive resistance, as well as a coefficient of thermal expansion comparable to that of concrete.
Various types of coatings are suitable for protecting concrete surfaces, including epoxy resin, bituminous compound, linseed oil, silicon preparation, rubber emulsion, and even mere cement coating. Coatings are also used for sealing cracks in concrete structures, and for this purpose, high elasticity coating materials are required.
Epoxy systems are commonly used for coating concrete surfaces, but they can exhibit changes in properties with variations in temperature and exposure to sunlight. Thin coatings can only bridge cracks up to 0.2mm in width, with limited debonding of the adjacent coating layer possible. To bridge larger crack widths, a fiber material, such as textile fabrics, can be inserted into the coating.
Recently, two-component liquid sealers have been developed for spraying onto concrete surfaces. These sealers have a low modulus of elasticity and improved elongation, enabling them to bridge larger cracks. With the proper selection of coatings and sealing materials, it is possible to provide long-lasting protection for concrete structures.
Methods of Using Surface Protection Materials
In order to impregnate a concrete surface with protection materials, it must first be properly prepared based on the desired depth of impregnation. The surface is then treated with an impregnation liquid, which is applied in an amount that fills the voids present on the surface. This can be achieved through the use of a brush, lambskin roller, or spraying method, depending on the absorptive capacity of the concrete. It may be necessary to repeat this process multiple times to achieve the desired level of impregnation, especially when using a thin solvent-containing impregnation system for the initial application.
It is crucial to consider the penetration depth of the surface protection material, particularly if the concrete surface is expected to experience wear and tear. Impregnation protection systems are only effective if the concrete surface is not subject to damage from abrasion or the formation of cracks. Resin-based impregnation is suitable for horizontal surfaces, but hydrophobizing impregnations are not recommended for surfaces where water will accumulate. Therefore, hydrophobizing impregnation is primarily used on vertical or sloped surfaces, where water can easily flow off.