Concrete structural members are susceptible to damage caused by various environmental factors, including the permeability of water and moisture, chemical attacks, and proximity to sea-coast structures. The corrosion of reinforcement is a significant concern, and it can lead to the deterioration of the entire structure. As a result, it becomes imperative to provide surface protection for concrete members to prevent such damage.
To mitigate the impact of environmental factors on concrete structures, protective measures are necessary. When concrete members are exposed to water and moisture, they become vulnerable to corrosion, which can result in significant damage. Similarly, chemical attacks on structural members can cause severe deterioration and lead to structural failure. Structures located near the sea-coast are particularly at risk, and without adequate protection, their longevity is severely compromised.
Therefore, to prevent these problems, surface protection of concrete members becomes necessary. By taking measures to protect the surface, the underlying structure can remain intact and durable. In this way, it is possible to minimize the impact of environmental factors and prolong the life of concrete structures.
Methods of Protecting Concrete Surfaces from Damages and Deterioration
Various surface protection measures can be employed to prevent or reduce damage to concrete structures. These measures include hydrophobation, painting, impregnation, sealers, and coating. These methods provide varying degrees of surface protection, with the level of protection increasing in the order listed above.
The process by which surface protection is achieved differs between these methods. In the case of impregnation, the protection is attained by preventing capillary absorption of water by the concrete. This is accomplished by either hydrophobation of the pores at the walls or by narrowing the capillary ducts due to film formation on these walls, depending on the material used for surface protection.
Sealers or coatings, on the other hand, create a closed thin film on the surface of the concrete, providing a higher degree of surface protection. Overall, the choice of surface protection method will depend on the specific needs of the structure and the desired level of protection.
Materials for concrete surface protection
(a) The materials used for impregnation, hydrophobation methods for concrete surface protection are:
Silicon organic solutions, resins, and oils are commonly used for impregnation and protection of various materials. Silicon organic impregnation materials include siliconates, silanes, siloxanes, and silicon resins. These materials are used to create a protective layer on surfaces and provide resistance to water and other chemicals.
Resins are another type of material used for surface protection. They form a thin film on the surface of the pores, narrowing the capillaries and providing protection to concrete surfaces. Polymethylmetacrylates (PMMA) and epoxy resins are two types of resin materials commonly used for this purpose.
Oils are also used for impregnation, with linseed oil being the most widely used oil for this purpose. Linseed oil may be used in boiled form, as linseed stand oil, or as a mixture product containing not more than 15% unsaturated organic compounds. These oils provide excellent impregnation properties and protect surfaces from water and other chemicals.
(b) Sealers:
Sealers are a more effective method of protecting concrete surfaces compared to impregnation and hydrophobation. They achieve this by forming a film on the surface. The application of a larger quantity of impregnation agent or the use of suitable resins can be utilized to seal concrete surfaces. Commonly used plastics for concrete surface sealing include epoxy resins (EP), polyurethane resins (PU), polymethylmetacrylate resins (PMMA), and unsaturated polyester resins (UP). Additionally, sealers can serve as a primer for coatings.
(c) Coatings:
Coatings are often preferred over sealers for providing additional protection to concrete surfaces. This is because coatings offer greater resistance to the diffusion of internal moisture, which can help to prevent damage and deterioration over time. There are two main types of coatings used for concrete surfaces: thin coatings and thick coatings.
Thin coatings are designed to follow the contours of the concrete surface, even if it is uneven or irregular. This can be particularly useful for surfaces that have a lot of variation in texture or elevation. By conforming to the existing surface, thin coatings can provide a layer of protection without significantly altering the appearance or functionality of the concrete.
On the other hand, thick coatings are used to create a smoother and more uniform surface on top of the concrete. These coatings are typically 1mm or thicker, and are applied in order to create a more level surface. Thick coatings can be especially helpful for concrete surfaces that have significant unevenness or irregularities. By filling in gaps and smoothing out bumps, thick coatings can help to create a more visually appealing and functional surface.
A good coating materials should have following properties:
Concrete surfaces require protection against various factors, such as chemical attacks, temperature changes, abrasion, and cracking. To achieve this, coatings are commonly used, including epoxy resin, bituminous compound linseed oil, silicon preparation, rubber emulsion, or cement coating. Coatings should possess specific properties, such as good adhesion to the surface, sufficient tensile strength, elasticity, and abrasive resistance, as well as a comparable coefficient of thermal expansion to concrete.
Coatings can also serve to seal cracks in concrete structures, and high elasticity coating materials are typically used for this purpose. However, the effectiveness of the coating in bridging cracks is limited by its thickness, and debonding of the coating adjacent to the crack may be necessary. For cracks up to 0.2mm in width, thinner coatings may be sufficient, while larger cracks may require the insertion of a fiber material, such as textile fabrics, into the coating.
Recent developments in coating technology have led to the creation of two-component liquid sealers that can be sprayed onto the concrete surface. These sealers possess a low modulus of elasticity and improved elongation, allowing them to bridge larger cracks effectively. It is important to note that epoxy systems may undergo changes in their properties when exposed to variations in temperature and sunlight. Therefore, the selection of the appropriate coating material and application method is critical to ensure the longevity and effectiveness of concrete protection.
Methods of Using Surface Protection Materials
To prepare concrete surfaces for impregnation with surface protection materials, the first step is to assess the depth of impregnation required. Based on this assessment, the surface is then prepared accordingly. The impregnation liquid is applied to the concrete surface in an amount sufficient to fill any voids present, after which it can be spread using a brush, lambskin roller, or by spraying, depending on the situation. Depending on the porosity of the concrete surface, several applications may be required to achieve the desired level of impregnation. In cases where deeper penetration is needed, thin solvent-containing impregnation systems may be necessary for the first application.
For concrete surfaces that are expected to experience wear and tear, penetration depth of the surface protection material is particularly important. As such, impregnation protection systems are not suitable for surfaces that are likely to be damaged by abrasion, crack formation, or other forms of local disturbance. While resin impregnation may be effectively used on horizontal surfaces, hydrophobizing impregnations are not appropriate for such surfaces where water may collect. For this reason, hydrophobizing impregnation systems are best used on sloped or vertical surfaces where water can easily flow off.