Concrete is a widely used construction material known for its durability and strength. However, its susceptibility to environmental factors such as moisture, chemicals, and abrasion necessitates effective surface protection methods to ensure longevity and structural integrity. These surface protection techniques of concrete not only enhance the aesthetic appeal of concrete structures but also contribute significantly to their overall performance and resistance to deterioration. In this context, various surface protection methods have been developed and employed to safeguard concrete surfaces from the detrimental effects of weathering, corrosion, and other forms of damage. From traditional coatings to advanced technologies, the evolution of concrete protection reflects the ongoing quest to enhance the material's resilience in diverse settings.

This blog shall take readers through the different protection methods of concrete surface. This topic is important for all the upcoming civil engineering examinations, including SSC JE CE and RRB JE Civil.

Objectives of Surface Protection

• Prevent ingress of water, chlorides, carbon dioxide, and harmful chemicals
• Reduce carbonation and chloride-induced corrosion
• Enhance abrasion and chemical resistance
• Improve aesthetic appeal and maintain surface integrity
• Prolong structural life and reduce maintenance costs

Surface Protection Methods of Concrete

The following measures can be implemented to minimise or halt damage to concrete structures:

• Hydrophobation: Application of hydrophobic agents to mitigate water penetration into concrete pores.
• Painting: Utilising paint as a protective layer to shield the concrete surface from environmental factors.
• Impregnation: Employing a system that prevents capillary absorption of water by the concrete, achieved through hydrophobation of pores or narrowing of capillary ducts by film formation on walls.
• Sealers: Application of sealers to create a closed thin film on the concrete surface, enhancing protection against external elements.
• Coating: Implementing protective coatings to shield concrete structures from various forms of damage.

The efficacy of surface protection for concrete structures increases in the order presented above. Each method varies in the process used to achieve concrete surface protection. In the impregnation system, protection is attained by inhibiting capillary water absorption, either through hydrophobation of pores or by narrowing capillary ducts through film formation on walls. Sealers and coatings contribute to a higher level of surface protection by forming a closed thin film on the concrete surface.

Preserving the integrity of concrete structural elements is imperative to shield them from environmental hazards. The vulnerability to damage, whether from the permeation of water and moisture leading to reinforcement corrosion or exposure to chemical aggressors, particularly in structures near coastal areas, underscores the need for comprehensive surface protection. Thus, safeguarding concrete members becomes essential in averting potential deterioration and ensuring the longevity of structures.

Materials used for Concrete Surface Protection

Below are some examples of materials used for different surface protection methods of concrete.

(a) For Impregnation and Hydrophobation Methods

(i) Silicon organic impregnation materials:

• Siliconates
• Silanes
• Siloxanes
• Silicon resins

(ii) Resins:

• Polymethylmetacrylates (PMMA)
• Epoxy resins

(iii) Oils:

Linseed oil (used in boiled form, linseed stand oil, or in mixture products with not more than 15% unsaturated organic compounds)

(b) Sealers

In contrast to impregnation and hydrophobation, sealers offer enhanced concrete surface protection by forming a film on the surface. Sealing is achieved by increasing the applied quantity of an impregnation agent that tends to form a film or by selecting suitable resins. 

Commonly used plastics for sealing concrete surfaces include:

• Epoxy resins (EP)
• Polyurethane resins (PU)
• Polymethylmetacrylate resins (PMMA)
• Unsaturated polyester resins (UP)
• Sealers can also function as primers for coatings.

(c) Coatings

Coatings provide additional protection compared to sealers, with increased resistance to internal moisture diffusion. Two types of coatings are employed: thin coatings, which conform to uneven concrete surfaces, and thick coatings, used to create a smooth surface with a thickness of 1mm or more. Ideal coating materials should possess:

• Resistance against chemical attacks
• Resistance against temperature changes
• Good adhesion to the surface
• Sufficient tensile strength and elasticity
• Adequate abrasive resistance
• Capability to bridge cracks
• Coefficient of thermal expansion compared to that of concrete

Suitable coatings for concrete surfaces include epoxy resin, bituminous compound linseed oil, silicon preparation, rubber emulsion, or even basic cement coatings. Coatings are also employed for sealing cracks in concrete structures, with high elasticity coating materials used for this purpose. Recent developments include two-component liquid sealers that can be sprayed onto concrete surfaces, with the ability to bridge larger cracks due to their low modulus of elasticity and improved elongation.

Classification of Surface Protection Methods

According to EN 1504-2 (European standard for concrete repair), surface protection methods are categorized into:

1. Hydrophobic Impregnation
2. Impregnation
3. Coating

Each method differs in its depth of penetration, film formation, and functionality.

Hydrophobic Impregnation

• Uses water-repellent chemicals (e.g., silanes, siloxanes)
• Penetrates the concrete pores without blocking them

Does not form a film on the surface

• Advantages:
  • Preserves vapor permeability
  • Prevents water and salt ingress
  • Minimal aesthetic change
• Limitations:
  • Limited protection against
  • mechanical or UV damage
  • May need reapplication over time
• Applications:
  • Bridge decks, facades, parking
  • structures, marine environments

Impregnation

• Application of reactive or non-reactive liquids that penetrate into the surface and modify its properties.
• Can strengthen the surface and reduce porosity
• Materials Used: Silicates, silanes, fluoropolymers, polymer-based resins
• Advantages
  • Deep penetration ensures longer protection
  • Improves hardness and resistance to abrasion
• Limitations
  • Doesn’t form a barrier against surface abrasio
  • Effectiveness depends on porosity of concrete
• Applications: Industrial floors, warehouses, water treatment plants

Surface Coating

• Involves applying a film-forming layer on the surface
• Acts as a physical barrier against environmental agents

Comparison between Type of Surface Protection

The choice of surface protection method depends on the depth of penetration, barrier properties, and compatibility with environmental conditions. The table below highlights key differences among major protection techniques to guide optimal selection.

This blog explained the Surface protection methods of concrete. This topic is important for your upcoming exams. If you are preparing for State and Central level Civil examinations and other diploma-level exams, get enrolled in AE/JE Civil Coaching on the Testbook App.

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