What is Concrete coating?
Concrete coating is a technique used to prevent the contact with, and ingress of, water and aggressive substances. Surface coatings can be composed of a wide variety of materials such as acrylics, epoxies, urethanes etc, and are engineered to form a robust protective barrier.
By mitigating effects of aggressive environmental conditions, concrete coatings can not only effectively prevent the most common forms of concrete deterioration but also provide an array of decorative finishes, transforming concrete surfaces into visually appealing structures with increased longevity and reduced maintenance needs.
What is Concrete coating used for?
Concrete coating prevents or mitigates deterioration processes involving ingress through or attack of the concrete surface such as carbonation, chloride contamination, abrasion-erosion, freeze-thaw, leaching, External Sulphate Attack (ESA), acid attack, biological deterioration, reinforcement corrosion and other processes in the presence of cracks due to shrinkage or thermal gradients.
When deterioration process have already induced damage to the concrete and its reinforcement previous concrete replacement or the application of other repair methods adequate to mitigate the causes of deterioration are required .
Only defects inducing surface level concrete damage (pop-outs, efflorescence, scaling, spalling, bug holes, Early age cracks, discoloration and inorganic/organic and/or biologic contamination) could exclude previous concrete repair with the application of this treatment.
How does concrete coating work?
This treatment works by forming a continuous film on the concrete surface, typically ranging in thickness from 100 micrometres to 5 mm. A repair involving coating the surface will always change the aesthetic appearance of the repaired structure, provided that the concrete was not coated before.
Concrete coatings chemically and mechanically bond to the concrete surface, ensuring the longevity and effectiveness of the protective layer. The specific bonding process varies with the type of coating used.
Epoxy coatings form a strong mechanical bond to concrete, penetrating the surface pores to create a hard, durable layer that is highly resistant to chemical attack, moisture ingress, and physical abrasion. However, traditional epoxies may be vulnerable to UV radiation, which can lead to yellowing or degradation over time.
Polyurethane and polyaspartic coatings are known for their flexibility and UV resistance. These coatings bond well to concrete and are particularly resistant to impacts, abrasions, and most types of chemical spills. They are also less likely to yellow under sunlight compared to epoxies.
Acrylic sealers provide a less durable bond compared to epoxies or polyurethanes but are breathable and allow for moisture vapor to escape from the concrete, preventing blushing and delamination
The resistance of concrete coatings to degradation largely depends on their chemical composition and application thickness. For instance, thicker applications of high-performance epoxies or polyurethanes can provide superior resistance to harsh chemicals, heavy traffic, and extreme weather conditions. Conversely, thinner applications or less durable materials like acrylic may offer less protection over time.
Selecting the correct coating involves assessing the specific needs of the concrete surface, including the environmental conditions it will be exposed to (e.g., UV exposure, aggressive soil conditions, chemical spills, mechanical wear) and the desired aesthetic outcome. Factors such as the coating's permeability, chemical resistance, UV stability, and flexibility must be considered to ensure the selected coating will provide effective and long-lasting protection.
How do I repair concrete structures using concrete coating?
To coat concrete elements according to BS EN 1504 the following steps should be followed:
Thoroughly assess the concrete surface for any damage, contamination, or irregularities. This involves visual inspection and possibly testing for strength and adhesion suitability.
Clean the surface to remove loose particles, dirt, oil, or existing coatings that may hinder adhesion. Methods can include high-pressure water jetting, abrasive blasting, or mechanical cleaning, ensuring a sound and clean substrate is achieved for coating application.
Repair any structural damage through concrete replacement or other repair mechanisms.
Level and smooth surface irregularities and repair cracks to ensure a uniform surface that will not negatively affect the coating application or performance.
Some coating systems require a primer to help them bond to the concrete surface or block out moisture; apply this as per manufacturer’s instructions.
Apply the selected concrete coating system in accordance with the manufacturer's specifications and BS EN 1504 requirements. This could involve brush, roller, or spray application techniques.
Multiple coats may be required to achieve the desired thickness and protection level.
Ensure that each coat is allowed to dry or cure as specified before applying the next layer.
Conduct quality control checks throughout to ensure the coating is applied evenly and achieves the required thickness, adhesion, and performance characteristics without defects.
Allow the coating to cure fully according to the product specifications. Curing time can vary based on temperature, humidity, and the specific coating used.
What equipment and expertise are required for coating of concrete structures?
Coating of concrete surfaces requires some or all of the following equipment:
High-pressure water jetting, abrasive blasting equipment, or mechanical cleaning tools for surface preparation.
Coating materials such as acrylics or epoxies.
Brushes, rollers, sprayers, and other application tools suitable for the chosen coating system.
Thickness gauges, adhesion testers, and inspection tools for quality control.
Suitable PPE for handlers and applicators to ensure safety during the coating process.
Expertise is also required in surface preparation, repair techniques, and coating application and relevant knowledge in selecting and applying the appropriate concrete coating systems for specific environmental conditions and service requirements is vital.
What are the advantages of repairing concrete structures using concrete coating?
Concrete coatings create a barrier on the surface, shielding concrete from moisture, chemicals, oil, stains, and physical damage like cracks and pitting. This protective layer helps to extend the service life of the structure by preventing deterioration caused by environmental exposure.
Coatings can significantly improve the appearance of concrete surfaces, offering a wide range of finishes, colors, and textures. This makes it possible to rejuvenate older structures or align new constructions with architectural aesthetics.
Coatings provide excellent resistance against the penetration and attack of carbon dioxide, water, sulphates, acids and chloride ions, protecting structures from adverse environments.
Some concrete coatings offer additional benefits such as slip-resistant surfaces, enhancing safety in high-traffic or wet areas. This feature is particularly beneficial in commercial spaces, industrial facilities, and outdoor walkways, where slip hazards need to be minimized.
Coatings can provide specialized, bespoke resistance against specific acids, alkalis, solvents, and other chemicals, making them ideal for industrial environments where spillages might occur. This chemical barrier helps prevent the corrosive effects these substances can have on concrete structures.
Many modern concrete coatings are designed to resist ultraviolet (UV) light degradation, helping to maintain the color and integrity of the coating in outdoor applications exposed to sunlight.
What are the disadvantages of repairing concrete structures using concrete coating?
The initial cost of specialised, high-quality coatings if they are required and the professional application process can be higher compared to other protective measures. The need for surface preparation, primer application, and possibly multiple coating layers requires skilled labor and time.
Even with a protective coating, surfaces can become scratched or worn, especially in areas with heavy equipment or traffic. These imperfections may require touch-ups or a complete reapplication of the coating to maintain its protective qualities.
While concrete coatings enhance durability, they may not match the original service life of the structure. Frequent maintenance or reapplication of coatings might be required over time to maintain protective efficacy.
If the concrete has already experienced significant deterioration, simply applying a coating might not be sufficient. In such cases, prior repairs, such as concrete replacement, may be necessary to address the underlying damage before coating application can be effective.
What are the limitations of repairing concrete structures using concrete coating?
The application of organic coatings is not recommended in environments with very low temperatures or high humidity. These conditions can impede the curing and drying of the coating film, leading to suboptimal results and potential failure of the coating system.
Moisture can become trapped beneath the coated layer, potentially leading to adhesion failures. It's crucial to ensure the concrete is adequately dried and prepared before applying coatings to mitigate this risk.
Concrete must be at least 2 months old before applying to allow the concrete to cure adequately, ensuring better adhesion and performance of the coating treatment.
Not all coatings are compatible with every type of concrete or existing surface treatment, which can limit the choice of coatings for certain projects. Incompatibility may lead to poor adhesion, delamination, or other failures, necessitating thorough compatibility testing before application.
Some coatings, especially those based on solvents, may release volatile organic compounds (VOCs) during application and curing, posing environmental and health risks. This necessitates adequate ventilation and protective measures during application and highlights the importance of selecting low-VOC or VOC-free options when possible.
Ancillary information
Service disruption: No
Preliminary works: Yes
Posterior works: Yes
Time consumption: Low
Cost: Low
References and further information