Why is concrete surface preparation important?
Services: Surface Preparation
Concrete surface preparation is essential for ensuring an effective application of coatings or linings. Meticulously preparing the concrete surface will improve adhesive bonding to the substrate, increase durability and longevity, resulting in minimised maintenance and mitigate future issues such as surface defects.
Key steps in concrete surface preparation:
Cleaning and removal of existing coatings – To achieve proper adhesion of the coating or lining the substrate must be porous and free from any contaminants and existing coatings. Typically, this is done via mechanical methods such as shot blasting, grinding or scarifying..
Scarifying – Scarifying is a process that cuts into the concrete surface, removing up to 5mm in one pass. It is usually the preferred method for removing existing resin-based coatings or for creating very rough surfaces for heavy-duty coatings. Scarifying is often followed by shot blasting to remove any chips or cracks in the concrete.
Shot blasting – Shot blasting is a process of firing metal shot at the concrete wearing away the surface and removing any coating, oils or debris. often used for heavy-duty surface preparation and in expansive areas such as on roads or airport runways where a coarser profile is required.
Grinding – Grinding is typically used to level and refine a surface to a desired smoothness, such as in commercial and industrial spaces to create a polished concrete floor.
Repairing cracks and surface defects – To create a smooth and level surface epoxy or polyurethane fillers should be used to repair profile cracks, joints and surface imperfections.
Moisture testing (RH levels) – Concrete floors that are high in moisture vapour transmission rates can result in a number of issues including ineffective adhesion of the coating, mold and even failure of the entire floor system. It is imperative that moisture testing is undertaken before a coating is applied. The most common testing methods are the calcium test or the relative humidity test. If moisture levels are too high a moisture barrier such as waterproof membrane or polyurethane sheeting may need to be applied.
pH testing – Freshly poured concrete has a pH level of around 12 due to the formation of calcium hydroxide when during the hydration process. When the calcium hydroxide reacts with the carbon dioxide in the air, calcium carbonate is formed, this then reduces the pH levels at the surface of the concrete. If the concrete is too alkaline or acidic it will prevent the adhesive from bonding.
Application of primers or sealants – Primers can help to enhance the bond between the concrete and the new coating or lining and are an absolute necessity prior to the application of paint to prevent cracking or peeling. Failure to properly prepare concrete will result in coating issues, peeling paint and can even cause cracks and structural damage, which would require costly repairs. Concrete surface preparation is therefore an integral part of any concrete coating, lining or flooring installation processes.