Surface preparation is an important part of concrete repair jobs. It helps to develop the correct bond with the new concrete. There are a number of methods used for surface preparation and chasing. Some repair situations demand the only surface roughening, some need concrete surface cleaning while others need the removal of the layer of damaged concrete. Every type of repairs needs a distinct kind of surface preparation. However, the concrete surface shouldn’t be too rough, too smooth or too irregular. Let’s have a quick look at different types of surface preparation techniques.• Chemical cleaning – Tri-sodium phosphate, detergents, and different other cleaners are often used for surface preparation. Nevertheless, they are not good for surface preparation in terms of concrete repairs. Solvents are also not used because they might dissolve contaminants. The contaminant is then carried to the deep into the concrete. And concrete coating is not recommended for this reason. However, the cleaning process is used under special conditions with the application of specific coatings.
• Mechanical preparation – With this technique, a thin concrete layer is removed from the surface to obtain different surfaces. Nevertheless, the type of surface depends on the removal equipment. Equipment used in mechanical preparation may include tools such as scrabblers, breakers, scarifiers, and grinders.
• Acid etching – This method of surface preparation and chasing is used for the removal of dirt from the surface. This also removes laitance. Acid applied on the surface can remove cement paste of a significant amount. And that leaves a rough surface with better bond strength. Acid penetrates concrete surface through the cracks. This often promotes corrosion of underlying reinforcing steel. This can damage the paste of the remaining concrete. Better you don’t use acid for every occasion. Rather use it on concrete while other surface preparation alternatives can’t be applied.
• Rotomilling – This is a large scarifier on steroids. It is driven with teeth mounted to drum rather than washers. These teeth can cause a fracture to the concrete to dust and chips. It can create deep grooving and striations. Rotomiller is used on horizontal surfaces only.
• Abrasive preparation – Be it moist or dry, abrasive blasting propels abrasive in a flow of compressed air. This makes abrasive particles to penetrate the substance. It also dislodges the fragments of mortar. As a result, an eroding effect takes place. This method can remove surface contaminants, coatings, unsound concrete, and adhesive films. It also imparts a profiled surface. Equipment used for abrasive preparation may include shotblasters, sandblasters, and high-pressure water blasters. Abrasive preparation is followed by air or water blasting, vacuuming or some other processes. The profile number is determined by surface roughness needed for different overlay applications. It is defined by sandpaper grit size as well.
• Needle scaling – Needle scalers are used for removing efflorescence as well as other brittle encrustations. The impacts of needle scaling create a cratered surface profile.
Different methods of surface preparation may include chemical cleaning, mechanical preparation, acid etching. The methods also include rotomilling, abrasive preparation, and needle scaling. Use any of them as per your requirements.