Choose the Right Surface Preparation Method to Avoid Flooring Failures
by Steve Heskett - Technical Sales Representative
Even the best coatings are destined for failure if not applied correctly, as coating performance is directly impacted by surface preparation and absorption rate. Integrity and service will be significantly compromised if the concrete substrate is improperly prepared. Choosing the correct method of surface preparation ensures coating adhesion to the substrate and prolongs the life of the coating system.
Is the Surface a Candidate for Coatings?
The first step in ensuring the flooring is installed correctly rests in determining whether the surface is a candidate for coatings in the first place. Testing and a solid inspection of the substrate should be a first priority. A simple water test can determine if the floor surface has been covered with sealers, contaminants, curing compounds, oil, grease or any other materials. More specifically, water will bead on the surface if the substrate is too dense to accept a penetrating primer. If this is the case, acid etching is not an acceptable means of floor preparation. Instead, the surface will need a shot-blast or diamond grind.
Also, testing for moisture and relative humidity (RH) levels is a practice every contractor should undertake prior to the installation of an encapsulating-type coating. The reasoning behind this practice is to prevent moisture drive, which once sealed has nowhere to go but horizontal between the coating and the slab, ultimately causing coating failure.
Three Methods of Surface Preparation
Following an initial inspection and confirmation that the surface is a good candidate for coating, along with the specific needs for preparation to ensure a long-lasting and solidly preforming system, it’s time to begin thorough preparation of the surface. There are several methods available, which can be used to clean, prepare and profile a sound concrete substrate or removing an existing coating as it needs the pours opened up for coating adhesion. If unsure which route to take, contact your Arizona Polymer Flooring representative before beginning work.
- Shot Blasting: The steel shot-blasting process includes steel shot centrifugally propelled at a high velocity onto the surface to clear it of any debris or coatings. A machine that recovers and separates dust and reusable shot is used and produces very little airborne dust or contaminants, which is especially helpful in confined spaces. Moving along in long, straight passes will produce a profile from a light sandpaper finish to a rough finish depending on the speed of the machine and size of shot used. Although shot blasting is a great way of preparing the surface to be coated and will remove any loose or spalling concrete, it takes a skilled technician to do it correctly.
- Diamond Grinding: Diamond grinding is an excellent way of preparing a concrete surface and becoming increasingly more popular as machines get bigger and better. With diamond grinding, which involves the rotation of one or multiple abrading disks or stones fitted with diamond cutting grain, can produce a profile anywhere from a 60 -grit sandpaper finish to a highly polished concrete floor, essentially, a surface to meet the preparation needs for virtually any coating. Grinding can also be used to effectively level an uneven surface. Using the correct grit diamond is an essential aspect of grinding. As a rule of thumb, hard concrete needs soft diamonds, while soft concrete requires hard diamond cutting grains.
When grinding a concrete surface, it’s vital to overlap and walk the grinder to avoid track marks on the surface. Walking is the side-to-side motion always keeping the grinder moving to prevent over-processing a specific area.
Most finish profiles for coating adhesion require a surface that feels similar to 60-80 grit sandpaper with the open pores. This can be achieved by using a minimum of 30-grit diamond cutting grain for good coating penetration. Anything higher may keep the penetrating primer from absorbing into the substrate, ultimately causing coating failure.
- Scarifying: Using the scarifying process includes employing a machine with the rotary action of cutters, which are essentially toothed washers impacting the surface at a right angle, removing the top layer up to a ¼-inch to fracture or pulverize the substrate. When used for coating removal, scarifying can be a very effective way of surface preparation, although this method would not be recommended for a thin film coating system.
There are many factors that affect the life and durability of a flooring system, especially the proper preparation of the surface. Knowing how your floor has been affected by contaminants or prior coatings and understanding the appropriate preparation are vital to ensuring your system stands up to years of use.