We are often asked which is the appropriate method of choice for preparing resin coatings for concrete garage floors, concrete warehouse floors, aircraft hangars, restaurants, offices or showroom floors.
Many of you know the old saying that paint is "only on the surface". This was true years ago and it still holds true today. There's no point in buying an expensive resin and then applying this paint to an ill-prepared surface. Doing so is unlikely to yield good results.
So what are the common floor preparation methods? There are four (4) common methods of concrete floor preparation. The four methods are 1) power cleaning, 2) acid etching, 3) shot peening and 4) diamond grinding.
Power Washing/Pressure Spraying for Concrete Surface Preparation
Power washing or pressure spraying is exactly what it sounds like. An applicator rents or buys a pressure washer and uses high-pressure water to clean the concrete surface. Sometimes this method may use a cleaner/degreaser chemical to help remove oil and other contaminants. These can be applied to the floor individually with a bucket, and are usually in a solution of warm or hot water, and the problem areas are worked with a wire or stiff brush to help remove the contaminants. Sometimes, depending on the model of pressure sprayer used, these cleaners/degreasers are added to the reservoir on the power washer itself and mixed at the pressure sprayer head. When using these chemicals, it is very important to rinse the floor effectively with fresh clean water afterwards,
Power washing is an inexpensive way to prepare floors. Equipment is readily available for purchase and rental in most market areas. In most cases, these devices can be purchased for a few hundred dollars and rented for less than a hundred dollars per day. One disadvantage of this method is that if too much pressure is used, or the head of the sprinkler is too close to the concrete surface, the water can dig or gouge directly into the surface, ruining the smoothness of the surface and causing potential damage when the floor is painted. , areas of visual inconsistency draw attention. Another downside to this method is that the floor will be very wet afterwards, and if using solvent-based paint, the floor needs to dry effectively before painting. In warm, dry climates, like the deserts of the American Southwest, this can take 1 to 3 days to dry out. In cooler, more humid areas such as the US Midwest or Florida (high humidity), floors may take 5 days or more to dry sufficiently for solvent-based coatings.
In another article that we plan to publish in the near future, many floor coating contractors use water-based coatings, and while each has its pros and cons, this delay in drying time can be avoided if you use water-based coatings. This could be a driving factor as to why some floor Coating Applicators prefer water-based coatings, if they only have access to this less expensive water-based floor preparation equipment, and then have an incentive to avoid delays in waiting for the concrete substrate to dry. able to paint it.
Acid etching of concrete surface preparation
Another common method of preparing concrete surfaces for application of floor coatings or paints is acid etching. In this method, an acid, such as hydrochloric acid, a common pool chemical available in almost every market, is diluted with water and applied to the concrete floor. Let the diluted acid and water mixture sit on the floor for 30 to 60 minutes. During this time, the floor may "bubble" or "hiss" and appear to be cleaning the floor. What's really happening is that the diluted acid is breaking down dirt and other contaminants like oil, rubber residue from the tire, silicon and other chemicals like the armourall tire care products that people love to put on their tires to make them look like new .
After letting the acid solution sit on the floor for a period of time, usually less than an hour, the applicator is then usually moved across the floor with the ammonia and water solution. As the name suggests, acids have a pH below 7, which is neutral like water. Ammonia is an alkali, or alkaline, with a pH greater than 7. The purpose of the ammonia solution is to neutralize the acidic aqueous solution that has been applied and sits on top of it and has penetrated the concrete surface. For proper results the paint should be applied to a pH neutral substrate. If the paint is applied to an acidic (pH less than 7) or alkaline (pH greater than 7) surface, over time the acid or base can attack and destroy the paint, causing adhesion to fail, and/or appear random bubble.
When considering acid etching as a floor preparation method, remember that concrete is a porous substance. It has many air pockets and small holes throughout its depth. It's essentially a giant sponge, just one that we can't easily pick up and squeeze. This is the main disadvantage of acid etching. When the acidic water solution is applied to the floor, think about the structure of the sponge and mentally visualize the acidic water solution being absorbed into the sponge. When the ammonia solution is later applied on top of it to neutralize the acid solution, some of the acid that is at a lower depth in the concrete will not mix with the ammonia solution and therefore not be neutralized. Some of the better floor paint contractors are aware of this and have taken extra steps to minimize this problem. They may rinse the floor with water before applying the ammonia solution to help reduce the amount of acid that needs to be neutralized. This acidic runoff can bring other problems, such as discoloration and scratches or "burning" concrete downstream of the runoff. This acidic runoff can also damage or kill plants if they are in a downstream path, such as next to a driveway. Some cities and other jurisdictions have banned the method due to acid runoff and downstream wastewater pollution concerns. Even without this intermediate rinse (before using the ammonia solution), floor contactors using this method of floor preparation will need to rinse the floor very effectively with copious amounts of water afterwards,
Most, if not all, DIY big box hardware stores that sell do-it-yourself garage floor paint offer chemicals or suggest an acid etch prep route. Many people who have applied these DIY garage floors and initially thought they had saved the cost of floor contactors in the floor paint business later found out, usually after a year or two of application, that their beautiful floor is now appearing in random patterns all over the floor. Bubble. We've spoken to many of these people over the years. They are confused as to why their floors still look fine in some areas, but randomly have these bubbles or adhesion/delamination issues in other areas (see photo above). Our better experience and knowledge tells us that this random bubbling of their floors is from leftover, unneutralized acid. Remember, concrete is a sponge. This means it will draw in and absorb moisture around the slab and the surrounding ground. As the rain and snow arrive (and melt), this moisture can be drawn into the concrete slab. As the temperature rises, moisture will rise through the concrete and migrate to the surface. The unneutralized acid remains trapped in the concrete pores, underneath the now dried floor coating that was applied 1, 2 or more years ago, is pushed up by this moisture and eventually contacts the underlying layer of the dried coating. Over time, this unneutralized acid can attack these parts of these dry floor coatings, and the pores in these areas have become trapped by the acid, resulting in what now appears to be a random bubbling pattern. This is the main disadvantage of acid etching.
In our experience, only very good and experienced floor coating contractors can understand this reality and take the extra effort necessary to try to overcome and minimize this problem. This is why we tend not to recommend this type of floor preparation. Another disadvantage of this coating is the smell of ammonia. Ammonia is a very, very strong smell and, to most people, a bad smell. Appropriate respirator should be used. It's also worth noting that by the time the contractor finishes this method of floor preparation, the floor will be wet or damp. Like the comments above in the power wash section, if using solvent based paints, you need to allow the floor enough time to dry effectively. Contractors who tend to use this method of floor coating tend to use water-based paints for this reason and to avoid drying time,
Shot blasting and scarifying machines for concrete surface preparation
Shot peening was a method that was commonly used about 10 or more years ago, but has quickly become less common. Shot peening is exactly what it sounds like. A machine is filled with small steel balls. These balls are shot at high speeds under pressure against the concrete. When the balls hit the concrete, they actually blast a layer of the top surface into pieces, which then crumble and can be swept away. These machines left a rather rough outline. This rougher profile is acceptable if a thicker resin such as epoxy is used, which will self-level when dry and produce a smooth surface. However, if using a newer resin technology such as polyaspartic polyurea, which is designed for thinner layers, the rougher surface left by the shot blaster may not be smoothed by the thinner polyurea , resulting in a floor surface that is not smooth and therefore may be undesirable. As these newer resin technologies become more common as they offer many desirable and improved dry film performance characteristics over resins such as epoxies, shot peening machines are used less and less in this field .
A scarifier is similar to a shot blasting machine. These machines generally do not use steel balls shot into the top surface of the concrete, but instead have multiple blades arranged vertically on a horizontally rotating axis. The blades are staggered and designed in such a way that they provide a very aggressive cutting action on the concrete surface. These machines often create so-called "corn rows", valleys and peaks in the floor surface after the machine passes. The valleys are where the blades dig into the concrete, and the peaks are the spaces between the blade pitches. Contractors usually need multiple passes with this type of machine to knock down the "corn rows" and often need to use another floor preparation machine to smooth and reduce the roughness or contours of the floor because the scarifier, when used alone, Usually leaves a floor that is too rough and uneven to paint. While these machines are useful, trying to remove previously applied coatings is very difficult and difficult to remove. Even this advantage has been largely negated in recent years with improvements in the shape and design of the diamond cutting blades used in concrete diamond grinding machines.
Diamond Grinding for Concrete Surface Preparation
A newer and in our opinion one of the current appropriate practices for concrete floor preparation is diamond grinding. Diamond grinding uses specially designed machines that allow interchangeable and replaceable diamond-inserted grinding tool bits to be inserted into the rotating head of the machine in contact with the concrete floor. These machines provide a dry, non-aqueous, non-chemical method of removing thin layers of concrete and the dirt and contaminants within that layer. Many of these machines are hooked up to an accompanying concrete vacuum that picks up the concrete dust created in the process. Using these machines usually results in a concrete surface that looks like new, and is clean and free of contaminants. Dirt, oil stains and silicones from car care products are often ground off the floor and the resulting dust is vacuumed away. There is one thing to pay attention to here. If dealing with heavy oil or other chemical stains, other methods may still be necessary, such as using a cleaner degreaser before sanding to loosen and help lift oily stains on the floor. Concrete diamond Grinders seem to come in all sizes and shapes these days.
A growing number of companies manufacture diamond grinding machines and offer them in many different sizes, shapes and weights. Having a machine good enough for the job is an important consideration. There is also a machine with a motor that can provide enough power for the diamond grinding head is also a factor that needs to be considered. Many machines are electric and require more power than the 110 volts common in nearly every modern home. For this reason, many contractors who use these machines also own and bring their own generators to the job site to generate the higher voltage and power required to run these machines. Some of these machines are even gas powered instead of electric, and some newer ones are now even propane powered.
We think better machines have counter-rotating heads. The outer head usually rotates in one direction. Connected to this head is another head with 2, 3 or more smaller heads that spin in opposite directions. Attached to these smaller heads will be several individual diamond bits. Diamond bits come in different "grit sizes," such as sandpaper, that allow the user to adjust the intensity of the grind to the concrete of the job site. For softer concrete, use a less aggressive drill. For harder concrete, a more aggressive drill is usually used. Diamond bits also come in different shapes, which provide different cutting performance. Smaller, simpler diamond Grinders can cost several thousand dollars. Larger, more complex machines can cost well over $10,000 each.
When using a diamond Grinder, there is no extra thought or delay in waiting for the floor to dry sufficiently before applying solvent-based paint to the floor. The obvious advantage of using a diamond Grinder is that this method may provide you with the right opportunity to remove dirt, contaminants and other obstacles to adhesion. But it does come at a price, and may be the more expensive option. This is a function of the cost of the machine and the replaceable worn diamond bits that need to be replaced periodically. If your floor coating contactor does offer this type of floor prep then we take that as a good sign that they are likely knowledgeable and committed to the industry, including a commitment to having better tools for better floors Prepare.
Conclusions on Concrete Surface Preparation Methods
So, what's a better way to prepare concrete floors? The answer is that it depends on your job and budget. A solid and experienced floor coating contractor should have several methods that they are experienced in using and should be able to offer you more than one method and be able to discuss why they suggest the pros and cons of their method. Probably the most common method of floor preparation is acid etching. Note that this is almost certainly the cheapest way to go and does enable many newcomers into the floor coating business. If dealing with someone who suggests this method, we recommend that you take the time to find out how long they have been in business, if they use other floor prep methods and why they chose or suggested this method for your job. There may be good reasons why acid etching may be the appropriate method for a given job and/or your budget. However, make this decision with purpose and knowledge. There's no valid reason that this is cheap and they don't have or can't afford a diamond Grinder.
