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Polished concrete is strong, durable and low maintenance with that earthy texture of stone having a polish comparable to granite. Here is how to control your emotions.
It's just like traditional polished terrazzo that is very flat and poured like a special mix to create the finish more successful. Polished concrete floors may also look almost bumpy and have little or no aggregate showing. Flatness and polishing aren't necessarily exactly the same thing that is a good indicate clear up before acknowledging any project.
It is additional time and diamond wear to chop floors having a concrete grinder until they're flat. They are able to be either ground flat to completely expose the aggregate like terrazzo, or the aggregate could be partially exposed, or the concrete grinding can expose a maximum of the fine sands at the surface. It often takes skill and experience to manage the entire process of polished concrete floors and also the quality of the concreter's original laying jobs are additionally a contributing element in the quality of the finish. Where the aggregate is a feature special materials could be put into the wet concrete mix for example coloured pebbles, metals and glass to enhance the final appearance.
Most people are unaware there are ten to fifteen steps for polished concrete floors that takes quite a long time to complete and can be quite expensive.
Typically it takes many grinding passes to complete a highly polished floor however, there are other ways as explained later. The overall rule would be to double the amount diamond grit size underneath the concrete grinder for each pass so a contractor might start with very coarse, 16 or 32 grit size diamonds, then use 60 grit diamonds then 120, then start again with a 50 grit diamond resin pad instead of a metal segment. Using the resin pads the steps might be 100, then 200, 400, 800, 1500 and lastly 3000 grit. That would be ten separate grinding passes which does not count the 2 other essential steps.
Two more essential steps:
1. Hardening the top
Polished concrete floors will often have the top hardened with a chemical prior to the second, third or fourth grinding pass. The chemical soaks in to the floor to a couple millimeters (almost half an inch) and results in a chemical response to take place which makes the floor harder and simpler to shine to a high finish. These floors are very resilient and strong without getting a surface coating.
2. Filling holes
Following the first concrete grinder pass removes the top layer of concrete paste it'll expose countless tiny air holes. If these aren't filled before the hardening process then the final polished concrete floor can have these unsightly imperfections. The holes are often full of a polymer tile adhesive kind of product combined with either the grinding dust or cement powder that is hand scraped across the floor using a trowel. The preferred way to fill the holes is to spray the acrylic adhesive in front of the grinder so the diamonds mix it in to the holes using the grinding dust on the third or fourth pass at around 120 grit. This process is quicker and also the dust matches the color from the floor to cover the holes better than when utilizing cement powder.
Very flat or slightly bumpy polished?
Some floor grinder machines are made to produce a very flat floor by reducing the high spots while some other medication is designed to stick to the contours of the floor more. When the surface will be polished without necessarily exposing the aggregate then just the finer resin pads need to be used on a concrete grinder that enables for movement of the pads to allow them to stick to the contours of the surface. This can create a polished floor without showing the pattern and texture from the exposed aggregates inside the concrete which is faster and less costly. Hardening can nonetheless be a benefit to assist the durability from the surface and to create a final gloss.
Issues with exposed aggregate
Sometimes the conclusion of exposed aggregate can be uneven when the mixture of concrete was poured unevenly or finished off poorly. Boot marks or kneeling board marks can be displayed suddenly because they have pushed the aggregate down further which might require grinding down another two or three millimeters (quarter inch) which will cost more than was quoted. Grinding this far may not be what the customer wanted either therefore it could be a risk.
Single head or multiple head machines
Original terrazzo grinding ended with single head floor grinders until the manufacture of three-head planetary machines. Planetary implies that each head turns one direction while the turntable that houses the heads turns independently in either exactly the same direction or the opposite direction. Some grinders can vary the direction of both turntable and also the heads and some can vary the speed of each. There are also multiple head planetary machines with four or even more heads.
The planetary heads can stick to the contours much better than single or twin head grinders and are faster to make use of with less effort due to eliminating the necessity to physically move the grinder laterally or perhaps in a circular motion. Single head terrazzo grinders ought to be moved inside a circular motion to prevent grinding lips or shoulders.
Edging
As with wood floors the edges should be finished separately towards the main floor area because the large machines may bump and damage the walls if they are used too close. For that first grinding passes a nine inch angle grinder is used using a diamond wheel attached with a dust extraction shroud fitted to take away the dust. The sit-down-to-use edge grinders are more controllable than stand up grinders while kneel-to-use grinders have good control, but are exhausting.
Following the first couple of or three cuts another dust extraction shroud having a corner feature is used having a seven inch polisher or perhaps a five inch, multi speed grinder to polish with resin pads and obtain tight in to the corners.
Simple polished concrete floors "look"
The number of approaches for polishing concrete can be reduced by as much as 60% but still achieve a similar appearance by grinding after which coating with a clear sealer. The initial step would be to grind with 30/40 grit diamonds to expose the aggregate, then fill all of the small air holes as described above (in 10 to 15 steps....) before another grind with 60/80 grit or 80/100 grit diamonds.
This will create a smooth enough surface to coat with a sealer. Polyurethanes are very hard sealers with a high gloss and could be purchased as UV stable to prevent yellowing (usually double the price of non UV stable urethanes), clear epoxy sealers are not as smooth and can chalk and deteriorate if exposed to sunlight and acrylic sealers have a much shorter lifespan because of their poor resistance to wear. Two coats are necessary use a glossy level.
Different ways to achieve "polished concrete"
The first is to cut the ground with coarse diamonds until all of the high spots happen to be removed to make a flat floor after which make use of all from the 12 to 15 steps to eventually polish it or because it is sometimes called, hone it. This is actually the true polishing system.
An alternative of the aforementioned is to cut perhaps half of the height of the higher peaks by beginning with a medium coarse diamond grit and move through to polishing using a machine that can ride up and over small rises.
Another alternative way of producing a honed surface is to start with relatively fine diamonds and simply polish to top of the surface after hardening without removing much of the very best cement paste. It is easier to do this once the floor continues to be laid flat and smooth.
Lastly, a "polished look" can be obtained by grinding with coarse diamonds after which fine diamonds before coating over with a definite sealer.
Only truly polished floors will retain their gloss with little maintenance because all coatings scratch with wear and lose their high shine. Special buffing pads on a standard floor polisher which contain very fine diamonds may be used to maintain cleanliness and the high gloss levels of true polished concrete. Janitors can be supplied with these and keep the floors in great condition without special treatment.
Some hire companies provide the grinding equipment for do-it-yourself concrete polishing and also have all the pads for the purpose. It isn't really so economical though since the pads may be only half worn when you finish with respect to the area involved.
