Polished concrete is concrete that has been treated with a chemical densifier and ground with progressively finer grinding tools. The grinding tools are usually progressive grits of diamond grinding cup wheels and diamond polishing pads. Typically, concrete is not considered polished before 400 grit, and it is normally finished to either the 800, 1500, or 3000 grit level. Stains and dyes are often applied to enhance polished concrete as well as other options such as scoring, creating radial lines, grids, bands, borders, and other designs.
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Polished concrete is considered a good sustainable design flooring option because it makes use of the materials already present. Most modern buildings are built on a concrete slab; polishing the exposed concrete eliminates the energy and material consumed by applying a floor covering. It is something to consider when building or modernizing towards a more green solution.
Polished concrete floors are low-maintenance, as they are more durable and easier to clean than many flooring options. Its relatively high coefficient of friction can make it non-slippery. Polished concrete reduces dust mite and allergen problems, and does not support mould growth. Anecdotal evidence suggests highly reflective polished concrete reduces lighting needs and improves natural lighting, but as of yet there has not been a study to confirm this. Polished concrete flooring is hard wearing and will not chip or dent like softer surfaces such as timber and mopping with warm soapy water once a week is the only maintenance required.
LEED 2009 standards contain guidelines for using polished concrete flooring to qualify for LEED credits.
In simple terms, the process of polishing concrete is similar to sanding wood. Heavy-duty polishing machines, for example concrete grinder, are used to gradually grind down surfaces to the desired degree of shine and smoothness. The closest equivalent example would be polished granite or marble.
Polished concrete floor installation is categorised into two types: new floors, and retrofit floors.
New floors require less work resulting in lower costs, but there are a few things to be aware of before a new concrete floor can be polished. Firstly the slab can contain a decorative aggregate. The two most common aggregates are river stone, granite, and black basalt mix, however the aggregate can be almost anything. The finished surface of the concrete will need to be finished to a high standard to facilitate the polishing process. During the finishing phase any decorative aggregates such as seashells or car parts can be dropped into the surface of the concrete. Builder needs to be aware as early as possible if the concrete is to be polished so that the final finish is of the best quality.
Retrofit floors can be done in two ways. The existing floor slab can be cut or sanded and the natural aggregate will be the feature or a topping slab with a minimum thickness of 50 mm can be added on top of the existing slab.
Process involved in polishing concrete: