Updated on 3/5/2021
More retail, restaurant, warehouse, fleet management, and office facilities are opting for polished concrete flooring as an alternative to marble, granite, tile, VCT, wood, linoleum, or coated concrete. Even homeowners are catching on to the appeal of these smooth, high-luster floors, which can be stained to replicate the look of polished stone.
Considering Polished Concrete Floor or looking for a trustable contractor to provide Concrete Polishing Services? Here is your must-read POLISHED CONCRETE COMPLETE GUIDE.
POLISHED CONCRETE: THE COMPLETE GUIDE
1. Polished Concrete Fundamentals
What is Polished Concrete?
Polished concrete is concrete that has been processed through a series of mechanically ground “polishing/grinding” steps utilizing professional equipment designed for concrete polishing. This process also includes the use of a concrete densifier/hardener which penetrates into the concrete and creates a chemical reaction to help harden and dustproof the surface. During concrete polishing, the surface is processed through a series of steps (in general a minimum of 6-8 grinding steps of processing is considered polished concrete) utilizing progressively finer grinding tools. The grinding tools are progressive grits of industrial diamonds in a bonded material such as metal/hybrid/resin often referred to as diamond polishing pads.
Concrete is not considered well polished before 800 grit, and it is normally finished to either the 800, 1500, or 3000 grit level. Dyes designed for concrete polishing are often applied to add color to polished concrete as well as other options such as scoring, creating radial lines, grids, bands, borders, and other designs.
2. Why Polished Concrete
Simply put, a polished concrete floor system transforms a porous concrete floor into a tightened surface, dense enough to keep water, oil, and other contaminants from penetrating the surface.
3. Concrete Polishing Process
Currently, the industry breaks down the process of polished concrete into grinding and polishing. Some simply use the word “polishing” for the whole process. Each phase is then broken down into multiple steps, consisting of consecutively finer grit abrasives. Every step is refined to its purest possible form on a microscopic level from one progressively finer abrasive to the next until the desired level of ‘polishing’ is achieved.
During the processes, a densifier/hardener is applied that is absorbed into the concrete creating a chemical reaction that makes the concrete more dense and hard.
Recent advances in polishing equipment and techniques have allowed concrete to be ground, honed, and polished to a high polish with clarity of reflection and depth. The process is performed with large planetary head machines where the main head rotates in one direction and smaller satellite heads spin in the opposite direction.
The result is a beautiful, durable and efficient surface that eliminates the need for carpets or tile that requires expensive replacement, maintenance, and use of harsh cleaning chemicals.
Maximum “clarity of reflection” and “durability” of the surface is achieved by strictly following the procedures, with which a contractor executes the grit sequence. Even if the desired result is not clarity of reflection or a glass-like finish, each grit must be fully refined to obtain the maximum durability and a clean crisp look of the finished surface. It is imperative not to skip grits in the processing sequence.
The process of concrete polishing is very technical in nature and requires real craftsmanship.
4. Options & Choices
There are many options available for different Polished Concrete designs. Different Aggregate Exposure, different Clarity of Reflection, and different dyed Color will change the visual aspects and physical characteristics of your polished concrete floor significantly. So know your options and potential outcomes before you make choices.
4.1 Aggregate Exposure
The Aggregate Exposure of the floor represents the amount of aggregate that will be exposed at the surface. Consider the needs and functions of your building when deciding whether aggregate exposure is appropriate. Grinding the concrete to expose aggregate may be considered attractive for a commercial space, but it can be unsuitable for a manufacturing space where dropped fasteners need to be easily spotted on the floor.
Below are the four most common aggregate exposure levels for polished concrete floor finishes.
Light Sand / Cream Finish
The light sand exposure is a ground and polished surface, typically exposing only the sand particles in the concrete floor. This finish is considered a “creamy looking” surface and is the most popular choice for Architectural Ground & Polished floors.
Salt & Pepper Finish
The Salt & Pepper exposure is a ground and polished surface, typically exposing a spattering of fine aggregate in the concrete floor. This finish is most often chosen to give the appearance of an aged surface. Approximate surface cut depth 1/16 inch.
Medium Aggregate Finish
Medium Aggregate exposure typically exposes the greatest amount of medium aggregate in the concrete floor with little or no large aggregate exposure at random locations. Approximate surface cut depth 1/8 inch.
Large Aggregate Finish
Large Aggregate exposure is a more heavily “cut” surface, typically exposing the greatest amount of larger aggregate in the concrete floor. The finish is the most often chosen when the substrate has been seeded with custom aggregate. On some floors including restoration of older concrete, there may be limitations to how deeply the floor can be cut. Approximate surface cut depth 1/4 inch.
Some property owners prefer a flat gray finish, and others would like to see some exposed aggregate in their finished concrete floors. Informing your contractor as to your expectations is the best first step toward achieving the polished concrete floors you desire for your facility. Keep in mind that there will virtually always be unpredictable variations that can only be uncovered by grinding and polishing the slab.
4.2 Gloss Level
Depending on the diamond grit used to polish a concrete floor, you can achieve different levels of sheen, from matte to a glassy mirror-like finish. Here are the four levels of polishing and the degree of shine you can expect to achieve at each level.
Level 1 (Flat / Ground)
A level 1 ground polish usually can be obtained by stopping below the 100-grit resin bond. When you look directly down at the floor, it will appear somewhat hazy with little if any clarity or reflection.
Level 2 (Satin / Honed)
A level 2 honed polish is obtained by stopping at the 400-grit resin bond, producing a low-sheen finish. When you look directly down at the finished floor and at a distance of roughly 100 feet, you can start to see a slight overhead reflection. This grit level produces a low-luster matte finish.
Level 3 (Semi-polished)
A level 3 polish is achieved by going up to an 800-grit or higher diamond abrasive. The surface will have a much higher sheen than that of level 2 finish, and you’ll start to see good light reflectivity. At a distance of 30 to 50 feet, the floor will clearly reflect side and overhead lighting.
Level 4 (Highly Polished)
This level of polish produces a high degree of shine so that when standing directly over the surface, you can see your reflection with total clarity. Also, the floor appears to be wet when viewed from different vantage points. A level 4 polish is obtained by going up to a 3,000-grit resin-bond diamond or by burnishing the floor with a high-speed burnisher outfitted with specialty buffing pads.
IMPORTANT TIPS – Measuring the Gloss Level
Once you have completed the entire polishing process, you’ll be left with a beautiful, shiny surface. But how do you accurately assess the degree of shine, other than by simply visually inspecting the amount of light reflectivity or clarity of the polished surface? Today, specifications for polished concrete are now including specified gloss readings, determined using gloss meters. Gloss values express the degree of reflection when light hits the concrete floor surface, and range from 20 to 30 (low gloss) to 70 to 80 (high gloss).
There are 6 ways concrete is colored:
- Integral – Performed at the time of pour and is considered environmentally friendly.
- Integral by seeding a cement/pigment mixture in the top region during power trowel finishing
- Penetrating Water Based Dyes – Performed during the polishing process and is considered environmentally friendly.
- Penetrating Solvent Based Dyes – Performed during the polishing process and is not considered environmentally friendly.
- Penetrating Acid Stain – Performed during the polishing process and is not considered environmentally friendly.
- Colored penetrating surface sealers which are also film-forming and thus produce a more solid color – Considered environmentally friendly
Different manufacturers offer different coloring choices to polished concrete customers. Here is the 24 stock colors covering the most common color choices seen in floors today offered by Ameripolish. Custom colors are available upon request. AIC is a certified installer for Ameripolish.
5. How Much Does Polished Concrete Cost
Polished Concrete project cost can vary widely based on factors including concrete condition, job size and location, aggregate exposure, gross level and coloring selection etc. For a fairly smooth floor, that requires only a few levels of grinding, $3 sq. ft. is the basic cost for a polished concrete floor. If the floor requires more in-depth grinding or includes coloring with stains and dyes or other special finish designs, then the price ranges between $3-$8 sq. ft.
Smaller residential floors tend to be a bit higher in price because of the requirement for smaller equipment which will relatively lower work efficiency and special design requirement.
6. Expectations and Limitations
Not all concrete is a good candidate for processing and polishing. When working on existing concrete, results are largely dependent on the quality of concrete a contractor is given to work with.
Most existing commercial concrete that is of sufficient strength and finished will allow for excellent results.
Variables such as aggregate, color variations, miscellaneous contaminates, cracks, patterns left by previous floor covering, existing stains, nail holes, patched areas, and flatness can affect the final appearance and results.
A slab newly poured based on specifications designed for polished concrete finish will eliminate a significant number of variables and provide improved finish results over an existing finished concrete slab.
7. Frequently Asked Questions
Is Polished Concrete Slippery?
Because of polished concrete’s unique shine and high reflectivity, many people question if it is slippery. Generally speaking, when the concrete is clean and dry, it is generally no more slippery than plain concrete surfaces. In fact, polished concrete tends to be less slippery than waxed linoleum or polished marble.
There are also anti-slip conditioners that can be applied to a polished concrete floor for extra protection against accidents. The special additives in these products are designed to improve traction and make wet surfaces safer. No additional cleaning is required, but normally it needs to be reapplied periodically.
How Do I Maintain Polished Concrete?
Maintenance for polished concrete is very minimal. However, regular cleaning is still needed. Regular care includes occasional damp mopping to remove dust or grit. You may also consider using some neutral cleaner and conditioner that cleans the surface and leaves behind a dirt-resistant film.
Except for high traffic areas, polished concrete will keep its shine for years. If it should ever dull, it is easy to restore. Sometimes simply buffing the floor with a commercial polishing compound will do the trick. If more touch-up is necessary, the floors can be lightly re-polished with a fine-grit abrasive.
IMPORTANT TIPS – Clean Spills Quickly: Corrosive or aggressively staining contaminants should be removed quickly to avoid possible staining.
What are the Conditions to Avoid to Maintain Polished Concrete?
- Standing liquids of any kind, including water
- Detergents containing hydroxides or sulfates
- Acidic or caustic cleaners; acidic detergents will etch the surface over time and dull the floor’s finish
- All contact with any acids
- Treated dust mops or sweeping compounds
- Bleach or any acidic/harsh chemicals
- Aggressive scrubbing brushes; Strata Grit, Nylo-Grit and other aggressive scrubbing brushes will alter the polished pattern and leave a dull appearance
Have More Questions about Concrete Polishing?
Contact us and ask any questions about our concrete polishing services. We’d like to help!