I spend much of my day doing the same thing.... educating folks on various concrete floor finishing options. It never ceases to amaze me as to what they tell me about their experiences with low cost floor finishing.
While 'Polished Concrete' is a term encompassing a wide spectrum of final finishes, there are a few "contractors" who push this term just a little too far & for their benefit alone. It most often comes down to "price". Don't be a victim. Ask a few questions before your contractor arrives and certainly before any money changes hands.
Best Practices:
Ask, then listen carefully.
If your contractor is knowledgeable and informed, it will show. Let them explain options and how the system works. As mentioned, polished concrete is a spectrum of final floor finishes. Pricing is based upon time and materials and varies for each option but is generally based on square metres. The higher the gloss and the more effort to achieve the desired results, the higher the price will be.
Polished Concrete is mechanically honed and polished concrete - Metal bonded diamonds do the cutting stages while the polishing process is done with resin bonded diamonds. Liquids, known as densifiers are applied during the cutting stages. Densifiers fill the capillaries and tiny pores of the concrete. As they dry, they crystallize, hardening and dustproofing the floor, improving its ability to be polished. The concrete floor is treated at least once during the grinding process. Various end degrees of gloss are directly related to how high a grit diamond was used last. Generally, for Matte finish, 200 grit, Satin, 400 Grit, Gloss 800 grit and high gloss 1500 grit diamonds are the final step. After the concrete has been burnished by a high speed diamond impregnated pad of the highest grit levels of 800-3000 grit, the floor can receive a stain guard to protect against common materials. Depending on where the installer stopped the grinding/polishing process, there can be a myriad of final results, yet they all share these same common installation procedures. In a nutshell, the spectrum of what is being called 'polished concrete', covers virtually all mechanical floor grinding, densification and integral sealing.
What is NOT 'Polished Concrete'?
I'm sure you are familiar with the phrase.... "if it looks like a duck and talks like a duck....."
How about... "you can fool some of the people, some of the time"........
These come to mind quickly when I see results like the photo at the top of the screen and this one....
This is NOT polished concrete, it is a poor "grind and seal" with an epoxy top coat. It is quite obvious from the reflections we see, the client did not get what he paid for.
We are coming across this more and more. Clients either do not pay for the outcome, or they call us within months to see if it can be "fixed". Short answer, it can be fixed, but it will need to be completely removed (cost of demo) and it then needs to be done correctly. (true cost of the installation). By the time all factors are considered, the client will have paid for their floor not once, but as many as 3 times. This is the true cost of working with a low cost contractor.
If you can take a knife or a razor to the floor and scrape off anything, it's just not polished concrete.
Be aware and be vigilant. In as much as 'polished concrete' represents a wide spectrum of floor finishes, only polished concrete, by definition, is 'polished concrete'.
Topical sealers will eventually wear and need to be replaced. This is one of the key advantages to 'polished concrete'...... lower maintenance and never needing to replace a topical coating.
In closing, understand not all contractors will provide the same end result. Floor finishing is a trade and not a process one learns overnight. Concrete is not a specific medium, meaning it is not consistent. Some is softer, some harder, some more porous, some less so. Allow your installer to use their training and experience to get you the final finish you desire. Learn about the process you are purchasing and ensure you get exactly what you ordered. It is too easy to be led astray by a less than honest contractor. A little education goes a long way!