Concrete polishing sealing Q&A

Concrete polishing sealing Q&A

Full 7 steps system (FT2/hr)

How slippery the polished concrete is?

Slip resistance is a concern with many floor systems, but particularly for concrete floors. Risk of injury is one of the biggest drawbacks to concrete. Intuitively, one might suspect that a highly polished concrete floor would become highly slippery-and thus more of a problem. It turns out that’s not the case.

Contrary to a common perception, the degree of polish or shine is not directly related to slip resistance. A 400-grit finish can and usually is less slip-resistant than a higher 1500 or 3000-grit final finish. It helps to think of it in this way: when a floor is wet and a person walks on it, the peaks and valleys in the landscape of the surface create a tendency for the person to “hydroplane.” On a completely flat surface such as that produced by 1500 or 3000 grit, the water is pressed out from under the shoe, putting the sole directly in contact with the concrete surface— actually making the shoe stick to the surface. A true grinding and polishing system with the highest levels of shine (using 3000-grit polishing) and gloss (gloss meter readings in the range of 45 to 65) exceeds OSHA (Occupational Safety and Health Administration) and Americans with Disabilities Act (ADA) standards for coefficient of friction and slip resistance, which are the two most widely accepted standards for these safety criteria.

The process creates an attractive environment with increased light reflectivity, a desirable characteristic in today’s safety-conscious marketplace.

Polishing system is chosen and certified by NFSI as a high traction and considered to be very safe.

What are the requirements for concrete intended to be polished?

4. Flatness requirements: ASTM International E-1155

5. Tight hard troweled (three passes) concrete.

6. No burn marks

7. Curing options (ASTM International C-309, C-171) — no acrylic curing and sealing compound

8. Admixtures may be used

Concrete must be dry out for at least 28 days after installation.

Can Lightweight / Air-Entrained concrete be polished?

Lightweight structural concrete is actually so because of the aggregate, and not the cement. Various aggregate recipes use various light weight materials to reduce the weight of concrete by as much as 40%. Lightweight concrete also provides greater fire resistance and greater R-values than normal weight concrete, in part due to air entrainment, which also allows the internal retention of more water, which enhances internal curing and hence, the strength and durability of the concrete.

Air entrainment principally is recommended to improve resistance to freezing when exposed to water and de-icing chemicals. However, there are other important benefits of entrained air in both freshly mixed and hardened concrete. Air-entrained concrete contains billions of microscopic air cells. These relieve internal pressure on the concrete by providing tiny chambers for the expansion of water when it freezes.

Concrete polishing sealing Q&A

The amount of entrained air is usually between 5 percent and 8 percent of the volume of the concrete, but may be varied as required by special conditions. The use of air-entraining agents results in concrete that is highly resistant to severe frost action and cycles of wetting and drying or freezing and thawing and has a high degree of workability and durability.

If polished, lightweight concrete would require the same finishing approach as the regular concrete, i.e. grinding, densifying, and lithium coatings.

However, some limitations to the finished result to be seriously considered.

The water retained by the air entrained concrete and the more porous, lightweight aggregates also greatly increases the cure time for fully dry material. The air entrainment also causes the concrete to exhibit a more porous surface after grinding, which can cause irregular results in finish applications. The more porous aggregates, such as shale, will often fracture during grinding. These imperfections can cause inconsistency in the way the concrete accepts applied finishes.

Industry standard does not completely rule out the polishing the surface of lightweight concrete, nevertheless, customers might not get the type of finish they were expecting.

How to calculate the quantity of concrete for the project?

Use this handy tool to calculate concrete yards for your project. It will also tell you how many bags of premixed concrete are needed. When pouring concrete, you should always order at least 10% more than the exact amount the project calls for. Just take the cubic yardage figure and multiply it by 1.10. It’s better to have too much versus running short. It’s a real pain if you know what you run out and have to order more. You will probably get charged extra delivery fees and fuel charges. So save yourself some money by making sure you have enough.

Slabs, Square Footings, or Walls

Leave a Reply