Diamond Polishing Concrete Slabs
Written by Todd Fratzel.
Polished Commercial Building Slabs
We are completing a 36,000 sq. ft. commercial building for a client and on of the exciting new construction techniques that we’re using is diamond polishing of the slab. Traditionally a large building like this would have the slab coated with an epoxy finish to protect the slab from liquid spills and traffic. However, another alternative is gaining popularity and that’s the use of diamond polishing.
Diamond polishing is a fantastic way to treat a new or old slab to protect it from day to day abuse. The process involves grinding and polishing the slab with several different grits until the surface is extremely smooth and hard. As you can see in the photo the surface becomes very shiny and looks like it’s been sealed with a shiny material.
How To Polish Concrete Slabs
Polishing concrete slabs is done by using a large floor poslisher that has diamond impregnated sanding discs. The photo shows a 20 HP Lavina 32 SPS Concrete Floor Polisher that’s being used on our project. Lavina polishing machines are planetary movement machines featuring 6 heads. The planetary motion results from the friction between the tools and the floor, which allows the tools to spin either clockwise or counterclockwise. This way the tool will not force itself against the surface’s resistance.
The floor get’s polished with several different grits. After the first rough grinding a concrete densifier is applied to the surface of the concrete. The densifier is one of several commercially available products such as sodium silicate (or a related silicate or siliconate).
This is applied to the floor to densify, or harden, the concrete. The solution is absorbed into the concrete matrix, filling the pores. Chemically, the silicate reacts with the calcium hydroxide in the concrete to produce calcium silicate hydrate. Sodium silicate is the most common hardener. Potassium silicate, lithium silicate, and various siliconates are also used. After the silicate infuses into the concrete, it crystallizes in place. Then the polishing continues.
Polishing continues until the specified “sheen” is reached. Most applications are polished to a minimum of 800 grit and a maximum of 3000 grit! The final step for our floor was the application of a concrete sealer which was then burnished into the slab. This provides a very good sealer to help prevent stains from oils and lubricants that might be used in the manufacturing facility.
Cost and Benefits To Polish Concrete Floors
Polishing concrete floors or slabs makes sense for several reasons. The cost of polished concrete floors ranges from $2/sf to $4/sf. The range depends on how smooth the surface finish will be and if any stains or colorings are used. For our project the cost was about $2.35 per sq. ft. This is pretty good when you consider most epoxy coatings run $1/sf to $3/sf.
The benefits of a polished concrete floor are fairly obvious. Polished concrete floors require little to no maintanance whereas floors with coatings require regular maintanance and re-application. The other big benefit to using a polished floor is the elimination of potentially dangerous chemicals. By eliminating paints and epoxies we’re providing a much “greener” option.
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