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  • When all the steps are carried out properly from the get-go on a polishing project, a polished concrete floor will become the focal point of any commercial facility.
  • Proper concrete placement and finishing techniques set the stage for a successful polished concrete job.
  • Laser screeds are commonly used to help meet specified floor flatness and floor levelness numbers. (Photo courtesy of Structural Services Inc.)
  • Notice the wavy appearance of this polished floor. This indicates that the specified FF and FL numbers were not met. It's virtually impossible for the polishing contractor to expose only the fine sands on a floor surface this wavy.
  • Curling at the joints will also create higher sections of the slab, making it nearly impossible to expose only the fine sands during polishing.
  • A Dipstick is the fastest and most accurate way to measure the flatness and levelness of concrete floors, per the ASTM E-1155 F-number system. (Photo courtesy of SSI)
  • If areas of the floor need repair due to poor finishing or damage during construction, great care should be taken to use the appropriate repair material. In this case, a pigmented resin was used when a cement-based product matching the color of the dye would have achieved better results.
  • Equipment from other trades should be fitted with nonmarking tires and be diapered to prevent hydraulic leaks.
  • Polishing contractors are responsible for meeting specified minimum gloss requirements. Usually several gloss meter readings are taken in a given space and then an average is calculated. A gloss reading above 70 indicates a very shiny floor.

Commercial Floor Checklist

Check out this Checklist of Responsibilities on a Commercial Polishing Project which outlines the roles different trades play during the concrete construction process.

As a polished concrete consultant, I have been involved recently in several preconstruction meetings for a large retail store chain. These meetings have proven to be very productive and an important step toward improving the quality of the retailer's floors, not to mention being a valuable learning experience.

These clients chose polished concrete for a good portion of their interior floors for a variety of reasons, including aesthetics, ease of maintenance, and light reflectivity. Upon visiting some of their earlier polished floors, we noticed a few problems that ultimately had nothing to do with the quality of the work done by the polishing subcontractor, but instead resulted from the work of the placing and finishing contractor. When polished concrete started becoming popular, specifications were being written inappropriately, setting up the polishing contractor for failure. One specification we came across in particular called for a light salt-and-pepper finish (exposing the sands with no coarse-aggregate exposure), but made no reference to floor flatness(FF) or floor levelness (FL) tolerances. As a result, some of these floors exhibited unlevel, wavy surfaces with raised sections that made it nearly impossible to expose only the sands. These areas showed patches of coarse-aggregate exposure, which the owners did not want. The remedy for this problem was to install the concrete within specified tolerances. In addition, specifying lower-shrinkage concrete materials, combined with tighter joint spacing, would significantly reduce the amount curling the concrete would exhibit.

Witnessing these recurring problems, it became apparent that we needed to revisit the entire concrete placement process, starting with how the subgrade was prepared all the way through to the curing of the slab and, ultimately, the polishing. After attending several of these preconstruction brainstorming sessions, it really got me thinking about the crucial roles each of the different trades play during the concrete construction process (see Checklist of Responsibilities on a Commercial Polishing Project). Everyone involved on a polishing project should be sharing the same common goal, which is to create a durable, architecturally pleasing floor. What's more, these floors have to be reproducible on a consistent basis from one region to the next. Of course, this is a daunting task considering some of the jobsite variables involved.

During these prepour gatherings, which were chaired by Pat Harrison of Structural Services Inc. (SSI), the main goal was to discuss how to improve the quality of these high-end floors and define each subcontractor's responsibilities. In addition to polishing, the topics included concrete pour schedules, mix designs, subgrade preparation, steel reinforcing, vapor barriers, admixtures, concrete plant information, concrete testing, placing and finishing techniques, and joint sawcutting and filling. As you can see, there's a lot more to a successful polishing project than simply passing a grinding machine back and forth across the concrete. Each trade needs to contribute their specific knowledge and skills and be held accountable for their scope of work.

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