How to prepare for polish concrete
Due to its attractive design aesthetic polished concrete has become very popular. Its low maintenance finish requires no waxing or sealers and it’s easy to clean. Like everything in construction, care must be used in order to use this finish effectively. When thinking about polished concrete, you should discuss a few things with the project team before beginning the polish.
A level surface is important.
The levelness of the concrete pour is key to a uniformly polished floor. The slab shouldn’t vary more than 1/16th of an inch across the surface to maintain a consistent aggregate exposure and sheen. Flatness is measured in levels (referred to as the FF rating). Because the finish-grinder is relying on a flat surface to get a uniform grind to expose the salt & pepper effect, an FF rating of 50 is advised. If the areas aren’t leveled correctly, differences will be evident in the appearance.
Big spaces are easier to level.
Buildings like residential spaces with smaller rooms will require more pours, broken up by room and must be leveled by hand. Whereas in larger spaces like warehouses and grocery stores, the pour will be smoother since a laser screed can be used to level the floor. However, the cost of the laser screed technology will need to be built into the budget. Research can be done to find a contractor that can give an FF 50 with a hand level if the budget doesn’t allow for the laser screed. While hand finishing isn’t necessarily recommended, it is an option.
Protection is very important.
Until finishing can begin, slab protection is critical to preserve integrity of the concrete. The concrete slab is usually poured in the beginning of construction and is exposed during the construction. It must be protected from damage. Depending on the class of aggregate exposure, some outer damage, like spilled paint, may not be ground away. Plywood mats below man-lifts, temperature control and plastic boards can all be used to protect the slab. For joints, ‘breathable tape’, not duct tape, can be used since concrete will cure and evaporate moisture. Using tape that doesn’t breathe could result in trapping moisture that could leave lines on the slab which could hold finishing stain and sealer and possibly ruin the it.
Cracking can be expected.
Cracking can be controlled, though due to its nature it can happen as the building settles into place. To help reinforce the material fibers can be added pre-pour. To account for the shifting of the steel support columns, strategically placed control joints can be added to isolate the slabs. Also, the industry standard for concrete depth is 4 inches, however increasing it will gain stability.
Polished concrete offers long-term durability and beauty in the right space. Taking notice of space, attention to detail and protection, the most intricate project with polished concrete can go just a little smoother.