How Is Concrete Polished?
To understand how concrete is polished, a good analogy is sanding wood. To smooth a rough-sawn piece of wood, you would begin with a coarse piece of sand paper progressing down to a very fine piece of sandpaper. With concrete, heavy-duty polishing machines equipped with progressively finer grits of diamond-impregnated segments or disks (like sandpaper) are used to gradually grind down the concrete. The grinding continues to the desired degree of shine and smoothness.
The process begins with the use of coarse diamond segments bonded in a metallic matrix. The segments are coarse enough to remove minor pits, blemishes, stains, or light coatings from the floor, giving it a smooth feel. Depending on the condition of the concrete, this initial rough grinding is generally a three- to four-step process.
The next steps involve fine grinding of the concrete surface using diamond abrasives embedded in a plastic or resin matrix. Crews use ever-finer grits of polishing disks (a process called lapping) until the floor has the desired sheen. For an extremely high-gloss finish, a final grit of 1500 or finer may be used. Experienced polishing crews know when to switch to the next-finer grit by observing the floor surface and the amount of material being removed.
During the final polishing step, some contractors spread a commercial polishing compound onto the surface to give the floor a bit more sheen. These compounds also help clean any residue remaining on the surface from the polishing process and leave a dirt-resistant finish.