Diamonds Grinders for Concrete Surface Prep

The word "diamonds" is inevitably associated with the concept of "big bucks," but like many other things about diamond grinding, this is something of a misconception. Diamond grinding can be completely competitive if you know how to do it.

Until recently, most people in the concrete industry have thought of diamonds only in terms of polishing. More mundane tasks, like removing coatings or prepping a stained and chipped surface for a new coating or microtopping, are easier to associate with brute-force methods. There's a certain irony in this perception, since concrete polishing came about because of the availability of machines designed for grinding.

Concrete is a hard material by design, and changing its surface requires force. Mark Elliott, a sales manager for Superabrasive Inc. in Atlanta, Ga., puts it this way: "Anytime you grind or shot blast, you're doing damage, but it's controlled damage." The old methods use vertical force. Shot blasters fire a steel shot downwards, hammering the concrete. Scabblers pound up and down with tungsten carbide tips. Scarifying rotates a series of carbide tips downwards like a soil cultivator digging into a field. They all strike vertically to fracture the top layer or break through the coating, and the concrete they leave behind is also microfractured. These methods are very aggressive, and each one has only a narrow range of profiles it can achieve.

Grinding wears away a hard surface by cutting across it with something harder. Diamonds are the hardest natural substance known, and their edges scratch into the surface while moving parallel with it. The size of the diamonds determines the depth of the scratches. The International Concrete Repair Institute (ICRI) defines 10 levels of Concrete Surface Profiles (CSP) from acid etching to milling. Diamond grinders can produce all of them.

Grinding is done with the same machine as diamond polishing. Most grinders use three or more spinning heads in a planetary arrangement: The discs spin on their axes in one direction, but their axes also orbit around a central point in the other direction, like rotating planets orbiting the sun. This produces a very even pattern across the entire path of the grinder. "You get a very flat, monolithic surface," says John Abrahamson, president of HTC Professional Floor Systems. "You get a beautiful floor — you remove all the imperfections."