Diamonds Are a Guy's Best Friend

Cutting lines, grooves and control joints with diamond blades is nothing new for concrete contractors, but enterprising craftsmen have been putting their creativity to the test by using the blades to produce decorative borders, graphic designs or V-shaped grooves that look like they were hand-tooled.

Tom Ralston, a third-generation concrete contractor from Santa Cruz, Calif., most often makes decorative saw cuts on interior floors in grid patterns (two-by-two-foot squares or three-by-three-foot diagonals) but says diamond blades can be used to cut any variety of designs.

“You can slice and dice a floor up like a boarding house pie,” he says.
Diamond blades can be used to cut both green and cured concrete, using a variety of right-angle grinders, hand-held circular saws, Dremel tools or walk-behind saws. A variety of blades are available in the market, each serving its own purpose.

Ralston uses Norton/Clipper Corp.’s Slab Crab, a new saw with wide rubber wheels that allows him to cut perfectly straight lines; a Soff-Cut saw for structural cuts in green concrete; a four-inch grinder to make circular patterns; and a Dremel tool.

He likes to get out on the slab days after it’s poured, lay out the design on his hands and knees, snap the lines using orange chalk — which doesn’t stain the concrete — and make his cuts, often by hand. The saw cuts can act as small dams, making it easy to use different acid stains in the design without the colors bleeding into one another. For example, he created a unique design on a residential entryway using Italian marble in one section, black acid stain in another, antique amber with bits of real copper in another, and deep score joints filled with copper epoxy.

Blade basics
A diamond blade is a circular steel disc with a diamond rim, which can be segmented, continuous or serrated. The rims are made up of a mixture of diamonds and metal powders that hold the diamonds in place.

As the blade hits the concrete, this bond wears away, exposing the diamond crystals that grind the material into a fine powder, says Thom Fisher, advertising and trade show manager for Diamond Products, Elyria, Ohio.

One general rule of thumb is to use a soft bond to cut cured concrete and a hard bond to cut green concrete. A soft bond will expose the diamonds quickly to cut harder materials, while the harder bond will wear away more slowly to cut softer materials. Fisher’s company provides contractors with a map that shows how aggregate differs in hardness in various areas of the country — an important consideration in choosing a blade. And if a contractor has trouble with a blade, Diamond Products can provide a custom bond within 48 hours.

Making sure the blade matches the saw is another consideration. “The quality of the blade needs to match up with the horsepower of the saw,” he says. “If you’re using a small saw for a small job, you don’t need a top-quality blade that’s loaded with diamonds and costs a fortune.”

However, Fisher says contractors will regret choosing blades merely on price, because the industry is loade d with cheap imports — at the World of Concrete show last year, he says, 60 of 65 diamond blade companies were from overseas. “The old axiom, ‘You get what you pay for,’ really applies here,” he says.

Ted Skaff, market specialist for Pearl Abrasive of Commerce, Calif., says distributors should ask contractors two main questions: “What saw are you using, and what exactly are you cutting?” He’s found that more contractors are scoring lines, swirls, circles or other decorative elements in green concrete.

General purpose blades are usually used on cured concrete because using them on green concrete can cause excessive blade wear and undercutting, but Skaff says contractors are having good luck using a general purpose, narrow-slot turbo rim blade to cut green concrete because decorative concrete lines are shallow — typically only one-sixteenth to one eighth-inch deep. “You can have your cake and eat it too,” he says. “Not everyone knows that.”