How to Cut Concrete with a Diamond Blade?

Whether you're sawing control joints, enhancing the concrete with decorative scoring, or cutting out existing concrete for patching or replacement, you can't do the job without a top-quality saw blade. Diamond saw blades are typically the best choice when it comes to making clean, professional cuts in concrete. Follow these 4 tips below for good sawing results.

Understanding how a diamond blade works will help you choose a blade with the right characteristics and cutting quality for your needs. Here are the four basic blade components:

(1) The metalcore, a precision-engineered steel disk with a segmented rim that holds the diamonds.

(2) The synthetic diamond crystals, the sharp cutting teeth that slice through the concrete.

 

(3) The matrix, a metal band that holds the diamond particles in place until they wear away.

(4) The weld, which attaches the cutting segments to the core (most segments are laser welded or soldered).

The exposed diamonds on the surface of each segment do the cutting, using abrasive action to slice through the material as the blade rotates at high speeds. As the diamonds at the surface become dull through use, the matrix begins to shed away to release the worn diamond crystals and expose new, sharp diamonds embedded within the matrix.

The most important fact to know is that the hardness of the matrix controls how quickly a blade wears. Here's the basic rule:

(1) A diamond blade used to cut soft, abrasive materials (such as uncured, green concrete) should have a hard metal bond so the exposed diamonds are fully utilized before they shed away.

(2) Conversely, a blade for cutting hard, nonabrasive concrete should have a soft bond to allow for easier erosion of the matrix, which will ensure exposure of new, sharp diamonds when you need them.

For maximum cutting speed and blade life, you should match the blade as closely as possible to the material you're cutting. Characteristics of the concrete you need to know to include the compressive strength, the size and hardness of the aggregate, and the type of sand.

We consider concrete with a compressive strength of 3000 psi or lower a soft material and concrete with strength above 6000 psi a hard material. Therefore, you should use a blade with a hard bond to cut the lower-strength concrete and a blade with a soft bond to cut high-psi concrete.

Similarly, hard aggregate (such as trap rock, basalt, and quartz) dulls diamond particles quickly, so use a blade with a softer bond to allow new diamonds to be exposed as needed.

The size of the aggregate in concrete primarily affects blade performance. When cutting through the larger aggregate (3/4 inch and up), the blade cuts and wears more slowly. Pea gravel (smaller than 3/8 inch) is easier to cut, but the blade will wear faster.

The type of sand determines the abrasiveness of concrete, with sharp sand being the most abrasive and round sand the least. To determine the sharpness of the sand, you need to know where it's from. Crushed or river bank sand is usually sharp while river sand is round and nonabrasive. The more abrasive the sand, the harder the bond requirement.

What if you will be cutting more than one type of concrete? As a general rule, we recommend choosing the blade based on the material you'll be working with most often or the material for which top blade performance is most important. Most diamond blades can cut a range of materials.

If you're placing new concrete, you have the option of cutting control joints while the concrete is still green (about 1 to 2 hours after finishing) or the next day after the concrete has hardened. The timing of the cut will dictate the type of blade you select.

Some decorative concrete contractors prefer to cut concrete while it's still green because it minimizes the occurrence of ugly random cracking (especially in warm weather, when concrete hydrates faster) and permits shallower joint depths of an inch or less.

However, green concrete will be softer and more abrasive than the same concrete in a cured state. That's because the sand in the mixture hasn't yet bonded to the mortar and it acts as an abrasive. Blade manufacturers offer hard-bonded diamond blades specifically for cutting green concrete.

Often the decision of cutting wet or dry depends on your preference and job requirements. Dry cutting eliminates messy wet slurry and the need to equip saws with water tanks and hoses. Using a blade wet, on the other hand, reduces dust but makes it necessary to contain or clean up the slurry. For indoor jobs where you need to keep the work area dry, a dry-cutting blade and compatible saw may be your only option.

The main difference between wet and dry blades is the weld (as described in Step 1). Dry-cutting blades have segment welds that resist heat and don't require water for cooling. They are usually intended for intermittent cutting and for use on handheld, low-horsepower saws.

If you're sawing decorative pattern lines in concrete, dry-cutting blades are often the best choice for making crisp, clean cuts (see Sawing and Patterning). These decorative cuts are typically only 1/16 to 1/4 inch deep and do not function as control joints.

Wet-cutting blades are typically used with walk-behind saws for cutting joints in cured concrete flatwork because water cooling permits deeper cuts. Although it's possible to use most dry-cutting blades with water, never use a wet-cutting blade dry. Always continuously cool the blade with water to avoid segment loss and blade warpage.

If you want to get more information on the use of diamond blades after reading the above, MORETOP is happy to share professional knowledge with you.

MORETOP is an experienced manufacturer of multi-function power tool accessories. We have a good reputation in the industry with our excellent manufacturing technology and thoughtful after-sales service. We are equipped with a professional quality inspection system and a comprehensive management team, which can strictly control the quality of our products. If you have a demand for diamond blades, MORETOP must be your best choice.