Utilizing exposed concrete floors in homes, schools, and businesses has been a popular choice for many years now thanks to its low maintenance and many possibilities. It is a trend that is more and more becoming a design fixture that is here to stay. When polishing concrete to a decorative finish, there are endless style options.
However, there is one item that can throw off the whole design of a floor: unsightly random cracking running through it—completely spoiling the aesthetic. How does this happen? Unfortunately, there isn’t much to do for an old slab, so this article will focus on newly poured concrete. With newly poured concrete, there is a way to reduce and possibly even eliminate random cracks. Ensuring an exposed concrete floor only receives “oohs” and “ahhs” instead of “eeeks” and “that’s a shame”.
Timing of the cuts: Let’s assume the newly poured concrete is a good quality slab. While concrete is hydrating and internal stresses start to build up, the concrete is looking for a way to release this stress. If a cut is made during this time, what we call the Green Zone™, the concrete will “crack” directly below this cut instead of creating a random crack on the surface. The Green Zone is the time between the initial set and the final set or to put it another way, during the first 1 or 2 hours after finishing. This is the prime time to make Ultra Early Entry™ cuts to avoid random cracks. The main purpose of Ultra Early Entry cutting is to cut control/contraction joints as these joints allow for movement in the plane of the slab and induce cracking by drying and thermal shrinkage at preselected locations. The joint forms a plane of weakness in which a crack will form.
The most important and difficult part of cutting is knowing when to cut. To detect the start of the Green Zone, the operator can touch, step, and/or roll the saw onto the slab. When there is no impression made on the concrete by one of these testing methods, the concrete is in the Green Zone and it is time to cut. If there is an impression left by touching, stepping, or rolling the saw onto it, it is still too early. The slab can be retested every 15 minutes.
You can also tell if an operator is cutting in the Green Zone as there should be little to no airborne dust. If there is a lot of airborne dust, the operator missed the Green Zone and the concrete has probably already started to make some random cracks.
Now that we know when to cut, the question becomes, “How can we make these Ultra Early Entry cuts in the Green Zone?” The answer lies in the Husqvarna Soff-Cut® method.
The right equipment and diamond tooling: The Soff-Cut method uses a Husqvarna Soff-Cut “up-cutting” saw equipped with a unique blade block, anti-raveling skid plate, and a Husqvarna Soff-Cut diamond blade. It is the combination of up-cutting and the skid plate, along with timing cuts in the Green Zone, that ensures the concrete is held in place to minimize chipping and spalling of the joint edges. That is the difference between Soff-Cutting and other early entry saws and blades. The blade block allows the skid plate to always maintain proper pressure on the concrete to ensure a smooth, straight cut with minimal spalling. After this cut is made, the concrete will crack directly below it.
It is important to note that Soff-Cutting does not use water compared to conventional cutting. Soff-Cut saws are dry up-cutting saws, and the Husqvarna Soff-Cut blades are specifically designed for use without water cooling. Since the concrete is still wet, there is little to no harmful airborne dust or slurry created. The debris produced will accumulate next to the cut joint on the slab and can be swept (sweeping in the direction of the cut to protect it from damage) into a container for easy clean up. Soff-Cut saws can also be attached to a vacuum to facilitate even easier cleanup.
Once the cut is made, the operator should be careful not to step on the newly cut joint as it is very fragile and the pressure applied by stepping could cause the sides of the joint to collapse. A typical job specification will require control joints every 12-15 feet. The spacing depends on slab thickness, shrinkage potential, subgrade friction, environment, and steel reinforcement. Some of these conditions will also dictate how deep the control joint must be cut, but as a general rule they are usually ¼ to 1/10 the thickness of the slab.
Of course one of the major benefits of cutting using this method is the reduction and elimination of random cracks. Using this method also allows for a shallower cut, as the concrete doesn’t need a deep cut to know it should crack below it. This shallow cut enables greater aggregate interlock for a stronger slab and minimizes the amount of joint filler that could be needed.
Since the Soff-Cut method can be utilized the same day as the placing and finishing of a concrete slab, it saves time over other techniques that wait until the concrete is cured. This means contractors can save time and money. Without the Soff-Cut system, contractors risk battling cracked slabs, irritated customers and artisans who were going to create a masterpiece out of the floor. This could cause a lot of unanticipated expenses if the contractor has to destroy the slab and re-pour.
Soff-Cutting can be used almost any time concrete is poured. It can even be used to enhance decorative floors by using a ProEdge blade to chase control joints for a beveled edge.
There are a lot of contractors currently using the Soff-Cut method, but unless they are using the complete Soff-Cut method (timing the cuts in the Green Zone, using a Soff-Cut saw, skid plate, and diamond blade) they are not truly controlling random cracking.
Soff-Cut and the Ultra Early Entry system have been recognized and certified by the American Concrete Institute (ACI 302-96) for years, which makes it the top contractor’s choice for eliminating unwanted cracks. The Soff-Cut method can save contractors time, money, and produces consistent results every time. Something contractors can rely on. ■
About the Authors:  Richard Tremain is a product manager for Soff-Cut and Stewart Carr is a Soff-Cut specialist; both are with Husqvarna Construction Products. For more, visit www.husqvarnacp.com.
Modern Contractor Solutions – May 2016
Did you enjoy this article?
Subscribe to the FREE Digital Edition of Modern Contractor Solutions magazine.