Concrete is used for every floor that is on grade. The term “on grade” means there is dirt under the slab that supports the weight of the floor. Most large concrete floors, when placed, are finished using a power trowel—large, walk-behind and ride-on machines with floating, combination, and finishing blades attached.
Power trowels do a wonderful job in the main field. When you have wide open spaces, they perform the task quickly and efficiently. The issue with a power-troweled floor is the edges. An edge is anywhere concrete is placed up to a wall or next to a form board. In these areas, another finishing method is used.
What is Concrete Edging?
A concrete edge is anywhere the concrete pour has started or ended. Ideally, the aim is to have the least number of edges as possible. An edge can be found at any vertical surface next to where the concrete will be placed. Concrete forms will also produce an edge. A form board is considered a termination point for the pour.
If you have been on a large concrete project, you’ll notice they try to minimize edges. If the entire floor can be placed at one time, they will do just that. By installing a continuous pour using minimal form boards to place against, the finished slab will be flatter.
How to Do Concrete Edging
A concrete edge is always finished by hand. To date, there is no power equipment available that can place a nice finish when the pour is stopped. There are two types of edging tools. One has a long pole handle attached, allowing the contractor to stand and walk while finishing. The other, which has been around the longest, is a true hand tool. The work is performed while kneeling next to the edge with the tool in hand.
Both styles are tools used to produce a neat, rounded edge along the perimeter of the slab. The tools come in various shapes, weights, and sizes, with a curved edge or a half-moon design. An edger is used to smooth and then finish the edge after the main field has been finished. When finishing an edge, the concrete is tightly compacted, producing a durable surface. Factors like blade type, handle material, and total weight influence the experience. For instance, a heavier tool may offer more stability but could exhaust you faster. Meanwhile, a lighter-weight choice allows for easy maneuverability but could increase finishing times. The radius that an edge produces comes in assorted sizes. The typical interior joint radius is 1/8” and for exterior edges, ¼” – ½”.
Stand-up concrete edgers might seem to make your life easier. These tools let you edge concrete slabs without bending over. Traditional methods usually require squatting or kneeling. With a stand-up concrete edger, it is easier to keep an upright posture.
Manufacturers design these edgers with adjustable pole handle lengths. These will include durable blades that form the concrete edge. Choosing the right stand-up concrete edger matters.
Hand-held edgers are the most widely used type. They have similar blades to stand-up models. If you talk to the old finishers, they will say that the level of control you have when using a hand-held is much better. Your vision is great since you are right over the tool while finishing.
Concrete Edge Defects
According to industry studies, using an edger improves overall project quality and appearance by up to 30% (Concrete Construction, 2021). Having the edges match the main field will give the appearance of a well-placed slab.
Concrete is the only building material that is produced onsite. It’s delivered in a plastic state and hardens once the concrete contractor has performed their finishing process. Environmental conditions will impact the curing process. Hot temperatures and wind will promote water loss. There will always be water loss since there is about twice the amount of water in the mix as needed to hydrate the cement. If water loss happens too early, finishing the surface can be difficult.
The edge defects that are clearest include surface cracking, irregular radii, waviness, and dipping. Cracking could be trying to edge too late when the concrete is already setting. Once the first set takes place, it becomes less malleable. Trying to shape a firm surface can be difficult, and cracks will appear.
When multiple finishers are working edges on the same slab, having the same tools is important. The weight, width, and radius must be the same throughout the project. If not, it will be noticeable.
The goal when finishing edges is to produce a flat slab and a uniform radius. The radius is produced with the edger. If the tools are the same, this should not be a concern. The number one issue with edges is when they are dipped. A dipped edge is when the finisher overly applies pressure on the plastic concrete, creating a lower edge than the field. This is not that big of an issue when placing sidewalks or driveways, but when it happens on an interior slab that will be polished, it is important. When a polishing contractor contends with a dipped edge, the surface will need to be hand-ground, honed, and polished. They seldom completely match the main field that was processed with a walk-behind grinder.
Concrete compaction can also be an issue when the floor is dyed and polished. If the surface is not compacted well, dyes will not be absorbed the same as the machined area. Weak surface edges have a tendency to turn out much lighter in color.
Conclusion
Concrete is a wonderful building material. It has great compressive strength to support tremendous loads. Placing a concrete slab takes experience and skill. It is not self-leveling, so screeding the plastic mix flat is important. Concrete is never as flat as it is when initially screeded. The more the surface is worked, the more imperfections appear.
That’s the biggest issue with edges: they get overworked. When you watch a finisher work the edges, you will see multiple passes over the same area. Edging is also an art. There are experienced finishers who do not like following a less experienced worker on the edges. They prefer to start and finish their own edges.
Edges are the first area of a floor looked at when a polished floor is evaluated. The edges tell the true story. Now, the quality of a polished project should not be put only on the polishing contractor's shoulders. There are times when the concrete finisher has an impact on the result. When polishing, it takes special equipment and tooling to perform the edge work. DiamaPro Systems manufactures stand-up edgers, hand-held grinders, and cup wheels to make the polishing job easier.
We are ready to answer all your polished edging questions and will show any piece of equipment you would like to see on-site or at your office!