Concrete landscape borders are typically designed to assist in maintaining a well-manicured appearance of your landscaping. In time, though, these concrete borders can become cracked from water penetration and then freeze into ice that expands and enlarges the cracks. To avoid this, you will need to repair the cracks when they first appear. This will sometimes require the use of specialized materials, tools, and techniques such as those below.
Step 1 – Preparing Your Border Surface
Examine the surfaces of your concrete border to identify cracks that you will need to repair. If some of these cracks are larger and have small concrete pieces that have broken away, or are about to break away from the border, you will need to remove these pieces. Allowing them to remain in the cracks will interfere with the adhering qualities of your fillers. To remove them, you may need to use a wire brush or hammer and cold chisel. To prepare narrower cracks, widen them to receive your filler using a grinder with an abrasive masonry wheel. Be sure to clean out all the cracks with a shop vacuum or a garden hose with a nozzle. Also, be sure the cracks are moistened before applying grout or filler
Step 2 – Preparing Smaller Cracks
In using a grout to fill narrow cracks, you will need to be sure the grout container tip hole is no larger than the width of the crack you'll be filling. If you're using a new tube of grout, cut the tip small enough that the hole it creates is smaller than the crack you'll be filling. In using an existing grout tube, be sure the grout still has a workable consistency and that the tip is small enough. Apply the grout into the crack. If the crack is deeper than 1/4 inch, apply the grout in separate thin layers, allowing each layer to dry before applying the next.
Step 3 – Preparing Larger Cracks
In filling larger cracks, those wider than 1/2 inch, you'll need to apply a process called undercutting. This process prepares the crack so that the grout can resist being forced out of the crack when the crack contracts from temperature changes. To accomplish this, you'll need to widen the crack more beneath the crack surface than at its surface. You can do this by chipping away the inner crack that is below the top surface with a chisel and hammer.
Step 4 – Filling the Cracks
Into the crack press your grout filler in 1/4 inch layers using a trowel. Before applying the next layer, be sure the previous layer is set and hardened. When all cracks are filled, texture the surface around the crack to match the surface of the area around it.