Fixing Larger Concrete Cracks
For cracks wider than ½ inch, you may want to consider undercutting the crack to make sure that the crack is wider below the surface than at the surface. This will help ensure that the patching material used will not pop out of the crack when the concrete expands and contracts.
If you’re using pourable concrete grout, only apply ¼ inch of grout per application. You can either fill the crack with sand leaving ¼ inch to the surface of the crack to be filled with the grout or make multiple grout applications that are ¼ inch thick, allowing adequate time for each application to dry. Wet the crack slightly and begin filling it in with grout, applying layers no thicker than ¼ inch. Overfill the crack slightly to compensate for the slight shrinkage the grout will experience as it dries.
If you'll be using vinyl concrete patch material, be sure to follow directions and only mix as much as you can use within the specified time, which is usually less than 20 minutes. Begin by wetting the crack with a spray bottle or hose. Spread the patch material into the crack using a pointing trowel, paying attention to fill the crack in layers no thicker than ¼ inch. Vinyl concrete patch material shrinks as it dries so applying it in layers will allow you distribute a more equal distribution that is less likely to crack. Once your initial layer has had enough time to dry (per package instructions -- usually a couple of hours), proceed with additional applications until the crack is full.
If you choose to use textured caulk, keep in mind it has to be applied to a dry surface. If the crack you're repairing is deeper than 3/8 inch, fill the crack with sand or foam backer board. Cut off the tip of the applicator to a size that matches your crack, not exceeding ¼ inch (refer to caulk manufacturer provided guidelines). In addition to completely filling the crack, apply some overfill to account for shrinkage as the caulk dries.
As you're finishing applications, use a pointing trowel to blend the final patch material with the surrounding concrete to form a good seal of the crack. Once you are done filling the crack, use a small brush, broom or even a block of wood to rub across your patch to help match the consistency of your patch surface with the surface of the original concrete. If the concrete cracks continue to reappear, call in a professional to rule out any larger problems.