How to Repair Low Spots in Concrete

Sweep the entire concrete surface to remove any dirt and debris from it.

Wet the concrete surface thoroughly with a garden hose and scrub it vigorously using a stiff-bristled push broom. This removes oil and grease that may interfere with the repair. Clean the entire area of concrete, not just the low areas.

Put on safety glasses. Place the tip of a cold chisel at the edge of the low area and tap the head of it with a hammer to chip away a 1/4-inch deep depression around the entire low area. This gives the concrete patch something to adhere to.

Insert a masonry drill bit into a drill and place the tip of the bit against the concrete in the low area. Drill down at least 1/2 inch. Repeat the process to drill evenly spaced holes over the entire bottom of the low area. This also gives the patching material a base to adhere to.

Pour a powdered mortar mix into a bucket and add the amount of water recommended on the package. Mix the powder in well using a trowel. Add more water a little at a time until the mixture becomes soupy, meaning that it no longer clings to the trowel when you tilt it sideways.

Pour the mixture into the center of the depression and smooth it out with the trowel until it covers the entire low area. Drag a long, wooden board lightly over the low area to smooth out the excess mortar.

Wait 30 minutes to allow the patch to set and then smooth the surface with the back of the trowel, making sure to feather out the edges of the repair so that it blends in with the surrounding concrete. If the surrounding concrete has a rough surface texture, drag the bristles of a broom over the repair lightly to create the same pattern.