Concrete cracks are caused by sideways expansion, poor drainage conditions or settling soil beneath the concrete. If your concrete is the same height on both sides of the crack, you can fix it yourself. But you have to enlarge the crack (Photo 1). Then power-wash the area and squeegee off the excess water before applying the filler. Fill with a polymer-modified cement such as Quikrete concrete resurfacer No. 1131. Our crack was wide and deep, so we chiseled out the entire opening and refilled it (Photos 2 and 3). However, if one side of the crack is lower, call an expert to diagnose and fix the underlying soil/drainage problem. Then either replace the sunken portion or call a mud-jacking company to raise it.
Chip out the cut concrete to get a fresh surface so the new concrete can bond to it.
Establish a solid base for the resurfacer by filling the opening with concrete and letting it dry (see Photo 3).
Add water to the resurfacer mix to get the consistency of pancake batter. Then fill the remainder of the groove and smooth it over.