How to Repair the Sunken Area of a Concrete Walkway

Measure the length of the sunken area with measuring tape. Use chalk to mark drill holes set 12 inches in from both sides and spaced evenly apart by 1 to 3 feet along the length of the walkway.

Use a core drill with a 1 1/2-inch bit to drill holes through the sunken slab. Wear eye, ear and mouth protection when cutting through concrete or asphalt.

Thread a hose with a 1 1/2-inch nozzle through the lowest-lying drill hole. Connect the open end of the hose to a slabjacking pump.

Stir slabjacking grout with a wooden stirrer. In addition to the standard components of cement, sand and water, additional ingredients are included so the grout won’t shrink over time. Fill the pump with grout using a scooper.

Turn the pump on and fill the cavity beneath the pavement. Turn the machine off and move the nozzle to the next hole. Continue filling each drill hole with grout.

Return the hose to the first hole and pump more grout into the foundation. Once the cavity is filled, the pump pressurizes the grout, which will slowly lift the concrete. Move the hose to the next hole after raising the slab about an inch. Continue this process until the sidewalk reaches its correct height.

Wipe off any excess grout with a moist cloth. Use a putty knife to pack stiff mortar into the drill holes. Cut the mortar off at the surface for a clean finish. Do not feather it out around the edges. Wait a full day for the grout to dry before opening the walkway to foot traffic.