How to Raise Sunken Concrete

Bore 1-inch holes through the sunken concrete with a core drill. Space the holes 4 to 8 feet apart along the slab, 2 inches inward from the edges.

Drill a 1-foot-deep hole through each core hole using a pneumatic rock hammer.

Mix equal parts Portland cement and fly ash in a mobile mixer. Add double the amount of sand to this grout mix. Pour water into the mixer to form a thick paste with the consistency of mortar.

Pour the prepared mix into a hydraulic concrete pump set near the sunken concrete slab. This pump has a pressure gauge that determines the pressure at which the mix is being pumped into the holes in the concrete. Extend the hose from the pump and insert it into one of the holes.

Pump the mixture into the hole at a pressure rate of 50 to 100 pounds per square inch. The concrete gradually begins to rise as the mix is pumped into its holes. Remove the hose from the current hole and insert it into another hole. Repeat the process of pumping the mix until the top of the rising concrete is level.

Lay a 4-foot level over the top of the concrete to determine which side is lower than the rest. Insert the hose into the hole along the lower edge and pump mix into it to help it rise. Remove the hose from the hole and set the pump aside when you jack the sunken concrete to the required height.

Prepare mortar in a wheelbarrow. Scoop up some mortar and push it into the holes in the concrete. Press the mortar into each hole using a stick to remove trapped air bubbles. Wipe excess mortar along the top of the slab using a trowel.