How to Fix Sinking Cement Blocks

Walk along the sidewalk and check the cement blocks that appear caved in. Pound a wooden stake into the ground next to each block to mark its location. Wrap yellow caution tape along the upper edge of each stake to highlight it in the landscape and keep foot traffic away during the repair process. Clean any accumulated debris or dirt from the sunken blocks with a broom.

Lay a level over each sunken cement block and its neighbor to determine which side is sinking and how high it needs to be raised to bring it in line with the surrounding blocks.

Bore 1 1/2-inch pilot holes into the sunken section of each cement block spaced 12 inches from the edge with a core drill. Space the holes 3 to 8 feet apart, depending on the dimensions of the block.

Add two parts sand, one part Portland cement and one part fly ash to water into a portable mixer until the resultant grout achieves a mortar-like consistency.

Inject the prepared grout mix into a corner hole in the sunken cement block with a concrete pump. Insert the pump’s hose into the hole before pumping the mix into it. Check the pressure gauge on the pump and maintain a steady pressure of between 50 and 100 pounds per square inch during the injection process.

Pump the mix into the hole, while maintaining the required pressure, until the block slowly begins to rise and the hole is almost filled. Insert the hose into the adjacent hole in the cement block and repeat the process to pump the grout mix into it until the block rises.

Check the height and evenness of the cement block with the carpenter’s level and pump more grout into the sunken side to raise it if necessary.

Plug up the drilled holes in the cement block once it is raised to the required height. Add mortar into the remaining gap in the hole and press it down to remove trapped air pockets. Scrape excess mortar from the top of the block and allow it to cure for the time specified on the label’s directions. Repeat the process to raise the remaining marked blocks along the pathway.

Remove the taped wooden stakes once the marked sunken blocks have been raised. Keep foot traffic off of the pathway until the mortar cures.