If you have a concrete walkway that is sinking, it could pose as a dangerous safety hazard. Anyone could trip and hurt themselves if the walkway is uneven. Most walkways sink due to the same thing--the dirt underneath the sidewalk was not packed down correctly. Soil shrinking could be another reason for a sinking concrete walkway. A concrete walkway does not have to be torn apart and poured again to fix this problem. There is a new method used to fix sinking concrete walkways, called mud-jacking, or slab-jacking. The mud-jacking process will make sinking concrete walkways level.
Warning: This is not the average job for you to try to complete on your own, unless you are knowledgeable in concrete mixtures and machinery.
Step 1 – Protection
As with any project, you will need to have the proper protection from dust and debris. Put on your face mask and safety goggles. This will prevent any pieces from hitting you in the eyes, as well as prevent dust inhalation.
Step 2 – Drilling the Holes in the Concrete
Use your masonry drill to drill 2 holes into the sunken concrete. You may have to drill a couple more holes, depending on the size of the sunken concrete. Drill holes that are 1 ½ to 2 inches in size.
Step 3 – Concrete Injection (Mud-jacking)
Put the grout pump nozzle into the hole and allow the mixture of pond sand and concrete to fill into the concrete walkway until it starts leveling. The pump should be able to produce anywhere from 50 to 100 pounds of pressure. As the mixture is pumped into the ground the pressure increases from the grout pump. This will cause the sunken slab to rise. The concrete slab will not require that much pressure to lift, since the slabs do not weigh much. When the sidewalk appears level, remove the hose.
Step 4 – Raising the Concrete
An alternative method for slab-jacking is to raise the concrete yourself. This should only be done if the sunken area is small. A pick used for prying or digging can be used to raise the concrete. Use the flat end of the pick to pry the slab up, just enough to add the concrete filler underneath it. Sand can be used as the filler, but gravel would probably pack in better. Concrete used as a filler may get squeezed right back out, if the pressure of the slab is too great. Lower the slab back onto the filler.
Step 5 – Finishing the Job
Use a concrete mixture to cover the holes you drilled in the walkway slab earlier. Once the holes have been covered up, use the putty knife to smooth them out. When you are done, the sidewalk should be nice and even, with no noticeable holes.