Most individuals have never heard of the term slabjacking, a common phrase known to those who work with concrete. Slabjacking is a method of repair for concrete when the material has sunken down into the ground. When concrete begins to sink, the problem is most likely with how the concrete was poured on fill dirt that was poorly compacted. Erosion and soil shrinkage can also occur and can lead to concrete sinking.

An individual who is experienced in slabjacking will be able to provide you with the service needed to repair your concreate. The slab can be floated back into position by using sand, cement and additional additives that are placed underneath the concreate slab.

Slabjacking Process

The process of slabjacking is done with a pattern of holes. Holes are drilled from 1 and ½ inches to 2 inches onto the slab that has sunken down. A mixture of grout is then applied with low pressure and pushed under the slab by using a hose that is two inches in size. A nozzle is attached to the hose that fits into the holes that were drilled onto the concrete. As the cavities are filled, the grout will be pressurized and this will raise the slab hydraulically. The desired height is achieved and your concrete slab repaired. The grout will consist of water, cement, sand and other additives to help prevent any shrinkage from taking place.

Drilling the Holes

The size of the slab will determine the number of holes needed to be made during the drilling process. A smaller slab such as one used in a sidewalk will only require one to two holes for pumping grout. A larger slab will need three holes which are arranged in a triangle pattern. The spacing and placement of the holes will be related to thickness of the slab as well as amount of grout needed for raising the concrete slab.

Grout Pumping

Once the holes are set, the grout will need to be mixed and pumped in. The grout should be pumped in at the lowest point of the slab so that the slab will be lifted correctly. When you need massive lifting capabilities, a heavier grout will be used for pressurization. More holes may be needed as support to help fill the slab so it will rise fully. These additional holes will be filled with fluid grout rather than dense material to ensure quality flow.

Patching the Drilled Holes

Once the grout has been added to the slab via the drilled holes and the slab is lifted, then the holes will need to be patched up. This is the last step in the process of slabjacking. The grout that remains in the drilled holes is removed. The holes are filled with a mortar mix that is stiff in consistency and the surface will be spread smooth. There is an option to drill cores instead of holes so that the cores can be glued back in place to make the patch job less noticeable.

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Meet Lance Davis


Lance Davis is a third generation Concrete Contractor with over 10+ years experience in concrete repair and slabjacking. His company Davis & Sons Concrete has proudly served all of North Central Illinois, Rockford and the outer suburbs - and he would love to hear from you!

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