Sometimes concrete tilts or sinks, even as soon as five years after being installed. As a result, concrete lifting is required to fix the problem. Luckily it is possible to do this yourself.
Understanding Why the Concrete Sank
Before beginning any concrete lifting yourself, it is important to understand why the concrete has sunk in the first place to make sure the sinking doesn't happen again. In most cases, the concrete has sunk because the dirt that was placed underneath it was not properly compacted during installation. Areas where this happens the most are on a driveway, a sidewalk, or a garage slab.
The Concrete Lifting Process
General Procedure Followed by Professionals
Someone more skilled can use this method. Drill 2-inch holes into the sunken concrete and pour a mixture of fly ash, sand, water, and cement into the holes with a pump that produces 50 to 100 pounds of pressure. The mixture, which is like thick mortar, easily raises the sunken slab. Not much pressure is required to do this since concrete slabs don't weight too much. The average 4-inch thick concrete slab only weighs 1/3 of a pound per square inch.
A Good Solution for DIYers
Sand also has air in it, but it may be a better option for the do-it-yourselfer trying to raise concrete. If it is done correctly. Smaller sections of sunken concrete can be cut out using a wet saw and then lifted out with a crowbar. Fill in the holes with sand and compact it with a tamping machine before replacing the sunken section. Pea gravel can sometimes be used instead of or even in conjunction with sand which fills in the spaces between the pea gravel.
Concrete Lifting with a Small Sledge Hammer, Brick Chisel, and Drill
This is another method for doing it yourself. Use the brick chisel and sledgehammer to undercut any edges of the sunken concrete as necessary. With a concrete drill or masonry bit, drill small holes into the sunken area and slowly pour a thin mixture of cement into the holes. Allow it to stand for half an hour so that it can settle. Pour more cement if necessary. and allow it to settle. Smooth the surface with a trowel and let the concrete cure for 24 to 48 hours.
Lifting Larger Areas of Concrete
To lift larger areas of concrete, you'll need help. Begin by removing any cracked pieces. Clean the area with water from a hose, and then build a wooden form a couple of inches higher than the existing sunken concrete so that it matches the height of the concrete that hasn't sunk. Fill any holes with tamped sand. Lay the new concrete and finish it with a trowel.
Replacing the Shifted or Non-compacted Dirt Yourself
As mentioned earlier in this article, concrete usually tilts or sinks because the uncompacted dirt underneath it has shifted, and is no longer providing a solid base for the concrete slab. The logical solution for the do-it-yourselfer is to dig a hole alongside the sunken slabs and shovel dirt into the hole. This will not successfully lift the concrete because there's too much air in the dirt. As the dirt gets moved, more air space is placed around each dirt particle making it fluffier, even though it doesn't look that way. The freshly installed dirt may temporarily raise the sunken concrete, but over time the concrete will shift again as the air leaves the soil and it settles back down again.