While concrete can sometimes seem as though it is indestructible, it actually needs maintenance if it’s going to last. Sunken concrete can create a lot of headaches, and once it starts to sink, your liabilities will go up instead, along with your concerns.
What causes concrete to sink?
Concrete is an extremely strong and durable material that’s easy to produce and perfect to build with, but it can also chip, crack and sink. Some of the most common reasons include water intrusion, a weak base that hasn’t been compacted properly, and poor construction. What you can do about it:
Replace the concrete
Replacing the concrete if it has deteriorated or cracked drastically makes more sense than trying to repair it; however, it is essential to note that a new slab will probably not match the concrete surrounding it, both in color and texture. Repairing and replacing tends to be the most expensive option, so before you proceed, it is crucial to address the reason as to why it deteriorated in the first place. If you do not address the issue, the same will happen to your replacement, especially if it was due to the slab’s weight in the first place, or due to the soil, that couldn’t handle or support it.
Use Polyurethane foam injections
Using a closed-cell polymer foam, the injection lifts sunken concrete slabs. Unlike open-cell foams, this closed variation ensures that gas pockets are sealed while preventing any water from being soaked up. The foam is injected through a hole, while a port is fastened mechanically to allow the injection to pass into, through, and below the slab. The great thing about the foam is that it expands in all directions and finds all of the low spots. Once the polyurethane foam reaches underneath the slab, the quick reaction between the expansion of air bubbles in the foam lifts the concrete back up. The foam will retain its volume and shape for an extended period of time, is not subject to erosion or moisture retention, and will not add a significant amount of weight.
Turn to Mud Jacking
A common term for lifting settled or sunken concrete, mud jacking (also referred to as pressure grouting or slab jacking), raises a settled concrete slab by pumping grout through it. This results in the slab being pushed up from below, while holes are drilled through the sunken block to maximise the lift.
Water is then combined with a dense limestone aggregate and is forced into the holes, filling any space that has been created as a result of soil compaction or water erosion. Once the areas are successfully filled, the lifting process will begin. Overall, the procedure is cheaper and requires less time and disruption than replacement, although both require a cure period before the concrete can then be used. Disadvantages include difficulty in cleaning up should the process result in a blowout, and it can also lead to further sinking if the soil underneath is incompetent in any way due to the extra weight.