Why Do We Need Concrete Repair?
In many cases, especially in Virginia where the soil types range anywhere from dark firm loam to a loose sandy clay, concrete slabs will begin to settle into the soil over time. When soil is improperly compacted voids can begin to form, causing the concrete on top to begin to sink. Over time this can lead to tripping hazards, cracked or damaged concrete, and crumbling of a concrete slab. While most noticeably an aesthetic issue, settled concrete can prove very dangerous to young children and older adults. A 2013 study found that "fall from the same level" incidents were the second highest causes of disabling workplace injuries, showing that trip-and-fall hazards are NOT something to take lightly. When concrete is damaged, it has to be repaired. Luckily for homeowners, there are plenty options available to do just that!
Concrete replacement is the oldest trick in the book for dealing with concrete issues. While other solutions exist for repairing settled but otherwise fine concrete slabs, replacement is the only real option for concrete that is damaged beyond repair. Depening on how handy you are, you can even do it yourself!
The concrete removal process begins with bringing in machines to excavate the deteriorated concrete to the legal specified depth below the existing grade. This is established by state law and can entail a much more involved process than simply destroying the previously laid concrete. Next, the broken concrete is removed to a legal dump site. The exposed soil base is re-compacted in preparation for the re-pour. Replacement begins with placing forms in the replacement area, and slowly pouring the specified inches of concrete over the given area- at an absolute minimum, this should be 4 inches. Expansion and control joints are furnished as needed to help minimize damage from contraction and expansion. Finally, the surface is hand-trowel or brush finished leaving a new piece of concrete resting on the same soil as before!
"Mudjacking" is the process of injecting a hydraulically pressurized slurry mixture underneath sunken concrete slabs. First, a series of 1-2 inch holes are drilled in a compromised section of concrete. Next a mix of soil, portland cement, and other materials are hydraulically pumped into the concrete using the hydraulic pressure to lift the sunken concrete back up to the original height. This material is generally very heavy, weighing between 100-110 pounds per cubic foot of material. While the materials used are somewhat constant across the country, they do differ regionally depending on available filler material (sand, fly ash, different kinds of mud, etc.) The holes are then patched with new cement to complete the job, with the only visual evidence left behind being the new concrete patches over the 1-2 inch holes. While prices differ depending on the scope of the project, a price between $600-$1,000 can generally be expected for most small projects.
Concrete grinding is typically the cheapest option for correcting the height difference between two slabs of concrete, but is also the most visually noticeable. When experiencing a slight height difference between two concrete slabs, grinding can be used to cheaply and quickly maintain a level surface. This is an especially favorable solution to homeowners that are low on money or only worried about the safety of their concrete, not necessarily the appearance. Essentially, the slabs that have not experienced settlement are ground down at an angle to eliminate the height difference between two uneven concrete slabs. Through concrete grinding, the healthy concrete slabs are visually scarred to avoid having to replace or lift the compromised slab. Concrete grinding can be done at the cost of about twenty dollars per linear foot, making it significantly cheaper than most other options. While the cost savings are enticing, the likelihood of future settlement and the increased expense of future repairs from having to damage an unaffected slab make concrete grinding a recommended service only under specific circumstances, such as tree root upheaval issues.
Polyurethane Foam Concrete Lifting
To lift concrete with spray foam, environmentally safe liquid polymer foam is injected through penny-size holes (about 5/8") drilled through a settling concrete slab. The high-density foam expands to 30 times its original size, lifting the concrete while sealing and reinforcing any loose areas in the soil. After approximately 15 minutes the polyurethane material is fully cured and the concrete can be used for whatever its original purpose was, whether it be a pool deck or a factory floor. Following the repair, all of the drilled holes are filled with a cementious grout to match the surrounding concrete, ensuring little visual difference between the corrected slab and the adjacent slabs.
Polyurethane foam weighs about 2 pounds per cubic foot of material. Poly foam is an inert, non-toxic, environmentally safe material that is self-sealing against moisture or other erosive factors, minimizing deterioration over time. The noise is significantly less than any other process, and the time to completion is between 1-2 hours for the majority of projects. By total cost foam lifting is more expensive than grinding, around the same price as mudjacking, and significantly cheaper than concrete replacement.