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 will begin to settle into the soil over time. This is caused by the weight of a concrete slab compacting the loose soil underneath it until it is no longer level with the adjacent slabs. In the long term this can lead to tripping hazards, cracked or damaged concrete, and eventually crumbling. While at first this may seem like a minor issue that deals primarily with aesthetics, it is important to remember that the ADA (Americans with Disabilities Act) has very clear regulations for the safety standards of concrete. Failing to keep in compliance with these regulations can lead to heavy fines and the potential for a lawsuit. While small cracks or abrasions can be repaired by the property owner or manager, this will not be the case for most concrete settlement and professional help will be needed. If outside help is required, you need to know the best options for keeping your property safe, attractive, and valuable.
One of the first thoughts a property owner will have when experiencing concrete concerns is simply to remove the concrete and have it replaced. While sometimes necessary in extreme circumstances, this will not resolve problems related to soil washout under the concrete slab, poorly compacted fill soil, or soil moisture content changes- all of which will increase the likelihood of future settlement on the new slabs. Another factor to take into consideration is the cost. Concrete replacement can run anywhere from twelve dollars per square foot of placement to twenty dollars, making it the most expensive option.
The concrete removal process begins with bringing in multiple heavy 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. Then there must be a complete removal of the broken concrete to a legal dump site. The exposed base of soil is re-compacted for the replacement of concrete. Replacement begins with forming and pouring the specified inches of concrete over the given area following specifications and reinforcement from the heavy machines under the supervision of multiple crew members. Expansion and control joints will be furnished as needed. Finally, the surface is hand-trowel or brush finished leaving a new piece of concrete resting on the same soil as before.
‘Mudjacking’ is a colloquial term used to describe an alternate process to polyurethane foam concrete lifting. While cheaper than replacement and foam jacking, mudjacking comes with a few drawbacks.
The process begins with a series of holes drilled in a settled slab of concrete. Then a mix of soil, portland cement, and other materials is hydraulically pumped through 1-5/8″ holes in the concrete using the hydraulic pressure to lift the sunken concrete back up to the original height. The holes are then patched with new cement to complete the job.
While mudjacking can solve the problem of concrete settlement temporarily, the soil will still be at risk for future settling from the sheer weight of the new materials that had been added to the substrate. The mixture used for mudjacking is usually incredibly heavy, having an average weight of 100-110 lbs. per cubic foot of material. As a result, the soil often does not stabilize 100%, and could sink again over time; the solution to this problem is typically to drill more holes for a greater cover. Though cheaper than polyurethane foam lifting, the applications for mudjacking are significantly less reliable than it’s more advanced counterpart.
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. Essentially, the slabs that have not experienced settlement are ground down at an angle to appear level with the settled slabs. This will not solve the problem of concrete settling, however, and over time the slab that was settling will continue to sink lower into the soil. 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 can be enticing, there are few applications of concrete grinding that are truly the best option when considering the likelihood of continued settlement and the damage that has to be done to perfectly fine concrete slabs to accomplish an even surface.
Polyurethane Foam Concrete Lifting
To lift concrete with spray foam, environmentally safe liquid polymer foam is injected through penny-size holes drilled through a settling concrete slab. The high-density foam expands to 30 times its original size, lifting the concrete while sealing and reinforcing the loose 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 those holes are filled with a cementious grout to match the surrounding concrete, meaning it will continue to match the surrounding concrete.
Unlike mudjacking mixes, polyurethane foam only weighs about 2 pounds per cubic foot of material. Poly foam is an inert, non-toxic, environmentally safe material. It is also self-sealing against moisture or other erosive factors due to being a closed-cell compound, meaning that there will be no deterioration over time. Additionally, spray foam injection systems only use a 5/8″ hole for an injection port (about the size of a penny). The noise is significantly less than any other process, and the time to completion is between 1-2 hours for the majority of projects. This leaves the customer with a solution to settled concrete that minimizes downtime, cost, and inconvenience, while maximizing the lifespan of the slab and the attractiveness of the final product. By total cost foam lifting is more expensive than grinding, slightly more expensive on average than mudjacking, and significantly cheaper than concrete replacement.