Concrete spalling is the peeling of concrete surfaces that leaves reinforcing steel exposed.
The peeling can affect sizeable sections of the concrete slab. Concrete spalling is caused by either acidic chemicals or poor quality concrete. Spalled concrete shows in form of rust stains, cracked, flaked or bubbling concrete. Concrete spalling can be more common in some climates than others, such as those with high humidity, precipitation or very cold winters like the American northern states. It is not unusual for concrete to spall naturally, even if exposed to these conditions for an extended period of time. The most common concrete spalling problem is caused by the use of low quality or poorly mixed concrete, which can be more susceptible to damage from corrosive materials.
If spalling damages are left untreated, it will lead to structural weakness. Repairing spalling concrete can be a relatively simple process. If it is a small area, the easiest thing to do would be to chisel out the loose parts and replace them with new material. However, if there are larger areas or deep cracks, you might need to use an epoxy injection system instead of just filling in the crack with concrete. If the repair work gets technical, seek expert advice. Concrete spalling may also indicate that the concrete has been exposed for too long to weather elements without being properly protected from those elements. In this case, complete replacement of the damaged area may be necessary.
Below are some common causes of concrete spalling. Avoid these mistakes to prevent spalling.
If the concrete placement does not provide adequate cover around the embedded reinforcing steel, the shallow cover will easily lead to spalling.
Use of poorly mixed concrete element or failure to properly cover the steel reinforcing a concrete structure. With time especially in heavy structures, the badly prepared mix becomes weakened concrete.
For structures with joints, improper construction of the joints will quickly lead to concrete peeling or shedding off concrete cover around the joint area.
Spalled concrete is most commonly found in areas where water gets trapped within the concrete for an extended period of time. Areas that are more likely to have problems with this include parking lots, sidewalks, roadways, driveways, garages, and other places where people walk frequently. It isn't uncommon to find small amounts of concrete spalling on vertical surfaces either due to acid rain or because they were poured at a low height without reinforcement bars.
Concrete spalling can manifest as a number of different problems, but the common thread is peeling and flaking away from the concrete. Spalling can occur in a number of different problems with concrete, but the most common is from expansive soils. Spalling often looks like small chips or flaking on the surface of the area affected. The main symptom of spalling is material appearance, although it can be an indicator that larger issues are developing beneath the surface. The most visible type of spalling is caused by improper surface preparation prior to applying new paint or other decorative treatments. Rust and corrosion hidden beneath this thin layer often form around rocker panel edges where lack of wheel well clearance causes them to rust from the inside out.
Concrete cancer is often referred to as spalling, but while they are similar in appearance, there are different causes. The way that each one develops can vary widely, but both types of damage tend to be caused by moisture leaking into the concrete and reacting negatively. What causes this reaction can have a huge effect on how it manifests itself. For example, many forms of concrete peeling occur because of poor quality or poorly mixed concrete rather than from an issue with the substrate beneath it. In situations like these, the only real solution is to replace all of the concrete affected by it. It isn't always necessary for replacement when concrete cancer occurs, though, since sometimes applying a seal over existing surfaces is enough to resolve the problem.
Concrete cancer is a form of spalling that occurs because of reactions to moisture or other liquids. Concrete cancer often looks like large flaking and pockmarks on the surface of the concrete, but different circumstances cause many different variations. The cement reacts with carbon dioxide in the air around it to slowly turn into calcium carbonate. When this happens, large amounts of calcium hydroxide and other chemicals leak out and slowly damage nearby surfaces' appearance and structural integrity over time.
If minor spalling is the only issue, concrete repair is possible with a mixture of paint and sealant. If you choose this route, make sure to read the instructions on each container carefully and apply it in thin layers so that you can build up several coats instead of trying to get complete coverage on the first try.
Bear in mind that in the concrete repairs process, it's is critical that the repair material you use is compatible with the material used to make the original concrete surface.
If the spalling is in an area that receives a lot of pedestrians or vehicular traffic, it may be possible to fix it by applying more concrete over the top of the existing surface. This method requires complete removal of the old concrete followed by additional reinforcement bars and new concrete. It isn't always necessary to replace all of the concrete when working on repairing spalling problems, though, especially in areas where people aren't likely to walk or park heavy vehicles.
In some cases, people will even use paint designed for outdoor concrete as patching material to cover up minor spalling issues because it can provide a similar level of moisture protection without requiring any other changes. It's important that you read the instructions carefully before trying this, though, since some concrete elements in repair material may not be compatible with the affected area.To fix concrete cancer, you'll need a combination of a sealant and a mixture of sand and cement. The amount of each ingredient varies depending on the size of the damaged area being treated. Spread the mixture over the affected surface using a trowel until it is just shy of being level with it after drying completely.
When choosing between these two methods, keep in mind that applying paint to your existing surface won't add any extra integrative strength. Adding new concrete to replace old spalling surfaces increases overall durability. However, when people choose to replace all problematic areas when fixing spalling problems, they often have more aesthetically pleasing results and make sure their concrete can hold up for years to come without any other repairs. Pouring a concrete slab floor? The Australian Government's Your Home website has some handy things to guarantee a top job.