Concrete spalling can appear as round or oval depressions along surfaces or seams. Spalling is particularly frequent in cold areas, when de-icing chemicals are used or periodic freeze-thaw cycles harm the concrete. Concrete spalled by chemicals or moisture tends to be dark in color, while concrete damaged by freezing and thawing tends to be white.
Spalling can also be caused by blasting with air guns or other methods of mechanical destruction. This type of damage is commonly found on roads and other public works projects.
Concrete that has spalled should not be used for structural purposes. Instead, it should be removed from affected areas so that traffic can travel safely.
Mechanical spalling is a common issue with concrete driveways and road surfaces. As mentioned, this type of damage can be caused by vehicles driving over the material or being driven over repeatedly. The end result is that parts of the concrete surface are destroyed, leaving rough patches underneath. Mechanical spalling is often more severe than chemical spalling because the force of impact is much greater when vehicles travel over the damaged concrete.
Chemical spalling occurs when substances are put into water that react with the calcium in the concrete, causing chunks to come off the surface. This type of damage is most common in areas where ice storms or salt is used to melt snow from roads.
Flaking is another term for this phenomenon. Spalling occurs on many stone surfaces as a result of moisture in the concrete mixture. Spalling is not only unsightly, but it may also cause foundation or building collapsing. Concrete that has spalled should be cleaned up by a professional to prevent further damage to your property.
Concrete spalling can be caused by a variety of factors, including poor concrete and reinforcing installation, electrochemical (galvanic) interactions between embedded metals inside the concrete matrix, and corrosion of embedded reinforcing steel due to exposure to water and/or chemicals. Over time, all concrete structures will experience some level of spalling. It is important to understand that although this form of damage may appear catastrophic, it does not necessarily mean that your structure is out of compliance with code requirements. Rather, it is an indication that you should conduct further investigation to determine exactly what has occurred.
Spalled areas of concrete can be seen as light or dark depending on how much reinforcement was present in the original mix. Concrete with no reinforcement is called "UNREINED CONCRETE". This type of concrete cannot withstand normal traffic loads and must be replaced. Reinforced concrete, on the other hand, can withstand normal traffic loads and is called "HIGH-GRADE CONCRETE".
High-grade concrete that has spalled should be repaired before it becomes more damaged. The repair should be done so that it matches as closely as possible the original color and texture of the concrete. If too much repair material is used then this could lead to a new problem called "CHECKERBOARDING" where different colors and textures are visible when looking at the surface of the concrete.
A spall is described as material flakes that break off of a bigger solid mass. Concrete spalling is generally caused by rusting of the steel reinforcement contained inside the concrete component. These expansion pressures can induce delamination, cracking, spalling, and breaking off of the concrete. The word "spall" comes from the British language; it means to hit or punch.
Concrete components are exposed to various agents such as air, water, ice, and other concrete components, which over time will cause them to deteriorate. This deterioration includes any changes that may be made necessary as a result of exposure to these agents. For example, concrete exposed to air for a long period of time will turn white because of the loss of pigment within the concrete. This loss of color is called albinization. Other forms of deterioration include corrosion of reinforcing bars within the concrete (if metal rebar is used within the concrete), oxidation of the cement paste, and attack on the polymer fiber fabric in composite concrete structures.
Concrete that has deteriorated beyond repair should be removed from service so that it no longer poses a risk when exposed to additional stress. Failure to remove damaged concrete components could lead to further damage or failure of adjacent sound concrete, since all concrete moves over time under its own weight. Concrete that has been damaged by heavy vehicles or equipment should be replaced before it causes more damage.