Concrete spalling is a common problem where part of the surface peels, breaks or flakes off. Also known as spalling, it is the result of a weak surface that is susceptible to damage. The term “spalling” is used to describe areas of concrete that have cracked and become detached from the substrate. There are a number of reasons why spalling occurs, including freeze-thaw cycles, the expansive effects of the alkali-silica reaction or exposure to fire.
However, the most common cause of spalling is corrosion of embedded steel reinforcing bars or steel sections. Corroded steel can expand up to ten times its original volume, exerting stresses on the surrounding concrete. Finished concrete is usually porous and can absorb rainwater. Spalling occurs on exterior slabs when water trapped in the concrete undergoes multiple freezes and thaws. When the water freezes, it expands by about 9%, which creates enormous pressure inside the slab.
One of the many reasons why concrete spalling occurs is the natural process called carbonation. Water immediately seeps into the concrete and causes corrosion of other elements, especially the reinforcement bars embedded in the concrete. It therefore creates bulges and cracks on the surface of the concrete. Steel reinforcement bars are often used in concrete to provide durability. In addition, poor quality steel can cause spalling.
This is a slow process that occurs when carbon dioxide from the air enters the concrete and is counteracted by hydroxides, such as calcium hydroxide, to form carbonates. Thus, spalling after a period of more than fifty years is due to the carbonation process. Acids from acid rain react with the surface of the structure and can cause spalling in high quality concrete. Chemical attack can also deteriorate concrete, exposure of concrete to different environmental conditions such as acid rain have serial effects on concrete. In addition, some of the common triggers of concrete spalling are related to construction defects. These can be inadequate preparation of reinforcing steel, incompatible supporting metals, metal bars placed too close to the surface, stress fractures due to excessive weight, insufficient concrete cover or poorly poured concrete. The best time to deal with spalling is when the concrete is first poured, taking measures to prevent it from occurring.
It is important to make sure that the coefficient of thermal expansion of the old concrete and the new filler material is the same. When exposed to extreme temperatures, either over time or suddenly, the surface becomes much hotter than the concrete beneath it. When the hydraulic pressure of the expanding ice exceeds the tensile strength of the concrete, the concrete scales loosen, exposing the aggregates. Therefore, protecting the concrete in time can prevent these dangers and also avoid having to replace it later. HomeQuicks describes some of the main causes of spalling and ways to prevent it. Concrete spalling can injure people or damage objects underneath, thus increasing risk to people's lives. These cracks, in turn, will pave way for atmosphere to further react with internal environment of concrete thus increasing danger of failure. It can be applied to both dry and wet concrete with a brush, sprayer, roller or other applicator.
The environment in which the concrete element is placed has a significant effect on its performance in relation to durability. In conclusion, understanding why spalling occurs and how it can be prevented is essential for ensuring that your structure remains safe and sound for years to come.