What causes concrete to spall?

There are several reasons why chipping occurs, including freeze-thaw cycles, the expansive effects of the alkaline silica reaction, or exposure to fire. However, the most common cause of chipping is corrosion of embedded steel reinforcing bars or steel sections. If you address a chipping problem early on, it's easy to fix. After all, detachment begins as a purely aesthetic imperfection caused by cold weather.

When the temperature drops below the freezing point, moisture in the concrete tends to expand, creating internal pressure. Over the course of a winter, or over the years, as the internal pressure increases and decreases, the surface layer of the concrete tightens, causing chipping. One of the many reasons why concrete chipping occurs is because of the natural process called carbonation. The water will immediately seep into the concrete and cause other elements, especially reinforcing bars embedded in the concrete, to corrode.

Therefore, it creates bumps and cracks on the concrete surface. Steel reinforcing bars are often used in concrete to provide durability. In addition, steel that is of poor quality can cause chipping. This is most commonly found along the thin outer edge, where there is less aggregate to bond the concrete together.

Antifreeze chemicals only aggravate already stressed concrete by allowing more water to migrate to the concrete, increasing the size and depth of chipping failures when freezing occurs. A contractor should pay special attention to the corners and edges of exposed concrete when dealing with concrete chipping. Because concrete acts as an electrolyte and wire ties provide the metal connection and support of the chair, it can cause corrosion of the embedded metal, causing chipping, cracking, and delamination. As a result, the concrete structure has a reduced asset value, may need repair or complete replacement.

Concrete can develop strong thermal gradients when exposed to the sun because it has a low thermal conductivity. When moisture in concrete freezes, these air cells relieve internal pressure by providing microscopic chambers for water expansion as it freezes. During firefighting operations, water poured onto the heated concrete surface also causes chipping. Concrete has enormous versatility and is used for a variety of different projects, from superstructures to pool patios.

The exceptional durability of concrete is the main reason people and companies use it in construction projects. Concrete can flaking for a wide range of reasons, and the damage is often due to a combination of factors. Concrete chipping is one of the most common problems in which part of the surface breaks, peels off and chips. And because it's a finished concrete surface, masons push the stones down and trowel the concrete.

Here, the top layer of concrete comes off, leaving the surface uneven and pitted while exposing the aggregate below.

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