Everything You Need to Know About Spalling Concrete

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17 March 2022 - 15:35, by , in Structural strengthening, No comments

A report recently came out about an injured boy who was struck by a spalling concrete slab that fell from the ceiling of their housing board flat due to wear and tear. According to Syasha Danial Alissa, her son was shooting water at the ceiling of their 45-year-old apartment when the concrete fell on his back. Natural wear and tear happens to older buildings, such as the family’s home, as well as moisture-prone areas like the kitchen and bathroom, where humidity causes concrete to crumble.

It is concerning what happened to Syasha and her son, and it may also happen to you and your family if your home is not properly maintained. Thus, the HDB encourages homeowners to be on the lookout for signs of spalling concrete and to have them repaired as soon as possible. What are the signs that you need professional assistance? Here is a guide on all you need to know about spalling concrete so that you can keep an eye on your home.

What Is Spalling Concrete?

As mentioned earlier, older buildings are often plagued by spalling concrete. What happens is that the steel bar, embedded in the ceiling slab, corrodes over time due to carbonation, a natural deterioration process. As carbon dioxide penetrates the concrete and interacts with water, it causes the steel bar to rust and expands in volume. As a result, the concrete surface of the ceiling peels, cracks, and eventually breaks off in a process called spalling or spalling concrete.

Bathrooms and kitchens, which have a high moisture content, are common places to experience this issue. Spalling concrete does not affect a building’s structural integrity if it is immediately addressed. If not, it may spread and weaken the building structure and may lead to severe damage to your home and or accidents. That being said, it is important to look for the warning signs and the causes of spalling concrete.

What Causes Spalling Concrete?

Spalling concrete slabs are usually caused by carbonation and extreme moisture. Nevertheless, a concrete surface can break off in various ways. Some of them are:

  • Corrosion of Steel Bar
    As mentioned, earlier, as water permeates the concrete surface, it causes the steel bar to rust and occupies more space than its original rebar, which results in pressure buildup and consequent spalling.
  • Freeze-Thaw Cycle
    This is a weathering erosion process, commonly in cold areas where ice can form. Whenever temperatures drop, water can freeze into ice when it seeps into the concrete. Ice may crack when it expands. The ice melts when the temperature rises, causing further damage to the interior. Concrete slabs spall as a result. As the temperature in Singapore is not cold enough to create freezing conditions, this does not happen here.
  • An Alkali-Silica Reaction
    This happens as a reaction between the reactive silica in concrete aggregates and alkaline cement pastes, which results in increased pressure in the concrete, swelling, and, eventually, spalling.

How to Spot Concrete Slabs?

In order to detect spalling concrete slabs early, keep an eye out for flaking, chipping, or missing large chunks of concrete from the surface, as well as exposed coarse rocky concrete aggregate. Spalling, however, can be difficult to detect by physical signs alone. Chemical and physical processes within concrete cause concrete to spall. Mixing methods and environmental factors can also contribute to concrete spalling. For this reason, it is best to consult a professional if you see any of the visual signs mentioned above.

How to Prevent Concrete From Spalling?

Even if you do not notice early signs of spalling concrete, take precautionary steps to avoid an incident. A few suggestions include:

  • Paint Ceiling Regularly
    Painting surfaces can slow down the carbonation process and avoid moisture from seeping into the concrete. You should paint your ceiling every three to five years, using anti-carbonation or good quality paint.
  • Seal Holes and Cracks Properly
    Cracks and holes allow moisture to enter the concrete surface. Look for them and seal them as soon as possible. If you discover a drilled hole that is no longer in use, such as holes left from fixtures, seal them up as well.
  • Provide Sufficient Ventilation
    Humidity speeds up the carbonation process. So, when moisture-prone areas like the kitchen and bathroom are not used, open the windows, vents, or doors in the area to provide proper ventilation.

How to Repair Spalling Concrete?

Below are the steps on how to fix a case of spalling concrete in your home:

  1. The corroded steel bar will be exposed after removing the spalled concrete with care.
  2. Corroded steel bars should be cleaned by removing all the rust. A two-coat anti-rust paint should then be applied.
  3. The affected surface should be treated with a bonding agent. The patch should then be made from polymer modified cement mortar.
  4. Match the rest of the surface to the repaired area.

Even so, it is still advisable to seek professional assistance since this type of issue can be extremely challenging to fix and is considered dangerous. Because of this, there is a high risk of further damage to your house if it is not done correctly.


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