A report came out recently about a boy who was injured after getting hit by a spalling concrete slab that fell from the ceiling of their housing board flat due to wear and tear. Syasha Danial Alissa shared in a Facebook post that the concrete fell on her son’s back, who was shooting water at the ceiling of their 45-year old flat. According to the HDB, natural wear and tear happens to older buildings, such as the family’s home, and more frequently in moisture-prone areas like the kitchen and bathroom, where the humidity causes spalling concrete.
What happened to Syasha and her son is concerning, and may happen to you and your family if your home is not physically well maintained. So, the HDB encourages homeowners to look out for signs of spalling concrete and have them repaired immediately by professionals. But how would you know when to call for professional help? To help you monitor your home, here is a guide on everything you need to know about spalling concrete.
What Is Spalling Concrete?
As mentioned earlier, spalling concrete is a common issue with older buildings. 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.
This is a common problem in places with high moisture, such as the bathroom and kitchen. Though, spalling concrete does not affect the building’s structural integrity, for so long as it is attended to immediately. 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?
In general, carbonation and extreme moisture cause the formation of spalling concrete slabs. Still, there are various ways on how a concrete surface can break off. Here are some of them:
- 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. If water seeps into the concrete, it can freeze into ice when the temperature drops. As the ice expands, it may cause cracks on the surface. Subsequently, when the temperature rises, the ice melts to water, which causes further damage to the interior. This process continues until it forms spalling concrete slabs. This doesn’t happen in Singapore as the temperature here doesn’t have the capability to create freezing conditions. - 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?
For early detection of potential spalling concrete slabs, look out for any flaking, chipping, or missing large chunks from the concrete surface, and exposed coarse rocky concrete aggregate. However, it is hard to pinpoint problems such as spalling by mere physical signs. Concrete spalling is a result of chemical and physical process within the concrete itself. It may also be caused by how the concrete was mixed or environmental conditions. That is why if you notice any of the visual signs mentioned, it is best to consult a professional as soon as possible.
How to Prevent Concrete From Spalling?
Even if you do not notice early signs of spalling concrete, take precautionary steps to prevent the incident from happening. Here are some of the ways to avoid such problems:
- Paint Ceiling Regularly
Painting surfaces can slow down the carbonation process and avoid moisture from seeping into the concrete. Paint your ceiling regularly- 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. Check for any of them and seal them immediately. Also, if you find 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?
If you did confirm a case of spalling concrete in your home, here are the steps on how it can be fixed:
- Remove the spalled concrete with much care to expose the corroded steel bar.
- Clean the corroded steel bar, removing all the rust. Then, apply two coats of anti-rust paint on it.
- Apply a bonding agent to the affected surface for adhesion. Afterwards, patch the area using polymer modified cement mortar.
- Paint the repaired area, matching the rest of the surface.
However, it is still advisable to call for professional help as this type of problem can be really challenging to fix and it is considered high risk work. Hence, it poses high risk and may lead to further damage to your house if not done correctly.
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