Spalling concrete is a common issue for older buildings. It is largely caused by carbonation, a natural deterioration process. This causes the steel bars embedded in the ceiling slab to corrode, which in turn causes the concrete cover to crack and bulge. As the owner, you are responsible for the repair of any spalling concrete in your flat.
How to prevent spalling concrete
Spalling concrete is a surface maintenance problem that occurs in reinforced concrete structures. If attended to immediately, the building’s structural integrity will not be affected.
Here’s how spalling concrete can be prevented:
Paint ceilings regularly
Paint protects your ceiling and helps to prevent carbonation. Ideally, you should paint your ceiling regularly.
Seal cracks/ holes properly
Check your ceiling regularly for any holes or cracks. These should be sealed immediately to prevent moisture and carbon dioxide from entering the concrete. Similarly, seal up any holes drilled into the ceiling that are no longer in use (e.g. holes left after a ceiling fixture is removed).
Ensure sufficient ventilation
A humid environment will speed up carbonation. To reduce the humidity in moisture-prone areas such as the kitchen, toilet, and bathroom, open the windows, vents, or doors when the areas are not in use.
Repairing spalling concrete
With regular maintenance, spalling concrete within HDB flats will usually be minor and can be easy repaired. However, if the spalling concrete is left unattended over a long period, it will spread to a bigger area and weaken the building structure.
The steps below briefly show how spalling concrete is repaired. For more details, please watch this video.
Step 1: Remove the spalled concrete
spalling concrete repair 1
Remove the concrete at the spalled areas to expose the corroded steel bars
Step 2: Clean and paint the corroded steel bars
spalling concrete repair 2
- Scrape and clean the exposed steel bars and use a wire brush to remove any rust
- Apply 2 coats of anti-rust paint to the steel bars
Step 3: Patch the hacked area
spalling concrete repair 3
- Apply a bonding agent to the affected surface to ensure proper adhesion
- Patch the hacked area using polymer modified cement mortar
Step 4: Paint the area
spalling concrete repair 4
- Paint over the patched area to match the rest of your ceiling
Removal of Loose Concrete on Ceiling
While waiting for the repairs, do remove any loose spalling concrete to prevent injury to your family members.
STEP 1 :
- You should wear a pair of protective gloves, and prepare a hammer and chisel to remove the loose concrete
- You can replace the chisel with a long flat point screw driver
STEP 2 :
- Cover the floor and protect the surroundings with thick cardboard
- Secure the ladder and climb up to remove the loosen concrete.
- Hold the affected portion of concrete and bring it down carefully
STEP 3 :
- Collect the concrete debris and dispose it safely at the bin centre
SPALLING CONCRETE REPAIR
We specialise in the professional repair of spalling concrete issues.
Spalling Concrete Prevention
Spalling Concrete Inspection
Perform initial inspection to assess condition of spalling concrete on ceilings and walls
Employ professional standards to spalling concrete repair method to preserve safety and structural integrity
Perform regular maintenance of compromised concrete surfaces to prevent onset of spalling concrete issues
SPALLING CONCRETE REPAIR
About Spalling Concrete
Especially in older buildings, spalling concrete is a prevalent surface maintenance issue. It is suggested that repair be done as soon as spalling concrete is observed as it can cause passerby risk.
A natural deterioration method called carbonation is mainly triggered by spalling concrete. This triggers corroding of the steel bars inserted in the ceiling slab, causing cracking and bulging of the concrete cover.
In reinforced concrete structures, spalling concrete is usually a surface maintenance issue. It does not impact the structural integrity of the construction if attended to immediately.
Spalls may appear as the rebar was exposed and humidity and water started rusting the rebar or as the concrete joints were improperly constructed. The concrete extends as the weather changes, causing it to spin, leading to further deterioration. One method that can avoid spilling of concrete is to apply a healthy water sealant to the completed surface to avoid water from entering the concrete.
Spalls can also be avoided if the concrete is carefully managed and suitable techniques are used when poured, such as providing adequate concrete cover (embedding) of the rebar and placing joints at the right locations and the right distances. Always pay special attention to the edges and corners of exposed concrete as specified by the structural engineer to ensure adequate concrete cover. The concrete mix is another important factor to consider, as the surplus water content can also lead to spalling.
- Regularly paint walls as paint protects your ceiling and helps avoid carbonation. Ideally, your ceiling should be painted frequently.
- Seal any visible cracks and holes found on surfaces properly
- Check your ceiling for any holes or cracks regularly. To avoid moisture and carbon dioxide from entering the concrete, these should be closed instantly. Similarly, seal any drilled holes into the roof that are no longer in use (e.g. holes left after removal of a ceiling fixture).
- Ensure sufficient ventilation in the indoor room as higher humidity will promote carbonation. Open the windows, vents, or doors when the places are not in use to decrease humidity in moisture-prone regions such as the kitchen, toilet, and bathroom.
Spalling Concrete Repair
Usually, spalling concrete within HDB flats will be minor with periodic maintenance and can be easily repaired. If the spalling concrete is left unattended for a long time, however, it will spread to a larger area and weaken the structure of the building.
The steps below show briefly how to repair spalling concrete. Do remove any loose spalling concrete while waiting for the repairs to avoid injury to inhabitants.
Step 1: Remove the spalled concrete
Remove the concrete from the spalled regions to expose the corroded steel bars.
Step 2: Remove rust from corroded steel bars
Scrape and clean the exposed steel bars and use a wire brush to remove any visible rust on all surfaces. Next, apply two coats of anti-rust oil all around the exposed steel bars.
Step 3: Patch the hacked region
Apply a bonding agent to the impacted surface to guarantee adequate adhesion.
Additional Tips for Repairing Spalling Concrete
- Spalling remedies differ by issue severity, concrete structure type and place, and other variables.
- If the spalling damage is shallower than 1/3 of the size of the concrete, a surface repair can generally be done to the concrete. If the damage exceeds 1/3 of the depth, steel bars may need to be installed and a complete restoration of the depth may be needed.
- Corroded rebar must be washed at the start of the restoration phase owing to exposure. Once the rebar is carefully washed (generally with a wire brush) and all corrosion is removed, a protective rust inhibitor layer should be provided to the rebar to minimise future corrosion.
- Damage can be repaired with a cemented overlay on driveways, walkways, and other horizontal surfaces. A waterproofing membrane should be introduced after the complete set of the overlay to avoid recurrence of spalling.
- Patching can be a random or localised damage repair alternative. Patches should stretch beyond the spalled fields by at least 4 inches. The surface in the patch area can be saw-cut to help contain and secure the patch for best results.
- Patching surfaces should be free of all debris and fine particles and should be totally dry before applying patching material. It is best to provide tooth for better bonding if the ancient concrete surface is rough. The finest patching materials are Portland cement or epoxy-based mortar and should be blended as directed by the manufacturer immediately prior to implementation.
- Repair materials should have a coefficient of expansion compared to the initial concrete.
- Any repaired joints must allow the concrete slab to expand.
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