Have you heard of concrete spalling but are not too sure what it means?
We’ll break down everything you need to know about this unfortunate type of damage to concrete.
What is concrete spalling?
The term concrete spalling is used to refer to concrete which is undergoing a process of fragmentation. This can lead to the concrete breaking into smaller segments and can expose its internal components to the surrounding air.
The cause of spalling damage is often chemical reactions between the concrete and other substances. It results in the formation of various unfamiliar compounds which accumulate within the concrete material itself. Due to the limited space, it exerts internal pressure and over time can cause the concrete to crack and thereby release the pressure outwards.
In a vicious circle, these cracks allow further air to infiltrate into the concrete and thereby increase the risk of structural damage. Plus, pieces of the concrete can dislodge or break off. Unfortunately, spalling concrete is a widespread issue and can affect concrete in multilevel buildings, on bridges and roadside pavements.
It is critical that timely intervention is carried out to address any concrete spalling and treat any damage before the integrity of the structure itself is compromised.
What causes concrete spalling?
Concrete spalling can stem from a variety of factors. Most commonly, extreme moisture and carbonation are the primary causes. Different factors can independently or collectively contribute to the occurrence and progression of concrete spalling.
Causes of concrete spalling can include:
Fire Exposure
Concrete being exposed to fire can initiate concrete spalling by causing the free water within the concrete to convert into steam. This internal expansion creates the pressure that leads to eventual spalling of the concrete.
Steel Corrosion
Rust forming on the embedded steel components within concrete can result in an increase in volume. This exerts undue pressure on the surrounding concrete and may cause it to subsequently spall.
Freezing and Thawing
More common in cold regions of the world, concrete spalling can occur during freezing and thawing cycles. As water enters the concrete and freezes during temperature drops it can lead to expansion and cracking. When the weather warms and subsequently thawing occurs, it can result in even further damage, exacerbating the spalling process.
Chemical Reactions
Alkali-silica reactions can occur when alkaline cement paste interacts with the reactive silica in many forms of concrete. These chemical reactions generate pressure, swelling, and can ultimately lead to concrete spalling.
Other Causes
Additional causes that are more preventative during the installation and construction process can include:
- Inadequate depth of cover over the reinforcement
- Poorly constructed joints
- Low-quality concrete covering over support steel
- Improper curing or finishing techniques
- A lack of bonding in two-course construction methods
How to recognise spalling concrete?
Concrete spalling manifests as a gradual weakening of the concrete surface. Typically, this means you will start to notice the formation of crack lines that can then eventually lead to pieces of concrete detaching. This deterioration can be observed in large structures such as bridges, where sections of the concrete surface exhibit signs of damage, but also in residential homes and buildings.
As mentioned, the process of concrete spalling is initiated by moisture infiltrating the protective layer surrounding the steel reinforcements or carbonation.
Over time, the internal exertion of pressure on the surrounding concrete causes the cracks to widen and become worse. If you notice this is occurring in your concrete, it can be a sign of spalling concrete.
Look out for:
- New cracks
- Widening cracks
- Broken concrete
- Chipped concrete
- Other sides of material deterioration
Can you prevent it?
When confronted with concrete spalling or the risk of it occurring, there are several steps you can take to address the issue. Prevention, where possible, is often the best approach to avoid concrete spalling altogether. Here are some preventive measures:
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Regular painting of ceilings
Applying paint to your ceilings with regular frequency can impede the carbonation process and prevent moisture infiltration into the concrete. Choose high-quality paint or anti-carbonation chemicals. If possible, repainting every three to five years can be highly effective in preventing spaling.
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Seal holes and cracks
Holes and cracks in your concrete can serve as entry points for moisture into surfaces. Have professional remedial builders inspect your property and promptly seal any imperfections they can identify.
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Ensure adequate ventilation
Humidity can accelerate the carbonation process which then causes concrete spalling. Where possible, ensure there is proper ventilation in moisture-prone areas such as bathrooms and kitchens by opening vents, windows, or doors even when these rooms are not in use.
How to repair concrete spalling
Concrete spalling is not always simple or easy to repair. Bad or amateur repair jobs can often lead to worse problems, compromised structural integrity and a large bill later on. Attempting to fix concrete issues independently can be challenging and hazardous, posing a threat of further damage to your property or structure if executed improperly.
That’s why repairing spalling concrete is best left to professionals with the right experience and knowledge in dealing with the complexity and risks involved.
Fortunately, BIM Sydney are trusted remedial building services specialists and have been servicing the greater Sydney area for decades.
Our team is your first port of call for all things concrete spalling–including prevention, identification and repair. Quality results, on time and to specification–that’s our guarantee.
