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Common Concrete Failures at High and Low-Rise Buildings: Causes and Repair Methods

Many high and low-rise buildings are constructed of concrete, providing strength and durability. However, over time, concrete buildings develop concrete failures that require attention and repair. In this blog post, we’ll look at three common concrete issues for buildings —efflorescence, cracks, and concrete spalling—exploring their causes and providing repair methods. 

Efflorescence: What’s that White Stuff on My Wall?

Efflorescence is a white, powdery deposit that appears on the surface of concrete. It occurs when the water-soluble salts present in the concrete are brought to the surface by moisture. As the water evaporates, it leaves behind these unsightly deposits. It’s a common failure, especially with today’s concrete mixtures and needs to be addressed to avoid costly damage to concrete walls down the road.

Concrete Failures Efflorescence

How to repair efflorescence:

  • Identify the Source of Moisture: Identifying and eliminating the source of moisture is key. Common causes are water ingress from failed roofs and flashing, cold and expansion joints failure and improper curing of concrete which can lead to moisture trapped. 
  • If an obvious source failure is identified, like failed flashing allowing water ingress, those areas must be fixed. If the efflorescence being carried forward from moisture that was trapped in the concrete the following methods can be used for repair.
  • Cleaners: Efflorescence deposits on the surface can be neutralized and removed using efflorescence cleaners. Common options include mild acids like muriatic acid or specialized biodegradable efflorescence cleaners. These cleaners should be used with caution as they have the potential to etch surfaces like windows and metal substrates. 
  • Power wash: After cleaning, the affected area should be thoroughly power washed with up to 3500 PSI to further remove efflorescence deposits, the applied cleaner and other dirt / debris.

At this stage, a decision on what coating systems or sealer to use to inhibit future efflorescence and protect the concrete long term will be required. There is a myriad of options on the market, Good, Better and Best, we will discuss these options in detail in our future blog posts.

Cracks: The Structural Menace

Cracks in concrete can result from various factors, including shrinkage, temperature fluctuations, settlement, and structural stress. They can compromise the structural integrity of a building and lead to water ingress.

Concrete Failures Cracks: The Structural Menace

How to repair concrete cracks at walls

  • Crack Chasing: In situations where large cracks are present, crack chasing may be necessary. Crack chasing involves using specialized grinders with diamond blades, to widen and clean out the crack. This creates a well-defined groove that enhances the adhesion of the repair material.
  • Prepare the Crack: Cleaning the crack is necessary, removing loose debris, and widening it if necessary. This creates a secure bonding surface for the repair material.
  • Tooling Urethane Sealants: After crack chasing and cleaning, urethane sealants are used to seal the cracks. It’s essential to properly tool the sealant so the crack is sealed and looks aesthetically pleasing. Tooling involves smoothing and shaping the sealant to ensure it adheres tightly to the sides of the crack. Specialized tool to achieve a uniform and aesthetically pleasing finish. This stage requires a significant amount of experience and skill by the technician to ensure a long-term repair.
  • Cracks can also be repaired with concrete, although many concrete are prone to failure on some cracks and will not be as long-lasting urethane sealant. 
  • Applying concrete for crack repairs: Apply a bonding agent to the cleaned crack to ensure proper adhesion between the existing concrete and the repair material. Fill the crack with a suitable concrete patching compound. Trowel to create a uniform finish. This step typically requires a skilled tradesperson. There are thousands of concrete finishes and it take skill to match existing finishes. Allow the repair material to be cured according to the manufacturer’s instructions. 

In order to achieve a seamless concrete crack repair, every step is integral to the process, ensuring meticulous attention and precision.

Concrete Spalling: I have a chunk of concrete hanging off my building!

Concrete spalling occurs when the surface layer of concrete begins to deteriorate and fall away, moisture escaping, rusting re-bar, freeze-thaw cycles during curing or poor concrete mix. It can lead to structural weakening, unsightly appearance and major repairs.

Concrete Failures Concrete Spalling

How to repair concrete spalls

  • Remove Loose Concrete: Start by removing the loose or damaged concrete.Diamond cutters and Hilti tools are valuable assets in concrete spalling repair due to their precision and efficiency. These tools are equipped with diamond-tipped blades, which are exceptionally hard and capable of cutting through concrete with ease. The controlled cutting provided by these tools allows for accurate removal of damaged concrete.
  • Exposed rebar is a common occurrence in spalling situations. To ensure the long-term integrity of the repair, it’s vital to assess the condition of the rebar. Concrete needs to be chipped away from all sides of the rebar, leaving it fully exposed for repair.  If corrosion is present, it should be addressed by cleaning the rebar, applying a rust converter to halt further corrosion, and then coating it with a corrosion-inhibiting primer. 
  • Prepare the Surface: Thoroughly clean and prepare the exposed surface. Apply a bonding agent to enhance adhesion between the existing concrete and the repair material.
  • Apply Repair Mortar or Resurfacer: Use a suitable repair mortar or concrete resurfacer to restore the surface. Apply it evenly, smoothing the surface with a trowel or float.
  • Cure and Seal: Allow the repair material to cure according to the manufacturer’s instructions. After curing, apply a concrete sealer to protect the repaired area from moisture and further damage.
  • Professional Assessment: For larger structural issues, it’s advisable to consult with an engineering firm, who can assess the extent of the damage and recommend appropriate repair methods.

Preventive Measures: Guarding Against Future Concrete Failures

While repairs are essential for addressing concrete failures, preventive measures play a crucial role in prolonging the life of concrete structures. Regular inspections, routine maintenance, and addressing issues promptly can prevent these common problems from escalating.

In conclusion, concrete failures like efflorescence, cracks, and concrete spalling are common issues in high and low-rise buildings. Understanding their causes and employing detailed repair methods is essential for maintaining the structural integrity and appearance of concrete structures. Preventive maintenance and professional consultation can go a long way in ensuring the longevity and safety of your building’s concrete components.

If you have noticed concrete failures at your building contact WCP at [email protected] or call us at 604 420 5552. One of our certified representatives will be happy to answer your questions.

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