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Concrete Cancer


Concrete cancer is the term given to the gradual destruction of concrete caused by rusting of embedded steelwork as a result of water penetration and can lead to a building's structural integrity being compromised. When water penetrates concrete through fine cracks or weathered, porous surfaces, it rusts the structural steel within which then expands. When the steel expands it creates more concrete cracks allowing for more water penetration, cancer spread and eventual spalling (when concrete starts to fall off a building), which will continue, if left untreated.

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  • worn surfaces: unprotected, porous surfaces lead to water absorption and concrete cancer.

  • cracked / fractured concrete: cracks provide water access to the steel reinforcement

       instigating concrete cancer and fracturing the concrete enabling further water penetration.

  • moisture stains and ponding: inadequate drainage causes water to settle into concrete

       leading to concrete cancer.​

  • failing control and expansion joints: joints that do not facilitate concrete movement can lead to concrete fracturing and concrete cancer.

  • inadequate concrete cover: steel reinforcement too close to the surface makes it easier for water absorption resulting in concrete cancer.

  • rust stains: when water comes into contact with steel reinforcement, the steel rusts.

  • rusted balustrade fixings: rust spreads to the embedded concrete starting the concrete cancer process.​

  • bubbling paint: paint that appears to be bubbling i.e. on soffits, often means concrete cancer is present.

  • hollow surfaces: concrete surfaces that seem hollow usually have concrete cancer.

  • exposed steel reinforcement: concrete cancer causes concrete to break away exposing the steel reinforcement.

What is it?

Understanding the phenomenon known as concrete cancer is a pivotal step for property owners and managers in ensuring the longevity and value of their assets. Concrete cancer describes the intricate process where water accessing structural steel in concrete, causing rust to develop. The rust expands causing stresses and fractures within the surrounding concrete. This sequence continues if left unattended, with areas of newly fractured concrete becoming a conduit for further moisture infiltration, a catalyst for the expansion of concrete cancer to wider and more prevalent areas. As you can see, what initially presents as minor patches of concrete cancer evolves into larger, more complex and expensive repairs.


The Cost

In our experience, this transformation can lead to an annual damage escalation of around 5%, directly impacting the financial implications of necessary repairs. Through proper remediation, we can halt this process and add waterproof and protective coatings to safeguard repaired elements and original structures from new instances of concrete deterioration.

Therefore a key focus for property owners and managers is to control the rising cost of the damage while maintaining structural integrity and asset value. A foundational financial principle underscores these actions:

  • Concrete cancer repairs cost between approximately $2000 to $3000 + GST per square meter, with a yearly increase of about 5% in repair scope if left unaddressed.

  • Waterproof coatings, defending structures against concrete cancer, require a budget of $100 to $150 + GST per square meter for both supply and installation.


As demonstrated by the rates above, addressing and preventing concrete cancer is crucial for owners to uphold their asset's value and avert substantial future repair costs.


The Most Common Hiding Places

Concrete fracturing in leading edges, soffits, beams, and columns is typically caused by concrete cancer. Signs include visible rust stains, localized fractures, and a hollow sound when tapped. Remediation involves breaking out the area to expose clean steel, eliminating rust, and using engineered patching materials for paintable finishes. Conspar has employed a validated method since 1996, endorsed by Structural Engineers and outlined in our 'Remediation Plans'.

Moreover, steel components exposed in or through concrete, like beams, lintels, and balustrade fixings, often serve as vulnerable points for concrete cancer. They link weather-exposed surfaces with the structural substrate, initiating rust and cracks. Over time, this harm expands, progressing to affect structural reinforcement within the concrete beneath and adjacent to these zones.

If you would like to find out more, or discuss the above in relation to your own property, please feel free to contact us.

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