This article provides an overview of a national webinar on concrete cancer in strata buildings around Australia, featuring Bruce McKenzie and Andrew Hulse form Sedgwick. The session aimed to provide a comprehensive understanding of concrete cancer, its causes, identification, and remediation for strata communities.
NAT: Conquer Concrete Cancer: Your guide to identification, repair and prevention | Bruce McKenzie & Andrew Hulse, Sedgwick – March 2025
Main Points Covered in the Session
The webinar covered several crucial aspects of concrete cancer in strata buildings, aiming to educate owners and strata managers on this significant property concern.
What is Concrete Cancer?
Concrete cancer, in industry terms often referred to as concrete spalling, is essentially the corrosion of reinforcement steel within the concrete. This corrosion leads to cracking, delamination, and dislodging of the concrete surface, often manifesting as flaking, peeling, or bulging. Visible reinforcement steel and rust stains are telltale signs. Concrete is fundamentally composed of concrete and reinforced steel, both of which must remain intact for the structure to function correctly.
What Causes Concrete Cancer in Strata Buildings?
The underlying cause is the ingress of water, chlorides, or other environmental contaminants that penetrate the concrete cover and reach the reinforcement steel. This leads to a chemical or electrochemical reaction, causing the steel to expand and exert pressure, resulting in the concrete spalling. Factors contributing to this include concrete cracking, inadequate concrete cover over the steel, poor concrete mix (especially incorrect water ratio), insufficient compaction during installation (leading to air pockets), and water impacting the curing process. Physical damage such as impact or fire, and disturbances like concrete cutting or drilling that are not properly sealed afterward, can also initiate concrete cancer.
Other Concrete Defects
The presenters clarified that owners may confuse other concrete defects as concrete cancer. While they are not necessarily the same, these defects could be related. Examples include efflorescence (salt leaching), which is a separate water problem, and render coatings or masonry spalling, which are different forms of deterioration. However, if issues like cracking allow water ingress, they can eventually lead to the corrosion of underlying steel.
Early Indicators of Concrete Cancer
Early detection is crucial. Key telltale signs include rust stains and marks, cracking in the concrete, a bulging appearance of the concrete surface, delamination, and ultimately, the breaking and falling off of concrete. Bulging often indicates an issue developing beneath the surface before it becomes visually apparent.
Preventative Measures
While much of the susceptibility to concrete cancer is determined during the initial construction phase (correct engineering and building practices), strata owners and managers play a vital role in prevention through regular inspections and maintenance. Early involvement when issues like small cracks are noticed is essential. Ensuring any concrete cutting or drilling is properly treated and sealed is also important. Engaging experts for regular maintenance inspections can help identify potential problems early.
Consequences of Untreated Concrete Cancer
Leaving concrete cancer untreated can lead to significant damage and even structural failure. As the steel corrodes and expands, it further weakens the concrete, leading to a loss of compressive strength and reduced effective area of steel reinforcement. This can have severe consequences for the building’s structural integrity and can result in significantly higher repair costs down the line.
Remediation
Properly addressing concrete cancer is a multi-step process requiring the right people offering the right advice. It should not be rushed and steps cannot be skipped. The process typically involves:
- Inspection and assessment through visual checks and sometimes thermal imaging. Exploratory works may be necessary to understand the depth of the damage.
- Engaging experts, particularly structural engineers, is crucial to determine the extent of the damage, the affected area, the severity, and the cause. Engineers are best placed to understand the role of steel reinforcement and how to rectify the issue without compromising structural integrity.
- Outlining a clear scope of work and specifications for remediation by consultants or engineers.
- Using experienced and qualified contractors for the rectification work.
- In advanced cases, full removal of spalled concrete back to sound material, cleaning and potentially sealing or replacing rusted steel reinforcement, and reinstating the concrete are necessary. Thoroughness is essential to avoid recurrence.
- For minor issues like small cracks, the fix might involve simply scabbing out the crack and filling it with grout or sealant to prevent further water ingress.
- More advanced cases often require scaffolding and, in some situations, propping of the surrounding structure, leading to more invasive and disruptive works.
Main Themes During the Session
Several key themes were consistently emphasised by both Bruce McKenzie and Andrew Hulse throughout the webinar:
The Critical Importance of Early Intervention
Both presenters stressed repeatedly that addressing concrete issues, even seemingly minor ones like small cracks, as early as possible is the most effective way to prevent the development and progression of concrete cancer. Early intervention minimises damage, reduces costs, and avoids more disruptive and extensive repairs later on.
The Necessity of Expert Involvement
A central theme was the need to engage qualified experts, particularly structural engineers, throughout the process – from initial inspection and assessment to the development of remediation plans and oversight of the repair work. Owners corporations, strata managers, and even building managers are generally not expected to possess the technical expertise required to properly diagnose and address concrete cancer.
Understanding the Technical Aspects of Concrete Cancer in Strata
While aiming to keep the explanation accessible, the presenters highlighted the underlying chemical and structural processes involved in concrete cancer. This understanding underscores the fact that it is not a superficial issue and requires informed and technically sound solutions.
Proactive Awareness and Responsibility
The presenters encouraged owners to be aware of the condition of their building and to report any concerns or changes they observe. This proactive approach, combined with routine inspections, can significantly aid in early detection and intervention.
Final Thoughts and Actions for Owners and Strata Managers
In their concluding remarks, both Bruce McKenzie and Andrew Hulse offered key takeaways and recommended actions for owners and strata managers dealing with concrete cancer in strata buildings:
- Bruce McKenzie emphasised the consistent theme of early intervention and the crucial need to involve experts: Bruce advised reaching out to experienced professionals to mitigate costs and ensure the longevity of the building, as owners corporations are not expected to have in-depth technical knowledge of this issue.
- Andrew Hulse echoed the importance of early prevention but also offered a message of hope: Even if buildings have construction or engineering flaws, there are numerous treatments available to improve their longevity. Andrew encouraged owners and managers to seek advice and explore the available solutions.
9 Key Actions for Owners and Strata Managers Dealing with Concrete Cancer in Strata Buildings
- Be vigilant and aware of the signs of concrete cancer.
- Report any concerns, such as cracks or rust stains, promptly.
- Arrange for routine building inspections by qualified professionals.
- Engage structural engineers for the diagnosis and development of remediation plans for concrete cancer.
- Utilise experienced and qualified contractors specialising in concrete repair for any remediation work.
- Ensure thorough investigation and a multi-step approach are followed for addressing concrete cancer, avoiding shortcuts.
- Act immediately upon identifying concrete cancer to prevent further damage and higher costs.
- Disclose any known concrete cancer issues to insurers.
- If magnesite flooring containing asbestos is present, engage hygienists and follow proper legal and safety procedures for its removal.
By being proactive, informed, and seeking expert advice, owners and strata managers can effectively manage the risks associated with concrete cancer and ensure the safety and longevity of their strata buildings.
Presenters
Bruce McKenzie Sedgwick E: bruce.mckenzie@au.sedgwick.com P: 1300 735 720
Andrew Hulse Sedgwick E: andrew.Hulse@sedgwick.com P: 1300 735 720
Presentation slides
Download the slide pack: Conquering Concrete Cancer
This post appears in Strata News #737.
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