Understanding Concrete Cancer and Its Repair Process

Concrete cancer is a term that strikes fear into the hearts of property owners and building managers, and for good reason. As a contractor specialising in the repair of this common problem, I’ve seen firsthand the damage it can cause. Left untreated, concrete cancer can lead to costly repairs, structural damage, and even safety risks. as was highlighted recently with the 2021 partial collapse of Champlain Towers South in Florida USA which resulted in the death of 64 people

In this article, I’ll provide an overview of what concrete cancer is, how it develops, and the importance of addressing it early.

What is Concrete Cancer?

Concrete cancer, or spalling, is the deterioration of concrete when the steel reinforcement (rebar) embedded within it corrodes. Concrete is a durable material, but when cracks form or water infiltrates, the steel reinforcement is exposed to oxygen, moisture and contaminants, this causes the steel to rust and expand, which in turn breaks apart the surrounding concrete forming spalls This process creates a cycle of damage that worsens over time if not treated properly.

Causes of Concrete Cancer

Concrete cancer is often the result of a combination of environmental factors and construction-related issues. Here are the most common causes:

1. Water Ingress: Water is the most common culprit. If cracks form in the concrete or if the building’s waterproofing is insufficient, water can penetrate to the steel reinforcement. In coastal or humid areas, the presence of airborne chlorides from the ocean can accelerate the corrosion process.
2. Poor Quality Concrete and Construction Processes: If the concrete used during construction is of poor quality or improperly mixed, it can become more susceptible to cracking and water infiltration. Concrete with a high water-to-cement ratio can be porous, allowing moisture to seep through easily. Additionally, one of the most common defects we see is insufficient concrete cover over the steel reinforcing leading to early corrosion of the steel reinforcing.
3. Inadequate Waterproofing: Buildings that are not properly waterproofed or protected against moisture intrusion are at a higher risk of concrete cancer. Roofs, balconies, and even foundations are common areas where waterproofing may fail.
4. Environmental Exposure: Coastal areas are especially prone to concrete cancer due to the presence of chloride irons in the air, which can penetrate concrete and accelerates the corrosion of steel. Industrial pollutants, freeze-thaw cycles, and high humidity can also contribute to the problem.
5. Carbonation: Under normal conditions, the high pH of concrete creates a passivating layer of oxide on the surface of the rebar, protecting it from corrosion. This passive layer is stable in alkaline environments, typically maintained by the concrete’s high pH level. Carbon dioxide from the atmosphere reacts with calcium hydroxide in concrete reducing its PH, a natural aging process of all concrete structures. As the alkalinity reduces its ability to form a passivating layer around the reinforcing diminishes, to a point where corrosion begins when the protective layer fails, allowing moisture and chloride ions (if present) to penetrate and initiate electrochemical reactions resulting in the corrosion of the rebar.

Effects of Concrete Cancer

If left unchecked, concrete cancer can have serious consequences. These include:

1. Structural Damage: As the steel reinforcement rusts and expands, it exerts a pressure within the concrete, which results in cracks and spalls forming with the potential for chunks of concrete to fall. Over time, this can weaken the structural integrity of the building, compromising safety.
2. Aesthetic Degradation: In addition to the safety concerns, concrete cancer is unsightly. Spalls, cracks, and rust stains can ruin the appearance of a building, reducing its value and appeal.
3. Increased Repair Costs: The longer concrete cancer goes untreated, the worse it gets—and the more expensive it becomes to fix. What may start as a small repair job can grow into a full-scale structural rehabilitation if not addressed early.
4. Health and Safety Risks: Falling pieces of concrete can pose a risk to anyone in the vicinity, particularly in high-traffic areas like walkways or balconies. Severe cases of concrete cancer may even require buildings to be vacated until repairs are made.

How We Repair Concrete Cancer

At Opat, we specialise in diagnosing and repairing concrete cancer. Here’s our typical process for restoring a damaged structure:

1. Inspection and Assessment: We start with a thorough assessment of the affected area to understand the extent and cause of the damage. This often involves removing small sections of concrete to inspect the underlying rebar and. Where a major concern regarding the structural integrity of the building is considered, physical samples can be taken to determine the depth of carbonation and chloride iron penetrating helping establish the potential for ongoing rusting of the rebar.
2. Removing Damaged Concrete: Once the scope of the problem is understood, we remove the damaged concrete to expose the corroded steel. This step is crucial to ensure the repairs are comprehensive and long-lasting.
3. Treating and Replacing Rebar: The rusted steel reinforcement is cleaned or replaced if considerable corrosion has occurred, anti-corrosion coatings are applied to prevent future deterioration. This step is key to stopping the concrete cancer from recurring.in the location repaired  
4. Repairing and Resurfacing: We then apply high-quality, durable repair materials to restore the damaged concrete. Depending on the location and purpose of the structure, we may also install additional waterproofing membranes to protect against future water ingress 
5. Prevention: Finally, we focus on reducing and slowing the corrosion process by applying coatings which provide protection from both chlorides, moisture and carbonation of the concrete 

Why Early Detection Matters

The sooner concrete cancer is identified and addressed, the easier and cheaper it is to fix. Regular building inspections and maintenance are essential, especially in older buildings or those exposed to harsh environmental conditions. If you notice cracks, rust stains, or spalling concrete, it’s important to act 

Concrete cancer doesn’t fix itself—it only worsens over time. By addressing the problem early, it may be possible to prevent extensive damage, ensure the safety of your building, and save on future repair costs.

Get in Touch

If you suspect concrete cancer in your building, don’t wait for the problem to escalate. Contact Opat Brisbane for a professional inspection and repair solution. We have the experience and expertise to restore your building’s structural integrity and prevent further damage.

By staying proactive and vigilant, building owners and managers can protect their assets from the costly effects of concrete cancer. At Opat Brisbane, we’re here to help with industry-leading repair techniques and personalised service that ensures long-term results.

Contact Opat Brisbane today on 

07 3265 3654

brisbane@opat.com.au