Concrete Cancer: What Is It and Why Should You Care?

Concrete cancer happens when the steel reinforcement inside concrete starts to rust, causing cracks, flaking, and serious structural damage. Left untreated, it only gets worse, leading to costly repairs and safety risks. The good news? If you catch it early, it can be fixed. Let’s break down what causes it, how to spot it, and what you can do to prevent it.

What is Concrete Cancer?

Concrete cancer is what happens when moisture, air, or contaminants get into reinforced concrete, causing the steel inside to rust. Since rust expands, it puts pressure on the surrounding concrete, leading to cracking, flaking, and even structural failure.

It’s a big deal in coastal areas (where salty air speeds up corrosion) and older buildings that weren’t built with modern waterproofing methods.

Reinforced vs. Unreinforced Concrete – What’s at Risk?

Not all concrete is the same. Reinforced concrete has steel bars (rebar) inside to strengthen it, while unreinforced concrete is just... well, concrete.

• Reinforced Concrete: The main culprit for concrete cancer. If water gets in and reaches the steel, it starts rusting, expanding, and breaking the concrete apart from the inside.

• Unreinforced Concrete: Less prone to this type of deterioration, but it can still crack and degrade due to moisture, poor quality materials, or exposure to harsh weather conditions.

How Does Concrete Cancer Develop?

It doesn’t just happen overnight. It’s a slow process, and it all starts with water getting where it shouldn’t.

The Main Causes of Concrete Cancer:

• Water Ingress – Cracks, poorly sealed joints, or porous concrete allow water to seep in.

• Chloride Exposure – If your building is near the coast, salt in the air speeds up rusting.

• Carbonation – Over time, carbon dioxide reacts with concrete, making it more acidic and less protective of the steel inside.

• Poor Construction or Materials – Bad waterproofing, cheap concrete mixes, or not enough concrete covering the steel all lead to problems.

How to Spot Concrete Cancer – Key Warning Signs

If you’re worried your building might have concrete cancer, here are some red flags to look out for:

• Cracks in concrete – Especially near joints, edges, or balconies.

• Rust stains – If you see rust marks seeping through the concrete, the steel inside is corroding.

• Flaking or bubbling concrete – Also called “spalling,” this is when chunks of concrete start falling off.

• Exposed reinforcement bars – If the steel is visible and rusty, it’s a major warning sign.

• Leaks or damp patches – Water finding its way through cracks in the concrete.

Ignoring these signs is a bad idea—the longer you leave it, the more expensive and complicated the repairs get.

Why Does Concrete Cancer Happen?

At its core, concrete cancer is caused by water, air, and time. But there are a few other reasons why some buildings are more vulnerable than others:

• Poor Waterproofing or Drainage – If water can’t escape properly, it will find its way into the concrete.

• Low-Quality Concrete Mix – Weak or porous concrete allows moisture to get in.

• Structural Movement – Buildings naturally shift over time, creating small cracks where water can sneak in.

• Harsh Environments – Coastal locations, industrial areas, or places with extreme weather conditions see faster deterioration.

How to Prevent Concrete Cancer

The best way to deal with concrete cancer? Stop it before it starts.

• Use Proper Waterproofing – High-quality membranes and sealants prevent water from seeping in.

• Regular Inspections – Small cracks can turn into big problems, so get your concrete checked every few years.

• Use High-Quality Materials – Cutting corners on construction leads to long-term damage.

• Ensure Proper Steel Coverage – The more concrete covering the steel, the harder it is for water to reach it.

• Apply Protective Coatings – Anti-corrosion coatings on steel reinforcement can slow down rusting.

How to Fix Concrete Cancer?

If your building already has concrete cancer, don’t panic—it can be fixed. But it’s not a DIY job. It requires specialist remediation techniques to stop the damage from spreading.

The Repair Process:

• Professional Diagnosis – A structural engineer will assess the extent of the damage.

• Concrete Removal – Any damaged concrete is carefully removed.

• Steel Treatment – Rusted reinforcement bars are cleaned, treated, or replaced.

• Patching & Strengthening – High-strength repair materials or additional reinforcement are used to restore structural integrity.

• Waterproofing & Prevention – Once repaired, protective coatings and sealants help prevent it from happening again.

Don’t Ignore the Signs – Get Expert Help Today!

If you think your building might have concrete cancer, the worst thing you can do is wait. Early intervention can save you thousands in repairs and prevent serious structural issues.

At CARAS, we’re more than just strata building remediation specialists—we’re an advisory and project management business committed to delivering better environments for our clients and the communities around them. Whether you need full project management services from inception to completion or independent expert advice on a specific challenge, we provide solutions that offer total peace of mind at every stage.

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