What Is Concrete Cancer? The Signs, Causes & How It's Fixed
The short answer
Concrete cancer is the corrosion of steel reinforcement inside concrete. When water and air reach the steel it rusts, and rusting steel expands, cracking and pushing off the concrete around it. It spreads until the steel is exposed, treated and the concrete restored.
If you have seen rust stains bleeding through concrete or lumps of it flaking away, that is concrete cancer. Here is what causes it, how to spot it early, and how it is repaired.
What concrete cancer actually is
Concrete cancer is the common name for corrosion of the reinforcing steel embedded in concrete. Concrete normally protects the steel, but once water, air and salts reach it, through cracks or thin cover, the steel rusts. Rust takes up more space than steel, so as it forms it pushes outward and cracks the surrounding concrete, which lets in more water and accelerates the process.
The signs of concrete cancer
It shows up most on balconies, suspended slabs, basements and car parks.
- Rust-coloured stains bleeding through the surface
- Cracks that follow the line of the reinforcing bar
- Concrete bubbling, flaking or falling away (spalling)
- Exposed, rusting steel
- Hollow-sounding areas when tapped
Why it needs to be fixed early
Concrete cancer does not stop on its own; it spreads as long as the steel keeps corroding. On balconies and suspended slabs it becomes a safety risk, and left long enough it can compromise the structure. Repairing it early, while the affected area is small, is far cheaper and safer than waiting. The fix is to cut out the failed concrete, treat or replace the steel, and restore the surface, which is our concrete cancer repair service.
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