What is concrete cancer?
Concrete cancer is the common name for corroding steel reinforcement inside concrete. Water and salt work their way in through cracks or thin cover, and the steel starts to rust. Rust takes up far more space than the original steel, so it pushes outwards, cracking the concrete and eventually breaking pieces off. That exposes more steel to the weather, and the damage speeds up.
In Perth we see it most on concrete beams and lintels, balconies, eaves, stairs and older exposed aggregate panels, especially near the coast where salt air gets into the concrete.
Signs of concrete cancer
- Cracks running along the line of the steel
- Rust stains bleeding through the concrete or render
- Concrete that sounds hollow or drummy when tapped
- Pieces of concrete that have spalled or fallen off
- Exposed, rusted reinforcement bars
How we repair it
We cut back all loose and drummy concrete until we reach sound material, exposing the full length of corroded steel. The rust is removed from the reinforcement and the bars are coated with a rust-inhibiting primer. Where steel has lost too much section, we add new bars alongside it.
The section is then rebuilt in layers with a polymer-modified repair mortar, keyed between coats so each layer bonds properly. We finish it back to the original profile and match the surrounding surface as closely as possible. Patching over the top without treating the steel doesn't work, as the rust simply carries on underneath.
Recent concrete cancer repairs work
