Concrete Cancer & Spalling Repair in Sydney

What concrete cancer repair in Sydney actually involves

Concrete cancer and concrete spalling describe the same failure. Reinforcing steel inside the slab corrodes; rust occupies several times the volume of the steel it replaces; the pressure cracks the concrete cover and pushes it off. On a balcony that usually appears first at the slab edge or on the soffit underneath, as a crack, then a rust stain running down the face, then a piece of concrete on the ground.

Breakout, treat, reinstate

The repair sequence is breakout, treat, reinstate. Damaged concrete is cut back past the corrosion until sound material and clean steel are reached — which is nearly always further than the visible damage suggests, because the corrosion travels along the bar. The reinforcement is cleaned back to bright metal and coated. Repair mortar is packed into the recess and finished. Where the cause was water getting in, the water has to be dealt with too, or the same bar rusts again behind the new mortar.

This is why patching does not hold. A cosmetic patch over corroding steel hides the stain for a season and leaves the mechanism running. The tell is a repair that fails at its own edges within a year or two, the sound concrete next to the patch spalling next.

Concrete Cancer & Spalling Repair in Sydney — common questions

How do I know if it is concrete cancer or just a crack?

Rust staining is the difference worth looking for. A crack with a brown stain running out of it, or a patch of soffit that sounds hollow when tapped, is the pattern — and because it is found by sounding rather than by eye, an inspection usually marks out a bigger area than a photograph suggests.

Is my balcony dangerous?

Concrete falling from a soffit is the case to treat as urgent. If material has already come away from an overhead surface, keep people out from underneath it and get it looked at rather than waiting for the next piece.

How long before it needs doing again?

Not in the repaired area, if the steel was properly treated and re-covered and the water was dealt with at the same time. Elsewhere on the same building is a different question — the rest of the structure is the same age and has had the same exposure.