The Hidden Dangers of Concrete Cancer and How to Treat It

Overview

Concrete cancer—also called spalling—occurs when embedded steel reinforcement corrodes, expands and fractures the surrounding concrete. In coastal and high‑moisture Australian environments it’s one of the most common and expensive building defects. Acting early saves money and protects occupants.

Why it Happens

The primary driver is water ingress. Moisture reaches the rebar via surface cracking, failed waterproofing, porous substrates, or chloride salts. Carbonation lowers concrete alkalinity, reducing passivation and accelerating corrosion. As steel rusts it can expand up to seven times its volume, forcing concrete to crack and delaminate.

Early Warning Signs

Look for rust stains bleeding from cracks, drummy or hollow areas when tapped, blistering or flaking concrete, moisture staining on soffits, and exposed or rusted reinforcement. Any of these warrants professional investigation.

Risks of Delay

Unchecked spalling undermines structural capacity (beams, slabs, balconies), increases repair scope and costs, presents falling‑debris hazards, and can compromise insurance and compliance obligations—especially in strata and commercial assets.

Professional Repair Steps

1) Diagnose with cover‑meter surveys, delamination mapping and carbonation/chloride testing. 2) Break out to sound concrete. 3) Clean and treat or replace corroded reinforcement with anti‑corrosion primers. 4) Rebuild with polymer‑modified or high‑build repair mortars to restore section. 5) Apply protective coatings or membranes to seal against water and chlorides.

Prevention Strategy

Adopt a planned maintenance program: periodic façade and balcony inspections; proactive crack injection and joint resealing; re‑coating cycles for protective systems; drainage improvements; and targeted cathodic protection on high‑risk elements where appropriate.

For Strata & Commercial

Older podiums, car parks and coastal façades are especially vulnerable. Portfolio‑level condition assessments help prioritise works and stage budgets, minimising disruption to residents and tenants.

Conclusion

Concrete cancer is progressive but manageable with timely intervention. Accurate diagnosis, disciplined repair methodology and durable protection are the keys to a lasting result.