NAT: Q&A Whether to treat or replace rusted rebar in concrete cancer repairs

This article discusses how to assess and manage rusted rebar in concrete cancer repairs, including when treatment or full replacement is necessary.

Question: In a Victorian strata building with concrete cancer, how much rust on reinforcing steel is acceptable before it must be replaced?

Concrete cancer treatment has started on our Victorian strata building. The contractor advised that they will only remove and repair areas of concrete that have visibly spalled, even though it appears that all of the reinforcing steel has some level of rust. In several places, rusted rebar ends protrude from the concrete. What level of rust on the reinforcing steel is considered acceptable before it must be exposed, cleaned, and treated, and at what point should the rebar be replaced entirely?

Answer: Reinforcement bar is usually only replaced if the steel has degraded to a point where it has lost its structural integrity.

Reinforcement bar is usually only replaced if the steel has degraded to a point where it has lost its structural integrity. Otherwise, the steel is treated depending on the specific circumstances.

Only a qualified structural engineer should make these determinations when there are significant problems, as often there are multiple factors to consider other than the corrosion itself. These include load, design, environment, and exposure that can influence a decision. I expect the contractor would have an engineer involved in this process. All work will need to be warranted and supported by designs from appropriately qualified and registered experts. If you are unsure about the decision, I recommend asking the question.

Bruce McKenzie
Sedgwick
E: bruce.mckenzie@au.sedgwick.com
P: 1300 735 720

This post appears in the December 2025 edition of The VIC Strata Magazine.

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Read next:

• NAT: Understanding concrete cancer in strata buildings
• NSW: Q&A How Do I Know if a Strata Building Has Concrete Cancer?
• NSW: Q&A Remediation of Serious Building Defect

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