Rebar corrosion: diagnosis and extent of damage

Rebar corrosion is the most frequent pathology of aged reinforced concrete, and also one of the worst assessed: visible rust is only the symptom. What matters is how much steel section has been lost and what it means for the structure.

What causes it

Two main causes: carbonation of the concrete (loss of alkalinity through CO₂) and the presence of chlorides (marine environments, de-icing salts). Both break the steel's protective layer and activate corrosion.

How the extent is measured

Diagnosis determines the carbonation depth or chloride content, the real cover and, above all, the section loss of the bars. With that figure the residual load-bearing capacity is assessed under the structural standards (EHE-08 / Eurocode 2).

What the report adds

The report distinguishes a cosmetic or superficial problem from one that affects stability, and sets the urgency of the intervention. Repair or reinforcement is carried out by a specialist contractor.

Frequently asked questions

Does visible rust mean immediate danger?
Not necessarily. It may be superficial or indicate significant section loss. Only measurement determines it.

Can it be repaired without replacing the structure?
In many cases yes, through cleaning, passivation and reinforcement. Feasibility is set by the diagnosis.

Who is liable in a recent building?
A structural defect in a new build fits the LOE ten-year warranty.