⚠ Reinforced concrete · Invisible until late
How the damage progresses, and why you cannot see it
Two mechanisms attack the steel inside the concrete at once. Nothing shows on the surface until the corrosion is already advanced.
Chloride attack
Salt from sea spray migrates inward and triggers pitting corrosion of the reinforcement, even in sound-looking concrete.
Elevated within 200–500 m of coast · LNEC E 465
Carbonation
CO₂ neutralises the alkalinity that keeps the steel passive. Poor concrete carbonates several mm per year.
"Very high carbonation depths" · UALG
What the engineer sees, in sequence
Stage 1
Rust staining
Brown marks following the line of the rebar.
Stage 2
Cracking
Cracks run parallel to the reinforcement.
Stage 3
Spalling
Concrete cover detaches as steel expands.
Stage 4
Exposed steel
Section loss. Structural concern.