What is Steel loss in concrete structures?
Steel loss from corrosion is the most common cause of failure for reinforced concrete structures. Once steel corrodes it expands and breaks apart along with the concrete its embedded in, exposing more steel to corrosion risk and beginning the cycle again. Over time this process can create extreme degradation and volume loss of the steel reinforcement in concrete structures and severely undermine their structural integrity.
How does Steel loss damage concrete structures?
The degradation of reinforcement or prestressing steel results in a significant loss of structural strength, posing a risk to the integrity and stability of the concrete structure.
Corrosion of reinforcement due to concrete carbonation or chloride contamination leads to a progressive loss of steel cross-section and is generally indicated by rust staining on the concrete surface and the appearance of cracks following the line of reinforcement.
For more significant steel loss (more than 3%), delamination and spalling of the concrete cover will occur, exposing the corroded reinforcement to further deterioration.
Depending on detailing, exposure conditions and concrete properties (porosity, mechanical resistance and cover), steel loss may be present without any external signs. Corrosion of stressed tendons within post-tensioned ducts present a particular problem as there may be little evidence of corrosion visible on the surface (this is of particular concern in the anchorage zone, where leakage of chloride laden water may occur).
What causes Steel fracture?
Poor compaction.
Inadequate curing.
Poor concrete quality.
Low cover.
Construction defects (e. g. detailing, cracks, voids, honeycombing).
Congested reinforcements.
Poor detailing.
How can I identify Steel fracture in concrete structures?
Visual survey | Non-destructive testing | Destructive testing |
Visual examination | Measurement of steel cross-loss after removal of concrete cover |
How can I repair Steel fracture in concrete structures?
Concrete replacement with addition of reinforcement.
Depending on condition and strength of existing concrete: