What is spalling concrete?
Spalling is the cracking, bulging and breaking away of the concrete cover over steel reinforcement. MND describes it as the flaking of concrete from the ceiling caused by corrosion of the steel bars in the floor slab. Rust occupies several times the volume of the steel it replaces, so as the bars corrode they push the cover off. It is most common in older buildings and in damp areas such as kitchens, toilets and roofs.
From the RRD Field Guide, checked against the sources cited in Concrete Spalling in Singapore: Causes, Risks, Repair Methods and Who Must Fix It. General information, not advice for your project.
The fuller picture
Spalling concrete is concrete cover cracking and breaking away because the steel reinforcement inside has corroded, usually after carbonation or chlorides destroy the steel's natural protection. Small patches can be repaired by removing loose concrete, cleaning and priming the steel and patching with polymer-modified mortar. Extensive spalling, beams, columns or cantilevers need a Professional Engineer. Owners repair inside HDB flats; MCSTs repair common property.
More questions on this topic
- Is spalling concrete dangerous?
- Can I repair spalling concrete myself?
- Who pays to repair spalling concrete in an HDB flat?
- Who pays to repair spalling concrete in a condominium?
- Does spalling repair need BCA approval?
- Why does spalling come back after repair?
- How is spalling linked to the Periodic Structural Inspection?