Concrete Spalling: Causes and Prevention Guide

Corroding rebKey Takeaways
Concrete spalling is the visible flaking, chipping or breaking away of concrete and is different from cracking or internal delamination.

Common causes include reinforcement corrosion, water penetration, poor concrete proportioning, inadequate compaction or curing, chemical and salt exposure, and severe heat or fire.

Rust stains, exposed aggregate, damp patches, widening cracks, exposed steel and falling concrete are important warning signs that should not be ignored.

The seriousness of spalling depends on its cause, depth, location and the condition of the reinforcement—not simply the visible size of the damaged patch.

Minor surface damage may sometimes be repaired with a suitable patching material, but deeper damage or corroded reinforcement requires professional assessment and structural repair.

The source of water entry, corrosion or chemical exposure must be identified and corrected before the visible damage is repaired, or the spalling may return.

Proper materials, accurate proportioning, careful placement, adequate compaction, correct curing, water protection and routine inspection can significantly reduce the risk of spalling.

Seek urgent professional help when concrete is falling, reinforcement is visible or heavily rusted, or the damage affects a beam, column, slab, balcony or foundation.

What Is Concrete Spalling?
Concrete spalling is the flaking, chipping or peeling of the outer concrete layer. Affected areas may appear rough, uneven or pitted. In advanced cases, pieces of concrete may fall away and expose the aggregate or steel reinforcement below the surface.

Spalling can occur in walls, slabs, beams, columns, foundations, balconies, driveways and pavements. Its seriousness depends on the depth, location and cause of the damage. A small surface patch may be mainly cosmetic, while deeper damage around structural members may require professional assessment.

Spalling is different from delamination. Delamination refers to separation within layers of concrete, which may not be immediately visible. Spalling is the visible breaking or detachment of concrete from the surface.
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