Scaling Concrete Surfaces

Scaling is local flaking or peeling of a finished surface of hardened concrete as a result of exposure to cycles of freezing and thawing. Generally, it starts as localized small patches which later may merge and extend to expose large areas. Light scaling does not expose the coarse aggregate. Moderate scaling exposes the aggregate and may involve loss of up to ⅛ to ⅜ inch [3 to 10 mm] of the surface mortar. In severe scaling, more surface has been lost and the aggregate is clearly exposed and stands out.

Note: Occasionally concrete peels or scales in the absence of freezing and thawing. Often this is due to the early use of a steel trowel, over-finishing or finishing while bleed water is on the surface.

Minor scaling is a cosmetic issue and may not need to be repaired. On the other hand, repairing concrete slabs with excessive and progressing scaling may not be feasible.

It is possible to repair light to moderately scaled surfaces. The repaired surface will only be as strong as the base surface to which it is bonded. The surface should be prepared to remove the unsound surface and should be free of dirt, oil or paint. The surface receiving the repair must be sound. To accomplish this, use a hammer and chisel, sandblasting, high-pressure washer, or jack hammer. The clean, rough, textured surface can then be repaired with thin bonded resurfacing.

• For concrete that will be exposed to severe freezing and thawing conditions, order good quality air-entrained concrete with a strength of 4000 psi [28 MPa]
• Do not add excessive water and place concrete at a slump of 3 to 5 inches [75 to 125 mm]
• Properly cure the concrete

• Finish concrete after bleed water has dissipated and avoid using steel trowels when finishing
• Consider sealing the surface with a commercial breathable sealer
• Avoid the use of deicing chemicals in the first winter and subsequently use them in moderate amounts