Scaling

Scaling is the local flaking or peeling of surface mortar, usually less than 1/8 th inch, caused primarily by hydraulic pressures from freeze-thaw cycles affecting the concrete at the surface.

Common Causes
• Excessive slump, overworking of wet concrete, premature finishing operations, inadequate or improper curing.
• Little or no entrained air due to: failure to use A/E agent, air worked out by overworking wet concrete, or premature finishing.
• Use of de-icing salts or chemicals used for ice removal on concrete with inadequate strength, air entrainment, or curing.

Prevention
• Always use Air Entrained concrete for outside work and indoor surfaces exposed to vehicular traffic (5 to 8 % is right for most mixes).
• Use low-slump concrete (4 inch max .) and a water/cement ratio no greater than 0.50.
• Cure the concrete immediately , with a recognized quality-curing compound.
• Don't sprinkle the surface with water
• Don't over-vibrate concrete - too much vibration reduces air entrainment.
• Protect the surface from freezing until it has a strength of 500 psi (keep the concrete above 50 degrees for 5 days.)
• After 28 days, apply a high quality sealer to the surface.
• Use quality finishing procedures, tools, timing, and techniques.
• Don't use de-icing salts or de-icing chemicals for at least the first year, avoid completely if possible. Sand will work well for traction.

Repair
1. Thoroughly clean surface and remove all weak or unsound material using a hammer and chisel, sandblasting, high-pressure washer, or jack hammer.

2. Apply a thin bonded resurfacing such as:
• Portland cement concrete resurfacing
• Latex modified concrete resurfacing
• Polymer-modified cementitious-based repair mortar


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