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