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Crazing
Concrete Surfaces
- The
development of a network of fine random cracks or fissures
on the surface of concrete or mortar
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Cracks are rarely more than 1/8 inch deep
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Generally, develop at an early age and are apparent the day
after placement or at least by the end of the first week
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Usually not readily visible until the surface has been
wetted and it is beginning to dry out
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Caused by rapid surface drying (high evaporation rates)
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low humidity, high temperature, direct sunlight, and
drying winds on a concrete surface when the concrete is
just beginning to gain strength
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Crazing concrete surfaces do not affect the structural
integrity of the concrete
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Rarely do they affect the durability or wear resistance
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Scaling Concrete
Surfaces
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Local flaking or peeling of finished surface of hardened
concrete
- A
result of exposure to freezing and thawing
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Begins as localized small patches and later extends to
expose large areas
- In
severe situations, more of the surface is lost and the
aggregate is clearly exposed and stands out
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Caused by freezing and thawing in the presence of moisture
and/or deicing salts are susceptible to scaling
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Fertilizers with ammonium sulfate or ammonium nitrate
can cause scaling as well as induce severe chemical
attack on the concrete surface
- With
proper care the chance of scaling can be reduced
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See Concrete Care section
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Plastic Shrinkage Cracking
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Appears in the surface of fresh concrete
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Usually parallel to each other about 1 to 3 feet apart,
relatively shallow, and do not intersect the perimeter of
the slab
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Caused by the surface drying out before it the concrete has
set (high evaporation rates)
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Wind velocity in excess of 5 mph, low relative humidity,
and high rotating and or concrete temperatures
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Plastic shrinkage cracks are unsightly but rarely impair the
strength or durability of concrete floors and pavements
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Concrete Care
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Proper curing by using liquid membrane curing compound can
reduce the risk of scaling
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Curing ensures the proper reaction of cement with water,
known as hydration
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Allows the concrete to achieve its highest potential
strength
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Normally included with all our installation at no
additional cost
- Do
not use deicing salts, such as calcium or sodium chloride,
in the first year after placing the concrete
- Use
clean sand for traction
- When
conditions permit, hose off accumulation of salt deposited
by cars on newly placed driveways and garage slabs
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Never use ammonium sulfate or ammonium nitrate as a deicer;
these are chemically aggressive and destroy concrete
surfaces (also in fertilizers)
- Be
sure concrete surface drains properly
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Poor drainage permits salt and water to stand on the
surface for extended periods of time
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This greatly increases the severity of the exposure that
causes scaling
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Protect concrete from the harsh winter environment
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Apply a commercially available breathable concrete
sealer or water repellent specifically designed for use
on concrete slabs
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Late summer is the ideal time for surface treatment
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