coat, and the second coat shall be applied perpendicular to the first coat.
Concrete surfaces which have been subjected to rainfall within 3 hours
after curing compound has been applied shall be resprayed by the method and
at the coverage specified. Surfaces on which clear compound is used shall
be shaded from direct rays of the sun for the first 3 days. Surfaces
coated with curing compound shall be kept free of foot and vehicular
traffic, and from other sources of abrasion and contamination during the
curing period.
3.15.4
Impervious Sheeting
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NOTE: Use impervious sheeting only for surfaces
that are horizontal or near horizontal. Do not use
on slab surfaces where appearance is critical.
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The following concrete surfaces may be cured using impervious sheets:
[_____]. However, except for plastic coated burlap, impervious sheeting
alone shall not be used for curing. Impervious-sheet curing shall only be
used on horizontal or nearly horizontal surfaces. Surfaces shall be
thoroughly wetted and be completely covered with the sheeting. Sheeting
shall be at least 450 mm 18 inches wider than the concrete surface to be
covered. Covering shall be laid with light-colored side up. Covering
shall be lapped not less than 300 mm 12 inches and securely weighted down
or shall be lapped not less than 100 mm 4 inches and taped to form a
continuous cover with completely closed joints. The sheet shall be
weighted to prevent displacement so that it remains in contact with the
concrete during the specified length of curing. Coverings shall be folded
down over exposed edges of slabs and secured by approved means. Sheets
shall be immediately repaired or replaced if tears or holes appear during
the curing period.
3.15.5
Ponding or Immersion
Concrete shall be continually immersed throughout the curing period. Water
shall not be more than 10 degrees C 20 degrees F less than the temperature
of the concrete.
3.15.6
Cold Weather Curing and Protection
When the daily ambient low temperature is less than 0 degrees C 32 degrees F
the temperature of the concrete shall be maintained above 5 degrees C 40
degrees F for the first seven days after placing. During the period of
protection removal, the air temperature adjacent to the concrete surfaces
shall be controlled so that concrete near the surface will not be subjected
to a temperature differential of more than 13 degrees C 25 degrees F as
determined by suitable temperature measuring devices furnished by [the
Government][the Contractor], as required, and installed adjacent to the
concrete surface and 50 mm 2 inches inside the surface of the concrete.
The installation of the thermometers shall be made by the Contractor as
directed.
3.16
SETTING BASE PLATES AND BEARING PLATES
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NOTE: Damp-pack bedding mortar will be specified
for setting base and bearing plates, except that
nonshrink grout will be specified for heavy
SECTION 03300A
Page 62
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