[Type I portland cement _________________________________
7 days]
[[Type IS][Type IP] cement ______________________________
7 days]
[Portland cement blended with silica fume _______________
7 days]
[Type II portland cement ________________________________ 14 days]
[Portland cement blended with
25 percent of less fly-ash or GGBF slag _____________ 14 days]
[Portland cement blended with more than
25 percent fly-ash or GGBF slag _____________________ 21 days]
Immediately after placement, concrete shall be protected from premature
drying, extremes in temperatures, rapid temperature change, and mechanical
damage. All materials and equipment needed for adequate curing and
protection shall be available and at the placement site prior to the start
of concrete placement. Concrete shall be protected from the damaging
effects of rain for 12 hours and from flowing water for 14 days [7 days
with Type III cement]. No fire or excessive heat including welding shall
be permitted near or in direct contact with concrete or concrete embedments
at any time.
3.5.2
Moist Curing
Moist-cured concrete shall be maintained continuously, not periodically,
wet for the entire curing period. If water or curing materials stain or
discolor concrete surfaces that are to be permanently exposed, they shall
be cleaned as required in paragraph APPEARANCE. Where wooden form
sheathing is left in place during curing, the sheathing shall be kept wet
at all times. If steel forms are used in hot weather, nonsupporting
vertical forms shall be carefully broken loose from the concrete, soon
after the concrete hardens, and curing water continuously applied into the
void so as to continuously saturate the entire concrete surface.
Horizontal surfaces may be moist cured by ponding, by covering with a
minimum uniform thickness of 50 mm 2 inches of continuously saturated sand,
or by covering with saturated nonstaining burlap or cotton mats.
Horizontal construction joints may be allowed to dry for 12 hours
immediately prior to the placing of the following lift. Silica fume
concrete, if used, shall be moist-cured. Curing of silica fume concrete
shall start immediately after placement.
3.5.3
Membrane-Forming Curing Compound
Concrete may be cured with an approved membrane-forming curing compound in
lieu of moist curing except that membrane curing will not be permitted on
any surface to which a grout-cleaned finish is to be applied or other
concrete is to be bonded, on any surface containing protruding steel
reinforcement, on an abrasive aggregate finish, or any surface maintained
at curing temperature by use of free steam. A styrene acrylate or
chlorinated rubber compound may be used for surfaces that are to be painted
or are to receive bituminous roofing or waterproofing, or for floors that
are to receive adhesive applications of resilient flooring. The curing
compound selected shall be compatible with any subsequent paint, roofing,
waterproofing, or flooring specified.
3.5.3.1
Pigmented Curing Compound
A pigmented curing compound meeting the requirements of the above paragraph
MEMBRANE-FORMING CURING COMPOUND may be used on surfaces that will not be
exposed to view when the project is completed.
SECTION 03301A
Page 42
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