shall be worked down into the surface by tamping and raking. When the
surface is sufficiently hardened to permit working, the surface shall be
screeded, floated, or trowelled to the specified finish.]
3.5
CURING AND PROTECTION
Curing and protection shall conform to the following requirements.
3.5.1
Duration
The length of the curing period shall be determined by the type of
cementitious material, as specified below. Concrete shall be cured by an
approved method.
[Type I portland cement
7 days]
[Type II portland cement
14 days]
[Portland cement blended with 25 percent or less fly-ash
14 days]
[Portland cement blended with more than 25
percent Fly-ash 21 days]
Immediately after placement, preplaced-aggregate 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 to the start of grouting. Preplaced-aggregate concrete
shall be protected from the damaging effects of rain for 12 hours and from
flowing water for 14 days. 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
Preplaced-aggregate concrete that is moist-cured 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. Where steel forms are left
in place during curing, the forms shall be carefully broken loose from the
hardened concrete and curing water continuously applied into the void 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. Burlap and cotton mats shall
be rinsed to remove soluble substances before using. Water for curing
shall comply with the requirements of paragraph WATER.
3.5.3
Curing with 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. The curing compound selected shall be compatible with any
subsequent paint specified.
SECTION 03372
Page 28
Previous Page
