applied as soon as the surface of the concrete approaches surface dryness
and shall be vigorously and thoroughly rubbed over the area with clean
burlap pads, cork floats, or stones to fill all voids. The grout shall be
composed of one part portland cement as used on the project, to two parts
by volume of well-graded sand passing a 600-m (No. 30) sieve mixed with
water to the consistency of thick paint. White cement shall be used for
all or part of the cement as approved to give the desired finish color.
The applied coating shall be uniform, completely filling all pits, air
bubbles, and surface voids. While the grout is still plastic, remove all
excess grout by working the surface with a rubber float, burlap pad, or
other means. Then, after the surface whitens from drying (about 30 minutes
at normal temperature), rub vigorously with clean burlap pads. Immediately
after rubbing is completed the finished surface shall be continuously moist
cured for 72 hours. Burlap pads used for this operation shall be burlap
stretched tightly around a board to prevent dishing the mortar in the voids.
3.5
CURING AND PROTECTION
3.5.1
Curing Time
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NOTE: Curing time may be extended if required by
the thermal study. See the concrete materials
design memorandum for the approved types of
cementitious materials.
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All concrete shall be cured by one of the following methods or combination
of methods for the period of time given below corresponding to the
cementing materials used in the concrete:
[Type III portland cement ...............................
3 days]
[Type I portland cement .................................
7 days]
[Portland cement in combination with silica fume ........
7 days]
[Type II portland cement ................................ 14 days]
[Portland cement blended with 25 percent or
less fly-ash or GGBF slag ............................... 14 days]
[Portland cement blended with more than
25 percent fly-ash or GGBF slag ......................... 21 days]
Curing shall begin immediately after placing. The Contractor shall have
all equipment needed for adequate curing and protection of the concrete on
hand and ready to install before actual concrete placement begins. The
curing medium and method, or the combination of media and methods used,
shall be as approved in accordance with paragraph SUBMITTALS, SD-03
Product Data, submittal item "Curing".
3.5.2
Moist Curing
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NOTE: This requirement is for hot weather curing
only and has to be used under certain conditions
only. Thermal cracking can occur when the
difference in temperature between the interior
concrete is more than 7 degrees C (20 degrees F)
higher than the surface temperature of a concrete
SECTION 03700
Page 65
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