3.3.2.8
[Placing Concrete Underwater
Concrete, described in Bid Item [_____], shall be deposited through water
by a tremie or concrete pump. The methods and equipment used shall be
submitted in advance of placement for review. Concrete buckets may be used
only to charge the hopper on top of the tremie. Concrete buckets shall not
be lowered under water and the concrete discharged subaqueously. The
tremie shall be watertight and sufficiently large to permit a free flow of
concrete. The discharge end of the pump line or tremie pipe shall be kept
submerged continuously in the concrete after placement starts. The
underwater seal shall be effected in a manner that will not produce undue
contamination of the concrete or turbulence in the water. Placement shall
proceed without interruption until the concrete has been brought to the
required height. The tremie or pump lines shall not be moved horizontally
during a placing operation, unless removed, moved, and properly restarted,
and a sufficient number of tremies or pump lines shall be provided so that
the maximum horizontal flow will be limited to 4.5 m 15 feet.]
3.4
FINISHING
3.4.1
Unformed Surfaces
The ambient temperature of spaces adjacent to surfaces being finished shall
be not less than 5 degrees C 40 degrees F. In hot weather when the rate of
evaporation of surface moisture, as determined by use of Figure 2.1.5 of
ACI 305R, may reasonably be expected to exceed 1.0 kg/square meter 0.2 psf
per hour, provisions for windbreaks, shading, fog spraying, or evaporation
retarding film shall be made in advance of placement to prevent plastic
shrinkage cracks, and such protective measures shall be taken before,
during, and immediately after finishing as operations require. All
unformed surfaces of concrete that are not to be covered by additional
concrete or backfill shall have a float finish, unless a trowel finish is
specified, and shall be true to elevation as shown on the drawings.
Surfaces to receive additional concrete or backfill shall be brought to the
elevation shown and left true and regular. Exterior surfaces shall be
sloped for drainage unless otherwise shown in the drawing or directed.
Joints shall be carefully made with a jointing or edging tool. The
finished surfaces shall be protected from stains or abrasions. The
concrete shall be thoroughly consolidated before finishing operations
commence or before leaving it for future concrete or backfill placement.
3.4.1.1
Float Finish
Surfaces to receive a float finish shall be screeded and darbied or
bullfloated to bring the surface to the required finish level with no
coarse aggregate visible. No water, cement, or mortar shall be added to
the surface during the finishing operation. Floating may be performed by
use of suitable hand floats or power-driven equipment. Hand floats shall
be of aluminum or magnesium. After the water sheen has disappeared, the
concrete, while still green but sufficiently hardened to bear a man's
weight without deep imprint, shall be floated to a true even plane.
3.4.1.2
Trowel Finish
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NOTE: Refer to the appropriate design memorandum
for surfaces to be trowel finished. Be sure these
are shown in the drawings.
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SECTION 03700
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