Methods and equipment used shall prevent the washing
of the cement from the mixture, minimize the
formation of laitance, prevent the flow of water
through the concrete before it has hardened, and
minimize disturbance to the previously placed
concrete. Do not deposit concrete in running water
[, seawater,] or in water temperatures below 2
degrees C (35 degrees F) 35 degrees F. Tremies, if
used, shall be watertight and sufficiently large to
permit a free flow of concrete. Keep the discharge
end continuously submerged in fresh concrete. Keep
the shaft full of concrete to a level well above the
water surface. Discharge and spread the concrete by
raising the tremie to maintain a uniform flow.
Place concrete without interruption until the top of
the fresh concrete is at the required height."
Add the following to paragraph entitled "Curing
Periods": "A structure permanently submerged in
fresh water shall be cured for 12 hours minimum
prior to being submerged in fresh water. A
structure permanently submerged in seawater shall be
cured for 5 days minimum prior to being submerged in
seawater."
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Place concrete as soon as practicable after the forms and the reinforcement
have been inspected and approved. Do not place concrete when weather
conditions prevent proper placement and consolidation; in uncovered areas
during periods of precipitation; or in standing water. Prior to placing
concrete, remove dirt, construction debris, water, snow, and ice from
within the forms. Deposit concrete as close as practicable to the final
position in the forms. Do not exceed a free vertical drop of 1 m (3 feet)
3 feet from the point of discharge. Place concrete in one continuous
operation from one end of the structure towards the other. Position grade
stakes on 3 m (10 foot) 10 foot centers maximum in each direction when
pouring interior slabs and on 6 m (20 foot) 20 foot centers maximum for
exterior slabs.
[3.6.1
Footing Placement
Concrete for footings may be placed in excavations without forms upon
inspection and approval by the Contracting Officer. Excavation width shall
be a minimum of 100 mm (4 inches) 4 inches greater than indicated.
]3.6.2
Vibration
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NOTE: For prefabricated epoxy-coated rebar use ASTM
A 934/A 934M. For epoxy-coated rebar use ASTM A
775/A 775M.
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ACI 301 [and [ASTM A 934/A 934M][ASTM A 775/A 775M]]. Furnish a spare,
working, vibrator on the job site whenever concrete is placed. Consolidate
concrete slabs greater than 100 mm (4 inches) 4 inches in depth with high
frequency mechanical vibrating equipment supplemented by hand spading and
tamping. Consolidate concrete slabs 100 mm (4 inches) 4 inches or less in
SECTION 03300N
Page 35
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