3.2.2
Placing Temperature
Concrete, when deposited in the slurry, shall have a temperature of not
less than 5 degrees C 40 degrees F. Heating of the mixing water or
aggregates shall not be permitted until the temperature of the concrete has
decreased to 7 degrees C 45 degrees F. The materials shall be free from
ice, snow, and frozen lumps before entering the mixer. All placing
equipment and methods shall be subject to [approval] [review]. When
heating is necessary to keep the concrete temperature above 5 degrees C 40
degrees F, it shall be regulated so that the concrete temperature does not
exceed 15 degrees C 60 degrees F. The concrete, when deposited in the
slurry, shall not exceed 32 degrees C 90 degrees F. Cooling of the mixing
water and/or aggregates may be required to obtain an adequate placing
temperature.
3.2.3
Concrete Deposited in Cutoff Trench
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NOTE: The hopper on top of the tremie pipe shall be
of a size capable of receiving and passing concrete
into the tremie pipe at the capacity rate of the
batching, mixing, and conveying equipment.
Depending upon the quality of aggregates available,
some tests may not be required. Refer to EM
1110-2-2000 for the purpose of each test.
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Concrete placed for the cutoff wall shall be deposited in a bentonite
slurry-filled trench by a tremie or by a valved tremie. The methods and
equipment used shall be subject to approval. Concrete buckets will not be
permitted for placement of concrete in the slurry trench, although they may
be used to transport concrete to the tremie hoppers. The tremie shall be
watertight and sufficiently large to permit a free flow of concrete, but it
shall not be less than 250 mm 10 inches in diameter. A funnel-shaped
hopper of at least [_____] cubic meters yards in volume shall be required
at the top of the tremie. Neither the tremie pipe nor the hopper shall be
constructed of aluminum. Hoisting equipment for raising and lowering the
tremie pipe as the concrete is placed and tools for connecting the tremie
pipe sections shall be continuously available and on hand. In lieu of use
of a tremie, concrete may be placed using a positive displacement pump and
pump line provided the entire operation is approved in writing after a
demonstration of its use.
3.2.4
Concrete Placement
Tremie pipe sections shall be suitably secured together and a gasket used
at each joint to prevent leakage. A retrievable traveling plug (go-devil)
or a dry pipe with a plate and gasket wired to the bottom to prevent
contact of the concrete and the slurry in the tremie shall be required to
start each placement. The tremie assembly shall be lowered to rest within
150 mm 6 inches of the bottom of the trench prior to beginning placement.
During placement of the concrete, any unnecessary movement of the pipe
shall be avoided. The bottom of the tremie pipe shall remain submerged in
fresh concrete at all times to a depth that will produce the flat test
surface slope that can practically be achieved. This depth shall not be
less than 3 m 10 feet nor more than 9 m 30 feet except when beginning
placement at the bottom of a panel. Batches of concrete shall be supplied
to the tremie pipe at a uniform rate for a continuous flow. The tremie
SECTION 03373
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