that buckets larger than 1.5 cubic meters 2 cubic yards shall not be
manually operated. The design of the bucket shall provide means for
positive regulation of the amount and rate of deposit of concrete in each
dumping position.
3.1.4.2
Trucks
Truck mixers operating at agitating speed or truck agitators used for
transporting plant-mixed concrete shall conform to the requirements of ASTM
C 94/C 94M. Nonagitating equipment shall not be used for transporting
concrete.
3.1.4.3
Chutes
When concrete can be placed directly from a truck mixer or agitator, the
chutes attached to this equipment by the manufacturer may be used. A
discharge deflector shall be used when required by the Contracting Officer.
Separate chutes and other similar equipment will not be permitted for
conveying concrete.
3.1.4.4
Concrete Pumps
Concrete may be conveyed by positive displacement pump when approved. The
pumping equipment shall be piston or squeeze pressure. The pipeline shall
be rigid steel pipe or heavy-duty flexible hose. The inside diameter of
the pipe shall be at least three times the nominal maximum-size coarse
aggregate in the concrete mixture to be pumped, but not less than 100 mm 4
inches. Aluminum pipe shall not be used. The nominal maximum-size coarse
aggregate shall not be reduced to accommodate the pumps. The distance to
be pumped shall not exceed limits recommended by the pump manufacturer.
The concrete shall be supplied to the concrete pump continuously. When
pumping is completed, concrete remaining in the pipeline shall be ejected
without contamination of concrete in place. After each operation,
equipment shall be thoroughly cleaned, and flushing water shall be wasted
outside of the forms.
3.2
PLACING
Concrete placement will not be permitted when, in the opinion of the
Contracting Officer, weather conditions prevent proper placement. Concrete
shall be deposited in the tremie hopper and in so depositing there shall be
no vertical drop greater than 1.5 m 5 feet except where suitable equipment
is provided to prevent segregation and where specifically authorized.
Sufficient placing capacity shall be provided so that concrete placement
can be kept plastic and free of horizontal cold joints while concrete is
being placed. Prior to placement, the Contractor shall submit the method
and equipment proposed for vertical construction joints cleanup and waste
disposal.
3.2.1
Time Interval Between Mixing and Placing
Concrete shall be placed within 30 minutes after mixing or agitating
ceases. When concrete is truck mixed or when a truck mixer or agitator is
used for transporting concrete mixed by a concrete plant mixer, the
concrete shall be delivered to the site of the work, and discharge shall be
completed within 45 minutes after introduction of the cement to the
aggregates.
SECTION 03373
Page 21
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