equipment, other than pumps, shall not be used for transporting lightweight
aggregate concrete.
3.7
CONVEYING CONCRETE ON SITE
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NOTE: Delete conveying equipment not wanted on the
project.
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Concrete shall be conveyed from mixer or transporting unit to forms as
rapidly as possible and within the time interval specified by methods which
will prevent segregation or loss of ingredients using following equipment.
Conveying equipment shall be cleaned before each placement.
3.7.1
Buckets
The interior hopper slope shall be not less than 58 degrees from the
horizontal, the minimum dimension of the clear gate opening shall be at
least 5 times the nominal maximum-size aggregate, and the area of the gate
opening shall not be less than 0.2 square meters 2 square feet. The
maximum dimension of the gate opening shall not be greater than twice the
minimum dimension. The bucket gates shall be essentially grout tight when
closed and may be manually, pneumatically, or hydraulically operated except
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.
3.7.2
Transfer Hoppers
Concrete may be charged into nonagitating hoppers for transfer to other
conveying devices. Transfer hoppers shall be capable of receiving concrete
directly from delivery vehicles and shall have conical-shaped discharge
features. The transfer hopper shall be equipped with a hydraulically
operated gate and with a means of external vibration to effect complete
discharge. Concrete shall not be held in nonagitating transfer hoppers
more than 30 minutes.
3.7.3
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 be used only for transporting
plant-mixed concrete over a smooth road and when the hauling time is less
than 15 minutes. Bodies of nonagitating equipment shall be smooth,
watertight, metal containers specifically designed to transport concrete,
shaped with rounded corners to minimize segregation, and equipped with
gates that will permit positive control of the discharge of the concrete.
3.7.4
Chutes
When concrete can be placed directly from a truck mixer, agitator, or
nonagitating equipment, the chutes normally 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.
SECTION 03300A
Page 40
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