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Unformatted text preview: pe, so constructed
that all materials
concrete are kept uniformly distributed
At the proportioning
plant, all solid
shall be water-tight
shall be accurately
weighed and charged into the drum; the
of water may either be charged iuto the drum or
measured and placed in the tank meant for carrying the mixing writer.
Trudr mixers shall be provided with some device whereby the time of
hauling, mixing, and introduction
of water could be readily checked.
‘4.7.4 Hand Mixing - Hand mixing slrould
Hand mixing, if authorized
work, shall be done on a water-tight
turned over using shovels as many times as may
homogeneous concrete of uniform consistency. be avoided in mass confor minor portions of the
The entire mass shall be
be necessary to produce 4.7.5 Retemperiq - The retempcring
of partially hardened
or mortar requiring renewed mixing, twith or without the addition of cement,
aggregate or water, shall not be permitted. 4.8 Handling and Conveying 4.8.1 The handling and convc,ying of concrete from the mixer to the
place of final deposit shall be dorlc> as rapidly as practicable
or 14~5 of ingredients.
Whenever the length
of haul from the mixing plant to the place of deposit is such that the concrete unduly compacts or segregates, suitable agitators shall be installed
in the conveying system.
Where concrete is being conveyed on chutes
or on belts, the free fall or drop shall be limited to 5 ft ( or 150 cm ) unless
The concrete shall be placed in position
30 minutes of its removal from tlic mixer
14 is : 457 - 1957
4.8.2 Handliwg Equibmeut 220.127.116.11 Buckets - 13uckets if used, shall be of the bottom-dump
type, permitting an even, controlled flow into the forms or hopper without
undue splashing or segregation. Cars, trucks and skips shall be designed
to facilitate uniform delivery rather than quick dumping. 18.104.22.168 Chutes - Where concrete is conveyed in chutes, the trough
of the chutes shall be of such size and shape as to ensure a steady, uniform
flow of material. The sections shall be made of, .or lined with metal and
al! runs shall have approximately.the same slope, not flatter than 1 vertical
to 2) horizontal. The layout shall be such that the concrete will slide
evenly in a compact mass without any’separation or loss of ingredients.
The required consistency of the concrete.shall not be changed in order to
facilitate chuting. Where it becomes necessary to change the consistency,
the concrete mix shall be completely re-designed. Wherever there is a
free fall within the conveying system, suitable baffle plates, splash boards
or down spouts shall be provided to prevent segregation, splashing, or loss
of ingredients. Wherever it is necessary to hold the discharge end of a
chute more than 300 cm ( or 10 ft ) above the level of the fresh concrete,
a flexible down spout shall b...
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- Fall '13