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State of California, Department of Transportation - page 16 / 52

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Another area of importance is the screen deck. Are there excessive wear and/or holes allowing oversized rocks to be stockpiled with aggregates? Visual inspection of the stockpiles will indicate if oversized rocks have been passing through the screen deck. Stockpiles should also be examined for areas of aggregate segregation. Pockets of coarse aggregate can develop if the material is dry, or the aggregates fall a great distance from the stacker belt to the ground. For example, if material containing both coarse and fine particles is placed in a stockpile with sloping sides (cone shape), segregation is sure to occur as larger particles roll down the slope. Building a stockpile in layers can minimize this type of segregation.

If the inspector is uncertain of what is causing stockpiles to end up outside the grading specifications, an aggregate sample may be taken from the stacker belt. The grading results of this sample will help to isolate the problem area at the crusher or stockpile area.

Stockpiles A stockpile is one of the most likely locations to witness segregation of the aggregate

fractions. aggregate

At are

the crusher, stockpiles typically developed with

of a

stacker

belt.

If

room

allows,

a

loader

and/or

dump truck are used to haul aggregates the crusher to a long-term storage

from area.

When

a

stacker

belt

is

used

to

stockpile

aggregates that large and small

are well graded, or contain fractions, segregation of the

material is likely to occur. stockpile can be defined as,

Segregation of a larger aggregates

rolling down the face and bottom of the stockpile.

accumulating

at

the

Numerous taken to

preventative measures can be

reduce

segregation,

and

contamination

of aggregate

stockpiles.

Place stockpiles on a draining, stable surface.

clean, dry, free Asphalt concrete

pads may be used to create

a solid stable

surface.

Keep

stockpiles

of

different

aggregate necessary stockpiles

sizes separated by space, or if use a barrier to physically keep separated. When a staker belt is

used to stockpile well the outside edge will be

graded aggregates, coarse, and the area

below

and

slightly

behind

the

head

pulley

will

be

fine.

A

rock

ladder

(photo

at

left)

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