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State of California, Department of Transportation - page 26 / 52

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Zero tolerance (scales returning to zero after dumping batch) for aggregate scales shall be 0.5 percent (1/2 %) of the total batch weight of the aggregate. Over-under tolerances (amount above or below the pre-selected weight for each bin) for individual weights of each aggregate bin shall not be more than one percent (1 %) of the total batch weight of aggregate.

Asphalt Binder Storage Tanks

Asphalt binder is typically stored in heated and insulated tanks. The tanks are calibrated at 100 gallon intervals (charts for converting inches of asphalt to gallons of asphalt are available from plant operator) and are to be accessible at any time for measuring (stabbing the tanks) the

volume of asphalt.

Safety is of the

utmost

importance

when

sampling

asphalt

binder

or stabbing the

asphalt

storage tanks.

The

temperature

of

conventional

liquid

asphalt

may be binders

as high as 375 F; modified asphalt (rubberized) may be heated to

temperatures of 400 F. Contact with material at these elevated temperatures

any will

cause

severe

burns,

always

wear

long

This tank stores the horizontal attitude, and widely used for liquid

asphalt binder in a

at this time is the asphalt storage.

most An

insulating metal tank

layer is located between the and the thin outside covering.

heavy

pants, boots, long sleeve shirts, heat resistant gloves, safety glasses and hardhat when working around hot piping and hot asphalt binder. A ½” to ¾” diameter asphalt sampling valve, located in the feed line to the plant, is used by the asphalt plant inspector to obtain a one-quart sample of asphalt binder. The valve opening is to be located 24 to 30 inches above the standing platform used to take the sample. Housekeeping in this area is very important, spilled asphalt should be cleaned up as soon as possible. Drainage receptacles are to be provided for flushing the valve before taking asphalt samples. The minimum amount of liquid asphalt to flush from the valve, prior to sampling, shall be no less than one gallon.

This tank stores the asphalt binder in a vertical attitude. The vertical tank is better for storing

polymer-modified because less air

type asphalts, primarily to asphalt contact and an

agitation

system that

keeps

suspended

in the asphalt

binder.

the

polymers

A temperature-sensing device, accurate to 10° F, must be installed in the asphalt feed line. A temperature-indicating device (LED, LCD, etc.) shall be located in the

control

room.

When

supplying

asphalt

concrete to a Caltrans automatic continuous

QC/QA project, an recording device

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