X hits on this document

PDF document

State of California, Department of Transportation - page 42 / 52





42 / 52

computer. The controller increases or decreases pump speed, to regulate the quantity of liquid asphalt flowing through the meter. Constant minor adjustments of the asphalt pump speed are needed to keep the metered rate consistent with the binder set point vs. aggregate TPH rate.

The controller may change the liquid asphalt count sent from the meter, for example, a gallon count signal is converted by the controller to a TPH count. The calculation is based on the specific gravity or the pounds-per-gallon data keyed into the controller (plants equipped with mass flow meters do not need to do this type of conversion). The plant controller (computer) must be completely automatic in operation.

Liquid Anti-Strip Additive Systems Caltrans has recently required the addition of liquid anti-strips to asphalt binder on smaller paving projects. Liquid anti-strips act as adhesion promoters between the asphalt and aggregate, improving aggregate to asphalt bonds. At the present time liquid anti-strip is to be proportioned into the asphalt binder at the AC plant. Liquid ant-strip furnished

without a “Certificate of Compliance” shall not be used.

Only the brand and type of

anti-strip used for the AC mix design may be used during concrete. If the contractor elects to change brands or types of design must be performed. Liquid anti-strip is difficult to

production of the asphalt liquid anti-strip a new mix move with a conventional

pump use.













Batch plants use a small vessel to weigh the liquid anti-strip at the rate of 0.5 percent by weight of asphalt binder. For example, if 300 pounds of asphalt binder were used per batch, 1.5 pounds of liquid anti-strip would be needed for each batch. The anti-strip is introduces along with the flow of asphalt binder into the pugmill. This system must operate automatically with the AC batching control equipment.

Continuous mixing AC plants use a mass flow, Coriolis effect meter to proportion liquid anti-strips. For example, while the AC plant is in production 20 TPH of asphalt binder is

being used, 200 pounds per hour of the anti-strip would be

percent by weight of asphalt binder.

The system


required to maintain the 0.5 be interlocked to the plant

controller and adjust delivery rates automatically.

The AC Plant Inspector must take samples of the liquid anti-strip and the asphalt binder prior to the addition of liquid anti-strip.

Vehicle Scales All asphalt plants are required to have a vehicle scale located at the plant site. The only person allowed to weigh a commodity for sale by mass, is a certified Weighmaster or their assigned deputy. If weighing a combination of vehicles that will not rest on the scale platform at one time, the trailers shall be disconnected and weighed separately. The individual weights may be combined for the purpose of issuing a single certificate. The

Document info
Document views211
Page views211
Page last viewedTue Jan 24 01:14:12 UTC 2017