storage level in each silo is being maintained above the 20 ton cut-off limit. The storage level indicating device may be either an audible or visual indicator. Multiple storage silos allows the plant operator a few different options for mix storage. All the silos could be filled with the same kind of
asphalt used to mixes.
concrete, or they may be store different kinds of AC It is when different mix
types are stored at the same wrong type of asphalt mix
time, the could be
sent to a Caltrans project. inattentive plant operator could
Multiple silos allow more than one type of asphalt concrete to be stored at the same time.
gates of the wrong silo, allowing AC to drop on the ground, onto a part
The Plant Inspector must ensure truck boxes are clean, do not have any material (AC) build up, and are free of any petroleum based release agents. Approved release agents should be used sparingly and visible pooling should be avoided. Visibly inspect AC mixtures being loaded into the trucks, watch for segregation of the mix caused by truck loading to one side, the plant operator opening and closing silo gates numerous times to top off the load, or loading the truck box with only one drop from the silo. Trucks may need to be tarped if the air temperature is cool and some distance is to be traveled from the plant to the paving site. Document all observations in your plant inspection diary.
Continuous Mix Process Controllers The asphalt plant controller, prior to being used for Caltrans projects, must be approved for use by Headquarters Construction.
Current CT 109 stickers must be affixed to the plant controller or scale indicator. The Plant Inspector must verify the span numbers shown on the CT 109 sticker as well as inspect any physical seals that are in place. If the CT 109 sticker is illegible or missing or if the security seals are broken, the District Weights and Measures Coordinator should be notified and the plant should not be used for asphalt concrete production.
The speed controls for individual aggregate feeders are maintained at the control panel. Once the bin percentages have been established, the aggregate rate (TPH) is increased or decreased using the master control. Controllers receive a wet TPH signal from the aggregate weigh bridge. Dry TPH are then calculated, using the moisture set point in the controller (the moisture set point may be changed at any time). The controller computes the amount of liquid asphalt from the target amount (usually a percentage) entered in the