Truck mixed PCC is usually proportioned by batching the separate ingredients directly into the concrete mixing truck. The ingredients are usually charged in a certain order to ensure good mixing of all ingredients. Although the specific order depends upon local practice, mixing plant procedures and possibly job specifications, a typical charging order is shown in Figure 1.
Truck mixed PCC (Figure 2) is appropriate for all types of pavement construction, but is particularly well-suited for instances that can take advantage of a concrete mixing truck’s monitored, continuously agitated storage volume (the mixing drum) and its ability to precisely deliver PCC through its chute (see Figure 3). These situations might include: intersection paving, street paving, pavement repair, urban environments, high traffic areas and staged/phased construction. Disadvantages of truck mixed PCC are longer load and unload times (due to the nature and opening size of the mixing drum) and the higher operating cost of a concrete mixing truck when compared to an end or bottom dump truck. Truck mixer specifics are covered in PCC Mix Transport.