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.
Figure 1. Typical charging order for truck mixed PCC (redrawn from ACPA, 1995).
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.