PORTLAND CEMENT CONCRETE - Materials for Civil and Construction Engineers - page 257

FIGURE 7.4 Concrete ready mix plant.

mixer in order to avoid segregation. Furthermore, the concrete should be
discharged at the job site within 90 minutes from the start of mixing, even if
retarders are used (ASTM C94).

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7.2.2 Mobile Batcher Mixed Concrete

Concrete can be mixed in a mobile batcher mixer at the job site (Figure 7.5).
Aggregate, cement, water, and admixtures are fed continuously by volume,
and the concrete is usually pumped into the forms.

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7.2.3 Depositing Concrete

Several methods are available to deposit concrete at the jobsite. Concrete
should be deposited continuously as close as possible to its final position.
Advance planning and good workmanship are essential to reduce delay,
early stiffening and drying out, and segregation. Figures 7.6-7.9 show dif-
ferent methods used to deposit concrete at the jobsite.