Page 396 - Moving the Earth_ The Workbook of Excavation

ROADWAYS

8.58 THE WORK

FIGURE 8.43 Mechanical cement spreader. (Courtesy
of Portland Cement Association.)

FIGURE 8.44 Single-shaft mixer. (Courtesy of Portland
Cement Association.)

This machine might accomplish the whole mixing operation in one pass, but two or more are
usually made to be sure.
Multiple-axle machines have either two or three axles, each equipped with tines. The first set
pulverizes and mixes; water is then added by a spray bar supplied by a tank truck; the second and
possibly the third set complete the job. These machines are often called single-pass.
If the rear plate of a mixer hood is lifted, the material is ejected a considerable distance to the
rear. On a sunny day this, as a preliminary operation, will produce quick drying of too-wet soil.
If the soil is trucked in, it is dumped, then bladed by a grader or shaped by a towed proportioner
into a symmetric windrow for the width being worked, with cement usually added on the top. Another
type of mixer picks up the windrow and passes it through a revolving drum. The first few paddles
blend the dry material, then water is sprayed in and mixing completed by the remaining paddles.
The material is discharged to the rear, and spread by an attached strike-off blade, by a follow-
ing grader, or by both.
The width that can be processed in one pass is limited by the width of the in-place mixer, or the
capacity of the windrow machine. This is usually around 10 feet, or one-half the width of a two-
lane road.