Page 395 - Moving the Earth_ The Workbook of Excavation

ROADWAYS

ROADWAYS 8.57

FIGURE 8.41 Distributing bags of cement. (Courtesy of Portland Cement Association.)

FIGURE 8.42 Preliminary mixing of cement. (Courtesy
of Portland Cement Association.)

The spreader should be towed rather than pushed to avoid picking up of cement by the truck
tires. It should be kept at least half full, to avoid changes in rate of flow.
The rate of cement delivery is rather critical. There must be enough to keep the mixer working,
but cement is vulnerable to loss by wind and spoilage by rain, so to spread it far in advance is risky.
Mixing. Two types of in-place mixers are used, single-shaft and multiple-shaft. A single-shaft
machine is shown in Fig. 8.44. As the machine moves forward, rapidly revolving tines strike
downward at the cement and earth, pulverizing and mixing with repeated blows as the mixture is
carried around inside a covering hood. Water may be added by a spray bar in the hood, or it may
have been applied to the soil ahead of the mixer.