Page 353 - Moving the Earth_ The Workbook of Excavation

ROADWAYS

ROADWAYS 8.15

Oversized stone may be bladed to the side, or picked out by hand. Small loose stone may also
be taken off, or it may be left to be pushed back into the gravel by the roller.
Oversize stones that remain in the gravel after spreading and smoothing may be pulled out by
a rake grader blade or a spike-tooth harrow.
Hand-picked stones may be thrown directly into trucks, or placed alongside the road for later
removal. Second handling is easier if they are piled rather than scattered along the edge.
Compaction. Each layer should be thoroughly compacted by pneumatic tired or steel wheel
rollers, or by traffic. A heavy steel wheel roller will work back into the gravel all small stone
pulled out by spreading work, and it gives a well-finished appearance. See Fig. 8.9.
The edges should be rolled first, and strips should be overlapped. This preserves the crown of
the road, which should be at least 4 inches for a 20-foot road.
Proper compaction is impossible if the gravel is entirely dry, and difficult if it is too wet. However,
dry gravel can be watered, and wet gravel will usually drain quite quickly. Full compaction on a
gravel surface is not as important as in subgrades for pavements.

Dust Control. Drying out, with resultant dust nuisance and aggravation of washboarding, may
be prevented by use of calcium chloride. This is spread by hand shovels or machinery on the sur-
face, and absorbs air moisture that soaks into and dampens the surface.
1
Recommended application is 1 ⁄ 2 pounds per square yard at the beginning of the dust season,
1
and ⁄ 2 pound a month or two later. However, satisfactory results may be obtained with much
lighter applications where summers are not entirely dry.

FIGURE 8.9 Subgrade compaction.