GRADING AND EXCAVATING
Grading and excavating are cutting the high spots
to grade and filling in the low spots. In cutting down
the high spots, enough suitable fill material may be
removed to fill in low spots. However, it may be
necessary to develop other sources of fill material. If
the site is on hard and rocky terrain, loosen and break
the soil with a dozer ripper. Before fill material can be
placed in low spots, a suitable foundation must be
prepared. Material of a low-bearing capacity may have
to be dug up before the fill is placed.
Base Course
The base course distributes wheel load stresses
from the surface pavement to the subgrade. Since
stresses in the base course are more concentrated than
in the subgrade, the base course
Placement and Compaction
When placing and spreading
on a prepared subgrade, start at
must be stronger.
base course materials
the point nearest the
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source or at the point farthest from the source. Then
place the material progressively away from or toward
the source, respectively. The advantage of working
from the point nearest the source is that hauling
equipment can be routed over the spread material,
which helps compact the base course and avoids
cutting up the subgrade. An advantage of working
from the point farthest from the source is that the
hauling equipment further compacts the subgrade,
reveals any weak spots in the subgrade, and interferes
less with the movement of spreading and compaction
equipment.
Base course compaction must produce a
uniformly dense layer, conforming in every way to
specification requirements. The thickness of the lifts
should NOT exceed that which can be compacted to
the required density. The thickness of the lifts is
determined by the size of the compaction equipment,
such as 6 inches for rollers and 3 inches or less when
using tampers.
NOTE: Optimum moisture content must be
maintained during compaction.
