Figure 4-15. In-place mixing of lime with existing base
and paving material on city street.
Figure 4-17. Deep stabilization after lime spreading
the plow cuts 24 inches deep.
Figure 4-16. Off-site mixing pads for Mississippi River
levee repair project.
The material is mixed and compacted in one
Figure 4-18. Root plow for scarifying to a depth of 18 inches.
operation, and no mellowing period is required.
One increment of lime is added and the
mixture is allowed to mellow for a period of 1 to 7
days to assist in breaking down heavy clay soils.
(The term mellow refers to the reaction of the lime
on clay to make it more friable and easier to
One increment of lime is added for soil modifi-
cation and pulverization before treatment with
cement or asphalt.
One increment of lime is added to produce a
working table. Proof rolling is required instead of
pulverization and density requirements.
Two increments of lime are added for soils
that are extremely difficult to pulverize. Between
the applications of the first and second increments
Figure 4-19. Scarifying existing clay subgrade with lime on
city street project.
of lime, the mixture is allowed to mellow.
(c) Deep stabilization may be accomplished
added to the top 6 to 12 inches for complete
by one of two approaches.
stabilization. Plows and rippers are used to break
One increment of lime is applied to modify soil
down the large clay chunks in the deep treatment.
to a depth of 24 inches (fig 4-17 through fig 4-19).
Heavy disc harrows and blades are also used in
Greater depths are possible but to date have not
pulverization of these clay soils. In frost zones, the
been attempted. A second increment of lime is