By: Monica Acosta
What is Soil Stabilization?
Types of Stabilizers
What is Soil Stabilization?
Improving the engineering properties of soils
used for pavement base courses, subbase
courses, and subgrades by the use of
additives which are mixed into the soil to
effect the desired improvement.
Although this process of improving the
engineering properties of soils has been
practiced for centuries, soil stabilization did
not gain significant acceptance for highway
construction in the United States until after
World War II.
Lime Cement-Fly Ash (LCF)
Lime-Fly Ash (LF)
According to The National Lime Association.
Lime can be used to treat soils in order to
improve their workability and load-
bearing characteristics in a number of
situations. Quicklime is frequently used to
dry wet soils at construction sites and
elsewhere, reducing downtime and
providing an improved working surface.
An even more significant use of lime is in
the modification and stabilization of soil
beneath road and similar construction
projects. Use of lime can substantially
increase the stability, impermeability, and
load-bearing capacity of the subgrade.
According The National Lime Association:
In the short-term, considering the structural contribution of lime-
stabilized layers in pavement design can create more cost-
effective design alternatives. A recent interstate project in
Pennsylvania, for example, began with a $29.3 million traditional
design approach. An alternate design using lime stabilization,
consistent with AASHTO mechanistic-empirical designs, cost
only $21.6 million—more than 25 percent savings. The savings
treating the existing subgrade material with lime, rather than
removing the material and replacing it with granular material; and
thinner layers of flexible pavement for the lime stabilized alternate
due to the increased strength of the lime stabilized subbase.
In the longer term, lime stabilization provides performance
benefits that reduce maintenance costs.
A cement-modified soil (CMS) is
a soil material that has been
treated with a relatively small
proportion of Portland cement.
The objective of the treatment is
to amend undesirable properties
of problem soils or substandard
materials so that they are
suitable for use in construction.
Preparing soil using Portland Cement for the new 380
Airbus at Chicago airport
Types of Cement-Modified Soils
Cement-modified silt-clay soils are soils that contain
more than 35% silt and clay (defined as material
passing a No. 200 (75 µm) sieve in accordance with
ASTM D4318). The general objective is to improve soils
that are otherwise unsuitable for use in subgrades or
subbase layers. Specific objectives may be to decrease
plasticity and volume change characteristics, to
increase the bearing strength, or to provide a stable
working platform on which pavement layers may be
Cement-Modified Soils Cont.
Cement-modified granular soils are soils
that contain less than 35% silt and clay
(defined as material passing a No. 200 (75
µm) sieve in accordance with ASTM
D4318). The usual objective is to alter
substandard materials so that they will
meet requirements specified for pavement
base or subbase layers.
Results of Using Portland Cement:
Reduction in plasticity characteristics as
measured by Plasticity Index (PI)
Reduction in the amount of silt and clay
Increase in the California Bearing Ratio
Increase in shearing strength
Decrease in volume-change properties
In-place mixing of lime with existing base
and paving material on city street.
Civil and Environmental Engineering Professor Craig Benson
and graduate student Burak Tanyu install a lysimeter to test
the effect of fly ash on ground water. (Photo: Courtesy College
Pull-type spreader stabilizing a base for a
STABILIZE TODAY, PAVE TOMORROW
The benefits of using chemical or bitumen additives are to:
improve the soils' strength
durability and gradation
reduce pavement thickness
for dust control during construction and
for soil waterproofing to preserve the soils' natural strength
by retarding ingress of surface water.
Have a Merry Christmas and a
Happy New Year!