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					Soil Stabilization

By: Monica Acosta
   What is Soil Stabilization?
   History
   Types of Stabilizers
   Lime
   Portland Cement
   Placement
   Conclusion
     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)
        Portland Cement
            Bitumen
              Lime
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
        came from:
            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.
Portland Cement
                                                          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
    size particles
   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
                          of Engineering)
                         Pull-type spreader stabilizing a base for a
                                        future mall.

Highway Reconstruction
    The benefits of using chemical or bitumen additives are to:
    improve the soils' strength
    workability
    durability and gradation
    reduce plasticity
    reduce pavement thickness
    for dust control during construction and
     for soil waterproofing to preserve the soils' natural strength
     by retarding ingress of surface water.
          Thank You!!
  Have a Merry Christmas and a
       Happy New Year!

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