soil stabilization by: monica acosta. overview what is soil stabilization? history types of...

Soil Stabilization

By: Monica Acosta

Overview 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.

History

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.

Types Lime Cement-Fly Ash (LCF)

Lime-Fly Ash (LF) Portland Cement

Bitumen Lime

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.

Example 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

constructed.

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

(CBR) Increase in shearing strength Decrease in volume-change properties

In-place mixing of lime with existing baseand 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)

Highway Reconstruction

Pull-type spreader stabilizing a base for a future mall.

STABILIZE TODAY,  PAVE TOMORROW                                                       

Conclusion 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.

Questions/Comments

Thank You!!

Have a Merry Christmas and a Happy New Year!