Surface to Subgrade Stabilization

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Surface to SubgradeStabilization
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Soil Stabilization Guide

• What is it?
• Who will use it?
• Where do I get it?

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What It Is

• Overview of various physical and chemical methods
  for soil and base stabilization.
• It includes methods currently in use in MT and
  those that could be used in the future.
• It also contains decision trees, as a starting
  point in selecting a method.

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Who Will Use It

• Designers
• Construction personnel
• Maintenance personnel

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Where to find it

• For those who have high speed internet access,
  the guide can be quickly accessed on the MDT
  INTRANET site.
• The guide is also available on CD.

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Overview

• Lime treatment
• Cement treated base / soil
• Fly ash treated base / soil
• Foamed asphalt

• Sulfate bearing soils

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Lime Treatment

• MDT currently doesnt have a pay item or spec.
• Guide contains links to example specs.

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Types

• Quicklime
• Hydrated lime
• Slurry

Lime Treatment
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Applications

• Short term (modification)

• Drying
• Strength
• Workability

Lime Treatment
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Applications

• Long term (stabilization)

• Durability
• Structural
• Permeability

Lime Treatment
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Effect on Clay

• Lime changes the structure of clay

Lime Treatment
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Fly Ash Treated Base
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Types of Fly Ash

• Type C self cementing
• Type F pozzolanic, requires activation

Fly Ash Treatment
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Applications

• Base stabilization
• Soil strengthening
• Control of shrink / swell

Fly Ash Treatment
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The Colorado DOT approved the use of a lime/fly
ash blend for a project on US 287 near Longmont,
Colorado.
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Lime was mixed with soil and allowed to mellow.
Class F fly ash was then delivered in live bottom
trailers.
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A motor grader spreading the ash over the lime
soil mixture
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Roto-tilling with addition of water.
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A sheeps-foot roller compacting the mix,
resulting in a 9- inch layer of stabilized base.
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Foamed Asphalt Base
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Foamed Asphalt Base
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Foamed Asphalt Base
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Foamed Asphalt Base
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Foamed Asphalt Base
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Benefits of Foamed Asphalt Treated Base

• Fast curing
• Efficient

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Pilot Projects

• Louisiana
• Maine
• California

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• Findings - Louisiana
• Foamed RAP is an acceptable base material and
  should be considered for use as a standard base.
• Foamed asphalt is not a good candidate for a
  wearing surface and should be well drained.

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Findings - Maine

• Determined structural numbers for the foamed
  asphalt pavements.
• Determined gradation requirements.

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Findings - California

• Reduced adverse traffic impacts
• Hauling expense dramatically reduced.

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Montana Experience

• Lodgegrass South
• Wyola N S
• Wyoming Line North

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Foamed Asphalt Summary

• Extensive research has been performed.
• As always, careful planning and testing is a must.

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Sulfates
Soils containing sulfate salts can present
stabilization problems
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• Sulfate Induced Soil Heave

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Soil Sulfate Content
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End of Chemical Treatments