Soil Stabilization & Soil Modification

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For Pavement Condition

(PCI of 55 or less)

Soil Modification is sometimes referred to as "mud drying" however, soil modification is much more than that. Often, subgrade soils have high moisture content, giving them poor workability and lacking sufficient strength to support construction equipment. Chemical additives such as lime, fly ash, and cement can be added to these soils to dry and improve the soil’s workability.

Soil modification refers to the process of adding and mixing the above chemical agents into the soil to dry it, improve its workability, reduce the plasticity index (PI), and shrink swell potential. These improvements often result in slight strength gains for the soil.

There are two types of Soil Stabilization, chemical and bituminous. Chemical stabilization is the process of adding and mixing additional amounts of the same chemical agents used in soil modification into the soil to allow a significant increase in the strength of the soil. This improves the load-bearing capacity and physical properties of a subgrade to support pavements and foundations.

The soil property results from soil stabilization and modification treatments are the same. Bituminous soil stabilization results in an improvement in soil strength but is not generally recommended for clay soils; therefore, it is not used to modify soils. Many agencies require a specified increase in unconfined compressive strength before a soil can be considered a stabilized layer.

  1. 20 to 40% cost savings compared to removal and replacement
  2. Reduction in trucking of material.
  3. 100% reuse of subgrade materials for In- place projects
  4. Same-day return to light traffic for some processes
  5. Up to 25 years of life extension. The limiting factor for the service life of soil-modified or stabilized pavements is typically the service life of the surface course and not the modified/stabilized mixture itself
  6. Structural Layer (a) Coefficients of soil stabilized layers depend on the stabilizing agent used and vary from 0.08-0.15.

Issues Addressed

Soil Modification/Stabilization:

  • Existing pavement failures due to weak or unstable subgrades
  • Weak or unstable subgrades for new construction
  • Unsuitable subgrades due to high shrink/swell potential
  • Unsuitable subgrades due to excessive moisture


Soil Modification

  • Reduction in plasticity and shrink/swell potential
  • Reduce costs of undercuts, elimination of excavation, and replacement of material
  • Provides access on and within project sites during all weather conditions (such as parking lots or building pads)
  • Utilize onsite materials

Soil Stabilization (in addition to the above Attribites)

  • Increases the structural integrity of the subgrade materials
  • Can reduce the required thickness of the pavement section
  • When performed on existing pavements, soil stabilization has many of the same attributes as base stabilization and FDR

Common Combinations

Soil Modification/Stabilization + FDR

Soil Modification/Stabilization + CCPR

Soil Modification/Stabilization + CIR

Soil Modification/Stabilization + any pavement section