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Performance Assessment of Lime and Fly Ash Chemically Treated Subgrade

Subgrade sample under magnification

Subgrade sample under magnification

Subgrade aggregate sample

Subgrade aggregate sample

Subgrade testing

Subgrade testing

Subgrade testing

Subgrade testing


Principal investigators:

Project status


Start date: 09/25/07
End date: 12/31/12


Report: Performance Assessment of Lime and Fly Ash Chemically Treated Subgrade (14.90 mb pdf) December 2012


Sponsor(s): Second Strategic Highway Research Program (SHRP 2)

About the research


This project was part of the SHRP 2 R02 project, Geotechnical Solutions for Soil Improvement, Rapid Embankment Construction, and Stabilization of the Pavement Working Platform.

Chemical treatment and stabilization of subgrades is a long-standing method to construct working platforms and improve the support conditions for pavement systems. Lime, cement, and fly ash are common chemical stabilization agents and are often incorporated with subgrade materials to improve volumetric stability, freeze-thaw performance, and/or subgrade stiffness.

Although laboratory test methods and design procedures are relatively well established, the long-term (5+ years) field performance characteristics of treated or stabilized subgrades is poorly documented and was the focus of this study. The main objectives of this project were as follows:

Nine test sections were selected to assess engineering properties of old stabilized subgrades in Texas, Oklahoma, and Kansas. The selection of the test sites was based on the type of subgrade, availability of old construction records, and age. Subgrades at six of these sites were stabilized with lime and the other three with fly ash. Eight of these test sites were more than 10 years old, and one test site was about 5 years old. Eight sites consisted of flexible pavement supported on base and stabilized subgrade or just stabilized subgrade, and one site consisted of concrete pavement supported on cement treated base and stabilized subgrade

Results from this study provide new information that should be of great interest to pavement designers dealing with selection of design parameters for chemically stabilized subgrade layers.