Field Verification of Stabilized Soil Strength

In marginal soils, it is common to use chemical stabilizers to improve the strength properties of those soils for roadway construction. Many departments of transportation have a standard or design guide that is used to determine the stabilizer type (i.e. Lime, Fly Ash, Cement Kiln Dust, etc.) and the amount of stabilizer to use based on soil classification. These design guides do not always provide an ideal stabilization design since only a few index soil properties like Atterberg Limits and grain size distribution are used for soil classification. The testing in this study involves five roadway construction sites where the use of Class C Fly Ash (CFA) as a stabilizer and quicklime as a modifier to reduce Plasticity Index (PI) and increase workability was performed. The roadway sites were tested with the Dynamic Cone Penetrometer (DCP) and unconfined compression strength (UCS) specimens were prepared to match the cure times of the field testing. The results of this research show that the DCP can be effectively utilized to verify strength gains of stabilized roadway subgrades and that the change in Average Dynamic Cone Index (DCI) could possibly be correlated to strength increase results from laboratory UCS testing.