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An asphalt overlay was then placed over the stabilized base. Class F fly ash in itself is not self-cementing. It needs additional lime to undergo a cementitious reaction. It's important to note that fly ash, when used in combination with lime or lime kiln dust, performs two important functions in FDR work:

1. Fly ash provides the silica and alumina needed for cementitious reaction with lime to increase the strength, stiffness, and durability of the stabilized base layer
2. Fly ash acts as a mineral filler to fill the voids in the granular pulverized pavement mix, reducing the permeability of the FDR stabilized base layer. Lime or lime kiln dust by itself will not provide adequate stabilization for pavement materials deficient in silica and alumina. The addition of fly ash is necessary for cementitious reactions to occur.

Objective and goal
The overall objective of this work is to demonstrate the effective use of Class F fly ash in combination with lime or lime kiln dust in the FDR of asphalt pavements.

The goal of the proposed program is to establish field-verified relationships for the service performance, structural and environmental behavior of FDR pavements constructed using lime-activated fly ash.

The project goal is being pursued with four interrelated activities. In the first, laboratory studies specifically designed to investigate the physical, chemical, and engineering properties of fly ash FDR mixes were conducted. This allowed the research team to determine the optimal material mixes that were implemented in the two pavement preservation projects.

In the second activity, two highway pavements were constructed and instrumented in 2006, and will be monitored for two years. The purpose of this activity is to obtain robust field results on the structural, service and environmental performance of field constructed FDR bases.