Resilient Modulus of Clay Subgrades Stabilized with Lime, Class C Fly Ash, and Cement Kiln Dust for Pavement Design

The effects of different percentages of one traditional additive—hydrated lime—and two by-products—Class C fly ash (CFA) and cement kiln dust (CKD)—on the resilient modulus (M r ) of four different clay subgrades were investigated. It was found that at lower application rates (3% to 6%), the lime-stabilized soil specimens showed highest enhancement in the M r values. At higher application rates (10% to 15%), however, CKD treatment provided maximum improvements. Three log-log and one semi-log stress-based models were evaluated. Validation of selected models was conducted by using additional soil data. Overall, a semi-log deviatoric and confining stress model was found to show the best acceptable performance. Additional analyses were performed to develop correlations of M r with compacted specimen characteristics and soil and additive properties. To illustrate the application of the semi-log model, the AASHTO flexible pavement design methodology was used to design asphalt concrete pavement sections.