RESILIENT AND PLASTIC BEHAVIOR OF CLASSIFIER TAILINGS AND FLY ASH MIXTURES

The resilient modulus and plastic deformation of two materials, currently considered waste products, were studied. The first material is fly ash, which is a waste product of coal combustion. The second is classifier tailings, a fine-grained material that is a by-product of aggregate processing. Results from cyclic triaxial testing used to study the resilient and plastic response of fly ash, classifier tailings, and a mixture of the two materials are presented. By itself neither material exhibits sufficient stiffness to realize any advantage in pavement construction. However, the resilient modulus of a mixture of the two materials is higher and plastic deformation lower than that of either material considered alone. Since no previously published experience with this material mixture exists, it is considered a new type of geomaterial. Historically, because of difficulties associated with cyclic triaxial testing, empirical formulas have been used to estimate resilient modulus. Therefore, the usefulness of applying existing empirical relations to the materials investigated to estimate resilient modulus is explored. Mechanistic-based pavement analyses were performed to predict pavement lives for flexible pavements having a subgrade of fly ash, classifier tailings, or a mixture of the two. The benefits of the material mixture in improving the pavement performance over that of either of its constituents are demonstrated.