Shear Wave Velocity and Its Anisotropy of Polymer Modified High-Volume Class-F Fly Ash-Kaolinite Mixtures

This study investigated the effects of polymers on the small-strain stiffness behavior of high volume Class-F fly ash-kaolinite mixtures. The shear wave velocity (Vs) and its anisotropy of organically modified fly ash-kaolinite mixtures were evaluated using a self-developed floating wall type consolidometer bender element (BE) testing system. Both synthetic polymers [polyethylene oxide (PEO)] and biopolymers (xanthan gum and chitosan) were used to modify the stiffness of fly ash-kaolinite mixtures. Shear waves generated and received by bender elements were measured to quantify the small-strain stiffness of the organically modified fly ash-kaolinite mixtures in three orthogonal directions, i.e.,vh, hv, and hh. The results suggested that (1)as the fly ash content increased, Vs increased, while the Vs anisotropy, in terms of shear wave velocity ratio Vs-hh/Vs-vh, decreased; (2)a threshold fly ash content concept, which corresponds to the onset of continuous contact chains between fly ash particles throughout the specimen, was used to distinguish the kaolinite-dominated zone from the fly ash-dominated zone of Vs and Vs anisotropy behavior; (3)the introduction of fly ash was also found to enhance the cross-anisotropy of fly ash-kaolinite mixtures; (4)the addition of PEO and chitosan increased the Vs of the fly ash-kaolinite mixtures, while the addition of xanthan gum decreased the Vs; and (5)all three polymers were found to decrease the Vs anisotropy of the fly ash-kaolinite mixtures.