Mechanical characteristics of organically modified fly ash-kaolinite mixtures
"Fly ash is a hazardous waste material to the environment. Beneficial reuse of fly ash, however, brings economic and environmental benefits, i.e., decreases the cost of disposal, reduces greenhouse gas emission, and improves mechanical properties of construction materials. Due to the lack of pozzolanic properties, the reuse rate of Class F fly ash in geotechnical engineering is relatively low (ACAA 2013). In order to promote the effectiveness and sustainability of high volume reuse of class F fly ash in geotechnical engineering, biopolymers (Chitosan, and Xanthan gum) and synthetic polymers (Polyethylene Oxide, PEO) were used instead of the traditional stabilizers to improve the engineering behaviors of fly ash-kaolinite mixtures. The effects of polymers on microstructure development and geotechnical properties (i.e., stiffness, stiffness anisotropy and strength) of fly ash-kaolinite mixtures were measured in the laboratory. Shear wave velocity (Vs) and Vs anisotropy of organically modified fly ash-kaolinite mixtures were investigated by a self-developed floating wall-type consolidometer bender element testing system. Vs results showed that PEO and chitosan increased Vs of the fly ash-kaolinite mixtures, while xanthan gum decreased Vs. Vs anisotropy of the fly ash-kaolinite mixtures was decreased by the addition of polymers. Critical-state friction angles of fly ash-kaolinite mixtures increased with the addition of PEO and chitosan, while decreased with xanthan gum. Polymer bridging and columbic interactions, and the subsequent changes in size and fabric of kaolinite are the major influencing mechanisms. Physicochemical effects and the fly ash ratio also contributed to the observed changes"--Abstract, page iii.
Anisotropy, Biopolymer, Fly ash, Kaolinite, Stiffness, Strength, Civil Engineering, Geotechnical Engineering, Polymer Chemistry
Missouri University of Science and Technology
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