Characterisation of fly ash-based geopolymers activated with sodium silicate

Abstract

The present work examines the effects of sodium silicate activating solution on the properties of fly ash-based geopolymers. Various geopolymers were synthesized utilizing fly ash, sodium silicate solution and NaOH. Moduli (mass ratio between SiO2 and Na2O) of sodium silicate solution were 0.5, 1.0, 1.5 and 2.0, and the reaction was performed at slightly elevated temperature. XRD and SEM/EDS studies combined with compressive strength testing demonstrated that fly ash activated with higher sodium silicate modulus was mechanically superior and more amorphous while in the systems with lower sodium silicate modulus, new crystalline zeolite phase such as faujasite was formed.